need help with 9mm ar

tommy gunn · Feb 29, 2016

I took my newly built 9mm ar pistol out for its first test fire and it was a jam-o-matic. I couldn't get thru a 17 round mag without jamming a dozen times. Now this may be all my fault I don't know. I didn't put the buffer spacer in and forgot it on my work bench. Would this cause the problem? I was using brand new magpul glock mags cause that was all I had. I put the spacer back in when I got home but I can't go test it for another week. If anyone has any ideas I'm open for suggestions. Thanks in advance.

tommy gunn · Feb 29, 2016

Could a mod please move this to gunsmithing? I just realized I put it in the wrong place. Thank you.

pwoolford · Feb 29, 2016

Can you describe the jams you were having? Was the spent round extracting completely? Were you getting double feeds? I'd start with that spacer and some different mags. I'd also bring along a different buffer spring and buffer. Which buffer are you running?

tommy gunn · Feb 29, 2016

pwoolford said:
Can you describe the jams you were having? Was the spent round extracting completely? Were you getting double feeds? I'd start with that spacer and some different mags. I'd also bring along a different buffer spring and buffer. Which buffer are you running?

The spent shell wasn't coming all the way out while the next round would load so it was getting jammed between the bullet and the top of the receiver. The spring I don't know it was listed in the 9mm section on 9mm ar.com. Same with the buffer. It has no name or logo on it.

pwoolford · Feb 29, 2016

Does the bolt lock back after the last round? Assuming your lower does that. What ammo were you shooting?

tommy gunn · Feb 29, 2016

pwoolford said:
Does the bolt lock back after the last round? Assuming your lower does that. What ammo were you shooting?

I don't know if it locks back I never made it thru a full mag with out the jammin. Ammo was winchester from walmart. I can give the specifics when I get home from work.

tommy gunn · Feb 29, 2016

Ok ammo is winchester 115 grain fmj. The buffer I'm not sure. My scale only goes up to 100 grams. The buffer weighs more than that much cause it errors out my scale. I did notice the mags were tuff to seat when fully loaded. Had to smack em in there. With one ore two rounds less the fit fine.

ashershapiro · Feb 29, 2016

With a 9mm AR, the problems are usually with the buffer or the mags. If you have the appropriate 9mm buffer and good mags, then you should be fine. I would add a wolf extra power buffer spring as well.

9mm builds take need very specific parts, not as much room for error as a regular AR.

Chevyman85 · Feb 29, 2016

tommy gunn said:
Ok ammo is winchester 115 grain fmj. The buffer I'm not sure. My scale only goes up to 100 grams. The buffer weighs more than that much cause it errors out my scale. I did notice the mags were tuff to seat when fully loaded. Had to smack em in there. With one ore two rounds less the fit fine.

When I built mine it jammed a lot at first as well. I was also using WWB 115gr ammo and narrowed the problem down to being the WWB was crap. Using FED American Eagle 115gr and 147gr I have no problems.

Obliviously my gun I'm sure isn't built identical to yours so there could still be other contributing factors to your problems. However I would try changing ammo and see if that helps. Some guns are picky, I have a few that are.

lee2 · Feb 29, 2016

I would try a better ammo first.

j_h_smith · Feb 29, 2016

147 gr is all I shoot. You will find it will help with reliability. Also make sure you lather that thing with a good lubricant. Remember it's a blowback rifle, lub is your friend.

How many mags did you try? Like others have said, it could be the mags too. I have heard of some folks having problems with Magpul Glock mags.

Good Luck!

Jmorrismetal · Mar 1, 2016

You need a lot more information, "glock mags" says your not using "normal" 9mm AR "stuff".

What upper, lower. We know the ammo, do you have any factory glock mags.

Lots of things can be wrong but it could also only be (and likely) a single variable solve the problem.

tommy gunn · Mar 1, 2016

No I don't have any factory glock mags. As I said all I have is 2 magpul glock mags. The lower is a joe bobs dedicated 9mm lower that takes glock mags.

Upper is a joe bobs spartan upper
Barrel yankee hill 5.5"
Bgc new fronteir glock ramped bolt (so I didn't have to change hammers)
Lpk standard spikes kit

I just haven't had time to make a trip to free america to buy any factory mags. I refuse to buy a nuetered mag in maryland. I'm definately gonna have to before the next test run.

pwoolford · Mar 1, 2016

I don't believe the JB Spartan lower locks back so disregard that. As others suggested definitely try different mags and ammo first. Not sure how far you are from Freestate but I go there weekly if you want to try some Glock mags.

tommy gunn · Mar 14, 2016

Well I put the buffer spacer in the gun. I made a trip to big dog outfitters and grabed several different mags. I made a mount for my umbrella to clamp it to the table at myrtle grove. I loaded up and drove down there this morning. Got there and remebered after looking at the sign they don't open till 1pm on mondays. This was at 9am. I felt real dumb. Then I ran into Dan and he tells me they will be closed all day cause they are having some big meeting down there today. People from anappolis, engineers, neighbors and a few otheres. Could be good could be bad who knows. I guess ill try again tomarrow.

44man · Mar 14, 2016

tommy gunn said:
Well I put the buffer spacer in the gun. I made a trip to big dog outfitters and grabed several different mags. I made a mount for my umbrella to clamp it to the table at myrtle grove. I loaded up and drove down there this morning. Got there and remebered after looking at the sign they don't open till 1pm on mondays. This was at 9am. I felt real dumb. Then I ran into Dan and he tells me they will be closed all day cause they are having some big meeting down there today. People from anappolis, engineers, neighbors and a few otheres. Could be good could be bad who knows. I guess ill try again tomarrow.

the meeting was a pre bid meting about replacing some of the baffels. there was some bitching from a guy about the holes in the wooden baffle above the berm. apparently they say people are shooting prone even though they are told not to so they can shoot under all the baffels and above the berm into that last wooden backstop and above it and I expect those bullets are landing somewhere.

tommy gunn · Mar 14, 2016

44man said:
the meeting was a pre bid meting about replacing some of the baffels. there was some bitching from a guy about the holes in the wooden baffle above the berm. apparently they say people are shooting prone even though they are told not to so they can shoot under all the baffels and above the berm into that last wooden backstop and above it and I expect those bullets are landing somewhere.

Ya dan also said they were finding evidence and getting complaints of people shooting after hours too. He mentioned something about people calling dnr about complaints of unsafe behavior but I didn't quite catch what he said. I have no problem with that part after all see something say something.

44man · Mar 14, 2016

it took me a few minutes to figure out exactly how they could be shooting that backstop on top of that berm. either prone from below or from above or the sides, either way is not safe for anyone down rage behind there. and man there are a lot of holes in the baffles also and the steel plates in front of the posts are all but destroyed. either people just plain cant shoot or they are targeting the posts and baffels and shooting over the berm on purpose.

tommy gunn · Mar 18, 2016

Ok now I'm really at a loss. I went to test fire the 9mm build today and all kinds of problems happened. Still a jam o-matic with different mags and ammo. Then this happened. Had a bullet blow up in my face. The primer went of and blew the powder and the back of the bullet out the back.

So now I got the case with the bullet stuck in the barrel and the back of the bullet stuck in the bolt face. I'm at a loss I don't know what to do now.

Sent from my SCH-S968C using Tapatalk

j_h_smith · Mar 18, 2016

Is the barrel clear? Looks like maybe a squib round and then the next round blew up.
Take that firearm to a qualified gunsmith. No backyard gunsmith, someone that knows an AR as well as the back of his hand. I'm glad you weren't hurt.

need help with 9mm ar

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