Rear take down pin trouble??

[NugginFutz]

Some parts came in the mail today. So I dug out the Spikes lower (blem) that I bought 5 years ago. They said it had a slight discoloration in the finish. I couldn't see it then and still can't see it.

I tried fitting the new billet upper to the lower and the front lug barely fit into the lower. Closed it up and tried to install the back pin. Went through to the far side of the lower, but no joy. I've squeezed the upper and lower pretty hard and pushed and hard as I can on the rear pin with my thumb.

I shot an e-mail off to the supplier, but won't get an answer before Monday. They will probably say it's the lower, and I don't want $20-30 in postage back and forth. I'm thinking of taking a few thousandths off the shoulder at a 45* angle on the pin. Least expensive part to replace.

Any thoughts before I fire up the lathe or grinder?

thanks,
CC

Have you considered removing the rear pin and fitting the upper to the lower for an alignment check? Before I cut anything, I'd be certain of how much misalignment was present.

It seems to me that skinnying up the rear pin almost ensures that a different upper would have fit issues. I've heard of a few folks that have reamed out the rear hole on their uppers to achieve a fit, but I cringe to think of it.