AR9 Pistol FTE or FTF

Hi all, hoping the braintrust has some ideas.

Recently purchased a kit similar to the one linked. The differences in my kit and the one linked are purely aesthetic. KAK brace, standard grip, etc.

I have it on a known working glock lower. I am using both factory ammo and reloads for variety in 33 round glock mags. No matter what brand or reload I use, about every 10 rounds or so there is a FTF or FTE or a combination of the two. (see pics)

Standard carbine buffer spring and 5.5 oz buffer.

When it works, it's great. But, you never know when it will jam. Any thoughts or advice on reliability would be much appreciated.

https://palmettostatearmory.com/psa-gen4-4-9mm-5-lightweight-m-lok-railed-moe-sba3-pistol-kit.html

I would love to have some useful input but my knowledge of such things is limited to "Damn it Jim"

Sent from my LM-X320 using Tapatalk

I would recommend a Wolff extra power spring and at least an 8 oz. buffer. Using a standard carbine spring and lighter buffer could result in an out of battery detonation.

Might also try smoothing any sharp edges at the chamber mouth to improve reliability. Liberal lubrication is also a good idea.

Love my AR-9 pistol.

Knowing what lower you're using would be helpful.

GuitarmanNick said:

I would recommend a Wolff extra power spring and at least an 8 oz. buffer. Using a standard carbine spring and lighter buffer could result in an out of battery detonation.

Click to expand...

This isn't going to solve the OP's problem, and, frankly, super heavy buffers are not necessary in every AR-9 build, especially with shorter barrels. I will concur that 5.5oz is on the light side. I have used the FM9 buffer with a lot of success, and that's only about 6.8oz.

OP, I had a very similar kit from PSA, and the bolt and barrel were just trash. I had to replace the bolt because of the ejection problems you cited, and the barrel got dumped because of the stupid short lede it had that prevented me from using my reloads (which did not have a terribly long OAL to begin with). I wound up using the FM9 bolt and JP Supermatch barrel, and it's run like a charm ever since. Have since switched to the Taccom ESSB and 3-stage buffer system to get some of that short stroke action going on.

jimboman2000 said:

Hi all, hoping the braintrust has some ideas.

Recently purchased a kit similar to the one linked. The differences in my kit and the one linked are purely aesthetic. KAK brace, standard grip, etc.

I have it on a known working glock lower. I am using both factory ammo and reloads for variety in 33 round glock mags. No matter what brand or reload I use, about every 10 rounds or so there is a FTF or FTE or a combination of the two. (see pics)

Standard carbine buffer spring and 5.5 oz buffer.

When it works, it's great. But, you never know when it will jam. Any thoughts or advice on reliability would be much appreciated.

https://palmettostatearmory.com/psa-gen4-4-9mm-5-lightweight-m-lok-railed-moe-sba3-pistol-kit.html

Click to expand...

Are you shooting fast, double taps when it happens?

Hi all, thanks for the responses. After some digging on the PSA website, it appears that there is a known extractor problem. Apparently certain bcg's they use are more likely to fail. Several people commented that they got PSA to replace them. I am going that route, but in this current time it will take 3 to 5 days to get a response. I took a bcg out of another 9mm build and used it in this one and it ran well. So, it appears that I got some "bottom of the barrel" parts or something.

Regarding the buffer and spring, I used what they supplied.

All of this is happened during normal shooting, nothing fancy. No double taps, rapid firing or the like.

GuitarmanNick said:

I would recommend a Wolff extra power spring and at least an 8 oz. buffer. Using a standard carbine spring and lighter buffer could result in an out of battery detonation.

Might also try smoothing any sharp edges at the chamber mouth to improve reliability. Liberal lubrication is also a good idea.

Love my AR-9 pistol.

Click to expand...

+1 on the above. Heavier spring and buffer and lubrication.

OP, if you replace your bolt, absolutely get one with the M16/AR-15 style extractor. They are oodles better than the old-style ones found on other 9mm bolts.

I use a 7 oz buffer and a very stiff buffer spring; basically for a 308.

erwos said:

OP, if you replace your bolt, absolutely get one with the M16/AR-15 style extractor. They are oodles better than the old-style ones found on other 9mm bolts.

Click to expand...

If that's a PSA bolt, it's likely the problem. I have two AR 9 with standard AR 9 bolts and have no problems from them. BUT, you probably have zillions more rounds through your guns so I give you the credit due.

outrider58 said:

If that's a PSA bolt, it's likely the problem. I have two AR 9 with standard AR 9 bolts and have no problems from them. BUT, you probably have zillions more rounds through your guns so I give you the credit due.

Click to expand...

I think so as well. Awaiting response from PSA, about as long as ship time from what I understand.

calicojack said:

I use a 7 oz buffer and a very stiff buffer spring; basically for a 308.

