Discussion in 'Handloading and Reloading' started by DMW1116, Nov 1, 2020.
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223 is a 1/7 and the 308 is 1/10 twist.
The 1:7 is a military twist meant to stabilize heavier armour piercing rounds - the green-tipped M855. It should stabilize anything from 55 gr up. Mine loves 62 gr. You probably don't want to get too much under 55 gr. They can be "over stabilized" and keyhole or fragment - a problem with the original M16. A 1:9 twist works better for under and around 55 although 1:7 certainly works with 55.
The 1:10 is a pretty normal twist for any .308. Mine has a bracket around 150 gr that it likes. I have shot some 200 gr, but backed up because overall performance started to go off. And, I have gone as light as 115 gr, but I moved away from them after a box.
The 223 generally runs around 4" groups at 200 yards with 55 grain factory ammo. Occasionally it will drop under 2" and run over 4.5" I haven't tried the 75 gr Hornady factory 223 loads at 200, but at 100 it runs 1" to 1.5", mostly the 1.5 side. I'm hoping the 75 gr hand loads work as good or even better.
I haven't shot the 308 enough to see a pattern yet. It has about 30 rounds through it, mostly fine tuning the gas block.
Twist is really dependent on the rifle... my 1:7 Colt H-bar won’t shoot 55grn worth anything, but my 1:8 carbine does; in fact, it shoots them better than 69grn SMK’s, which I found odd.
Yes, I agree that 55 gr is getting borderline. 62-65 gr much better.
Twist rate certainly has an effect on accuracy, but don’t discount bullet quality as a major factor. There are a lot of poor to fair quality 55 gr bullets out there that can barely break 4 MOA in a stock run of the mill barrel, regardless of twist rate. Likewise, there are some 62 gr projectiles that share dubious reputations ( green tip and Armscor FMJ). I have shot plenty of MOA groups with Fiocchi Extrema 40 gr V-Max factory ammo out of stock S&W 1 in 8” twist and even PSA 1 in 7” twist barrels, and duplicated that with handloads with 40 and 50 gr Nosler Ballistic Tips and Hornady V-Max bullets. The old Federal American Eagle 50 gr Tipped Varmint factory ammo was also an eye opener for many AR-15 owners accustomed to cheap factory 55 gr FMJ ammo. Sadly, it has been discontinued by Federal, as it was too good to be sold so cheap. Bullet and barrel are primary determinants of accuracy, if either one is sub par, accuracy is more of an accident than a planned outcome.
My rifle shoots 55 grain pretty good, but the 68 grain stuff was awful. I was shooting 8" paper at 200 yards and missed all but once, after shooting with 55 gr and hitting pretty consistently. It was off enough I was hitting whole separate targets from the one I was aiming at
For what it's worth, my best 223 Remington load uses 77 grain BTHP match bullets and RL-15. It even works great for me in a rifle with a 1:10 twist barrel (the best load I've found).
In the 308 Winchester with bullets from 110 grains up to at least 168 grains, I've found IMR 4064 hard to beat.
This times a thousand.
Bullet quality trumps bullet weight for accuracy.
Got to test these yesterday. The best load was 23.5 grains, with a group just over 1/2" at 100 yards. The max charge of 25 grains was good too, coming in under an inch. So, it seems I either got really lucky at those two charges or I got really lucky and found a good powder/charge/case/primer combo on the first try. Most of the groups were at least as good as the factory loads. Averaging all my test loads gave 1.25", from 0.54" to 1.73". In any case, I'm under the 2 MOA I told myself I'd be happy with on this rifle.
You chose a lucky powder... It's pain sometimes. But it's accurate.
Congrats on being factory ammo. That's always my goal.
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