Most versatile twist rate

[dpodgurs]

So I've got a couple of 308's nailed as my front runners for my 308 build. The question now is what twist rate I should go with. Looking for the most versatile barrel so I can run subsonic and supersonic rounds with little variation in bullet drift.

Right now I'm seriously looking at the R700 5R or the R700 AAC-SD both in 20" threaded barrels (Intend on suppressing in the future). the 5R has a 1:11.25" twist and the AAC-SD has a 1:10" twist. The AAC-SD would be ideal for subsonic rounds because of the faster twist but I am unsure if supersonic rounds using say a 168gr or 175gr bullet are going to have adverse effects, especially with bullet drift at longer distances.

As with anything I could have overlooked something and other twist rates could be better for my application. Let me know what you guys think.

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Dave

 

[Helmet]

Re: Most versatile twist rate

1-10" twist is definitely more than you need for those rounds at supersonic speeds, but I don't think it would cause any problems. Savage 308 rifles come with a 1-10" twist standard. If you were just shooting supersonic speeds then a 1-12" twist would be fine for them, but since you are shooting subsonic you should get the right twist for that and just have a little more twist than you need the rest of the time. You will probably never notice the difference.

 

[dpodgurs]

Re: Most versatile twist rate

Did some more digging and came to the same conclusion so I decided to go with the AAC-SD. Thanks for the info though, every little bit helps.

 

[redbullitt]

Re: Most versatile twist rate

10 twist here, one rifle with an 11. Usually shoot 175s, occasional 168s. No trouble here at all.

Good experience with subsonics and supersonics out of the 10 twist. 180 RN and 150FN shoot well (accurate and stable) down to 25 degrees F (coldest I have shot them).

 

[biffj]

Re: Most versatile twist rate

Depending on what weight bullets you're going to use subsonic 10" twist may be too slow. We normally use an 8" twist in our dedicated subsonic 30 cal rifles shooting up to 240gr matchkings. With a 10" tw I'd be leery of shooting anything over 168-175gr subsonic....at least if I was using a suppressor. On the other hand when we do shoot supersonic lightweight bullets through our fast (8"tw) barrels we don't see any accuracy problems. Use good quality bullets and that will minimize issues with concentricity and balance. That makes the faster spin have less effect on accuracy. For very long range the spin drift is consistant so if you have a faster twist you can account for it out there too. Basic plan is to figure out what you intend to do with the rifle and set it up for that then deal with the other odd uses as they come. Just make sure if you are shooting through a suppressor that your bullets are stable without it before putting it on. I've repaired a number of suppressors that were hit by unstable subsonics fired in barrels that wouldn't stabilize them. Normally its just damage to a couple baffles and an endcap but there is occasionally damage to the tube. That isn't repairable....

Frank