Problem with AR magazines

[silvery37]

I loaded up some magazines to see how well my .300 whisper rounds would fit. It seems like if I load over 15 rounds in a 30 round magazine it becomes very sluggish. I havent tried shooting it yet but it looks like the mag would cause a jam. The rounds dont want to move up in the magazine because there is too much friction from the larger .308 rounds. Do 10 or 20 round magazines work better?

[redtazdog]

I loaded up some magazines to see how well my .300 whisper rounds would fit. It seems like if I load over 15 rounds in a 30 round magazine it becomes very sluggish. I havent tried shooting it yet but it looks like the mag would cause a jam. The rounds dont want to move up in the magazine because there is too much friction from the larger .308 rounds. Do 10 or 20 round magazines work better?
Have you tried a magpul 30rnd Pmag ?
They work nice and smooth for my 300 whisper with no mods to them.
If you get the chance load up the GI mag and the Pmag
and push a round out of each mag with your finger.
You will feel and see the difference, very little friction with the Pmag
and they feed without jamming up in the mag.

[Pitt300]

I followed jimcrowell's suggestion of loading to COAL of 2.14".
Then they fit fine.
Try a few!
I'm still working up loads so no pressure or Supersonic issues yet.
They load/shoot/print fine.
I got a 1.3" verticle group last week.
I'm still having cycling issues but I've just about concluded that it's w/my gun & i'm addressing it.

[jarhead1086]

Second that on the PMag, they work great because they have a smooth swept radius instead of an abrupt jog as they feed. The bullet ogive matches the smooth radius on the feed lips. This will allow you to load a little longer if you wish.

[jjmcrowell]

I may have to try the Pmag again. I tried them awhile back and had couldn't get more than a few in. Perhaps because I had started loading them short.

What length are you using with the Pmags? 2.25"?

What bullet are you using the Pmag, Sierra Match King or something else?

[jarhead1086]

It could very well have been an early generation PMag. The first few out were too tight in the width(?) and there were complaints of jamming. Magpul changed the molds and the 20 I have all run great in full auto with my M-16 and work great with the Whisper too. I bet if you still have the old PMags that Magpul would trade you out. I have shot everything from 130 TNT's to 220 MK's without a hitch. You can load long without the ogive touching like you see on the regular mags.

[jjmcrowell]

Yes, that may be it, I had some of the recalled magazines. They sent me new ones to replace them, but I'm not sure if I tried the new ones with 300 whisper.