Temperature and Pressure

[Bigeclipse]

Hey all,
I have read some articles on how temperature can effect accuracy and pressure. I have read numerous threads on which powders may or may not be effected by this as well (or somewhat resistant) So here is my situation... I get really bored over winter (no hunting season where I am until May) so this is when I do a lot of my reloading, testing, and shooting. Temperatures are typically below 20 until mid to end February. My question is if you develop a hottish load during this time, what impact have you see on pressure increases in say a 30 degree temp swing in weather. The reason I ask is deer season here is in November. Typically the temps are similar to my testing temp of 20 degrees (normal temps are between 15-30) but we do have some crazy temp swings once in a great while. this past year we actually had one day approach 50. I think it was 47degrees out. So in a situation where you develop a hot load near max charge for your rifle in say 15 degrees...are you worried about potential injury to you or your rifle if the temp increases to 50 degrees? 70? 90? or do you find accuracy may suffer but even though the pressure does increase, it is not too much of a safety concern? I know this is all subjective and every person and rifle may differ, I am just asking for honest answers here. Please don't just say (test in temps you shoot) or something like that. I do try and test in same operating temp as my hunting season but sometimes weather can act really fun during hunting season and we cant control it. The reason I am asking is lets say you run a ladder or OCW test and find a really accurate and fast load. This load is giving you just a touch of pressure signs (slightly flattened primer)....maybe a "hint" of ejector mark but very hard to tell (definitely NOT a definitive shiny ejector mark nor heavy bolt lift) and you tested this in 15 degree weather. Would you be worried about shooting this load in say summer time? If so, does that mean you test a few rounds with lower powder charges first? Again, ignore accuracy for this discussion. Thanks guys.

 

[Mikecr]

I mitigate some of the concern by keeping the ammo in my pants pockets, during load development, and while hunting. I load single shot in every gun(only when ready to actually shoot).
This takes care of ammo components.

There will still be some shifting in the gun. The colder bore will be tighter and the impact of this would likely correlate with given bullets (they're different diameters). Cold bore accuracy/tune could be affected as the bore is colder to the burn. So I would expect MV to go down a bit with very cold, but no significant pressure differences.

 

[Bigeclipse]

I mitigate some of the concern by keeping the ammo in my pants pockets, during load development, and while hunting. I load single shot in every gun(only when ready to actually shoot).
This takes care of ammo components.

There will still be some shifting in the gun. The colder bore will be tighter and the impact of this would likely correlate with given bullets (they're different diameters). Cold bore accuracy/tune could be affected as the bore is colder to the burn. So I would expect MV to go down a bit with very cold, but no significant pressure differences.

Thanks for the info. My major concern though is if you develop a hot load on the boarder of higher pressure. For instance lets take 60,000 as the pressure limit which by SAAMI specs hits say 50grains whatever powder you use. I slowly work up your load and see that for your rifle and chamber you aren't hitting pressure signs until 52 grains. For example slightly flattened primer and the Slightest hint of an extractor mark. So slight you aren't even sure if it is the extractor mark or not. So you figure you are around maybe 58,000 or so. Lets say for instance you did all this testing at 15 degree Fahrenheit. Not its summer... and 80 degrees out. Cant you safely shoot this load? I know there are a few variables here but should anyone even attempt to shoot this load since it was boarder line higher pressure in cold so theoretically it will be even higher pressure in the hotter summer time. Or am I thinking this through incorrectly?

 

[FEENIX]

Thanks for the info. My major concern though is if you develop a hot load on the boarder of higher pressure. For instance lets take 60,000 as the pressure limit which by SAAMI specs hits say 50grains whatever powder you use. I slowly work up your load and see that for your rifle and chamber you aren't hitting pressure signs until 52 grains. For example slightly flattened primer and the Slightest hint of an extractor mark. So slight you aren't even sure if it is the extractor mark or not. So you figure you are around maybe 58,000 or so. Lets say for instance you did all this testing at 15 degree Fahrenheit. Not its summer... and 80 degrees out. Cant you safely shoot this load? I know there are a few variables here but should anyone even attempt to shoot this load since it was boarder line higher pressure in cold so theoretically it will be even higher pressure in the hotter summer time. Or am I thinking this through incorrectly?

The pressure sign is a safety issue/concern and is telling you something. Ignore it and face the consequences associated with it. I provided a video link on your pressure signs thread -- I thought it was very informative and straight to the point.

 

[dkhunt14]

If you are on the edge when it is cold you will be too hot when in summer. Matt

 

[barefooter56]

Bigeclipse,
Lots of good suggestions here. Usually load testing is done during Hot weather. Especially working up a target load where you are out in the sun for long periods. If you work up a load in the heat of the summer you will know what your maximum load is for most circumstances. However, you will also need to test it in the cold for hunting applications. Some things you may test in the cold is using a magnum primer instead of a standard primer or just changing to another brand of primer that has been tested and found to be hotter than what you are using now. Always back the load down a grain or so and work back up. You may have to work up a load using one of the "extreme" temperature powders if you are not using one already. In short you are trying to make the load as flexible as you can so you don't have issues in cold or hot such as hang fires or over pressure. There is no one answer . You have to test to know. Just as you have to test your bullet seating depth and powder charge to find your seating depth and velocity accuracy nodes. In your case its the velocity change due to the cold that can throw your accuracy off possibly. Bryan Litz's book "ACCURACY AND PRECISION FOR LONG RANGE SHOOTING " has a chapter on muzzle velocity effects that goes more in depth on this. Hope this helps!
Take care!
Phil Hoham
Berger Bullet Tech

 

[Bigeclipse]

The pressure sign is a safety issue/concern and is telling you something. Ignore it and face the consequences associated with it. I provided a video link on your pressure signs thread -- I thought it was very informative and straight to the point.

yes it was informative about what pressure signs look like. Thank you... but it was not very informative on the question this thread is about. I am not trying to sound rude and do appreciate any information given. I was simply just asking what types of impact developing hot loads in the winter cold have running those same loads in the summer. I know pressure increases with heat but was not sure how much. From what people are saying here is a hot load in the winter can become a dangerous load in the summer. that is all I needed to know.

