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Gas operated wonder 9?

5K views 40 replies 10 participants last post by  vz58 
#1 · (Edited)
I've been taling about building a 9mm direct impingement upper since this past april and have been gathering parts since early summer. Over the past two weeks I've managed to make some progress on the build.
I started with: a 9mm blank; a $10 barrel extension from CDNN; a spare carrier and upper I've had for years; A set of used USGI bolts off of gunbroker; and a Caterpilliar diesel engine nut 13/16"-16tpi.
The barrel blank I started with was one of the .800" blanks that have been floating around for the past few years. This barrel is too thin to turn a shoulder into for the barrel extension to rest against. I decided to used a savage style locknut to solve this problem. An internet search turned up Catapilliar diesel engine grade 8 nuts for about $1.50 each so I got several.
After short chambering the barrel I threaded the last 1.150" of the barrel to 13/16"-16tpi so that the barrel extension was a little difficult to thread on. Then I screwed on the barrel extension so that the back end of it was 1/2" from the back end of the barrel and drilled the index pin hole to a depth of just past the bottem of the barrel threads. I also drilled a gas port about 1.5" in front of the barrel extension since it was already squared up. Then I screwed on the locknut as far as it'd go, and then screwed on the barrel extension with red locktite and secured it with the index pin made from 1/8" drill rod. After letting it set for a day I torqued down the lock nut and secured it with red locktite. Before the loctite set up I turned down the locknut to just under 1" with the barrel extension towards the tail stock so that any cutting force would be tightening the lock nut and not loosening it. Then I finished chambering the barrel after opening up the 556 bolt to .398" so the 9mm case would fit.
I then made a gas block for it out of steel and cut down a used rifle length gas tube to fit. The first few rounds of test fire showed that with a .090" gas port the bolt comes back enough to extract the case from the chamber and stop with the hammer half cocked so that the hammer catches the firing pin as it tries to go forward.
Thats where I'm at right now. The wonder 9 part of it is I wonder what it'll take to get it to run. More work and current photos to come!
 

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#31 ·
Here's a pic of the upper complete except for parkerizing and a muzzle brake. I'm going to try to make a levang type muzzle brake for it, but not to tame the awesome fury of the mighty 9mm luger round as it seems to kick about as much a a 22lr bolt action with CCI stingers. I want to make a levang type brake for it as they seem effective at directing the noise away from the shooter. Which is always nice for young shooters. It feeds fairly reliably with one bullet flipping up and jamming out of 2-3 magazines. I might be able to eliminate that by trying different spacing of the feed lips or smoothing out the feed ramp a little more. With the caterpilliar barrel lock nut on there Muttman joked that I should stamp it "Powered By CAT" :thumbup1: But in the mean while since we're still in a severe storm warning, I put the snow camo stocks on and took a picture between snow bands.
 

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#33 ·
Thanks Dark Knight. I started on a levang type comp on it, but stopped when I started getting a cold. No sense working on something with bubble head and screwing it up.
 
#35 ·
I managed some time to work on the comp. I turned some 1.25" 4150 rod down to 1.050" and drilled a .385" hole through it. Then drilled the six .185" port holes about 1" deep. I may deepen them to around 1.5" though. I knurled the back end of it. I need to decide if I want to reduce the diameter from the port holes back or leave it full size. I also need to thread it and parkerize it. I may also put a couple wrench flats on the back end and harden it. Here it is so far.
 

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#36 ·
I managed a little garage time and got the comp drilled and threaded. I also ended up drilling the 6 port holes to about 1.5" deep so there would be more overlap. That does mean that the tap ends up cutting into the port holes and that does put extra stress on the tap. I used a spiral tap (which does better with the interupted cut) and held it with the live center to square it up. I still need to use a boring bar to flatten the space between the bullet hole and the comp holes so the gas has a flat spot to impact against. Right now it's tapered from the 37/64" drill bit. You can see in the picture of the back of the comp, how the gas will impact the flat spot (the darker area) and also partially exit the 6 port holes. A couple of the port holes still have burrs on them and look a little hairy in the picture
 

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#38 ·
I wonder what velocity gains you could get with the 357 sig in a 16" barrel. A 6.8 sbc bolt may work for the 357 sig, 40s&w, 10mm auto as is or it may need opened up .002" or so. I was tempted to use my last assortment of ak parts to build a 40s&w gun that used sten mags. I don't know if the 357sig will work or not in the sten mags.
 
#39 ·
on my glock the 40 and 357 mags are pretty much the same mags.

i never seen a 357 sig carbine though i have shot many a 357 sig from 4.5" and 5" barrels. it is a nice speedy round with lots of "POP" from a pistol.

sort of a 7.62x25 toks bigger brother. light short bullets loaded for a sig carbine would make considerable increases in velocity i would think .

one thing about the 357 sig it makes mucho pressure for a pistol round. looks like it would run well in a DI based system.
 
#41 ·
.357 sig 115gr corbon
5" 1578 fps
16" 1768"

.357 sig 125gr federal premium
5" 1501
16" 1723



No 45 super but lets look at 44 mag (a little hotter true)
165 gr corbon
5" 1270
16" 1552

240 gr federal hydra shock
5" 1367
16" 1619

Glock 40 and 357 are the same mags
 
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