AR-9 Pistol Help

KnotRight

KnotRight

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I built an AR-9 pistol and it has a Scorpion can on the end. I know gas has nothing to do with the operation of this gun. I was having a problem with some light primer strikes (I reload all my ammo for the past 35 years) so I changed the buffer to an H3 and put a heavier hammer spring in the gun. Took it to the range today and still having issues with light strikes. I did put those rounds back in the gun and they would fire.
I am thinking about putting in another trigger group and taking apart the bolt to see if there is anything around the firing pin. Any ideas?
 
I have been reloading almost as long as you, so I almost hate to suggest it may be the ammo. The fact that the rounds fired on a second attempt usually means the primers were not seated fully. The first firing pin strike is enough to seat it but doesn't transfer enough energy to ignite it. I assume you were using a tried and trusted load.
I bought a cheap 9mm AR barrel once. The chamber was cut just enough too deep that the cartridges would fall into it and be slightly out of the reach of the firing pin. Light strikes resulted.
The fact that your ammo fired on a subsequent attempt kind of rules this second idea out. Otherwise, I would do exactly what you have done to troubleshoot. Interested in what you find out.
 
Lunkhead said:
I have been reloading almost as long as you, so I almost hate to suggest it may be the ammo. The fact that the rounds fired on a second attempt usually means the primers were not seated fully. The first firing pin strike is enough to seat it but doesn't transfer enough energy to ignite it. I assume you were using a tried and trusted load.
I bought a cheap 9mm AR barrel once. The chamber was cut just enough too deep that the cartridges would fall into it and be slightly out of the reach of the firing pin. Light strikes resulted.
The fact that your ammo fired on a subsequent attempt kind of rules this second idea out. Otherwise, I would do exactly what you have done to troubleshoot. Interested in what you find out.
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Just ordered a new firing pin and spring. Going to take apart the bolt and make sure that there is no $hit in the way of the firing pin. Also, order a 3 pack of Wolf springs. I might have 4 or 5 milspec trigger groups around here and next time I go to the range I will bring a couple of them
 
Look at the hammer. I had a build kit that wasn't supposed to, but had a lightweight hammer In The pack. Same scenario as you. Changed hammers and problems gone.
 
Be careful when you take apart BCG as the firing pin has a spring, unlike an AR, which as you know has a floating firing pin.
 
I just took apart the bolt and cleaned the firing pin. The whole bolt was not very dirty. And there is a big difference between an AR-15 and AR-9 firing pin. After watching a couple videos, I primed a couple cases and let the slide down easy. It was striking the primer the way it was on the range, very light and busting the primer. If I released the bolt at full speed the bolt did go all the way in and popped the primer. Here is a picture of the 2 firing pins and the barrel extension.
20210817_164354.jpg20210817_165935.jpg
 
JRHorne said:
What brand BCG, what brand trigger, and what brand barrel?
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BCG - PSA
Barrel - I think Ballistic Advantage
Trigger - Milspec with all surfaces polished to a mirror finish

I figured out that the bolt was not going all the way forward when I had light strikes. I cleaned the chamber and bolt really good tonight. I just looked at the loads that I was shooting, and they should be close to max velocity (4.4 grn of Bullseye under a 124 RMR RN bullet).
 
Will the trigger keep the bolt from going into battery sometimes? That is what I figured out was happening. After watching some videos, I tried that they were showing and while at the range, when I had light strikes and pulled back the bolts, the round was not being held by the extractor. I had to turn the gun sideways to get the round out of the lower.
 
Ok, I think that I am on the right track. I just ordered a RED buffer spring from sringco.com. I figured that I do not have enough forward motion on the bolt to get it in battery. While talking to the rep at Springco, he asked what buffer I was using, and I told him it was a H-3. Then he asked if it was the "Standard" length for ARs. Yes, it is, then he said that it needs to use an AR-9 buffer which is 3/4 of an inch longer. Now I am over my head. He gave me a website to order a buffer for the AR-9 that has a longer head space. He also said the I could build a 3/4-inch spacer and use the standard-length buffer. If I get one made, make sure that I have a fender washer on the end of the spacer. Why? Again, I am in over my head.
 
KnotRight said:
Ok, I think that I am on the right track. I just ordered a RED buffer spring from sringco.com. I figured that I do not have enough forward motion on the bolt to get it in battery. While talking to the rep at Springco, he asked what buffer I was using, and I told him it was a H-3. Then he asked if it was the "Standard" length for ARs. Yes, it is, then he said that it needs to use an AR-9 buffer which is 3/4 of an inch longer. Now I am over my head. He gave me a website to order a buffer for the AR-9 that has a longer head space. He also said the I could build a 3/4-inch spacer and use the standard-length buffer. If I get one made, make sure that I have a fender washer on the end of the spacer. Why? Again, I am in over my head.
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The washes is probably to keep the spacer from slipping into the spring
 
Johnny said:
For testing purposes, I have read that a stack of quarters of the dimension you seek will work if you stick them in first.
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That is what the guy at Sprinco.com said use if I did not have anyone that could turn me the space to the correct size on a lay. Now i am looking into an AR-9 buffer that has the extra 3/4" on the spring side of the buffer. This has been a learning process.
 
I think you're on the right track with the buffer. The one I had in my AR9 was a good bit heavier than the AR15 buffer. I want to say it was 5.8 oz. H3 is close to that I think? The spring was different as well. The quarters in the end of the buffer are to limit rearward travel of the bolt to mitigate breaking the bolt stop during LRBHO. If LRBHO even works on yours. I ended up with three in mine.

I ended up selling my 9mm upper. I got sick of tinkering with it. It was fun for a little while though.
 
Not sure if mentioned: make very sure your hammer spring is not upside down. Common install mistake and causes lite strikes.

Get a stack on quarters and put them in tube first. I use a 9mm multi stage buffer, and use the quarters to short stroke the bolt.
 
Rode by PSA today and remembered that they had an 8 oz extended 9 MM buffer Picked it up and going to try it with the current buffer spring. Hoping with the extra length in the buffer, I will not need any spacers. When the SprinCo red spring gets here I will change out the one in there and make another trip to the range. I am starting to feel like I am testing a gun for the government.9mm bolt.jpg
 
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