Sierra 150 grain 6.5 Matchking

[6ShotsOr5?]

I got a response from Sierra, the nominal length of the bullet is 1.500”.

 

[Bert Croy]

Al, how many grains of H4350 and how are you seating the bullets also do you know the freebore of the chamber, Thanks

 

[rardoin]

Update for me: 6.5 x55 BJAI / 150 SMK at 2915fps / 30" Brux 7.5tw-4 groove = blow-ups at midpoint on their way to 1000yds. Pulled out of the match. End of 'research project' for me. Back to the Precision Ballistics 142gr @ 2960fps until the .284 is built. Over and out!

 

[FrankG]

Update for me: 6.5 x55 BJAI / 150 SMK at 2915fps / 30" Brux 7.5tw-4 groove = blow-ups at midpoint on their way to 1000yds. Pulled out of the match. End of 'research project' for me. Back to the Precision Ballistics 142gr @ 2960fps until the .284 is built. Over and out!

Hmmm.....what lot number you got on the bullets? I’ve got two different lots and I’ve had no bullet failures at all.

I’m running them at 2700fps in a 1-6.75 twist barrel. Bullet rpm is at 288,000 out of my gun. Your rpm at your velocity and twist is at 279,840. So I’ll say that cancels the rpm thing out in my opinion.

My barrel has 5R rifling. Not a 4 groove

Other possible factors......

How many rounds on your barrel?

Possible cleaning damage or damage from when the barrel was made that could be effecting the jacket?

I’ve got another barrel in 6.5PRC and is a 1-7.5 twist that I’m getting ready to shoot as the weather gets a little better here but I don’t for see any problems.

Later, Frank
Bartlein Barrels

 

[FrankG]

What bore size is your barrel? Is it tighter than standard .256”?

If it’s a tight bore it’s going to work against you. I’m not a fan of tight bore barrels? The tighter bore is going to cut into the jacket deeper which in turn can lead to failures.

I’m going to lean towards ruling out the twist being a problem. I just remembered that while in the design/prototype of Sierra making those bullets we even made them 1-6 twist barrels during testing. There was never a mention of bullet failures at anytime.

At 1-6 twist and 2700fps that would give you a bullet rpm of 324,000rpm. Even mid 200,000rpm is cranking on the bullet and upper 200k and 300k is in the insane world.

Bullet makers are pushing the designs for BC’s etc...and us shooters at times push them faster than they should be pushed or try and run a barrel longer than we should and we ask a lot out of the bullets. In the end we are all pushing the envelope on this stuff.

 

[rardoin]

Frank, thanks for the interest. The barrel is a .265 bore to my recollection and shoots a 142 Precision ballistic over 3000 fps without issue (I run them at 2960fps as that is the sweet spot). I have run the 150 SMK's in a Bartlein 8tw 5R up to 3000fps without failure (several hundred). The Brux barrel is a 4 groove with conventional cut lands. I seem to recall Sierra recommending a canted land barrel but I had the Brux in the 7.5 on hand and was hoping the 'hard' land engraving would not be an issue. I don't have the lot# on hand but will get back to you tomorrow.

Robin

 

[1shot]

I have been running this bullet for a while now in my 6.5 GWI at 2,990 fps. Bartlein 7.5 twist bbl. canted land 32" long. I've has the bullet over 3,100 fps. but it trashed the brass quickly. The latest performance test was at the BSWN. I shot this set up during Palma day on the low end of the range with some squirrely winds. I went 150-11x, 149-11x,144-5x. To date I have had -0- issues with bullet blow ups, and all previous matches indicate that it will shoot.
I hope this helps,

Lloyd

 

[FrankG]

Frank, thanks for the interest. The barrel is a .265 bore to my recollection and shoots a 142 Precision ballistic over 3000 fps without issue (I run them at 2960fps as that is the sweet spot). I have run the 150 SMK's in a Bartlein 8tw 5R up to 3000fps without failure (several hundred). The Brux barrel is a 4 groove with conventional cut lands. I seem to recall Sierra recommending a canted land barrel but I had the Brux in the 7.5 on hand and was hoping the 'hard' land engraving would not be an issue. I don't have the lot# on hand but will get back to you tomorrow.

Robin

Robin, Your welcome on the interest. .265” would be the groove size. Not the bore size. Would be interested if you know what the bore size is.

Whenever you get a barrel from any barrel maker keep the information somewhere in your log book. We always stamp our barrels with bore and groove size, twist.....as well as the s/n. Some barrel makers don’t stamp a s/n. To us it’s important. Tells us what lot of steel it came out of and all the details. It’s a road map.

