I need another powder to play with like Texas needs more rain. Saw IMR 4166 in Cabela's today and bought some. Of course, I couldn't buy just one pound, I had to buy three in case it does good. After the two powders I chose last year did so poorly in varying temperature conditions, CFE223 and 1200R, I wanted to give this one a try. It's one of Hodgdon's new Extreme Powers and is supposed to be insensitive to temperature. I did plan on using this for 130 to 150 grain bullets with COALs longer than mag length. I will be able to use it in .223 and .308 if it doesn't show promise in the 6.8mm.

Anyone have any experience with this powder?

A lot of new powders came out during the powder/primer shortages and were scoped up in hopes of replacing an old favorite that was not available. I haven't bought anything new for fear I would like it only to find I couldn't buy any more of it. My favorite for both the .223 and the .308 is Varget and while I still have a few pounds of it, I haven't seen it for sale. I'll be interested to see how the IMR 4166 works for you. I've had good luck with IMR 4064 in the .308 and this new powder is very similar.

My inventory of powders is:

W231, H4831SC
WSF, 2400
W748, Clays
W296, AA#7

I am able to have a far reaching purchase power in that my brother-in-law is a truckdriver and when he is laid over he checks the stores for mine and a friends powder needs. He just scored me some WSF and H4831SC in Houston, Texas.

The above powders serve ALL my needs and ALL are accurate in ALL my firearms. When powders become easily available I will start experimenting again.

I hear ya Bushy....AR2206h is versitile to be sure.
just about out of it but have some winchester powder to keep .223 going till I get more
the load testing I did earlier trying to sort out .270 has chewed through nearly a tin of AR221sc
ASteel takes care of .12ga
wee tin of trailboss donuts takes care of subs

Compared to CFE223 and Varget, IMR 4166 doesn't appear to have as much energy potential when looking at comparative loads in .223, .30-30, and .308. Chart below is taken from the Hodgdon.com website.

IMR 4166 also is not as dense as the other two powders. Using a 6.8mm SPC Case filled to the neck, below is the weight of charge.

32.8gr IMR 4166
33.5gr Varget
38.4gr CFE223

If I used a drop tube I could get the charge for IMR 4166 up to 34.1gr.

When loading the 6.8mm with a 130gr ProHunter at 2.415 COAL, 31.0gr of IMR 4166 was max capacity. This load was using a 16" drop tube and some compression. I will start a powder charger vs velocity ladder at 29.5gr and work up from there using case head expansion measurements to determine when max chamber pressure has been reached.

Base on the above and below, I don't expect IMR 4166 to provide higher velocities even though it is a faster powder than the other two. When I get the load/pressure boundaries worked out, I can test its temperature sensitivity to see if all this was worth it.

IMR 4166 has more energy (produces higher pressures) but burns faster too which means that you will not get higher velocities with it.

Guess it just does nothin for me!Maybe just a fill-in for shtf!

The potential benefit of IMR4166 powder is the load you develop in the summer shoots the same during hunting season. I started doing temperature sensitivity testing after two powders I chose for my hunting loads went South in the colder weather. Loosing 50 ft/sec can make a difference at long ranges. The two powders, CFE223 and 1200R, were loosing 150 to 200 fps. Plus I get to "play" with something new which can be interesting.

www.huntingnut.com/ind...9&start=60

Was able to fire off a Powder vs Velocity Ladder with 130gr ProHunters this morning. Started at 29.0 grains of IMR 4166 and worked up to 30.5gr (a 16” drop tube was used). Pressure did not reach max chamber pressure. The IMR 4166 was close in performance to TAC and just below Varget. It may actually do better with 150gr bullets. Will test temperature sensitivity later in the Summer.