I have an older pre? AI in 308 it’s folding stock. It does not have the quick barrel change. I understand they come with a 1:10 twist barrel so I was thinking of 190gr SMKs...any thoughts?
AI - 308, twist rate? Right bullet
- Thread starter Baer45
- Start date
It will handle anything between 110 grains and 230 or so grains.
Barrel twist is one of the least important influences on accuracy.
Not necessarily. The barrels with English proof marks are mostly 12 twist IIRC.
If your barrel is a marked AINA it is likely a Bartlein 5R and 10 twist. I have both.
While true that either twist may likely not affect accuracy at short distances it could very possibly have negative effects at longer ranges.
If it is a factory barrel versus an AINA, then it is a 1:12 twist made by Lothar-Walther I believe. I shoot 168 SMKs if inside 600 yards and 175 SMKs for 600-1,000.
The 1:12 twist is not optimal for 175s but I have not experienced any issues
The 1:12 twist is not optimal for 175s but I have not experienced any issues
I was reading Long Range Precision by Anthony Cirincione (vol 3) showing the Greenhill Formula and he decided to use a 1:11 inch twist to shoot 180 gr SMKs. So my thinking was a faster twist in 1:10 would jump up the bullet weight to maximize stability....I’ve always shot 175 gr regardless of twist but thought it might be fun to see the difference at1000.....
I believe at some point the 11.25 twist was decided to be the "perfect twist" for 308. Sure do see a bunch of them on custom builds any way.
I shoot the 185 Hybrid ahead of Varget for a muzzle velocity of 2,780 FPS. The barrel is a 26" 10 twist Bartlein 5R chambered by Tooleyand screwed on my trusty AIAW. At the 1,000 yard mark JBM says it is still making 1,433 FPS using 50% humidity and 450 ASL altitude. It is stable and very accurate there. Were as a 20" it calculates to still be okay at that distance (even when adjusting the velocity down for barrel length difference).
My other AW currently has a 12 twist English barrel on it and I usually shoot 155 Scenar bullets thru it. Not because it won't stabilize others but I just like shooting those bullets.
I did try 168 SMK (which should be perfect for 12 twist) Federal Gold Medal Match at 1,000 yards in a AIAE MKII with 20" 12 twist once. The load shot one hole groups at 300 yards and well at 600 yards but it took quite a few rounds at the 1,000 yard target to determine those bullets were key holing at that distance.
I love those Bartlein barrels! Not a suprise on the GMM 168’s...I will give those Hybrids a look! C
