New AR FTE problem

[ANDERSON MEDIC]

I assembled my new PSA AR about 3 weeks ago and took it out for the third time today. It is a PSA dissipator kit w/ 16'' barrel on a patriot defense lower. Has mil-spec buffer tube and standard psa bcg. I have used tulammo in every semi rifle i have owned with great success. Today i was using a mix of tulammo and federal 55gr fmj rounds. I had a disturbing amount of fte's while firing using multiple pmags. As i watched my father i law fire the rifle it looked as though the bolt was not reaching the farthest back point possible in the cycle. Almost as though the rounds didn't have enough kick to cycle the bolt fully rearward. This caused the neck of the fired casing to not be able to fully clear the ejection port and as the bolt returned to the forward position it jammed as the new unfired round from the magazine and the spent casing that had not fully ejected came into contact with one another. Is it possible that the buffer spring is a bit too stiff for this ammo and that i could fix the problem by getting a "softer" buffer spring? Is this an option? Or is the cause of the problem likely somewhere else. My first outings with this ammo i had no problems, so what are some other possibilities that could be causing this? Thanks in advance for any advice guys.

[Guest nysos]

Can you cycle it by hand without any issues, or does it seem harder than it should or hang up at any point? If so, something is probably out of spec - likely the buffer tube.

If it doesn't seem harder than any other rifle you have, it is likely the gas block not being lined up over the gas ports on the barrel perfectly. Could be getting too little gas to cycle the BCG all the way back so the rounds can eject properly.

[Dolomite_supafly]

It is a problem with gas. You either have the gas block partially blocking the gas port in the barrel or the gas port is too small to fire the ammo. I have seen a few barrels lately with smaller gas ports than what is needed. Also, check to make sure the gas key is properly staked and tight.

When you disipator style, where is the gas port located? At the carbine position or the rifle position?

If you can give me the info I can tell you what port size you probably need. Then you can start with that and go up a few .001" at a time until it cycles reliably. Another thing you need to do is oil the running surfaces well during the initial break in. Ammo differences between commmercial ammo and milspec ammo can be a problem as well but it is rare that a gun is on that fine of an edge that it will not cycle commercial but will cycle milspec. The fix for this is just to open up the gas port in the barrel.

You should not have to get a lightweight spring or lightweight buffer. The gun should run fine with milspec buffer and spring providing it is getting the correct amount of gas.

Dolomite

[Clod Stomper]

Edit: D'oh! Dolomite beat me by a minute

^ This. Or the gas port could be too small (it has happened). Or the gas key could not be tightened down. Could be several variables. Could even be the ammo. There are several folks in this area, including myself, who would be happy to help you diagnose it.

Just curious, are you with Anderson Co EMS?

Will

Edited September 10, 2012 by Clod Stomper

[ANDERSON MEDIC]

Wow thanks for all the quick replies you guys. To do a reply to all:

1: It is cycling fine by hand. Does not feel any different from any other ar that i have manually cycled the bolt on

2: It is a mock dissipator. The upper came to me from psa completely assembled with a rifle length handguard covering a lo-pro gas block that is in the carbine location.

3: Yeah i work for Anderson co. EMS. Oak Ridge station 2.

[TMF]

Just a reference question there Dolo, what would be the best method for accurately increasing the gas port size? If done this before on a machine gun barrel using a Dewalt, bench vise and titanium bits, but wouldn't dream of doing it that way on one of my private guns.

[Dolomite_supafly]

Just a reference question there Dolo, what would be the best method for accurately increasing the gas port size? If done this before on a machine gun barrel using a Dewalt, bench vise and titanium bits, but wouldn't dream of doing it that way on one of my private guns.

That is exactly how I do it. I find the current size of the port using the drill bits. Then I go up one step and drill it using a cordless drill. The drill bit is so small that it will self center as long as you are reasonably square to the bore. You need to mark the drill bit with tap to make sure you go all the way through one side without touching the other. Then I shoot the gun to see if it is reliable. If it is I might go up one more size to make sure it will never have an issue.

