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

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