I had the opportunity to go to a Basic/intermediate sniper school hosted by a local police department. I got the green light to use run my 18" GAP AR10. The ammo supplied was Winchester 168 BTHP. I had sighted in the rifle with an old box of Win 168 and had good groups .75" at 100 a week before the school.
The first day of class we confirmed our zero and started doing drills. By lunch it became obvious that something was wrong with my rifle system. The groups had opened up to 1.5". I checked the rifle, scope and mount and all seemed to be in order. Then I found what I think is the offending part, the ammo. While doing some 2 shot drills and unload/reload I noticed that the loaded round I was ejecting from the chamber was bad.
It appears that the neck tension is not enough to prevent the bullet from being driven back into the case more than a quarter inch when it hits the feed ramp. In some cases I was able to wiggle the bullet with my fingers.
At some point in time I will run some of the ammo through a neck crimper and see if that changes anything. The day I sighted in my rifle I had been single loading so that is why this problem didn't appear earlier.
Luckily I had also brought along my Rem700 and just ran that through the school. If I had to buy my own ammo that would not have been my choice but like I said it was free. Lesson learned.
The first day of class we confirmed our zero and started doing drills. By lunch it became obvious that something was wrong with my rifle system. The groups had opened up to 1.5". I checked the rifle, scope and mount and all seemed to be in order. Then I found what I think is the offending part, the ammo. While doing some 2 shot drills and unload/reload I noticed that the loaded round I was ejecting from the chamber was bad.
It appears that the neck tension is not enough to prevent the bullet from being driven back into the case more than a quarter inch when it hits the feed ramp. In some cases I was able to wiggle the bullet with my fingers.
At some point in time I will run some of the ammo through a neck crimper and see if that changes anything. The day I sighted in my rifle I had been single loading so that is why this problem didn't appear earlier.
Luckily I had also brought along my Rem700 and just ran that through the school. If I had to buy my own ammo that would not have been my choice but like I said it was free. Lesson learned.
