I recently bought a 338-378 Weatherby Accumark. I am using 225grn accubonds, H1000, and Fed 215 primers. Started with 109grns of powder to get on paper. Shot three different groups, with three different loads trying to find one that shot better than the others. Starting load @ 107grns, then 109grns, then 111grns. Never got better than a 3" group. The rifle was bought used. My buddy thinks that it could just be copper fouling, and a good cleaning might do the trick. I was thinking about trying 250grn accubonds. Would copper fouling make it shoot that bad?????

Sorta depends on how bad the fouling is.

Most of such bad accuracy is a poor choice of bullet, try something else.

Cary, it could be several things.
Yes, I've see barrel with enough copper fouling that the owners thought they would have to rebarrel the gun.

I would start with scrubbing out the copper, and making sure everything s tight.

Some component combinations don't play well with each other. I've had experiences in the past where FED 215's with stick powers would print 3" groups. With H1000 and Accoubonds, I'd try Winchester Mag Primers, and work up in 1gr increments.

I bought 2 different brands of copper solvent and plan on doing some major cleaning when I get off work this evening. I guess I have just been very lucky up to now. I have never had any problems like this. I sure it hope does the trick. If this doesnt work I'll try different primers.

Hey Cary,

Yes, copper fouling can make things pretty bad. If you have a copper solvent that has worked well for you give it a good cleaning. I use Bore Tech Eliminator and it removes copper like nothing I've ever seen. I shoot Barnes bullets so a good copper solvent was a must.

One of the other things these boomers do is loosen up screws like you wouldn't believe. Make sure your action screws are snug (don't over tighten) as well as your scope mounts and rings.

Several people I know that shoot 250 grain bullets swear by the Partitions and RL 25. I've seen loads for US869 and 250 grain bullets so that could be a possibility as well but I use that for the heavier bullets like the Barnes 265 grain LRX. Seating depth can make a significant difference with this chambering because of the long freebore. I've seated them as long as they could be and still fit and function in the mag box. The most accurate loads I've come up with were actually seated pretty deep while running a pretty stout load (Weatherby chamberings seem to like it hot). I seated the 265 grain bullets to the same OAL as the 225 grain bullets and they shoot about 3/4 inch at 100 while shooting about 1 1/4 at 200 (assuming I'm shooting for sh-t that day). I want to note though, while it's not a lead sled I shoot from a bench rig so these numbers are not off hand or anything. The reason I say that is a friend of mine had similar issues and found that the rig he was using just changed the harmonics (or whatever) enough that his rifle didn't like it. From a front rest type of rig his groups shrank significantly.

All of that said, start with a really good cleaning and make sure everything is tight. Remember, there can be many different reasons groups are not as tight as you might like.

Ken....

Use JB bore paste and clean out the barrel.

If it shoots crummy afterwards, welcome to Silly Safari Season!

You are going to be running around chasing the root cause of something that may or may not be fixable.

You could have poor bedding, a poor scope, misaligned rings, or a bad barrel.

You won’t know till you get there.

Among other things check bedding, barrel channel ring and mount screws. What scope do have on it. Have some on else shoot it.

What type of rest are you using ect ect

I han a rem 700 300wm that wouldn't shoot under 8 inchs it had so much forend pressue on it that one could see the barrel move upwards when you tighten the action screws.

After bedding and free floating the barrel channel its a .750 rifle now.

I am using Talley one piece base/ring and a Swarovski Z5 scope. The rest is a Cabelas wannabe lead sled. I had a buddy try it and his groups were just as bad as mine. He has the same rifle and the same loads and shot under 1" the same morning with his.

Cary,
That is exactly how my 378 Weatherby shot until I had the bedding checked. It had been bedded with a marine fiber bedding material but there was pressure on the front receiver screw. Once it was re-bedded to eliminate the pressure on the front screw, the groups immediately came down under an inch. The groups had been 2-3" no matter what load I tried.

Ed, what exactly do you mean by eliminating pressure on the front screw? I dont know a lot about how bedding affects accuracy. I just know that I always hear people say that the recoil lug needs to have good solid bedding.

