6CM testing Results

[Hohn]

Comparing them when shooting the same bullets at the same velocities is more than fair. It takes me more powder, but less pressure to get to velocity than the 6 Creed with the same bullet.

Could be, but suggesting that burning MORE powder can yield a vastly superior barrel life is inherently problematic because the amount of pressure you can drop by going to the slower powder is tiny IF you are keeping MV the same.

Hodgdon data illuminates this point. A basic .243 with a 108 ELD will suffice for comparison. H1000 gives 3051fps in their test barrel at 58,200psi. Dropping down to Retumbo gives 3039fps at 57,500psi. Speeding up to a powder like H4831 gives 3014fps at 59,400. And going faster still to H4350 gives 3015 fps at 59,300.

So from H4350 to Retumbo, we're talking a MV range of 36 fps and a peak pressure range of 2100psi. This strongly suggests that there's no getting around the fact that speed=pressure. If you are pushing a 6 comp match to similar speeds as a .243 AI or 6 creedmoor, the pressure will be VERY close if the powders are similar in basic chemistry. (i.e. Hodgdon Extreme).

 

[Hoser]

Dont know what to say.

Good luck to you.

 

[Laurie]

Could be, but suggesting that burning MORE powder can yield a vastly superior barrel life is inherently problematic because the amount of pressure you can drop by going to the slower powder is tiny IF you are keeping MV the same.

Note:

6mm Competition Match Cartridge — Slower Powder Yields Better Barrel Life
My dad was shooting a 6XC for a while and was getting tired of going through almost two barrels a year. So, he came up with the 6mm Competition Match. Like I said, it is a .243 Winchester with a 31-degree shoulder. This delivers the same (if not better) velocity as the other popular 6mm cartridges, but we get almost double the barrel life because we increased the case capacity, so we can shoot a slower burning powder. The barrel I took to Camp Perry that won the CMP Cup had over 3700 rounds on it when I was finished. [EDITOR: Take note readers! Most 6mm barrels are toast after 2500 rounds.] Granted it definitely needed to come off at that point, but it obviously was still shooting well enough to win!

Accurate Load with Peterson Brass, Berger Bullets, and Vihtavuori N165
The two loads I shot all week were Berger 108gr BT behind Vihtavuori N165 in Peterson Cartridge Company brass for 200 and 300 yards, and then Berger 115 VLD behind N165 in Peterson brass for 600 yards. Both loads are easily going over 3000 FPS. I try to only use the best components for reloading, so that’s why I go with Berger, Vihtavuori, and Peterson. Obviously Berger and Vihtavuori quality are pretty known, but I believe Peterson is right up there with Lapua[.] I’ve visited the Petersen factory many times. I’m always blown away by the time and effort Peterson puts into everything.

[From here: AccurateShooter Daily Bulletin September 22 2019 about Joe Hendricks Jr's 6mm Comp Match XTC Tubegun. Note that the 'bold' emphasis is that of the author or more likely the Forum Boss is his writing / editing the feature, not mine.]

http://bulletin.accurateshooter.com/?s=Joe+Hendricks+Jr&submit=Search ]

Your premise whilst apparently common sense doesn't apply in all circumstances because powders have other characteristics than just burning rates. So your view is probably correct for two powders with the same specific energy levels / flame temperatures but different burn speeds, although other less tangible features / behaviours might make some difference to barrel life in either direction. Viht N165 on the other hand has acquired a reputation for exceptionally cool burning and resulting good barrel life even when normal pressure levels are being produced. I can't comment on N165 effects with XC, Creedmoor, 243 size sixes, but have proven this hypothesis to my own satisfaction in 6.5X55, 284 Win and 284 Shehane. I'm convinced enough to have selected 6mm SLR for a recent build instead of 6mm Creedmoor and will use N165 only (with 105-115s) assuming precision and MVs turn out OK with this powder. Sadly Covid restrictions have stopped me getting as far as even running the barrel in to date.

 

[Hohn]

I read the original 6 comp match article. I don’t doubt that n165 can have substantial barrel-life-enhancing effects. But that would be a feature of n165, not 6 comp match per se.

