Author Topic: Rebarreling a .270 to .240W (Read 897 times)

AnthonyW · « **on:** December 20, 2004, 02:40:56 PM »

He everyone this is a cool site and my first time here. My thought is rebarreling my M77 270 ultralight tangsafty to a 240 weatherby. I heard this is an easy swap because the head spacing is the same. If so Which barrel manufactorer should I go with. Thanks for any replies.

gunnut69 · « **Reply #1 on:** December 20, 2004, 07:15:16 PM »

The 270 is a standard case head cartridge and the Weatherby round is belted. They do not headspace even similarly.. The 6mm-06 is the near ballistic twin of the 240W and it is simply the 30-06 necked to 6mm. In it's normal configuration the headspace guages may well be the same as they are for the 270 and the 30-06. This is a wildcat but a very bidable one and brass is easily for from 270 or 30-06 (270 would be easiest). The Weatherby is a factory round but brass is incredibly expensive and I've found it to not last as well as commercial brass made in the USA. The guys around here have been using the 6mm-06 as a long range coyote shooter. They use Spit BT hollow points in the mid weight range for the bore(around 70-85 grains), long barrels and high power scopes to take out coyotes at ranges I won't even quote. Although some have been checked by rangefinder... Don't expect long barrel life but as a hunting rifle it should be great..

victorcharlie · « **Reply #2 on:** December 21, 2004, 12:27:41 PM »

Good to hear some talk of the 6mm 06. One of my buddies has one and I think it's an incredible rifle. I'm thinking his has a 1 in 12 twist 32" Heavy bull barrel and one of the old Urnerlt scopes. Talks about a long range shooter! I've been thinking of having one built for years, and this is probably my favorite wildcat. I don't hear of many people using it.....I wonder why?

Judson · « **Reply #3 on:** December 21, 2004, 03:30:26 PM »

I have yo agree with Gunnut69 here!!! I am rather sure that the 6mm/06 is actually a bit hotter then the .240 Weatherby, you might also look into the 6mm/284, you will hear some rumors about feeding problems with the rebated rim but I have built several and it is no problem. I have also done three of the 6mm /06, one on a Ruger 77 and two on Mauser 98 actions all it requires is a new barrel, but while you are at it lap the lugs, square the action and all that good stuff.
On the other hand if you really want a .240 Weatherby you will find the head diameter is .473 just like your .270 so again we are talking a new barrel and no machine work to the bolt face but performance wise I would go with a 6mm/06 or the 6mm/284.

gunnut69 · « **Reply #4 on:** December 21, 2004, 06:22:42 PM »

JUDSON- how does the case capacity of the 284 case compare with the 30-06 when necked to 6mm. I kinda remember winchester sort of implying the 284 as a short action 270. It didn't work that way but the short case in a standard length magazine should give a bit more leaway in bullet seating depths. How hard is it to get hold of 284 brass? The guys that have the 6mm-06s around here really like them for coyotes. They tend to be a little destructive for whitetails but it most likely was just poor bullet selection...

Greybeard · « **Reply #5 on:** December 22, 2004, 12:11:44 AM »

Don't see how the 6-06 could be hotter than the .240 Whby. Case capacity is identical. Only way one will do more than the other is if you up the pressure cuz the case sure isn't gonna hold more. Same can be said for the 6-284 really. Fill them all with water and they should be within a grain or two at most of same. Any difference with be caused by thickness or brass in the particular brand of case not due to size of case. All three use same loading data.

gunnut69 · « **Reply #6 on:** December 22, 2004, 10:35:50 AM »

I've not loaded for the 240 but have a bit of experience with the 6mm-06. The 6mm-284 should also be the same as the 6mm-06 as originally the idea for the 284 was to duplicate 270 ballistics in a short action. Enough case capacity was lost by having to deep seat the bullets that evidently the round didn't catch on. Perhaps it was just a bit too different. The only round in the 6mm caliber that is significantly faster is the 244 APEX. Based on a full size belted mag case necked down it is not very efficient. An associate built one on a Ruger action I believe and reported that it was too much. Only the slowest powders were usable and even then with a 26 inch barrel the flash was amazing. Still velocities were also amazing and barrel life comensurately short but still it did what he wanted. In all reality I've found the 243/244's sufficient for anything reasonably asked of this bore size. The 6mm-06 does make a formidable coyote round for extreme range shooting though.. I've a 6mm Remington in a Ruger No.1 that I've been toying with boring to a 6mm-06 or a 240 Gibbs. I bought a reamer for the Gibbs wildcat a few years back and am still wondering if it is worth the trouble. The shoulder is farther farward which means fireforming the cases.. If a suitable set of dies could be located reasonably perhaps this may be a cheap conversion. It surely is not a common round!

Judson · « **Reply #7 on:** December 22, 2004, 12:45:57 PM »

You do realise here that we are debating just a few hundred feet per second? Case capacity of the .240 is 63.08 grains of water, for the 6mm/06 it is 64.82 and the 6/284 68.33 grains. Also with the 6/284 you can seat the bullets out further so you waste no case capacity. One other thing about case capacity is that when measured the case is filled to the top of the neck, why I do not know for this area is never used other then for the bullet. The neck on the Weatherby is much longer then that of the 6mm/06, .308 compared to .240 on the 06 wildcat.
As for the .240 Gibbs, it will involve fire forming and all that good stuff. I do have loading info for it but the gains over the cartridges are minimal but it is different and hotter. I also have a set of dies I would be more then willing to part with. I took a .240 in trade a year ago and the customer who ended up with it had me set the barrel back and chamber it for the 6/284.

AnthonyW · « **Reply #8 on:** December 23, 2004, 03:09:37 PM »

Dang this has turned into one hell of a debate now. The thing is I do not want to fire-form cases anymore because I have a 243 RCBS improved sako, and that little sucker has very high velocity. So I thought I'd rebarrel the old 270 to something that was compareable but different then what I have. Ammo cost doesnt matter beacause I wont shoot it more than 60 times a year. The gun will mostly be used for coyote hunting. I also get ammo at wholesale through my archeryshop. Let me hear some more opinions on the 240W. Thanks