Coldbore shots

[Velvet]

Hi guys.
How long between shots should I wait to simulate a coldbore shot? That is, after a sequence of shots, I would like to leave the weapon at rest until it returns to its original state. I have seen that both the POI and the speed between the coldbore and the second shot vary. My idea is to place a target and shoot several coldbores, to see variation of group and speed in relation to the second shot.
I thought about measuring the temperature of the barrel before doing the coldbore, and after each run, wait for it to cool down to that temperature. But maybe we have to wait longer, hence the doubt.
Any advice, much appreciated.
Best regards.
V

 

[Rich Coyle]

Get an infrared thermometer for about $12 - $20. Check the barrel before you start. Let it cool to that before starting again.

 

[memtb]

There are a lot of potential variables....ambient temperatures, barrel mass, amount of powder burned, ect. Usually 3 minutes or so should be adequate. However, to be certain.....purchase an "infrared temperature" gun ( can be had for under $50), allow your rifle to obtain ambient temperature, measure your barrel temperature prior to your first shot. Then after each shot, continue measurements until the barrel reachers near the original temperature. That may be a bit extreme, but, then there are no questions! As a plus the "temperature gun" has many uses elsewhere! memtb

 

[Velvet]

Okay. I will buy one to try.
What do you think of those who use thermocouples attached to the barrel?
The correct process should be to let the rifle take room temperature, measure barrel temperature before the first shot, and after the shots, wait for it to go down to that same level.
Perhaps we would have to wait for the barrel expansion / contraction processes to end.
I have no problem waiting an hour if necessary.
Thank you.
V

 

[CVCOBRA1]

Having two or three guns with you at the range helps a lot. Keeps you from getting in a hurry to find that cold bore POI.

 

[Rich Coyle]

One can get a lot of Bible reading done while a barrel cools.

 

[jreagle]

my guess is an hour or 2 for the inside of the barrel to match the ambient air temp. The only cooling provided is the ambient air temp itself for the barrel, cooling mostly from the outside to inside. One of those barrel cooling fans will help a lot. A probe stuck in the throat of the barrel after removing the fan would help determine how fast it is cooling.
Sounds like a fun experiment for a range day this fall....

 

[Velvet]

my guess is an hour or 2 for the inside of the barrel to match the ambient air temp. The only cooling provided is the ambient air temp itself for the barrel, cooling mostly from the outside to inside. One of those barrel cooling fans will help a lot. A probe stuck in the throat of the barrel after removing the fan would help determine how fast it is cooling.
Sounds like a fun experiment for a range day this fall....

I think one hour should be enough, especially since it would be only two shots, one for each target (coldbore and second shot). With 20 shots, half for each target, we should have a reliable statistical sample, both to see variations of the POI and muzzle speeds. 10 hours of sacrifice

 

[KyCarl]

Since cold bore is what you have hunting we play a game at deer camp the day prior to opening day. We each slap down 20 bucks set up a target at 200 yards.
Everyone gets 1 shot from the rifle he's going to hunt with any way you want
offhand... kneeling..your choice.Closest scoops up the cash AND gets his choice of stands opening day! Some hot competition!

 

[sable tireur]

I think one hour should be enough, especially since it would be only two shots, one for each target (coldbore and second shot). With 20 shots, half for each target, we should have a reliable statistical sample, both to see variations of the POI and muzzle speeds. 10 hours of sacrifice

The time required to reduce the rifle temperature to ambient gets longer the closer you get to ambient because of the smaller differential between the two. It's not linear. You actually have to get the air around (or in) the rifle cooler to get it to ambient faster.

That's why when you're testing and shooting groups, a fan or other cooling appliance or technique is extremely helpful to condense the time. I've known some folks who keep the AC on in their truck or car to speed up the cooling process. Place the rifle inside then go shoot another while the first is cooling.

 

[Velvet]

Since cold bore is what you have hunting we play a game at deer camp the day prior to opening day. We each slap down 20 bucks set up a target at 200 yards.
Everyone gets 1 shot from the rifle he's going to hunt with any way you want
offhand... kneeling..your choice.Closest scoops up the cash AND gets his choice of stands opening day! Some hot competition!

a lot of pressure!
Then, it is worth doing the cold bore shot test and POI variations.
Currently, the tests are for 300winmag with 220gn ELDX, and 73.5gn of H1000, CCI250. The first tests showed me an approximate horizontal POI variation of 0.5 MOA at 100y, and about 50ps less speed.
The rifle shoots sub moa consistently.

All this job, is because I want to define precisely, the POI of the coldbore, to leave the riflescope calibrated for that shot.

 

[Velvet]

[QUOTE="That's why when you're testing and shooting groups, a fan or other cooling appliance or technique is extremely helpful to condense the time. I've known some folks who keep the AC on in their truck or car to speed up the cooling process. Place the rifle inside then go shoot another while the first is cooling.[/QUOTE]
Good idea!!!

 

[Rshooter]

Purchase a ( Chamber Chiller ), they work great and speed up the cooling process.

 

[Velvet]

Purchase a ( Chamber Chiller ), they work great and speed up the cooling process.

Great!!!