6mm ARC - Practical Reloading

[Laurie]

Is there a testing lab that has data showing the (actual) produced pressure of Powder A @ X number of grains ,and the (actual) produced velocity for test projectile

Yes, there are many such as that for the Hodgdon group powders (Ramshot, Accurate, IMR, Hodgdon, Winchester. Go to the Hodgdon Reloading Data Center website, select 6mm ARC as an example, whatever bullet(s) you fancy, likewise powders. Both starting and maximum loads consist of charge weight, MV, Pressure.

These are taken from tests in a barrel whose internal dimensions and the chamber cut in it are compliant with the SAAMI specifications for the cartridge using modern industry standard electronic pressure measuring equipment and methodology. That is why they often bear only a passing resemblance to actual results in factory rifles as the latter often have considerably 'looser' barrels and longer-throated chambers. (Some reloading manuals measure pressures in the SAAMI spec kit, but reshoot the loads in a factory rifle to provide more representative MVs.) Older cartridges often show pressures as C.U.P. (Copper Units of Pressure) not psi as pressures were measured in pre electronic crystal / strain-gauge kit in special pressure barrels with attached cylinders to take a copper cylinder, the amount it was compressed by the chamber pressure being used to calculate what that pressure was.

Many other sources quote the pressures so measured, usually for the maximum charge only, but not all do so.

Where the source puts all loads into columns by MV, eg 2,500 ........ 2,600 ............ 2,700 fps etc and doesn't quote pressure (Hornady and Sierra manuals), the companies have carried out pressure-barrel tests and graphed the centre-line through the data points, reading off what charges are predicted to produce the set MVs with the highest quoted charge set at the level below that which exceeds SAAMI MAP values. This used to be done manually on graph paper, but nowadays the lab technician feeds in the relevant data - cartridge, components used, powder grade and charge weights into a PC program and MVs are automatically transferred from the chronograph and the calculations run there, even building a printer-ready table for the next edition of the reloading manual in at least one bullet company's case as different powders are tested.

 

[David Milisock]

My question was definitely not phrased correctly .
I am aware of the load data provided in the assorted load books.The load books show a safe working pressure of 52,000 of pressure and develop xxx fps of velocity per xxx number of grains of powder for that projectile. I am aware of and understand why the difference between gas guns and bolt action . I also understand many factors relate to velocity of a projectile.

Is there a testing lab that has data showing the (actual) produced pressure of Powder A @ X number of grains ,and the (actual) produced velocity for test projectile

A comparison chart with equal test parameters that shows Powder A @ 25 gns.produced 50 thousand psi of pressure @ 2500 ft per second velocity to projectile weighing 100 gn. with a impact force of. xxx ft lb at 100 yards

Powder B @25 gns produced 42,500 thousand psi. @ 2450 ft per second to the 100 gn. projectile. with impact force of xxx ft lb.
The load books, and charts are to me a generic listing of what is available.

Does such information exist, available to, we the people, or is it proprietary , and released on a need to know basis. This is just my in depth thoughts on the subject, ( am I trying to pick the fly crap out of the pepper) and need to be concerned with other factors more under my control.

Thank you.

I know of no such data table. The loading data provided does not even list peak pressures accurately. The data provider sets their own safety limit that can be proved in court not to exceed the SAAMI maximum. So it's up to the creator and publisher of the data, that’s why you can see such huge variations in max charge weights.

I worked with a fellow several years ago with his own piezo device and my understanding is that listed pressures are maximum average nominal pressures that reside between a set maximum and minimum peak pressure. The standards are stringently observed.

With all this said I believe this may be why very nearly all the early 6MM ARC data has disappeared from the web. Hornady in my opinion has reduced powder charges on some if not all the original loads. They may have been pushing the limits more than they liked. Notably the CFE load is nearly 1 grain lower in the gas gun. LeverEvolution was modified about 1/4 grain lower for gas guns however the new data has been published several times identically.

A few videos, podcasts and data charts have gone completely from the internet. A video where they discussed a Hornady employee first working on a very early 6mm AR for himself is still around but the more detailed video made later where they discussed Hornady development of the 6 ARC using Leverevolution to develop the first heavy weight load data is gone as are all the first loading data.

