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CZ LONG ARMS => CZ BREN => Topic started by: armoredman on April 09, 2016, 05:15:49 PM

Title: What is the barrel twist rate?
Post by: armoredman on April 09, 2016, 05:15:49 PM

Any know? I know AR guys go nuts for that info, guess we should know, too. :)

Title: Re: What is the barrel twist rate?
Post by: Bodene on April 10, 2016, 05:04:04 AM

The only thing I could find that mentions it says "The bore is 6 grooves, one right hand twist in 7 inches." In this article http://www.smallarmsreview.com/display.article.cfm?idarticles=1448 - Bodene

Title: Re: What is the barrel twist rate?
Post by: M1A4ME on April 10, 2016, 07:30:15 AM

If the barrel isn't marked you could find out with your cleaning rod.

Insert the rod from the muzzle end.
Put a patch in the patch tip and screw the patch tip into the end of the cleaning rod.
Pull the patch/tip through the chamber till it contacts the lands and stop.
Use a sharpie to mark the rod.  Just a dot or hash mark will do.
Pull the patch/tip through till you see the mark come back to the same position it was in when you marked it and stop.
Use a tape measure to determine distance in inches from the muzzle to the mark you made.

That's the barrel twist in inches.

.223's used to be (long time ago) 1 turn in 12" or some were even 1 turn in 14".  These were good for 55 grain and lighter bullets.

The 62 grain bullets prompted a change to 1 turn in 9".

The heavier bullets prompted a change to 1 turn in 7" and some are 1 turn in 8".

I actually have a heavy barreled AR15 varmint rifle (I called it the vARmint rifle) that has a 1 turn in 10" barrel.  The only one I've ever seen with that twist rate.  I don't shoot anything heavier than 55 grain bullets in it and it actually does very well with 45 grain bullets.

While the "rule" is not 100%, if you want to shoot the heavier match/hunting bullets that have been developed to try to improve the .223's performance from a varmint cartridge into a better man stopper/deer cartridge you'll most likely need the faster twist 1 turn in 8" or 1 turn in 7" barrels.

Title: Re: What is the barrel twist rate?
Post by: Garmanarnar on April 11, 2016, 02:27:31 PM

805 Bren has a 1:7 barrel.

Title: Re: What is the barrel twist rate?
Post by: armoredman on April 11, 2016, 03:33:39 PM

So a 62 grain slug is probably a really good idea, then.

Title: Re: What is the barrel twist rate?
Post by: RSR on April 11, 2016, 05:01:43 PM

1:8 is sufficient for up to high 70 gr projectiles in .223/5.56.

1:7 barrels were designed to sufficiently spin the long 5.56 tracer rounds.

1:9 is generally best for 60 gr projectiles in .223/5.56.

1:12 works great for 55gr and lighter in .223/5.56.