I bought two CProducts 10rd magazines for my 6.8. They function great so far, but capacity is different by one round based on ammo manufacturer. Both magazines will hold 9 rounds of Federal Fusion but 10 rounds of Remington Ultra-bonded Corelokt. Both rounds feed/fire/eject in the rifle. Any idea what the difference is? It's got to be case diameter, right? I don't have a caliper to measure the difference at this time, but how far off can they be and still work?

That's what it seems like but I can't see the diameter difference being enough to not allow the 10th round. Must be very little clearance at the bottom of the mag with 10 in it. Send the mag back or just cut a little off the spring.

Another possibility is that the ogive on the Federal rounds is rubbing against an internal rib on the inside of the magazine while the remington round isn't. Pressure on the ogive will push the front of the cartrige more toward the center of the magazine, thereby forcing the frounts of the cartridges to stack in a more upright rather than staggered configuration. Stacking in a more upright configuration forces the rounds to assume a more sing-stack-like and less double-stack-like configuration and reduces capacity.

I have noticed this same issue and have had to trouble shoot it when reloading 300BLK cartriges. When trying to push short light bullets that weren't designed for the 300BLK out toward the lands or maximum COAL, the ogive profiles proved too rounded to the point that the internal magazine rib rubbed against the bullets to an unacceptable degree. That can cause reduced capacity as well as have adverse reliability consequences. Therefore, I had to bump all those bullets back in the case to the point where the contact with the magazine rib was reduced to an acceptable degree. I also wanted my rounds to feed in a variety of magazines and the internal rib varies from magazine to magazine so I had to test my rounds in each magazine to make sure I set the bullets back far enough to function well enough in all my magazines.

Try loading and unloading the Federals in your magazines a couple times and see if the copper jackets show any wear on the ogive corresponding with any internal ribs in the magazine.

Thanks, Wildhorse, I'll check that. I got an email response from the company asking me to call them to discuss it. Honestly I'm fine if they only hold 9, as I'll be carrying them both or one of the 25s as well. I just thought it was interesting and wondered if anyone else had had similar issues.

Cproducts customer service is great. The will help you diagnose and solve the issue.