New AR Troubles

[Tpb10505]

Just for starters, I am new to semi-auto rifles and the AR platform itself. So I'm inclined to think my noobness has something to do with my issues before the rifle itself...

Today I went to the range with my new AR comprised of a RRA lower and this upper based on an AeroPrecision and Black Hole Weaponry barrel in 5.56 (16", 1 in 8 twist).

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=238168734

I was shooting at 50 yards getting the Magpul BUIS' sighted in. The groups werent stellar but I attributed that to my lack of experience with irons.

Next i put on a Burris AR-332, torquing the mount screws with a Leupold torque wrench and proceeded to adjust the sights. However, my groups were at best 2" at 50yd (closer to 3 or 4). I was shooting from a front rest and rear bag. The ammo used was SWammo's 55 grain in 5.56. Their quality and reputation speaks for itself. The lack of accuracy at such short distances has me puzzled. I had a firm rest, and believe my technique to be adequate for good groups as it has before.

The next issue, likely related to the first, is that in a 20rd magazine the rifle would jam at least 4 times. From what i can tell the issue lay with feeding, and the new round getting stuck on the way in. Or, the next round would fail to load at all, and the chamber would be empty. Im using Magpul PMAGS which are new. Also, the bolt would never hold open on the last round. I assume there may be a simple issue that I in my inexperience with this platform that may be the cause.

Lastly, and this could likely be a nonissue, but again, im not familiar with semiauto as i am with bolt guns. The ejected brass all had a similar trait, in that a good portion of the neck end was flattened. Im not sure if this is a clue or just normal from ejection.

The offending rifle...

I appreciate any help you all can give. Thanks!

 

[Redmanss]

Re: New AR Troubles

You're shooting ball ammo. No matter who loaded it, groups typically run 2-4moa. It looks like it is a carbine length gas system, and the flattened brass is from violent ejection and failing to cycle as it is overgassed. Throw in an H2/H3 buffer and it will slow down the cycle of operation.

As for shooting them, watch the trigger and exaggerate your follow through. They're really finicky.

 

[bbhank]

Re: New AR Troubles

if it was over gassed it would still hold open on last round, ill bet your gas block is loose. Your trigger could account for a great deal of your accuracy issue.

 

[bbhank]

Re: New AR Troubles

also i have found 8 twists like the 62-69 grain ammo.....

 

[Tpb10505]

Re: New AR Troubles

I took the quad rail off and everything seemed in place and tight. I'll try some better ammo next time I head to the range, and see if there is something affordable in the trigger department

 

[rez187]

Re: New AR Troubles

first check your spare tire, if that dont help did you leave in the full size buffer when you put the ctr on?

 

[rez187]

Re: New AR Troubles

ps also try duct tape and bailing wire they fix most problems

 

[whiskeytangofox]

Re: New AR Troubles

What weight buffer are you using, and where was the brass ejecting? i.e. 2,3,4,5 oclock

 

[Flynn]

Re: New AR Troubles

Assuming good ammo and mags, this sounds like a buffer/action spring problem.

 

[turbomilton]

Re: New AR Troubles

i am not new to ARs but i have never had any problems like this so never thought about these things. So what does the weight of the buffer have to do with extraction.

 

[Flynn]

Re: New AR Troubles

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Turbomilton</div><div class="ubbcode-body">i am not new to ARs but i have never had any problems like this so never thought about these things. So what does the weight of the buffer have to do with extraction. </div></div>
It may be short stroking. If this is the case, it's often attributable to underpowered ammo, or a combination of action spring/buffer and ammo. If the ammo is underpowered, an overly heavy buffer would prevent if from fully cycling.

Not long ago, I had similar problems with a LT OBR shooting Black Hills .223 match ammo. I changed the spring and the FTE/FTF problems went away. My particular problem was caused by a combination of underpowered ammo and wrong spring..

I read the op saying the brass was being severly dented on ejection. To me that says the action is too slow (underpowered ammo/spring/buffer).

 

[turbomilton]

Re: New AR Troubles

Thanks that does make sense

 

[Tpb10505]

Re: New AR Troubles

Flynn,

What spring did you use when you changed if you dont mind me asking?

Im not sure of the weight, I can ask the seller of the lower and they may know. when i picked up the brass all of it was at about 4o'clock.

Thanks for all the help everyone

 

[whiskeytangofox]

Re: New AR Troubles

The buffer will have be marked (stamped) if it is a H, H2, H3. If it has no mark it should be a carbine buffer which is the lightest. You should find out what spring you have as well. The only way I know of to figure out what you have is to compare it to a regular carbine spring.

 

[Flynn]

Re: New AR Troubles

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tpb10505</div><div class="ubbcode-body">Flynn,

What spring did you use when you changed if you dont mind me asking?

Im not sure of the weight, I can ask the seller of the lower and they may know. when i picked up the brass all of it was at about 4o'clock.

Thanks for all the help everyone </div></div>

The weapon shipped with a "Springco red spring". I replaced it with a "Springco blue spring".