mac11 build taking shape

[scotthmt]

Helped a friend build this, not mine. Takes sten magazines, using the sten magwell and lower section, sideplates are welded on and welds have been grinded down and smoothed down as much as i saw fit.

[sava6e]

Very nice, hope your friend likes it, I built one and felt they feel weird, but hey gotta have some ghetto guns!

[madmike]

Looks great! Did you have any trouble with warping?

-madmike.

[scotthmt]

Tig would have definately been the best way, this whole thing was mig'd using a small mig welder with co2/argon, that weld will hold but it could be redone but honestly I don't want to do anymore gridning

The sideplates warped slightly, but I was able to bend the bow out and weld it so it couldn't move

Fredie, I have a cad file I took of the sideplates if your interested PM me

[madmike]

Do you think welding in small spots at a time, instead of continuous down the whole seam would prevent warping? Would it be as strong?
I'm thinking of doing an M11/9 build, and I'm hoping to do it right.

-madmike.

[hawk81]

If the material is heat treated, you don't want to get it to hot or you will ruin the heat treat. Welding a little at a time is the best way to weld it, and yes it will help prevent warping.

[scotthmt]

its having issues with failing to eject, and the primers are punctureing, i think it needs hotter ammo than these reloads i have

[rustycase]

its having issues with failing to eject, and the primers are punctureing, i think it needs hotter ammo than these reloads i have

Not necessarily.
And you have described two different problems.

If you provide more info, perhaps someone could offer a solution.
rc

[scotthmt]

1 out of 3 round will fteject, the shells get stuck in the upper jamming the bolt from closing on the next round, usually the primer is punctured, could have been all the time I should havecheckd but didn't. I think the primer is too soft, gets punctured, loses pressure and the bolt doesn't cycle far enough rearward to eject the spent casing, or possibly the ejector bar is worn andor too short.

[scotthmt]

So what should i do? Im thinking ill try hotter ammo or i'll sand a bit off the firing pin.

[scotthmt]

So does anyone have any experience with whats going on or have any ideas on what i should do? or am i onthe right track on my own.

[wilit]

Not an expert or even amateur gunsmith, but here's my guess.

1. Primer puncture: Sounds like the firing pin is too long? I would take the bolt out of the upper and push the firing pin in till it bottoms out and measure how much protrudes from the bolt face. Not sure where you could find specs on how far it's supposed to protrude, but you could at least check it against another 9mm firearm and compare.

1A. You did mention you were using reloads. Are you positive the primers were completely seated in the pocket?

2. FTE: From all my research (I've got the same kit sitting in my closet for the past 2 years) I think the jamming is pretty normal. Closed bolt Mac's are notorious jam-o-matics which is why in the free world they're $250 guns.

[saki302]

I don't know about that- the 9mm guns usually run quite well as far as I've seen.
If it's failing to eject, check your extractor tension, maybe the spring is weak or the extractor is damaged. Take care of your punctured primer problem first, then see how well it shoots.
I'd buy a new firing pin- check how far yours protrudes first.

-Dave

[sava6e]

how many rounds do yo have through it? how smoooth does the bolt move back by using the cocking handle? mine didnt want to work until the parts broke in and now have no problems

[scotthmt]

the bolt moves back easily if the hammer is cocked, if not it takes a decent amount of force to pull it back, i think the firing pin was hitting a bit too hard, i took a bit of material off the rear so it hopefully wont punch through the primers. I havent had it out again to check it out. i will be testing it again soon.