Need FTF help

[Old ranger]

My DPMS build is an Areo Presision complete upper, a polymer lower from James Madison Tactical and Magpul stock/magazine.

Problem- with magazine loaded and charging handle released, a round will enter the chamber, but it will not fire. There are no marks on the primer. With the magazine out and a round loaded by hand into the chamber it will fire and eject the case. I cannot figure out why. Any ideas?

[forty_caliber]

There are members here much more knowledgeable than myself.  To me it sounds like the magazine may be keeping the BCG from going into full battery.   After loading a round from the mag, then dropping the mag, will the forward assist move the BCG forward?

I had a similar problem once with an AR pattern mag in a DPMS pattern rifle.

.40

[Robocop1051]

So here's my guess/suggestion....

Disclaimer: I've never heard of this happening before.

I'm thinking there's a drag/snag somewhere in the loading/chambering. This is preventing your rifle from going into full battery.

1. Try a different magazine; steel vs polymer, 10/20/25 rounds. Some rifles just prefer specific mags. One of our members has a CMMG that will not use Gen2 PMAG's, but runs fine with Gen3????

2. Check your extractor. Just make sure there's a full range of motion there. Probably not an issue since your single load is going through no prob. 

3. I should have said this first.... WET!!! How wet is your rifle? The .308 rifles like to be very wet at first. I don't mess around with expensive gun oils for break in. I soak all my BCG's in Mobile1 full synthetic 0w50 to start. After they are broke in, I swap to a CLP or whatever else is on hand. I cannot express WET enough. Keep the chamber clear, but the rest of the upper should splash when it cycles.... seriously. 

4. Buffer and buffer spring: make sure you're using an Armalite AR-10 buffer spring. You may also look into a heavier buffer (H2 or H3 minimally). JP also makes an adjustable weight "Silent Captured Spring" (SCS) system that might work...$$$$

5. Chuck a chamber brush into a rotary tool, squirt some glitz on it, and spin that little bastard to death inside the chamber. It's a cheap $3 sacrifice to smooth out the inside of that chamber. Clean it really good afterwards. Windex will neutralize and clean the acidic polish, then use any spay cleaner after. Make sure to relubricate. The porous metal will be stripped of all protection and will rust like a MFer if you neglect it at this point. 

[shepp]

6. Welcome to the forum feel free to tell us about yourself in the intro section 

[Old ranger]

Using the forward assist does not help. The BCG is chrome. I haven't tried a different mag yet or a "wet" BCG. Extractor seems to work fine. The buffer spring was packaged as an AR-10. Could Itell a difference if I compare it to an AR-15 buffer spring?

[jtallen83]

Have you tried it with just one round in the magazine at a time? Oil it up real good and cycle it by hand with an empty magazine in several dozen times then check for any wear marks on all the parts including the mag.

[Old ranger]

Yes I have tried it with only one round in the magazine. Anything that comes out of the magazine won't fire, only if I hand load one in the chamber.

[Boot_Scraper]

1 hour ago, Old ranger said:

Could Itell a difference if I compare it to an AR-15 buffer spring?

Measure and count coils. Compare to see what you got. 

[washguy]

Old Ranger        Just for you       lemme read the first post of yours  ill be back  spring in front ar15 car spring and the back one ar308 car spring    

So I take it you are using a car buttstock correct? Rifle stocks totally different. Theres a lot of junk parts floating around that arnt even close to what you need...there is no spec in ar308 and then theres no spec from mfg to mfg so you can get fubarred ...see my point?.....the bcg MUST lock back on one round in mag...you aint even there yet....so...lube up the bcg shotgun or better yet take off the upper point it muzzle down and drop in bcg...does it almost go into battery by gravity? look for the gas tube being out of alignment... rubbing of bcg or try it with charge handle too.....lube it too....you have got to start to eliminate problems one at a time.....12 gauge bore mop with flitz and a drill will certainly help with a rough bore....have you taken the bcg aprt and checked the rings..they can get pinched and that will cause problemos of it going into battery....get the proper buffer system parts and check for dragging somewhere and gas tube alignment... 

Oh...what mags you using? do they rock and are they sloppy in the magwell...or tight?                       Wash

 

 

 

 

 

 

 

Edited August 16, 2017 by washguy

[Sisco]

How is the fit between the lower and the upper? When you put a magazine in, does that fit change at all? Sounds like the mag prevents it from going into complete battery. Like Rob says, see if it is an individual magazine issue. And lube it up! What trigger group are you using, by the way?

[Robocop1051]

I'm going to go one more step... your magazine might not be sitting right in the magwell, and that can be attributed to the mag catch/release. If you're using anything other than an Armalite LPK, you need to swap the mag release. 99% of the releases are AR15, or slightly modified AR15. The newer Armalite AR-10A mag catch/release is much beefier than the others and specifically designed for the .308 LR20 mags.

If you search around our forum, I did a semi-lengthy write up on the differences and why people should swap. 

[washguy]

Old Ranger      So I went back again to your post.......So you are telling us that you got yourself an 80% lower and you machined this lower and matched it up with the Aero upper?

Aint saying your machining aint the cause ,but it damn well could be.....  here's your sign .....lol             Wash

Going out on a tiny lil limb here

It aint your upper...take that out of the equation....it fires and ejects when you place bullet in a single shot mode...... borrow someones working lower and bolt it up to your upper.  See if it works or not.....what you have is a clusterfuk right now

 

Edited August 16, 2017 by washguy

[Robocop1051]

I don't remember... was it PSA or AP that was out of spec? That could be the issue too. 

This is the primary reason why I'm so against the 80% market. 80% isn't representative of how much work is required to have a complete rifle... its the maximum amount of quality you can expect to have in an 80% build.