I have just bought a Colt pre-ban with one of those annoying blocks.  I have no intention of converting to full auto but would like to get rid of the block.  I have access to a milling machine and could do a good job of cutting it out.  Any comments about the legal aspects or if it would decrease the value of the pre-ban?  Thanks

its prefectly legal to remove the block. as far has hurting the value i dont know

I think it probobly would lower the value, from a collectors standpoint. The hole left from the removed block should be filled. This, even done perfectly, will lower the overall condition of the lower. But I feel the whole sear block thing is a non issue. First of all you shouldn't ever need to sell it. And if by chance you were going to commit a felony and convert it, why bother using an expensive pre ban, use a new lower instead.