6 cm twist rates (7 vs 7.5) and elevation

[dirtytough]

I’ve seen more reports of ELD m’s going poof than any other bullet. I’ve had issues with the 52’s.

When I contacted Hornady 300,000 RPM’s was their max.

I wouldn’t be too worried about it. If for some reason you have issues you can always swap to Berger, Barnes, Sierra, etc. Even if you are around 3050 FPS you are still less than 315k RPM’s. I would go 1-8 or 1-7.5 on your next barrel though.

Blowing up bullets is more a result of the grooves and bore diameter.

Iv got a lot of rounds through 7 twist 6 and 22 cal with zero issues using 6 groove .219/.237 bore barrels.

I’ve always wondered what the best number of grooves is for bullets staying together. I have never came across a study on it.

 

[Article 4]

I am running a 7.5 twist in my current 6 CM with 115 Bergers at 2955 fps out of a Bart #13 Carbon at 25" length. I calculated twist rates and optimal performance for the length of that bullet considering I will be using the rifle for both hunting and target/range time.

 

[Lawnboi]

I’ve seen more reports of ELD m’s going poof than any other bullet. I’ve had issues with the 52’s.

When I contacted Hornady 300,000 RPM’s was their max.

I wouldn’t be too worried about it. If for some reason you have issues you can always swap to Berger, Barnes, Sierra, etc. Even if you are around 3050 FPS you are still less than 315k RPM’s. I would go 1-8 or 1-7.5 on your next barrel though.



I’ve always wondered what the best number of grooves is for bullets staying together. I have never came across a study on it.

I think there are a bunch of factors involved. Non tight bores are a starter. Seems fairly common to find .218 and .236 bore 22/243 blanks all over. That’s a lot of extra squeeze.

Then there’s number of grooves, anywhere from 3-6.

Not to mention carbon fouling. I can say for certain I can feel that first few inches of barrel a lot more when cleaning. Scope says it even more.

Hornady did say long barrels also can propagate the problem, maybe just more area for friction, I don’t know.

Either way, though I prefer to shoot bergers for my 6mm stuff, I have close to 2000 Hornady bullets going ~3k in 7 twist, 6 groove barrels and have yet to see one poof.

I would have zero concern shooting a 7 or 7.5 twist 6 creed. Though given the chance to choose I probably go with a 7.5 twist 237 bore barrel

 

[wind gypsy]

It seems tight bores, rough bores, hot bores, longer barrels, high RPMs, 3 and 4 grooves, and conventional lands (vs canted lands) all can contribute to jackets going poof.