How fast should you be able to shoot a 165 grain out of a 308 with out a gas check? I am useing unique. Ten grains I beleive and I don't think the bullets are getting to the target at 50 yards in one piece.
First things first. Does this bullet have a rebated base to accept a gas check? While some people say the get good accuracy without a check at the lower velocities, this has not been the case for me in 53 years of shooting cast bullets.
If the bullet is a plain based model, then I believe that velocity should be kept right around 1400 FPS or a bit less for best results. I'm thinking some of the velocity estimates are a hair on the high side. I'm guessing you're getting about 1300 FPS with 10.0 gr. of Unique.
The idea to try that load at 25 yards is a good one.That load will be radically off if you're still using a full power sight in. Use a fairly large target to insure catching the bullets. Do bell the necks of the cases slightly as you do not want to damage the bases of those bullets, another good reason to use a gas check BTW. In his experiments, Dr. Mann in his book THE BULLET'S FLIGHT discovered that damage to the base caused great problems with accuracy. In fact, he felt it totally destroyed accuracy. The book is actually quite dry and boring, but there is good information if you're willing to stick it out.
Sometime, cast bullets can be quite puzzling. For example, you cam load a 110 gr. cast bullet to full velocity in an M-1 Carbine, but cannot reach the same velocity in a .308 or 30-06 and maintain the same level of accuracy. I never quite figured out that one, but belive it may have to do with bullet jump.
Two more things to check. Take a couple of those bullets and stick the nose into the muzzle of the rifle. They should not go in or if they do, be a snug fit. If they are loose, then you'll never get any kind of decent accuracy. The nose of the bullet should slightly engage the rifling for the best accuracy. At least it works that way in my rifles.
If the bullets are a proper fit, you should be able to get maybe 1.5 to 2.0 inches at 100 yards. At roughly 1300 FPS, trajectory will probably be a bit flatter than a .22 LR. Another thing that comes to mind, is you must be careful with your follow through.
Just what is the sized diameter of your bullets. Even though your bore is .308", your bullets should be at least .309" and preferably .310". Those diameters are perfectly safe.
Sorry if this all seems a little disjointed, but I'm trying to give suggestions as they pop into mind. I hope some of them will give you the results you're looking for.
Paul B.