If you are on the edge when it is cold you will be too hot when in summer. Matt

thanks...that was basically what I was after.

Bigeclipse,
Lots of good suggestions here. Usually load testing is done during Hot weather. Especially working up a target load where you are out in the sun for long periods. If you work up a load in the heat of the summer you will know what your maximum load is for most circumstances. However, you will also need to test it in the cold for hunting applications. Some things you may test in the cold is using a magnum primer instead of a standard primer or just changing to another brand of primer that has been tested and found to be hotter than what you are using now. Always back the load down a grain or so and work back up. You may have to work up a load using one of the "extreme" temperature powders if you are not using one already. In short you are trying to make the load as flexible as you can so you don't have issues in cold or hot such as hang fires or over pressure. There is no one answer . You have to test to know. Just as you have to test your bullet seating depth and powder charge to find your seating depth and velocity accuracy nodes. In your case its the velocity change due to the cold that can throw your accuracy off possibly. Bryan Litz's book "ACCURACY AND PRECISION FOR LONG RANGE SHOOTING " has a chapter on muzzle velocity effects that goes more in depth on this. Hope this helps!
Take care!
Phil Hoham
Berger Bullet Tech

good to know! Maybe I will hold off on all my load work ups until summer...now I need to find something else to do during the winter haha.

 

[barefooter56]

Bigeclipse,
I have found that case prep is a good distraction during the winter.....LOL !!
Phil

 

[Bigeclipse]

Bigeclipse,
I have found that case prep is a good distraction during the winter.....LOL !!
Phil

That's a good idea!

 

[barefooter56]

Make sure you have a good stereo and XM radio capability in your room. Bluesville , Little Steve's garage, Jazz , Sinatra. Depends on my mood lol!. Makes the chore easier and isn't distracting IMHO. Finish one process for all ( decap, fl size, trim etc) before you go to the next step and keep a list of where you are in the process in each can of brass. Doing .223 brass for 3-gun taught me that. Volumes are huge ! You try to do one cartridge case completely at a time and the pile NEVER seems to get smaller and that's depressing. I try to end up where I have all the brass done (even primed) so all I have to do to get out to the range or a match is drop powder and seat bullets.
"eat the elephant one bite at a time"
Take care!
Phil Hoham
Berger Bullet Tech

 

[Bigeclipse]

Make sure you have a good stereo and XM radio capability in your room. Bluesville , Little Steve's garage, Jazz , Sinatra. Depends on my mood lol!. Makes the chore easier and isn't distracting IMHO. Finish one process for all ( decap, fl size, trim etc) before you go to the next step and keep a list of where you are in the process in each can of brass. Doing .223 brass for 3-gun taught me that. Volumes are huge ! You try to do one cartridge case completely at a time and the pile NEVER seems to get smaller and that's depressing. I try to end up where I have all the brass done (even primed) so all I have to do to get out to the range or a match is drop powder and seat bullets.
"eat the elephant one bite at a time"
Take care!
Phil Hoham
Berger Bullet Tech

thanks! I have two rifles and 7 pistols I reload for so definitely no shortage of things to reload

 

[Bill Johnson]

Back when I was young and dumb (got over one of those) I developed an excellent coyote load in my 30-30 using a Speer 110 spire point. Temp was around 45F. Come summer with temps in the 90s, flattenned primers and sticky extraction. I'd have to look in my notes but it was some crazy load I had worked up and knew it was on the edge as far as pressure. Just forgot until later in the year.....

 

[Bigeclipse]

Back when I was young and dumb (got over one of those) I developed an excellent coyote load in my 30-30 using a Speer 110 spire point. Temp was around 45F. Come summer with temps in the 90s, flattenned primers and sticky extraction. I'd have to look in my notes but it was some crazy load I had worked up and knew it was on the edge as far as pressure. Just forgot until later in the year.....

what you just stated is a perfect example of what I was after.

Problem is I already loaded up the rounds to run a ladder. I chose to load 6 loads. the top load is .5 grains less than what I currently tested as my max load in this thread (the case picture in the beginning of this thread was 50.2 grains...the top load I loaded for my ladder is 49.7 grains) so I guess technically I could run my ladder during temps that will be colder say for example 25F. If my results show stability node below the highest load then I will probably be good to go in upper temps (as far as safety) but if my accuracy node is one of the higher loads then I would have to keep that in mind for warmer temps. What I could do in that scenario is when warmer temps start to hit, such as 60s...I could do another smaller max load test there. if I show my max load in the warmer weather is above my accuracy node load from my ladder test in cold weather, then this load will be a good load for hunting temps here in NY (gun season is always below 50f, usually well below that). or is this a bad way to look at it? Again safety is definitely most important thing of course!