I’ve been developing some loads for a 2022 buffalo hunt using my 416 Remington Mag. The bullets of choice in this case are 400gr. Nosler Partitions and Barnes FN Banded Solids. I also loaded the old style 400gr. Hornady FMJ as a practice load. Being a little light on stock of the medium burn rate powders at the time, and with the spotty availability of RE-15/Varget/4064, I decided to give one of the IMR Enduron powders a try – IMR-4166. This is their Enduron entry in the medium burn rate category, and they list data for it on their website. Seemed reasonable to try. They list a max load for the 400gr. Bullets at 75.6gr. In the interests of safe pressure, case life, and simply not wanting to push the envelope, I went from 73.5gr. to 75.5gr in .5gr. increments with each bullet tested. Powder charges went from not compressed to very lightly compressed.

Shot them yesterday on a cool, humid July day in PA and was underwhelmed with the results to say the very least. From the very starting loads, I was seeing pressure signs on the cases. Primers were pretty flat and showed increasing cratering as I went up. Extraction seemed fine, lightly sticky if anything. It was apparent right from the get-go that this was not an appropriate powder for this application. I actually blew a primer on one of the max charges using the Hornady bullet – troubling! Not one of the bullets or loads reached 2400fps, and the spread between the top and bottom loads was only about 50fps. The whole process seemed to struggle to get anywhere. The one other component – accuracy – was, well, crappy! My rifle will group three shots into 1.5” with some other loads I have. All three bullets were in the 2.5-3.5” range with all loads.

So, the experiment pretty well bombed in this case. All of the markings of a good load ranged from insufficient to downright dangerous. Not sure if any of you have experiences like or unlike mine. I still like the Enduron powders and will give 4166 another go in a different cartridge where it’s maybe more at home. I might try it with lighter bullets in the 416; I have a ton of the 350gr. Speer Mag Tips.

The funny thing is, since I loaded those test rounds, I’ve acquired fresh batches of both RE-15 and H4895. Both of those are pretty tried and true for the cartridge and should give me better results. It’s back to the drawing board with some lessons learned.

Give Varget a try.

Another vote for Varget!
With the 350 gr Barnes, my rifle will shoot close to 1/2" 5 shot groups...

That might be the move. I'll certainly try RE-15, but Varget is a close second on my list. I'll have to keep my eyes open to find a pound or two. That seems to be one powder my local store never seems to have.

Did either of you have trouble hitting 2400fps without any weird pressure signs?

No pressure signs with the 350 gr Barnes.

My best loads with the 350 gr Speers was with BL-C(2) and Fed 215s. Very consistent 3-shot, 1 inch triangles at 100 yds, with velocity near 2600 fps.

I have been shooting a few loads with 4166 in my 416 Rem. Basically just testing for velocity, haven't tried to shoot a group yet. 73.5 gave me 2350 with a 400 gr Swift Aframe which is the goal. 75.6 was 2400 fps in my gun. Primer's are fairly flat but not cratering. I shot some of those in 105 degree temp one afternoon. RL-15 was really accurate in this gun and I may try some IMR 4064.

quote:

Originally posted by Gale Johnson:
I have been shooting a few loads with 4166 in my 416 Rem. Basically just testing for velocity, haven't tried to shoot a group yet. 73.5 gave me 2350 with a 400 gr Swift Aframe which is the goal. 75.6 was 2400 fps in my gun. Primer's are fairly flat but not cratering. I shot some of those in 105 degree temp one afternoon. RL-15 was really accurate in this gun and I may try some IMR 4064.

Interesting and good to hear. It was only 70-75 or so when I was shooting, so I'm way off your tropical test session. I have RE-15 loaded up since the initial post and will swing by the gun store at some point to see if anything 4064 or Varget are available. Your velocity results are similar to what I was seeing, though mine were a bit lower on each end. I'd be curious to see how your rifle groups if you ever decide to shoot for that.

When you are burning 70+ grains of powder I would start lower than 2 grs below max.