340 Weatherby Magnum Owners?
To my good friends in Alaska, the most beautiful State in the nation, greetings from Oregon.
I have been lurking on this forum for many years and have learned alot. Thanks. I posted this question, because I know there are more 340 owners here than any other forum.
I need your help and advice about bullet selection for the 340. I have done a substantial amount of load development (various powders, OALs, etc) on my 340 and still am not satisfied with the results. I’m I asking for too much to get MOA with this rifle?
The challenges, as you know, include:
(a) the twist rate is 1:10. According to Greenhill's caculations, this means bullet length of 1.633 – 1.985. Of course, there is nothing near that in .338 hunting bullets. The longest bullet available is 250gr. Barnes TSX at 1.5”. The 225gr TSX and the 275gr A-frame at 1.4”. Most others are 1.3’ or less.
(b) with the free bore, you are limited to magazine length for OAL ( I have been using 3.710”)
Here are my findings:
250gr Nosler Partition – 2.0-2.5” groups at 100 yards (not acceptable)
225gr Swift A-Frame – 1.5–2.0” at 100 yards (not acceptable)
New 225gr. Barnes MRX – 1.5” groups at 100 yards (not bad – not great)
250gr Barnes TSX – 1.5” groups at 100 yards (not bad – not great)
225gr Barnes TSX – sub-MOA groups (one at 0.630”) at 100 yards, HOWEVER, with only 3 or 4 rounds in a 5-shot group. There is always 1-2 flyers in every five shot group, 1-2” apart from the ragged holes above. I thought this was the one. 87.5 gr of IMR 7828ssc. But, I cannot get rid of the flyers. I have tried different powders, etc – flyers are gone but so is the accuracy. Shortening the OAL does not work. Cannot increase it because of the magazine.
Thinking about trying the 275gr. A-frame, but that is a very big bullet for elk. Probably OK for Moose. Anyone using this bullet?
What are you using? What kind of groups do you get? Is MOA possible?
Thanks in advance for your input!! OEH
problematic 340 WBY
Shades of deja vu!!! I had a rifle from a well known custom light weight rifle maker that did pretty much the same thing. I put over a 1000 rounds thru it utilizing different powders, primers, and bullets. I finally rebarreled it to a 300 Canadian (now called a 300 RUM) and have been satisfied ever since. Soooo, I would consider having a competent gunsmith evaluate your rifle with the thought that a new barrel might be the answer to your problem. Many 340 WBY's shoot well and I think an expectation of sub MOA accuracy is not unreasonable
Thou I am no fan of the 33's I have used them quite a bit. I always seem to wish I had my 375 when I am carrying them. Anyway I had 2 340's that where very, VERY accurate. The first was the first Lasermark I ever saw and had to have it. With factory 250 noslers it was a genuine 3/8" gun. I had a 3 shot group at 300 yards that was 5/8". Not shot by me. The other was a custom rifle with the reamer made to copy that Laser that never shot anything over a inch.
I would go thru the gun checking everything. Scope, mounts, trigger, bedding, barrel bedding, barrel crown, etc.... Flyers are usually ammo or bedding.
Scrub the bore until it is spotless. Not pretty clean but spotless.
I would then check everything in the loading process. I use Lee collet dies as they make nice straight cases easily. No dicking around afterwards. Then I would go with the 225 TSX and IMR 4831 or H4831sc. Use only Federal 215M primers. I have no idea why but I have seen a 1/2" WBY shoot 2" by going to the CCI-250.
Good luck. Hope your shoulder lasts thru the load development.