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Old 06-02-2014, 09:40   #1
SS454Bob
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LE 6920 bullet weight question

After break in for my new Colt, I'm not too happy with it's accuracy. One of our "range experts!!" where I shoot, says my problem is with the 1/7 twist barrel and the 55 GR bullets I'm shooting.
I'm looking for recommendations of what GR bullets I should be using or is the "range expert" off base with his comments?

I realize the Carbine is not a "target rifle" but I would hope to do better than a 4" group at 100yds!
Thanks
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Old 06-02-2014, 09:58   #2
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What ammo? If it's just 55gr plinking fodder 4" wouldn't surprise me at all. High quality ammo in the 69-77gr range should shrink that by more than half.
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Old 06-02-2014, 12:57   #3
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Your 6920 will perform well with the right ammo. This is a 3x3 post it note from 60 meters with match grade ammo.
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Old 06-02-2014, 13:35   #4
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I was using Remington 223 55 GR. Numbers on the box MC L223R3 ammo, Nevermore.

Nice shooting arvil! What grain bullets on the Match Grade ammo?

By the way, my M4 came with a "flip up" rear sight with no elevation adjustment? I just picked up a carry handle sight for it today and will install it for the next shooting session.
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Old 06-02-2014, 13:40   #5
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Quote:
Originally Posted by SS454Bob View Post
I was using Remington 223 55 GR. Numbers on the box MC L223R3 ammo, Nevermore.

Nice shooting arvil! What grain bullets on the Match Grade ammo?

By the way, my M4 came with a "flip up" rear sight with no elevation adjustment? I just picked up a carry handle sight for it today and will install it for the next shooting session.
Your elevation adjustment is done with the front sight post. You need the proper tool to adjust it or use a small punch, or the tip of a round like I did in boot camp. Additionally, I would also switch ammo to the Federal XM193 55gr. This may help.
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Old 06-02-2014, 13:50   #6
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Next to the rifle itself ammo selection will be the next thing ( aside from the shooter of course) to affect accuracy. Bargain basement 55 grain plinking ammo is likely to do no better than 3 inches out of a carbine. Put match ammo in it and it will act like a different gun. Unless you reload maximum accuracy will only be realized with the match grade 75 cents plus a round ammo. This goes for any rifle not just your colt.
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Old 06-02-2014, 14:03   #7
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I would not be so concerned with Match Grade ammo. The way I look at it, if you are hitting MOF (Minute of Forehead) shots @ 100 yards, you are good to go. Remember, you are shooting a carbine and not a Match Rifle. They are two different animals with different purposes and performances. As with my carbines, hitting MOF @ 100 yards is good for me. My Mk12 Mod0 is good for 1.5" groups @ 100 yards, but then again, that is what it is designed and built to do.
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Old 06-02-2014, 14:10   #8
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Two loads that have performed well for me are Hornady 75g TAP and Federal 69g Gold Medal Match.
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Old 06-02-2014, 14:39   #9
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Thanks for your comments guys!

I'm an old M1 Garand guy and can get better than 3" out of a standard "Service Grade Garand" using Military surplus ammo and much better with my reloads at 100 yards. I'm relatively new to the AR platform and I guess I expected to much "right out of the box" for the Colt.

I did receive an unwanted lecture from my clubs "resident range expert" on the virtues of barrel twist as it relates to bullet weight so that is why I posted these questions.

I have ordered a front sight tool, will get some 60 or greater grain bullets and try again.

Thanks
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Old 06-02-2014, 15:53   #10
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Hi, Bob. You have been using the factory open sights when you have been shooting? No optical sight? If that is the case, then maybe you shouldn't be that disappointed with your 100-yard groups. With a good scope on your Colt, you may find that even with that "mismatched" 55-grain ammo, your groups will be a lot smaller. As for bullet weights, those with more experience than I can correct me if I am wrong, but the conventional wisdom does seem to be that if you shoot light bullets out of a faster-twist barrel such as your 1 in 7, accuracy CAN (not necessarily will) suffer. Conversely, shooting the heavier bullets out of a slower barrel such as the 1 in 9 inch that my Armalite has, can result in poor accuracy. The bottom line is that each rifle handles ammo differently, and what works well in one rifle might be crappy in another, so you just have to experiment to find out what your rifle likes. Good luck with the highly regarded rifle that you have purchased.
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Old 06-02-2014, 16:44   #11
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Quote:
Originally Posted by SS454Bob View Post
Thanks for your comments guys!

I'm an old M1 Garand guy and can get better than 3" out of a standard "Service Grade Garand" using Military surplus ammo and much better with my reloads at 100 yards. I'm relatively new to the AR platform and I guess I expected to much "right out of the box" for the Colt.