I believe they made the right choice, from my observations it appears that the 6 ARC especially in the heavyweight projectiles is powder sensitive in gas guns, it not only needs the right burn rate but a progress burnings power of the right burn rate.

 

[gunsandgunsmithing]

I believe they made the right choice, from my observations it appears that the 6 ARC especially in the heavyweight projectiles is powder sensitive in gas guns, it not only needs the right burn rate but a progress burnings power of the right burn rate.

Yes, and I believe that the appropriate gas system and port size can make a significant real world difference in bolt life. You may be able to tip the powder jug a tad more with the right combination and timing of the gas system. They have got to cover their back sides for most any scenario out there. Bolt lugs breaking isn't typically catostraphic but I suppose it could be or could become that way if the lugs break, say one by one until it becomes a catostraphic event.

 

[Gtscotty]

I know of no such data table. The loading data provided does not even list peak pressures accurately. The data provider sets their own safety limit that can be proved in court not to exceed the SAAMI maximum. So it's up to the creator and publisher of the data, that’s why you can see such huge variations in max charge weights.

I worked with a fellow several years ago with his own piezo device and my understanding is that listed pressures are maximum average nominal pressures that reside between a set maximum and minimum peak pressure. The standards are stringently observed.

With all this said I believe this may be why very nearly all the early 6MM ARC data has disappeared from the web. Hornady in my opinion has reduced powder charges on some if not all the original loads. They may have been pushing the limits more than they liked. Notably the CFE load is nearly 1 grain lower in the gas gun. LeverEvolution was modified about 1/4 grain lower for gas guns however the new data has been published several times identically.

A few videos, podcasts and data charts have gone completely from the internet. A video where they discussed a Hornady employee first working on a very early 6mm AR for himself is still around but the more detailed video made later where they discussed Hornady development of the 6 ARC using Leverevolution to develop the first heavy weight load data is gone as are all the first loading data.

I believe they made the right choice, from my observations it appears that the 6 ARC especially in the heavyweight projectiles is powder sensitive in gas guns, it not only needs the right burn rate but a progress burnings power of the right burn rate.

I don't believe the bolded portion is accurate. Hornady takes the updated load data sheets down from their website for all chamberings when the data makes it to the app and load manuals. I have the Hornady app, and the current load data looks to be almost exactly the same for the weights I looked at except for Varget and RL-15 where the new max charges were actually HIGHER than those originally published.

Can you cite an example where the currently Hornady data has been lowered from the originally published data sheets? Comparing the 108gr, 105gr and 95gr tables, I can't find a single example, and only two instances where loads were changed at all (the increases cited above). The CFE and LVR loads published for those weights by Hornady have not changed in the current data, from the initial publications I posted above. I don't think it's fair to imply that Hornady put out recklessly high pressure data that they subsequently had to dial back, it's just not true.

 

[Retired shooter]

OK gentlemen.
While I may be older, or maybe the same age as many of you, I an still rookie at reloading , especially this cartridge. I was looking for something slightly larger than the 223, more power, heavier bullet,better in the wind, equal to or slightly more recoil. I got talked into the 6ARC by a very reputable firearms co. He had already done the 224 valk. As most of you know my son started doing the ELR stuff with his 338 lapua. My desire is to find out the longest distance I can shoot consistently. With that being said I want to use the heavier bullets, of the available manufacturer. Therefore with my rookie status , I ask questions, ( unfortunately not always phrased correctly) No competition, no paper punching, hopefully milk jug challenging, and steel shooting.

Just an attempt to figure out where to start with what powder, and how much or whose.
Everyone has got there opinions and experience usually with data. As I said earlier a gent in a shop selling different types and makes of powder showed me a loading book end of last week with the 6ARC listed using an Alliant powder, that I had not previously seen in any load data. I have a few up to date books, however did order another from another co.

So after this long post, for longer distance, maybe even the proverbial mile shot or long distance milk jug killing, with the heavier bullets, where will be a good starting point for reloads, after I get the new upper I am waiting on.

Thank you RSGs ( Real Smart Guys )for putting up with an older rookie,.

