Temperature and POI Change…?

[Full Curl]

Yesterday I grabbed my custom 270wsm out from the basement with a box of handloads and went to the range to shoot a few and foul the barrel for our local deer season in a few weeks.

I shot 5 shot strings at 100yds and 200yds. Very surprisingly vertical was off, I was 3.5 inches high at 100 and 3 inches high at 200. Horizontal was spot on still. Both groups were .5 MOA as this rifle has always been a tack driver. I previously had it zeroed for 200 which put it a hair over an inch at 100.

Haven't touched the rifle other than cleaning it since last year where it was spot on. I'll check the action screws and the scope mounts but a thought I wanted to ask the group…

The rifle and ammo were in my basement where it was 58 degrees. We had record breaking high temp yesterday of 74 degrees. I grabbed the rifle and ammo from the basement and was at the range 15 minutes later shooting in 74 degree temps. The rifle and ammo were cold to the touch, then were both placed on out on the bench in the sun. I know temps increase speed but could it be to this extent??

Rifle and glass are both high quality products.

Any thoughts? I found this very odd as it's never happened before but I've also never shot in such drastic temperature differences.

 

[The Oregonian]

What was velocity? Wonder if it could be cold welding with higher pressures and velocity.

 

[Tiny Tim]

What kind of temps was your original load development done in and are you near max loads? Powder type? Any chance you know if velocity changed. 3.5" @ 100 is huge, but a change in recoil or harmonics could account for that.

 

[Full Curl]

I didn't measure velocity, I had no reason to bring the chrony. If I don't figure this out I will be. Original dev was done in 55 to 65 degree temps. About 85% of max as far as load. H1000 powder so not very temp sensitive. Didn't notice any pressure issues while shooting yesterday. Just odd how horizontal was still spot on and only the vertical changed. Triple checked my loads to make sure I didn't grab the wrong ones. Even shot a couple out of different batches to be sure and they all grouped the same.

 

[Full Curl]

I never experienced cold welding before and don't know much about it. All rounds were loaded 2-3 years ago with 3 times fired brass and nosler bullets. Brass was wet cleaned with SS media and shoulder bumped a few thousandths. I use imperial case lube and a little might get in the case mouth which helps the expander ball. Maybe a very small amount is still in there when I seat the bullet?? Ammo is stored in my basement which is low humidity and temp controlled. None of my other calibers have experienced this??

 

[ButterBean]

I never experienced cold welding before and don't know much about it. All rounds were loaded 2-3 years ago with 3 times fired brass and nosler bullets. Brass was wet cleaned with SS media and shoulder bumped a few thousandths. I use imperial case lube and a little might get in the case mouth which helps the expander ball. Maybe a very small amount is still in there when I seat the bullet?? Ammo is stored in my basement which is low humidity and temp controlled. None of my other calibers have experienced this??

I would agree on the cold weld with that big of a swing, take some loaded rounds and seat the bullet a tad deeper all you need to do is move the bullet to break the cold weld

 

[The Oregonian]

Given it was 2-3 years and SS cleaning I would sure investigate cold welding before anything else. I would load some new ones with the same load and compare those to the older rounds with a chrony.

 

[JMW67]

sounds like your scope creeped a little, could be cold weld but I would think the groups would not have been so good Adjust your scope and shoot again since you notice no signs of pressure

 

[Tiny Tim]

Any chance there is a pressure point in your barrel channel?

 

[Bob Wright]

Nice experiment ready to try. Bring 5 as is and 5 re-seated a few thou. Shoot them and see what happens.
Let us know. Definitely over a chrono.

 

[BrentM]

That's a big jump for velocity and really, velocity doesn't have as much to do with it as people think. It is really harmonics when the bullet exits the barrel will determine where it lands. I have had very slow FPS in a test load that hit higher than faster loads at short distance. Ladder testing for example really needs to be done 300 min and I prefer 500 so that you can experience clusters in a more vertical fashion, but even then faster loads can sometimes impact within the same basic area as slower loads.

I'd probably just rezero since it is an accurate load and then verify the load data at longer range. I would suggest breaking the weld as others mention for peace of mind.

 

[Tiny Tim]

I never experienced cold welding before and don't know much about it. All rounds were loaded 2-3 years ago with 3 times fired brass and nosler bullets.

From what I've read, cold welding seems to happen relatively quickly. If they are 2-3 years old and worked fine last year, I'd look elsewhere. Nothing loose or got bumped/disturbed?

 

[RYEWSKY25284]

Yesterday I grabbed my custom 270wsm out from the basement with a box of handloads and went to the range to shoot a few and foul the barrel for our local deer season in a few weeks.

I shot 5 shot strings at 100yds and 200yds. Very surprisingly vertical was off, I was 3.5 inches high at 100 and 3 inches high at 200. Horizontal was spot on still. Both groups were .5 MOA as this rifle has always been a tack driver. I previously had it zeroed for 200 which put it a hair over an inch at 100.

Haven't touched the rifle other than cleaning it since last year where it was spot on. I'll check the action screws and the scope mounts but a thought I wanted to ask the group…

The rifle and ammo were in my basement where it was 58 degrees. We had record breaking high temp yesterday of 74 degrees. I grabbed the rifle and ammo from the basement and was at the range 15 minutes later shooting in 74 degree temps. The rifle and ammo were cold to the touch, then were both placed on out on the bench in the sun. I know temps increase speed but could it be to this extent??

Rifle and glass are both high quality products.

Any thoughts? I found this very odd as it's never happened before but I've also never shot in such drastic temperature differences.

 

[RYEWSKY25284]

you had mentioned that you checked your actions screws and scope mount??!!
I would say that "IF" you changed the torque in ANY way on either of those attachment points, I guarantee you have changed your POI..... Been there.Done that.
The good news, readjust scope-done.
For me, once I'm done with load development and have the rifle dialed in, I don't touch anything again.
If I notice the accuracy is falling off, then I will start looking at touching screws..

Best Regards
Steve C