Re: 200gr SMK\'s in .30-338
I've wore out four .30-.338, 1:12 twist, 28-inch barrels getting about 1200 rounds each. Sometimes using Sierra 190-gr. HPMK's and other times using Sierra 200-gr. HPMK's. All with full-length sized Winchester cases and RWS large rifle primers (mildest ones made). Used IMR4350 powder with 65 or 66 grains for the 190's and 64 or 65 grains for the 200's. Bullets were seated about .010-inch longer than throat contact.
Shot two 15-shot test groups at 1000 yards with each new barrel and 12-pound lot of powder to go with it. Groups ranged from 5 to 7 inches across all four barrels; the last one shot the best.
I don't think a 5-shot group tells much about accuracy. 10-shot groups are better and 15-shot groups are very close to reality. Any one of several reasons could be the cause of your dilema; barrel, bedding, sights, handloading process/tools. And if you're like me, I can't shoot a .30-.338 very accurate off a bench with any type of support; I gotta lay down on my belly slung up in a good prone position resting the stock's forend and toe on sand bags to test loads.