Franken 9mm AR FTF problems - Page 1

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[ARCHIVED THREAD] - Franken 9mm AR FTF problems

Posted: 6/12/2015 8:16:08 PM EDT

I can fire 2 rounds and the 3rd doesn't feed in to the chamber.

any suggestions of fixes to try?

Parts include Ebay Tactical Ambush barrel 8, PSA bolt, mag and buffer, 80% dedicated 9mm lower with Anderson parts kit Kak shockwave blade buffer tube.

Posted: 6/12/2015 8:33:49 PM EDT

[#1]

It could be magazine-to-barrel alignment, barrel positioning, feed ramp geometry or "other." By "doesn't feed into the chamber," what exactly do you mean? Does the third round go in some random direction and block the bolt, does it get jammed by an empty in the space above it, or something else? This is important: if it gets jammed by an empty, the problem is almost certainly your ejector not being lined up in the ejector groove in your bolt. If it's something else, there are specific things to look at.

Posted: 6/12/2015 9:13:02 PM EDT

[#2]

jams partly into the chamber, went and tried again, took a picture of the jam

Posted: 6/12/2015 10:00:40 PM EDT

[#3]

That looks like magazine alignment - specifically it looks like the magazine is a little low in the lower. That allows the first few rounds (which are under higher spring tension) to feed fairly well, but when the magazine isn't stuffed anymore, the spring doesn't push the rounds up quite high enough and eventually the top round in the magazine isn't high enough to go in straight enough.

Sadly, this is a problem for 80% lower makers.

Posted: 6/12/2015 10:31:20 PM EDT

[#4]

Are you sure the magazine is catching properly and is fully inserted? Not to sound like a lameo for asking...but..

Posted: 6/13/2015 1:27:31 AM EDT

[#5]

Are those Handloads? Looks like you need more crimp

Posted: 6/13/2015 7:09:11 AM EDT

[#6]

Double tap

Posted: 6/13/2015 7:16:42 AM EDT

[#7]

Could be magazine. I think the PSA magazine is an Uzi style meaning the rounds feed in flat. Maybe try an ASC magazine, they feed in with a slight up angle. That should help alignment problems a bit. And they are only like 12-15 bucks, so a cheap fix to try.

And just a comment, but your bolt looks really dry. Mine was tight when new and needed a good amount of juice to run smoothly. I would soak your bolt in lube except for the face.

What weight buffer spring are you using? If using standard carbine, try throwing a rifle spring in there. There is plenty of room and the extra couple coils will add a little more force to the forward bolt velocity. I would also run a bit of lube down the buffer spring and buffer edges to slick the tube out.

Posted: 6/13/2015 7:31:11 AM EDT

[#8]

Quote History

Quoted:
jams partly into the chamber, went and tried again, took a picture of the jam

<a href="http://s746.photobucket.com/user/riverfrontww/media/DSCN0057_1067x800.jpg.html" target="_blank">http://i746.photobucket.com/albums/xx103/riverfrontww/DSCN0057_1067x800.jpg</a>

View Quote

Take a picture with the upper OFF. Include the lower with mag-well adapter, magazine and (at least) one round!

ETA: From the picture, I think the mag-well adapter might be a bit LOW. From the picture, it looks like the feed-ramps are too low. I'll get a pic of my setup later today. Unfortunately I got rid of my 9mm dedicated lowers...so now I have mag-well adapters only....but the geometry should be the same.

Try this:

With the upper installed (and mag-well adapter in place). After releasing a SMALL amount of tension from the screws, pull the adapter up the mag-well until it comes to a stop (it might move a mil or two). While holding pressure, tighten the screw/s up. Make sure you mag works correctly.

That is what happens with 5hrs of sleep ;)

Posted: 6/13/2015 9:07:06 AM EDT

[#9]

The transition from the feed cone cut in the breech face is too angular, I'm betting you have a half moon cut scored into the case when it hangs.

Posted: 6/13/2015 9:37:43 AM EDT

[#10]

First off thanks to everyone for all the help with my problem I will try to answer all the questions.

mag is fully seated and retained

Factory loaded ammo Winchester Ranger 124 grain

Using a PSA 9mm buffer, I will try more lube on the bolt later today, going to order a couple different mags from midway today (right down the road) and pick up some different ammo as well.

I'm pretty sure i'm getting the half moon cut as well here is a picture of the last round that was jammed.

more pictures below will hopefully answer the rest of the questions

Posted: 6/13/2015 10:03:49 AM EDT

[#11]

Decided to polish the feed ramp, figure it couldn't hurt, then lubed the heck out the bolt and upper. Loaded up 10 rounds first 2 bang bang 3rd round click, looked at the ejection port and its the same jam.

Posted: 6/13/2015 1:10:19 PM EDT

[#12]

Your feed ramp is too low. It lines up with the second round in the magazine - it's essentially not doing anything for you. So when the first and second rounds have left the magazine and the spring tension is a little bit lower, there isn't enough upward push to line up the third round - and you get this failure.

Posted: 6/13/2015 1:54:51 PM EDT

[#13]

Feed ramp might be low, but it seems to be about the same as mine(Black Creek dedicated 9). But it does look like your magazine may be a little high. Itlooks like the seam on the rear of your mag is pushing the bolt catch up. Is it? If so your mag or mag catch may be the issue.

I went at looked at my mags and I had it backwards, the ASC feed flat in, the Uzi have a slight upwards angle at the front. Still probably worth a shot to try a different brand magazine.

Posted: 6/13/2015 3:42:19 PM EDT

[#14]

I got it running. Just rounded the transition between the feed cone and the chamber. MadMachinist nailed it with the half moon cut to the jammed rounds.
Figured I didn't have anything to lose modifying the Ebay barrel, rounded the transition a little then polished it. reassembled the upper and ran 25 rounds thru it flawlessly twice.

before picture

some after pictures if I remember I will take some more when the final hand guard gets here. Looks lopsided but its mostly the angle of the camera.

Posted: 6/13/2015 3:54:51 PM EDT

[#15]

Excellent......

love it when Franken guns run..........

Posted: 7/4/2015 5:10:07 PM EDT

[#16]

Perfect timing on this thread. I just got my 9mm finished, and it's having the same issue. Looks my Dremel and I will be working on that lip.

Posted: 7/4/2015 8:48:06 PM EDT

[#17]

Might be safer idea to just touch the edge with a chamfer tool if you reload..

Posted: 7/4/2015 10:37:36 PM EDT

[#18]

Good idea. Now to find mine. It's around here somewhere.

Posted: 7/5/2015 12:24:57 AM EDT

[#19]

I have the same tactical ambush 8" barrel from ebay with PSA mags and AMM mag block and had the same feeding issue. Adjusting the mag block by lowering the front a tad bit took care of it.

Posted: 8/23/2015 11:08:15 AM EDT

[#20]

I decided not to try fixing my barrel on my own. Sent it off to Mad-Machinist instead. He did a great job and had quick turnaround time.

Finally tested it yesterday, and it's running great. Nice and smooth; no more jams.

Posted: 8/23/2015 11:22:41 AM EDT

[#21]

Funny, my reliability improved with the 6" tactical ambush barrel. Below are my build specs.

RRA upper, buffer, and bolt
QC10 lower
ASC magazines
Tactical Ambush 6" ebay barrel

[ARCHIVED THREAD] - Franken 9mm AR FTF problems

AR-15 » Rimfire and Pistol Calibers

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