mpeltier Posted July 5, 2007 Share Posted July 5, 2007 I found lots of info on the .223/5.56 twist and bullet recomendations and know it well. I am fairly new to the .308/7.62. So, My new DPMS TAC20 has a 1/10 twist barrel with cryo treatment, I see bullet weights from 110 up to about 180 with 147/150 most common for FMJ/Mil. Is there a similar rule of thumb as to what should shoot most accurate in a 1/10 twist. I am not trying to get around testing different bullets/loads just wanting to educate myself to some others experiances to shorten the learning curve as she is expensive to feed. Link to comment Share on other sites More sharing options...
HiCapMag Posted July 5, 2007 Share Posted July 5, 2007 The 1-10 twist is biased for the heavier/longer bullets like 175 SMK (what I use), 185 Lapua, or even 155 Lapua which are very long. HOWEVER, a fella over at SnipersHide did up some loads with 110vmax and they shot very well...he might have had a 1-11, but you get the idea. Link to comment Share on other sites More sharing options...
Dan Sierpina Posted July 6, 2007 Share Posted July 6, 2007 The 10" twist for a .308 is like the 7" twist for a .223. It will do just about everything. You should be able to use 190 Sierra Matchkings with it. In a bolt gun, I think up to a MK 220 grain will stabilize fine. Pick a bullet to practice with and have at it. Link to comment Share on other sites More sharing options...
Patrick Sweeney Posted July 6, 2007 Share Posted July 6, 2007 The 1/10 twist in .308" bores dates back a century. [warning, didactic learning mode] The .30-40 Krag used a 1/10 twist to stabilize the 220 jrn bullets they used. The new Springfield also used it, as the .30-03 (not a typo) used the same 220 grain JRN bullet. When the world turned upside down with the advent of spitzer bullets, everyone scrambled. The new cartridge, the .30-06, used 150 grain bullets, and the case necks were too long for the shorter bullet. The Army saved money by having the existing rifles barrels pulled, set back, re-chambered, and reinstalled. They did not replace the barrels, and so the 1/10 twist remained, even though it over-stabilized 150 grain bullets. Also, to save money and not have different barrels in supply, the barrel length spec was changed. The .30-03 had had a barrel of 24.206" (not kidding) and the .30-06 had a barrel of 24.006" Your 1/10 twist will stabilize any bullet you can find to stuff in a .308 or .30-06. Link to comment Share on other sites More sharing options...
mpeltier Posted July 7, 2007 Author Share Posted July 7, 2007 (edited) Thats interesting. So is the 1/10 twist the only twist rate offered up for the AR10 platform? What do any of the other heavy caliber battle rifles use like the FAL, M1A, G3,? Thanks for any and all responses. Edited July 7, 2007 by mpeltier Link to comment Share on other sites More sharing options...
lmccrock Posted July 7, 2007 Share Posted July 7, 2007 FAL is 1/12". Lee Link to comment Share on other sites More sharing options...
hopalong Posted July 11, 2007 Share Posted July 11, 2007 My match M1a has a 1-10 twist and I have developed two 110 grn loads that shoot 1/4 groups (5 shot) at 100 yds with it. I have not tried them to see what they do farther out as they are for a 100 yd match. It also shoots 168 grn hpbt in a 3/8 group but at 200 yds where I test them at. I have not tried them in my M1a scout squad but it shoots the 147 winchesters in a 1 1/2 at 100 yds with the peeps when I'm having a good day holding it (gun shoots better than I do ) My buddy had a .308 bolt gun that shot 1/12 goups at 100 but it had stablized the bullet enough so it shot 1/2 inch at 200....seems he had a 1- 9 and was shooting 155 grn Palma Match kings (If I can remember that right) Hopalong Link to comment Share on other sites More sharing options...
benny hill Posted July 12, 2007 Share Posted July 12, 2007 My custom dpms has a 1-12" twist in it for 147-150 gr bullets. Link to comment Share on other sites More sharing options...
MasterLefty Posted July 12, 2007 Share Posted July 12, 2007 (edited) Way back when the .308 with a 168hg HPBT was the king of Hunter Class Benchrest, the idea twist was 1:15. In '88, I had my gun rechambered to .30x47, running SG 125gr FBHP. With the 1:15 barrel the gun would shoot .009" group (in ideal weather conditions). During this time Speedy (Tom) Gonzales just set a new world record with a 250-31x score shooting .30x47, 125gr FB and 1:15 twist. However he thought a 1:14 would do better. Today, the .30BR is starting to show promise in varimant (the case is too small for hunter), with 1:17 or 1:18 twist rates. 110gr .925" - 1:18 125gr 1.000" - 1:17 The formula to use for determining twist is: Twist = C*D2/L x (SG/10.9)1/2 where: C=180 for velocities over 1800ft/s (150 for velocities under) D=bullet diameter (inches) L=bullet length (inches) SG=bullet specific gravity (which is 10.9 for lead-core bulletes) I realize that you are discussing 3-gun rifle, where the ranges vary and you may be varying your bullet selection; but if you are shooting a dedicated 100/200 yd bench gun, the above formula will provide the optimum twist. For a good all-around 30cal barrel, the 1:11 or 1:12 twist is an excellant choice. Kenny Edited July 12, 2007 by MasterLefty Link to comment Share on other sites More sharing options...
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