Temp Sensitivity

[Rifleman]

Ok I am gonna open a can of worms here but please understand I am only interested in the actual, factual, results of the scientific data. I am not trying to honk anyone off or step on any toes.
Steve White has commented many times about many powders being temp. sensitive in the Savage. Ok I will buy a certain amount of that as I know in centerfire applications some powders do display temp sensitivity while other seem to be fairly immune. However Steve maintains that N120 is temp sensitive. Well first let me say I have the utmost respect for Steve and his intellect and I know he tests many more loads then I even care to. However I am not sure this subject has really been looked into enough to provide a conclusive answer. I can honestly say that I have not Chronographed N120 for the sole purpose of testing temp sensitivity. However I have shot this load (60 grs N120, Barnes 300 gr original, MMP orange sabot, and WW209 primer) almost to the exclusion of all others for quite some time, and I have shot it in a wide range of temps. If this load was temp. sensitive to the degree I believe Steve maintains it is, then I should have at the very least picked up a change in POI. I have not seen a change. Matter of fact a couple weeks ago I shot a deer in the top of the heart at 135 yds (temp was about 35) and this was somewhat of a difficult shot. I had to get off my little stool and contort my position and thread the needle through the brush to hit the deer where I wanted to. I aimed low on the heart and with my given zero, my POI was dead on for the given range. No doubt this is not a conclusive test, however it jives with what else I have seen with this load and serves as an example.
So my question is this. Has this question of temp. sensitivity with N120 ( or any other powder for that matter) been tested in a complete and scientific manner? Has this matter of temp. sensitivity been tested solely or has been just an observation made in conjuction with other tests being conducted? Is there recorded data that would stand up to scrutiny to support such conclusions?
I do believe at lower charge weights or lighter bullets this powder will not make consistent pressure. However at 60 grs with a 300 gr bullet I do believe both are heavy enough to avoid temp. sensitive issues. But again I myself have no hard data to support or disagree with my own conclusions.
Again I am not trying to pick a fight with Steve, he is my favorite powder stuffin dentist! Just looking for the facts.
Thanks Rman

 

[SW]

Dwight,
I have fairly thoroughly tested 2015/300SST/SMI,VV-110/250XTP-SST, VV-110/120 10/60/250SST,14/61 110/322 250SST from >90 degrees to slightly sub-zero(rare to find such temps in AR but did 2-3 years ago). I have not tested VV-120 nearly as much - also my gun with relatively smooth(lapped barrel) for some reason shoots best at 57g/300SST/HPH-12. This combination 57gs,300SST,somewhat loose barrel)does certainly loose velocity as temps get into the 20s - appx 200'/sec over 70degree temps. This is a comparatively low pressure load though, especially compared to 60gs in a tighter barrel. I think those of you who live where it can really get cold do some chrono testing. Hopefully, VV-120 will not be nearly as temp sensitive as it is in my rifle with its load.

 

[RBinAR]

I almost always avoid this topic as I don'treally care to shake a hornet's nest.

Where I live it's hard to get much shooting in really cold weather. So I have a suggestion: y'all all move south of 33 degrees latitude and you won't have to debate this.

 

[Rifleman]

Rick and Steve,
I would love to move south of the Mason Dixon line but if I did I would have to shed alot of weight to keep from sweatin to death on those hot summer days. That doesn't really sound like an option for someone who loves baked goods as much as I do.

No, I don't really consider this a debate or hornets nest, just simply a question that needs answered. I wanted to establish whether if the testing had been done or not. Sounds likes Steves load of 57grs and a looser barrel might be quite a bit lower pressure then my combo of 60grs in a tighter barrel. I have enough true data for my load at higher temps ( from 50 to 70 degrees) that it would be a fairly simple matter to fire a few shots over my chrony at lower temps and compare. Hopefully this winter I will get around to doing this and be able to share my findings.

Could be Steve that what I think we both expect is true, and that is there is a certain amount of pressure level that must be reached to avoid a temp sensitive load and once that is reached it is not a significant issue.

I know from my experience as a operator in a power house that as a general rule of thumb, cold fuel generates less heat/pressure then pre warmed fuel. I would say that with even those powders that were designed to be temp insensitive there is a measurable drop in velocity as temp drops. Now it might not be significant, but it will be measurable. So the question becomes not if, but how much.

 

[RBinAR]

Rick and Steve,

I know from my experience as a operator in a power house that as a general rule of thumb, cold fuel generates less heat/pressure then pre warmed fuel. I would say that with even those powders that were designed to be temp insensitive there is a measurable drop in velocity as temp drops. Now it might not be significant, but it will be measurable. So the question becomes not if, but how much.

Dwight there is no doubt in my mind the cold effects load performance. The extent is hard to measure or perhaps just beyond my ability to measure.

Amoung other things some odd conditions exist in a muzzle loader that one would think causes the effect. One is "engraving pressure" this refers to the initial pressure generated by a rifle loaded from the breech to start the bullet in the lands and grooves. Since the bullet is not a perfect fit it takes some pressure to get the bullet into the barrel. The inital pressure generally runs 2000 to 3000psi and it provides a pre-heated condition for the fuel to burn as the bullet heads down the barrel. There is no engraving pressure in a muzzle loader.

Another problem making things worse is in really cold weather plastic can be come brittle and effect load performance. Duck hunters have carried ammunition in their vest pocket for years knowing patterns can be terrible with really cold shot shells.

Still without a way to measure the problem here's what I've told folks that hunt in really cold weather: try to develope your load within 20 degrees of the temperature you'll hunt at. It's been my experience that almost any powder is immune from temperature effect if the difference is less than 25 degrees.

So if you hunt where it will be 60 degrees try to develope a load at 60 so the load will shoot from 35 to 85 degrees no problem. Only if you get a horrific day (90 degrees or 30 degrees) will the load be affected and then probably not by much. If you hunt when it's really cold say 10 degrees try to shoot some when it's 20 or 15 don't go into the woods with a load developed when it was 65.

As a worse case condition what some hunters may be faced with is having two loads. Maybe a really cold weather load and a really warm weather load.

 

[Rifleman]

All good points RB.

 

[SW]

Concerning working up loads near the temps we will hunt in: do more people work up the next seasons load in July-Oct or Jan-Mar? Which is the better time for Nov,Dec hunts?

 

[RBinAR]

Concerning working up loads near the temps we will hunt in: do more people work up the next seasons load in July-Oct or Jan-Mar? Which is the better time for Nov,Dec hunts?

The woods are full of hunters in Nov. and Dec. and the ranges are full of dust in Feb. and March.