precision rifle loading and loose primer pockets

[LTUME1978]

I have a question for experienced precision reloaders. I have a Savage Model 12 Long Range Precision Rifle in 6.5 Creedmoor. The rifle is extremely accurate (1/4 inch groups at 100 yards with hand loads that are neck sized). I bought a bunch of Hornady factory ammo in 2011 when I bought the rifle with plans to shoot the ammo then reload the brass. I have done that with 200 rounds and am on my third loading of the brass (including the original factory loading). The primer pockets are extremely loose on the brass. The factory ammo was supposed to be loaded with 41.5 grains of H4350 (they provide loading data on the box so that one can duplicate that) which is maximum charge per the Hornady loading manual. However, I had to pull a bullet because one round came with the primer upside down and found that it had 43.5 grains of powder in the case. I have been using Reloader 17 powder for my loads. I experimented with different charges starting at the minimum and going to maximum in 0.4 grain increments trying to find a sweet spot. All of the different charges produced the same level of accuracy and I could not see any signs of overpressure in any of the different charge levels. Since I got the rifle to learn how to shoot out to 1000 yards, I decided to stay at the maximum charge for all loads.

I was expecting to get more than two loadings out of the brass so I contacted Hornady. They requested that I send them some of the ammo for testing as they stated some early brass was soft. However, they want me to get the barrel slugged to confirm bore size as they stated that Savage had made some barrel bores undersized and that may be causing the primer pockets to go loose. I contacted Savage and they did not seem to know what Hornady was talking about. They asked if I had any problems removing spent brass. I told them no, that the spent brass came out of the rifle easily (no sticking). The primers did not show signs of high pressure either. They said that I did not have a problem with the rifle bore size. I don't want to take the rifle somewhere to have it slugged and take a chance on something happening that will mess up a rifle that shoots so well.

I have some questions about reloading for the rifle. I used an empty case with a bullet seated long to determine the length to the lands in the barrel. From that, I seat the bullets 0.025 off the lands (which is a lot longer than what the OAL in the Hornady manual calls for). I don't see any signs of high pressure (primers are not flattening out - have seen that and know what that looks like), no leaking primers, no problems extracting, etc. I know that if I went out to the lands (or within a few thousands of the lands), I could have pressure problems unless I backed off on the load and worked back up. Am I missing anything that could cause the primer pockets to get loose after just two firings? Hornady is the only company making brass for this cartridge so there are no options other than forming Lapua brass (others are doing that but I am not ready to go there yet).