338-416 Rigby IMP

[358sta]

I'm new to this forum. I was directed here from another forum, where I posted these same questions but with no responses, by Jon A.

Looking for loading data for this wildcat. The project was finished 10-12 years back before the introduction of the WSM and RUM cartridges. I just recently got the rifle from the gunsmith (I moved before it was finished). I will be using 300 gr. Sierra MK bullets. I figured I might as well test it out before I have it rechambered for some other hotrod 338 cal cartridge.

I have the following slow powders in my inventory that I think might work for this combination -
H-1000
Retumbo
RL-25
N-170
AA-8700
H-50BMG
IMR-5010
WC-860
H-US869
WC-872

Any guideance would greatly be apprecaited along with any suggestions on a firefoming load.

Thanks.

 

[chris matthews]

go over to www.precisionlongrangehunter.com and post it there for Darryl Cassel....he has shot that round for years and has a bunch of info on it.

 

[358sta]

Was told Dave King has experience with this round and frequently posts on this forum. I have posted the exact same information above on the forum you suggested.

 

[wc872]

116.5 grs.WC872 has worked w/300gr SMK
112.5grs. of 24N41 or H50BMG w/300gr SMK
H1000 & RL25 worked quite well w/250gr Scenar/Lockbase
Ditto w/225gr. Accubond
Semper Fi

 

[Jody]

358sta, i was just wondering if you have worked up any loads for your 338-416? I to have just built a new gun in this caliber, i have talked to Darryl Cassel a little on this gun and load development. One question, were does the wc872 fall into the burn rate chart? Also have you done anything with US869 with the 300 grain? Thanks

 

[Black Diamond 408]

I have built lots of these hotrods, retumbo works very good with the 300MK, top loads around 99grns, start low and work up.

 

[358sta]

Jody, I had another gunsmith look over our rifles and found a slew of problems including a large amount of runout on the chambers. So, we decided to have both rifles rechambered for A-Square's 338 Excalibur cartridge. We also chose this cartridge over the 338-416 IMP because we didn't want to go through the hassle of forming brass. Ballistically, the Excalibur is very similar to the 338-416 IMP with the added bonus of having formed brass available. Granted, A-Square's brass for the Excalibur is twice the cost of Norma's 416 Rigby. Sorry, I won't have any information for you. I just received the reamer for the Excalibur and hope to be shooting in a few weeks. As to WC-872, my lot (have 6-8 lb. jugs) is within one grain of the new Hod. US869 powder, very slow. Hope this little bit of info helps in your load development.

KP