The gunsmith put a dial gauge device on the stock and an indicator on the barrel. When he loosened the the front receiver screw, the dial indicator jumped about .030". He bedded the action and the dial moved only .002" when he loosened the front screw. The groups immediately went to 1" or less---same loads I had shot before.

Weatherby also has a recommended process to tighten the receiver screws using a torque wrench. I have never tried it but a friend says it works.

This is why I love this forum!!! Great people, more than willing to offer advice to someone they have never met, because they share the same interest, and know how it feels because they have been there before!!!!

quote:

Originally posted by Ed Scarboro:
Weatherby also has a recommended process to tighten the receiver screws using a torque wrench. I have never tried it but a friend says it works.

Ed brings up a good point about the Accumarks as well as the Fibermarks (both have aluminum bedding blocks). Here's the info I've seen posted:

Tighten the rear trigger guard screw first to 30 inch pounds.
Align the Barrel to the center of the barrel channel in the fore stock.
Tighten the front trigger guard screw to 30 inch pounds.
Tighten the rear screw to 50-55 inch pounds.
Finally, tighten the front trigger guard screw to 50 -55 inch pounds.
Applying this method, using a torque screwdriver of the proper size, will insure the proper fit between the receiver, and custom aluminum bedding block, as well as the proper positioning of the barrel in the barrel channel.

Hopefully that will help you out. Remember though that your rifle just might not like that load.

Ken....

Heat---That sounds like what my friend was trying to explain to me. He is a collector of Weatherbys and has a passion for the 270Wby. At last count, he owned 7 of them. I didn't feel so bad after that since I own 4 in 30-378 (3 Accumarks and 1 synthetic).

Hey Ed, I can't say I collect things in general and I don't own more then one in any chambering but I do like Weatherby rifles. One 338-378 Accumark, one 340 Alaskan and one Vanguard Stainless Sporter in 257. The only other rifle I own is a Ruger 77 Mk II in '06. I am considering dropping the Alaskan into a Euromark stock for that silver and wood look and might get a new barrel in 300 Wby as I don't own a 30 cal magnum.

Ken....

This collector had a complete set of German left hand Weatherby's. He just seems to add to the 270Wby collection but none of the others. I think I own 10 Weatherby rifles right now including the 338-378, 378 and 416. I use the 257 for deer and the 30-378 for plains game in Africa. I used my 338-378 for brown bear in alaska.

Well I cleaned the barrel for 10 hours over 3 days and finally got the barrel clean. Went and shot it again yesterday and it has not improved at all. I talked to a buddy that says I need to have it bore scoped and check for heat cracks. He said that particular caliber is bad about getting heat cracks. Gonna try and get that done this week one day.

Years ago I read an article talking about how the 30-378 Weatherby would erode the throat after only 75 rounds and then more damage after only 125-150 rounds, etc, etc. I have a 30-378 that at the time I had over 300 rounds thru it and it would still group 1.25" at 200yds give or take depending on weather (or shooter). That rifle today has over 500 rounds thru it and it still shoots the same as it did at only 100rds. My regular load in it is 101gr of RL22 with 180gr Swift A Frames.

I think I would be more interested in getting the bedding checked and changing bullet/powder combinations. If the gunsmith has a borescope he probably has a torque screwdriver to try the correct tension on the action screws. My 338-378 did not like h1000 but shot RL25 very well. With the freebore, it did not seem to be very picky with the OAL. Good Luck.

I Have decided to say the heck with it!!! I am listing it on the classifieds. Will accept a reasonable offer.

It's unfortunate that you're giving up so easily. H1000 is a good powder for the heavier bullets and it wouldn't suprise me if your rifle just doesn't like that combination. Just curious, have you tried factory ammo?

Ken....

You give up too easy!
I tried H1000 in a couple other calibers and have NOT reloaded for this one, BUT... I had better groups from Retumbo in one rifle and RL25 in another. You may also try the Sierra 250gr Gameking first finding the powder this rifle seems to like then switch bullets around. Changing only one thing at a time.

Before dumping it I'd look at the crown and bedding. Either one can cause weird issues. Nate