I have an A2 Rock River Service Rifle upper. I want to change to A4.

Is it practical to swap in a A4 receiver in place of the A2 ?

Is it possible to change the gas block/sight to the low weaver gasblock for removable front sight?

Might be cheaper to just buy another upper.

quote:

Originally posted by striker1:
Might be cheaper to just buy another upper.

Not to mention more versatile. Definitely less of a pain in the ass. If you have no interest in having a 20" barrel anymore, sell the whole upper and put the cash towards what you want.

If you only want to change from an A2 upper to an A4 flattop, you can buy a a stripped upper receiver for about $50 and swap all your parts over. If you have the tools, it's a 15 minute job. If you are really looking for a completely different configuration, then buy another upper.

I did it to a Bushmaster set up for Service rifle last year,

swapped uppers, cut the FSB flat, and kept the float tube and A2 handguards,

took maybe 30 minutes (float tubes are a PITA sometimes and cutting the FSB off and rounding it out including a refinish to the part cut)

I converted both my service rifle A2 .223 upper and a 22lr upper into A4's. I replaced the A2 front sights with screw on railed gas blocks. I think it cost me less than $100.

I have the tools, but with the low cost of complete uppers from PSA, I’d probably just get the complete upper that floated my boat as opposed to a receiver only swap.

AR's are like Lego's ...
With the proper tools you can do about anything you want ... however I did find that with a 7.62x39 and the A4 with the detachable handle/rear sight, you need a taller front post to get on paper with the irons at 100 ... and with mine, the post had to be at the top of its adjustment to be on paper at 100 ... I ended up going back to the A2 ... then I had an extra upper and had to build another gun!

It's funny how things work out like that sometimes!