Before I get started, I want to add the disclaimer that when I purchased my SA Standard M1A (with walnut stock) in December, I wasn't expecting, or at the time, desiring a M21. However, after a few months of shooting Port ball, and getting a feel of the gun, I decided to try some different loads. Since my eyesight isn't as good as before, I put a scope atop it that I originally had on an AR.
Rifle: Springfield Armory M1A Standard and walnut stock, with 244 rounds through the gun
Time/Date: 1600-1800 CDT 30 August
Range: 100yds, from bench, resting on sandbags
Altitude: 890ft MSL
Temp/Conditions: Balmy 89F, Partly Cloudy, Wind from ESE, gusting to 15 (range faces NE)
Scope: Leupold M8 6x42mm (I liked fixed scopes)
Mounts: ARMS 18 with Leupold Mk4 1" rings
Ammunition: 1 box Federal GMM 175gr HPBT, 1 box Winchester 168gr HPBT Nosler Match
Since the scope was zeroed at 100 for the Port, I wanted to see how far off the scope was from POI. First two shots (Federal) 4 and 4.5" up, 1" left. The next two shots surprised me, because I had a burst of two rounds--with one missing the paper (but staying inside the berm). After inspecting the rifle, and downloading the magazine, I proceeded to shoot the next 6 rounds at the target. I allowed for the rifle to cool down between shots (45 sec to 2 minutes) as well as not changing cheekweld. The first group of 9 on the target was unimpressive. Although some shotholes were near or touching, they weren't part of the same shotgroup. 9 shots filled a 4" by 4" square. After cooling, I shot the rest of the Federal box, with slightly better results. The last five shots of the box ended up in a nice X pattern, about 1.75" from diagonal corner to corner.
I cleaned the rifle (and found a lot of brass flakes from the Federal brass), and then proceeded to shoot the Winchester. The first round struck 2.5" 12 o'clock above center. After firing the rest of the 10 round group, I was thinking the Winchester was a better round for my rifle. Ten shots fell within a 3"x3" square. I adjusted my scope (shots were high left), and shot again. As I was rapidly running out of time (10 minutes to shoot 10 rounds), I only gave 30 seconds between shots. Here the Winchester proved to be the better round in my rifle. 9 out of 10 shots fell within the inner 2" circle, with 5 shots at 1.25".
I want to do some more testing (get a box or two of Black Hills) to look for a Match round for my gun. Why? I just wanted to see what the rifle will do when 1) I can see the target and 2) the ammo is of quality and consistent. Yes, it won't be taking LRCHs off of gnats at 500yds like my bolt gun, but will still do some nice things.
Oh, and if Winchester (with less brass flakes in gun than Federal) proves to be the best round for the gun, I hope I can get it reloaded, because the cheapest I can find it is $20.50 a box! Yikes!
Good range report. As you said the group sizes are not too impressive, but this is where you start, by finding out what the rifle likes to shoot. I feed my M1A (iron NM sights) the loads that shoot good out of my custom 308 bolt gun, and especially thos loads that I tries and did not perform as good as hoped in that rifle. Oddly enough it likes a 155 grain Sierra MatchKing handload best so far.
Make sure your bore is good and clean when seeking to find that best ammo. If you do not handload try some other factory loads but stay away from the "light magnum" loads and other hot loaded factory ammo as your M1A gas system might not like them.
Several guys report good results with Black Hills ammo, it is reasonably priced and loaded with great bullets.
Id put money on it that you will see accuracy improve as you continue to break it in some more.
Welcome to the Gawd's-Honest-Rifle club
I have done 1.5 inch 5 shot groups at 100 yards with Port ball from prone with my standard.
I can't do it on demand anytime everytime but I have done it enough to know the rifle and I are capable of it.
Someday I would like to see how match ammo does with a realy good shooter behind it.
Try some Federal 155 grain match ammo. www.ammoman.com is one supplier of this ammo. Your standard M1A (1:12 barrel twist) may like a lighter weight bullet.