 

[Laurie]

But that would be a feature of n165, not 6 comp match per se.

Yes - just so! That's the point Hendricks made and I support. BUT ... the larger case cartridge allows the use of N165. The lower capacity 6XC doesn't and the Creedmoor case is at best marginal for this powder needing charge sizes that would produce heavy compression before full pressures are attained.

I saw similar issues with the sevens. Long-freebore 7mm-08 in high-capacity Winchester brass would just hold enough N165 for acceptable performance with 175/180gn match bullets, but at fill-ratios that produced such heavy compression that COALs were all over the place, whilst 284 has enough capacity to happily attain 2,800-2,850 fps / 30-inch barrel MVs with some mild charge compression.

So far as case design (the 'Turbulence Point' hypothesis) saving the barrel goes, there is some evidence that 6mm Rem gives better life than its short-neck / shallow shoulder angle 243 Win contemporary, but I've never signed up to claims that case design in itself can virtually double barrel life. Any change either way has to be relatively small.

 

[Hohn]

Agreed on all points.

I'd personally go 243AI if I wanted to go that route because of ubiquity relative to oddball 31degree shoulder and brass stability. I'm sure the 31 feeds better, but for a bench or prone gun that's mostly single fed I don't see an issue with that much. If you need reliable mag feeding, I can see that been a different thing entirely.

 

[Dgd6mm]

I run a .243 and my Comp Matches both with H1000. Shoulder angle I believe as Laurie. The slower burning H1000 is the main contributor to extended barrel life. Joe Hendricks has done this with the 6.5x.284 and the .243 before the development of the 6CM. The 6CM with dang sure push a 115 DTAC at upper speeds. But note if your looking for better barrel life, keep it under 3200fps.

Don Dunlap

 

[Laurie]

I'd personally go 243AI if I wanted to go that route because of ubiquity relative to oddball 31degree shoulder and brass stability. I'm sure the 31 feeds better,

...............

I was offered a very nice Lawton action rifle that a friend who is a gunsmith / rifle builder made for himself in 6mm Super LR. I always liked the 30-deg shoulder + long neck set-up on the XC and this marriage with 243 Win seemed an eminently sensible wildcat using easily obtained brass and no fireforming. Crucially the dies came with the rifle. When the original well-used barrel was completely shot out (not with N165), that rifle became a very nice 6BR bench Light Gun, but I had the SLR brass, dies and my gunsmith friend still had the SLR reamer, so when the barrel on another six gave up the ghost late last year, a rebarrel to 6mm SLR was the no-brainer choice.

 

[Longrange57]

Note:

6mm Competition Match Cartridge — Slower Powder Yields Better Barrel Life
My dad was shooting a 6XC for a while and was getting tired of going through almost two barrels a year. So, he came up with the 6mm Competition Match. Like I said, it is a .243 Winchester with a 31-degree shoulder. This delivers the same (if not better) velocity as the other popular 6mm cartridges, but we get almost double the barrel life because we increased the case capacity, so we can shoot a slower burning powder. The barrel I took to Camp Perry that won the CMP Cup had over 3700 rounds on it when I was finished. [EDITOR: Take note readers! Most 6mm barrels are toast after 2500 rounds.] Granted it definitely needed to come off at that point, but it obviously was still shooting well enough to win!

Accurate Load with Peterson Brass, Berger Bullets, and Vihtavuori N165
The two loads I shot all week were Berger 108gr BT behind Vihtavuori N165 in Peterson Cartridge Company brass for 200 and 300 yards, and then Berger 115 VLD behind N165 in Peterson brass for 600 yards. Both loads are easily going over 3000 FPS. I try to only use the best components for reloading, so that’s why I go with Berger, Vihtavuori, and Peterson. Obviously Berger and Vihtavuori quality are pretty known, but I believe Peterson is right up there with Lapua[.] I’ve visited the Petersen factory many times. I’m always blown away by the time and effort Peterson puts into everything.

