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Cold bore shot always a little slower

B muzguy

Is there a secret to get the first shot.. cold bore .. to the same velocity as the next shots out of your rifle?

For instance 2889 first shot. All the rest are 2917 roughly, but they all go in the same hole at 100 yards. I know at distance the first shot will be low. So do I just aim a little high or put .2 grains more powder for the first shot?
 
There is no secret to getting a "Cold-bore" shot to match groupings after a barrel "warms" , as virtually every barrel ever made will change , allowing velocity to change .
 
The parameters to play with are the cleaning intervals and how long you wait between tests. The climate conditions can change between time lapses and range sessions, so you will also have to learn the study of external ballistics and the effects of atmosphere In addition to your internal ballistics and hardware.

If your pre-fouled gun will shoot accurately when truly cold, then the issue is how it may do if it needs a follow up shot. When we are very lucky, all shots go into one group. A gun that won’t means you have to understand the limits and move on if those don’t suit your needs. But you have to be patient and honest with the testing to know if your cold bore shot is on the marks.

I have had my fair share of stock and scope issues to debug and have had rigs that were too easy and others that took hard work. It takes lots of range sessions in weather to know if you can reliably place an accurate cold bore shot under stress and in variable weather. Best if nobody is going to be shooting back...
 
For hunting the focus should be on cold bore accuracy(not velocity).
And for this you're not going to learn a lot at 100yds(unless a 12ga squirrel hunter).

You could add more powder to get a goal velocity, with little change at 100yds, but you'll need to learn about the affect at your max hunting shot distances.
This is where cold bore development comes in, which most shooters (even hunters) never do.

After working up a hot load based on precision, I move to cold bore accuracy. These are completely different animals for many guns.
I do this at my worst range (200yds) at a shot rate that has so far proved worst for all barrels & cartridges I've dealt with (1sht/10mins). I'm one of these people who shoot tighter moa at greater distances. I think it's an optical issue.. I do this exactly as I shoot in the field, off a Harris bipod in the dirt.
I keep ammo in my pants pocket to normalize it's temperature, and the development is for either summer or winter loads(no such thing as universal). My barrels are always dry pre-fouled before I begin a session, and I don't shoot near enough shots in a session for fouling change to affect results.
All I'm adjusting is powder charge.
With 3 or 4 shots on a 1" bullseye (1/2hr session) I have a result better/worse.

This takes time & discipline, and you have to be brutally honest about your system potential, proven as you go.
You may find as I have, a great grouping gun with no real potential for hunting. You can also find just the opposite, a terrible grouping gun that is very accurate, maybe from first couple shots.
So given the potential efforts in this, the first test I do, using my hot load, is purely to see how sensitive the gun is to a barrel warming up. Every 10mins I'll shoot 2 quick shots on target.
-If the 2nd shots are grouped well but the 1st shots are walking all over badly, the gun has zero potential for hunting. Don't waste further efforts on that.
-If the 1st shots are grouped, but the 2nd shots are walking a bit, now you've got something to work with.

An example; I loaded up some new 6XC brass with a great hot load worked up earlier.
I'm gonna fire form the cases and see right off the bat if my tube gun was worth cold bore development. I had over $5K invested in the system with intent to use it for groundhog hunting,, but this result killed the whole show. I sold it all a couple weeks later..
6XCgrpSSM.jpg
 
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Keep a separate record over time of both your cold and clean barrel shots.

This is easy to do. Place a blank target behind the target your using during a range session. After the first shot, remove the rear target and label it i.e. clean or cold barrel shot. Reuse the appropriate rear target each range session in the same manner. After about 15 to 25 range sessions you'll get a good idea of your rifle's clean and cold barrel potential - as the saying goes - a picture is worth a thousand words.

If you want more information. Number each shot and record the temperature and wind conditions. For the clean barrel target, record any pre-range session conditioning of the bore, i.e. dry patched, etc. One technique that has worked for me is to run a patch of mineral spirits down the bore to remove any lube then dry patch the bore. In most of my rifles, this cuts down on clean barrel flyers.

For a long range precision hunter, cold and clean barrel performance information is very useful - even critical because if you miss the first time you may not get another chance.
 
That slower first [cold bore] shot does not necessarily have to print "lower" at all distances. It certainly can, but the muzzle launch angle when it exits the bore is also part of the equation as to how high it prints relative to the slightly faster shots. IMO - it would be a lot easier to determine an average relative point of impact of that first cold bore shot relative to the average POI of the other shots, and then simply adjust using the scope turrets than it would be to keep track of rounds loaded with a different charge weight.
 
B muzguy said:
Is there a secret to get the first shot.. cold bore .. to the same velocity as the next shots out of your rifle?

For instance 2889 first shot. All the rest are 2917 roughly, but they all go in the same hole at 100 yards. I know at distance the first shot will be low. So do I just aim a little high or put .2 grains more powder for the first shot?
Click to expand...
Most barrels are like me. It takes my old bones awhile to get going. Tommy Mc
 
I shot my .223 bolt gun last Sunday. Temp at noon was 45°. I shoot 5 warm ups using some of my AR loads. Then I start shooting my precision loads. Both me and the rifle are ready after 5 warm ups. In the summer, it only takes 2 to warm up.

PopCharlie
 
Barrel warmer might help.

Used to race remote control cars on pavement and had electric tire warmers so we could hit the track using full power. Used on indoor carpet racing too.
 
mikecr said:
The OP is concerned about his cold bore shot.
Is your solution to not be concerned with cold bore shots?
Click to expand...

Yes. Literally, could warm the barrel.

Other possible solution include applying collodial graphite suspended in a denatured alcohol as a base.

Or HBN or Danzac.
 
mikecr said:
The OP is concerned about his cold bore shot.
Is your solution to not be concerned with cold bore shots?
Click to expand...
I shoot warm ups because I am concerned about cold bore shots. In my rifles, the cold bore shots tend to be slower and shoot a little high.
PopCharlie
 
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