No, it's not. However, Hodgdon lists velocities (or at least used to with their US859 add) with essentially zero velocity change over a huge temp range WITH THE 50BMG. However, most folks using it here are finding that it is not temp stable, I believe. But, like I said and many others attest to, neither are the Hodgdon Extreme powders (like Retumbo). When you are dealing with the heat you have, you probably need to work up a load that's safe during the higher end temps you're expecting to hunt in with any powder you may consider using. The Extreme powders may be a little more forgiving in this regard than standard powders, but there is no 'holy grail' of 'all temperature' reloading from what I've seen.
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I personally have only worked with the 300 RUM while helping out Tim when he got his. We tried several of the above mentioned powders. At the same time I was also working up loads for my .270 AM using the 872 and 869.
The thing we found with most of the loads and powders we worked with was, we could not get close to the charges most are using with some, but could get better with others. I don't feel that this was more due to extreme differences in powder lots, than differences in where we are, compared to where most here are.
We're still getting the velocities that most are, but the climate here is such that some of the popular powders will max out generally 4 - 6 grs below what some are using. The H-1000, was the winner for his RUM and so far I have settled on a load with the AM using 92.5gr of 869 for a 3260 velocity. The RL-25 which we tried three different lots of was the worst case of this. Loads would go from good to close to blowing the primer out within hours of loading them . Just due to the temps and changes in humidity. Yes they were up there, but were fine at 65 degrees and blowing primer pockets at 85. It works great for others, but not for the area we hunt and shoot in.
I am now working with a 7 STW and am finding the exact thing mentioned above. Similar powders showing differences of a couple of grains going from mild to mean with just a change in temps and conditions. The trouble is we go from winter to summer on a weekly, and somtimes daily basis, not to mention that you can actually see and feel the humidity change from a nice 40% up to 70% plus and the temp remain fairly constant. Just takes a shift of the wind and a few hours. Not to mention the pressure swings as a high system moves through followed by the rebounding low system. FWIW - it seems when you get case capacities above the 70gr mark, that the powders used take on a whole new character. I can shoot any of the Reloader powders in my standard 7 mag, or smaller cases with hardly any noticable change in things, but once you get above that limit things start to differ.
The folks who live down here in the balmy South should realize that the humidity and lesser altitudes play an important role when you get up in the bigger powder charges using these slow powders. I conversed with Lerch and Bill both while working up my loads and I still could not get up to the charges they were using, but then again, they are some 500 or so miles north of us and their climate is different.
My recommendation would be for those of us in Tx to try to work up your loads on those mid June and July days when you can spit steam, and the humidity is dripping off the roof. Then you know your set for our terrible 30 degree winters. The coldest day we have been able to shoot in was around the mid 30's so far, and it only changed the drop about 1" at 500yds on our loads. We weren't able to check the velocity due to the rain but figure it is only a matter of time before we will hit a clear morning and similar conditions.
I do know for a fact that I shot some of the 869 in June, and it was in the mid 90's, that trip I put a couple of rounds into the ice chest we had our drinks in and dropped them down to around 65 degrees. I noted a drop of 200fps between the ones I had sitting ambient temp in the box and shaded. I also know that this works just the reverse as I ironed out a couple of case heads, (primers were toast), just a short time before then with a similar load.
Just some tid bits I thought I would share. Bottom line is like GG said, the powders will tell you which one is going to work. You will have to determine how it is being effected in your rifle under your conditions in the areas you live. What works here or there might be on opposite ends of the stick. If your headed from the flatlands of the Gulf Coast to the peaks of some mountian range, the best you can hope for is to try and meet in the middle. One thing for sure, if your load is on the upper end down here, your probably fine going up, but the opposite isn't always the case.
To tell you the truth, I seldom ever look at reloading manual's maximums. It means nothing to the individual gun I'm loading for. I watch the pressures and the chrono, and if they say I can go up more than I do. If it is above listed max then it is above listed max.
Goodgrouper I could not agree more. I appreciate what youre saying. Most of my rifles are custom and I have never been able to reach maximums. I was amazed with your numbers on IMR 7828 and it mainly was because I had worked up a load that for my 300 Ultra with a gunsmith friend and it was extremely accurate and worked great. I was using powder the smith had on hand. He had a new can I took and loaded rounds from that were still accurate but blew out primers and wanted to lock the bolt which I knew was not good. It really puzzled me and I even took the same rounds up your way in the mountains and had the same reaction. I figured that if the rounds shot hot in Texas that being higher in the mountains and higher elevation with cooler weather would make some difference but it didn't. My smith friend tells me he believes that when IMR was sold to Hogdgon that there were some lot problems,and our cans were not 7828, who knows.
I really appreciate the input as I am only one wandering around out here and it really helps to hear what others have experienced. Heck my bet is you have probably forgotten more than I will know. [img]/ubbthreads/images/graemlins/wink.gif[/img]
thanks for the reply. I have not found much difference in lots except with IMR 7828. I think that may have had something to do with a change in ownership in companys but who knows.
I have not tried 869. I read good thing and hope to try it soon.
Nice to meet you so to speak and South Texas is a great place to hunt and spend time. Better than being cooped up in this big city.
Did some testing of the 300 Slowpoke this weekend (300 RUM is the parent with about 5.5% less capacity) and when the wind blew the 35P over for the 3rd time I quit for the day but with the 210 and 200 gr pills the US 869 and H1000 worked well Retumbo did not but the H870 was the best by far with 109 gr with a 210 Berger giving 3289 avg over 5 shots and a 24 fps high to low.
Glad I bought 2 more 8lb kegs last week---my 30-378 loved 870 as well.
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I'm gathering parts for a 300 RUM project, I really like the potential of this round for my first long range setup. Correct me if I'm wrong but isn't the BC on the 220 matchking above .6?
What I've gathered from this post-Retumbo is the best extreme temp powder, but its best velocities are obtained at more than 100% case capacity?
US869 gets the best velocities at much lower pressures, but is very unstable at extreme temperatures?
What about h1000 and 870?
I'm in Texas also, and would like a round that I could shoot year round without have to reduce loads and all, but would like a little velocity potential as well. I've read this thread several times, maybe I need it dumbed down to my level, I don't have much experience yet in magnum cartridges (but I'm dyin to dive in!!).