Barrel Temps When Developing a load?

[Montana73]

I've searched all the past threads on breaking in a barrel and all discuss not shooting x shots before letting cool down. However, nobody talked in detail about temperature differences and cooling down on their barrels.

I shot my 7STW 26" barrel for the first time recently. (It has 100+ rounds thru it). I bought a IR temp gun and checked the barrel at start of shooting here in NC...it was 65 degrees. I would shoot 3 - 4 round groups, separating each shot by 2-5 minutes and temp on barrel settled around 77 degrees. If I shot 4 rounds, it would get to 80 degrees then settle down to mid-70's.

For you experienced shooters, bench rest or otherwise, what is your answer here? If I keep the temp between 65 and 80 degrees by separating my shots am I doing the right thing? Or does is need to get back down to 65 degrees? If so, that probably means 10+ minutes between shots is my guess.

Thoughts?

 

[elf]

I shoot in benchrest matches.We are required to fire 5 record shots (on the target) within 6 mins, and still within that time frame, as many sighters as we want. I always start with sighters, maybe 5 or 10 before I go to the bullseye. So in 6 mins, we put 10 - 15 downrange. Don't worry about the barrel temp. After the first few shot, they should all go in the same hole!!!

 

[dfanonymous]

I don't worry about it. I try to take out as much barrel heat for zero by waiting between shots, usually I fill my time wrighting in initial velocities and what not. but I usually end up confirming zero on a separate day all together, this is to make sure the cold bore is at as close to perfect zero as I can get it.

For PRS, contour matters in my experience. especially when using hot overbore cartridges. 10-15 shot strings in 90ish seconds, I wouldn't use anything less than a med Palma and generally use and prefer m24/40 contours. The idea is to prevent minimize poi and mv shifts as much as possible for the typical string of fire. For hunters, you should only need one shot.

 

[AZShooter]

I think a hunter should try and duplicate hunting conditions when developing a load. . Owning multiple rifles helps. I will work up loads for a particular rifle in similar temperatures that will be encountered while hunting. Iprefer

While shooting at the range, as you observed the barrel temperature quickly increases with multiple shots. I rarely shoot more than two shots with the big magnums and three with medium sized cases. I want the barrel as close to ambient temperature as possible.

I know a well known local gunsmith who will shoot one shot allowing barrel to cool naturally to ambient before shooting another shot. This becomes an all morning affair.

I prefer to accelerate the cooling time if I didn't bring multiple rifles or if time is a factor. There are many ways to cool off the barrel. If accelerated cooling is desired many run cold water across the outside of the barrel and some even run water through the bore! Naturally the bore must be swabbed out to remove all water.
Other shooters use a damp towel wrapped around the barrel.

Using forced air is far slower than using a liquid but less messy. Some use small air pumps that are used to inflate an air mattress. While I haven't seen it yet, a air compressor with higher flow would be faster. Fastest way to cool with air I know of and use myself, is to use a CO2 tank with a tapered hose to fit tight into end of chamber. Mild flow will cool a barrel to ambient temperature in 20 or 30 seconds. As barrel is cooling stop flow before outside gets to ambient as cooling will continue as the cooler inside radiates towards outside. I have used this system for well over a decade when time is a factor in developing a load. The 20 lb tank costs around $22 dollars to fill but will last several range sessions. Smaller tanks don't work.
We learned that there is no need to buy an expensive regulator, a ball valve will work just fine.

 

[milo-2]

I don't worry about it. I try to take out as much barrel heat for zero by waiting between shots, usually I fill my time wrighting in initial velocities and what not. but I usually end up confirming zero on a separate day all together, this is to make sure the cold bore is at as close to perfect zero as I can get it.

For PRS, contour matters in my experience. especially when using hot overbore cartridges. 10-15 shot strings in 90ish seconds, I wouldn't use anything less than a med Palma and generally use and prefer m24/40 contours. The idea is to prevent minimize poi and mv shifts as much as possible for the typical string of fire. For hunters, you should only need one shot.

I mostly agree with this. If your STW is used as a target gun, warm it up. If it is a hunting rifle and you really don't want to fire 3 warning shots before the kill, fire it cool.
The same principle extends to load development, develop for a target rifle the way it will be shot, ditto on a hunting rifle.

 

[lancetkenyon]

I always take multiple rifles to the range. I shoot 3 shot strings, then let cool back to ambient air temps, usually let them sit for 20-30 minutes. Barrel taper makes a difference.
Once load development is done, I zero to cold bore shot plus two extras. You should want to verify two follow up shots will hit the same POI as your cold bore for a hunting rifle.