Cold Barrel Shot Testing

[Ehunt]

I am wanting to do Cold Barrel shot testing. How long should I wait in between shots for the barrel to cool off enough to produce another "cold barrel shot?"

[Capbyrd]

Get yourself one of those infrared thermometers and check the temp inside the bore.  When it's back down close to ambient, you are ready for the second shot.   Also be sure to clean the bore between rounds. 

[Omega]

I usually only wait 5, maybe 10 minutes between shots, after I've zeroed my rifle.  I've never had to adjust to the cold shot though, they've always been close, so far.  That's a good idea for the laser thermometer though, hadn't thought about using it for that.

[jpx2rk]

Could just take a 2nd firearm to shoot while you wait for the other one to cool down.  I usually take a 22RF in these circumstances, takes 5+ minutes to set up the 22RF, load it and shoot it for a few minutes, put it aside and go again on the cold bore testing.  Repeat

[xtriggerman]

I'm not sure what your after. In a properly bedded barrel, the average hunting rifle should hold a group with the first shot consecutively. The factor that more often than not determines POI off a cold barrel is to have a some what freshly fired bore vs a cleaned bore. Powder residue contains graphite. Ultra light barrels along with extra long barrels put a lot of value in a perfect bedding.  Basically, if the barreled action is bedded right, the first 3 shots threw a cold barrel should not have much variation. After that, barrel weight and cartridge powder capacity will be the spread contributors as you apparently all ready know. 

[Navy Chief]

I run into a similar issue when I load test a new round. Basically, I fire one round of a known load for a "base line POI", dry patch the rifle, walk to the target to mark the shot (200m), and walk back. By the time I get back to the bench the barrel is within 10 degrees of cold temp and I start with my test string using the same technique for each round. I typically shoot 8-12 test rounds loaded in 1/2 grain increments and at the end of the string the barrel is never more than 30 degrees warmer than when I started. At the end I fire one more round of the original known load to verify POI hasn't changed and I'm done. I have found that (in my rifles at least) there is no measurable change in POI between the first "base line" round to the last POI verification round.

Now having said all that, I'm an old codger so it takes me about 5-6 minutes to walk to the target and back, you young whippersnappers probably just run it in a minute or two! Seriously, five minutes between shots will be plenty of cool down time unless you are leaving the rifle in the hot sun on a hot summer day.

[Ehunt]

On 12/6/2018 at 10:59 AM, xtriggerman said:

I'm not sure what your after. In a properly bedded barrel, the average hunting rifle should hold a group with the first shot consecutively. The factor that more often than not determines POI off a cold barrel is to have a some what freshly fired bore vs a cleaned bore. Powder residue contains graphite. Ultra light barrels along with extra long barrels put a lot of value in a perfect bedding.  Basically, if the barreled action is bedded right, the first 3 shots threw a cold barrel should not have much variation. After that, barrel weight and cartridge powder capacity will be the spread contributors as you apparently all ready know. 

I'm just trying to test to see what the deviation from cold to warm shots will be. My Stainless .223 Wylde AR-15 has about 1.0" - 1.5" deviation from cold to warm shots (all shots thereafter are very good at 0.50" or less). I just built an AR-10 in .308 Win with a Faxon Nitrite barrel; I am hoping the "cold shots" will end up being a lot closer than they are with my AR-15.

On my AR-15, I was using Iron Sights at 25 meters on an M-16, 300 Meter Zero Target I was getting around 1.0" to 0.30" groupings from my 1:8 SS .223 Wylde 18" barrel. Widest group was with 55 grain ammo Norma Tac Ammo, and the tightest group was with 69 grain PPU Match ammo. 75 grain seemed to be less accurate, but that is probably my bad eyes. It was an indoor range and poor lighting with my astigmatism eye balls... so I think I need some kind of optic to shoot more consistently.

I just bought a 4-14x44 ACSS Scope from Primary Arms. I am hoping this will help also.

Edited December 10, 2018 by Ehunt

[Ehunt]

On 12/5/2018 at 7:14 AM, Capbyrd said:

Get yourself one of those infrared thermometers and check the temp inside the bore.  When it's back down close to ambient, you are ready for the second shot.   Also be sure to clean the bore between rounds. 

Man! I wish I could afford one!

[Capbyrd]

4 minutes ago, Ehunt said:

Man! I wish I could afford one!

Grab one of these from harbor freight.  

https://www.harborfreight.com/catalogsearch/result/index/?dir=asc&order=EAScore%2Cf%2CEAFeatured+Weight%2Cf%2CSale+Rank%2Cf&q=thermometer

[Ehunt]

1 minute ago, Capbyrd said:

Grab one of these from harbor freight.  

https://www.harborfreight.com/catalogsearch/result/index/?dir=asc&order=EAScore%2Cf%2CEAFeatured+Weight%2Cf%2CSale+Rank%2Cf&q=thermometer

Cool! Thanks!

[Alleycat72]

On 12/5/2018 at 7:14 AM, Capbyrd said:

Get yourself one of those infrared thermometers and check the temp inside the bore.  When it's back down close to ambient, you are ready for the second shot.   Also be sure to clean the bore between rounds. 

Clean? What?....

Only clean when the accuracy goes away. Some of my guns go 250ish rounds before I clean the barrel. One goes closer to 400. A clean bore will shoot a different POI than a fouled bore.

[Capbyrd]

10 hours ago, alleycat72 said:

Clean? What?....

Only clean when the accuracy goes away. Some of my guns go 250ish rounds before I clean the barrel. One goes closer to 400. A clean bore will shoot a different POI than a fouled bore.

The purpose of "cold bore testing" is to find out the POI shift.   That isn't just about temperature, but rather, like you said, the combination of a clean bore and temperature.  So if the OP is trying to figure out his POI shift from a cold bore, he should also take bore fouling into account as well.  

[Alleycat72]

2 hours ago, Capbyrd said:

The purpose of "cold bore testing" is to find out the POI shift.   That isn't just about temperature, but rather, like you said, the combination of a clean bore and temperature.  So if the OP is trying to figure out his POI shift from a cold bore, he should also take bore fouling into account as well.  

A fouled bore is more consistent. A better practice is to shoot your cold bore shot with a fouled bore and log that. When you clean the barrel always foul it before putting it up. Your cold bore shot will have much less deviation.