I have a 243 AI with a 1-13 twist. What bullet weight is best for this?
Will it stabalise an 85 grain bullet at AI velocities.

johnny, my 243ai has a 1:10 and it will shoot upto 90gr bullets pretty good 95 burgers shoot very good.
70 to 90 grain bullets should shoot good. if you use the longer vld bullets it may shoot 95's also
Dave

My 1/14 6mm BR will stabilze the 75 gr. V-max and 80 gr. Remington PLHP bullets. A 1/13 might be able to stabilize a 85 gr. flat base bullet, but might not spin a 85 gr. boat tail bullet fast enough for stable flight.

Each barrel is a law unto itself, but I think that you will be able to stablize the 85's in that barrel. I had a 1 in 12 Remington 40X 6mm Rem which would just barely stabalize the 90 grain Berger boattails. Interestingly they shot better at higher elevations and hotter temps... It was definately borderline.

The only way to be sure is to shoot some, and faster is better in this case.

A 1 in 13 is supposed to stabilize bullets up to 75 grs...

Its the length of the bullet, not weight. Check Berger and Sierra website, they list the twist needed. My guess, 75gr or less. Bench Rest shooters use 68gr with 1-13 twist @ 3200 fps.

I have a 243 AI with a Broughton 3-groove and a 1-13" twist. I tried and tried various 68 - 75 gr. bullet weights and could never get any of them to shoot up to my expectations - 0.500" or better 5 shot groups. I finally tried some 80 gr. Bergers (Berger recommends a 1-12") and they shot fantastic. First 5 shot group measured 0.257" and the following range visit I only shot one 5 shot group but it measured 0.411". First load I've found that has showed that kind of consistency. Velocity for the load is running 3550 - 3575 fps out of my 26" barrel with SDs of 12 & 5. Hope this helps.

Kevin

If I was in your shoes, I'd buy one of the "trial packs" of bullets that some places sell...with 6 m/m bullets of several weights (lengths). Then I'd just shoot them, rather than theorizing about it. Your rifle will tell you what is "right" for its barrel.


BTW, most of the short range BR shooters (out to 300 yards) I know who are shooting 68 gr. 6 m/m bullets are using 1-in-14" twist barrels and doing just fine with them. Some even use 1-in-15" twist tubes. (Also, most of them, even with the small PPC case, are getting closer to 3,300 fps or more, rather than 3,200 fps.)