[From here: AccurateShooter Daily Bulletin September 22 2019 about Joe Hendricks Jr's 6mm Comp Match XTC Tubegun. Note that the 'bold' emphasis is that of the author or more likely the Forum Boss is his writing / editing the feature, not mine.]

http://bulletin.accurateshooter.com/?s=Joe+Hendricks+Jr&submit=Search ]

Your premise whilst apparently common sense doesn't apply in all circumstances because powders have other characteristics than just burning rates. So your view is probably correct for two powders with the same specific energy levels / flame temperatures but different burn speeds, although other less tangible features / behaviours might make some difference to barrel life in either direction. Viht N165 on the other hand has acquired a reputation for exceptionally cool burning and resulting good barrel life even when normal pressure levels are being produced. I can't comment on N165 effects with XC, Creedmoor, 243 size sixes, but have proven this hypothesis to my own satisfaction in 6.5X55, 284 Win and 284 Shehane. I'm convinced enough to have selected 6mm SLR for a recent build instead of 6mm Creedmoor and will use N165 only (with 105-115s) assuming precision and MVs turn out OK with this powder. Sadly Covid restrictions have stopped me getting as far as even running the barrel in to date.

Anything close to doubling barrel life with increased case capacity or slower burning powder is a stretch! Probably should start another thread but will make a couple of comments. Regardless of powder used in a particular rifle cartridge, the gases and abrasive media are responsible for barrel erosion. The amount of powder burned per bore size is always the determining factor. A 30BR will always have less erosion than a 300 WM. Slow burn to fast burn has little effect in the scheme of things and each exhibits same basic chemistry. It is a factor to a small degree but both powders still burn through the throat area. Rapid fire, number of shots, and barrel temp. will be a larger factor. All single base have basic chemistry as well as double base depending on ratio of double base. Increasing barrel life to the magnitude of 2X will not happen with a slightly slower burning powder. See attachment.

 

[AckleymanII]

It is very obvious that many of these posters have not seen the HEAT INDEX Chart of how much heat various powders put out.

I played with the 6mm Rem and 243 side by side on red hot p. dog towns. The 6 Rem shot 38.5g of H4895 and the 243 shot 36g of H4895 with Sierra 85g BTHP. The 6mm barrels looked better after 1000 rounds.

So, on an experiment, I played with a 6 XC with a .400 long neck, formed form Lapua 308 brass with the small primer pockets.

On a 30" barrel, I put 900 rounds on the 8T barrel 6 xc barrel, throated .095, since the neck was so long, using H4350 for 500 rounds, then 400 rounds of R#17, nodes at 3150 and 3250 with Sierra 107's respectively.

leade grew .007 in 900 rounds, and there was only a tiny bit of the very slightest fire cracking on the throat at 900 rounds. I attributed the fire cracking to the hotter node with R#17. Groups with the Exell tuner were so small, they were in deed the smallest groups that I shot consecutively in my life, easily beating the many 6ppc's on Panda's and Hall actions that I have owned over the years.

I think that it is true that the turbulance point is influenced by the length of the neck, but the longer neck maybe what is needed for "in your face" night and day differences to be seen.

Lately, I have been shooting a 6 BRA with H4895. If you notice the heat index of the H4895, it is the hottest powder you could ever shoot in a mid size case. I am fighting HARD COOKED ON carbon fouling, and what I consider fairly extensive wear at 1500 rounds that many could consider shot out.

So, I am at a cross roads. I have to accept the Accuracy and lack of barrel wear of the 6 XC with the Slower burning powder, and lower heat index, in conjunction of the long neck vs the Accuracy of the 6 BRA with the hottest powder made with the shortest barrel life of any cartridge I have ever shot.

God as my Witness, the 6 XC-LONG NECK shooting 40.5g of H4350 has at least twice the barrel life of a 6 BRA with H4895.

I wonder if the accuracy of the 6 BRA with H4895 outweighs the difficult cleaning and short barrel life, just part of the "cost of doing business". I am going to try a powder with a much cooler heat index for the 6 BRA, and if I don't get the accuracy with consistency I am looking for, then I will try a different case where I can shoot a slower powder with a low heat index.

 

[Longrange57]

It is very obvious that many of these posters have not seen the HEAT INDEX Chart of how much heat various powders put out.