 

[David Milisock]

I don't believe the bolded portion is accurate. Hornady takes the updated load data sheets down from their website for all chamberings when the data makes it to the app and load manuals. I have the Hornady app, and the current load data looks to be almost exactly the same for the weights I looked at except for Varget and RL-15 where the new max charges were actually HIGHER than those originally published.

Can you cite an example where the currently Hornady data has been lowered from the originally published data sheets? Comparing the 108gr, 105gr and 95gr tables, I can't find a single example, and only two instances where loads were changed at all (the increases cited above). The CFE and LVR loads published for those weights by Hornady have not changed in the current data, from the initial publications I posted above. I don't think it's fair to imply that Hornady put out recklessly high pressure data that they subsequently had to dial back, it's just not true.

Yes I will see if I can post a PDF here later the grandkids just showed up.

I added 2 PDF files the one is 108/110 grain Hornady data and 103/105 Hornady data. Note 2 things, Hornady lists powder burn rates from top fastest to bottom slowest. The CFE and LeverEvolution are reversed on the data charts.

Also the 108/110 grain loads show higher charge weights than the 103/105 grain charge weights. The 103/105 data appeared online after the 108/110 data, obviously Hornady reduced the charges for the 103/105 projectiles.

Then if you go to the Hodgen load generator site they listv6MM ARC loads lower than Hornady.

Reloading Data Center

www.hodgdonreloading.com

 

[Gtscotty]

Yes I will see if I can post a PDF here later the grandkids just showed up.

I added 2 PDF files the one is 108/110 grain Hornady data and 103/105 Hornady data. Note 2 things, Hornady lists powder burn rates from top fastest to bottom slowest. The CFE and LeverEvolution are reversed on the data charts.

Also the 108/110 grain loads show higher charge weights than the 103/105 grain charge weights. The 103/105 data appeared online after the 108/110 data, obviously Hornady reduced the charges for the 103/105 projectiles.

Then if you go to the Hodgen load generator site they listv6MM ARC loads lower than Hornady.

Reloading Data Center

www.hodgdonreloading.com

I don't see any new pdfs that you posted. The 105gr data was published at the same time as the 108/110gr data and has always been I tiny bit lower. That's not an adjustment over time, that's different load data for different bullets, it hasn't changed since it's been published, except 103gr ELDx was added to the bullet list, still the data didn't change.

The Hodgdon data has always been lower than the Hornady data, also not a change. Different publishers, different data, different maxes, you see that for all cartridges.

 

[David Milisock]

I don't see any new pdfs that you posted. The 105gr data was published at the same time as the 108/110gr data and has always been I tiny bit lower. That's not an adjustment over time, that's different load data for different bullets, it hasn't changed since it's been published, except 103gr ELDx was added to the bullet list, still the data didn't change.

The Hodgdon data has always been lower than the Hornady data, also not a change. Different publishers, different data, different maxes, you see that for all cartridges.

Yes the grandkids are trying to induce a heart attack.

 

[Gtscotty]

Yes the grandkids are trying to induce a heart attack.

Those are the same files I posted a few posts ago. That data has not changed or been reduced between those initial PDFs, and the current Hornady manual. The theory that Hornady realized their 108gr data was too hot (after they pressure tested it?) And therefore lowered the 105gr data doesn't make any sense because the supposedly problematic 108gr data has subsequently been published in their manual and in the app without being reduced in any way.

Hornady's published data is fine, not dangerous, and there's been no conspiracy to reduce it. It's interesting that Hodgdon's data is different, but across many cartridges those two publishers have significant differences, so not exactly surprising.

I will say for someone wanting to get started, work up your loads, but I've settled on 29.2gr LVR under 105gr MBs in my 21", and 108gr ELD and 100gr TGKs over 29.3gr LVR in my 18".... I'm seeing a bit of a pattern in the final destination of my load workups.

 

[Retired shooter]

Those are the same files I posted a few posts ago. That data has not changed or been reduced between those initial PDFs, and the current Hornady manual. The theory that Hornady realized their 108gr data was too hot (after they pressure tested it?) And therefore lowered the 105gr data doesn't make any sense because the supposedly problematic 108gr data has subsequently been published in their manual and in the app without being reduced in any way.

