Does it still look good . Any corosion on the brass or bullets? I have had good luck w/ surplus ball ammo from the 70's & 80's. If it was stored in a dry place and not been exposed to real hot conditions it should be OK. YMMV
I have 3 FAL mags for sale. In good shape. 2 are Belgian. Small areas of surface rust on 2. These have been in storage for about 6 years. The darker one isn't Belgian. I sold both FAL's a few years ago and don't need these. There isn't any marks at all on the follower of the dark colored one.
$50 shipped.
Before you start drilling on things how about you put a few layers of duct tape on the face of the buffer and see it that solves the problem. If that works then you will know modifying the buffer tube is worth it.
I ordered an upper from Bear Creek that had an AR-15 rifle length gas tube for a 6.5 Creedmoor. Large frame AR's take different parts. Some manufacturer s don't understand the difference.
That is a AR-15 gas tube in there. The AR10 rifl
s tube is longer.
https://www.armalite.com/SACItem.aspx?Item=10007010
This is the one you need.
Here is the link to the proper buffer.
https://www.armalite.com/SACItem.aspx?Item=EA1090
This link has the spring and buffer and gives you a spare extension.
https://www.armalite.com/SACItem.aspx?Item=AR10REKIT02&ReturnURL=/Armalite/Product-Category/AR10-Parts-Accessories/Lower-Receiver-Parts&Category=ac614400-ff09-4cdf-9d35-419a654e7201
If the web says out of stock call them they usually can find the parts.
The monstrum scopes are cheap Chinese scopes. I have 2 and they hold zero so far. They are on short range toys. My serious guns get better scopes.
I always install the rings first and then install the scope