temperatures effect on everything.

[22BRGUY]

Cold air is more dense to shoot through also.

 

[savagedasher]

Could have been the cold didn't let the firing pin hit hard enough. I had this happen in a banquet shoot when it was bitter cold. I had to hit the first three, two or three times to get them to go off. After a few fired and I got some heat in the gun they all fired. Matt

It wasn't when I took one out of a inside pocket I shot the deer put a cold one to finish it off all 3 wouldn't fire. The warm inside my pocket did. Pulled the bullets and powder replaced the primers with mag no more problems . Guess their a reason for putting mag primers for cases with over 60 GR of powder and cold weather. Larry

 

[dkhunt14]

Yes that is the rule I use. Especially with slow powders and for hunting. Matt

 

[chevytruck_83]

I often wonder about random stuff like this. Ill ask these forums then end up buying books by people like Brian Lititz and try to wrap my head around things I don't fully understand. After about a half a dozen times reading it finally makes sense. Just seems to me like there's a lot of variables that change with temperature to only account for burn rare and obviously environmental data into your trajectory cards.

 

[Tozguy]

I see posts about how temperature sensitive a powder is but often wander how much effect the barrel being subjected to the same Temps effects velocity. I realize the expansion of steel is very minimal but I would think there is some change. A tighter bore at least In my head would cause both higher pressures and more resistance. Are there any articles worth reading that take other factors into account when considering temperature.?

There was an article recently that related increases in velocity to bore fouling. Sorry don't remember the source. It makes sense to me that the accumulation of bore fouling is tightening the bore enough to impact velocity. It would seem relatively easy to observe this ourselves.

The thermal expansion of a bore could be calculated. But if testing shows that velocity increases with respect to fouling, then the thermal expansion occurring in that situation was not enough to compensate for the build up of fouling and keep velocity constant.

And does barrel temperature have an impact on the rate at which the bore will foul?

 

[chevytruck_83]

There was an article recently that related increases in velocity to bore fouling. Sorry don't remember the source. It makes sense to me that the accumulation of bore fouling is tightening the bore enough to impact velocity. It would seem relatively easy to observe this ourselves.

The thermal expansion of a bore could be calculated. But if testing shows that velocity increases with respect to fouling, then the thermal expansion occurring in that situation was not enough to compensate for the build up of fouling and keep velocity constant.

And does barrel temperature have an impact on the rate at which the bore will foul?

Good points. If you do remember at some point where you read this please let me know. Sounds like an interesting read.

 

[dkhunt14]

There was an article recently that related increases in velocity to bore fouling. Sorry don't remember the source. It makes sense to me that the accumulation of bore fouling is tightening the bore enough to impact velocity. It would seem relatively easy to observe this ourselves.

The thermal expansion of a bore could be calculated. But if testing shows that velocity increases with respect to fouling, then the thermal expansion occurring in that situation was not enough to compensate for the build up of fouling and keep velocity constant.

And does barrel temperature have an impact on the rate at which the bore will foul?

Yes I believe it may tighten the bore some but I wonder if it also doesn't lubricate it as well. Carbon and graphite are lubricants.

If you shoot at 1000 yards the point of impact is low with a clean barrel. Some barrels is a lot. Usually after one to two shots it levels off and stays consistent. If it would get tighter as fouling builds I wouldn't think you could shoot a small group. Another thing is if you put 2 drops of Marvel Mystery oil on a patch and push it through the clean barrel the first shot is close to Point of aim. Now I know 2 drops would slightly tighten the bore but most stays on the patch. How much could it tighten a bore on a .308 barrel at 30 inches.

Yes I think temperature can effect the way a bore will foul. I find the colder it is the more it fouls. If you don't believe this try loading and shooting a muzzleloader in very cold conditions. This is just my opinion from things I observed. Matt

 

[chkunz]

Using the coefficient of thermal expansion for steel, I calculated that the expansion of the bore for a thirty caliber rifle for a 200 deg temperature rise would be 0.0004 inches.

 

[billlarson]

The coefficient of linear expansion for steel is 0.0000065 in/in/deg F so you can ignore the effect of temperature on barrel dimensions.

WHY THEN DO THEY RECOMMEND "NOT"USING STAINLESS BARRELS IN SUB ZERO TEMPS....????

 

[LHSmith]

WHY THEN DO THEY RECOMMEND "NOT"USING STAINLESS BARRELS IN SUB ZERO TEMPS....????

That is only for a specific SS alloy.

 

[chkunz]

The coefficient of linear expansion for stainless steel, 18-8 is 0.0000096 in/in/deg F

 

[Tozguy]

Using the coefficient of thermal expansion for steel, I calculated that the expansion of the bore for a thirty caliber rifle for a 200 deg temperature rise would be 0.0004 inches.

