lil gun cold weather pressure

[45r]

I read something on another site that lil gun has around 4 or 5 thou higher pressure in cold weather due to it's higher nitro content or something like that.Is that why the pressure is often lower for top loads on data sheets compared to H-110/296.

[Hoot]

I live where the temperature swings over a 120 degrees and I use almost entirely Lil Gun in my 450b. I've never seen Lil Gun get faster as the temp goes down, nor have I seen increased pressure indications so I can't confirm that one.

Hoot

[wildcatter]

I live where the temperature swings over a 120 degrees and I use almost entirely Lil Gun in my 450b. I've never seen Lil Gun get faster as the temp goes down, nor have I seen increased pressure indications so I can't confirm that one.

Hoot

10-4 on this..

45r, you could test it for yourself and report the results here, by putting some rounds in a zip-lock bag, in the freezer. Transporting them in a cooler, on ice and Very Soon, their after, shoot them (don't let them sit in your gun for more than several seconds, before shooting) and you'd get a good idea about the performance.

In years past, I did this with dry ice in a cooler and didn't have any hang fires, until I got into the mid-burn-rated RIFLE powders (I forget just now, but I seem to remember, the problems didn't start, until I got slower than IMR4895). I'm sure these Renegades, around these here parts, have far better ideas about testing cold weather loads. without being in cold weather..

..t

[pitted bore]

I read something on another site that lil gun has around 4 or 5 thou higher pressure in cold weather due to it's higher nitro content or something like that.Is that why the pressure is often lower for top loads on data sheets compared to H-110/296.

45r-
There are two parts to your interesting question.

[1]
I recall reading the same rumor somewhere. I think it's not true. Like Hoot, I've not observed any increase in Lil'Gun pressures at low temperatures. (We don't get quite the temperature extremes here in MI's U.P. that he gets in MN.)

I'd really like to know where the data for a 4-5K psi increase originated. For this level of detail, somebody must have had a pressure measuring device. Because the claim runs counter to the usual understanding of how powders work, I'll be sceptical until somebody produces the set of data showing this, with a description of how it was collected.

Hodgdon claims that their line of Extreme powders show decreased temp sensitivity, but Lil'Gun is not one of these powders.

I'd bet that "nitro content" is not the reason for the claimed behavior. Nitroglycerin has been a component of smokeless powders for about 124 years. The original British cordite was more than 50 percent nitroglycerin, and it was notoriously temperature sensitive, with the highest pressures occurring at high temps. The double-based nitro-containing powders distributed by Alliant all show the usual decrease in pressure when fired at lower temps.

According to some gun writers that seem to know what they're talking about, the ball powders from Ramshot/Western (like the Enforcer powder that does pretty well with light bullets in the 450B) are a lot less temperature sensitive than the majority of other powders. They attribute this to some remarkable additives developed within the last 20 years in Europe. However, the powders do not show an increase in pressure at low temps, but rather a comparative lesser decline in pressure at low temps.

Hodgdon doesn't reply to emails very promptly, but it still might be worthwhile to send them this question and seek their opinion.

[2]
Could you further explain your question about data sheets showing pressures at top loads for Lil'Gun vs H110/296?

Has Hornady published pressures for 450B reloading data? To which data sheets are you referring? I'd really like to know for some of my own efforts with this cartridge.

Thanks.

--Bob

[45r]

I asked because data for 357mag and 300BLK are showing lower pressure for the same weight of lil gun compared to 296/h-110.In a question about using lil gun in the 300 BLK at another site the pressure issue in cold weather was brought up.It was recommended to stick with 296/h-110.I'm glad their isn't any concern with the 450.

[Hoot]

The one remote possibility that comes to mind is the fact that Brass, due to its copper content, exhibits a large change in volume as a function of temperature, as most metals go. A case loaded in a room at 75 degrees would have less internal volume once it got very cold. Less case capacity equals greater chamber pressure for the same amount of powder. That phenomenon would apply to all powders though. Not just Lil Gun. I'm speaking obviously in generalities and since I've never actually measured case capacity say just above the freezing point of water and say just below the boiling point, it's probably an inconsequential amount. However, maybe it's not.

Hoot

[Stealthshooter]

That might prove to be a hard thing to measure unless you had some salt water at the same temp as the case is. Any warmer and the case would rapidly warm to the temp of the water.

[Stealthshooter]

Just thought of something. Maybe you could use some Glycol instead of water?

[pitted bore]

The one remote possibility that comes to mind is the fact that Brass, due to its copper content, exhibits a large change in volume as a function of temperature, as most metals go. A case loaded in a room at 75 degrees would have less internal volume once it got very cold. Less case capacity equals greater chamber pressure for the same amount of powder. That phenomenon would apply to all powders though. Not just Lil Gun. I'm speaking obviously in generalities and since I've never actually measured case capacity say just above the freezing point of water and say just below the boiling point, it's probably an inconsequential amount. However, maybe it's not.

Hoot-
I think you're correct in assuming that the change in volume with temperature is inconsequential. Here's a LINK to a page with coefficients of thermal expansion of some metals. The coefficient has units of microinches per inch per ºF. For cartridge brass the coefficient is 11.1, or 0.0000111 inches per inch per ºF.

So, if a 450B case is 1.6900 inches long at freezing (32ºF) and its temperature increases 180ºF to the boiling point of water (212ºF), the case would increase in length from 1.6900" to about 1.6934". Calculating volumetric increase is an exercise left to the student <grin>. The 180ºF range is large, but I've hunted at minus 20º and at 100ºF, a range of 120ºF.

(According to the table, if the case were made of plutonium, the expansion would be about twice as much.)

--Bob
(edited for spelling, grammar, and clarity.)

[Jim in Houston]

Another possibility to consider is the speed of the chemical reaction as the powder ignites and begins to burn, which would be slower at a lower temperature. Don't know exactly what effect this would have - allow more time for combustion gases to build up pressure before the bullet is expelled, which would be like preloading the cartridge with some initial pressure before the bulk of the powder ignites.

Any chemistry majors out there?