Weatherby 338-378 grouping issues

[valin]

Hey guys. I've been having a difficult time trying to figure out why I am getting such terrible grouping with my Weatherby Accumark 338-378. At 100 yards, the accuracy is all over the place, and i'm talking 8" at times. The scope I am running is a Leupold VX-3L 4.5-14x50. I am shooting from a solid table, with the gun in a fairly heavily weighted down rest. I was grouping very well with my old Weatherby 300 mag in the same rest. Do you guys have any ideas for me? Whitetail season is fast approaching, and I'm running out of ideas.


Here is the load specs:

20 brand new brass, and 20 once fired brass
180 grain Nosler Accubond Spitzers
110.0 grains of IMR-7828
Federal matched 215 primers
3.763" total length

I wanted to eliminate as much as I could, so I picked up a new box of 180gr bullets, a new tin of 7828, and a new box of matched primers. I yanked the stock off the rifle to ensure there was no barrel floating issues, and everything is perfect, as I expected it to be.

 

[GNERGY]

I had problems with the 250 gr. Noslers in my 338 Ultra mag, then I tried the Barnes 225 TTSX and put 3 shots at 300yds into 5/8ths of an inch. I did get the 180's to shoot OK.
Load the Barnes .050 off the lands and do your testing at distances of 200 to 300 yds.
Good Luck
Tarey

 

[Tikkamike]

I have a couple ideas. for 1 an 8 inch group at 100 is unacceptable. that is a direct indication to me that something is loose. take the scope off and the rings `make sure the bases are tight. Also make sure none of the screws for your bases are not too long and bottomed out. once everything is tight lap the rings set your scope in there and shoot it again. if that doesnt fix it I would swap the scope with another to see if you get the same group if not you probably have a broken scope. Lastly my dad had accuracy issues with his accumark 338-378 (1.25-1.5" groups) he switched to Barnes Tripple shocks which are a good match to a freebore rifle like yours because they are not meant to be seated close to the lands.
Can I ask why you are shooting 180's out of a 338-378? that is way too light for that gun. Take advantage of that big powder can and shoot a minumum of a 225. 180 is suited for something like a 30-06.

 

[Autorotate]

At 100 yards, the accuracy is all over the place, and i'm talking 8" at times.

If I saw this type of target, I'd look really hard (Dr. Rifle slow and thorough like) at the following-

Optic-Do you have another rifle you can put the optic on, and just shoot a group with to make sure you didn't shake a the guts loose on the VX3.

Optic mounting-Obvious visual inspection, then remove optic, remove rings, remove bases. Reassemble using a product like the Kokopelli alignment bars to ensure a stress free mount for your optic. If you don't have alignment bars, attempt to slowly and gently rotate your scope in the rings with the ring caps removed, exercising care not to mar your tube. If your scope acts bound up, that should serve as an indication that your optic mounting is putting stress in your optic. Reassemble and torque to mfg specs.

Action screws-check to ensure you have those torqued to 55-65 in lbs. Most smiths will suggest the front screw needs to be torqued to final torque first, then the rear action screw.

Barrel free float-you stated it is free floated, but most Wbys will have pressure point near the forend, used to establish a poor mans barrel tuner if you will. Either this pressure needs to be consistent from shot to shot, or free floated altogether.

Bullet weights-Try a three shot group with starting loads at 180, 210, 225, and 250 grain weights (or those you are interested in). Your barrel may like a certain bullet weight/velocity range vs. others....no need beating your head/wallet against the wall, let the rifle tell you what it wants to shoot first, then fine tune.

Use a vice/brace/led sled type dvice to get the big precision/accuracy issues sorted out. That's a boomer, and it won't be fun while you sort this out. Rule yourself out as a variable until you get it calmed down, then go back to your proven shooting methods for fine tuning.

 

[valin]

I really do appreciate the input guys. I went back out shooting today, with a buddy of mine who runs the same rifle. I swapped out scopes, and ended up with the same result......still all over the place. We then fired my loads in his 338-378 and ended up with the same results, so therefore, the issue is in the loads. We also fired some 200gr. nosler accubonds on 104 gr. of IMR 7828, and the results were substantially better, but still not great by any means.

I have been doing some more research on this site on load data for my rifle, and am going to take all of your advice, and step up into a heavier bullet. I am going to order some Barnes Tipped TSX 225's. I would really appreciate it if you could recommend me some loads for these bullets. Is the IMR 7828 a good powder for this, or should I be switching?

I will be using Federal 215 matched primers.

 

[Gnome!]

Don't know if this will be of much help
.338-378 @ www.reloadersnest.com

338-378 Wby Load Data - Handloads.Com

LoadData - .338-378 Weatherby Magnum (Barnes Reloading Manual #3)

 

[bb204]

Is this the first load that you have tried ? How did you come up with this load ?

 

[valin]

This is a load that I had found in the nosler loading manual, and I have also seen it posted online previously. It is the first load that I was attemping to run, since this rifle is new to me.

 

[340Shooter]

I would also try some 250gr bullets. Some rifles like heavier weights.

 

[Gnome!]

Unlike you Valin I'm having no problems getting 3/4 - 1 groups at 100 and 1.5 inch groups at 200 using the factory 250G partitions as that is all one can purchase here in OZ

So I am looking forward to reloading my own with Hornady 225gn SST's once my press arrives. I have also been given 50 Hornady 250gn Interlock round nose to try as well

As for what charges I will be using I have yet to decide, but am leaning towards 90gn AR2209 or possibly 112gn AR2225 for the 225gn SST and 108gn AR2225 for the 250's

 

[Tightline2001]

i would try Retumbo, H1000 or H50BMG. all of these powders shot great in my .30-378 accumark. I was using the 210 bergers. I know yours is a 338-378 but i tried 7828 in mine and it did not like that powder at all. Just a suggestion

 

[valin]

Thanks for the input guys.

I will pick up some H1000, and play with that with the 225 TTSX's. On the Nosler site, they recommend the low at 107 gr. and the max of 111 gr. with a 225gr bullet.


Have any of you guys played with 225 TTSX's?, and what loads did you end up with for accuracy?

How are the TTSX's on a smaller animal like a whitetail?

 

[valin]

I was unable to get the TTSX's, so I picked up some 250gr. Speer Grand slams instead, since most of you guys recommend 250-300gr. I also picked up some H1000 powder, and am going to do some loading this weekend.

Any recommend loads?

 

[athompson4]

I shoot a .300 weatherby and my dad swore that it would not shoot right when he was trying to use it. So I started reloading for it and discovered that the biggest difference in grouping and consistency came from the kind of powder used. Try powders with different burn rates and different grain lengths. When testing the powder always use the same bullet for each set. I have tried 165 and 200 grain noslers in my .300 and what works for the 165's did not necessarily work for the 200 grains.