NFA Gen2 Polly Clearaning rear channel for Upper?

[Ironballs]

I have a NFA Gen2 Polly lower that needs clearancing rear take-down pin-channel. The Grizzly upper will fit in the front lug, but the rear lug doesn't sit in the channel. Can I grind /shave a little bit to make it fit, w/o jeopardizing the integrity of the lower?

I would like to hear from anybody & especially from NFA on opinions/solutions.

Thank you.

 

[Ironballs]

The NFA tech says:


"Yes, you can. It will not jeopardize the integrity of the lower.

Thank You,

M. S.
New Frontier Armory, LLC"

They responded very fast!

 

[STS Hunter]

I bought a stripped NFA lower about a year ago. What makes one a 2nd gen?

 

[Ironballs]

...What makes one a 2nd gen?

From Joebob:
*NEW GenII Lowers feature newly redesigned pivot and takedown pins for more strength and will not pull out, along with redesigned fire control group that will not allow safety to be engaged with hammer forward.

There may be other things, I don't know.