What should I try next?

[Jody Simcox]

Loading for 270 WIN... Nosler brass, H4831SC 56.9 gr behind 130gr AB. Last week I shot 3 groups- 40, 80, and 120 off. By far, the best group was at 120 off (.7”/ES 38) but the most consistent velocity (also by far) was with the 40 off group (1.4”/ES 11). Now, I want to further tweak seating depth (and in much smaller increments). I think I should try 35, 45, and 50 off. My question is should I tweak off the best group or tweak off the group with the consistent velocity?

MV 2860 at 120 off
MV 2840 at 40 off

Thanks for any input

 

[josebd]

I’ve never used a chronograph for working up loads,that’s just me!

 

[Had2muchofForums]

How did you decide on 56.9 grains? Seems like about 60 grains would put you closer to traditional .270 speeds. And keep in mind, the AB is a bonded bullet so it won't expand as much at low velocities (compared to something like the Nosler ballistic tip or Remington cor-lokt).

 

[DngBat7]

Loading for 270 WIN... Nosler brass, H4831SC 56.9 gr behind 130gr AB. Last week I shot 3 groups- 40, 80, and 120 off. By far, the best group was at 120 off (.7”/ES 38) but the most consistent velocity (also by far) was with the 40 off group (1.4”/ES 11). Now, I want to further tweak seating depth (and in much smaller increments). I think I should try 35, 45, and 50 off. My question is should I tweak off the best group or tweak off the group with the consistent velocity?

MV 2860 at 120 off
MV 2840 at 40 off

Thanks for any input

That is such a minor velocity difference, I’d probably go for the accuracy. Probably would be the more effective route down range. But I could be wrong

 

[Had2muchofForums]

Oh and initially don't worry much about the extreme spread. Standard deviation gives a more accurate and complete picture.

 

[Jody Simcox]

Oh and initially don't worry much about the extreme spread. Standard deviation gives a more accurate and complete picture.

A significantly lower ES will always produce a significantly lower SD...right? And I arrived at 56.9 gr after extensive OCW testing... initially moving from lowest recommended charge weight to the maximum in 0.5 gr increments, then 0.2-0.3gr, then 0.1 gr... moving up and down from my best group at the range during that particular round of testing. The AB has been very effective at killing deer for my son (at the distances he shoots- <200 yds), I just can’t get it to group at 4-500 yds like I’ve been able to do with my other guns.

 

[Had2muchofForums]

And although some people say you can't use a chrono for load development, I completely disagree. A consistent chronograph like the magnetospeed can and is the most reliable and objective method to be utilized for developing charge weight. Seating depth needs to be shot on paper, no way around that.

I'm a stickler for recording data. I have dozens of excel pages filled with accurate notes. And what I noticed after a half decade or so is that the ladder test results almost always matched up perfectly with the chrono numbers. The flat spot on the target was also the flat spot on the chrono.

Look for your velocity over a few charge weights (approx 1% apart) to level out. Three to four rounds per. Weight will give an accurate enough average velocity.

Pick the middle charge weight and test seating in small increments. Like .002" at a time. Start touching the lands (or wherever you choose) and work out or in for about 7-8 groups. Look for the groups to tighten up or for where the poi is relatively the same. I've seen both. Smaller cartridges tightened up whereas larger calibers tended to flatten. This part is not set in stone, I only have so many calibers to test.

Good luck and remember there is no substitute for the scientific method.

 

[Had2muchofForums]

A significantly lower ES will always produce a significantly lower SD...right?

If I test 1000 shots and 999 are the exact same velocity, but one round is a squib and registers 100 ft/sec less than the other 999 then my ES is 100 but my st dev is going to be less than one.

1000 rounds with a 75 ft/sec ES and a 25 ft/sec SD imo is a less desirable load than the first.

What do you think?

ES only uses two data points. SD uses them all. So st dev gives a more accurate impression because it uses more data.

