Bullets in a 1-9" twist bolt gun or AR...


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magnumman44
January 10, 2010, 08:45 PM
What are the heaviest bullets you have had good results with in a gun with a 1-9" twist? I have a Remington SPS tactical and a new DPMS Sweet 16 that I have some 69 gr and 70 gr bullets...will they work???

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cbrgator
January 10, 2010, 08:47 PM
Generally, you don't want to go much heavier than 62gr.

magnumman44
January 10, 2010, 10:39 PM
Well, in my SPS, the best grouper so far is the 65gr Sierra Matchking boattail bullet...Will be trying the 62-thanks for the advice. We have tried several 55 gr and a few 60 gr, but the 65 has been 1/2" at 100.

taliv
January 10, 2010, 11:13 PM
sierra 69g are good in 7-10 twist barrels
dunno for sure, but i'd bet you could use a 75g too

R.W.Dale
January 10, 2010, 11:26 PM
I have had surprisingly good results with 75grn A-maxes in a 1-9 twist savage. Of course YMMV generally speaking the 1-9 twist kinda has the 69g HPBT designed for it

Steve in PA
January 11, 2010, 12:51 AM
I got great groups with 75gr Hornady TAP ammo out of my 1:9 Bushmaster and Savage rifles.

DBR
January 11, 2010, 01:11 AM
It is not the weight of the bullet that matters but its length. Many rifle barrels are are only approximately the twist they state. You have to test your barrel with any bullet you want to shoot at the maximum range and coldest temperature you want to use it.

A bullet that marginally stabilizes in warm air may not stabilize in cold air. A bullet that marginally stabilizes at 100 yds may not stabilize at 300 yds. As a general rule with normal bullet designs and down to low temps, the 1/9 twist will work with most conventional bullets equal or less than 70grs.

The bullet the military designed the 1/9 barrels around was the 62gr "penetrator". Because of the steel core in the 62gr these bullets are longer than their weight would indicate so conventional bullets slightly heavier usually also work in these barrels.

taliv
January 11, 2010, 09:25 AM
yeah, dbr, but nobody says, "oh, i use the SMK 1.235"s in my guns". weights are used to identify common bullets.

everallm
January 11, 2010, 10:50 AM
In general (and it's not cast in stone)

.223 Remington / 5.56 NATO rule of thumb.....

1:12 - 55 grain max, best with 50 grain or less

1:10 - 60 grain max, best with 55 grain or less

1:9 - 69/70 grain max, best with 65 grain or less

1:8 - 77 grain max, best with 69/70 grain or less

1:7 - made pretty much for the 77 - 80 grain VLD (Very Low Drag) bullets

With a fast twist (1:9 or faster) and a light (like 40 grain) bullet pushed to a high velocity, depending on bullet construction, you can cause the bullet to self-destruct from centrifugal force. Those Varmint Grenade 40+gr out of a 1:8 or 1:9 tend to go "poof" within about 50 feet of the muzzle, pretty/funky to watch but not practically useful.......8-)

Your rifle MAY play nicer out of those weights, only real way to know is try......

DMK
January 11, 2010, 11:40 AM
Many rifle barrels are are only approximately the twist they state. I believe this is very true. One rifle could have a 1:8.5 twist and another a 1:9.4 twist, both labeled as 1:9.

As far as actual experience, I've had good accuracy out to 100y with Black Hills and Hornady 75GR through Bushmaster and Rock River 1:9 twist barrels.

DMK
January 11, 2010, 11:46 AM
The bullet the military designed the 1/9 barrels around was the 62gr "penetrator". Because of the steel core in the 62gr these bullets are longer than their weight would indicate so conventional bullets slightly heavier usually also work in these barrels. Actually the military barrels are 1:7 twist and it's for the longer tracer rounds. Tracer compounds being lighter than the steel or lead of FMJ bullets, tracers of the same weight are longer.

DBR
January 11, 2010, 02:19 PM
DMK:
Correct me if I am wrong: I thought the M16A2 20" rifle was 1:9 for the 62gr bullet and the 1:7 came along for the M4 14.5" carbine and the A3 rifle and the tracer problem in arctic air.

rcmodel
January 11, 2010, 02:31 PM
Nope, the very first Armalite GI AR-15's were 1/14 and they caused problems in arctic testing.

That was changed to 1/12 on the M16 & M16A1.
The M16A2 was changed to 1/7, and the bullet was changed from 55 to 62 grain at the same time.
All later versions of the M16 & M4 use 1/7.

There was never a 1/9 twist M16 version in service.

1/9 is strictly a civilian deal, as it is an ideal compromise to handle most sporting bullets, from very light to the heaviest that still allow loaded rounds to fit in a magazine..

Only the target shooters really need a 1/7 for the very heavy Match bullets used in long range competition.
But, they must be single loaded because they are too long to fit the magazine.

rc

DMK
January 11, 2010, 03:18 PM
Thanks RC. Good answer.

