AR15 shooting Problem

[woodman6295]

I recently purchased a Daniel Defense DDM4V7 with a Nikon Coyote Special Scope 4x12x40
It's a 5.56/.223 Caliber. At 50 yards we held a good group. At 100 yards bullets were 9 inches in all
directions. We used .223 ammo in 53 grain, 55 and 62. The 62 got a little better results but not great.
Today I used Hornaday match 75 grain BTHP . We have mounted gun in a lead sled and strapped sled to shooting bench to eliminate most movement and error. The barrel in a 1 in 7 twist. With the last ammo we got a 3 inch group at 100 yards. It appears the heavier bullets work better but I really can't go much heavier. Everybody tells me I should be able to shoot 62 grain bullets and be dead on.
I think I have a problem with the gun or barrel.What do you think?

 

[FearNoWind]

I think we don't have enough information.
Are you shooting reloads or factory ammo?
If it's factory, what factory?
If they're reloads, what's the bullet length (not COAL, but the length of one lonely bullet out of the box)
Your information source is correct that with the 1:7 twist the heavier bullet should perform better than the lighter one. The 1:7 is a military production rate. I think you'd be better of with a 1:8 - but that's just an opinion.
The discussion in this thread will be of interest to you:
http://www.longrangehunting.com/forums/f111/daniel-defense-ddm4v7-accuracy-issue-options-126745/

 

[woodman6295]

I'm not using reloads. All factory ammunition.
I used Hornaday Super Preformance Varmint .223
53 grainV-Max they didn't work. ALSO tried Winchester
223 62 grain fmj they were better but not great.
The last on 75 grains worked the best.

 

[FearNoWind]

Well, based on my rough calcs, you're gonna have to find a bullet that's at least 75 grains and about 1.25 inches long running 3200fps to get anything decent out of that rifle. Of course, that's just one imaginary load, other combinations might work.
Addendum:
I just ran some rough calcs on the 65 grain possibilities. With a 1:7 twist and a MV of 3200fps you'd need a bullet length of about 1.19 inches. Use a bullet puller and measure the length of the 65 grain bullet. If it's 1.19 Inches or greater you should be OK. If not, you'll need to change something else.

 

[woodman6295]

I've already tried the 75 grain bullets and they do work better but still a 2 inch group. I went back to point of purchase and they think there's a problem with the barrel or gun. The are calling manufacturing plant to see what they can do or suggest. They believe it should shoot 65 grain bullets with no problems? So I'm waiting to see what manufacturer will do. Purchase point assures me they will get a fix of some kind.

 

[436]

I recently purchased a Daniel Defense DDM4V7 with a Nikon Coyote Special Scope 4x12x40
It's a 5.56/.223 Caliber. At 50 yards we held a good group. At 100 yards bullets were 9 inches in all
directions. We used .223 ammo in 53 grain, 55 and 62. The 62 got a little better results but not great.
Today I used Hornaday match 75 grain BTHP . We have mounted gun in a lead sled and strapped sled to shooting bench to eliminate most movement and error. The barrel in a 1 in 7 twist. With the last ammo we got a 3 inch group at 100 yards. It appears the heavier bullets work better but I really can't go much heavier. Everybody tells me I should be able to shoot 62 grain bullets and be dead on.
I think I have a problem with the gun or barrel.What do you think?

As the man said.. most likely need a little more information.. Does you rifle have a flash hider or muzzle break.. if yes take it off and try a couple of groups again.
Also double check to be sure your mounts and optics are tight.
You might also check to be sure the barrel is properly seated in the receiver.

Good luck
436