Hornady's published data is fine, not dangerous, and there's been no conspiracy to reduce it. It's interesting that Hodgdon's data is different, but across many cartridges those two publishers have significant differences, so not exactly surprising.

I will say for someone wanting to get started, work up your loads, but I've settled on 29.2gr LVR under 105gr MBs in my 21", and 108gr ELD and 100gr TGKs over 29.3gr LVR in my 18".... I'm seeing a bit of a pattern in the final destination of my load workups.

Yip grandkids are known for that even as they get older. One in Marine Corp, other off to college next year.
Always glad to hear they would be here, at times ready for them to leave, before they got here.!

 

[David Milisock]

Those are the same files I posted a few posts ago. That data has not changed or been reduced between those initial PDFs, and the current Hornady manual. The theory that Hornady realized their 108gr data was too hot (after they pressure tested it?) And therefore lowered the 105gr data doesn't make any sense because the supposedly problematic 108gr data has subsequently been published in their manual and in the app without being reduced in any way.

Hornady's published data is fine, not dangerous, and there's been no conspiracy to reduce it. It's interesting that Hodgdon's data is different, but across many cartridges those two publishers have significant differences, so not exactly surprising.

I will say for someone wanting to get started, work up your loads, but I've settled on 29.2gr LVR under 105gr MBs in my 21", and 108gr ELD and 100gr TGKs over 29.3gr LVR in my 18".... I'm seeing a bit of a pattern in the final destination of my load workups.

Ok take a look at the data and look at other manufacturers data. When have you ever seen anyone's data that when using the same powder with a maximum charge the bullet weight and powder charge weight both go up? Well Hornady data does!

I don’t think there's a conspiracy, Hornady published their 108/110 grain data at LeverEvolution max at 29.7 grains. Then a little while later they published data for multiple bullet weights and the 103/105 grain data was 29.5 grains. The 108/110 data has remained the same on that single sheet but the 103/105 dropped .2 grain under the 108/110 load and that's suspect to me.

If they had not reduced the 103/105 grain load the powder charge would be higher then the 108/110 charge. Anytime with a max charge when using the same powder as the weight of bullet goes down the powder charge goes up. It's clear to me Hornady reduced pressure in the 103/105 loads.

I believe that Hodgen has their charges listed a bit lower as a protection against lawsuits, they do publish the pressures of their pressure barrels and it's close to max for max loads.

I have to dig around I have some earlier data I printed from the web that is no longer available. I do believe the Hornady 108/110 data to be MAX for gas guns and may be cause to make sure that you're careful approaching max. There is a bit more head room for the 103/105 grain bulletts but not much.

 

[Gtscotty]

Ok take a look at the data and look at other manufacturers data. When have you ever seen anyone's data that when using the same powder with a maximum charge the bullet weight and powder charge weight both go up? Well Hornady data does!

I don’t think there's a conspiracy, Hornady published their 108/110 grain data at LeverEvolution max at 29.7 grains. Then a little while later they published data for multiple bullet weights and the 103/105 grain data was 29.5 grains. The 108/110 data has remained the same on that single sheet but the 103/105 dropped .2 grain under the 108/110 load and that's suspect to me.

If they had not reduced the 103/105 grain load the powder charge would be higher then the 108/110 charge. Anytime with a max charge when using the same powder as the weight of bullet goes down the powder charge goes up. It's clear to me Hornady reduced pressure in the 103/105 loads.

I believe that Hodgen has their charges listed a bit lower as a protection against lawsuits, they do publish the pressures of their pressure barrels and it's close to max for max loads.

I have to dig around I have some earlier data I printed from the web that is no longer available. I do believe the Hornady 108/110 data to be MAX for gas guns and may be cause to make sure that you're careful approaching max. There is a bit more head room for the 103/105 grain bulletts but not much.

You're reading too much into the difference between the 108gr and 105gr data, and seeing something that isn't there. Different bullets have different shank lengths, different pressure profiles and max loads. Usually heavier bullets have lower max charges of a given powder than lighter but there are many, many exceptions due to bullet construction. Originally the 103gr-105gr load table only showed the 105gr hpbt, which by the way has to be seated pretty deep in the case to stay out of the lands, it's not at all surprising to me that the max loads are lower than the much more recent 108gr and 110gr vld type designs.

