I have a couple of ideas what may be wrong do any of these sound like they could be the problem? I had a bit of spare time this weekend so I got around to doing a little extra gun work. I built a 30-06AI that shot very well considering it was all from scavanged or forum built parts It was a gift I was building for a nephew, he should be happy. The I decided to put together a 270/300RUM. I threraded and chambered a new SS 9 twist schillen non-fluted sendero style tapered barrel. I got that part right, I thought my indicator was broke when I went back in to check for runout. Then I threaded it for a SSG v-port brake and cut the crown.......had to do this twice and lost 1/2 inch of barrel But I finally got this done to my satisfaction. Put the barreled action into a HS take off I bought off the forums and had a great christmas gift ready for another of my nephews.........except it will not shoot worth a darn. I am getting 6 inches of verticle at 800 yards and I cant seem to tune it out. My usual practice is to get sighted in at 100 yards while I do the break in then move staright to my 800 yard target to finish my load work. When I get on the 800 yard target I tune the load to minimize verticle. Istarted out with a mild load of 94gr of WC872 pushing a 130 hornady and using a Federal 215 to light it off. I used 7 RUM cases that I necked down using my 270AM die because I didnt have a neck bushing that would give me suitable neck tension. I worked the load up to 97 grains fiddled with seating depth changed primers and nothing seemed to make it any better or any worsed....what the heck is wrong with this gun? Here is what I am thinking am I on the right track? Firing pin spring or work hardened brass? I only used three cases to break in the barrel and for any load work. I wish that I had thought to try more cases but it didnt occur to me until this morning that that may be the problem. It will be easy to rule that out. I have an extra long action bolt laying around I will switch the cocking piece out and rule that out too. Any other ideas why this gun is giving me so much verticle? If the groups were not perfectly verticle I would just try some different bullets, but groups are a straight up and down line. This is only the eighth rifle that I have built and have never had a problem making one shoot better that 1/2 MOA at 800 and has me scratching my head. Anything else to try?