RL-26 Temperature Drift Data

[Engineering101]

trentcamp

You have to decide for yourself if RL-26 will work for you. I'm using RL-26 because it provides significant performance gains. I'm also aware that it drifts somewhat with temperature. Not crazy like RL-22 but some. I'll do what it takes to use it successfully such as load development in temps similar (+/- 20 degrees) to what the ammo will be used in. If I find I need to use the ammo in temps that are likely to knock the load off the accuracy node, I'll develop another load for the new temp - which basically means you have to change the quantity of powder used to get back to the same velocity that worked before. Its not like that is hard to do. I also won't load a bunch of ammo to sit in a box. I'll load what I need when I need it since at that point I will know what temperatures I'm going to be in.

 

[Double Dropper]

I guess at the end of the day we have determined that temperature, humidity, ambient fire arm temperature (not just the ammo) elevation, velocity, all can have an effect on our POI. How much is the real question. If youre willing to shoot 1000 yards ( I am not) its a huge concern, if your not willing or capable of shooting past 300 yards ( 75% of hunters ) I wouldnt worry, just my opinion, but the long and the short is when you get to hunting camp check your POI gun)

 

[degreen]

I have just started researching powders, and their sensitivity to temperature. In my research I have found that there is just to many variables to try to figure out. Do you load rounds to cover for every 10 degrees to keep your POI the same, or do you just deal with the possible velocity drop of a more temperature stable powder. I am a KISS person. The charts I have seen for the more temperature stable powders show that if you were to zero your rifle in cooler temperatures you should only see a +/- 20 fps change over a 100 degree shift in temps.

 

[Pdvdh]

No matter what a guy does to plan for temperature affects on MV and POI, he should still shoot the rifle to verify POIs in the field conditions, preferably in the vicinity and elevation of the hunting grounds just prior to the hunt. If we already know our MV at the temps we'll be hunting in, then the primary remaining information needed to shoot responsibly and confidently at long range, is the rifle's zero.

So there may be some benefit to loading differing powder charges for differing temperatures with some rifles, but I have no interest in that practice as a first approach. The more potential for error and use of the wrong ammo built into my equipment preparation, the more apt I am to goof up in the excitement at the time of the shot.

I'll shoot my bullets a little slower in the cooler temps, and try to confirm any shifts in POI or degradation to precision as my preferred and first approach. This has proven viable and functional for my hunting conditions in Alaska. It would be rare for my temps to change more than 20*F from pre-hunt POI verification to the time I'm pulling the trigger on a game animal.

Of course, others should consider the anticipated changes in environmental conditions at the location and altitude of their hunts. There may be better options if temps will swing 60*F during the huntable portion of day's hunt. I just don't see that kind of temperature swing and can tolerate and adjust the temperature shifts I experience with my chosen methods.

 

[WildRose]

wildrose

Let me say that it is good to be conservative when dealing with any form of gun powder and that your wife is a smart women to suggest protection. However, with knowledge you can do certain things that can prove advantageous. For example, I have had QuickLoad for years and one of the things it makes you aware of is what happens when you put a powder in a case for which the powder is way too slow because it will list loads for all powders with the top performance (highest velocity) at the top of the list. Invariably the powders on top are all way slow and load densities are like 115% or more because QucikLoad assumes it still fits in the case. (You can setup QuickLoad not to show loads past a certain compression). Anyway you then pick a powder down the list where load fill percentage is closer to 100%. Just the process of picking a load makes you aware of the performance you could get if you went with a very compressed load of a really slow powder. For certain situations I've overstuffed cases with the bullet seated to just about contact the powder then remount the press upside down to do final seating. That will get you a couple of more grains in the bigger cases without compressing the powder. Very fun with a nice performance boost since the powder takes up the space surrounding the base of the bullet before the bullet is pressed home.

I started off handloading around 1978. I was thinking 82 but it was a couple of years before I graduated HS. I started with the old all in one box "lee loader" that you had to use a hammer to punch out or seat primers and to resize your cases! A good family friend who was as close to an expert as you can find on the subject started helping me vastly expanding my knowledge base and upgrading my equipment dramatically. By the late nineties I was turning out very accurate rifle loads and thousands of 12g loads each year.

In the eight years or so since I found this site I've learned more than I had in the entire three decades or so prior. If the answers aren't to be found here at least there's always very good questions which lead one to search the other available data sources on the web. Sometimes just knowing where you can go look something up to me at least is even more valuable than having someone just tell me what the answer is.

