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Posted: 7/4/2007 12:02:43 PM EDT
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I have built an AR to use thompson mags. The gun works great. I would post pics, but can't figure out how. |
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You need to open an account with one of the picture hosting websites. I use www.picturetrail.com or photobucket.com. Upload your picture to the picture hosting site. Click on the properties of the picture you uploaded. Highlight the URL of the picture. It will start with http:. Copy the highlighted URL. Go to AR15 .com where you want to post the picture. Click on the little picture icon. It will open a new small window in the upper left of your screen. I am very interested in how you got the bolt carrier to clear the feed lips and stirp a round. Did you use a Colt/RRA type bolt carrier or an Oly type? What mods did you have to make to the mag and did you use a magwell block of some kind? |
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ETA: That's HOT /Paris When do you go into production  Or just one for me anyway  Would be really cool if we could get one of the billet lower makers to leave a little extra thickness on the mag well walls for this. 
I'd prefer that design, that way one is not stuck with an Oly upper receiver. I guess the receiver needs modification anyway so it's probably a non-issue... |
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I dug out a Thompson mag, a couple of lowers (Double Star and Sabre), and the calipers. Looked like my lower (either one) would need at least .030" removed from each side, and that would still be a tight fit. I did some more digging and found 5 more Thompson mags (there's another four, somewhere) and measured those. The first mag was apparently a little oversize, and the others would probably do just fine with .025" removed from each side of the magwell (one of them might work with .020" from each side). The wide mag is marked "U.S. - 30 CARTRIDGE - CAL .45", and has a manufacturer's mark with "CO" inside a larger "C". Most of the other mags are Seymour Products mags. ETA: I found the other four mags. All four have the same markings as the first (wide) mag I measured. Two are the same width as the first one. One is about the same width as the Seymour Products mags. And the fourth is about .008" wider than any of the other mags. Looks like careful mag selection is going to be critical for fit. |
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I will try to get some video this week end. I used the AR mag catch, it did however need to be thinned were it touches the mag, so not to hit the live ordanance. Thompson mags come in a wide variety of thickneses . Two of my mags needed a little squeezing in a vise. I used a Bushmaster lower , as it had the widest extierier mag well tolerance of all my lowers. |
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Can you take a good picture of the amount of material you removed from the bolt carrier? I tried a Thompson mag in my AR45 lower and when I seated the mag high enough to feed the rounds, the bolt carrier hit the back of the mag. Did you remove any material from the back of the mag where the bolt carrier would hit it? Also, by putting th emag farther back in the magwell and using a ramp, the feeding issues I experienced with the Oly mag forward position seem to have been solved. The LaFrance also sets the mag back towards the rear of the magwell.  
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| The mag needs to be set back to the ejector spring. I went throught several prototypes before finding the correct angle and rise. The only way it works is with front ramp. If you bring the round / mag up to high it interfiers with ejection so you only can allow the bolt to catch any round by as mutch as the lip ring.To allow for so little contact push you need to have a smooth longramp angle. Ramp angle + slopped barrel extention = smooth battery. |
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No room for a ramp on the AR45 lower as the mag is already all the way to the front of the magwell. I'm glad to see someone got it to work but it did take a modified lower, modified magwell block, modified bolt carrier, and modified magazines. All the things we avoided with our GG lower. I have a dedicated lower that uses Reising SMG mags but I had to modify the mag and used JB weld to make permanent magwell filler blocks. Works great but not very cost efficient. Mags are $85-$100 when you can find them. |
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I am not looking to sell , just give free information. The upper is a dedicated 45ACP. The lower can be returned to a 223 ( slightly modified ). The machining , 3 hours of set up and hand cranking. The mag blocks, 5$ materiehttp://pic20.picturetrail.com/VOL1568/9305313/17038790/264005240.jpghttp://pic20.picturetrail.com/VOL1568/9305313/17038790/264005222.jpgl. |
| http://pic20.picturetrail.com/VOL1568/9305313/17038790/264071905.jpg" border=0 id=img>http://pic20.picturetrail.com/VOL1568/9305313/17038790/264071901.jpg" border=0 id=img> |
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That is outstanding, very nicely done. It looks like this just might be the way that LaFrance does his .45's as well, perhaps Pinkerton could comment. You should put this up in the Build forum as well. You have me absolutely drooling, waiting for more photos. Maybe I should start looking for an Oly .45 barrel and bolt. Anyone want to make a repro LaFrance handguard? This is the kind of thing that makes surfing through all the BS worthwhile, congratulations on a fine rifle. Now that I think about it, did you give us a shot of the complete gun? |
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I now have some in action video but need to figure out how to link it up. http://pic20.picturetrail.com/VOL1568/9305313/17038790/263796372.jpg |
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465, Could you please tell me what the thickness is on that rear block you have in the magwell? I know where the Oly ejector rod is located in the upper but there are wire springs on the rod and I'm not sure how far forward I need to place my magazine to just clear them. 
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Tapco has Thompson mags for $6 each. ETA: The two I received are still covered with a heavy coat of cosmoline, and they don't appear to be beat up or rusty. |
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