Small Gas Checks?

[870TC]

Anyone else having problems with 30 cal gas checks from Hornady?
I've been having trouble getting them to go on without shaving a little lead off the base and leaving it in the bottom lube groove.

Things I have tried:
At least 10 different boxes of checks, all new, no old stock. (I size for a commercial company)
At least 10 different 30 cal molds.
Tried expanding the checks, (helps on most but not all), using a brass round head machine screw to tap the check with a 4oz hammer.
I don't cast them, but they have varied the alloy at my request to see if that makes a difference.

[Leftoverdj]

870, inspect the base of the shank very carefully. You are looking for signs that the alloy is intruding ever so slightly into the gap between the blocks and the sprue plate. One way to test is to rotate a bullet in a kids' pencil sharpener. Turn it the opposite direction from sharpening a pencil. You want to burnish, not cut. If the bullet will go into the GC after, but not before, you are dealing with a tiny fin. That's a casting problem, not a GC problem.

If that turns out to be the case, get the casters to check the sprue plate fit, reduce the casting temperature a bit, and reduce the pressure into the mould, if practical.