So I do not shoot competition so this question is just for my info. I am fairly new to reloading and I do most of my shooting above 50 degrees. I guess 75 percent of my shooting is done above 70 degrees. My question is how much of a effect does the cold weather have on your load that you work up. Lets say I have a gun that shoots 1/2" groups or better in the 75 and up temps. Does it change when you shoot the same load in 40 degrees? I am guessing powder type has a bunch to do with it?
Cold question
- Thread starter BULLET 05
- Start date
I'm a novice but if you search temperature stable powder you will find several threads including some charts showing most powders. In general the extruded powders are more temp stable than ball powders but I'm sure there are exceptions.
Extruded powders will be less sensitive to temp changes but in extreme changes you will see some differences in M V.
It absolutely affects tune. How much is hard to say because there are a ton of factors. Suffice it to say that because it affects tune, it'll be the same as if you changed tune by adding or subtracted to/from the powder charge.
My 2 cents. I do a fair amount of shooting between 10F and 25F. Cold weather will decrease your velocity slightly but often does not change tune. I have several rifles that shoot better in the cold. The important factor is proper ignition. Temp stable powders are just part of the issue. You need to be using powders that ignite well at lower temps. Stay away from ball powders like WW748 or blc2. Use powders like the 4895 series that are easy to ignite. Also use a hot enough primer. Really cold temps can call for mil spec primers because they are a bit hotter. Do not use srp brass if a lrp option is available (ie srp creedmore vs lrp). Ignition issues will cause erratic velocity and groups. Larger cases with very slow powders can sometimes be an issue. For my 300wm I stick w 4350 or 4831 and a mag primer for the cold. Absolute temp stability is not required as much since you can measure your velocity fairly easily and know what the effect is.
I highly recommend shooting during the winter. You will have the range to yourself.
I highly recommend shooting during the winter. You will have the range to yourself.
There's a good reason that hunters often retest their loads when they get to their hunting locations, especially if the conditions are vastly different than they were where/when the load was developed.
My experience with hunting all year around, varmints in summer, deer / predators in the winter plus practice sessions at the range all year around is there can be a change in POI from rifles sighted in during the summer then using that same sight in during winter months.
I am not a ballistics engineer but in my experience ball powders are more sensitive to large changes in temperature. I have personally experienced pressure surges with H 380 in the 22 250 hunting varmints in 90+ degree weather. While I have shot some very nice groups with ball powder, several years ago I stopped using them since extruded powders give me more consistent results with the yearly large temperature swings that we experience in my area.
One of the most influential factors is air density. Cold weather air is more dense than warm air and has an impact on POI changes regardless of the powder used in my experience. This is especially significant when the shooting involves small vital areas like varmint and predators. For big game out to 300 yards, I do think it makes a difference since the vital area is so much large.
I would highly recommend verifying sight as the seasons changes for the aforementioned reasons stated.
I am not a ballistics engineer but in my experience ball powders are more sensitive to large changes in temperature. I have personally experienced pressure surges with H 380 in the 22 250 hunting varmints in 90+ degree weather. While I have shot some very nice groups with ball powder, several years ago I stopped using them since extruded powders give me more consistent results with the yearly large temperature swings that we experience in my area.
One of the most influential factors is air density. Cold weather air is more dense than warm air and has an impact on POI changes regardless of the powder used in my experience. This is especially significant when the shooting involves small vital areas like varmint and predators. For big game out to 300 yards, I do think it makes a difference since the vital area is so much large.
I would highly recommend verifying sight as the seasons changes for the aforementioned reasons stated.
Dimner
I do believe in Captain Crunch.
My personal rule of thumb is to match your load dev as close in temp as when you plan to shoot. I dont reload for matches, so I'm never worried about having that 1/4 moa group stay 1/4 moa at various temperatures. However, I will make sure to account for loads I plan to shoot in very hot weather. Those hlcan show unfriendly pressure signs if you do not load dev in warm weather.
For a hunting load I do my load dev during the warmer months. I find my stable node, retest it, then do my seating test and verify the results. At that point I wait until lat October to do the fine tuning of the load. Hunting loads are used, for my purposes, between 15 and 45 degrees most of the time. So I don't fine tune at 70 degrees.
