Comparison Chart of Major AR Brands

[warlord260]

I had a question about barrel steel, and i was wondering if someone could explain. I see the DD barrels state: 4150 CHF. How does that differ from B-11595E steel? I know what the CHF means, just not the difference.
Thanks,

[MistWolf]

Agreed on the 6.8 unless you have a 458 handy. So what do these heavier than 70 bullets do out of a 1/9? Poor accuracy? Less than ideal accuracy? Keyhole? I have shot 75s out of a 1/9 with good results but velocity was 3600, somewhat faster than 5.56 can do.

It's RPM that stabilizes the bullets which is determined by twist and velocity. At 3600 fps, a 1:9 twist will stabilize longer bullets than it will with a velocity of 2900 fps. If the RPM is too slow, the bullet will be unstable and wobble or even keyhole and have a negative impact on accuracy

[Suwannee Tim]

It's RPM that stabilizes the bullets which is determined by twist and velocity. At 3600 fps, a 1:9 twist will stabilize longer bullets than it will with a velocity of 2900 fps. If the RPM is too slow, the bullet will be unstable and wobble or even keyhole and have a negative impact on accuracy

Indeed. I was trying to get the specifics on exactly what occurs, poor accuracy or keyhole but I decided it probably varies depending on exact circumstances. I was shooting a 22/6mm and was getting pretty good results, an inch at 200 and so. One thing that puzzled with one brand of 75 grain bullets was that I never got a 10 shot group. I would shoot 10 times and get 7, 8 or 9 bullet holes. Never 10. Eventually I figured out that the bullets were exploding due to centrifugal force. Loading them down resulted in degraded accuracy.

[warlord260]

I had a question about barrel steel, and i was wondering if someone could explain. I see the DD barrels state: 4150 CHF. How does that differ from B-11595E steel? I know what the CHF means, just not the difference.
Thanks,

So DD uses 4150 grade steel, but is it Mil Spec. B1159E steel?

[Kentucky Cop]

Hey Rob,

Did you ever touch base with Accurate Tool and Rifle reference our discussion?

Thanks,

KC

[mechanic87]

I knew that my purchase of a DPMS was lower grade......thanks to this chart I see how very low it is. Oh well, it gives my a target to shoot for when I can afford to upgrade. Thank you very much for all of the information.

[bobafett]

I knew that my purchase of a DPMS was lower grade......thanks to this chart I see how very low it is. Oh well, it gives my a target to shoot for when I can afford to upgrade. Thank you very much for all of the information.

I don't think there's anything wrong with their lowers, they are made of 7075-T6 like just about everyone else.

[6933]

What their made of isn't the issue. It's their tolerances and tolerance stacking. In other words, what DPMS may say is acceptable a higher quality manufacturer would not.

[bobafett]

What their made of isn't the issue. It's their tolerances and tolerance stacking. In other words, what DPMS may say is acceptable a higher quality manufacturer would not.

Got it, didn't know they had spec issues with their lowers.

[justin_247]

I knew that my purchase of a DPMS was lower grade......thanks to this chart I see how very low it is. Oh well, it gives my a target to shoot for when I can afford to upgrade. Thank you very much for all of the information.

Well, until you do upgrade, there's a lot of things you can do to improve its reliability.

1) stake your carrier key or buy a BCM/DD/LMT full-auto BCG
2) stake your castle nut
3) swap out your buffer for an H buffer
4) get the chamber reamed out to 5.56
5) install anti-tilt followers in your magazines or use PMAGs

Doing these steps should make it run pretty well until you shoot the barrel out or accumulate enough money to upgrade.