Barrel heating question

[BCRider]

Pretty new to rifle shooting and recently I've been trying to set up a TC Encore in 7mm-08 for some target shooting and perhaps steel silhouette shooting. Now I know this hardly fits in with fractional MOA stuff at 500 yards but my question is about general trends of barrel warming and why the POI drifts in some (most? all?) cases.

I noticed while sighting in my scope I seem to be chasing the POI as it constantly climbs. Then I remembered about the whole warm barrel thing and took a break for a few minutes. The POI had dropped about 3 inches at 100 yards just from this short break. Up until then I'd been having to lower the scope setting every shot without apparent change. During this time I'd been shooting about one round in 45 seconds to a minute. The cooling down break was around 4 to 5 minutes.

Is this a built in issue of some sort or could it be the way the TC Encore fore end is screwed to the barrel in two spots? Is it something that is related to the heat treating of the barrel that can be tempered out of the steel via some controlled heat cycling of some sort? Or have I just got a nice hunting rifle and should stop right here?

I'm not going to go crazy on this gun but it would be fun to take it a little ways down the optimizing highway to see how well both it and I can shoot. I'm going to get a press fit front pin and a tighter locking key spring to seat the barrel more solidly in the frame. I've done the spring tweaking and action polishing already to drop the trigger pull down to the 5'ish lb range and will likely tweak it to a lighter 1.5 to 2'ish lbs. There'll be a few other things to check but for now this whole barrel heating and shot pulling is something I'd like to learn more about.

 

[Obtunded]

All barrels are manufactured with some degree of latent stresses. The manufacturing processes determine the degree of stresses, with hammer forged and button-rifled barrels being the worst.

Manufacturing does include a process of stress relieving, but no barrel is completely stress-free. This means that when the barrel is subjected to any influences that change its dimensions such as fluting or heating, these barrels will change shape. In the case of fluting, it can be permanent, or in the case of heating, it is transient.

A shifting POI with a heated-up barrel is often indicative of its dimensional changes from either an inconsistency in the steel's homogenicity or some latent stresses.

It is very common in factory barrels, particularly barrels of a lighter contour. Benchrest and F-Class shooters use as heavy a contour as they can get away with to minimize the effects of shifting POI's as a result of heating. Others buy into the belief that cut rifled barrels have less latent stresses. Generally speaking, a top quality match grade barrel is supposed to mitigate the liklihood of this being a problem, but not always.

SHifting POI is the rationale behind having a zero for a "cold bore shot" with "sniper" weapons.

 

[Mystic Precision]

It is very common for factory barrels to walk or warp as they get hot. My understanding is that little stress relieving is done. Certainly, what is done is not always adequate - but that costs $$$

Match barrel from all top line makers are stressed relieved to a point where the manf see little warping due to heat as it applies to their sport/discipline. A good quality match barrel can shoot sub MOA groups even when too hot to touch - not good for barrel life but an indicator of how well it was produced.

In the case of your Encore, is the climbing POI repeatable and predicatable. If it is, then you have a barrel issue and there is nothing much you can do to change this. some has suggested cryo treatment but have not done it myself and I think it was only offered in the US anyways. Not even sure if it is being offered anymore????

If there is a change but varying, then you might an issue with how the barrel is installed and the lock up of the frame vs barrel. Tightening it up will prove beneficial no matter what.

Break open single shots are rarely used in competition because of all the variables that are introduced that can affect accuracy. A change of barrel can help as the new one may be less prone to warpage???? I can offer you alternate barrels.

Let us know how your testing progresses.

Jerry

 

[BCRider]

Thanks guys, I appreciate the answers you posted.