Well it’s officially here. Summer time here where I live means 90 plus degree temperatures with 90 plus percent humidity until at least mid September. Deer season starts in mid-october where it’s going to be in the low to mid 80s in the day and by the end of season in January will probably be in the 40s.
I’ve got one gun I want to finish load developing on, a 28 Nos with ABLRs and another gun I need to start load developing on, a 7 PRC with LRX.
I know it’s going to be challenging with trying to stay out in that type of conditions. Cool down time for both the rifle and the suppressor are going to be significantly longer than usual.
But is there concern for finding a load which gives a nice tight group now only to find that it opens up significantly when the weather cools down?
I don’t know that I’ve observed a load’s accuracy bei mg better or worse given the temperature when compared to other loads.
However, you may pick something that the velocity won’t be good in a different season. You can fix that by choosing a temp stable powder.
A lot of guys also control for this at some point in the testing by putting the ammo in the fridge and bringing it to the range in a cooler. Take it out, put it in the cartridge right away, and shoot it. Then you will know how it’ll perform in the fall.
Do load development, note down the velocity that worked well, then add or remove powder to match that velocity for a different temperature (obviously this isn’t going to take you from an Arizona summer to hunting polar bears, but should be fine for summer → fall). If you’re loading really close to the limit don’t use your winter ammo for plinking during the summer.
After shooting, I put a barrel cooler in the chamber and set the gun in the shade leaned up against my truck so the heat goes up and out the barrel instead of being trapped if the barrel is horizontal.
I will be curious on your 7PRC load development. I am going to start with the LRX bullet and H1000 powder. I plan to start are recommended COAL all as published by Hodgden.
I’ve shot some LRX loaded by Choice Ammo, and it works great. Plan on initial seating at same depth as that stuff since it works so well (but very expensive).
4831SC will be my first powder since I have a couple of bottles already for another gun that it didn’t work for. Also have some Retumbo sitting around. H1000 would almost certainly be next, but holding off as I would have to purchase some of that.
I have two boxes of the Choice LRX. Based on my past experience I am sure they will shoot well, just don’t like to pay $5 plus shipping fees with each trigger pull. I have a pound of the 4831SC but am seeing where it burns a little fast for the 7 PRC. Obviously I will try it, but going to start with the H1000 at two grains below max.
Berger also sent me some load data with their 175 grain elite hunter bullets. They are getting right at 3000 FPS with this bullet and H1000 - let me know if you want me to send that your way. My only challenge is that 24" barrels were out of stock when my build was going on, so I opted for a 22" - I expect I will see 2950 or so FPS.
Similar to what Jim responded, I use a homemade barrel cooler. I bought a rechargeable air pump from Amazon and about 18" inches of high temp tubing. If I limit my groups to 3 shots, it never gets too hot and I’ll run the air pump for 5 minutes in between groups and I’m good to go.
I tried to continue my load development on my 7 PRC today. I live in Vegas, and it was around 114 today. I was shooting from a bench rest in the shade but decided to stop because I was getting signs of over pressure in both the factory and custom loads. Extremely stiff bolt, bolt face marking on the case head, and deformed case ejection lips. The precision hunter actually blew out a primer, so I stopped after the second shot of that. I even had all my ammo in a cooler so it should have been relatively cool. Here are a few pictures.
I imagine that when it is a 114° outside, the barrel stays pretty hot, and it probably only takes a few seconds of being in the chamber to heat through the thin metal of a case, so I don’t know if keeping the ammo cool before hand actually does anything to help. Just my speculation.
Maybe the only true way to know if it is the load, (too hot) is to take the same box of ammo, and save it till the fall when the temps are back into the 50’s. If it still does it then, it helps to eliminate a variable as to what is causing it.
As much as I hate it, I don’t shoot a lot during the summer heat for a couple of reasons.
The barrel will just not cool down for a long time after 4-5 shots, and the temp 85 or higher.
High humidity - gives me the shudders thinking about moisture creeping into all the internals of my weapon (but that is just me - can be defeated by good cleaning and oiling).
The data gather is not all that useful during hunting season temperatures in most cases - good to know, but shooting in 30 degree weather changes things.
It may not blow up your weapon, but slamming the extractors, springs, etc., willo eventually weaken or crack those items. Come hunting season is right when half of your extractor pin will fall out…
Have only ever experienced one blown out primer, and that was in Texas, in summer, shooting in the shade, but it was 90+ outside (it was a hot handload), and I have never experienced a factory blown primer.
Seems to be, only by casual observation, that the velocities quoted by ammunition manufacturers for the 7 PRC appear to be pushing the edge on pressure for everyone. When a machine operates right on the edge of any tolerance, it increases the likelihood than even a small change in a variable can cause an issue. I don’t have data to support that the 7 PRC is an issue as a round, but I haven’t seen these types of comments for 300 Win Mag, another high pressure, large powder charge cartridge.
Good luck
If you learn how to use GRT or quickload you can predict temperature effects on your loading and adjust your powder charge to compensate with a high degree of accuracy. Here’s the same charge of a “temperature insensitive” powder gaining 50 fps and going overpressure from 50F to 114F.
