PS MAC-10/45 Failure to Fire

decngb

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I haven't used my original upper in my Powder Springs MAC-10/45 in years since putting Lage goodies on it. Until today, that is. With the original upper and bolt installed, pulling the trigger releases the bolt as normal, but the firing pin apparently doesn't even touch the primer. The gun is cleaned and oiled. Is there something than may have fallen off the bolt after years of storage? Any good videos or instructions on disassembly, inspection, and reassembly of the original bolt? It works fine with my Lage upper installed.
 

root

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In the barrel pinned in?

If not it can walk out and afffect headspace.

Had a barrel I had to take 30k off of the receiver side of the flange to set it
Same deal no primer strikes till I did that.

How does the FP on the bolt look?
Could be a issue also.
 

A&S Conversions

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Are you sure that the bolt from another upper didn't get switched? The old style bolt extractor needs the barrel clearanced for the extractor. If the old style bolt is used with a new style barrel, without that clearance, the extractor hitting the barrel will hold the bolt from fully chambering. Just a thought.

Scott
 

BlackBelt

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Did you try different ammo with the same result?
Is the ammo you are using reloaded?
Did you try different magazines?
Have you changed the mag catch to a different one, or done a 9mm conversion kit recently? (The factory 45 mag catch is usually smooth on the end, whereas the factory 9mm catch usually has ridges where your finger engages it.)
 

Jack007

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The old style bolt extractor needs the barrel clearanced for the extractor. If the old style bolt is used with a new style barrel, without that clearance, the extractor hitting the barrel will hold the bolt from fully chambering. Just a thought
THIS!
 

decngb

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In the barrel pinned in?

If not it can walk out and afffect headspace.

Had a barrel I had to take 30k off of the receiver side of the flange to set it
Same deal no primer strikes till I did that.

How does the FP on the bolt look?
Could be a issue also.
I'll have to look it over to see if the barrel is pinned. The firing pin looks normal, but I don't have another to compare it to. It's a nice rounded point with no appearance of wear.
 

MitchWerbellsGhost87

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I’ve noticed that this doesn’t always happen. Sometimes the old bolts work okay with new barrels that aren’t clearanced for the extractor, and then sometimes it really whacks the barrels and doesn’t close fully into battery. Im not sure why, it almost looks like it is because of the bolt, like the extractor protrudes a little bit further with some MAC/rpb bolts more others? The large majority of RPB barrels didn’t have that extractor clearance notch, and they used the original MAC bolt castings in those guns, machined slightly differently than early MAC, but the same dimensions. The only thing I have noticed is that the barrels without the notch do not always properly extract snap caps, but they will usually run okay with live ammo, I assume it’s because the extractor isn’t necessary to eject the casings on a blowback SMG. It is really only there to pull cases that expand a bit and stick in the chamber too much for the blowback pressure alone to blow them out.
 

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