[Bottom Gun]

I've been shooting nothing but ball ammo and FMJ reloads in my AR-10 in the four months I've owned it and it has functioned perfectly. This weekend, however, I shot some soft point reloads through it for the first time and it didn't work very well.
I shot some 150 and 165 grain Remington CoreLokt bullets I loaded.
With a full magazine, they worked well but as the magazine reached the half full mark and the spring tension decreased, the rifle started jamming.
The cartridges in the magazine were walking forward and deforming the tips of the bullets in the magazine. It flattened them more than any I had ever seen in the past. It flattened them to the point the flats started catching on the base of the feed ramp. Each time that happened, the bolt pushed the bullet far into the case and jammed the rifle.
I kept checking the cartridges in the magazine to see if the bullets were walking back into the cases, but they weren't. They were only forced back into the cases when they would catch on the ramp and jam the rifle. I didn't crimp these cartridges but I'm not sure it would have made any difference if I had.
I tried several different magazines, 10 and 20 rounders, and the results were the same. The soft points would all walk forward in the magazines once they were at the halfway mark. I also shot Portuguese surplus in these same magazines and had no problem at all. They didn't appear to walk in the magazine at all. They were longer than the soft points though by about .100 inch though and consequently stayed where they were supposed to in the magazine. The Remington soft points became even shorter as they banged against the front of the magazine. I don't feel I had them seated too deeply though since they have cannelures and that's were I seated them.
I wish I'd had some other type of soft points along so I could compare them to these CoreLokt's.

I'm at kind of a loss as to what to do to correct this since I did want to hunt with this AR-10 this fall. Maybe I should try something with a polymer tip like the ballistic tips or SST's?
Is overall length critical with these rifles? Is there such a thing as loading too hot? These loads were right at max according to my Lyman book. I didn't see any signs of excess pressure but I wouldn't want to go any hotter.
Since it works fine with ball ammo, I'd sure like to try to correct this with my loads before I start bending magazine lips or modifying feed ramps.

I'd welcome any suggestions as to how I might correct this.

Thanks,

Ken

[AZ Jeff]

It sounds like the rounds are jumping forward in the mag, and smashing the tips against the front mag wall under recoil. The reason that it only does it with less than 1/2 a mag is that the friction between the cartridges is higher when the mag spring is more compressed, thus holding the rounds still in recoil.

Here are some possible solutions:
1. try different brands of soft point bullets, looking for harder lead tips
2. switch to ballistic tip bullets, such as Nosler
3. figure out a way to block the mag spring up from the bottom so as to simulate having at least 1/2 a mag of cartridges when the follower is at the top of the mag. (A block of wood cut to fit the space between the floorplate and the mag spring would do this nicely.)

[Bottom Gun]

Yes, That's exactly what is happening. I'm losing the spring tension in the magazine as it empties.

I think seating depth may be part of the problem as well as bullet type. I'm going to try different types of bullets and seat them out as far as possible so they won't have as much room to travel in the magazine.
The polymer tipped bullets are probably the answer although I'd rather use a regular soft nose bullet if possible.

The magazine block is a great idea. I need to take my 5 round hunting mag apart and see if I can do something like that with it and still maintain a 4 or 5 rd capacity. If so, that could very well solve my problem.