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Posted: 10/8/2007 5:07:31 PM EDT
| First, I'd like to thank those who have been answering my titleII questions. I'm new to this over the last year. Question 1, I have a MAC-10 that's papered in 9mm/45acp with both uppers. I'm looking at a M-11 in 380, is it convertible to 9mm? If #1 is yes, then is it legal to do so, being that it's form four reads only 380? Thanks |
It is legal to convert an M11 in .380 to 9mm. But it is not very practical. I know of a handful that have been done, and in every case, the additional energy of the 9mm round in the shorter .380 M11 receiver warped and battered the heck outa the frame.  The M11 needs the longer length of the M11/9 frame for sufficient bolt travel to bleed off energy. Of course, you can always download the 9mm to non-destructive levels ... but you are left with loads that are identical to .380. |
| Which 380? If it's a real M11, I would not mess with it. But if it's an M11A1, then it's basically a chopped M11/9 frame and uses the Zytel mags for both calibers. I've shot one converted to 9mm with a slow fire conversion and it was nice and slow. The only modification to the lower was a hole drilled in the back plate. The difference in price between 9mm and 380 makes the conversion worth while. |
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I disagree on the m11/380 going to m11/9. I have both full size uppers and the 380 isn't significantly faster than the 9mm. Here's a picture: www.125gp.com/~jester/pics/gun/SWD.jpg The m11a1 is a different animal. It's shorter, has a much higher RPM and would be nasty to convert to 9mm Jess |
I'm not sure what you disagree with. Yes, if you start with the longer M11/9mm receiver, you can also run a .380 upper with no problem or significant ROF increase. The .380 is a less powerful round, and with the same-length of bolt travel, ROF will not change. But if you start with the much shorter M11A1/M11/380 receiver and try to convert it to 9mm, you do not have sufficient bolt travel for the more powerful caliber, and in effect are forcing it to short-stroke. It is like installing the ultimate MacJack buffer, except without the additional cushioning of the fat buffer. The result is the bolt beating itself to death on the receiver backplate. YMMV. 
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OK, now I'm really confused:  Yes, I was speaking of the SWD M11A1/380 as being not easy to convert, because of insufficient receiver length. The original MAC and RPB M11/380s that I have had, on the other hand, all used a completely different, shorter steel magazine that is too small to fit 9mm cartridges. Converting one of these to 9mm would require cutting off the entire pistol-grip section of the receiver and welding on a new one that would allow 9mm magazines. AFAIK, no Mac-smith offers such a service. The only M11 I am aware of that can easily handle both 9mm and .380 is one that began life as a registered SWD M11/9mm, and for which a second aftermarket upper in .380 was added. So: SWD M11A1 in .380: Not easy to convert; may self-destruct due to short-stroking. MAC and RPB M11s in .380: Require chopping the receiver and welding on a new grip/trigger section. To me, that also qualifies as not easy to convert. Please tell me which factory .380 M11 is easy to convert to 9mm.
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Maybe I'm showing my ignorance? :) Here's what I have: http://www.125gp.com/~jester/pics/gun/SWD.jpg 9mm upper is lying loose above the gun. What I thought is a factory 380 upper is mounted on the receiver. Both are almost exactly the same physical size, differeing only in barrel and bolt face size. Everything else about them is identical. Thoughts? |
It'd be fast, but not as fast as my m11/9. Sorry 
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Your photo is of an SWD M11/9mm that left the factory as a 9mm SMG, and later had an additional 9mm-length-but-chambered-in-.380 upper added to it. Check the engraving on the rear right side of the receiver. It should read: "M-11/NINE mm / S.W.D. INCORPORATED / ATLANTA,GA U.S.A." A coupla 07/02 gunsmiths have made and sold .380 uppers for M11/9's in recent years. It's not that difficult: The barrel is an easy swap (drive out the retaining pin and unscrew it), and AFAIK you can usually even get by with a 9mm bolt. So the only new part required is the barrel itself, which has the same bore as 9mm but the smaller .380 chamber. Adding a .380 upper to an M11/9mm is a pretty cool idea -- the Zytel mags work with both calibers, though sometimes you need to tweak the feed lips for .380. Now if only there were a source for cheap .380 ammo! AFAIK, none of the Mac-family manufacturers sold 9mm/380 dual-caliber SMGs back before 1986 or offered .380 uppers for the 9mm versions. The RPB company is still around, and may have offered a conversion at some point post-'86. There's an excellent MAC family history and list of all variations at Scott's MAC-10 Page: home.earthlink.net/~jwet/mac.htm You'll note that the original M11 in .380, as made by MAC and RPB, was a scaled-down "fat Mac" that used the tiny steel mags. They also are one of the rarest Mac family variants, so I wouldn't recommend chopping on the receiver. The SMG in your photo is a 9mm-framed version made after SWD bought the rights and redesigned it, reducing the bolt from 1.5" square to 1" square and lengthening the receiver. The only .380 that SWD made was the M11A1, which is really just an M11/9mm with the rear of the receiver chopped off. The telltale sign is the manufacturer's caliber engraving on the right side of the receiver. Here are pix of SWDs in each caliber that I've owned, showing the different caliber markings and the difference in receiver length (and thus bolt travel): M11/9mm:  M11A1 in .380: 
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My lower is definitely m11/9. I thought the 380 upper was an OEM thing. The bolt face is smaller than the 9mm bolt but otherwise the same dimensions. Three of my zytel mags are stamped "380", and everything else was the same so I made an ASS(of me)umption that they made an m11/380 that wasn't an m11a1. Shooting 380 through it definitely hurts the wallet more than 9mm :) |
FYI. SWD did offer a 'factory' 380 conversion kit for the M11/9 pre-86. They marketed it as a slow fire conversion. It had a correct 380 bolt face. If this is one of those original kits, then it is a collectible as not too many were shipped. This was listed in the SWD catalogs and I think Firepower magazine did a write up of the conversion kit. |
Very interesting. I've never seen or heard of one ... but then, what do I know about MGs? I stand corrected. And thanks for the valuable historical info. 
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Seems like that could be do-able. The 9x19 magazines are tapered front to back, just as is the 9x19 cartridge, so that might be a problem for the straight-cased 9x18 Makarov round. The .380 (9x17) magazines are straight-sided, but might be too short to accomodate the 9x18. I wouldn't be surprised if either one could be made to work though. Sounds like a good project for someone with more mechanical aptitude than myself! 
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With all due respect to all the parties in this thread, the M11A1 or SWD M11, however you wish to refer to the gun, can be converted to 9x19 Case in point: http://i22.tinypic.com/3328e15.jpg In this photograph you see pictured my M11A1 with a long barrel 380 upper attached. Below that you see a 9x19 short upper. Since the gun uses zytel mags, 380 or 9x19 can be loaded. Min you however, this gun is a custom built M11A1 by John Norrell and has welds second to none. Many areas not welded on factory M11A1s or M11/9s are fully welded on this gun. To answer the big question, yes, loaded with 9x19 it does run like a striped ass ape. |
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