Home Forums Reloading Big Game Rifles Got IMR 4166 today, first impressions on loading

Got 8 lbs of IMR's new "Enduron" powder 4166 in today for use in my 308. I normally prefer IMR 8208 XBR for the 155's that I shoot but couldn't find any in stock as I'm running out and I love to tinker with new things. Have a workup loaded with 155 Scenars ready for the range on Wednesday. I'll update the post with some basic firing info after that but wanted to put up a pic to show the granule size for those curious as IMR touts in their press release that it is short grained to flow smoothly through powder measures. My opinion is that is misleading or at least not what I was hoping for but I'll let you be the judge.

New label:




Below is a pic of the new powder next to some other extruded offerings I have on hand. You can see that 4166 has pretty thick granules, the only one in the group that has longer grains is old school IMR 4831 which is like trying to run toothpicks through my Redding powder measure. I'm putting this out there for those who may be wanting to use 4166 in a progressive. You can see also that XBR has by far the smallest kernels in this group.



Looking at load data by Hodgdon my guess is that 4166 falls right between H4895 and Varget in burn rate but we'll have to wait and see when it is added to the burn rate chart. Only thing pertinent I can say at this point is that this powder is pretty bulky and gives good loading density. I loaded 20 rounds up for an OCW test from 43.8 to 45.8 grains in Lapua 308 brass with the 155 Scenar(Hodgdon data indicates min of 43.0/ max of 46.2c for the 155 SMK) and I started compressing powder at 44.6 while using a 5" drop tube and loading to a COAL of 2.835". At my highest weight of 45.8 the base-ogive length was 0.003" longer than the start load and had lots of crunch when seating. By comparison, I don't have any compression at all even at max of 45.3 with XBR (still have a tiny bit of shake space even) and don't start crunching until 46.0 with Varget. So take away from this what you will, hope it helps others make a decision.

I'll be back later in the week with a limited range report, my rifle got scrubbed clean tonight so I'll be able to have a look at how clean burning 4166 is. Barrel doesn't pick up copper much at all as is so not sure I'll be able to say whether or not their "copper killer" claim is true, but if I find anything unusual I'll report back here about it.

In my testing with a Redding BR-30 there wasn't any difficulty with throwing consistent charges, but I did find the granules a little too large to always flow easily into any case-neck smaller than .243".

Good day at the range. Not much to say about performance at this stage other than it appears to work. No velocity data, battery I brought with me for the chronograph was dead. Anyway, load development shouldn't be too difficult.

Rifle shows no obvious copper fouling with 22 rounds down the bore, powder fouling appears about what I would expect to see using XBR. Not very dirty in comparison with H4895 which I have always thought is filthy.

Temp was about 50F during this 100 round robin, there are NO pressure signs on any cases. Not sure how much further I can go with it to find max but what I've already fired shows enough to be workable without wearing out brass.

Looks good so far, we'll see how it does long term for temp swings and such. Would love to get some velocity readings on the 45.4 grain region, as I know I can get 2800 fps with XBR in this 19" barrel.

Thanks, Rye. Hopefully your 45.4 load has good velocity as it's pretty tight. Even 45.8 is very agreeable. Keep us posted. Also let me know if you'd like some one to test a little of your 4166 in a 7-08

Sounds like it'll be useful for a deer load in my lightweight 300 WSM.

Back again. Christmas season and my 6 day/week work schedule have not allowed much time to shoot but I got around to more testing this morning.

Previous test posted above had me concerned, while 45.4 shows a tight group its POI is not consistent with the ones surrounding it. For grins I did a seat depth test at 45.5 grains and got horrid results. Fliers in every group and POI that moved around slightly between different depths. Not good. I did get some velocity readings though, and averaged 2750 FPS via an Oehler chronograph at 7 feet from the muzzle with very low SD numbers in spite of the crappy groups. Slower than my XBR load which goes 2800 FPS out of this 19" barrel with a 7" suppressor attached. With no pressure signs up to 45.8 grains of 4166 I decided to push further and see what I could get.

Below you will see today's round robin from 45.0 to 46.4 grains of 4166. In today's shooting you can clearly see the scatter that centers at 45.5 and the obvious OCW at 46.2. It was pouring rain and I had my 4 year old son with me (he loves watching Dad shoot) so I didn't get the chronograph going but I will next time out when I check seating depth at 46.2. I'm going to guess 46.2 grains will probably get a little over 2800 FPS, I'll keep updating as I find out.

Loading note: I used a paper towel tube to drop powder from the pan into a funnel with a 5" drop tube and had no crunch loading all the way up to 46.4 and seating depths were perfectly consistent.



Also found my limit on pressure today: 46.4 grains showed just the slightest bit of primer flattening. Right in line with Hodgdon's data. No other signs present. Shown below are 2 fired primers, 46.2 on the left, fully round and 46.4 on the right with the slight flattening. Pay no attention to any other signs on the cases, craters occur always as this is a factory Remington 700 and the ejector swipes are left from my old AR which this batch of brass started out in.
I pushed out some of these primers with a decapping die today and the pockets are still tight on all of them.



To those who haven't checked it, Hodgdon updated the burn rate chart and IMR 4166 is located right with IMR 4064 which doesn't surprise me at all. Link to updated burn rate chart is below.

https://www.hodgdon.com/PDF/Burn%20Rates%20-%202014-2015.pdf

Call me crazy but I don't see a 2 + 1 flier when you're talking 7 groups with 1.2 grains difference in powder charge and the average MOA being 0.7" and the same POI being basically within an inch square if you were to overlay all of the last 7 groups. Therefore, pick a nice round number in the middle and pile up a bunch of critters with it. I'm sure they won't bitch if a perfect broadside shot is off by a half inch.

Good luck!

RyeDad....thanks for the good info and the nice job of reporting. I also like the 8208XBR but after seeing your tests I might pick-up some of this new 4166. Never hurts to try some new stuff.

Yep, it's all the same group.

I've been playing a bit with 4166 in a couple of my 308's, a Rem. 700 5R and 40X to be exact. It's performing quite well with 168 grain Hornady HPBT bullets in Hornady match and RP brass with WLR primers.

I'd be interested to see how it goes with 168's. This is a 5R also, just had it cut to 19".

With no tuning for length, primer choice, and thrown charges about 43 to 43.1 grains it's giving .5 to .6 MOA at 200 yards, as guided by 6x scopes.

Soon I'll put on the fine reticle 6.5-20x40 and test primers.

What speeds mathman?

I haven't clocked them.

Tested seating depth today. GREAT results!

46.2 grains IMR 4166
155 Scenar
Lapua brass
CCI-200 primer

Numbers in blue marker on target are base to ogive measurment, add 2.2 to the beginning. (IE: 30 = 2.230" B/O) Oehler derived velocity averaged 2805 FPS for all 15 shots combined.

The three rounds of the 2.230" chrono'd 2804, 2804 and 2805. Ya think that'll work?



Also, cleaned the rifle with Butch's after returning home. Barrel had around 60 rounds since scrubbed clean and was only fired with this powder and these bullets since then.

This is the first patch pushed through after soaking in Butch's:



You may not be able to see but it has just the very very slightest blue tint to it which is less than I usually see at this point with Varget. Wasn't much carbon either, even using a suppressor.

IMR 4166 appears to be the real deal. If it proves temp stable over the next 6 months I may never buy Varget or XBR again.

PS, in case anyone missed it this is not a custom rifle. It's a Remington 700 5R that has been cut to 19" and threaded and I bedded it in the HS Precision stock using Devcon 10110.