People ask about the burr and I tell them to shoot it and the burr will be gone. If they are really, really anal about it you can force a bullet down the bore until it covered the port. Then drill as usual. This will eliminate the burr. Afterwards just knock the bullet out of the bore. I have never had to do it because people are more scared of forcing a bullet down the bore than the burr.

********************************************

With it being a factory assembled upper I would not recommend altering it in any way. PSA seems like they are pretty good about taking care of problems. I would contact them for advice. Who knows they might have had a run of barrels that were drilled too small. Or they might give you the go ahead to drill the port without voiding any warranty.

Not with your brand but I have seen brand name carbine barrels with ports under .060" when you need at least .070" in most cases. Yours needs to be somewhere between .070" and .083" to be within "spec". And some guns like .070" while others, for whatever reason, NEED .083" to run.

In the mean time OP grab some ammo other than Tula or Federal and try it again. It may need a few hundred rounds to get things loosened up. Make sure you have the bolt pretty wet with lube. Not thin lube like Remoil but something a bit thicker. 30 weight synthetic seems to work pretty good. You could also try some grease or antiseize on the bolt head during the greak in. Antiseize seems to cushion things a bit as well as be a little slicker than grease itself.

And although some guns don't mind Tula some really do mind it. The problem with Tula is it is underpowered. Most American 55 grain stuff runs 3,000+ fps but Tula averages 2,850 fps. That 150 fps means there is less pressure at the port and that reduction can be enough to cause cyclins issues. Another issue that comes up is when the gun gets hot the chamber can get coated with the finish on the cases causing stuck cases. I have several guns tht don't mind Tula but it did take a little work to get them there.

Don't get discouraged, we you will get it figured out. And because you are local to me maybe we can meet up sometime and I can help you out.

Dolomite

[ANDERSON MEDIC]

Tomorrow is my next opportunity to take the thing out and im going to do as you reccomended. I've never had to break in an AR before, all the ones i've shot have had thousands of rounds through them already so I'm gonna get generous with the lube and take a few (hundred) shots with some PMC and lake city ammo tomorow. I thought maybe the problem may lie with the ammo being underpowered but wasnt sure. Naturally the last thing i want to do is be without my brand new toy for weeks, even though i too have heard that psa has a stellar track record with service after the sale. I will post tomorrow after range time and update. Thanks to all of you i am already very glad i joined this forum

[peejman]

How many rounds through it? A friend had a similar problem with a brand new upper and Tula ammo. It was simply not broken in yet. A little oil and few hundred rounds and it's worked fine since.

Edited September 10, 2012 by peejman

[ANDERSON MEDIC]

How many rounds through it? A friend had a similar problem with a brand new upper and Tula ammo. It was simply not broken in yet. A little oil and few hundred rounds and it's worked fine since.

About 400 so far. I thought i had the thing lubed well enough but as dolomite suggests i may have been using too light of a viscosity oil for the break in. I'll be trying something much thicker when i go test tomorrow with a few different ammo types. The curious thing is that the first time using tula it shot perfectly

[peejman]

About 400 so far. I thought i had the thing lubed well enough but as dolomite suggests i may have been using too light of a viscosity oil for the break in. I'll be trying something much thicker when i go test tomorrow with a few different ammo types. The curious thing is that the first time using tula it shot perfectly

I think that should be plenty of rounds for it to be broken in. If switch lubes doesn't work, I'd dig deeper into the gas system.

[ANDERSON MEDIC]

Ok so i took the rifle out today using a mix of pmc, AE black box and a few lake city rounds. Used 30w synthetic oil to lube the surfaces and I had none of the problems i was experiencing a few days ago. I guess panicked when my brand new rifle wasn't working properly! Thanks for all the input you guys saved me some time for sure. In the future I will know to use a thicker lubricant during the break in. And the best part is that i didn't have to tear into the gas system. Maybe in time I will be able to utilize the 200 or so tula rounds i still have left in my safe, but until then i will continue to run the more expensive american brass