I have new C3 enhanced billet lower, and a Windham lower parts kit. The buffer retainer will not fit in the hole for it though. I don't know if I should contact Windham, or C3. I measured the buffer retainer with a caliper and it has an outside diameter of .249". I also managed to get my caliper in hole and the hole measured .248"
I am building on a shoestring budget, anyone have any advice? Should I contact Windham, C3, or just see if I can find a buffer retainer that is .247"?
**Update**
I decided to contact Windham first. Got an email back from them already. They said said that the measurement on the pin should have been .247" and mil spec for the hole is .250" +/- .006" so technically the hole is still mil spec, though on the tight side of the tolerance range. They are sending me a new pin.

Gotta love good customer service.