Gunsmithing With New > 150 grain 6.5m bullets a 7 twist a reality in terms of 6.5x284

[rancher5]

I'm re barreling a rifle strictly for distance, with new 150 + gr bullets Sierra , Berger, maybe Hammer, bullets I was thinking of going with a 7 twist 6.5x284, Yes a 7.5 twist would be better maybe, but I have a Shilen on order as I have sometime before building starts I could mak some changes, any thoughts please be free, Discussion is on 6.5-.264 BULLET only verses twist. Thank You

 

[Ledzep]

7 twist @ 3200fps is 330,000 RPM which is spinning pretty fast, but still probably safe, and I think 3200fps is pretty optimistic for a 6.5-284 with 150+ bullets, so you should be fine with a 7 twist.

 

[cwinner]

I shoot them in a 6.5-06AI at 3,100 from an 8 twist at 6,000 ASL with no problems. Also have done quite a few on 7.5 twist, mainly for Creedmoor sized sized cases at 2,700-2,800 ish and they work fine.

7 twist is a little fast in my opinion and practical experience with the Sierra 150's.

I see you being right on the breakpoint with a 6.5X284, I'd likely go 7.5.

 

[beretta_man11]

I was in the same boat. I did a 24" 7.5tw with the intention of more 160gr pills to hit the market. Hopefully it pays off in the end. Good luck with whatever you put together.

 

[DAVETOOLEY]

I've shot custom made 150's out of an 8 at about 2900 FPS and had no problems. That was one of two combinations that I knew gave me an edge at 1K. I never shot them further. Once you get faster than an 8 twist to many variables appear.

 

[rancher5]

I've shot custom made 150's out of an 8 at about 2900 FPS and had no problems. That was one of two combinations that I knew gave me an edge at 1K. I never shot them further. Once you get faster than an 8 twist to many variables appear.

 

[rancher5]

Thank You for responding yes I've been thinking about all the variables, ,this year we have a mile challenge 6.5cal or less, so going past 1000 is the plan, I've read the first batches of 150's from sierra had a tendency to fragment blow up, wobble, Last I heard they were looking into it, this is a single feed 28" finished barrel, if I decide to go with it, I trust Shelin since using a few barrels that all worked as intended. This rifle is a benchrest single feed. New horizon for the 6.5's with very little data since there jut coming out with 150 + bullet weights, Trade off velocity verses weight, I'm at a5700- 6300 feet depending so theres that. Thank You all very much for your experience, thoughts and feedback.

 

[rancher5]

7 twist @ 3200fps is 330,000 RPM which is spinning pretty fast, but still probably safe, and I think 3200fps is pretty optimistic for a 6.5-284 with 150+ bullets, so you should be fine with a 7 twist.

Thank you for running the numbers ,No I don't see 3200fps in my vision, maybe low 2900's will see how pressure goes, No rules yet if the whole bullet needs to hit or just fragments, jest aide, Thanks

 

[DAVETOOLEY]

I'll add that I don't like extremes. In theory it looks good on paper but in practice there are usually issues. YMMV

 

[DAVETOOLEY]

RPM's= speed in FPS X 720 divided by the twist rate.

 

[rancher5]

RPM's= speed in FPS X 720 divided by the twist rate.

Thanks I'll keep that for further test.

 

[bjay]

H

I've shot custom made 150's out of an 8 at about 2900 FPS and had no problems. That was one of two combinations that I knew gave me an edge at 1K. I never shot them further. Once you get faster than an 8 twist to many variables appear.

Howdy dave,
Is this coming from 6.5-284?

 

[DAVETOOLEY]

6.5X55 IMP