68 grain hornady match in 1-9 twist DPMS 5.56 nato

J

Jimmc

New member
I have a DPMS 16" oracle upper on a rock river lower. The rifle will shoot 50 grain to 60 grain bullets quite well. This rifle has a 1-9 twist which should shoot 60 to 69 grain bullets. My problem is it does not accurately. 68 and heavier bullets are hitting all over the target from 100 yards. There is as much as two to three inches between each bullet strike. I am using benchmark, varget and imr 4064 in these reloads with an oal of 2150-2158. I have a 1-8 twist RRA varminter 24" stainless bull barrel that shoots 50 grain A-max hornady bullets very well. It will not handle 77+ grain bullets at all. Far worse that the 1-9. Any ideas, thoughts, suggestions will be appreciated.
 
I personally (or rather my RRA Predator Pursuit) love the things. With some 8208 XBR powder and some rem cases with CCI 400 primers am able to get great groups.

Try putting them in in the RRA Varminter. Only thing I could tell you about the 1:9 is that it may just not be able to stabilize them.
 
Last edited:
I know that you have some good powders, but you might try some TAC or Winchester 748 with the heavier bullets and try some with both regular and magnum primers...Start off seating them at magazine length and then shorten them in .005" increments...

First I'd build some test loads (magazine length) with the powder charge in .1gr increments, starting from one full grain below published max by Ramshot... I've found most of my really accurate loads are between .4gr and .7gr below max listed loads...

With your 16" barrel, you may be using a powder combination (Varget and IMR 4064) that is a little too slow and not getting all the available velocity out of round... I know that BenchMark is faster than TAC or W-748, and may be too fast... It seems to work great in .204s and .223s with lighter bullets...

I usually use TAC or W-748 in most of my AR loads, especially with the heavier class of bullets...Both of my .223 ARs are 1/9 16" barrels...and I usually have great results..

If you don't have one, HERE is a link to a burn rate chart...
 
I've tried accurate 2520 loaded at 25.2 grains(kinda strange)with some 69 grain Noslers. I could never get those 68 grain Hornadys to do much for me. The Accurate 2520 works great in my rig. I'm shootin em out of a 1-10 tube at about 3k fps.
Those 77 grainers are some heavy Muthas your going to need a faster twist rate to get them to work. I wouldn't bother burning the powder trying. Use a lighter bullet.
 
I have a Rock River varminter with a 24" stainless bbl. with a 1-8 twist. I plan to shoot the 77 gr. in this rifle. If it does not work I will shoot the weight that will.
 
I loaded 10 68 grain rounds today. Five with 22.0 grains of benchmark and five with 22.8 grains of benchmark. I also loaded 10 rounds of 77 grain sierra hpbt . The powder was exactly the same. Both weights fired from the 1-9 with far better accuracy that the others I had tried. Maybe I am on to something, What do you think?
 
Originally Posted By: JimmcI loaded 10 68 grain rounds today. Five with 22.0 grains of benchmark and five with 22.8 grains of benchmark. I also loaded 10 rounds of 77 grain sierra hpbt . The powder was exactly the same. Both weights fired from the 1-9 with far better accuracy that the others I had tried. Maybe I am on to something, What do you think?

FWIW- So far I have only loaded up 50g, 55g, and 60g bullets for my two AR`s in .223 and with any of these different weights and whatever powders, I have switched to Benchmark and probably wont look back, Win. 748, AA2230, AA2460 and H335, H4895 - accuracy wise I can meet or exceed results with Benchmark.
Not sure what exactly you are asking- what do I (we) think, as long as it is working for you and your working up your loads safely, then thats all that matters.
I do have some 68g .224 dia. HP`s so if you find something that works keep us informed. Both my .223`s are 1/9 twist and one of them is an Oracle w/freefloat handguard.
 
Most all 18 to 20 inch ar's like the heavier bullets. Some 16" like the 69 grain bullets. I am still trying to find the right combination with the powders that I have to make this work.
 
Today I found the answer to my problem with the 77 grain sierras and the 68 grain. That answer is IMR 8208. This is some nice handling powder, not the slowest but it sure helped my rifles out. The groupings of both rifles tightened up quite considerably. This is the best powder that I have ever used, bar none.
 


Write your reply...
Back
Top