BP temperature sensitive?

[StewartLeach]

Was out yesterday with my tried and true 40 cal flinter, getting ready for a trip to NMLRA matches at Phoenix. High temp for the day was 39 degrees Fahrenheit. Same cast balls, GOEX 3Fg, patching, moose milk lube as always. Same sight picture, too.

Groups were good, but 2.5 inches low at 50 yards. Could this be due to temp being lower than most of the time when I shoot this rifle?

 

[mark/wi]

I have not noticed any change in mine because of temp. Mark

 

[Col. Batguano]

A couple of things are going on;

Yes, pressures in a colder bore are going to be lower than in a hotter one.

When stuff gets colder, it shrinks. The bore is going to have a slightly larger diameter, and the ball is going to be of a slightly lesser one too. Thus, you're more likely to get blow-by with the expanding gasses, but more importantly, (and this assumes that you use the same patch thickness and ball diameter as you did in more moderate temperatures) the ball won't take as much force to get started on its' way, so your peak chamber pressure will be lower, as will your velocities.

In Ye Olden days of extended African Safaris the British ammunition companies used to have a somewhat reduced load for ammunition intended for Africa. Particularly for their large bore double guns, and with their relatively weak primary extraction. Pressures in a blued gun could skyrocket in a gun who's chamber was out in the sun for awhile. Though I never heard of an action failing because of it, I HAVE experienced difficulty in actually breaking (for the purposes of extracting the empties) a finely made double (cartridge) gun when doing an extended range session. It only took about 8 rounds through it before I started noticing. Another good reason to only use muzzle loaders!

 

[smo]

High temp for the day was 39 degrees Fahrenheit.

Bet you had on heavier clothes than normal...

. Could this be due to temp being lower than most of the time when I shoot this rifle?

If you have heavier clothes on it could change the positioning of the rifle when shouldered . :idunno:

 

[Brokennock]

Velocity is probably lower, thus, possibly, a lower point of impact. Not sure if it correlates directly, but, I know modern pistol reloads loose a little to quite a bit of velocity, depending on powder used, in temps as little as 20 to 30 degrees colder.

 

[Danny Ross]

I'm going with SMO's answer also. The change in the
amount of clothing you wear would/could affect how you place your head on the stock, length of pull, and depending on the butt stock configuration, would/could change how it is placed into the shoulder at the bench also. If anything that would be affected being put down the barrel at colder temps, I would think it would be more the patch lube. 39 degrees is not that cold though, now if we were talking -10 that "might" be another story. Again though, I would think it would be more the clothing. Now if we were talking Pyrodex I have seen changes in impact with colder temps using that, real Black Powder no. DANNY

 

[smoothshooter]

I think you may be mistaken on the rifle bore enlarging when cold.

It will shrink like everything else.

 

[jpm1963]

Correct, in fact the bore will shrink more than the ball, but neither is likely to change enough to significantly effect the outcome.

Humans operate in a very narrow temperature range, when we do press fits in the shop using liquid nitrogen, that is when you see the temperature matter. Until it is about -200 C or so, I doubt it matters much to the bore or ball. Now the shooter might be a little less likely to hold the target while shivering.

Jim

 

[Pukka Bundook]

What sort of a day was it, Whitefox??

If a very bright sunny day, even if cool you will likely shoot lower than on a dull day.

Old saying was, "Light's up, sights up"....Light's down, sights down!".

I've shot mine and not noticed much difference between say 70 F and -20F More human error on my part I'd guess if I shot off.(At moderate ranges) Yes, there is a bit of difference, but never noticed this much.

Best,
Richard.

 

[M. De Land]

True, anything circular expands in ID diameter when heated and shrinks when cooled.
Same deal as heating a steel sleeve to put on a shaft, when it cools it's locked in place by shrinkage.

 

[Rifleman1776]

All good info.
But, as for the bp, no. Real bp is a chemical mixture. It is not affected by temp. changes. It does not compound until ignition. But, as others have stated, other factors may affect the performance of a ml rifle in extreme temps.

 

[hanshi]

Black powder does not seem to be temperature sensitive at all, from what I've read and experienced. Many smokeless powders can be, however. And while I've never been shooting/hunting is really cold weather, I have been out many, many times when it was well below freezing...yeah, I know, that isn't even approaching the cold some of you experience.

 

[MSW]

brrr ... just reading about this stuff has motivated me to get the woodstove going

 

[Hairy Clipper]

In Walter M. Clines book about Muzzleloaders: Then and Now, first published in 1942, Walter tells of how the target shooters of the day would notice a 1" lower point of impact in cold temperatures at their usual shooting distance of 60 yards (IIRC). He is referring to flintlocks in his book.

 

[68K20]

I wonder if this would have anything to do with the way the barrel is fastened to the stock? I know on the gun I picked up, it is held by pins through tight fitting holes, not slots. I would think when the wood stock contracts from the cold it could pull on bottom o the barrel, shifting POI down. This is on my list to fix before my next outing.

 

[Rifleman1776]

Your quote does say

target shooters

, meaning multiple observations of this effect. I'm not doubting his observation. But, I do believe the cause is something other than cold bp. Cold barrels might have different harmonic vibrations, etc. I dunno :idunno: just speculating.