Fast twist barrels light bullets
 

I will throw this out rather than derail the CZ thread.

Speaking mainly of 223 and a 40 grain Vmax but a few 50 grain as well.
When I have run them up to speed in 1-9” twist and faster I have had zero luck getting 100% of the to the target 100% of the time.

Tailoring loads and slowing them down has zero interest for me. I will go to a smaller case.

I had or have some where a list of what is a max RPM for some bullets.

Getting them up to speed exceeded that point, thus ending with my results.


If anyone has had luck with fast twist and varmint type bullets I amm all ears.

I am on the fence on building an AR match 223 with a 1-12” twist.
I have a very accurate Bushmaster with a 1-9” that will rip apart most varmint bullets, this is why I ask.

Interesting - I have never had a problem with a fast twist barrel shooting lightweight bullets and having them come apart, especially with a 9 twist.

Possibly bore or throat roughness causing it?

same here, though if the jackets are to thin a fast twist barrel can twist the front of the bullet off and it will look like a nose cone from a rocket but hollow inside.
at least that's the explanation walt berger gave me for my rifle twisting his 30 gr mef's in two. he replaced them with non mef and they were fine.
rough throat or a bur can contribute as well.

Bore has been looked at with several bore scopes by several different smiths.

I have a Badrock rifle in 223/5.56, 1-7” twist. I know who’s barrel it is, you can forget about everything 50 grains and under.

Buddy has a fair number of fast twist .224’s. He has the same results I did. We have both went to 60 grain varmint bullets. The reduced speed and RPM reduction, no problems.


I have seen some guys with the fast twist 6mm bullets have similar issues.

i think the bottom line is when you fire a cartridge in a really fast twist barrel at high velocity the back of the bullet engages the rifling and begins to twist and the front of the bullet is stationary. the result is a bullet twisted in two in the middle and a catastrophic failure, with a puff of gray down range.

I use 52gn projectiles in my 1 in 10 twist barrel at 3300 FPS and have no problems. Although probably not as fast as yours and not quite as quick a twist either.

Pete

I've heard about this happening, but I shoot 35gr.Dbl. hp Calhoun bullets, 40gr. Sierra, and 50gr. Sierra SMP bullets in my 9T Kimbers without any issues. I imagine the only real thin jacket of the bunch I shoot would be the Calhouns.

No problems here with 1:9 twist and 40gr Vmaxx or NBT, 50Vmax, etc., as others have said. In fact, the 45gr HP Winchester factory Varmint Pak shoot around 0.3MOA for 5 shots at 3675fps.

I think.........
 

....it was an old article in Precision Shooting that said, for most .224 caliber bullets, the limit was about 320,000 rpm.

From my own experience.....for .172 caliber bullets, it's about 380,000 rpm.

Of course, bore condition has a lot to do with it, as well.

Hope this helps.

Kevin

My 223 is 1/9 twist and shoot everything I put down it, as low as the 35 grainers, without any issue of them hitting their target/varmint. :)