I did this project.
--unitized gas cylinder
--NM oprod spring guide
and you're there.
Springfield "Loaded" to M21 conversion. A National Match has no rear lug and is legal for service rifle competition. An M21 is not legal for service rifle competition.
1 - New stock
2 - Rear lug - welded
3 - Bedding
4 - Unitizing
5 - Clearance handguard
6 - NM sights
7 - NM trigger job (if not done)
8 - NM spring guide
9 - Large smile when done he
I would skip on the rear lug to tell the truth. While it will make the bedding last longer, you do see them crack from time-to-time. For the expense, it doesn't add a lot of tangible value to the rifle.
For the casual shooter probably not worth it, but for hi-power competition shooters who shooting thousands of rounds a year, it would definitely be worth the trouble. Even though I don't compete, from what I understand the serious competitors pretty much rebed their rifle once per year during the off-season(ie winter),
I was told that it would not be advisable to weld on an extra rear lug because of the possiblity of cracking the reciever during the welding process. The advice was if you want a rear lug, but it from the factory. I don't know how true this is.
BTW: The NM version also has a reamed-out flash suppressor. I forget what the reason is for this modification though. I think it was to prevent water droplets from interferring with the flight of the bullet when shooting in the rain?
That's one of the common explainations. The other one is that the larger dia will have less shock wave interference as the bullet leaves the barrel--I don't know if I buy either one. I suspect the reason is that the guy assigned to do the drawing for the NM spec rifle thought it sounded like a good idea.
I've skimmed my M1A twice--once at about the thousand round mark and once about a thousand rounds into the second barrel. Both times I did it because I had the sneaking suspicion that it wasn't shooting like it should--nothing really evident on paper, but just an antsy feeling. The service rifle teams used to skim the bedding annually--they also shoot 6 days a week. Most civilian competitors are doing well if they shoot 6 times in a month. The teams invented the lug to get around having the skim the rifle halfway through the season (and also used to crack the lug shooting 190gr bullets).
I don't know of anyone that does it annually, but then again I only know of maybe a half dozen guys that shoot the M1A that I would consider to be hard-holders. There just aren't that many of us on the firing line these days.
FWIW, the lug on the SA Inc rifle is welded on. At least with the factory job, you know that it was properly heat treated afterwards--and if it came on a complete rifle, it's got a lifetime guarantee.