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Tweaks to feed 2.75" from a 3" magazine

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This might be a bit premature, but I thought I'd share a few tweaks I've made to assist with feeding 2.75" shells from a 3" magazine. I say premature, as I just picked it up Monday evening and have yet to fire it at all yet. Found an RAA import from '06 that was still NIB at a great bargain and have spent the last couple nights tweaking & modding.


First off, I tried feeding the 2.75" shells as it came right out of the box. Hand cycled a full mag with no hitches whatsoever. Figuring that was a total fluke, I slowed down the bolt return to battery controlling the bolt by hand and then saw what the problem was going to be. The nub on the bottom left side of the bolt pushes the shell out of the magazine, cocking the shell a smidge to the right...just enough to snag the shell on the right edge of the upper barrel extension. Went back to letting the bolt slam home under full spring pressure, and sure enough, it WEDGED a shell into this area on the right side extension. Out of the box, 9 out of 10 shells feeding seemed acceptable until I can get ahold of a 2.75" mag, so I pressed on.


Having read that most folks seem to have issues with the shell impacting the bottom of the barrel/feed ramp. I got my small sanding drum with the fine grit and blending the lower lip of the barrel into the feed ramp, just like you do for a S12, and polished it up.


After some conversion work, I got back to the barrel extension, examining contact points between it/them and the shell in the magazine. The top edge of the shells were making minor contact with the very top of the big part of the barrel extension as well. First, I used the same small drum to chamfer the right lip of the barrel extension about half way through the thickness creating a mini side feed ramp to guide the shell back toward the chamber. Then, I repeated the process for the rear most portion of the top edge of the barrel extension, but not quite as deep...polishing everything after the sanding. The angled edge of the top extension is what cams the bolt closed, so I tried not to monkey with that as much as possible - too thin there and the bolt will eventually beat it into a shape that's not conducive to proper bolt camming action.


All said and done, I can load the mag up, let the bolt close by hand until the bolt contacts the top round in the magazine, and then let the spring carry the bolt closed under spring force and each round plops right into the camber - easy peasy. Full speed hand cycling is running like clockwork as well.


Tomorrow evening will be the live fire test of all this...


In any case, the little arrows are pointing to the parts that got chamfered or ramped:






This is just a different angle, without the arrows:






And finally, a crappy cell pic of her as she sits now:



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Well, I suppose I can't say that the minor tweaks I did will fix an S20 that has some serious issues, but I just got back from the range and put a box each of Federal 7/8 oz @ 1290 fps and Federal 3/4 oz @ 1400 fps through her and not a single malfunction there with the 3" magazine.


I also had some Win AA reloads to test, but they were too weak to eject the spent casing & squishing the hulls, so I only shot 5 of them so I didn't mangle up too many hulls. I've got a CSS reduced power recoil spring that came with the "reliability kit" I got for my 12 that I'll try with those shells next trip out.


OT, but I bought a Mec 650 from my uncle set up to load a 13/16 oz load of #8 over a yet to be measure charge of Red Dot along with a box full of AA hulls. He said that was his old trap load for his Ruger Red Label, so I've run with it so far in the Mossy. Apparently it's notably weaker that cheapo Federals from Wally World. Anyone need 5 lbs of Red Dot...?

Edited by abyssdncr
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