I played with the 6mm Rem and 243 side by side on red hot p. dog towns. The 6 Rem shot 38.5g of H4895 and the 243 shot 36g of H4895 with Sierra 85g BTHP. The 6mm barrels looked better after 1000 rounds.

So, on an experiment, I played with a 6 XC with a .400 long neck, formed form Lapua 308 brass with the small primer pockets.

On a 30" barrel, I put 900 rounds on the 8T barrel 6 xc barrel, throated .095, since the neck was so long, using H4350 for 500 rounds, then 400 rounds of R#17, nodes at 3150 and 3250 with Sierra 107's respectively.

leade grew .007 in 900 rounds, and there was only a tiny bit of the very slightest fire cracking on the throat at 900 rounds. I attributed the fire cracking to the hotter node with R#17. Groups with the Exell tuner were so small, they were in deed the smallest groups that I shot consecutively in my life, easily beating the many 6ppc's on Panda's and Hall actions that I have owned over the years.

I think that it is true that the turbulance point is influenced by the length of the neck, but the longer neck maybe what is needed for "in your face" night and day differences to be seen.

Lately, I have been shooting a 6 BRA with H4895. If you notice the heat index of the H4895, it is the hottest powder you could ever shoot in a mid size case. I am fighting HARD COOKED ON carbon fouling, and what I consider fairly extensive wear at 1500 rounds that many could consider shot out.

So, I am at a cross roads. I have to accept the Accuracy and lack of barrel wear of the 6 XC with the Slower burning powder, and lower heat index, in conjunction of the long neck vs the Accuracy of the 6 BRA with the hottest powder made with the shortest barrel life of any cartridge I have ever shot.

God as my Witness, the 6 XC-LONG NECK shooting 40.5g of H4350 has at least twice the barrel life of a 6 BRA with H4895.

I wonder if the accuracy of the 6 BRA with H4895 outweighs the difficult cleaning and short barrel life, just part of the "cost of doing business". I am going to try a powder with a much cooler heat index for the 6 BRA, and if I don't get the accuracy with consistency I am looking for, then I will try a different case where I can shoot a slower powder with a low heat index.

You pose some very good questions! I've been shooting for 55 years and been through over 100 custom barrels from various manufacturers and no telling how many hunting rifles with factory barrels. Heat index charts are great but also carry a lot of ambiguity! I have some of the same questions involving short/long neck. Additional heat as we know will aggravate an already bad situation. In keeping with virtually the same basic case size I've shot several different powders in 6BR. For example: LT-32, N133, N135 with light bullets; N140, Varget, H4350, RL-15, 16, 17 and even H4831sc with heavier bullets (80-107). I have seen differences in barrel life....but not 2x or even close. Most of my shooting has been 5 sh groups so I'm not really punishing the barrel or bullets. In our world of punching paper....accuracy is king so we will do whatever it takes. Contrary to belief, I've seen where double base powder such as RL-16 or RL-23 show less fire cracking and better overall life but be prepared to get some kickback on that! Best accuracy was with a single base. Hydrogen and nitrogen content of the mix appear to be the culprit. I'll post another write up I did several years ago. I believe what you are saying, although it sure has not been my experience, .....I also wonder what the outcome would have been had both XC and BRA been shot with something in between like Varget?? Regardless, Powder manufacturers would argue that powder alone would be even remotely responsible for what you have experienced. I don't have much of a recommendation for you, however if XC is doing that well, I would either try perfecting it with the H4350.....or see if another powder would help the BRA. Many will throw rocks at me but you might try Varget or better yet RL-16 if your simply looking at barrel life.

 

[AckleymanII]

Varget is rough on barrels with these smaller mid size case, even 17 Rem and 223's. There maybe some gains in the very long neck on the 6 XC I am shooting.

ON p. dog towns, we hammered barrels hot and hard. H335 was very easy on barrels vs H322 that was hard on barrels along with AA2015. H335 loads got shot 300 rounds in between cleanings, AA2015 and H322 got 125 round shot strings. Heat cooks the carbon on.

