300-221 in an AR help me with mags
 

Hey guys I picked up a AR upper to go along with my bolt gun but I am having some trouble feeding them in my mags. I tried a few 20rnd Pmags and and one well used metal mag. Any hints and tips you guys can pass along?
I am trying to keep the same OAL between my Bolt gun and AR just to help with the reloading.
Dustin

Several friends and I have had excellent performance from C Products. I've got 2 10-round magazines and a friend has at least 4 30-round magazines that feed flawlessly.

The two 20 round PMags I have have major feeding issues. The rounds don't sit level and I get bolt over failure to feed almost every round. If I had not removed the front ribs on them I would have sent them back there is something out of wack with them. The thirty rounders with the front rib removed work fine. The mags that seem to work the best for me are DH Teflon coated G.I. 30 rounders, the only mods I made to them was to take the sharp edge off the front of the mag that would catch on the case mouth.

AR mags feed ammo for which the 0.250 ogive of the bullet contacts the rib on the magazine. Ammo makers design their ammo with this in mind.

That could be tricky. I load my bolt gun ammo a bit longer than my M-16 ammo.

And my bolt gun brass is Lapua so I keep it separate.

The way to make it easy is to make the OAL for the AR, and then use that in the bolt gun.

Any one have pics of this mod. The OAL does fit in the ar mag but the 220s might need to be set back just a little more to help with the feeding and stacking issues.

Dustin

Oh and thanks guys

USGI spec feeding
 

Previously from http://300aacblackout.com/ ;now I don't see it listed on their page anymore:

Existing AR magazines have a rib which normally contacts the 5.56mm case-neck. With 300 BLK ammo, the contact is on the bullet. Because the bullet is a larger diameter, the rib will push the cartridges out of alignment, and can lead to binding potentially resulting in Failures to Feed. For this reason, it is important to load ammunition so that the contact point with the magazine rib is on the bullet ogive in an area of about 0.250 inch diameter. Here are some suggested OAL for popular bullets:

• Hornady 110 V-Max, OAL: 2.000
• Barnes 110 TSX, 2.015 OAL
• Sierra 155 Palma, 2.150 OAL
• Sierra 220, 2.089 OAL
• Lapua B416 200 grain, 1.960 OAL
• Hornady 150 FMJ-BT 3037, 2.065 OAL
• Nosler Ballistic Tip 125 grain, OAL: 2.085
• Remington AccuTip 125 grain, OAL: 2.085
• Hornady 130 SP #3020, OAL: 2.010
• Sierra H2120 125 ProHunter, OAL: 1.950
• Speer TNT 125 1986, OAL: 2.010

To use my 20 round de-ribbed PMAGs for prone or from the bench, I put 30 round PMAG followers in them to stop the tilting. Lost a couple rounds capacity but they worked 100%.