POI shift

[Texas Solo]

My F Class 223 shoots very well at 600yds. But as the match goes on, it shoots lower & lower. After 10rds of a 30 shot in 30 minutes relay, it drops 1.5". The longer we go the worse it gets.
When cooled off, it's back to normal.

It's a #12 Savage in an aluminum bedded Choate stock. Schillen match 28" 1/7 barrel, 75gr Hornady ELDM, 24.5 gr Varget at 2800fps. Action screws are properly torqued.

Very frustrating that I can't find what's causing it. Any help appreciated.

 

[CharlieNC]

Its not unusual to find the recoil lug, especially an oversize aftermarket model, does not fit properly in the Choate. Dremmel the recoil space more open in all directions, tape the front and sides of the recoil lug, and bed it.

 

[Fuj]

What Charlie said about the lug. I'll go a bit further saying the Choate
does not like heat. I own one and use it as my fire forming stock for Savage
barreled actions. I've had the barrels hot enough to smell plastic. The
aluminum V block is not that big and not a lot of plastic holds it in place.
It's a noodle plain and simple and your barrel heat build up is most likely
softening and letting the lug area to droop. It sounds like you like to compete
and compete on a budget. So what I'm saying is to part ways with Choate and
find a decent piece of wood. I shoot Aluminum chassis if that''s your preference.

 

[Keith Glasscock]

I completely disagree. The stock supports the barrelled action. Unless the scope is mounted to the stock, you are wasting your time chasing that for this issue.

How do I know? After dozens of barrels in F-Open, from nearly every major manufacturer, I've had more than a few that warp slightly as the barrel heats up. The result is usually a dropping point of impact over time. The same rifle with a different barrel doesn't do it, so I know by process of elimination that it is the barrel.

The initial post said POI drops 1.5" and refers to 600 yards. If it is dropping only 1/4 MOA, that is a minor barrel warp. Personally, I just learn to "lead the dance", walking my aimpoint up over time. I've had good results with cryo in reducing it on a few barrels, but I don't think it's a fix-all.

 

[biggun2869]

I don't know but it is my belief that Keith knows what he is talking about and I don't think he would in any way lead you astray. Gary

 

[rardoin]

In my experience, a smaller diameter barrel will 'walk' more as it heats up. Like Keith said, learn to either shade your hold higher as a match progresses or make incremental dial-ups.

 

[glockaholic]

It sounds predicable so go with the flow. Don't be surprised if the next barrel walks up instead of down........even if identical specs.

 

[CharlieNC]

It could be the barrel, but the recoil lug resting on on the stock is a common problem for a Savage action in a Choate stock, and it is free to address. It's not really bedded, its an aluminum vblock that does not always provide adequate clearance for the recoil lug.

 

[STOMP442]

I completely disagree. The stock supports the barrelled action. Unless the scope is mounted to the stock, you are wasting your time chasing that for this issue.

How do I know? After dozens of barrels in F-Open, from nearly every major manufacturer, I've had more than a few that warp slightly as the barrel heats up. The result is usually a dropping point of impact over time. The same rifle with a different barrel doesn't do it, so I know by process of elimination that it is the barrel.

The initial post said POI drops 1.5" and refers to 600 yards. If it is dropping only 1/4 MOA, that is a minor barrel warp. Personally, I just learn to "lead the dance", walking my aimpoint up over time. I've had good results with cryo in reducing it on a few barrels, but I don't think it's a fix-all.

I agree. Add a click after 10 rounds and let er rip.

 

[Cfshooter]

I see the same with my Savage model 12 in 223. It is also probably about a 1/4 moa total drop as the string continues. It is pretty predictable and I just hold as needed as it walks.