Do you think glass bedding might help my temp related verticals (6PPC)?

[GJgo]

Hey All,

I have a Sako 75 in 6PPC-USA that I love to shoot. It's 100% factory with the trigger at a crisp 1lb. Last year I did my first ever match with it, just to see how we'd do, and I shot a grand agg (25 @ 100 and 25 @ 200) of .5" using a bipod, a sandbag, and a metal folding chair. (still working on both my shooting and my equipment!) So, for a first time, I think I did pretty well and look forward to getting better with practice and experience. (I know I'll never win BR with this rig but I enjoy the competition and the comaraderie..)

So, here's the issue. When the barrel is cold, the gun shoots high for 3-4 rounds. As it warms up the POI tracks down, and after 4 rounds or so when the barrel is up to temp the POI stays rock solid and doesn't shift as the barrel heats up further, even with 10-15 shot strings. (Not that it ever really gets that hot with my Benchmark load, but it did when I tried some Varget.)

So, when I did the competition, I ended up spending my low shots as warm-up rounds instead of using them as intended- to judge the wind, etc.. They were esentially useless in terms of gaining information before going upstairs and running the string.

So, is this a scenario that anyone has a known fix for? Ideas or suggestions such as glass bedding? I don't mind one fouling shot, but 3-4 seems excessive.

TIA

 

[jlmurphy]

It sounds like the barrel has unrelieved stress issues. It wouldn't hurt to bed the action and free float the barrel, but precise movements like that usually indicate the steel in the barrel is expanding at an uneven rate when heated. If you have a solid surface and clamps, you can secure the bare action and pour hot water through the barrel while monitoring the muzzle with a dial indicator. I did this with a barrel that would move 3" when hot, the indicator showed .018" movement, which extrapolated to 3" at 100 yds. There is no easy fix, hot stress relieving would probably ruin the bore finish, and there is no guarantee the barrel dimensions wouldn't change, the jury is still out on cryogenic stress relieving. It might be getting hot between the barrel and the stock, you might try increasing the clearance.

 

[GJgo]

Thanks, I never thought of that. The barrel is fully floated all the way back- enough so that there is no chance of touching, at least from how it would seem to me..