338-378 Loads and Accuracy Tips

[normo]

I'm looking to help a buddy solve some accuracy issue's with his 338-378, it's a Wthby Mark IV.
He has done some handloading for it, and is getting 2-3 good shots followed by a flier or two.
Does anyone have some good pet loads for this caliber/rifle combo? Since the plan is to begin again somewhat from scratch, where not limiting ourselves on bullet makes or weight.
Additionaly what type of accuracy work would you suggest to the gun itself to help it shoot better?
Being a Wthrby I figure it will shoot great once we get a load worked out.
Thanks.

 

[Richracer1]

Please tell us what has been done to the rifle and what powders, bullets, primers that have been tried.

Personnally, I would try the following combos:
250 AccuBond using either US 869, Retumbo, Supreme 780, Hybrid 100V, IMR 7828SSC, H1000 and a large rifle magnum primer
(recommend Fed. GM215M)

 

[JD338]

Member OU812 may be able to shed some light on this for you.

JD338

 

[normo]

Rifle is stock, has a brake on it, and maybe a trigger job.

Not sure what he and his dad are loading for it currently. But again, were willing to work from zero and go from there.

We'll have to give the above load a try, and work from it.

 

[Richracer1]

The list of powders I suggested, came from Nosler's #6 and Hodgdon's reloading data base.

 

[Antelope_Sniper]

I would say Rich is dead on. I would start with IMR 7828SSC, H1000, they have a reputation for accuracy in the big boy rounds, and are more likely then some of the others to be sitting on your shelf. If you wanted to try something new, 869 would be high on my list as well.

 

[GB300wm]

Make sure the rifle is cleaned with a good bore cleaner and fouled with 10 to 12 shots before making any determinations. Also make sure to wait 5 minutes between rounds to let the barrel cool and three shot groups are fine as 4 or 5 shot groups may make you flinch. The 338-378 is very powerful and will make even the best of us flinch with repeated exposure to firing this gun. A chronograph will also help in determining a load and checking extreme spreads. Look for a load that groups well with extreme spreads as low as you can get them. :grin:

 

[JD338]

OU812 had some issues with his Accumark 338-378 Wby. As I recall, the chamber was not concentric with the bore.

Waiting for OU812 to jump in here and give you his experience.

JD338

 

[normo]

I was thinking he might be shooting groups to quickly and heating it up a little, so we'll make sure we shoot nice a slow.

Hopefully it's nothing like a miss-aligned chamber and bore. For sure it will get a good cleaning before heading to the range.

 

[DrMike]

What you describe sounds like an issue related to a pressure point on the barrel channel at some point, so that as the barrel heats up it creates a pressure that moves the barrel slightly. I should think that the advice to make certain to give time between shots is sound. Also, the cleaning won't hurt, and the time invested in cleaning will permit cooling.

I would imagine that misalignment would not necessarily result in inconsistencies such as you describe.

 

[OU812]

Sent you a PM.