Quickload may well be the next step for me. I've just spent so much upgrading everything else this year I have a feeling that my wife might appreciate it if I upgraded some things around the house for her first. She's been amazingly patient and understanding over the last ten years as we added more rifles, handguns, and shotguns not to mention good supplies of ammunition for each and then of course with the rifles I also had to upgrade optics.

I have good friends that I respect a lot who have always tended towards using compressed loads and had sensible reasons for it but it always made me nervous. I know that bur rates tend to go up dramatically as pressure increases and having come close to blowing one up in my face years ago I've probably just naturally been a bit over cautious.

 

[WildRose]

I am currently loading with very favourable results RL-26. Realistically if I shoot all summer with load A, and when the weather gets cold, double check the zero ( summer 75' F and winter -25 F) and the zero is very close or almost the same, as long as I know the velocity is there really and issue? They all shoot slower when its colder, got that, highly unlikely I would shoot past 600 yards. My ballistic calculator (200 grain Horn ELD-X @ 2950 fps 75'F) is 54.7 inches low @ 600. IF it dropped to 2875 fps @ -20 degrees the bullet drop is 59.7 inches or 5 inches @ 600 yards. I understand there are many variables but for hunting ( assuming the POI is checked under cold conditions ) is this a problem?? Shoot most people cant hold 5" difference under hunting conditions.

The further the range the more critical everything becomes. You're hitting right around a point I make frequently which is that things start getting complicated beyond 600yds and extremely complicated from 1,000 and beyond.

Most Hunters can't hit a 8" paper plate at 100yds so the thought of anyone shooting anything at 250 just boggles their minds.

Most of us here though aren't the average guy or gal and we try to squeeze that nth degree of accuracy out of every rifle and every round we shoot.

 

[codyadams]

I don't understand what the big issue with temp drift is guys, all the better ballistic apps can account for this, and after some pretty simple testing it is a known factor that can be accounted for similar to range to target. The only time I seeing it becoming an issue is if you drop or gain enough speed that it takes you out of your accuracy node....

 

[Gord0]

The further the range the more critical everything becomes. You're hitting right around a point I make frequently which is that things start getting complicated beyond 600yds and extremely complicated from 1,000 and beyond.

Most Hunters can't hit a 8" paper plate at 100yds so the thought of anyone shooting anything at 250 just boggles their minds.

Most of us here though aren't the average guy or gal and we try to squeeze that nth degree of accuracy out of every rifle and every round we shoot.

Some hunters I know look at something 100yds away and think it is 250. I guess that's a good thing as they won't shoot at it

 

[Wedgy]

I don't understand what the big issue with temp drift is guys, all the better ballistic apps can account for this, and after some pretty simple testing it is a known factor that can be accounted for similar to range to target. The only time I seeing it becoming an issue is if you drop or gain enough speed that it takes you out of your accuracy node....

Doesn't the Kilo 2400 have some adjustment for this ?

 

[Pdvdh]

I don't understand what the big issue with temp drift is guys, all the better ballistic apps can account for this, and after some pretty simple testing it is a known factor that can be accounted for similar to range to target. The only time I seeing it becoming an issue is if you drop or gain enough speed that it takes you out of your accuracy node....

It's a lesser deal if the only affect is the bullet leaves the muzzle a little faster or slower. It's a bigger deal if in addition to leaving the muzzle at a different velocity, the bullet is also pointed in a different direction.

 

[codyadams]

Doesn't the Kilo 2400 have some adjustment for this ?

Not necessarily the 2400, but the applied ballistics application for the sig 2400 has it. And other applied ballistics apps.

 

[codyadams]

It's a lesser deal if the only affect is the bullet leaves the muzzle a little faster or slower. It's a bigger deal if in addition to leaving the muzzle at a different velocity, the bullet is also pointed in a different direction.

That would make a little more sense. I have developed loads before that while going up in charge, the POI changes not just vertically, but horizontally as well. However, I personally have not seen it change over 1 MOA, if even that, and even that sub MOA POI spread is usually over 100-250 fps spread, which even if the powder changed 2 fps per degree, which is alot, that's still a minimum of a 50 degree change. If the powder is 1fps per degree, your looking at a minimum 100 degree change to make even 1 MOA of change.

But, I guess that's just even more of a reason to practice with your gear regularly and in the field, and not be one of the guys that shoots their rifle once a year a few days before season to make sure you can hit a milk jug at 100 yards off a solid bench and then call it good and shoot at animals at 400 yards away. Lol. FAR too many of them.