I was checking out the new Hornady #10 manual for 338 RCM load data and noticed that the published load data for
the 338 RCM is less than the 338-06.

This baffles me as the RCM case can hold more water (3-4 more grains) and is equivalent to the 338-06 Improved.

Hornady shows in most instances heavier powder loads for the '06 case over the RCM case.

Why is that?
Is this a SAAMI thing?

With case capacities being pretty much the same I would expect to use either or load data for each case.

Which also begs the question...Does case design matter?
I would think no, but?

Likely cause most RCM rifles are based off 20" barrels while the 338-06 in most load books is in a 24" barrel.

Yes, (20" verses 23") but the powder charges listed are LESS for the RCM case.

Doesn't make sense, especially when you look at Hornady Factory loads are loaded pretty stiff and getting quite the speeds.

http://www.hornady.com/store/338-RCM-200-gr-SST-Superformance/

Listed factory load of 2,950 mv for a 200 grain bullet compared to the Load Guide of 2,850 mv.

That just tells me they CAN load a higher pressure load.


I'm very impressed with this rifle/cartridge concept.

It is unfortunate there is little load data for this fun and very useful round.

I have two 338 RCMs. The sporter has a 22" barrel and once I came across this load I quit. I use the 225 gr accubond with 61 gr of RL-17 for 2775 fps.Mag box is 2.950", bullet seated accordingly. Super accurate, and has taken four cow elk to date. Would be more but hard to get an Az tag.

FYI the reamer is the exact copy of the one Hornady designed. I know because I had a conversation with Lonny before he retired.

The other is a LA Mark X that used the same reamer then a throating reamer was used to allow a longer OAL with 300 gr Bergers. This package has a 1 in 9 twist 30" barrel uses 56 gr of RL-17 for 2525 fps.

Hope this helps

Thank you!

I have some 225 AB's I'll try out.

61 Gr of RL 17 std primer, with 225 gr N Part. or N Accubond or Horn Interlock, bullets was the load I settled on in my 2 338 RCM,s. 20" barrels 2625 FPS Average about 1" in both rifles.

Keep hearing bad things about the Hornady 225 SST bullets being to soft, but they are accurate and fast in the factory load about 2690 FPS. Any real exp. with the 225 SST? Bought several boxes when brass
was hard to find.

I'll have to check my book, but I seem to recall 61gr RL17 was exactly what I ran with my 338-06 and 225 ABs.

61 grains is what got me 2690 fps in my 21" barrel 338-06

Have had ejector marks with Factory Hornady 225 Gr SST loads in my 20" 338 RCM very accurate.


No marks with my reloads with 225 GR loads about 2625 FPS in my 20" 338 RCM, any faster and was not as accurate.

IMR 4320 was the best overall powder in my former 338-06. 23" w long throat. 225's did 2670 + 1/2 MOA.

4064 and 200 NBTs is a killer deer load. 2910mv and 1/2 MOA.

Here's a thread...

http://forums.outdoorsdirectory.com/showthread.php/92858-338-06-2700fps

Thanks!

There could be differences in throating, etc. However, in checking my Hornady #9, there was no clear trend. Some loads were almost equal, some a bit heavier for one or the other cartridge. The biggest differences seemed to be for the 225 gr loads. As usual, I check different manuals and in this case both sets of Hornady data, and then start a bit low, watching the expansion at the pressure ring carefully as I work up to max.

Revisiting this as I bought a 22" Ruger Hawkeye.

This little round is a good one.