Anybody experience a cold bore shift? I'm wondering if it's the quick change screw torque value. I havent tried bumping it up. Had a match yesterday (1st with the AI) and I had a consistent .3 low cold bore shift for 1-2 shots then it was back dead nuts. Any ideas?
Cold bore shift on AI/AT
- Thread starter BLKWLFK9
- Start date
I noticed something like this last winter. My theory was that the colder temps shrunk the barrel and action ever so slightly so that the first shot ended up slightly off. Follow on shots went back to the POI I was expecting. So I ended up chilling the barrel and reinstalling it. Since then I haven't had a problem.
I tighten to 6nm (53 in/lbs) and don’t notice any thing abnormal.
When I was using my wheeler torque driver at 49 in lbs I did seem to have the first round or 2 hit a hair low after removing and reinstalling my barrel. Since picking up a dedicated 6nm torque limiter and some fix it sticks I haven’t noticed anything odd.
The cold bore I was getting in the past could have been me or possibly the wheeler torque driver not being very accurate. A little extra torque shouldn’t hurt anything.
When I was using my wheeler torque driver at 49 in lbs I did seem to have the first round or 2 hit a hair low after removing and reinstalling my barrel. Since picking up a dedicated 6nm torque limiter and some fix it sticks I haven’t noticed anything odd.
The cold bore I was getting in the past could have been me or possibly the wheeler torque driver not being very accurate. A little extra torque shouldn’t hurt anything.
I would not have thought this could possibly be a thing until last week when I was at the range. I wanted to switch from my 6.5 CM barrel to go back to a .308 barrel for some handload testing. I have an HRD gear tenon thread cap and had hand tightened it immediately after removing the barrel the last time I was at the range. I had done several strings of suppressed fire and the barrel was uncomfortably warm when I put it away. Well, last week when I went to remove the cap, I could not get it off without the help of a friend holding the barrel to get two hands on it. Apparently, heat shrinkage is enough to clamp a hand-tight cap hard. Maybe it effects the fit when we just swap barrels?
I have always just hand tightened mine and have never seen a cold bore issue.
My AIAE mk3 I used to have...that was a different nightmare.
My AIAE mk3 I used to have...that was a different nightmare.
I might be misunderstanding what the OP is asking.... are you saying you observed a cold bore impact that was not where it normally was? With my AI and the 308 win barrel that I use for work, I have a repeatable .2 mil low x .05 mil right cold bore impact. I’ve documented this over the last 1800 rounds and depending on the lot of ammo were using, it’s always around that area. My follow up shots stack in the center of the “x”. I have other bolt guns that shoot dead nuts from cold bore until the barrel is too hot to touch, and I have a couple with predictable / repeatable cold bore shots. Each rifle / load has a personality. I change the barrel on my AI AX on a weekly basis and always torque to 55 in lbs. a couple weeks ago I forgot my adjustable torque wrench and only had a fixed torque seekonk t-handle wrench set at 49 in lbs. The cold bore, follow up shots and impacts from that day were identical to the weeks before and the weeks after with the barrel torqued to 55 in lbs.
Just my experiences.
Just my experiences.
Also let me be clear. I'm not talking ab a shift after swapping barrels. That I would expect. I'm talking about a traditional cold bore shift. In the match this weekend, I had to aim .3 high on the first shot of each stage. As the day got warmer (91deg), the barrel would be hot as shit without shooting it due to ambient air temps and the shift would go away. If i were to pull the rifle out right now and shoot, the 1st shot would be .3 low, the 2nd would be .2ish low, 3rd would be dead nuts. I'm trying to remedy this.