I did receive an unwanted lecture from my clubs "resident range expert" on the virtues of barrel twist as it relates to bullet weight so that is why I posted these questions.

I have ordered a front sight tool, will get some 60 or greater grain bullets and try again.

Thanks
In a 1:7 barrel, you can use 55gr up to 77gr. A 1:9 is good for 55gr to 72gr. When I was in the Marine Corps back in the late 70's to early 80's, we were using M16A1s with a1:12 20" barrel. Hitting a silhouette target center mass at 500 yards was no big deal. You just had to make sure you had the right sight picture and sight alignment. The 55gr round travels in an arch and you had to compensate for that at distance. That is why most zeros on the AR15/M16 are now done at 50 yards. If you are hitting center at 50 yards, you should be hitting center at 200 yards. At 100 yards, you may have aim a little lower to hit center. It is up to the individual as to how you want to zero your weapon. Personally, I like 50 yards. Most red-dot optics get zeroed at that range and some at 25 yards. I have found that 50 yards is ideal. As for the M1 Garand, I can relate. I have a 1943 Springfield Armory M1 Garand that is dead on at 100 yards. I use only surplus M2 Ball ammo. It is one sweet rifle. As you will find out, the AR will take a little getting use to, but it is very easily adaptable.

Here is my Colt LE6920
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And my M1 Garand
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Old 06-02-2014, 17:17   #12
Jason D
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The range guy had a point.

Your gun would be better suited towards heavier bullets.
With a 1 in 9" barrel you can get lucky sometimes and have one that can stabilize heavier bullets. Rarely have I seen a 1 in 7" barrel that can run light weight bullets well. Most match rifles will be found with a 1 in 8" that can stabilize the bullets well on both ends of the spectrum.

I would not be shocked if your gun would shoot an inch or less at 100 yards with a 77 or 79 grain match bullet.

Good rule of thumb...

1 in 7" medium to heavy bullets
1 in 8" general light/medium to heavy.
1 in 9" light to medium grain bullets work the best

The 1 in 8" barrel might have trouble with some of the super light weight varmint bullets. Perhaps everything under say 55 grain.
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Old 06-02-2014, 18:20   #13
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Mine would not shoot M193 well at all. It shot sub 1" at 100m with M855
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Old 06-02-2014, 18:54   #14
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My 6920 likes 62gn and up ammo with a 50/200 zero with a 1x4 Millet scope.
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Old 06-02-2014, 20:30   #15
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Thats about what I get shooting prone with cheap 55g ammo with my 6920.
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Old 06-04-2014, 11:18   #16
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My 6920 was shooting 1" @ 50 yrds with irons, bench, using PMC Xtac 55gr two weeks ago.

It is 1/7. Haven't tried 100 yrds yet.

edit;
Did anyone notice he's shooting .223 not 5.56?

Last edited by greyeyezz; 06-04-2014 at 14:43..
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Old 06-16-2014, 20:25   #17
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I ordered a Colt LE6920 and am wondering what ammo to get for it, .223 or 5.56? What grain for range shooting at 25 yards? Seems from what was said this rifle needs at least 55gr or heavier? Thanks.
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Old 06-16-2014, 23:20   #18
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We tested a 6920 next to a S&W Sport back in 2012 and found that accuracy in both improved greatly between a couple of hundred rounds and 1200 rounds. The 8/19/2012 tests were after each rifle had had 1200 rounds fired through it.

https://www.facebook.com/photo.php?f...f&notif_t=like

Both rifles now have about 5000 rounds through them and throat measurements and current accuracy test results should be forthcoming within 60-90 days.

Because S&W no longer makes the Sport with the 5R barrel, the test is no longer strictly repeatable. They do still put the 5R barrel on one of their higher end rifles, so a future test of a 6920 beside another 5R melonie barrel remains a possibility, but increases in our instructor training business makes keeping track of data challenging.
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Old 06-16-2014, 23:35   #19
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One thing that I wanted to note: one of our participants at a Rifle Instructor course fired a .18 inch 5 shot group on 6/1/2014. That group was shot with the test Colt 6920 with Fiocchi 50 grain Vmax loads. The rifle has a Leupold VX-R 2-7x 33 scope. The most impressive thing about the group was that he held under 1.25 MOA so consistently.
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Old 06-16-2014, 23:47   #20
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Also note that the lightweight bullets that the 6920 likes are tipped bullets. The tips make them long for their weight and puts their center of mass well behind their center of pressure, which means that they need to spin at a higher rpm to be stabilized than a non-tipped bullet of the same weight. It is actually bullet length, not weight, which determines how fast a twist is required to stabilize them.
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