338-378 & Powders

David Long · #1 08-14-2009, 06:42 PM

Hey guys, I'm new to this. Am shooting a 338-378 with a 40" barrel, 1 in 8 twist. Using 300gr SMK (when I can get them). Wondering if anyone has any experience with Vihtavouri powder in this calibre & what results.

Marine sniper · #2 08-16-2009, 04:02 PM

Quote:

Originally Posted by David Long

Hey guys, I'm new to this. Am shooting a 338-378 with a 40" barrel, 1 in 8 twist. Using 300gr SMK (when I can get them). Wondering if anyone has any experience with Vihtavouri powder in this calibre & what results.

Why the 1/8 twist? Only need 1/10 for a 300SMK. Ever thought about trying H50BMG powder?

David Long · #3 08-16-2009, 04:54 PM

We used to use 1 in 10 with 30 Cal, but ended up chasing every deer we shot. Were using SMK 200 gr, & seemingly punching holes through them. Went to 1 in 8 & it made the 30 Cal into a deadly instant killer. Same happened with 338 Cal. Have been using H50BMG with this gun, but am finding burn rate changes with from one loading to another in same lot#. Having same problem with H1000 in a couple other guns. Hodgdon don't want to hear it. That's why asking about another powder. When I said I was new at this, I meant with the forum. Have been long range hunting 35 years. Have kills out to 1650yds. Several one shot to 1400yds. I thank you for the feedback.

Dave

PS: Marine myself from '58 thru '61

Joel Russo · #4 08-16-2009, 06:34 PM

If H50BMG is your powder for accuracy and velocity, why not buy the 8lb jugs and verify burn rate from jug to jug?
I shoot the .338-.408, and the .375-408 all year long, hundreds of rounds through each. Every time I move into a new jug of powder, I simply verify the burn rate. If it's off a bit, I adjust the load.
I do this whether it's Hodgdon powder or Vihtavouri.

RDM416 · #5 08-16-2009, 08:33 PM

David,

40" barrel? I can understand a barrel that long on a 50 BMG, but what is your reasoning for it in a 338 cal? You might check out Lilja's web site about barrel length. Dan used to have a article posted where he did a test with ultralong barrels and velocities. It has been a year or more since I read the article so I don't remember all the details, but I think he used a 338 cal, and started with a long barrel in the 38 to 40" range. He would get a velocity reading, cut off an inch and try again. I don't remember what the cutoff was but at some point on barrel length, he no longer got any gain with the longer barrel. I'll have to see if I can find that article again.....you have me curious now.

I will keep an eye on this thread as I am interested in VH N170 in the 338-378 (mine is actually a 338Kahn, but not much difference.) I am currently loading RL 25, but it so temperature sensitive that I have had to make a chart of velocity variations based on temperature. (Elk hunting in NM at 80 degrees, or whitetail hunting in Kansas at 12 degrees can cause velocity variations large enough to cause real problems) I have tried 50BMG in my Kahn, but could not get the velocities I get out of RL 25. N170 looks to be about halfway in between RL 25 and 50BMG on the burn rate chart, so I have been thinking about giving it a try.

If you work up a good load with VH powder, please post your results. I will do the same, but I already have my drop chart worked up out to 1100 yards and don't plan to make any changes until after this years hunting season is over.

yobuck · #6 08-16-2009, 08:55 PM

some of the guys around here are using wc872 in both the 338x378 and 338x416 imp.

David Long · #7 08-16-2009, 10:15 PM

Read Dans' article about barrel length, went with 40" to get 3000fps. Shoots great. Am using 8lb containers, but burn rate is changing from loading tom loading out of same container. Has changed while sitting in loaded cases. Using Oehler chronos, 33 & 35P hooked in series & keep careful track of velocities. Super shooter, but hate having to back off on load 2 or 3 times a year. Just wondering if anyone else having problems.

Thanks again, Dave