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Shade 04-15-2012 05:24 PM

AR-15 Target/Competition Loads
 
I will be working up several loads for my AR for the local Tuesday Night
Rifle League.

I will be shooting my Bushmaster, it has a 1 in 9" twist match grade barrel.
http://www.bushmaster.com/catalog_xm15_BCWA2S20.asp

I have purchased 68, 69 and 75 grain match grade bullets for working up
loads.

Just looking for your ideas, insights and recomendations.

TIA,
Shade

ryguy00 04-15-2012 06:01 PM

First, you bought all of the wrong weight bullets. You have a 1:9 twist so you want to stick to the 55 grainers and similar weights. You will find that a faster 1:7 twist is necessary to stabilize the heavier bullets. If you want to try them anyways, good luck! Everybody gets lucky sometimes.

What type of competition are you loading for? If youre looking for accuracy, ive had good luck with lapua brass, cci br4 primers, win 748 powder. Fireform your new brass to fit your chamber and figure out how far out you need to seat your bullets to get them to just be touching the lands. Since youre shooting an ar, youre going to have to settle for the longest length that will fit in your magazines. See what the min and max charges in your book say to use for your powder. Start right about the middle and work your way up. I usually use half grain increments when testing loads. You will see your groups start to shrink and then they will open back up as you continue to increase powder charge. Keep notes. Go back to where they were smallest and fine tune the powder charge. After that is done, you can play with seating depth a little if you like

Shade 04-15-2012 10:19 PM

Quote:

Originally Posted by ryguy00 (Post 771782)
First, you bought all of the wrong weight bullets. You have a 1:9 twist so you want to stick to the 55 grainers and similar weights.

I know I am pushing the limit with the 75 grainers but 68/69 are regularly
shot with a 1 in 9 twist. The match grade bullets I am going to be working
with are HPBT so the stabilization should be a little better than a FMJ or soft
point. I have done a fair amount of research but this paragraph sums up
most of what I have found, and better than I can.

Quote:

Originally Posted by ar15.com
Special purpose rifles often have uncommon twist rates. For example, if you are building a varmint rifle and want to shoot the short 35 grain, 40 grain, and 50 grain bullets, a 1:12, or even 1:14 twist would be best. On the other hand, long range High Power shooters often select 1:8, 1:7.7, 1:7, or 1:6.5-twist barrels to stabilize the long 77, 80 and even 90 grain bullets used for 1,000 yard competition. Additionally, new testing of heavier rounds (68-77 grains) seems to show that they perform very well in simulated tissue and may be a better defensive choice than 55 grain or 62 grain rounds. The majority of shooters, though, typically shoot bullets of 50 to 69 grains in weight (note that the 62gr SS-109/M855 bullet is as long as a 71 grain lead core bullet) and should select 1:9 twist barrels. At typical .223 velocities, a 1:9 twist will stabilize bullet lengths equivalent to lead-core bullets of 40 to 73 grains in weight.

1:12 twist rifles cannot stabilize SS-109/M855 bullets and 1:7 twist rifles are slightly less accurate with lighter bullets and will often blow apart the thin jackets of lightweight varmint bullets. The 1:7 twist is used by the military to stabilize the super-long L-110/M856 tracer bullet out to 800 yards, but unless your plans include shooting a significant amount of M856, the 1:9 twist rate is better suited for general use.

There is, of course, an exception: if you want to use loads utilizing the heavier, 75-77 grain match bullets currently used by Spec-Ops troops and other selected shooters, you'll want a 1:7 twist barrel. Although military loadings using these bullets are expensive and hard to get, some persistent folks have managed to obtain a supply, and will need the proper barrel twist to use them. Anyone who foresees a need to shoot this ammo should consider a 1:7 twist barrel.

Quote:

Originally Posted by ryguy00 (Post 771782)
What type of competition are you loading for?

We shoot at 200 and 300 yds NRA Hipower match.

Quote:

Originally Posted by ryguy00 (Post 771782)
If youre looking for accuracy, ive had good luck with lapua brass, cci br4 primers, win 748 powder. Fireform your new brass to fit your chamber and figure out how far out you need to seat your bullets to get them to just be touching the lands. Since youre shooting an ar, youre going to have to settle for the longest length that will fit in your magazines. See what the min and max charges in your book say to use for your powder. Start right about the middle and work your way up. I usually use half grain increments when testing loads. You will see your groups start to shrink and then they will open back up as you continue to increase powder charge. Keep notes. Go back to where they were smallest and fine tune the powder charge. After that is done, you can play with seating depth a little if you like

I can fire form my brass and neck size and I have no feed issues with my
AR-15, I was pleasantly surprised. Unfortunately I have a 5.56 Nato
Chamber and cannot get to the bullet to seat just off the lands.

Thanks for the powder recommendation.

Do you really think the barss makes a difference?

