Bullets sometimes jam into front of mag when chambering.

[rsilvers]

Anyone ever have 220 Sierras sometimes jam into the front wall of an aluminum mag on the first round when you chamber it (with a fully loaded magazine)?

If so, is there a fix? Perhaps related to the OAL of the cartridge?

[TCCrewchief76]

MagPul PMags.

[Hoser]

And just like with 223, download by a round or two.

[Alleycat]

http://i112.photobucket.com/albums/n173/dabid82/dremel_foto.jpg
I dremel all of my mags. Most of the jams I had were from the front of the case mouth hitting the square edge of the mag. A little radius on the mag and all is well. Or Pmag, but I can't get used to the feel of them.

[LouBoyd]

Next time a cartridge jams before you clear the jam inspect carefully what the cartridge is hung up on, where the bolt is located, and think about how it all could have gotten into that situation. There are several possible ways for the cartridge to fail to feed properly. Most of the cures involve carefully adjusting the magazine feed lips, but there can be burrs on the barrel extension or other parts causing some of the problem. The lip of the magazine in front of the bullet in the magazine can be a problem on some magazines. The shape of the bullet ogive relateve to the feed ramp can be a problem The bolt should push on the case head, not the side of the cartridge, so the height the cartridge lies above the top of the magazine when the bolt is behind the magazine will affect feeding. The cartridge has to be able to rotate upward, but too soon or too late will cause jams. The 50 Beowulf with it's rebated rim is not the easiest cartridge to feed. Careful inspection and thinking will usually save having to buy mags or do unnecessary grinding. It may help to watch a cartridge feed while slowly lowering the bolt manually and watching just how the cartridge slides and tips as it goes into the chamber. Particularly watch how the bolt is pushing the cartridge all the way. It's safest to make up a few dummy cartridges for doing that testing.
I believe in polishing off rough magazine edges to allow smooth feeding but i've never needed to remove enough metal to warrant using a Dremel. Use one if you want but they can do a lot of damage very quickly if you slip. You can try P-mags if they work and fit your ammo. The center ridge down the front of a P-mag though is a bit constraining on cartridge OAL. It's easier to adjust the lips on metal mag than on a plastic one, which usually just involves light bending with no grinding.

That's just my experience. Use whatever works.

[Alleycat]

http://i7.photobucket.com/albums/y261/GawkyEndymion000/dremel.gif