As an example here's the result of a 30 second search for similar situations in the Hornady app.

Max loads for RL-15 in .308:
41.4gr - 190gr IL
42.3gr - 195gr hpbt, ELDm
42.3gr - 200gr ELDx
43.2gr - 208gr hpbt, A-max, ELDx
43.6gr - 212gr ELDx

The 212gr max load is higher than the max loads for 208gr, 200gr, 195gr and 190gr. Did Hornady come up with the 212gr load first, then dial back the pressure for the other 4, or do different bullets have different max charges with factors beyond "heavier bullet = lower charge"?

Again, you're reading a chain of events into this load data that there's no real evidence for, the load disparity you're basing it all on isn't a very rare occurrence across various cartridges and bullets.

 

[Beiruty]

Wanted to learn about what others are trying and share my experience so far:


Build:

• 20” 1:7 twist 416 SS DMR Profile Ballistic Advantage barrel
• Vltor upper and lower
• Ballistic Advantage bolt in PSA premium bolt carrier
• Adjustable gas block
• TBAC Ultra-9 suppressor
• Geissele SSA-E trigger

Goal:
It would be fun to have a relatively light weight AR-15 platformed rifle that can consistently shoot at or under .5 MOA from 100 to 1000 yards.

Testing:
From prone using Joy-Pod bipod, Bigfoot rear bag and NF 5.5-22X50 optic. All rounds loaded to 2.26 COAL.

First steps:
Using the lathe, I modified some 6.5 Grendel dies by shaving off .040 from the base and replacing the neck sizing bushing. I set the dies up in a Forster Coax press and using annealed 6.5 Grendel brass, sized the necks down and pushed the shoulders back to the SAAMI specs. I also used a Sinclair carbide expander mandrel before loading.

First firing:
I was lazy, and using known data from the 6mm AR, I loaded 27.5 grains of H4895 under a 105 Berger Hybrid Target. This was way over pressure yielding speeds in the 2730 FPS range, heavy ejector swipes and unusably expanded primer pockets. Groups were all in the 1 to 1.5 MOA range at 100 yards. SDs were in the low single digits, however! Bad test - bad approach and dangerous. I know better and am lucky to re-learn that lesson without the pain that often accompanies such learnings.

Second firing:
Testing from 26.0 grains of H4895 up to 26.5 grains showed better results. The best results were the 26.5 grain charges with speeds of 2594 but SDs in the 17 FPS range. 100 yard groups were in the mid .5 MOA range. The groups got worse as the the powder charge decreased. No pressure signs, swipes or ejector marks at this charge range. It is, however, over pressure according to Quickload.

Changing gears:
I received some Hornady 105 grain Black factory ammunition that shot poorly in my barrel. Speed was good at 2640 FPS and SDs were a reasonable 11.4 FPS. Group sizes at 100 yards were terrible at 1.9 MOA.

I also tried some VARGET under the Hornady 108 ELD-M. 27 grains yielded 2554 FPS with a 5.5 SD and very repeatable .5 - .52 MOA at 100. I took these out to 700 and 900 yards on a windless day with the same .4 to .5 MOA results. The lack of wind is unusual but was welcomed. There were no pressure signs at this charge weight, however, Quickload estimates that this is 3900 PSI over SAAMI pressure.

Learning so far:
Fired by not resized converted 6.5 Grendel brass holds 34.74 grains of water and fired but not resized factory 6mm ARC cases holds 34.58 grains of water. In Quickload I edited a 6 PPC case for case length and case capacity and now get estimated MV within 2-4 FPS of what I have measured using the Labradar.

Disclaimer:
All of the above hand loads are above 52000 PSI, and, as such, I am obligated to warn everyone from trying them. If you do so, you are doing it at your own risk.

Next Steps:
It looks like the 27 grain VARGET and 108 ELD-M combo is very close to a predicted OBT node. .2 to .3 more grains is what I am going to test next.

Additionally, I don’t want to give up on H4895. I want to test this powder with both the 108 ELD-M and the 105 Hybrid Target.

