I got a new bolt action tactical build and started my load development. The barrel is a Kreiger standard Palma 1:8.5 and chambered with what is called a Lapua reamer. I used H4831SC, H4350 and H414. The bullets were SMK 142 and 123. Hornady 140 A Max and Berger 140 VLDs.Primers are 210Ms. Brass is Lapua. I did all of my testing at 100 yds. off of a bench in very good conditions. All groups are five shot.I could not find any combination that would give me groups consistantly under .75" I had a lot of tight three and four shot clusters but seldom got a full group under .5". I changed all the usual suspects, Scope, mounts,action screws, seating depths. Checked bullet runout, .0013" maximum. I called my gunsmith for help and said he would check it out if would send it back but he first asked me to call another of his customers that he had built a similar rifle for and see what he had to say. I did and found out that the other customer had the same make and spec barrel cut with the same pattern reamer. I described my symptoms to him and he said that his rifle had acted the same way. His would only shoot well with Lapua 139s. I got a box and eureka, I found it. After determining that the gun preferred to shoot with the bullets backed off of the lands my four group aggregate was .26". It shot good with the bullets jammed .010" but better backed off. I have a few hundred new 7mm-08 Winchester brass that I ran through a Redding FL 260 die. I tried those in place of the Lapua brass. The cases had the flash holes reamed and the mouths chamfered. The primer pockets seemed uniform and the primers seated well by feel and the primers were flush to -.003" low. The neck tension is quite high on the Winchester brass. I initially increased the powder charge by .2 gr. since the Winchester brass has more capacity. I ended up increasing the charge by a total of .5 gr.
This got me within 5 fps of my velocity using the Lapua brass. My next four group aggregate was 1.18" with nothing less that .90" I am well pleased that the rifle will shoot right at a quarter minute with any combination of components. However the extreme differences in group size due to different match bullets and brass is a little disconcerting. I have read the other post on this thread where one poster commented that his Winchester brass would not shoot until he turned the necks and annealed the brass. The neck thickness on my Winchester brass runs .013-.015. The Lapua runs .014-.015. My chamber neck diameter is .298. That neck variation should not cause a four fold increase in group size. The neck tension might but I will have to do some anealing to verify that. It still seems like a stretch to have that condition cause such a decrease in accuracy.
By the way the rifle was built by Jon Beanland. He builds a fine rifle and I have never experienced any better customer service but I have and am experiencing much worst customer service from some nationally know gunsmiths as well as just plain shoddy work.
This got me within 5 fps of my velocity using the Lapua brass. My next four group aggregate was 1.18" with nothing less that .90" I am well pleased that the rifle will shoot right at a quarter minute with any combination of components. However the extreme differences in group size due to different match bullets and brass is a little disconcerting. I have read the other post on this thread where one poster commented that his Winchester brass would not shoot until he turned the necks and annealed the brass. The neck thickness on my Winchester brass runs .013-.015. The Lapua runs .014-.015. My chamber neck diameter is .298. That neck variation should not cause a four fold increase in group size. The neck tension might but I will have to do some anealing to verify that. It still seems like a stretch to have that condition cause such a decrease in accuracy.
By the way the rifle was built by Jon Beanland. He builds a fine rifle and I have never experienced any better customer service but I have and am experiencing much worst customer service from some nationally know gunsmiths as well as just plain shoddy work.