who wants to troubleshoot for me? local gunsmith?

[Robbie2883]

So i do not have time, experience, motivation nor ammo to troubleshoot one of my AR's. I've built several AR's and never had a problem with them. This one though it getting on my nerves. It's a basic spikes lower with a Magpul PRS stock (rifle tube, buffer & spring) and a DPMS 20" SS bull upper. i cannot for the life of me get this thing to cycle reliably. it won't ever cycle steel casing and brass casing getting more rare. Plenty well lubricated, good ammo. last time i went out the first 30 rounds cycled flawlessly, then the next 80 rounds were FTF or jams. Most of the FTF's would eject the shell but not even try to pick up the next round and the bolt doesn't even lock back on the last round so the only things i can think (since i have tried a few buffers/springs) is either head spacing or gas system leak. Like i said i just can't troubleshoot it soooo...advise? or a suggested GOOD smith to run it to? I'm in the niceville area.

or if anyone experienced wanted to hit the range with me and would be willing to help me with it?

thanks guys

 

[Little Jack]

JJ's is a bit of a drive but he's helped several on the forum.

Just shooting in the dark here, not saying you haven't thought about any or all of the below...

gas block pinned/set screw/ clamp on? Would want to make sure the gas block/gas port are lined up. Not a quick fix if the block is pinned. Gas tube appear to in working order? Evidence of gas leak around the base of the gas block?

compared to your other ARs, how does it cycle by hand? Binding? Does the bolt move in and out of the carrier without too much effort? Do the locking lugs engage/disengage properly? Any marking/damage to the bolt?

how does the brass that's been fired look?

Have you tried that upper on another lower?

 

[brasshog]

Here's my two cents. It seems to be a gas problem. Have you looked at the bolt to ensure that the gas rings are NOT lined up ? Something that simple can cause everything that you listed above. Since it's after you have fired it 30 times or so it may also be a carbon/lubrication issue that is retarding the gas system. Just alittle carbon in the wrong spot or possibly too much/too thick a lube ? Also, have you tried measuring the last round that feed reliably and the first round that is FTF (for headespace issues)? Also, what caliber are we talking about? That would bring in the 5.56/223 questions also. I don't know of a gunsmith in your area unfortunately. I'm not one...just an old grunt

P.S.- Stupid question- Your not lubricating that rifle and setting it in the safe vertical are you ? My Remington 1100 would allow the lube to slowly bypass the buffer/piston system in the stock and carry carbon with it. It made it slugish and did all of the above. I had to purposefully clean it one day and I was horrified at the mess inside the buffer area. The gun was clean but that buffer wouldn't let me cycle ammo and I had a hard time with the "high/low brass question".

 

[merkinman]

The question that I have would be head spacing. Next have you use a gas tube cleaner and insured it enters the barrel( try spraying break parts cleaner in the tube and insure good flow in the barrel).

 

[Robbie2883]

Found this today only SS barrel I've ever had but the build up in front of the block and by the tube pin doesn't look normal to me. Still need to pull the bolt and check the rings. I'm going to yank the block off tomorrow and see if its lined up right.

223
Brass looks fine
Lubed properly
No binding
Did the same on another buffer/spring/tube setup

 

[Bluewater Tactical]

It looks to me that the gas block came loose and it isn't lined up over the gas hole in the barrel anymore.

 

[FrankT]

Reinstall the gas block, first, then take your buffer and spring out to inspect and clean.

 

[ksenter]

what quality/brand is that block? You can even see residue by the gas tube pin. Definitely suspect block issues.

 

[Emcm2]

Ksenter took the words right out of my mouth in a blowed up pic you can really see blow by all around the pin you might have a blockage or misalignment

 

[1911Junky]

Looks like the gas block was not lined up completely with the gas hole. A good bit of barrels are designed for a delta ring and when one is using a free float hand guard you now no longer have that spacer there thus if you push the gas block too far...past the holes will not line up. I would do as everyone suggests ....make sure the gas tube is cleaned, gas rings are not Lined up, gas block is perfectly aligned with gas hole I barrel and then try it out. Sounds like a gas issue causing your timing to be way off.

 

[FrankT]

Well I would say the trouble shooting has been quite effective, let us know after reinstalling the gas block.

 

[donr101395]

Looks like the gas block was not lined up completely with the gas hole. A good bit of barrels are designed for a delta ring and when one is using a free float hand guard you now no longer have that spacer there thus if you push the gas block too far...past the holes will not line up. I would do as everyone suggests ....make sure the gas tube is cleaned, gas rings are not Lined up, gas block is perfectly aligned with gas hole I barrel and then try it out. Sounds like a gas issue causing your timing to be way off.

When you re-install it I would smear a little Rocksett on the inside of the block(not near the gas port) and then use it on the set screws as well as stake the set screws. I say Rocksett because it holds up to the heat better than locktite.