Cold Bore shot.

[possum]

How much does a cold bore shot on a precision rifle affect your poa/poi, and why/ how does it?

also say for example that you wanted to get mulitple cold bore shots in one range session, how long between shots should you wait to get the barrel as close to cold bore as possible? 10 minutes 15 etc?

thanks

 

[Gingerbreadman]

I don't know definate figures, but I have heard of people zeroing in a rifle cold bore by shooting it once a day.

 

[hossdaniels]

I have a smokeless muzzle loader, that needs to cooled all the way for the plastic sabots to keep their rigidity, takes about 15 minutes between shots at 50* if you are shooting for groups. I dont think a sporter sized barrel would take that long. With my 270 a-bolt I take 2 shots at a time, the third one is the consistent flier. Its usually fine time I walk to 200 yd target and back.

 

[UnTainted]

on my 30-06 i give it about 20 to 25 minutes between shots to get my cold bore group sighted in for hunting.

Go to handguns or another rifle while waiting for it to cool down. The average distance I've seen it move my group was between .5 to 2 inches in no wind.

This year I shot my elk twice, both shots going through the same entrance hole, both shots exactly where I aimed them behind the left shoulder. The second shot was fired immediately after the first. I would say sight it in cold bore, but don't worry too much about it while in the field for second or more shots unless you're firing out past 500 yards. If you do, practice those ranges with cold and warm shots to see how it affects YOUR gun (each gun acts differently depending on the bull-ness of the barrel, its legnth, floated or not, caliber, bullet, etc...

I think more important than the cold bore shot or sighting it in cold bore is to make sure after you clean your rifle, that you fire it once for the fouling shot. That has created 2 to 3 inch differences in my rifle at 200 yards (more than the cold bore difference).

 

[jlmurphy]

It is easy to see if your first shot from a cold bore is in the following group. The internal ballistics of the barrel are complicated, but testing is easy. I have mostly heavy barreled rifles and most put the first shot in the group, I usually leave Kroil penetrating oil in the bore and patch the barrel before shooting. I have heard some benchrest shooters use Loc-Eze, a graphic lock lubricant to precondition the barrel before shooting. As far as cold barrels, once it cools to ambient temperature, it's cold. You can even use forced air, CO2, or even water to cool the bore ( be careful ), you don't have to wait a day.

 

[Jenrick]

The main difference is going to be between a cold clean bore and a warm fouled bore. A cold fouled bore is usually pretty close to a warm fouled bore. A good log book will help you determine exactly how much of a difference, and where. It's different for every rifle, so it's best to chart each rifle separately if you really want to know.

As to how big a difference it really makes, it really depends on what exactly you're trying to shoot. Minute of deer it really won't matter, hostage rescue or bench rest it'll make a difference.

The easiest way to get a good cold clean bore zero is to use the same target every time you go shoot. Fire your first cold clean round on it with the same POA, and then put that target away. Do that multiple times to get multiple groups. I've found my Rem 700P shoots approx .5" right and .75" high on a cold clean bore with my preferred ammo, compared to a fouled bore (either warm or cold).

As noted above cold fouled bore is easy, just give it time to get back to ambient, say 15-20 minutes tops.

-Jenrick

 

[atblis]

Yeah

Depends on the rifle. Mine doesn't vary much, but I don't get it very hot. I'll fire at most 5 shots in a row. I usually wait 20 minutes.

Now, there's a huge difference between clean and fouled. Only take 1-2 shots to settle in though.

 

[351 WINCHESTER]

For my hunting rifles I fire 2 quick shots to simulate a follow up if necessary. No need to fire 5 shot strings unless you're punching paper or just want to get familiar with a new rifle.

 

[W.E.G.]

Unless there is something "wrong" with your rifle, I'm with the a-fouled-barrel-is-a-fouled-barrel crowd.

If the gun is shooting the first shot from a clean, cold barrel "outside the group," how far outside is it?

One inch?

You know, for hunting, and for a lot of other scenarios, one inch just doesn't matter.

If you've got a gun that "walks" the group badly as it heats up, you might think about getting your hands on a better rifle if its to be used for precision shooting.

 

[rangerruck]

there was an excellent article on cold bore shooting a few months ago in Shooting times, i think. Author used about 10 diff rifles, bolt, semi, lever etc. and tried several diff things there is cold bore, cold bore for about 30 mns or more, cold bore for a week; there is cold bore not cleaned, cold bore, cleaned, cold bore cleaned and left for a week , cold bore not cleaned , left for a week.
to put it shortly , the best results , with poi , poa, shift, etc., occured with a cold bore, cleaned, left alone for a day or more. two of his test rifles, a savage varminter, and a ar type in 243, hit predictably / exactly the same place, each time he cold bore, shot, cleaned, and left for over a day. he tried some after an hour, but apparently , there is still something deep in the molecules going on , in all the metal parts, in a rifle, that we just can't see, becuase the shots after an hour, though close, were not the same as the ones left cleaned for over a day.
also a winny 94 gave him some real good results, and a boltie 7mag from Weatheby or howa did real well. The worst was a Ruger, and another rifle, whose shots, no matter when shot were total shotgun, completely unpredictable, any time you shot it.

 

[possum]

thanks for all the info guys!

ragerruck, thanks i will have to check that aricle out.