40 grains of IMR4064 is a tick below current minimum of 41.5 for a 168. Not enough to worry about, but that card is old. Buy a Lyman manual. Max is 45.9(Compressed). Compressed loads are nothing to worry about.
You need to check case lengths(Trim, chamfer and deburr as required only), FL resize every time(no neck sizing only, ever, for semi-auto's, lever actions or pumps. ) and watch the OAL(2.797" is ok. 2.800" is MAX. And that's from the point of the bullet to the flat of the case head, not the ogive of the bullet.) for any semi-auto. No crimp is required for a semi-auto either.
Not FL resizing will cause your issue. So will case length. Set your vernier calipres(preferably digital) to 2.015" for .308 and use 'em as a gauge to check lengths quickly.
There's no such thing as a "case length head space gauge". Cartridges do not have headspace. There are case length gauges and headspace gauges(that have nothing to do with the case), but not one in the same.