Ok, I've done my research, and am continuing it (hopefully) with this post.
308 Win for MR F-class is not new, and been done over and over. I'm reviewing those posts now!
Rifle: DPMS LR-308, 24" barrel, 1:10 twist, chamber (listed as 308 match, which is .050" less freebore over standard 308 or whatever that means from the builder. Was recommended). Bullets: 155, 168, 173, 175gr (to be tested) All loaded to 2.800" Mag Length! This is the trick part!
Goal: My local club has started an F-AR class, basically .223 at 600y with a rule limiter to keep costs down and encourage more competitors. Bullets must be mag-length. Someone could theoretically buy factory ammo and compete with us without the need for a match built rifle.
Idea: Do the same thing for AR-10s and other 308-AR types. Trouble is, can someone really be competitive without a match built rifle?
Thought Process:
Distance (600y)
In the AR-15 by limiting bullet weight to 77gr, and length to mag-length, the biggest improvement over a quality barrel is to hand-load. Otherwise, not a whole lot will help you out, since custom chambers etc... are really for the single loaded 90gr bullets. I guess you could build a custom chamber for the short 2.260" load lengths, but I've yet to see someone do it and/or show an improvement by doing so, compounded by feed ramps and the semi-auto action, neck-turning isn't recommended, but it might help.
In the AR-10/308 style rifles, one could breach into a semi-palma style rifle. I know of guys using the 155 to 1k yards, but if bullet weight was limited to 180gr, and COAL to 2.800" (Mag Length) would that restrict a 308 enough to make a theoretical COTS rifle plausibly competitive?
Ok before you start flaming me, Theoretical really means the probability exists that this could happen, and its better than winning the lottery. COAL for Mag Length can change if you load 1, 2, or 10 so assume someone had to load 10 through the magazine (which brand changes it again). Bullet weight limit is simply to eliminate the single loader even further in 223, however, I don't have the experience to know if the 175 is at a ballistic disadvantage over the 155 simply due to velocity shortcomings? Is there any factory ammo produced that would allow someone to buy off the shelf competition? I'm also assuming that by restricting to gas-guns the neck-turning and brass handling gets a little relaxed over the bolt F-TR or F-Open. Would others agree? Am I in the right ball-park, or would someone do better with 110gr FB bullets?
In our club experience, we've found that the AR is usually 4-5 points behind F-TR rigs, but with a little wind who knows what can happen. We really don't have enough data to push one way or the other. We would also compare the 308AR rifles to F-TR to see how they performed, I wouldn't expect an AR-10 to outperform a well tuned F-TR rig in 308, but how close could they be is one question, and I'd sure have fun with that kind of challenge!
-Mac
308 Win for MR F-class is not new, and been done over and over. I'm reviewing those posts now!
Rifle: DPMS LR-308, 24" barrel, 1:10 twist, chamber (listed as 308 match, which is .050" less freebore over standard 308 or whatever that means from the builder. Was recommended). Bullets: 155, 168, 173, 175gr (to be tested) All loaded to 2.800" Mag Length! This is the trick part!
Goal: My local club has started an F-AR class, basically .223 at 600y with a rule limiter to keep costs down and encourage more competitors. Bullets must be mag-length. Someone could theoretically buy factory ammo and compete with us without the need for a match built rifle.
Idea: Do the same thing for AR-10s and other 308-AR types. Trouble is, can someone really be competitive without a match built rifle?
Thought Process:
Distance (600y)
In the AR-15 by limiting bullet weight to 77gr, and length to mag-length, the biggest improvement over a quality barrel is to hand-load. Otherwise, not a whole lot will help you out, since custom chambers etc... are really for the single loaded 90gr bullets. I guess you could build a custom chamber for the short 2.260" load lengths, but I've yet to see someone do it and/or show an improvement by doing so, compounded by feed ramps and the semi-auto action, neck-turning isn't recommended, but it might help.
In the AR-10/308 style rifles, one could breach into a semi-palma style rifle. I know of guys using the 155 to 1k yards, but if bullet weight was limited to 180gr, and COAL to 2.800" (Mag Length) would that restrict a 308 enough to make a theoretical COTS rifle plausibly competitive?
Ok before you start flaming me, Theoretical really means the probability exists that this could happen, and its better than winning the lottery. COAL for Mag Length can change if you load 1, 2, or 10 so assume someone had to load 10 through the magazine (which brand changes it again). Bullet weight limit is simply to eliminate the single loader even further in 223, however, I don't have the experience to know if the 175 is at a ballistic disadvantage over the 155 simply due to velocity shortcomings? Is there any factory ammo produced that would allow someone to buy off the shelf competition? I'm also assuming that by restricting to gas-guns the neck-turning and brass handling gets a little relaxed over the bolt F-TR or F-Open. Would others agree? Am I in the right ball-park, or would someone do better with 110gr FB bullets?
In our club experience, we've found that the AR is usually 4-5 points behind F-TR rigs, but with a little wind who knows what can happen. We really don't have enough data to push one way or the other. We would also compare the 308AR rifles to F-TR to see how they performed, I wouldn't expect an AR-10 to outperform a well tuned F-TR rig in 308, but how close could they be is one question, and I'd sure have fun with that kind of challenge!
-Mac
