I have several 6.8 and 6.5 ASC stainless steel magazines that I scored used. I believe several of the springs have been modified by the guy who had them before me while he was attempting to remedy a poorly-feeding AR (brand name withheld to avoid derailing my question). Until now, all I had used were the 6.5 ASC mags and I know they have been feeding my 264LBC and my 6.5x6.8 without fail. I'll soon be feeding a second 264LBC and also the American 30 as well; I'd like to have mags for each rifle. So my question is this: ASC sells magazine rebuild kits that include the spring and the follower. Does anyone see any difference in the 6.8 and the 6.5 magazines besides the color of the follower? My OCD tells me to get all the rebuild kits the same (6.5) unless there's a reason to replace them differently. I have attempted contact with ASC and received no reply.
I have both ASC 6.8 and 6.5 Magazines I'm using for American 30. The followers apart from color and caliber stamp appear to be the same dimensions. There is a slight difference with the feed lips. The 6.5 have a greater radius at the front of the lips. The front channel going down the length of the 6.8 magazines are slightly deeper, about .005". I have no way of testing the spring tension to check for any variance.
Hopefully ASC will get back to you soon. But from my perspective I would think the 6.5 rebuild kits would work for both.
I took as many measurements as I could with both and the only difference I can find in the ones I have is one of the legs on the bottom of the 6.5 magazine is cut about 2/10 of an inch shorter, and when I say cut I mean cut, they have very rough edges and aren't even cut straight. With that said, I can't see the rough cut mattering in the slightest, looks like the cut is made to allow for the slightly larger diameter of the 6.5, only 9 6.5 will fit in a 10 round 6.8 magazine with that follower, trimming it to match the 6.5 follower allows the 10th round to load. I couldn't hit the range today but the 6.8 mags with the trimmed followers allow for flawless manual feeding in my 264LBC and my 6.5x6.8. I just ordered the replacement springs for all the used mags