Joe, yes, i am going to Perry this year. Maybe we can meet up while there.
lte82 is spot on.
I missed the part that your are shooting a 308AR with a 26" barrel, putting you in match rifle category. I actually started out shooting the AR-10 in the service rifle class (20" barrel DPMS based M110 build) while i waited for my AR-15 to arrive...this was the basis of the advise i gave you before.
When your supply of 175s run out, i recommend moving away from the sierra line of bullets. Those bullet designs are old and hold back the 30 caliber chamberings...not bashing them or saying they aren't accurate or don't work, but they are outdated compared to the Bergers and the Hornady 178HPBTs, the 208AMAX and 208HPBT designs.
I am now a big Berger fan. I shot the 185Berger in front of 44.2gr Varget (or 41.4gr Ar-Comp) out of my M1A supermatch for the 1,000yard state match in Houston...while the 175s i shot the week before in practice was just going transonic (per feedback from the pits), the 185s were far more consistent, held better vertical and windage for me than the 175s.
The USAMU's 1,000yard load from a M110 (20" 308 AR) is 45gr Varget with 185bergers. This is the same load/rifle they used to set the 1,000yard record...200(highX count). So, as you can see, the 308 even in a 20" rifle can shoot and clean the 1,000yard target...you just have to be a shooting god to do it hahahahaha.
When you get a chance, run a ballistic program comparing the 185/175s at the same velocity (you can shoot em at same speed because they have the same bearing surface). With your 26" barrel, you should be able to get them up to 2,700-2,800ft/s without operating on ragged edge of pressure. You will be amazed by the difference in windage correction.
For the cost-conscious, the solution may be the 178gr Hornady HPBT. It has the same BC as the 190gr SMK bullet, but can be pushed about 100-120ft/s faster, you should also be able to get this bullet going close to 2,800ft/s if you use the right powders.
I would also check the throat of your rifle. My rifle was chambered with a looooong throat. So long, that i can shoot the 208AMAX at good enough speed to gain maximum wind advantage. If you are able to shoot the 208AMAX or 210Bergers, you won't wanna go back to the SMKs.
The Hornadys are about $10-$20 per box cheaper than the Bergers...you may want to buy a box of each of the 185bergers and 178HPBT (not AMAX).
Ar-Comp will not be the best powder for all this...that distinction belongs to 2000MR & RL-17. Varget is your best bet for temp stability but at the cost of lower velocity.
There are better calibers for shooting XTC, and i too would prefer to shoot a 6mm of some flavor (check out John Scandale's 6mm). It's based on 6.8SPC brass necked down to accept a 6mm bullet. It gets you about 85-90% of 243Win velocities with a better barrel life...still all these calibers will be ultimately more expensive than the .308 due to shorter barrel life.
Since you mentioned cost as being a concern, it does not seem likely you will be buying another rifle or switching calibers. I would work with what you got until its time to re-barrel or buy another rifle. The lowly .223/556 is still a good choice for XTC and will be about 50% cheaper than shooting the 308s.