 

[Jody Simcox]

If I test 1000 shots and 999 are the exact same velocity, but one round is a squib and registers 100 ft/sec less than the other 999 then my ES is 100 but my st dev is going to be less than one.

1000 rounds with a 75 ft/sec ES and a 25 ft/sec SD imo is a less desirable load than the first.

What do you think?

ES only uses two data points. SD uses them all. So st dev gives a more accurate impression because it uses more data.

So you think I should work off the group that was .040” off (SD 5, but poor group on paper) as opposed to the .120” off group (which looked better on the target but had an SD of 15.5)?

And thanks for your patience...

 

[Had2muchofForums]

So you think I should work off the group that was .040” off (SD 5, but poor group on paper) as opposed to the .120” off group (which looked better on the target but had an SD of 15.5)?

And thanks for your patience...

I wouldn't use either load, but I am curious how you settled on that charge weight??

And no problem, I enjoy it

 

[Dusty Stevens]

See what looks good on target before you ever get out the chrono. All that jazz dont matter if it shoots like azz

 

[Bc'z]

See what looks good on target before you ever get out the chrono. All that jazz dont matter if it shoots like azz

^^^^Right. ^^^
I only use chronograph to get velocity for dope cards, after all load development is done.

 

[Had2muchofForums]

Dusty, you're a good dude and an asset to this site. But, I couldn't disagree more with that statement.

I truly believe, if you were to try this method, you would see the value.

 

[Dusty Stevens]

Dusty, you're a good dude and an asset to this site. But, I couldn't disagree more with that statement.

I truly believe, if you were to try this method, you would see the value.

I have. Pretty much 95% plus of the cases ive shot over the last 25yrs of competition needed fireforming. The negatives far outweigh the positives. That much pistol powder is a bomb if even the slightest compression or wrong medium is used so i will never advocate using cow to form and will actually respectfully speak out against it at every opportunity having seen blown up rifles and injuries come to my shop from using that method. You cant control what people read between the lines on the net. Some folks say half a case of pistol powder then the next guy says cow. The first guy was using a patch or wax plug but didnt mention it- now you get this situation. This rifle was not far from being shrapnel. So whats the advantages of cow forming? Pistol powder and a patch or wax plug would have formed that case the same way with no danger even with a triple charge. Using a bullet and normal load? Perfect case- no danger. You cant control what people interpret from internet posts. So please dont think im disrespecting you- far from that for sure! I just prefer people to take the safe road even if it takes longer to get to the end.

 

[Had2muchofForums]

I have. Pretty much 95% plus of the cases ive shot over the last 25yrs of competition needed fireforming. The negatives far outweigh the positives. That much pistol powder is a bomb if even the slightest compression or wrong medium is used so i will never advocate using cow to form and will actually respectfully speak out against it at every opportunity having seen blown up rifles and injuries come to my shop from using that method. You cant control what people read between the lines on the net. Some folks say half a case of pistol powder then the next guy says cow. The first guy was using a patch or wax plug but didnt mention it- now you get this situation. This rifle was not far from being shrapnel. So whats the advantages of cow forming? Pistol powder and a patch or wax plug would have formed that case the same way with no danger even with a triple charge. Using a bullet and normal load? Perfect case- no danger. You cant control what people interpret from internet posts. So please dont think im disrespecting you- far from that for sure! I just prefer people to take the safe road even if it takes longer to get to the end.

Dusty, I think you have me confused with JMayo.

http://forum.accurateshooter.com/threads/high-pressure-case-pic.3963770/#post-37341436

I'm not talking about fireforming or using pistol powder. I'm advocating this gentleman use a chronograph to record data while loading for his .270 Winchester using H4831sc and 130 Nosler Accubonds.

And that the same flat spot identified on a ladder test will also correspond to a flat spot across velocities on the Magnetospeed.

But to your point about fireforming: like most things I've read from you, we are in complete agreement.

