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Posted: 8/26/2011 1:50:05 AM EDT
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Earlier I reported problems chambering and feeding some (probably defective) 7.62x39 UMC fmj ammo through a MAK90. The bullet "guide" is pretty much at a straight, sharp right angle to the bullets being chambered. The bullet tips of the UMC ammo often came to an abrupt stop on the forward edge of the bullet guide, deforming the cartridge, sometimes forcing the bullet back into the case (dangerous). Various other makes of fmj ammo chambered and cycled flawlessly compared to the UMC, including some Winchester 123 gr. JHP hunting rounds.
I did notice that the bullet "guide" seemed to clip off part of the exposed lead tip on the JHPs, slightly deforming the tip and leaving a little pile of lead fragments on the shooting bench. Otherwise, the JHP rounds chambered and cycled without a hitch. Just wondering if it would be worth grinding down the sharp edge of the bullet guide. Although it would be nice to cycle JHPs without clipping the bullet tip, I'd hate to do anything that might compromise chambering / feeding. As I say, this thing has digested everything except this blasted UMC fmj up to this point. If it is advisable to grind down the bullet guide, are there any guidelines I should follow? Thanks! |
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Quoted:
Personally I would just knock off the edge with a dremel tool and don't take off to much because then it effects the feed angle of the bullet to the chamber...but I have had to polish some on my Ak-74 when building it.... I guess what I'm asking is how much is enough and how much is too much to grind. I mean, the rifle has functioned with everything except '99 vintage UMC FMJ and it clips part of the exposed lead tips off Win JHPs (which I could live with, by just using ammo it's known to function with). However, I'd hate to grind too much or the wrong spot and have it start misfeeding everything. Any pictures (worth a thousand words) of bullet guides that have been ground down or polished would be much appreciated. Thanks! |
| As I said just knock off the sharp edge and I wouldn't change the profile other than the 90 degree edge that holds up the bullet travel.....I use a chamfer burr remover that is at any hardware store..... but you can also use a rat tail file and do it lightly or a dremel with 600 grit sanding drum.. |
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I had the same problem on my Draco pistol. It was cutting SP's and HP's right down the middle of the tip and locking them up hard.
I can't get pics until tonight, but I just gave the edge a nice radius, maybe not even a 1mm wide bevel/rounding, if that. Any smoothness to the edge at all so it can't bite the bullet gilding metal will probably be enough. Just make sure you focus on the left and right feed positions from where they pop up and out of the mag. You can even ignore the center of the guide. It's not real picky because it's only real job is to rise the bullet and case enough that it gets it's nose into the chamber, then the rest of the 7.62x39's generous taper does the rest. Don't worry about grinding too much. A properly made bullet guide is going to be some seriously hard steel. A Dremel with a small medium to fine aluminum oxide stone, or some tiny rat-tail files will take a LONG time to take appreciable metal off of it. |
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