There are two other possible issues.
One is many of the new shotguns have chrome lined chambers with are much smoother and tend to prevent the issue. But, that doesn't explain that the older 870's don't have the problem. I doubt if the OP's chamber is chromed, nor that it was cut to the same quality of the old ones.
The second is the shell rim. Some of the off brands are made to work primarily in O/U and SxS and the rims are not necessary American standard dimensions. Although I haven't had a problem with Rio, Cleaver, and a few others.
I don't doubt a chamber rub will help the OP and hope it does, but it shouldn't be a 50 rounds problem. Would also be interesting to know if it happens with good Winchester, Remington, Federal shells with rims up to American specs.
Addition: As far as Smiths go, I had a Krieghoff that would get light primer hits with Winchester shells which wouldn't go off. Didn't happen with Remington. Smith was at the shoot and he told me Krieghoffs were made to shoot with Remington shells and that is all I should use. Yea right....
Must have been odd that other K-Gun users were not having problems with Winchester shells.
Last edited by battue; 01/17/17.