 

[Bc'z]

Dusty, I think you have me confused with someone else. I'm not talking about fireforming or using pistol powder. I'm advocating this gentleman use a chronograph to record data while loading for his .270 Winchester using H4831sc and 130 Nosler Accubonds. And that the same flat spot identified on a ladder test will also correspond to a flat spot across velocities on the Magnetospeed.

But to your point about fireforming: like most things I've read from you, we are in complete agreement.

PatrickH, I have to agree with Dusty about the use of a chronograph during load development. Here's a few of the questions that I have asked myself and other shooters about this subject.
Q, Wont the magnetospeed affect the harmonics of the barrel and give you a difference in poi?
A, why yes it will.

Q, So would it be safe to say it can also affect your grouping during development ?
A, its very possible.

Q, So then I would have to load twice as many rounds per charge so I can shoot for grouping, then shoot for #'s?
A, yes, also doubling # of rounds down barrel.

Q, So if i observe load data and load for either OCW, or ladder test i should be ok as long as i check for pressure signs after each charge weight?
A, Makes sense to me.

 

[Had2muchofForums]

PatrickH, I have to agree with Dusty about the use of a chronograph during load development. Here's a few of the questions that I have asked myself and other shooters about this subject.

Q, Wont the magnetospeed affect the harmonics of the barrel and give you a difference in poi?
A, why yes it will.

Response: Yes, in my experience the magnetospeed can affect poi. But, we are not looking for POI when using the MS. We are looking for a flat spot in velocity. So, where the bullets land are not important. In fact, using this method, you don't even need a target for powder charge development.

Q, So would it be safe to say it can also affect your grouping during development ?
A, its very possible.

Response: Yes, it can affect your grouping just like a barrel tuner. But, again, we are not looking at nor concerned about grouping. We are looking for a node or window that our velocities change very little. You will also see a low SD across these groups of rounds.

Q, So then I would have to load twice as many rounds per charge so I can shoot for grouping, then shoot for #'s?
A, yes, also doubling # of rounds down barrel.

No, it should actually take the same or fewer rounds. Fewer since there is very little chance of ambiguous results.

Q, So if i observe load data and load for either OCW, or ladder test i should be ok as long as i check for pressure signs after each charge weight?
A, Makes sense to me.

Resonse: You could certainly use OCW or ladder, but they can be difficult to decipher. Just look at how many threads there are asking for help interpretting both. In addition, a chrono gives objective data that really can't be messed up when interpreting. It's real easy to pull a shot on a ladder or OCW. Using a chrono, you could pull every shot--but you would still retain the important information.

For seating depth testing, I don't use the MS. Instead I take a page from Tony Boyer's book. This is where I look at the targets for feedback and the chrono probably wouldn't do much good, but I've also never cared to try and see if I could establish seating depth with the chrono; I have my doubts.

Good Questions!

 

[Had2muchofForums]

And to your last comment about OCW and ladder: They work just fine and many people use these methods--I certainly did for many years, as well as a few others. Over time, I found what is consistent and reliable for me. YMMV!!

 

[Had2muchofForums]

Is it your assertion that the flat spot seen on the chrono won't show up on the ladder if performed independent of each other. In other words; if you perform a perfect ladder test w/o the MS attached and identify that flat spot, are you asserting that the same charge weights shot over the MS won't correspond, in the form of consistent velocities and low SD's, to the flat spot seen in the first test w/o the MS attached?

 

[Bc'z]

No I'm sure the #'s should match the flat spot visible on target.
Providing there wasn't operator error during group or ladder test.
Point I'm trying to make is if a reloader is being conscious of published data and keeps his/ her eyes peeled for pressure they should be fine.
Let's look at it another way.
We all know and agree a magnetospeed will change your poi.
How many people have seen the magnetospeed shift under recoil?
With the shift of the chronograph also come a shift of poi in respect to poa. Due to harmonics being different from the shift.
Is this not the same as a barrel tuner works?