BUIS rear with non-F marked FSB?

[Hmac]

DPMS with flattop...but has an A2 non-F marked front sight. For putting on rear BUIS, just add the longer front sight pin?

[bkb0000]

if necessary. try it without the longer post first, though.

[AMMOTECH]

You maybe be able to get a 25M zero with no problems but if you go out to 50Y then you will need the taller post.
You can get one from Bushmaster: http://www.bushmaster.com/products.asp?cat=21
Part No: 9349056-M

[Hmac]

Thanks for the tips, guys. It's my buddy's rifle and I'll let him know.