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Thread: Uzi Build Not feeding Correctly

  1. #1
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    Uzi Build Not feeding Correctly

    Hi guys,

    I've got a couple builds i've been working on for while in spare time. They were smg parts kits converting to semi auto. I used 80% receivers and tig welded the front section of the smg receivers to the 80% and kept the smg trunnions. This was mostly RTG stuff using the jigs sold on that sight to align it all when welding. I did have to raise the blocking bars a slight bit to fit the jig and reweld. I'm using smg barrels along with the smg feedramps I believe from BWE. I'm using McKay semi auto bolts. Grip lowers I welded in a metal piece to block the selector from going to full auto. Anyways I've got an issue on both of these builds. They don't want to grab a round from the left (ejector side). I can start with a mag with the first round on the right of the mag and cock the gun and fire. It ejects that round, "grabs" the round from the left side and it actually puts the round into the chamber but infront of the extractor, so that the firing pin wont hit the primer. I tried a bolt out of my semi auto vector and same results. I have read everything I can find on this site. I've tried different mags and it does looks like some slightly push the right side bullet into the ejector but not bad at all. I'm somewhat leaning towards the chamfer of barrels are not very good and slowing down or blocking the bullet from smoothly entering the chamber. My biggest question is if anyone has any experience with this setup of using a smg barrel and feedramp along with a semi auto bolt? Are there issues with this setup I am not seeing? Thanks

  2. #2
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    If you look at the last picture the semi Uzi extractor sometimes needs to be slightly modified, I wish I could
    find the pic in our library but I can't. Also, someone can explain why this is done better than me but I have a suspicion that that is your problem.

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    Quote Originally Posted by kanewtervalve View Post


    If you look at the last picture the semi Uzi extractor sometimes needs to be slightly modified, I wish I could
    find the pic in our library but I can't. Also, someone can explain why this is done better than me but I have a suspicion that that is your problem.
    That could be, but I did try my bolt from my vector built semi auto and i just checked and the extractor is ground like your picture and I still had the problem. I would say everything needs better fitment like top cover etc but it all looks to be in spec. Because I had the same issue in two different receivers built the same I was mostly curious if me using a smg feed ramp and barrel with a semi bolt causes some issue I'm not aware of? Have any of you guys with smg's ever put a semi auto bolt in your gun? I don't know why you would but am just curious if it did run.

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    Sounds like your bolt is dragging on something.

    The closed bolt conversion removes the lower "feed lip" from the bolt so it is a "controlled feed" system instead of the "push feed" the open bolt uses. In the controlled feed it is like almost every pistol out there, the breechface hits the cartridge and shoves it forward. As it exits the magazine the nose enters the chamber and the rear of the case slides up the breechface and under the extractor, that is why the corner ism radiused. To allow easier entry.

    Push feed is used in the open bolt because the fixed firing pin would catch on the rising cartridge case if the breechface was flat. So the feedlip pushes the cartridge ahead of the bolt until it fully chambers, then the extractor snaps over the rim and into the extractor groove when it fully closes, also firing it because now the FP has hit the primer as well.

    The only difference between the extractors is the corner radiused, if the case is winding up fully chambered but the extractor isn't engaged and holding the bolt partially open, the problem would seem to be the bolt doesn't have enough force to snap the extractor over the case and something is preventing the case from sliding up the breechface.

    Have you tried the McKay bolts in your Vector?

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    Quote Originally Posted by slimshady View Post
    Sounds like your bolt is dragging on something.

    The closed bolt conversion removes the lower "feed lip" from the bolt so it is a "controlled feed" system instead of the "push feed" the open bolt uses. In the controlled feed it is like almost every pistol out there, the breechface hits the cartridge and shoves it forward. As it exits the magazine the nose enters the chamber and the rear of the case slides up the breechface and under the extractor, that is why the corner ism radiused. To allow easier entry.

    Push feed is used in the open bolt because the fixed firing pin would catch on the rising cartridge case if the breechface was flat. So the feedlip pushes the cartridge ahead of the bolt until it fully chambers, then the extractor snaps over the rim and into the extractor groove when it fully closes, also firing it because now the FP has hit the primer as well.

    The only difference between the extractors is the corner radiused, if the case is winding up fully chambered but the extractor isn't engaged and holding the bolt partially open, the problem would seem to be the bolt doesn't have enough force to snap the extractor over the case and something is preventing the case from sliding up the breechface.

    Have you tried the McKay bolts in your Vector?
    Thank you for the explanation. I think you might be right. The bolt being slowed down somewhere and as kanewtervalve pointed out with needing the ground lip on the extractor. I have not tried the McKay bolts on the Vector yet due to nasty weather today but will give that a test as well.

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    Load the magazine up so the first round is on the left side the problem side, remove your extractor, cause you don't need it to shoot off a round only to extract a round. Chamber and fire the gun, do this multiple times seeing if it feeds from both sides of the magazine.
    Class 3 shooters blow thier loads faster and with only 1 pull of the trigger

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    Quote Originally Posted by David Hineline View Post
    Load the magazine up so the first round is on the left side the problem side, remove your extractor, cause you don't need it to shoot off a round only to extract a round. Chamber and fire the gun, do this multiple times seeing if it feeds from both sides of the magazine.
    I believe I read that on here from a similar problem and meant to try that also. Thank you for the reminder

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    Quote Originally Posted by HK9mm223AK View Post
    I believe I read that on here from a similar problem and meant to try that also. Thank you for the reminder
    Also remove your top cover, remove your bolt assy and springs, load enough in the magazine that the first round is on the left side away from the ejection port. stick the loaded magazine in and see if the curvature of the underside of the riveted in ejector is pushing the round forward enough that it feeds too soon into the ramp.
    Class 3 shooters blow thier loads faster and with only 1 pull of the trigger

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    Getting home built uzi's to run properly can be extremely frustrating. I've built 8 of them using the same 80% channels as you. Every time I think I have the process down to a science I run into a problem that puzzles me for days and I've been so frustrated I would start to doubt my abilities only to sleep on the issue and the solution will just hit me after I've given up trying to diagnose it. I even bought a bullet trap just for testing my builds cause driving to a place to shoot just to test a small adjustment became too much of a pain in the ass. I've had to do some pretty drastic chamfering on all the aftermarket SMG barrels I've purchased to get them to feed properly and when encountering a problem similar to what your having I've had to go as far as adding a bunch of weld filler to the feedramp and then using jewelers files I would shape the feedramp to where it would work with that particular barrel and receiver combo. The amount of hours I've spent tweaking some of my builds to get them to work has been insane but in the end it was worth it. Just don't give up till you get her going is the best advice I could give you and if you get to a point where you're frustrated as hell and want to throw your build into the wall just put it down and come back to it later

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    @boomer1983 not sure if you ever got the issues on your latest build resolved but they sound similar to problems I encountered on two other UZIs.

    They both had feed or extraction issues based on which side the round came in from the mag.

    The first gun had a barrel who's breech face was milled wrong, the bullet would would hit the breech face (I think it was left side) and then get stuck into it because the breech face was razor sharp and cut the bullets jacket . This was clearly a barrel defect and solution was to sand and open up the breech face (careful not to touch the chamber).

    The second gun also had a barrel problem but rather the round would get wedged into the chamber far too deep. The problem there was due to a combination of problems, the receiver was very slightly out of alignment (and a press fixed it), the bolt head was allegidly "new" but so covered with foueling we couldn't get a round in until it was cleaned, and finally the barrels chamber was cut poorly (cant fix that).

    So have a look to make sure the barrel and bolt line up, welding can also shrink sheet metal and a bap weld seam To shorten it.

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