Shredding bullets in 6mm CM

[Nicktheshooter]

Thanks for all the replies. Good stuff!

 

[Texas10]

Why do 105 gr bullets survive the 9 twist? Is it lower speed like 2950 fps and maybe heavier jackets?

236,000 RPM, almost 100,000 RPM slower than OP's, and now you're in 6BR territory, not 6mm CM.

I shoot the 105 Hornaday's and 107 SMK'S out of an 8 twist at 2850. That's 256,500 RPM.

 

[Webster]

You're spinning them apart.

Velocity X 720 / twist= 324,000 RPM.

Shoot a heavier bullet, slower. I used the 86 V-Max out of my .243 for deer but that was a 9 1/2 twist.

Always wondered if the rifling engraving weakened the jacket or bond to the core. Obviously doesn't matter if the rpm is in the proper range.

 

[Texas10]

Course or damaged lands, excessive heat or copper build up will put a marginal bullet over the line and in the worst case, blow up during a contest on a hot day. You'll read about shooters who lose a round due to blow ups when the RPM is well in the safe range. It happens, and that's one of the reasons so much money is spent on custom bullets.

 

[Rdlningcltchdmpr]

I was thinking about tooling marks, etc because I have had other bullets (heavier) come apart as well, but some shoot great. Here is another photo from same day shooting 108 ELD-M, 10 shot group @ .08 MOA. Believe it or not though, they will come apart on me at higher velocity as well View attachment 1149850

Probably the rough interior causing it along with too high rpm. Rough bore no good.

 

[Ned Ludd]

Bullet RPM, jacket thickness, barrel length (i.e. frictional heat), a "tight" bore, even the cross sectional shape of the lands, can all be contributing factors to jacket failure. Using a slower twist rate barrel, slowing the velocity of the load, switching to a different manufacturer's bullet that uses a higher quality or thicker jacket, switching to a slightly larger diameter bore, or using a barrel with a different land profile profile such as 5R or 5C rifling, are all approaches that have been successfully used to mitigate jacket failures.

 

[AckleymanII]

60g sierra may work, and 80g Sierra blitz BT should work fine.

 

[Alex Wheeler]

I have shot plenty of 55 blitz, 60 sierra hp, and 55 BTs at 3800+ in 8 twists. Never had a blow up, until they hit then that centrifugal force really does a job! These have all been 4 groove Kriegers.

 

[mgunderson]

Now take into account the bullet is heating up during super sonic flight and the stability of the core is decreasing with the rising temperature..... poof. Early in flight is often over-speed, but it can show up later in flight as well. 300-400 yards is the latest I have personally witnessed.

They have a strange vapor trail too. Almost appears white or smoky before they come apart.

 

[ebb]

Many years ago I tried the 210 Berger in my 300RUM(stock sendero right from the box) , they blew up. Called Berger, the tech says "too much speed , too much RPM, too rough of a barrel. Any one of the three can do it. You've got all three."

 

[GrocMax]

Never had an issue blowing up 58g vmax, and spin them well over 325K. Now the 70 TNT on the other hand, has been spin sensitive for me.

 

[urbanrifleman]

Factory Savage barrels blow up bullets more than others.

 

[SBS]

Factory Savage barrels blow up bullets more than others.

I suspect that the reason we hear about this problem often with Savage barrels is that they are about the only factory target barrels used these days -- high quality custom barrels being the norm otherwise. I think if Remington and Winchester were producing target rifles in the same price range with fast twist barrels, we'd see the same problem with their factory barrels. Costs a little more to go 1st class.

 

[urbanrifleman]

I suspect that the reason we hear about this problem often with Savage barrels is that they are about the only factory target barrels used these days -- high quality custom barrels being the norm otherwise. I think if Remington and Winchester were producing target rifles in the same price range with fast twist barrels, we'd see the same problem with their factory barrels. Costs a little more to go 1st class.

Well they shoot good, but from testing a few of them they blow up bullets that custom barrels don't.

Try the 80 grain Blitz.

It go boom.

 

[Nicktheshooter]

Guess I need to go ahead with a barrel swap then! I bought a Savage for the action and ease of changing barrels but thought I could shoot out the factory first.

 

[SBS]

Guess I need to go ahead with a barrel swap then! I bought a Savage for the action and ease of changing barrels but thought I could shoot out the factory first.

You can shoot out the factory barrel. Just go to heavier varmint bullets and clean frequently. I own a number of Savage factory varmint barrels which see some high volume PD shooting, but I use calibers/bullets which keep the RPMs reasonable, change rifles often to let them cool and clean when fouled much. Also follow same routine with custom barrels and it benefits them too. When buying replacement barrels, try matching twist closer to bullet selection requirements.

 

[gman47564]

heat plays a big role in bullets blowing up … in 90 + temps I was having 90 gr. berger vld's blowup after 8 or 10 shots... the temp droped into the 70's and the problem went away...

 

[Dgd6mm]

Guess I need to go ahead with a barrel swap then! I bought a Savage for the action and ease of changing barrels but thought I could shoot out the factory first.

Barrel swap, or,
I know that if it was myself, and I wanted to shoot this factory barrel, I just step up to a heavier bullet.

 

[fatelvis]

If you find tooling marks are the problem, and you’re thinking of changing the barrel, first try using the Final Finish kit by David Tubb. It moves your throat out a bit, but really smooths things up well when done according to directions. I used it on my new RPR barrel as a last resort, and It worked beautifully.