Only the target shooters really need a 1/7 for the very heavy Match bullets used in long range competition. I wouldn't say only target shooters need 1/7. The 1/7 and 1/8 twists handle 75gr and 77gr match rounds very well and loaded hot, these rounds do very well for a self defense and home defense round. Hornady's TAP in 75gr is a great performer as is 77gr mk262 ammo when you can find it.

1/7 will also shoot 55gr just fine, but that's on the low end of its range. 1/9 would be best if you also needed to shoot 40gr varmint loads in your "go to" carbine. If your gun is only used for SD, HD and plinking 1/7 works just fine.


I have a couple 1/12 twist ARs, two 1/9 twist and four 1/7 twist. I shoot 55gr through all of them. I keep some mags loaded with 75gr TAP for the 1/9 and 17 twist guns and I have a few mags loaded with 77gr mk262, but I can only use those in the 1/7 twist guns.

rcmodel
January 11, 2010, 05:35 PM
I wouldn't say only target shooters need 1/7.I knew when I typed that somebody would be along and counter it. :D

However, I would contend that the 1/9 is still the best compromise twist rate for the average .223 shooter.

I'd imagine there are about a million to one 55 grain bullets loaded & sold for every 75gr or 77gr grain match bullet.

And the varmint hunters like the lighter 40-45-50 grain bullets to stay in one piece on the way to the target.

rc

DBR
January 11, 2010, 06:19 PM
Thanks for the info guys. Obviously my AR history is lacking.

FRJ
January 11, 2010, 06:35 PM
I use Sierra Gameking 65gr in my 1_9 mini 14. Shoot 5 into an inch and 20 rapid fire into 1.480". Good enough for me. FRJ

ForneyRider
January 13, 2010, 05:57 PM
I shoot a lot of Hornady 75gr BTHP through my 1:9 AR. They work great as do 69gr SMK.

I have some Berger 73gr to try. Load charges are similar to 69gr and Mr. Berger said I can load them to 2.26 length.

Sierra 77gr SMK are listed as 1:9 compatible. I think they are close in size to 69gr SMK and 75gr Hornady BTHP.

sscoyote
January 14, 2010, 09:59 PM
I'm running 65 SGK's for long-range coyotes these days in my 26" 1:9, but used to use the 65 JLK Low Drags with the old DPMS VLD magazine-
http://i157.photobucket.com/albums/t49/sscoyote1/DPMSVLDmagazine.jpg

lomfs24
January 15, 2010, 12:27 AM
The Greenhill formula is the theoretical formula to determine twist rate.

FOR VELOCITIES UNDER 2,800 FPS
twist rate = (150 * bullet diameter squared) / bullet length
bullet length = (150 * bullet diameter squared) / twist rate

FOR VELOCITIES OVER 2,800 FPS
twist rate = (180 * bullet diameter squared) / bullet length
bullet length = (180 * bullet diameter squared) / twist rate

RockyMtnTactical
January 15, 2010, 01:08 AM
Generally, you don't want to go much heavier than 62gr

??? With a 1/9? Are you serious? My 1/9's do just fine with anything up to 75gr.

Utah1
January 15, 2010, 01:19 AM
69 SMK in my 26" 1/9 barrel Savage Model 12. Also does really well with lighter 50gr bullets. I've shot the 75gr Amax, but they don't group as well as the 69gr SMK. Haven't given up on them yet however.

jbech123
January 15, 2010, 11:24 AM
I have a savage lrpv with a 9 twist. I think all else being equal, a longer barrel will help you go a tad heavier too. I have shot the whole range of factory offerings, from 36gr black hills varmint grenade to the 77gr MK. It shoots them all extremely well(less then .75"), including the 77. My best 3 shot group was actually with the 36gr(.21"!), but I've yet to fire a group over an inch with it.

Mr. T
January 15, 2010, 04:13 PM
For a 1:9 barrel you can go to 75 grains but it's at its limits. Personally anything from 55 to 75 should work in a 1:9. I happen to get my best results with a 69 grain sierra hollow point boat tails.

dagger dog
January 15, 2010, 04:40 PM
Utah1 I'm with you there bud!

The 69gr SMK, Reloader 15 powder, and some body besides myself shooting my 12 FV .223 Savage 1in9 twist will yield groups under 2" at 200 yds! Any thing under the 69 gr mark doesn't buck the wind enough to equal the accuracy of the 69 grainers.

panrobercik
January 15, 2010, 05:19 PM
I've shot SMK 69 in my Savage 1 in 9 with great results. Better than 55 or 62. Lately I've tried Hornady 68 grain that are actually longer than the 69 SMK and got even better groups. The Hornady 68 are as long as some 75 grain projectiles so I suppose those would do just as well.
I've noticed that finding the sweet spot on the seating depth can make bigger difference than the bullet type. That being said, longer projectile can be seated closer to the rifling than the short ones.

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