I started with a new lot of RL15 in my 470NE last week and it is apparently hotter than the last lot. I chronoed the 500gr woodleigh soft points at 2100 and my solids were running about the same or slightly faster (temperature in the mid 60's). Today the temperature is in the mid 80's and the softs were running 2180 and the solids were 2198-2200. The POI was only 1-1.5" inch lower than the 2100 velocity and regulation at 50 yards seemed just fine.

This seemed like a large jump in velocity for the temperature change. I have a buffalo hunt in Zim in August. I think the temperature range should be 50's in the early morning and as high as the low 80's in the afternoon. This gun seemed to be rather sensitive to velocity changes back in the winter but now it seems to shoot about anything.

I am shooting a 140-2.1 Merkel and the loads were 87gr of RL15, #2 Kynoch wad with 500gr Woodleigh SP and 86.5gr of RL15, #2 wad and 500gr Woodleigh solid--Fed215M primers with all loads.

I might consider dropping the load a tad(1-2 gr.) and see what she does.

Geronimo

ED, You might want to try H-4350 powder in your 470, it will fill your case more and give very stable velocities @any temp extreme. I know it may sound stupid but i have frozen 500 nitro rounds in the deep freezer, and then cooked them in the 105 degree Oklahoma sun, then chronod both batches of 4 rounds each and only had a difference of 18 fps. Hodgdon extreme powders work very well for me, I have a friend with a 470 Jeffery that loads 112 gns of H-4350 with a 215 mag primer and 500 woodleighs for 2155fps from 28 inch barrels, regulates perfect. He stated he will not touch another powder for the Jeffery. Good luck Jerry

The H-4250 loads are pretty consistant, but I think no more so than the RL 15 loads. The one downside I can think of is that with IMR-4350, H-4350, or H-4831 there will be a noticeable increase in perceived recoil over the RL 15 loads. It seems to me that the change in velocity may be due solely to a different powder batch.

Geronimo

I definitely agree part is due to the powder lot change. I just never checked velocity change with that 20 degree change in temperature with RL15. I did back off the loads in the solids since my original load was already running 2125mv. My original load with the softnose was slightly under 2100 on average so I left it at 87gr to see what they changed with the new lot of powder. They increased to 2125-2130 with the temperture in the high 60's-low 70's. The solids even with .5-1gr less powder were running 2145-2150 at the lower temperature range and jumped to 2198-2200 with the temperature in the mid 80's. This looks like about 50fps increase with the 15-20 degree change in temperature. Does that sound right?

I could see a 35 degree change in temperature morning to afternoon in Zim in August. The gun seemed to shoot to the same POA give or take an inch or two and shot together---softs 1.5 inches apart and solids were less that 1 inch apart without crossing.

The felt recoil was noticeably heavier at 2180-2200fps, almost like using 4350 or 4831.

I usually hunt Zim in August or September and I generally try to develope an average load in the 2125-2150 fps. range just before a hunt. Even in Michigan it is pretty hot that time of year, so temperature is not really a factor. I think you will find RL 15 to give very consistant velocities within a given batch of powder. But, as with all powders, when you go to a new cannister, you may want to back off a grain or two and work your way back up.

Geronimo

Geronimo,
I have a new chronograph and I thought it may be fast compared to one I borrowed but I checked it with a 300 Win Mag and it was right on. I think I will load some test loads down a grain or so and try to find a morning over a weekend that is around 70 degrees. We have had abnormally warm weather for the past week in North Carolina. My original plan was to target 2125 since that is where it shot best last fall.

I was amazed how well it grouped at 2175-2200fps.

I when to the range early this morning and retested my original loads while the temperature was 69-70 degrees. The 87gr load with SP's chronoed at 2080 and the solids with 86.5gr of RL15 were right there at 2075-2080. The reduced loads at 85-86gr were in the 2025-2040 range of velocity. I fired 4 rounds (2 solids and 2 softnose) as my last group with my original loads for the solids and softnose and they were all on a 2" dot I used for a target. I guess at 75-80 degrees the velocity will be approx. 2125-2150 since it chronoed 2175-2200 at 85 degrees.

Hope this works.