How many rounds on the Brux barrel?

If you shot the same lot of bullets thru the Bartlein and Brux and only the Brux has had bullet failures that should lead you down to trying to figure out what is going on with the Brux. Not to say it’s not the bullet being part of the problem.

Later, Frank

 

[rardoin]

The Brux has about 800 rounds now. The throat has advanced about 8 thous since round 80. The first few inches of bore has very slight firecracking visible with a Hawkeye...no more than my other barrels in this chambering at this round count. I suspect the type of rifling as the 5R barrels have shot them faster with no failures...but at 8 and 8.5tw.

 

[FrankG]

The two lot numbers I have on the SMK 150’s are.....

012589645333 / 012594192

0118213665656 / 011896002

800 rounds on the Brux. Did the failures happen when the barrel was new or after you had X amount of rounds on it? If it started at a later date then it could be some damage to the bore from cleaning or shooting etc...or you have a build up carbon in the bore at the throat area and in conjunction with the throat getting rough it’s beating up the bullet more than it should and causing problems.

You said the throat has slight firecracking...look for any missing chunks of metal on the edge of the lands. Look up from the chambers case mouth for about 8”. Pay attention to the driving side of the lands.

Later, Frank

 

[rardoin]

I did not start shooting the 150's until it had about 600 rounds down it. Borescope after last cleaning looked good...nothing out of the ordinary. I use a 22" Hawkeye/90deg mirror so a good inspection at least 10" in the breech end. Muzzle end looks fine also. They had been grouping great at 300yds during testing but would throw at least 1/8 shots well out of group. Since I was shooting on an e-target I did not have the ability to check the out of group impacts for lead spray or yaw on impact profile. Again, the 8tw shot them without issue for over 300rds...just not as precise as my 'go to' bullet so I decided to spin them faster in the 7.5 twist. The 8tw barrel had 5R lands...the 7.5 conventional. Is there any lot numbers that have been prone to in flight failures?

Robin

 

[FrankG]

Robin, Again I haven’t heard of any failures from anyone. So no comment on lot numbers that have been prone to in flight failures.

I listed the lots I have. What lot number do you have?

 

[Longrange57]

Robin, Your welcome on the interest. .265” would be the groove size. Not the bore size. Would be interested if you know what the bore size is.

Whenever you get a barrel from any barrel maker keep the information somewhere in your log book. We always stamp our barrels with bore and groove size, twist.....as well as the s/n. Some barrel makers don’t stamp a s/n. To us it’s important. Tells us what lot of steel it came out of and all the details. It’s a road map.

How many rounds on the Brux barrel?

If you shot the same lot of bullets thru the Bartlein and Brux and only the Brux has had bullet failures that should lead you down to trying to figure out what is going on with the Brux. Not to say it’s not the bullet being part of the problem.

Later, Frank

I've shot 2,000 of them...no problems...yet! I do have occasional shot that comes out of group that is a concern. Three different calibers and three different barrel makers. Normally shooting 2740-2830 fps with 8tw. I've shot many at 2930 with 8tw 6.5 x 284. I mentioned on another thread that as we close in on 300,000 rpm its anybody's guess when it will happen. My experience has been that Bartlein barrels are slightly faster than Kreiger, and Kreiger slighly faster than Brux. All three shoot great for me. The 1,000 yard competition is pushing everything to the max as you have already mentioned. Long strings, high temps, high rpm, long barrels, etc. Appears that the bullet just will not handle the abuse. It's a shame because I love the BC.

 

[TZaun]

Robin, Again I haven’t heard of any failures from anyone. So no comment on lot numbers that have been prone to in flight failures.

I listed the lots I have. What lot number do you have?

Frank, I have lot #0118129339595 / 011864308 and I had one blow up. It was my 60th shot in an F-Class match one hot day (98*). I haven't loaded another one since. I have about 850 of them for sale if you want . I was pushing them ~2845 fps in a 7.25-twist 4-groove Krieger. The barrel had very little fire-cracking just starting in the throat. I've shot other bullets out of far, far worse looking throats than that one and never had a lick of trouble. After reading several other accounts of the 150 Sierras blowing up there is definitely something wrong with the bullets. They seemed to want to shoot very good, but as Longrange57 said - they just can't handle the abuse.

