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Thread: Gas operated wonder 9?

  1. #21
    Gunco Member wrench1957's Avatar
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    Wow, I think I would check the mag spring first. Maybe put a block or try to shim it up for more push up on the mag follower. Cheap and easy experiment...
    Do it before it is too late!
    Proud member of the NRA,GOA and JPFO!!!
    And now GOCRA in MN!!!!

  2. #22
    Gunco Veteran Viper Dude's Avatar
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    Hello moleman,
    Yes, there are lots of bad Sten mags. They were a real problem for the Brits in WW-II. The mags are a copy of the German Schmeiser MP-28. The mags can be tuned-up to work with some care.

    VD

  3. #23
    gunco irregular moleman's Avatar
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    Viper Dude,
    I ended up bending the feed lips on the bad mag to match the mag that would feed. That seems to of fixed that mag. I tried it out and it feeds well now. I tried some of my 124gr lrn bullets with a 4.0gr charge of 321. That light load wouldn't cycle the action, but a 115gr fmj with 5.2gr of 231 (which is a starting load) cycles it just fine. The +p ranger ammo that I initially was using is noticably louder with a more energetic case ejection. I think I have a good cartridge load range that'll work the action. After the last gas port adjustment I was getting some bullet jacket in the gas system which was beginning to disappear. I had no copper in the gas system today, but I did have some lead dust stuck to the bolt tail where the key dumps the gas. If I'm going to work up a lead plinking load I think I'll have to debur the gas port first.

  4. #24
    Gunco Veteran [486]'s Avatar
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    Some .50BMG guys load turned steel bullets and report no abnormal barrel wear, I'm thinking something like that would deburr a gas port pretty well. Turn a few bullets right at .355, anneal them, load them up with a minimum load and see if it knocks the burrs off.

    Oh and remember that the gas key might restrict a bit of gas flow too, what with the bend in the gas channel. Might want to look at the insides of it and maybe port it out.

  5. #25
    Gunco Veteran Viper Dude's Avatar
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    Hello moleman,
    There must be a neet way to deburr the gas port on the inside of the 9mm barrel. A tiny dental burr ??? A Burrquick" tool ??? A stainless bore brush ??? A cable with some grinding compound ???

    VD

  6. #26
    gunco irregular moleman's Avatar
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    Viper Dude, Yes I was planning on using a small dental burr to do it! I got lazy the last time I drilled the gas port and just used a cordless drill instead of squaring it up in the mill. I think I have the gas port canted slightly. Before that there were no bullet shavings in the gas system and I enlarged it several times. Not a big deal and it seems fine now with fmj. I'm cheap though and like to shoot cast bullets. The gas port is around .108"-.110" so a slightly modified 1/8" shank dremmel bit would also work.

    [486], You're thinking this through! When I was working on the bolt I measured a gas key and the inside after the turn is around .122". The gas tube is a little under 1/8" (.118"ish) and is really the choke point for gas getting from the barrel to the bolt at the 90 degree turn in the gas block. The gas port is about as it should be and I don't think a bigger one would improve things. The upper seems to be working fine at starting loads all the way up to +p loads. I really don't want to overgas it more so it'll work with very light plinking loads. The upper worked fine with +P loads with a gas port of .100". I opened it up some so I could use slightly lighter loads than standard. The light plinking loads don't even break 900fps but work in some of my other 9mm builds so I'll just use them up and increase the powder till they work in this upper. It shouldn't take much.

  7. #27
    Gunco Veteran [486]'s Avatar
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    Maybe try drilling the gas hole after the bend in the key larger, then when making the turn the gas doesn't meet a restriction, because they probably just run a drill bit in from each end to make it, where the 2 holes meet [where the bend is] might not be full bore of either drill size.

    With a little googling [as I've never had an AR gas key off of the bolt carrier] I found a pic that shows the hole sizes. You might also want to take a small round file to the bolt carrier's gas hole and elongate it to the front to make for a more gradual radius there with the larger hole in the gas key.
    Ar 15 gas key image by Phil_in_CS on Photobucket

    Might get the nice light loads cycle. That'll save you a bit in powder if you shoot as much as I know making a 9mm AR would let me shoot! 8D

  8. #28
    gunco irregular moleman's Avatar
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    [486] The photo of the guys messed up carrier you linked to shows how the gas passage is angled in the photo and since it is an angled cut across the 1/8" hole the hole is actually .123"x.178" (still an 1/8" hole as far as a passage goes). I can stick an 1/8" bit through both ends of the gas key and see it in the hole of the other side which means the same funky .123"x.178" hole is inside the key as well (still a 1/8" passage as far as the gas goes). I measured a gas tube as I was pulling the .118" measurement from memory. It turns out its closer to .113"-.114" I just remembered it was smaller than 1/8" as I had to turn down some 1/8" drill rod to cap the gas tube so I could press it in. That means the passage in the key is still around .010" larger than the gas tube and probably .015" larger than the gas port.
    The 4gr of win 231 just isn't powerful enough to cycle the action. Not the guns fault it is a very light load. I typically load lead plinking rounds as slow as possible as it uses less powder and you don't get much leading to speak of compared to driving them faster. The 4gr loading is maybe going somewhere around 870fps and I was using as it cycled my sgn-9 and suomi, plus you get 1750 rounds out of a pound of powder occording to the math. Even if I go up to 4.6gr I'll still be right at a starting load for some of the reloading books I have and will get 1500+ rounds out of a pound of powder. I can live with that.
    Last edited by moleman; 01-05-2011 at 09:20 AM.

  9. #29
    Gunco Veteran muttman's Avatar
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    Moleman,
    One more nice build. At work now so look for a pm tomarow. Muttman.
    Last edited by muttman; 01-05-2011 at 10:15 PM. Reason: add to.

  10. #30
    gunco irregular moleman's Avatar
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    Quote Originally Posted by muttman View Post
    Moleman,
    One more nice build. At work now so look for a pm tomarow. Muttman.
    Thanks Muttman!

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