The 6 XC with a .400 long neck, shooting H4350, 8t, 105-107g bullets exibit a lack of throat wear that I have never seen in any other case in my life. The barrel when throated to .147 freebore, surely increased case capacity as the bullet was seated half way up the long neck, this surely lowered pressure...darn easy tuning.

When I was shooting NBRSA, a 6ppc with 1200 rounds on it was considered about toast for competition, which is still true of the 6 BRA shooting 105's with H4895 in SOME circles.

Longerange, your input is appreciated.

 

[Longrange57]

Varget is rough on barrels with these smaller mid size case, even 17 Rem and 223's. There maybe some gains in the very long neck on the 6 XC I am shooting.

ON p. dog towns, we hammered barrels hot and hard. H335 was very easy on barrels vs H322 that was hard on barrels along with AA2015. H335 loads got shot 300 rounds in between cleanings, AA2015 and H322 got 125 round shot strings. Heat cooks the carbon on.

The 6 XC with a .400 long neck, shooting H4350, 8t, 105-107g bullets exibit a lack of throat wear that I have never seen in any other case in my life. The barrel when throated to .147 freebore, surely increased case capacity as the bullet was seated half way up the long neck, this surely lowered pressure...darn easy tuning.

When I was shooting NBRSA, a 6ppc with 1200 rounds on it was considered about toast for competition, which is still true of the 6 BRA shooting 105's with H4895 in SOME circles.

Longerange, your input is appreciated.

Thanks! If it means anything, I've had great success with H4350 in 6.5 x 47 both in accuracy and barrel life! Your description of shooting p dogs and hammering barrels round after round make me want to run backwards! I have never tortured a barrel like that, so in that arena you can teach me a thing or two! I shoot comp at 5-600 yards and 5 sh gr that I'm sure would bore most guys! After all these years I've shot barrels from all the main manufacturers and never had a bad one. Bad to me may not mean bad to someone else! However, I've done fairly well and normally agg 1/3 moa! My world is pretty easy on barrels, but have done lots of experimenting with different powders. I'm retired and shoot 4-5,000 rounds a year! Keep me posted or PM me if you get anything figured out! Sounds like the XC is a warrior! Thanks for sharing your experiences!

 

[Hohn]

It is very obvious that many of these posters have not seen the HEAT INDEX Chart of how much heat various powders put out.

I think this misunderstanding might be yours, actually. You are mistakenly assuming that the heat index from QL equates to actual heat in a barrel. There are some on here that would have you believe that 20gr of N165 is "less heat" than 10gr of Varget, despite being twice as much powder.

This is a gross misunderstanding of what is occurring.

Heat and temperature are different things.

Flame temperature is not barrel temperature in the same way that the 2500F flame temperature of a candle isn't your finger's temperature when it passes through, nor is the 6000+F flame temperature of Acetylene in oxygen the temperature of the steel it's welding.


If you look at the heat index chart, you'll see values of 3500 near the bottom and 4000 near the top, with some notably hotter. There are not many things where 3500 is vastly different from 4000. The difference is literally 1/7th hotter. That's a bit like arguing that 35F is "cold" but 40F is "hot". That doesn't seem quite right.


Consider the case of H335 being "easy on barrels" compared to H322. You mean to say that H335 (index: 3980) is vastly different in barrel life compared to H322 (index: 4000) and that "heat index" explains this? The difference between the two powder is 20/4000-- 0.5%.

I find it hard to accept the idea that vastly different barrel life experiences can be attributed to heat index when this example has nearly identical powders in terms of heat index (whatever that actually is-- it has no units and isn't defined that I've seen).


I completely accept the some powders are much harder on barrels in some firing schedules and with some cases. But I reject the idea that quickload heat index explains more than just a tiny bit of this observation.

 

[AckleymanII]

You learn a lot about various powders and barrels when you shoot 20K+ rounds a year in high volume varmint situations.

I don't know anything about Quick load, and the heat index chart seemed to be a possible explanation as to why certain powders cook the carbon on much worse than others along with fire cracking, not to mention extended tapering of the lands on high index powders vs short tapering of lands in lower heat index powders.