Barrel Heat Affecting Accuracy

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Rohann

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Hi all,
Well I saw this in "Battle Rifles" so I figured I would start one here.
How much does barrel heat affect accuracy? Would you notice a difference in accuracy if you made sure to fire cold?
E.g. it's 15 degrees, no wind. Would there be a difference between firing 1RPM and 1RP/3M?

-Rohann
 
As a barrel heats it begins to expand and distort,depending on the design of the barrel it will be affected to a different level. Keeping the barrel as close to a consistant temp. as possible is always going to aid in accuracy.
Some data indicates that once the barrel reaches a certain temp the amount of heat generated by firing and lost by cooling between shots reaches an equalibrium and accuracy will be improved.
 
Oh ok. So theoretically, the rifle will always be the most accurate cold, but it varies from rifle to rifle? I found (for my third shooting session anyway) that my cold-barrel shot shot slightly left of wherever I was aiming (could have been to do with my shooting or the ammo though).
What ROF seems to work best for you guys?

-Rohann
 
log every shot you make ,call it,shoot it, place it, keep track of your conditions,

I have three range cards spring/fall,Summer,Winter


Jamie
 
Jamie said:
log every shot you make ,call it,shoot it, place it, keep track of your conditions,

I have three range cards spring/fall,Summer,Winter


Jamie
Click to expand...

That sounds really boring.

I have found my Mauser to shoot VERY accurately with a barrel that scalds your fingers if you touch it.
 
Oh ok, will do. I haven't been logging that many details, just what range, what ammo, what temperature. I'll start logging detailed though, as I'm actually starting to reload now.

-Rohann
 
In "real world" situations, the rate of fire may well be determined by factors other than the whim of the shooter. If you are shooting in a match there are time limits. If you are in the gopher patch, the gophers determine the rate of fire! If you hunt like I do, the rate of fire for your hiunting rifle is once every couple of years and that likely a miss!
In practice you can mess around all you want between shots and strive to never let your barrel get warm. This might not result in better targets. When shooting "F" class in Canada, we usually shoot alongside the TR shooters or at least shoot a similar course of fire so shots are 1-2 minutes apart. In the states it is common to shoot strings so the shots may be seconds apart to try and get the shots off in the same condition. Obviously, most feel managing the conditions is more important than regulating barrel temperature.
The same sort of thing is true in BR competition. I've seen guys fire 15 or more shots during the 7 minute time allowance when using a lot of sighters to verify conditions. Again, there is virtually never any consideration given to moderating the rate of fire to regulate barrel temperature.
Now, this is not to say that individual barrels might not perform better cold. Also, it makes a certain amount of sense to try and test a hunting rifle cold. After all, that is how it is going to be used in the field. There will be no sighters and, if the first shot is a miss, it's likely the follow up will be the same. Regards, Bill
 
Once I zero a rifle with a good load I go through a shot sequence similar to a match heat.

Every round is plotted in the log book,so I can reference it.
This is done during a "normal " day, wind, rain, whatever, iin the afternoon.

This gives me a good indication of how the rifle is going to react when it gets warm during a five shot, 50 second string for rifle rodeo, or a five shot target match .
It also gives me an idea if i am going to bbe able to handle the rifle well enough.
I shoot some better than others....
cat
 
Thanks for the replies. I will be shooting matches with time limits, but I was just wondering what to expect. As soon as I get loads worked up I'm going to start doing those kinds of tests ("rapid" fire from bench, slow fire from bench, POI change after GunJuicing, etc.). I want to figure all of this stuff out before the TacMatch in Chilliwack.
Do you guys log your reloads as well ("batch" number, etc.)?

-Rohann
 
The ammo gets numbered by the box on labels - lot 1, 2 etc. and the number of thimes the brass is loaded gets logged, as well as the running round count for each rifle ,in the log book.
Cat
 
Oh ok cool, I'll do the same. Just out of curiosity, what kind of logbook do you use? An organized range-bag sized notebook, or a binder? So far I just log things onto a Word document after copying it down at the range.

-Rohann
 
I have used the log book such as Jamie uses, but prefer to use a ringed 8.5X11
ring binder so I can jot down lots of stuff that pertains to the rifle.

All my reloading data goes into the same book, as does my son's.
That way we are "on the same page"! :D
cat
 
I also keep a a spare notes pages in my log book too.....Everytime I shot I learn something new

Jamie
 
I just use a binder, standard 2" school size. That way I only have one book to tote to the range. Makes life easier, and I have all my data in one place. As for the heat vs. accuracy thing, if you shoot in a discipline that requires multiple shots, you are just fooling youself as to the practical accuracy of your rifle by only shooting from a cold barrel. - dan
 
Jamie: Thanks! That's a pretty big logbook; do you just write in whichever type of target you use? Can you give me a bit of an idea as to how you use it?

cat: That sounds like a good idea, I think I'll start doing the same. I haven't really recorded the shots I've taken in detail, but I've only put about 57 rounds through it.

dan: You're totally right. What I was trying to figure out too, though, is how much the POI changes from taking a cold-bore shot to shooting in succession (at the Chilliwack Tac-Rifle match there aren't any sighters).

-Rohann
 
Rohann, test as you are going to compete/hunt. Do your initial load development with as cool a barrel as possible. You don't want heat issues to cloud your results.

Once you have a decent load or two, shoot them at the distance and conditions the rifle will be applied.

For hunting, I test from a cold barrel as close to the temp I will be hunting in. No use testing a 30C "cold" barrel when I am hunting near freezing. I want to know where that first bullet lands at any range I am likely to hunt at.

I will also test two follow up shots and see if there is any significant change in POI. If there is, I either have to live with it or get another barrel/rifle.

For competition, work your load/rifle under match conditions. For F class, I worked up my loads using low rd counts so nothing overheats and I am sure of the results - no shooter fatigue.

Then I test each load with several 20 to 25rds groups at distance in 15min or less to simulate match conditions. Obviously, testing is done in the warmer months. Hopefully, the last few shot are as accurate as the first.

Track how that barrel behaves as it heats up an fouls. Many factory barrels will 'walk' as they heat and also loose consistency (dispersion increases). Sometimes, this is greater then acceptable and a new pipe/rifle is warranted.

Quality BR barrels tend to be more stable even when scalding hot. Only testing will determine this.

Also, test the ammo. Many powders are affected by ambient temp so if you use that ammo in the cold, test in the cold.

For F class, my chambers are going to get very warm. As a final test, I will chamber rds and let them heat soak for a few minutes. I need to know that if I hold off shooting and leave a rd in the hot pipe, it will not cook off/overpressure or fly into the 8 ring.

For hunting, I might get the ammo damp and see if that affects anything.

You need to trust that rifle will perform if you do. Wasting time second guessing yourself or the rifle ensures you will not have the confidence to score.

It doesn't matter if this means groups are bigger then a dime. I will take consistency and predictability over a fussy bug hole shooter anyday.

Now the really hard part, practising and improving enough so you are as good as your rifle.

Jerry
 
Seems that Jerry knows what he is talking about. Have you found barometric pressure to effect anything, or that coupled with ambiant air tempurature, or humidity levels? There are so many variables... its a wonder we even conect with the vermin at any extended range lol.
 
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