• Will try 26.6 H4895 with 108 ELD-M expecting 2608 FPS out of my barrel.
• Will also try 26.5 H4895 with 105 Hybrid Target expecting 2635 FPS out of my barrel.

Both of the above correspond to OBT nodes using Quickload.

Request:
There is already a big thread in progress discussing the merits of this cartridge which is interesting but not the intent of this one. Would like to keep this thread focused on practical experience and suggestions to optimize safe hand loads for this cartridge in semi-auto gas rifles.

Hope this helps someone,

Henryrifle

Since you have an adjustable gas block, if you can close fully. Develop your load while the gas block is closed, check for high pressure. After all is done, you can open the gas block, so the AR would cycle with developed correctly.
How far is the gas block hole from the muzzle end?
I can develop a sim in GRTools and calibrate to your observed MV.

 

[David Milisock]

You're reading too much into the difference between the 108gr and 105gr data, and seeing something that isn't there. Different bullets have different shank lengths, different pressure profiles and max loads. Usually heavier bullets have lower max charges of a given powder than lighter but there are many, many exceptions due to bullet construction. Originally the 103gr-105gr load table only showed the 105gr hpbt, which by the way has to be seated pretty deep in the case to stay out of the lands, it's not at all surprising to me that the max loads are lower than the much more recent 108gr and 110gr vld type designs.

As an example here's the result of a 30 second search for similar situations in the Hornady app.

Max loads for RL-15 in .308:
41.4gr - 190gr IL
42.3gr - 195gr hpbt, ELDm
42.3gr - 200gr ELDx
43.2gr - 208gr hpbt, A-max, ELDx
43.6gr - 212gr ELDx

The 212gr max load is higher than the max loads for 208gr, 200gr, 195gr and 190gr. Did Hornady come up with the 212gr load first, then dial back the pressure for the other 4, or do different bullets have different max charges with factors beyond "heavier bullet = lower charge"?

Again, you're reading a chain of events into this load data that there's no real evidence for, the load disparity you're basing it all on isn't a very rare occurrence across various cartridges and bullets.

We will have to agree to disagree on this and here's my argument. I'll stick the reference to CFE #111 on the burn rate chart and LeverEvolution #113, both listed as good performing powders by Hornady from weights from 75 grain to 110 grain.

I'll list CFE first always.
75 grain
31.6
33.6
80 grain
30.9
31.8
87 grain
30.9
31.6
90 grain
29.4
31.1
105 grain
28.6
29.5
110 grain
29.1
29.7

Do we see the pattern? While the bulletts represent, varmint, monolithic, interlock, ELD expanding, ELD match, as well as hollowpoint match they all are listed as having reasonable or good performance with these two powders.

ALWAYS with these two powders until the 110 grain weight as bullet weight went up, powder charge went down. I believe we see the same pattern with all powders listed for this cartridge.

Here are my theories, one there will never be peace in the Middle East.

Two if you were following multiple forums you saw in 2019 rumblings of this cartridge, very early there were postings that are either removed or just very hard to search that had details of the powder and charges used but the discussion was only the 108 ELDM.

I am of the opinion that at the early development stage the process was only considering the military application and all the pressures were actually measured without consideration of the consumer market and once adopted by the military and listed, were hard to walk back from. Hence the 110/108 data on its own sheet maybe.

Is it possible that all or the bulk of the charge weights for projectiles under the 108 grain weight are computer generated? Maybe.

In any case in my opinion there can be no doubt that Hornady built a small amount of head room in the max pressures for the data for the 105/103 and less weight loads.

 

[chromatica]

I did some load development for Hornady 105 BTHP's in my 24 inch Ballistic Advantage barrel. I'm getting 2600 fps with 27.9 gr of CFE223. This is higher velocity than predicted in the latest version of the Hornady reloading manual.

 

[Gtscotty]

We will have to agree to disagree on this and here's my argument. I'll stick the reference to CFE #111 on the burn rate chart and LeverEvolution #113, both listed as good performing powders by Hornady from weights from 75 grain to 110 grain.

I'll list CFE first always.
75 grain
31.6
33.6
80 grain
30.9
31.8
87 grain
30.9
31.6
90 grain
29.4
31.1
105 grain
28.6
29.5
110 grain
29.1
29.7

Do we see the pattern? While the bulletts represent, varmint, monolithic, interlock, ELD expanding, ELD match, as well as hollowpoint match they all are listed as having reasonable or good performance with these two powders.