My plan was to get Remington brass, conventional load, fireform, trim
and then sort by case weight to get the uniform brass/chamber volume.

ryguy00 04-16-2012 12:54 AM

Well consistency is the key to accuracy. Im more familiar with benchrest type standards of accuracy. Benchrest shooters use lapua brass for a reason. But im not familiar with your type of competition. To be completely honest, i know nothing about it. So whether lapua brass is necessary for you depends on the type of accuracy youre looking for. Are you looking to achieve 1 moa? Half? Quarter? Less? If quarter or less, i would highly recommend lapuas brass. If that tight of a group isnt necessary for what you are doing, then no, you dont need to spend the extra money for lapua brass.

I know you are shooting an ar, so no, you wont be able to touch the lands. Neither can i in mine. But my ar is strictly a blaster for me. 1 moa is good enough for me.

In my 223 remmy 700 however, sub quarter moa is what im getting. The lapua brass, br 4 primers, and 748 powder under berger pills is my recipe for this animal.

748 is one of the cheapest powders you can buy. But so far, ive shot my best groups ever with it in 223. Dont be afraid to give it a shot.

You already have your bullets, so i wont try to sway you. But when they run out, try some hornady a max bullets and berger target bullets. Ive had OUTSTANDING accuracy with both of them. Choose whatever weight you find to work well out of the bullets you already have. Bullet jackets can differ a lot between brands and on paper, the difference can be huge.

No matter what your acceptable levels of accuracy are, here is what i advise: pay attention to what the benchrest guys are using. They are shooting 1/10ths of an inch @ 100 yards. Their bullets, their brass, their powder, their primers are all doing that for a reason. The more accurate you can make your ammo, the easier it will be for the shooter to shoot well. If your ammo will shoot sub quarter moa out of your gun and you really only need to be able to hit a 6" plate, then there is a much bigger margin for error for the shooter.

Shade 04-16-2012 01:35 AM

My competitive shooting is similar to service rifle matches, where the shooter
not the gun or the ammo is usually the biggest variable. We shoot prone and
kneeing or sitting, shooter preference at 200 and 300 yrds on standard
military targets.

I work up loads shooting off a bench at 300 yards and use an incremental
load development method. I have posted it here before. The gun is capable
of sub MOA; I shoot 2-3 MOA in prone. Which keeps me in the black at 300
yds. We shoot iron sights for competition.

I did the 68 and 75 gr bullets I have are Hornady and the 69 gr are Sierras;
all are match grade HPBT and the 68/69' state on the box 7-10" twist barrels.

I will have to get some Bergers and 748.

Thanks,

Txhillbilly 04-16-2012 01:49 AM

Your rifle should have no problem with the 68/69 gr bullets,but depending on just which 75gr bullets you have,they my not shoot very well.
Hornady 75gr BTHP Match bullets shoot great out of my Savage 12FLVSS 223 with a 1-9 twist,but the Hornady 75gr AMax bullets are longer and don't shoot very well with a 1-9 twist.
I have very good results using BL-C(2) and Varget with the heavier bullets,and H335 works great with the 68/69gr.

ryguy00 04-16-2012 02:41 AM

Another thing on the 748: its a ball powder and measures smooth as butter. Always another plus. Im sure there is a better powder out there somewhere. Isnt there always? But i havent tried it yet. As good as it works and measures added to the plus of low cost, ill keep buying it in the 8lb keg and using it for my bolt 223 and my slide fire stocked ar. That ar is a HUNGRY monster! Lol

Shade 04-16-2012 02:44 AM

Quote:

Originally Posted by Txhillbilly (Post 772165)
Your rifle should have no problem with the 68/69 gr bullets,but depending on just which 75gr bullets you have,they my not shoot very well.
Hornady 75gr BTHP Match bullets shoot great out of my Savage 12FLVSS 223 with a 1-9 twist,but the Hornady 75gr AMax bullets are longer and don't shoot very well with a 1-9 twist.
I have very good results using BL-C(2) and Varget with the heavier bullets,and H335 works great with the 68/69gr.

I have the Hornady 75 gr Match, not the A-Max. I know I am pushing the
limits with 75 grainers but hey box of 100 is $22, cheaper than a night at
the bar...

A little more information I live in Illinois so we get almost exclusively
westerly winds, our range shoots to the north so most of the time we have
a distinct cross wind, left to right. So what I might loose in spin stability
I might gain in mass and momentum.

I have Varget on the shelf.

Shade 04-17-2012 07:20 PM

Well here is some follow up on what I have found.

The Greenhill formula is what I was thinking of earlier but could not remember
it.

The following website does it better than I could.

http://kwk.us/twist.html

Based on that site and calculations I ran.

My data is based on the following. Going to Hodgdon reloading data center
I looked at typical .223 Remington loads and velocities for 69 and 75 grain
bullets. The bullet diameters are .224 and the bullet lengths are .978" and
.9835 respectively.

So...

68 gr at 2700 fps needs 1:9.3 twist
68 gr at 3000 fps needs 1:9.8 twist
75 gr at 2500 fps needs 1:8.9 twist
75 gr at 2900 fps needs 1:9.6 twist

So with a 1 in 9 twist, I should be in great shape.


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