That is huge! and explains why my 30-06 hunting rifle has trouble keeping the third shot in the group.
I always ignore the first clean/cold bore shot in any accuracy test. After the bore is fouled by a shot or two aren't subsequent bullets all facing a similar bore surface? But if temperature is rising and the bore is changing dimension then wouldn't the energy lost to friction vary according to clearances?

The question of lubricants in a bore gives me a headache. The darn stuff makes a good pressure sealer when it can't flow out of the way fast enough.

 

[Changeling]

Years ago I went squirrel hunting with a Ruger 10/22 that I had greased/oiled (Rem oil/grease) up nicely (lack of experience) Temp was down around 0 deg. After sitting a while I got a shot at one. It didn't go off even after a few attempts.
Later at home I cleaned out all the grease and oil with lighter fluid. Put 1 drop on the bolt, that's all. Never had another problem.

 

[M14AMU]

Anyone that doesn't believe that temperture changes affect powder, ignition, and MV.....shouldn't be in the rifle game!!

 

[rain164845]

WHY THEN DO THEY RECOMMEND "NOT"USING STAINLESS BARRELS IN SUB ZERO TEMPS....????

I think that has to do with brittleness of the stainless at low temperatures that has caused sporter weight barrels to blow up at very cold temps.

 

[billlarson]

Anyone that doesn't believe that temperture changes affect powder, ignition, and MV.....shouldn't be in the rifle game!!

Sure does..... and another thing that has always amazed me is military ammo..... it goes off at +120*F and --60*F...... shows they did our homework.....

 

['Freak]

Using the coefficient of thermal expansion for steel, I calculated that the expansion of the bore for a thirty caliber rifle for a 200 deg temperature rise would be 0.0004 inches.

Lookin’ like you ciphered that one on a CM barrel’s bore ID and not the barrel’s OD in the vicinity of the neck. As the barrel’s temperature is increased it’ll expand outwards, or contract if cooled, at the same rate for all dimensions.
.308” x .0000065” x 200° = .0004”, if …?
vs.
(1.125” - .308”) x .0000065” x 200° = .00106” change in bore ID according to the amount of steel making up the barrel’s wall thickness from the ID on out to the major OD.

Comparing CM steel at ambient 5° vs. 95° fer only a 90° increase, a barrel’s bore ID is increased .00048”.
(1.125” - .308”) x .0000065” x 90° = .00048”


Thinkin' that's how it works anyways.
'Freak

 

[chkunz]

Lookin’ like you ciphered that one on a CM barrel’s bore ID and not the barrel’s OD in the vicinity of the neck. As the barrel’s temperature is increased it’ll expand outwards, or contract if cooled, at the same rate for all dimensions.
.308” x .0000065” x 200° = .0004”, if …?
vs.
(1.125” - .308”) x .0000065” x 200° = .00106” change in bore ID according to the amount of steel making up the barrel’s wall thickness from the ID on out to the major OD.

Comparing CM steel at ambient 5° vs. 95° fer only a 90° increase, a barrel’s bore ID is increased .00048”.
(1.125” - .308”) x .0000065” x 90° = .00048”


Thinkin' that's how it works anyways.
'Freak

Intuitively that is what most folks would think. But that is not how the physics works, you use the bore diameter. One way to think of this is to imagine a large steel plate, draw a circle on the plate and then heat (or cool) the plate and observe what happens to the circle. The amount that the circle changes with temperature is not dependent on the size of the plate. Another way to understand the physics to imagine drilling a hole in a large block of steel and imagine what happens to the hole with a temperature change, it does not depend on the size of the block that the hole is drilled into.

 

['Freak]

Intuitively that is what most folks would think. But that is not how the physics works, you use the bore diameter. One way to think of this is to imagine a large steel plate, draw a circle on the plate and then heat (or cool) the plate and observe what happens to the circle. The amount that the circle changes with temperature is not dependent on the size of the plate. Another way to understand the physics to imagine drilling a hole in a large block of steel and imagine what happens to the hole with a temperature change, it does not depend on the size of the block that the hole is drilled into.

Ooooh … tay, took awhile but now I get it, I think… Same rate but the diameter change at pick a point on a cylindrical object is greater by 2x the radius the further the check point is from the center point, rite?

 

[chkunz]

Ooooh … tay, took awhile but now I get it, I think… Same rate but the diameter change at pick a point on a cylindrical object is greater by 2x the radius the further the check point is from the center point, rite?

Sometimes it helps me to evaluate an extreme case to understand the physics. Think of an infinitely large plate with a hole in it. Now change the temperature of the plate and calculate the change in the diameter of the hole. Obviously you would not use the infinite dimension of the plate for the calculation of the change in the diameter of the hole, you would use the diameter of the hole in the calculation. With all respect, your example may be correct, I just could not visualize it. Calculation of the change in barrel dimensions with temperature is the easy part, the challenge is to determine the effect on accuracy, if any. Take care, Clyde.