ALWAYS with these two powders until the 110 grain weight as bullet weight went up, powder charge went down. I believe we see the same pattern with all powders listed for this cartridge.

Here are my theories, one there will never be peace in the Middle East.

Two if you were following multiple forums you saw in 2019 rumblings of this cartridge, very early there were postings that are either removed or just very hard to search that had details of the powder and charges used but the discussion was only the 108 ELDM.

I am of the opinion that at the early development stage the process was only considering the military application and all the pressures were actually measured without consideration of the consumer market and once adopted by the military and listed, were hard to walk back from. Hence the 110/108 data on its own sheet maybe.

Is it possible that all or the bulk of the charge weights for projectiles under the 108 grain weight are computer generated? Maybe.

In any case in my opinion there can be no doubt that Hornady built a small amount of head room in the max pressures for the data for the 105/103 and less weight loads.

We will have to agree to disagree, I don't think you're reading my posts or acknowledging my verifiable examples. It would seem that you have an axe to grind here, and nonsensical conspiracy theories to spread without a shred of anything approaching proof or support.

I gave you clear examples in other, easy to find load data of the kind of load/bullet weight discrepancies you're pointing to as proof of conspiracy and you ignored them because they are inconvenient to the scenario you've made up. They are not at all uncommon and anyone who has been loading for a while and looking at different sources should know that. Full stop.

I've been watching the load data posted by Hornady since the chambering was announced, and there has been no sign of conspiracy, no suppressed data, the files I posted are the first ones published, and they match current data, there have been no revisions down. Period.

Why did you leave the 95gr/100gr data off of your example? It's:
CFE: 29.4gr
LVR: 29.7gr

So the only real discrepancy here is that the 105gr loads are a little lower (not surprising, see my post above) the 100gr and 108gr are pretty much in line.

I normally try not to argue with close minded individuals or those who will stick to their preconceived notions in spite of all evidence, but I'm concerned some folks reading this thread might take you theory as being grounded in fact, and it's not. You are muddying the water around this chambering and scaring people looking to get into it unnecessary, why is that?

 

[David Milisock]

We will have to agree to disagree, I don't think you're reading my posts or acknowledging my verifiable examples. It would seem that you have an axe to grind here, and nonsensical conspiracy theories to spread without a shred of anything approaching proof or support.

I gave you clear examples in other, easy to find load data of the kind of load/bullet weight discrepancies you're pointing to as proof of conspiracy and you ignored them because they are inconvenient to the scenario you've made up. They are not at all uncommon and anyone who has been loading for a while and looking at different sources should know that. Full stop.

I've been watching the load data posted by Hornady since the chambering was announced, and there has been no sign of conspiracy, no suppressed data, the files I posted are the first ones published, and they match current data, there have been no revisions down. Period.

Why did you leave the 95gr/100gr data off of your example? It's:
CFE: 29.4gr
LVR: 29.7gr

So the only real discrepancy here is that the 105gr loads are a little lower (not surprising, see my post above) the 100gr and 108gr are pretty much in line.

I normally try not to argue with close minded individuals or those who will stick to their preconceived notions in spite of all evidence, but I'm concerned some folks reading this thread might take you theory as being grounded in fact, and it's not. You are muddying the water around this chambering and scaring people looking to get into it unnecessary, why is that?

I simply missed them, my fault no subdifuse intented.

I do acknowledge your examples I just don't think they apply here, the 90 grain Hornady is a monolithic, the 95 is a flat base SST, the 105 a Spire Point Boat Tail with a very short bearing surface.

In fact that it is an example, that points to your phenomenon, the one faster powder charge for the 105/95 grain remained the same as the 90 grain but the slower powder dropped to 29.7. A whopping 1.4 grains, then again dropping. 2 grain more for 105 grain, a ELD design.

I was waiting to bring this up after doing some research but the powder burn rate may be a consideration, in your example, in my opinion R15 is significantly faster than I would use for 190 and heavier in a 308, the CFE issue may an example.

