338-378 & Powders

[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.

 

[Marine sniper]

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]

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]

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]

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]

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

 

[David Long]

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

 

[Long Time Long Ranger]

David, I have seven 338-378's right now. Have been shooting this round since the 70's. Great cartridge for long range anything. H-870 has always shot best for me through the years with best velocity and lowest extreme spreads. Just varies a bit batch to batch so I order quite a bit at a time same lot number. Since Retumbo came out I have been working with it and getting very good results. Have never tried vito powders. In the 28" 1-10 Hart barrel I was shooting this evening I was pushing the 300's at 3050 fps, the 250's at 3325 fps and the 200's at 3615 fps. I have quite a bit of data on this round. All of mine are 28-30" barrels and the 300's all run between 3000 and 3100 fps depending on the rifle.

 

[Joel Russo]

Am using 8lb containers, but burn rate is changing from loading tom loading out of same container. Has changed while sitting in loaded cases.

If you're "burn rate" is changing from shot to shot out of the same jug, I doubt it is the powder.
Did this just start happening?
If you're intent on using VV, then don't overlook 24N41. I use it in my .30-.416 Rigby Improved with excellent results shooting the 240 gr and 250 gr SMK.

 

[J E Custom]

The H50 BMG and the H869 are both extreme powders and should be very consistent
in the 338/378.

Like joel Your problems may be some where else. I use a lot of these two powders and
get very consistent SDs and velocities.

J E CUSTOM

 

[bigdawg1592]

This post was originally started by my Father, and l'm not sure you guys are quite understanding what he is saying. When we are loading with the Hogdgon powder, we are finding consistent velocities. However, the problem we are running into is this; lf we load 20 rounds and shoot 10 of them, the velocities are consistent. When we shoot the other 10 rounds at a later date, the velocities are consistent, but have increased by as much as 100 fps overall averages. This seems to be a problem with the guys in our area that are using hg powder, which is why he inquired about different powders. And we use 2 chronos connected in series, so are confident in our numbers.

l would like to say that l have been in a few other forums, and you guys seem to at least be knowledgable and worth talking to. Thanks for the intelligent replies.

Vince

 

[Long Time Long Ranger]

Bigdawg,

The loads I was reffering to that I shot yesterday with the 200 grain noslers were loaded 10 years ago with my pet load of H-870. Ten years ago they averaged 3615 fps. Yesterday they averaged 3615 fps. So that is not a problem with the H-870.

 

[Joel Russo]

We need more information to help solve the problem. When there is a fluctuation in velocity, is it up or down? What is the ES between shots between different days? Are you using cheap digital scales or old balance beam? Are you using a lube in the neck that is causing a chemical reaction? How are you storing the "other" rounds that are varying in velocity? Are you cleaning the barrel between different shooting sessions?

Do you have any fouling at the end of the barrel? The 40" barrel is excessive for this case, and you may be experiencing "slow down".

Are you're chronographs in 100% working condition and are they at the same distance from the muzzle every time?

I doubt that the problem is with the powder, since you stated that you had the same problem with H-1000 in other guns.

My guess is that the problem lies somewhere in your scales, powder storage, chronograph or primers...

 

[David Long]

Hi Joel,
Thanks to all for the input. Let me say, I'm a real nut about this stuff. Consistent velocity, 8 to 12fps in 10 shots. Chrono always set up the same distance. Using the new RCBS Chargemaster scales. I'm quite involved with these biug guns as I build stocks & do all the bedding. Every gun we are using & there are 10 of us, is shooting 1/4 moa or better. Like I said, we have good chronos & I am only having this problem with 4 guns all of which is using H50BMG or H1000. Was shooting 30-378 'til 2 yrs ago. Not only does the chrono show increase in velocity, but cases show signs of sticking & pressure. Am running 2990fps and not wanting to work with max loads as I just don't need all that energy. Once I get velocity at 2990fps, the gun is super accurate. Any ideas you may have will be appreciated. No copper fouling. Gun don't go more than 15 rds without cleanup. Have been in this game for 35 years. Just got a new 8lb cannister of H50BMG for the newest gun I built this year. Can't really try it 'til I find some 300grSMK. I know burn rate changes from lot to lot, but never had this problem 'til about 2 yrs ago with Hodgden. By the way, powder stoted in controlled conditions, as well as Fed Match Primers. Both chronos, which are hooked up in series are reading 7fps difference and always show the increase.