“Over twisting” a problem?

Shane Lindsey

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Joined
Jul 13, 2010
Messages
1,265
Greetings all,

I have an 8 twist 300 RUM.

Will shooting 215 Bergers be an issue down range? I have heard yes and no so wanted experience from those that have shot similar. Just in the initial stages of development and they have good potential, but don’t want to burn up components if they aren’t going to work at longer ranges. I have looked at the Berger calculator and they are at 2.32, hence this post.

245s seem to be a little tougher to find a load, but getting there.

Thanks.
 

Franko21

Active Member
Joined
Jan 11, 2019
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25
Location
California
The overspin formula that I have seen used is below. Supposedly above 300K RPM and you become more likely to blow up bullets. This will also be influenced by the state of the barrel (e.g., an older rougher barrel will blow them up at lower RPM).

(MV*720)/BTR = RPM

MV = muzzle velocity

BTR = barrel twist rate
 

Canadian Bushman

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Joined
Jan 24, 2012
Messages
1,814
Location
Houston, Texas
More than likely no.

You may get slightly larger groups than you may of with a slower twist but this is arguable, and depends on bullets balance and bullet/case straightness.

You will also have to deal with a bit more spin drift. Ballistic calculator will do this.

On the plus side, higher stability has been shown to aid in the performance of bullets traveling back down to subsonic speeds.

If i shot a rum i would definitely shoot an 8 twist despite these very minor issues. With that amount of powder i would want to be able to shoot the 230, 240, and 250 class 30’s.
 

Shane Lindsey

Well-Known Member
Joined
Jul 13, 2010
Messages
1,265
Thanks,

If these don’t work out, there is always THE easiest loading bullets, Hammer to try out. Have some 181s loaded up to test.

Waiting to see how these 215/245s shake out
 
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