I mention nor imply any conspiracy by anyone, in fact I would suggest that reduction of the loads by 1/2 a grain or so was smart business by Hornady. I can't see anything in my posts that suggest any conspiracy. I simply report the progression of available material and deduce data based on the chronological order of data. All based on my 55 years of handloading.

I'm not muddying any water, simply examining and providing a possible concept to explain why the load charges for the 103/105 grain projectiles are lower than the charge weights for the 108/110 grain projectiles. Especially since there is very little difference between the 103, 108 bullet styles, nor much difference between the other match style bulletts except the weights. In any case due to bolt thrust limitations a measure of extra precision should be sought when loading near maximum 6MM ARC AR loads.

Extra caution is a good idea, it certainly won't stop me I have several hundred 107 Sierra and I just bought a box of 103 ELDX, I have primers and 2 pounds of LeverEvolution.

If there is need for extra caution I would say it's not nearly as much that the load data the cause but the very wide spectrum in the quality of AR builds and those building them.

 

[Retired shooter]

Good Evening Gentlemen

Understand different reloading companys state varied powder, varied loads, for various grain bulletts, and produces xxx velocity and safe working pressure .

Is there any way to determine whose powder burn rate chart to be the ( go to chart.) How do you guys determine whose or which chart to be the gospel. Reason for once again asking.

Just received Lyman 51st edition
#96 Alliant power pro 2000-MR
#102 HOGDON CFE22
#104 Leverevolution

Nov 2019 chart
#111 Hogdon CFE 223
#112 Alliant power pro 2000-MR
#113 Leverevolution

Another chart no date, do not know publisher
#140 Hogdon CFE 223
#141 Leverevolution
#143 Alliant power pro 2000-MR

Dont have a problem with last two charts, however why would the Alliant powder now be moved that far to the faster end of the chart. Any way to designate how much faster percentage wise, one is over the other.

Does a reloader have to purchase 5 one pound bottles of powder and extensive testing with ea . Most of you have settled on Lever, does that make it the go to powder. General consensus slower burn powder for heavier bulletts. Is that the reason for Lever to be the favored one.?

Sometimes more knowledge and information can be very useful, other times Not.

Thank you.!

 

[Gtscotty]

Good Evening Gentlemen

Understand different reloading companys state varied powder, varied loads, for various grain bulletts, and produces xxx velocity and safe working pressure .

Is there any way to determine whose powder burn rate chart to be the ( go to chart.) How do you guys determine whose or which chart to be the gospel. Reason for once again asking.

Just received Lyman 51st edition
#96 Alliant power pro 2000-MR
#102 HOGDON CFE22
#104 Leverevolution

Nov 2019 chart
#111 Hogdon CFE 223
#112 Alliant power pro 2000-MR
#113 Leverevolution

Another chart no date, do not know publisher
#140 Hogdon CFE 223
#141 Leverevolution
#143 Alliant power pro 2000-MR

Dont have a problem with last two charts, however why would the Alliant powder now be moved that far to the faster end of the chart. Any way to designate how much faster percentage wise, one is over the other.

Does a reloader have to purchase 5 one pound bottles of powder and extensive testing with ea . Most of you have settled on Lever, does that make it the go to powder. General consensus slower burn powder for heavier bulletts. Is that the reason for Lever to be the favored one.?

Sometimes more knowledge and information can be very useful, other times Not.

Thank you.!

They're just relative burn rate charts, emphasis on relative, they are supposed to let you know in general which powders are on the faster side, which are on the slower side and which are medium-ish. I don't think there is a gospel burn rate chart, nor would such a chart be particularly useful, faster-ish vs slower-ish doesn't tell you anything about the heat of combustion, or volumetric density. It's a very general depiction and not overly useful, that's why they don't spend a whole lot of effort on it (1 page out of 192 with zero explanation in the 2023 Hodgdon manual).

For reference, the 2023 Hodgdon burn rate chart has 108: CFE, 109: PP2000MR, 110: LVR; telling you that they are all pretty similar burn rate, slot in between the Varget and 4350 burn rate areas, and not a whole lot else.

 

[Retired shooter]

Thank you Sir!
How does length of barrel figure in to powder selection.?