338-378 range report

[el matador]

Finally got some nice weather around here so I took the big Weatherby out to test some stuff. I have been shooting uncoated 250 grain Accubonds with 107.0 grains H1000. This load shoots .5 to .6 MOA and scoots along at 2975 fps.

My first test was with some HBN coated 250 grain Accubonds. Using my 107.0 H1000 load at 3.800" I fired 5 shots over the Magnetospeed V3: 3057, 3058, 3065, 3065, 3063. This is a good 80 fps faster than the same load without HBN, and my ES for the 5 shots was 8 fps. After a couple of sighters to work the HBN into the barrel I fired the last 3 rounds into a group of 3/4 MOA. Pretty good since the velocity was well above my previous accuracy node. I'll have to fine tune this load since my gun likes the Accubonds and recoil is much softer than with the 300s.

Next I tested out some loads with the 300 Berger Hybrid and RL33. I started at 110 grains and worked up to 118 with no pressure signs. Groups were fired at 110, 112, 114, and 116 grains, but accuracy was poor. I shot 1 round at 117 and 1 at 118 grains to check for pressure, and these 2 shots went into 3/4 MOA with almost no vertical. All loads were HBN coated and loaded to 3.900". The exciting part was the velocity I'm getting from a bone-stock Accumark with a 26" barrel:

116.0 grains: 2913, 2908, 2917. ES of 9 fps, but accuracy was poor so no big deal.
117.0 grains: 2965 fps
118.0 grains: 2991 fps

I'm looking forward to another range session where I'll focus more around the 117-118 grain range and see what my groups and ES look like.

I picked up a box of 285 grain ELD Match bullets this week to try out. Hopefully I can find a 1/2 MOA load with one of the big bullets at 2950+ fps. After today I'm very optimistic.

 

[ctw]

I also own a .338-378,and look forward to your continued load development. I have'nt done any with mine as of yet. This summer I want to try nos. 225 gr. accubonds with rl. 26.

 

[Deleted member 46119]

Weatherby's have always seem to have a preferenct for Nosler bullets.

I tried to get my 338-378 to shoot 300g OTM. Giving up.

Gonna try Hornady ELD-M next.

After that gonna give up and reassemble as a 460 Weatherby.

 

[hemiford]

I'm building a custom 338-378. I have a strong suspicion that most of the
problems folks have with accuracy on these is due to the factory barrel.
It's just not stout enough. Nor long enough, but that's a separate issue.

 

[el matador]

I had no trouble finding a good load with the 250 grain Accubonds. I've noticed this rifle either likes a load or it hates it. I get 2 or 2.5 MOA groups until I find the node and then it tightens right up. I'm hoping the same will happen with the 300 grain Hybrids, and that the accuracy node will be around 2975 fps. I wonder if the reason people haven't had good luck with this bullet is because they can't reach that velocity with the usual powders. 2850-2900 is about max with Retumbo or H1000. There has got to be another node at lower velocity but that wouldn't be as much fun.

The factory barrels are a bit skinny for such a big cartridge. Mine has performed really well with the right loads though.

JF, don't give me any ideas. I'm fond of all the 378-based cartridges and a .460 would be a lot of fun!

CTW, good luck with the 225 ABs. Let us know how they shoot with RL26.

 

[Scratch]

el matador

What primer have you found best for the RL-33 powder in your testing?

Thank

Scratch

 

[el matador]

Scratch, I've only tried the Federal 215. Would prefer the 215M but they're still scarce. They're a nice hot primer which seems to work well in the big 378 case.

 

[Deleted member 46119]

Scratch, I've only tried the Federal 215. Would prefer the 215M but they're still scarce. They're a nice hot primer which seems to work well in the big 378 case.

I'm using CCI. 215s or 215Ms are just not showing up anywhere I can get them. Not online at all.

 

[Wedgy]

Your HBN results seem to be opposite from the norm; the same bullets with the same charge should drop in velocity, not increase because the HBN decreases the friction which lowers pressure = lower velocity.( it was 250 Accubond with 107.0 before & after coating right ?) In my Edge and RUM I had to add about a half a grain to get back to the speed I was at before I started coating bullets. Most people lose about 40-50 fps, it's pretty well expected so your case is interesting. Did you coat the barrel as well ?
Wow, 118 grain, that 378 case holds a lot of powder ! It's got my attention, thanks for the report and keep us posted.

 

[el matador]

Wedgy, most of the stuff I've read indicates that velocity should stay the same or decrease when using HBN. I wasn't expecting an extra 85 fps but that's what the chrono said. The exact same load with bare bullets was 2975, and coated was 3060. I don't know if the long Weatherby freebore has anything to do with it? This load is several grains below max in my gun, so maybe it has to do with the lower pressure. I really have no idea. Hodgdon, Hornady, and Nosler data all say the max velocity with this bullet is 2990-3000 fps with H1000. I'm loading .100-.140" longer than their OAL, and I tested up to 109 grains without ever seeing pressure signs. 107 grains is really easy on brass and accuracy is .5-.7 MOA.

With regard to barrel coating, I did not do it before going to the range. I had previously coated it by removing all copper and swabbing with alcohol/HBN. I then shot a few groups with the coated Berger 300s (about 10 shots). Since I had an elk hunt coming up I went to the range with my non-coated 250 Accubonds to make sure the rifle was zeroed. It took 3 shots before the rifle settled back in with the non-coated bullets. In total I fired about 12 shots with the naked Accubonds. After my hunt I returned to the range with my coated bullets without cleaning or re-coating the bore. I fired one HBN coated Accubond as a fouler, and then chronographed the next 5 shots (speeds are in my original post). The last 3 I fired for a group which went into 3/4 MOA: 2 bullets in the same hole and one "flier" at 200 yards.

I don't remember my exact ES before coating the bullets but it wasn't bad. Probably in the 15-20 fps range.

That RL33 is a fairly dense powder. 118 grains is a compressed load but there's no way I could fit that much H1000 in there.

 

[Laelkhunter]

Do you have a muzzle brake on it ? I love my .340 Wby, but I love it even more with a brake.

 

[el matador]

Yeah, this gun wears a brake. Recoil isn't bad at all with the 250s...and manageable with the 300s.

 

[Scratch]

jfseaman

Brownells has CCI 250 primers in stock as of this morning.

Scratch

 

[Deleted member 46119]

jfseaman

Brownells has CCI 250 primers in stock as of this morning.

Scratch

Yeah, got plenty. Want 215Ms. Some loads are not working with CCI.