I just finished putting together a lower built on a Stag receiver and LPK with an A2 buttstock I picked up at a gunshow. Believe the buttstock is a Bushmaster, but I'm not positive. Anyway, the spacer between the buttplate and the buffer tube rattles. All the references I can find say the buttstock spacer should be 5/8" across the main part, where mine measures 9/16". Anybody have one laying around they could measure for me?