For precision aka paper punching/long range steel loads, I never test lower than 50 degrees because I know that if it's less than 50 it's either a) hunting season b) cool enough for me to work on hunting loads or c) -10 degrees and I'm not gonna do anything outside in that cold other than sit by a campfire
I fine tune the long range steel loads at around 75 degrees.more often than not. That way when its blistering hot, i wont run into unexpexted pressure signs.
For a hunting load I do my load dev during the warmer months. I find my stable node, retest it, then do my seating test and verify the results. At that point I wait until lat October to do the fine tuning of the load. Hunting loads are used, for my purposes, between 15 and 45 degrees most of the time. So I don't fine tune at 70 degrees.
For precision aka paper punching/long range steel loads, I never test lower than 50 degrees because I know that if it's less than 50 it's either a) hunting season b) cool enough for me to work on hunting loads or c) -10 degrees and I'm not gonna do anything outside in that cold other than sit by a campfire
I fine tune the long range steel loads at around 75 degrees.more often than not. That way when its blistering hot, i wont run into unexpexted pressure signs.
Dave M.
F-Open Class shooter (284 win, 6dasher, 6.5-7PRCW)
Powder type? Cartridge? Discipline?
If I know the width of my tune, I will adjust my match load to the weather at destination. I live in the PNW which is colder, but not Mid-West cold. As an example, if I am developing my load over winter (right now) and then flying to AZ for SWN, I will load at the lower end of my node. If I am developing a load over the summer and flying somewhere expected to be colder, I will load at the higher end of my node. Pretty simple rule, but the key is knowing the width of the accuracy node.
Ned Ludd
Silver $$ Contributor
IMO - the best thing one can do to address such a question is to measure velocity using a "standard" load across the range of temperatures they are likely to shoot. Only then will they actually know how much effect, if any, that temperature has on their specific powder/primer/bullet combination. So one can do some testing and cover the temperature range they typically shoot, record the velocities, and then adjust charge weight to compensate, if necessary.
Although there are powders that seem almost completely resistant to temperature effects across a fairly wide range of temps, they are few and far between. Even powders widely considered to be relatively insensitive to temperature effects such as Varget can exhibit measurable changes in velocity using a standard load at different temperatures. In my hands, load velocity with Varget might change as much as 0.5 fps per degree F, which translates to somewhere in the neighborhood of about 0.1 gr of powder for every 10 degree change in ambient temperature. If someone desires to compensate for temperature effects by changing the charge weight, it is a simple exercise to make up a "standard" load that is safe and test across a range of temps. At the same time, they can make an estimate of exactly how much a given charge weight is worth in terms of velocity in their specific setup, so they know approximately how much to to tweak the charge weight to keep the velocity relatively constant.
Although there are powders that seem almost completely resistant to temperature effects across a fairly wide range of temps, they are few and far between. Even powders widely considered to be relatively insensitive to temperature effects such as Varget can exhibit measurable changes in velocity using a standard load at different temperatures. In my hands, load velocity with Varget might change as much as 0.5 fps per degree F, which translates to somewhere in the neighborhood of about 0.1 gr of powder for every 10 degree change in ambient temperature. If someone desires to compensate for temperature effects by changing the charge weight, it is a simple exercise to make up a "standard" load that is safe and test across a range of temps. At the same time, they can make an estimate of exactly how much a given charge weight is worth in terms of velocity in their specific setup, so they know approximately how much to to tweak the charge weight to keep the velocity relatively constant.
Last edited:
...and then there's air density. Lol!
The answer somewhat depends on what you expect from your load. The method Ned Ludd describes is a good one and tends to work well for maximum load charges.
I don't normally load for smallest group but consistency in point of impact. Using the more temperature stable powders like IMR 8208 and 4064 the loads have excellent accuracy in 20-100F temperatures. I use the OCW method of development and will usually do load development in the spring with 60-70F temperatures and choose the load that's in the middle of the "node". If I develop a load in hot weather then I will choose a load on the high side and if it's cold I shade towards the low side. I also stay away from maximum loads.
Years ago I was working on loads for 223 and H335. I made a mistake of developing a load that worked at 50F, as I recall, but made the mistake of leaving the box in the sun for some time then shot that load on a 95F day. The report was different, the recoil was different and it took a 2x4 to get the bolt open. The load was slightly less than Sierra's maximum in Edition V. Since then I've avoided double based spherical powders and worked with extruded.
Quite.
40 is Tee Shirt weather in Minnesota.
.....and shorts.
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.