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-   -   Problem AR (http://www.firearmstalk.com/forums/f20/problem-ar-43400/)

Secondamendment 06-03-2011 08:42 PM

Problem AR
 
I have a Model 1 sales AR with a 24" fluted bull barrel. I only have a couple of hundred rounds (maybe) through the barrel. Couldn't get it shoot a group with BUIS, we kept raising the front post but it just wouldn't put what I call a group on paper. Later discovered that they make two heights of front posts one for the gas block (which is what I thought I had purchased) and one for the hand guard where mine now sits untested.
Also mounted an enexpensive 4 power scope on the flaptop upper, went too the range and got it sighted in more or less. At this point I don't know what I need to do to get it shoot somewhere near its potential.
1) Have shot a couple of different brands of ammo.
2) Get much better optics maybe the stadia lines are to big (MOA) to get a good group.
3) Clean the barrel better between outings possible the barrel isn't broken in yet.
I know I am older and am have trouble with my eyes but it doesn't seem to effect my ability to shoot a group with my 308 Saiga or my 300 WIN MAG Savage. This thing shoots more of a pattern than a group.

ktmboyz 06-03-2011 10:06 PM

It sounds like you have the wrong front sight. There are two different heights. A rail installed front sight is 1.45 inches from the rail and a gas block sight is 1.60 inches from the top of the block.

At 25 yards that should put you at about 8-9 inches off from center.

Quentin 06-04-2011 04:53 AM

Also there are at least two different railed gas block heights, the S&W M&P-15 OR gas block rail is the same height as a railed handguard so uses that height sight while ArmaLite's shorter railed gas block needs a taller sight. No doubt there are other examples of the different heights. So you may need to get a taller sight for the shorter height.

The poor grouping may be a second problem. Hopefully you just need to find ammo that rifle likes. Or it could be that wobbly front sight that you've backed out too far.

Sniper03 06-04-2011 05:31 AM

I agree with Quentin.

Unless the sight is loose and wobbling. Not getting a good group would have nothing to do with the height of the front or rear sight. You might not be able to get the elevation dialed in with the wrong height of Sights. But it would not prevent the rifle from getting a good group! The impact on the target might be too high or too low with no more elevation adjustment. But would not effect the rifle from shooting accurate groups. Then there is the issue of grain of the bullet compared to the twist of the rifle. For example if you have a 1:12 twist they will not stabilize bullets over 55gr. Therefore not shooting good groups and if the bullet weight for example would be in the 69 grain weight some key holes possible at 100 yards out of the 1:12. Only other thing is a barrel problem. Do not assume that just because they are new they are good. From time to time a bad barrel gets out of the factory. That barrel should be shooting 1/4 to 1/2 MOA Groups at 100 yards.
We can tell you how to check the twist if you do not know. What grain of bullet are you shooting and the brand?

03

mjkeat 06-04-2011 01:04 PM

Its probably a 1:9 twist.

Could the barrel nut could be loose? The barrel might have a bur/deformity somewhere.

Secondamendment 06-04-2011 02:41 PM

re:group dynamics
 
I have been shooting Winchester White Box and American Eagle both in 55gr FMJ.

The barrel is from E R Shaw I can check with Model 1 sales about the twist rate.

Group size is about 3" and centered and was kinda leaning toward the stadia lines in the optic not being in exactly the same place each time I fired, the scope itself is tight so if recoil (what there is) is moving anything in the optic it has to be the stadia lines unless its glass etched.

How do you check to see if the barrel nut is loose?

Like one of your earlier threads was saying there should be no reson this rifle can't turn in better groups.

Keep the ideas comming I'm stumped..:confused:

mjkeat 06-04-2011 03:33 PM

An AR barrel wrench and a torque wrench. I believe its supposed to be around 35 ft #

diggsbakes 06-04-2011 06:12 PM

I'd agree w/ the front post being the wrong height, if your (way off point) groups are at least consistent. But this doesn't just sound like an elevation problem. . . It sounds like the size of the group is the complaint, rather than an extreme variation in elevation.

If they are around 2-3", which is way larger than they should be with that set-up, I'd start looking into the barrel/receiver connection. Then, make sure your gas block is properly aligned with the barrel. I don't remember exactly what type of gas block/front sight combo you had, but to check : 1.) Get your receiver leveled perfectly 2.) get a vial (small level available at most places where gun cleaning supplies are sold) and put it on the block or front sight. If it is slightly canted it could cause this.

mjkeat 06-04-2011 09:43 PM

Quote:

Originally Posted by diggsbakes (Post 517618)
I'd agree w/ the front post being the wrong height, if your (way off point) groups are at least consistent. But this doesn't just sound like an elevation problem. . . It sounds like the size of the group is the complaint, rather than an extreme variation in elevation.

If they are around 2-3", which is way larger than they should be with that set-up, I'd start looking into the barrel/receiver connection. Then, make sure your gas block is properly aligned with the barrel. I don't remember exactly what type of gas block/front sight combo you had, but to check : 1.) Get your receiver leveled perfectly 2.) get a vial (small level available at most places where gun cleaning supplies are sold) and put it on the block or front sight. If it is slightly canted it could cause this.

Would a torpedo level work?

Sniper03 06-04-2011 10:59 PM

Secondamendment,

MJKEAT is correct! The minimum torque on the barrel nut should be 35 Ft. Lbs. It could be slightly more in order to properly align the gas tube with the openings on the barrel nut and in the receiver. I guess maybe I missed it but what kind of hand guard do you have on it. If they are standard type 2 piece handguards just take them off. And see if the barrel nut will move back and forth against the gas tube. If it is a free float quad rail type just move the handguard back and forth griping it at the rear right in front of the receiver. If you get a very slight movement it is a loose barrel nut. Be sure it is not just the movement between the upper and the lower. It will be between the Free Float Tube Barrel Nut and the Receiver. It will only slightly move and less that the normal barrel nut would because the Fee Float Barrel nuts are over an 1 1/4 in length normally Which Means the passage through it is also. So they will have more contact with the gas tube running through it. If it is not that you have a definite barrel problem. I would not hold too much trust in that cheap scope because it could have parallax issues. You advised you are shooting Winchester White Box and American Eagle 55 grains. Even if your rifle is 1:12 / 1:9/ or 1:8 you should be at least getting around 1 MOA inch groups at 100 with that rifle configuration. It is hard to diagnose issues over the Internet. But as MJ stated if the barrel nuts not loose and all of the other things we spoke of are in order. My friend you have a barrel problem. Maybe a factory defect since that does happen on rare occasion. I would certainly call Model One at that point.

03


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