 

[FrankG]

I've shot 2,000 of them...no problems...yet! I do have occasional shot that comes out of group that is a concern. Three different calibers and three different barrel makers. Normally shooting 2740-2830 fps with 8tw. I've shot many at 2930 with 8tw 6.5 x 284. I mentioned on another thread that as we close in on 300,000 rpm its anybody's guess when it will happen. My experience has been that Bartlein barrels are slightly faster than Kreiger, and Kreiger slighly faster than Brux. All three shoot great for me. The 1,000 yard competition is pushing everything to the max as you have already mentioned. Long strings, high temps, high rpm, long barrels, etc. Appears that the bullet just will not handle the abuse. It's a shame because I love the BC.

I'm going to say you need a faster twist so that odd shot doesn't leak out of the group. According to my numbers at 2800fps. they need like a 1-7.52 twist min. If your running a 1-8 I'm going to say your too slow on the twist.

I've got a 6.5PRC barrel ready to go and I did a 1-7.25 twist on mine.

Later, Frank

 

[FrankG]

Frank, I have lot #0118129339595 / 011864308 and I had one blow up. It was my 60th shot in an F-Class match one hot day (98*). I haven't loaded another one since. I have about 850 of them for sale if you want . I was pushing them ~2845 fps in a 7.25-twist 4-groove Krieger. The barrel had very little fire-cracking just starting in the throat. I've shot other bullets out of far, far worse looking throats than that one and never had a lick of trouble. After reading several other accounts of the 150 Sierras blowing up there is definitely something wrong with the bullets. They seemed to want to shoot very good, but as Longrange57 said - they just can't handle the abuse.

I got plenty of bullets but thanks for the offer!

Go 5R on the rifling. I'm asking permission from one of the ammo makers if I can use/get they're data but they told me twice now this year the data they have the odd number of grooves helps fight bullet failure. I've maintained that now for several years.

The odd number of lands and grooves....they don't directly oppose one another. This distorts/upsets the bullet jacket less vs. an even groove barrel.

Later, Frank

 

[FrankG]

Robin, Thinking about your gun some more.....you said the bore looks o.k. Looking thru the borescope. If that is the case how does it feel when you pull a patch thru it?

Push the patch breech to muzzle. Don’t exit the bore. Pull the patch back thru towards the breech end. Not really fast and not really slow. Does it feel like it’s getting resistant/rougher feeling as you get closer to the chamber end? If so that would be a indicator that the throat is rougher than you think and or you have heavy carbon build up. If the carbon build up is really heavy this can and will tighten up the bore more then some think it will. A combination of the bore tightening up and a rougher feeling throat this will beat the bullet up more and could be the cause of your bullet failure problem.

Later, Frank

 

[Longrange57]

I'm going to say you need a faster twist so that odd shot doesn't leak out of the group. According to my numbers at 2800fps. they need like a 1-7.52 twist min. If your running a 1-8 I'm going to say your too slow on the twist.

I've got a 6.5PRC barrel ready to go and I did a 1-7.25 twist on mine.

Later, Frank

Thanks Frank, Probably not going any faster on twist. At 2930 where I would like to shoot that puts it around 300,000. Been there done that! At this point I'm having very good results with 147, 140 hyb, and 130 vld. The accuracy these bullets give me have allowed me to win a few matches. Its tempting to move on to 7mm just cant handle the recoil unless gun is really heavy. At this point accuracy with 6.5 x 47 and 6.5 x 55 are allowing me to place fairly high even in tough wind conditions. When I get ready for another barrel I'll be in touch!

 

[FrankG]

Thanks Frank, Probably not going any faster on twist. At 2930 where I would like to shoot that puts it around 300,000. Been there done that! At this point I'm having very good results with 147, 140 hyb, and 130 vld. The accuracy these bullets give me have allowed me to win a few matches. Its tempting to move on to 7mm just cant handle the recoil unless gun is really heavy. At this point accuracy with 6.5 x 47 and 6.5 x 55 are allowing me to place fairly high even in tough wind conditions. When I get ready for another barrel I'll be in touch!

At 2900fps the bullet rpm out of a 7.5 twist is 278,400. At 7.25 twist that is 288k rpm.

I'm running a 6.75 twist on my 6.5CM at 2700fps and that is putting me at 288k rpm also. I have no bullet failures. Shoot 150smk, 140amax box ammo and Hornady 147's all with no issues. 5R rifling.

 

[Longrange57]

At 2900fps the bullet rpm out of a 7.5 twist is 278,400. At 7.25 twist that is 288k rpm.

I'm running a 6.75 twist on my 6.5CM at 2700fps and that is putting me at 288k rpm also. I have no bullet failures. Shoot 150smk, 140amax box ammo and Hornady 147's all with no issues. 5R rifling.

Absolutely, I have had no failures as well. Mostly shooting at lower velocities and 5 shot strings.