need help with 9mm ar

OrbitalEllipses · Mar 18, 2016

Holy hell.

44man · Mar 18, 2016

as clandestine, I believe he said once that some 9mm ars tended to fire before the bcg was closed into battery.

best have someone VERY knowledgeable look at that gun asap.

tommy gunn · Mar 18, 2016

Ya that's my plan. There wasn't a squib in the barrel. That was the only round in the mag.

DutchV · Mar 18, 2016

I'm going to bet that your feed ramp needs some polishing, since that seems to be typical of the 9mm builds. Not sure that's going to solve the whole problem, though.

jimbobborg · Mar 19, 2016

Are you using a standard M4 upper and lower receiver? I don't see the block on the upper that you normally see on a 9mm upper. Also, your picture looks like what happened to my 6.8 upper when I had a high primer on one round and it slam fired, which caused a broken BCG for me and I had to replace the upper receiver and BCG.

clandestine · Mar 19, 2016

Who assembled the upper? Was it checked with a headspace gauge? A loose barrel, bad headspace or a FCG that drops the hammer prematurely can cause what I see. Insufficient buffer weight or action spring tension can also cause premature bolt opening which can also cause what I see. This can also show itself in extraction problems. Seeing the fired brass would tell me more.

That projectile will have to be pressed out and then some cerrosafe to get out the casing. The extractor and firing pin on that bolt may be toast.

The ejection issues are likely ejector related. Ejector problems are so common with glock mag ARs that custom ejectors are becoming a thing.

tommy gunn · Mar 19, 2016

The bullet came right out without any effort. I used a dow rod and barely pushed it and it fell right out.

clandestine · Mar 19, 2016

tommy gunn said:
The bullet came right out without any effort. I used a dow rod and barely pushed it and it fell right out.

Thats good. One less thing to resolve.

To get the casing out you plug the front of the chamber with a cleaning patch and pour cerrosafe in the chamber from the breach. Let it cool and tap the casing out.

Here is the idea:
http://www.mdshooters.com/showthread.php?t=191058

Long1MD · Mar 19, 2016

Scrap it and spend ur money on an H-bar or AR pistol in 556. Never understood the 9mm AR nonsense

clandestine · Mar 19, 2016

Long1MD said:
Scrap it and spend ur money on an H-bar or AR pistol in 556. Never understood the 9mm AR nonsense

Yeah, its silly.

tommy gunn · Mar 19, 2016

Long1MD said:
Scrap it and spend ur money on an H-bar or AR pistol in 556. Never understood the 9mm AR nonsense

I already got 2 5.56 pistols and a 5.56 rifle. I just wanted something different. Besides I got 3 pre-ban lowers so I'm not too worried about the hbar thing. 9mm is a range toy anyways. I just hate when my toys are broken and I have to figure out how to fix em.

tommy gunn · Mar 19, 2016

clandestine said:
Thats good. One less thing to resolve.

To get the casing out you plug the front of the chamber with a cleaning patch and pour cerrosafe in the chamber from the breach. Let it cool and tap the casing out.

Here is the idea:
http://www.mdshooters.com/showthread.php?t=191058

How far down the front of the chamber should I go? Its a 5.5" barrel I don't fill the whole barrel do I? That's problibly gonna come out as a stupid question.

clandestine · Mar 19, 2016

tommy gunn said:
How far down the front of the chamber should I go? Its a 5.5" barrel I don't fill the whole barrel do I? That's probably gonna come out as a stupid question.

Not stupid at all. I would put the patch at the front of the chamber so only the chamber gets filled (Dont want the cerrosafe to form into the rifling).

tommy gunn · Mar 19, 2016

clandestine said:
Not stupid at all. I would put the patch at the front of the chamber so only the chamber gets filled (Dont want the cerrosafe to form into the rifling).

Well thankfully I don't have to go that route. I took the whole thing apart and using a large copper bore brush I got it out. I went into the back of the casing and twisted the brush till it was tight then pulled hard. It came out. So now all peices of the shell are out. My plan is to put it back together and have someone look at it or should I just leave it apart?

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clandestine · Mar 19, 2016

tommy gunn said:
Well thankfully I don't have to go that route. I took the whole thing apart and using a large copper bore brush I got it out. I went into the back of the casing and twisted the brush till it was tight then pulled hard. It came out. So now all peices of the shell are out. My plan is to put it back together and have someone look at it or should I just leave it apart?

Sent from my SCH-S968C using Tapatalk

Excellent work!

Its hard to say if anything was damaged. At a minimum a set of Headspace gauges should be used to ensure the headspace is not too short or excessive.

From there check the bolt group and make sure the firing pin isnt bent or sticking forward.

If you take a live round and put it into the bolt face does the extractor hold the round well if you shake the bolt? The extractor may have a bad hook or no tension. They tension like a 1911 extractor and can be adjusted.

I would thoroughly test the fire control group too and make sure the FCG is not binding or following.

While the barrel and handguard is off, it is a great time to check ejector position. Put the upper on the gun with the charging handle and bolt installed. Look from the front (No barrel or handguard) and slowly retract the bolt. you want to see where the ejector sits in the slot cut into the bolt. it needs to be as high and toward the ejection port as allowed without binding on the bolt. It requires slight bending with smooth jaw pliers. You can also test to see if the magazine is contacting the bolt causing cycling issues at the same time.

I hope these things make sense.

What buffer and spring are you using?

tommy gunn · Mar 19, 2016

I honestly don't know the buffer and spring. I got it from 9mmar.com. I was gonna order a wolf spring when I get paid and try a heavier buffer. I tried to weigh my buffer but my scale only goes up to 100 grams. Which only comes out to roughly 3.5 ounces. It kept erroring out my scale so I guess it weighs more than that.

j_h_smith · Mar 19, 2016

Long1MD said:
Scrap it and spend ur money on an H-bar or AR pistol in 556. Never understood the 9mm AR nonsense

Sorry, I've got 2 9mm AR pistols and a carbine. All of mine work fine after a little tweaking. I'm no expert, but I'd rather have my 9mm in a CQB than the 55.6 carbine. But that's just one man's opinion.

j_h_smith · Mar 19, 2016

Just curious, what ammo were you using?

clandestine · Mar 19, 2016

tommy gunn said:
I honestly don't know the buffer and spring. I got it from 9mmar.com. I was gonna order a wolf spring when I get paid and try a heavier buffer. I tried to weigh my buffer but my scale only goes up to 100 grams. Which only comes out to roughly 3.5 ounces. It kept erroring out my scale so I guess it weighs more than that.

Can you show me a picture of the buffer?

I would consider a Tubb AR15 Flat Wire Spring if you can afford it. I cant tell you how many malfunctioning AR's in 9mm that spring has fixed, even XP springs dont perform as well.

tommy gunn · Mar 19, 2016

clandestine said:
Can you show me a picture of the buffer?

I would consider a Tubb AR15 Flat Wire Spring if you can afford it. I cant tell you how many malfunctioning AR's in 9mm that spring has fixed, even XP springs dont perform as well.

Its the one one the right. I sat it next to my spikes t2 out of my rifle for a comparison.

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need help with 9mm ar

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