Rifle - Ammo choice

That's loaded question. I think there is limited utility in 3 or 4 shot groups, especially when dealing with a cold bore. I did a lot of testing with my Ruger American .30-06, setting up a chronograph, logging chamber temperature with a thermocouple, testing various factory and hand loads (I was stationed up in PA with little else to do on my days off and plenty of extra cash ). I found that as long as the barrel was free floating I would have very little temperature-induced variation. I would shoot from a dead cold bore on a winter day, with cold ammo, in 10-shot groups and with the loads the rifle liked most I could cover the hole with a quarter at 100 yds. With the stuff the rifle didn't like it would take a playing card to cover the group. I never had any stringing effect as the barrel heated up which I did get with my M1A until I shimmed the gas block. Every rifle is a different story as is the person behind it though. You can try letting the barrel cool but without a consistent way to check the temp I don't know what that would tell you. There are companies that make bore cooling fans for range use but I don't think they are worth much unless you are really doing some volume range work. With the current batch of budget polymer stock rifles on the market, I'd check to see if you have enough flex in the forearm of the stock to touch the barrel while resting it your shooting position. I noticed this was a problem with my Ruger and using the Ruger bipods that attached to the front sling swivel lug, so I swapped out the stock for a Boyd laminate.

Every gun is different. Factory sporter barrels will react to heat sometimes and some are capable of 10 shot strings on target!! If your gun shoots the fusions dead on first shot every time then opens up I would take that over some of the others listed based on my personal experience with how fusions do on game.
When you say better how big a group you talking about 1in at 100 yards or 3in at 100yds ?

I hav e 4 rifles and they all shoot Coreloks very well.When I bought my A bolt .270 I tried 9 different brands and types of ammo and I got best groups with Core-loks(1 in.)My A bolt 7mm mag.shoots Federal premiums best,Core-loks 11/2 in.I have come to believe that the first shot out of cold barrel is most important for hunting.I don’t do long range shooting,though.Longest shot on deer has been 250 yards,I once knocked down boar hog at 500 yards with my 7 mag.

All solid advice, my only point is to “season” the barrel”. Shoot it clean it shoot it clean it. Do this for a box or so, I’ve always had some increase in consistency after doing this. Good luck

The way I was taught years ago is to begin with a clean barrel that is close to sighted in. Set up a rock solid shooting platform and a target 100 yds. apart. Load up any brand of ammo and fire the first shot but not at the bulls-eye of the target. My instructor called this a flyer and it is always the first shot after a clean barrel and it doesn't count.

Load up ammo no. 1 and shoot for a three shot grouping waiting about a minute between rounds. Don't worry about adjusting the scope to the bulls eye. What you are hoping for is a close grouping near the bulls-eye. Mark holes or load up another target. Wait at least 5 minutes then load up ammo no. 2 and repeat then again with ammo 3. If one of the three shots doesn't group well shoot a fourth.

After shooting ammo 3 you would have shot between 10 and 13 rounds. Clean the barrel and fire a flyer. Repeat if you have additional brands of ammo. Once you pick the right ammo now adjust the scope to the bulls-eye.

I have tried at least 10 different brands of ammo and my 7-08 likes Double Tap DT Hunter with 140gr. Barnes TTSX bullets.