208 ELD-M & IMR 4166 load development

Thought I would post my results. Pretty good powder. Meters ok. Had 15-25 mph winds so grouping didn't go so well. 52 degrees. 3 shots per set out of my 10T 308. Labradar chronograph.
Lapua brass, Fed 210 primers. Hodgdon reload web site showed max load at 40.2C so I know I was pushing it.
37.0 gr @2280.5 fps (avg)
38.5 gr @2355.9 fps
40.0 gr @2427.1 fps
41.5 gr @2510.8 fps (best grouping)
43.0 gr @2592.4 fps (2 of the 3 primers had slight black powder around the edge)

To compare with varget, the furthest I got was 39.6 gr @2381 fps. Anything higher I started getting case swipes.

It might be wise to increase your charge by 1/2 grain increments, in the future.

When I get this high, I usually go .2 grains if I go further. Or start backing off when I see problems like I posted above. Will back off .2 gr with 5 sets of 3 shots until I don't see issues.

I recommend going .5 increments too. Anything more than that then you're potentially missing a sweet spot. Let us know if you're able to get those 208's to shoot.

I'm wanting to load those 208's too, but it'll be for a 300 wsm.

It appears your lot is a bit different than what Hodgy tested as well. If you look at their data versus yours, you can see that you are a bit slow near the starting loads; which is completely normal, but you overtake them once you hit about max by charge weight. That tells you that the load is getting a bit cranky for whatever reason as the burning rate speeds up that quickly.

I just did another batch a week ago. Wanted to tone it down and get close to fps what hodgdon posted. Think I will drop a little more.
41.7 @2553.12 *High spread between shots* Low shot 2533.35, High shot was 2572.89
41.9 @2545.96 *Best groups*
42.1 @2546.31
42.3 @2566.78
42.5 @2570.00

very surprising results. I didn't think 4166 could get those types of speeds especially with a bullet as heavy as that.

making me want to screw my .308 barrel back on and try those 225 eld-m's with 2000mr I have setting on the bench.....

One thing to note. I use 3 shots per set of powder. Same brass, etc as before. Am still getting 1 powder seep around the ring of the primers out of 3 shots. The primers are not flattened, no case swipes observed, ejects fine. Will still back down another set until all primers are clean. 4166 was a surprise to me too. Just happened to come across the load data and happened to have 1 lb from trying a couple years ago for my AR10. Am liking it though. Its very close to IMR 4064, but cleaner burning.

Made up another batch to try. 41.5, 41.3, 41.1, 40.9 and 40.7. Hoping not to see any powder burns around the primers as before. Hodgdon lists max at 40.2C. Hornady doesn't list IMR 4416 in there book.

Looking at my StrelokPro software at both the 208 ELD vs the 178 ELD, using 2553 fps (lowest I have shot) for the 208, the 208 ELD @1000 yard is 1427 fps with 941 of energy. The 178 ELD is 1351 fps and 722 of energy. Speed isn't much difference but the energy is a bit more for the 208 ELD. Was hoping to get to the range this week and see how the batch I worked up will do. Rain all week unfortunately. Will be a little slower but have to insure no powder is seeping by the primer pockets.

What coal are you loading the 208's ? and how far off the lands ?

I had a good 208 load for my 308 fcp-k (had because barrel is now toast). Found a tight load between 41.3 and 41.9 gr of Varget and settled between there at 41.6 gr, 2,450 fps, 24"bbl. But the COAL was 2.940", 0.005" off the lands.
I assume at 2.800" coal 41.9 gr of Varget could of been over pressure, hence why I asked the coal you're loading them at.

yep. The 208 should be seated at something above 2.950 to get a good charge without the "powder seeping by the primer pockets". :o. BTW How does your bolt face look?

I seat match rounds 0.020 off the lands at 2.846 for the 208-M. The 178-X I seat at 2.810. Bolt face is fine. Am still loading over what hodgdon web site states to use. Will see what the next batch produces. I tried varget but wasn't the greatest. Take a look at Hodgdon reload site and see how varget and IMR 4166 compare. 4166 looked better to try. Hornady book doesn't list I4166 for the 208's.

FWIW: I tend to go with 1/2 gr charges when testing initially, then shift to 3/10 when I get into an area that looks good.

All new powder I will do 1 grain jumps but keep it below max levels looking for a clue as to what may be promising.

I usually do the same but went different this time. Since I am above max, have to go .2 gr to see where the issues disappear. Did some more research for other powders I use to see if anything better. 8208 comes up but 4166 uses less powder for the same fps from what I read.

Finally got out to the range today. Beautiful day. 72 degrees and calm wind. 3 shot groups using IMR 4166 with 208 ELD-M.

40.7 2504.44 fps (avg 3 shots)
40.9 2509.01 Best group
41.1 2514.88
41.3 2536.16
41.5 2539.32 1 primer has slight powder around it

Still not as tight of grouping like my 178 ELD-X do. Am done load development on the 208 ELD-M bullets. My next test will be with the 185 juggernauts.
Note the fps on 41.5 on my 1st post, then compare my resent. 52 degrees then, 72 degrees now. IMR 4166 is not supposed to be temp sensitive. Almost 30 fps faster with higher temps.