Click to expand...

I'll go there next after I hear back from PSA.

Check this post for some recommendations. https://www.mdshooters.com/showpost.php?p=5836311&postcount=6

jimboman2000 said:

Hi all, thanks for the responses. After some digging on the PSA website, it appears that there is a known extractor problem. Apparently certain bcg's they use are more likely to fail. Several people commented that they got PSA to replace them. I am going that route, but in this current time it will take 3 to 5 days to get a response. I took a bcg out of another 9mm build and used it in this one and it ran well. So, it appears that I got some "bottom of the barrel" parts or something.

Regarding the buffer and spring, I used what they supplied.

All of this is happened during normal shooting, nothing fancy. No double taps, rapid firing or the like.

Click to expand...

Well it's good that PSA is honoring their work. Hopefully it all works out.


.

I had the same issue on mine. It's that the throat of the barrel is too tight to feed the nose of the bullet in properly. That's why you get the ftf because the bullet went nose up on battery hitting the barrel throat like a wall vs a funnel, and the fte because the case was stuck in the tight barrel to be ejected. I bought barrels from Macon Armory that the feed ramp have more of a cone shape to help guide the bullet into position. I would actually start there as I had the same issue and that solved it, three times. https://maconarmory.com/products/copy-of-ar-45-barrel-blowback-only

Joe Blow said:

I had the same issue on mine. It's that the throat of the barrel is too tight to feed the nose of the bullet in properly. That's why you get the ftf because the bullet went nose up on battery hitting the barrel throat like a wall vs a funnel, and the fte because the case was stuck in the tight barrel to be ejected. I bought barrels from Macon Armory that the feed ramp have more of a cone shape to help guide the bullet into position. I would actually start there as I had the same issue and that solved it, three times. https://maconarmory.com/products/copy-of-ar-45-barrel-blowback-only

Click to expand...

I would be somewhat surprised if this was causing his FTEs if he's using factory ammo. Where the problems tend to come in is with reloaded ammo, which is often using lengths and bullet profiles much more likely to hit the rifling without a more substantial throat. In any event, he can test this by simply slowly chambering a round... if there's resistance, he has insufficient throat. I had a reload (with a crimp, even) which had a bullet get stuck in the rifling during manual extraction during a match... ugh, screw PSA.

The most likely explanation is that he's got the 1911-style extractor PSA bolt, which is not nearly as good as the new AR-style extractor bolts.

Seriously, let this thread be a warning: the PSA 9mm kits look much better than they often function.

I have seen ejection issues like this if the ejector is not at the right location. a lot of the glock mag lowers have the ejector mounted with 2 set screws. the height must be set for proper ejection.

Most of the "expertise" in building a good reliable blowback AR9 comes down to a few things. The ejector usually needs a little tuning, it should be really close to contacting the inside corner of the slot cut in the bolt, placing it as far inward on the case as possible without binding, this gives the best ejection. The extractor needs to be burr/defect free, polishing can help, and bolts that use AR15 extractors need a good spring / o-rings. It has to be able to freely snap over the rim as a case is chambered, and to hold in place as the case violently blows back against the bolt. If it has a LRBHO at all, they can be a PITA to get to work, and usually takes some work to get the bolt catch spring vs mag spring and the linkage in between moving freely and balanced so it works without the catch engaging inadvertently. The carrier / buffer / spring choice is probably the most critical, and there are a few considerations like running a suppressor, barrel length, and ammo choices. bolt/buffer mass more than anything controls cycling speed, and timing, the reason most are using heavy buffers, but the weight needed will vary.

being 9mm is shorter than 5.56, you don't need as much bolt travel, limiting it by about 3/4" with a spacer or longer buffer will reduce recoil and chambering force a bit, while speeding up the cycle speed. You can reduce bolt travel 1" or more than normal, but that is around the point where you might not have enough travel to reset the trigger, and it takes a special short-stroke bolt for the bolt catch to work. Spring rates don't really do as much to change cycle speed, but they can affect both recoil and chambering force. I like to run a heavy buffer with sliding weights(smoother recoil and less bounce than solid buffers) and a standard carbine spring) Have had great luck with the Kak 10oz buffer, the mass seems to kinda self adjust with ammo, functions fine with my light PCC match loads and with hot +p loads little gas /port bark when running suppressed, cycles quick enough, soft recoil, nice light charging handle pull. I've used Tubb ar15 springs with this buffer too with good luck. Lighter buffers and heavier springs have a bit harsher/quicker recoil, and they can get obnoxious with hot ammo. Once you get under 6oz or so you can get reliability problems especially if using solid buffers, there can be noticeable bolt bounce and wear between the bolt and chamber smashing into each other.