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Posted: 1/9/2010 2:14:03 PM EDT
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I ran across an old .22 conversion unit I bought about 25 years ago in a deal with my first AR, a 1978 SP1. Anyway, the .22 converion unit is marked as follows:
Atchisson M16/AR15 .22 L.R. Conversion Military Armament Corp. Marietta, GA, USA What magazines fit this unit? I have 1 original mag, but would like to find a couple more if possible. |
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If this is the tubular conversion, only genuine Ciener mags will work without modifications to the bolt or mags. modded /bdm mags will have lips thinned so much they will be fragile.
There's a buffer in the back of the unit that deteriorates, permitting the bolt to come far enough back that the habber hangs up and the bolt won't close. Cork, neoprene, urethane, etc about 3/4" thick fixes it. |
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There's one for sale here. http://www.gunbroker.com/Auction/ViewItem.aspx?Item=148535787#PIC
There are quite a few pictures here and I believe the seller is implying that it will work with JAC (Ciener) Mags of current production. If nothing else maybe you can sell it and buy a new conversion.. Good Luck, Spec |
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Spec, I have one in inventory. I haven't shot it much, but the original mag has rust that distorts it and it won't feed (or load, for that matter). Ciener mags have the same profile as the MAC 16rd insert.
The incompatibility of BDM mags relates to clearance of the bolt with regard to feed lips, and possibly to the way the ejector fits between the halves. Somebody with a mill could relieve the bolt like somebody posted last year, but I don't remember what bolt they were adapting to what mag. I'm not sure that would fix the extractor clearance. Sleeper, to be cautious, I'd get one Ciener mag, you may be able to get a 10rd fairly cheap. |
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I have at least four 30s and three 10s. A round dozen full body BDMs and 4 skinnies. And now, 2 drums. and a 5 lot of 15s.
One of the 30s is BLUED and patented or patent applied for, Dayton, OH. Likely BroCal mfg, from the MKII Atchisson, which is open like the Cieners, but I understand has some detail differences (flat firing pin?). |
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FWIW,
I have the same old conversion unit, its one of those things you have, and then rediscover in a drawer many yrs later  , anyway
ordered a cmmg mag and gave it a try, as it comes you have to mod it, took me about 20 minutes to do the fitting and milling off the back side of the mag( on top< where the feed lips are, on the back,theres a step, you just take the step off), along with putting the conversion unit in the mill and opening up the mag well area so the new mag will go in, also, you might have to scrape off maybe .020 off the outside corner of the feed lip to get the bolt to clear it, just lightly scrape it, dont go doing any deep carving! NOTE< what ever you do on the ejector assembly leave some meat to hold it and just radius things out, and trim a little off the corners of the mag for clearance(did mine with a knife) as to the buffer, I had some poly laying around, turned it out and stuck it in the back , its about .750 long , kept trimming it back till the thing worked, but not allow the bolt to lock up, figure I will make up a few spares and toss them in the tool box so I have them if I ever wear out this one, also I took about 3/8 inch off the recoil spring seems to let it work easier, so far have after the initial test mag full , for tweaking things, the last 3 mag fulls of federal bulk , has ran fine for me 
hope this helps 
wow, just looked at that ad, they sold that thing for 199.00! sheesh you can buy a newer style for less!, and to think, mine had the price tag still on the box, 79.95 |
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Maybe you guys that know more about these conversion kits can help. I emailed CMMG and they tell me that their magazines will work with my Atchisson kit. What do you guys think?
Oops. I just saw the post above describing what needs to be done to make the CMMG mags work. I don't have a mill. Maybe I'll order one of the mags and see what I can do. |
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Quoted:
Maybe you guys that know more about these conversion kits can help. I emailed CMMG and they tell me that their magazines will work with my Atchisson kit. What do you guys think? Oops. I just saw the post above describing what needs to be done to make the CMMG mags work. I don't have a mill. Maybe I'll order one of the mags and see what I can do. I ordered the Black Dog mags, which appear to be exactly like the CMMG mags, in hopes of bringing my old MAC/Atchisson conversion kit back to life. The issued 10 rd mag was flimsly, and I wanted a higher round count. But when I got the mags, the mag lips were considering higher than the MAC mag, and in my opinion, would have taken a lot of work to file down the mag lips. There is the Atchisson kit, but their is also the Atchisson kit, as made my MAC and long since discontinued. I thought the same as you, and thought if it said "Atchisson", it had to be the same. But not so if it says MAC on it. |
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what do we have to mod the bolt for?
my bolt locks back on the last round, it feeds fine, extracts fine,, and so far the mag and conversion has been put into 4 different ARs and it worked in all of them, mag was sloppy in the mag well but the thing still functioned, (maybe Im just lucky today, I dunno) as to the plastic being rubbery, so far its not an issue for me, the warmest the mag has gotten is about 70degrees, and coldest was around zero, the other day now if it gets droopy in 100plus weather, , you wont catch me outside either
everything I did, to allow a new mag to work in my old unit, could be done with a dremil tool, and a pocket knife, the mill just keeps things straight, and pretty looking,thats all as to weakening the mag, what little I took off of mine, I dont see it bothering it, along with I m not going to just drop the mag and let it hit the ground either, for what its worth, AIM has the cmmg mags for 18 something with 1cent shipping, and I ordered 3 more , since the one I got worked out so well,
fwiw, my conversion unit looks just like the one in the gunbroker pics Huskytaio, the lips do look too high, you might have to shave off the out side corner of the feedlips, maybe .020 was the most I had to take off on mine and it worked, just go slow ,, look things over, trim here, trim there, also, when I ran across the mag, the cost is what made me try the cmmg mag, when you take the shipping off of something it does make a difference cost wise, along with, I had absolutely no clue whether the mag was going to work out or not, now that its looking good now, I will try to keep an eye out for a BD mag and try one too |
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My feeling is that without relieving the opening in the bottom of the bolt housing, and relieving the bolt to clear the mag lips, the alternative is to thin the mag lips to the point that I believe they'll be fragile and short lived.
There's a reason the plastic lips are thicker than the formed sheet metal of the original MAC and later BroCal and Ciener mags. |
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