Mossberg 338 Win Mag Reloading Help

[Gary Murray]

I shoot a Mossberg 338 Win Mag and have just started reloading this year. My most accurate factory rounds for this gun were the 225gr Federal Power Shocks but they have since been discontinued. I tried a box of Fusions and they were the worst factory rounds i ever put through my rifle.
Anyhow, I need some help trying to put an accurate load together. I'm using IMR 4350 powder and went through a whole box of 225gr Nosler Partition bullets with zero consistency. I have a spring grizzly hunt coming up on the May long weekend and hope i have something put together by then. I always thought that because my gun originally liked 225gr with my discontinued Federals that the 225gr would always be the way to go but i am finding out now that this is not the case. The IMR 4350 powder is what i was told to get but i was also told that IMR 4831 would be better. I was also told to buy factory rounds for my grizzly hunt but then again i would have to buy a few boxes to find what my rifle likes and to those of us that shoot the 338 Win Mag, it is no cheap date. Any help would be appreciated.

Gary

 

[Kenny_G2]

I never had any luck with IMR in my 338. I went to Reloader 19 or 22, can't remember off hand, and I finally had some decent groups. For load development I always start working with the cheap Hornady and Sierras, which I would also have no problem using for hunting. Once I get a good combo I develop a load with the premium bullets (250gr Grand Slams for me) and the grouping is usually not far off.

 

[jeff270]

Re 22 and 250gr bullets worked pretty good for me.
If i still had a .338 I would try the 225gr TSX.

 

[elkhuntr]

Please define 0 consistency. If you are maintaining sub 2" groups, you are hunting with confidence out to 300 yards. So not sure what level of consistency you are looking for.

IMR 4350 or H4350 are great go to powders I have found. Yes, others are recommended and work well too. However, IMO, if you cant get I4350 to work something else may be astray. Consider the shooter in the equation as well

What we know is that your rifle has proven that 225 gr works. So you should be able to at the very least achieve factory ammo performance. There is a gazillion variables to consider. Be sure to work within two grains or so from max and use 0.5 grain intervals. You don't need to hod rod this round, it has more than enough to get the job done. I started with 67gr of I4350 and went up. Start load at 67gr and max shows at 72 gr on the Hodgdon site. I found a great accuracy node in a 22" barrel around 68gr or so. I read others finding success in the 70gr range. Your barrel will tell you its preference.

And verify your best bullet jump with the best load. You may find that factory OAL may not provide the best accuracy for your rifle. First, I would try the Noslers with about a 10-40 thou jump. X2 on KennyG2 advice on using cheaper pills. Save the boutique ones for the real deal if you wish, but those standard pills will get the job done too.

If you have access to a run out guage use it to identify where runout is happening. 4-6 thou should provide reasonable hunting accuracy. I found recently my new unfired win brass was very...repeat, very inconsistent. Once fire formed I could maintain sub 4 thou. But I did identify that my dies were imposing about 2 thou runout from the expander button. However, to better this I will need to neck turn the brass, that varied from 10 thou to 12.5 thou thickness variation.

Hope this helps in some way.

 

[mmattockx]

My Ruger 77 likes IMR4350 under 250gr bullets and RL-19 under 225gr bullets. Nosler Accubonds (225gr and 250gr) and Hornady SST's (225gr) and SP (250gr) have all shot acceptably for me, certainly more than good enough for hunting purposes.

Just my $0.02, but I wouldn't load anything lighter than a 250gr bullet for grizzlies. The Barnes 225gr TSX would probably work well, too, but I have yet to try any myself.


Mark