.270Wby Conversion to .270WSM


Jul 7, 2004
San Diego
Hi Folks,

I am new to the site. I have read some of your posts and realize that there is a lot of brain power and proven experience at this site.

I am not a proffesional long range hunter as some at this site are, but I do expect my rifles to be able to reach out and touch targets out to 500 yards. I say 500 because that is how far I estimated my shot at a WY 4x5 buck was last year with my .257Wby.

I am currently fooling around with my .270Wby Magnum which is giving me trouble. I can get only one load to give me relatively good accuracey. My load is 75gr. IMR7828, with a 150gr. Barnes "X" bullet. This gives me groups between .5 and .75 inch at 100 yards. However, it is a hot load and stretches the ring at the base of the magnum case so that it chambers with slight binding the next time I load it. This I beleive throws off the alignment in the chamber and reduces accuracey.
I have tried lighter powder charges, different powders, lighter bullets, but this rifles just says no. Accuracey suffers if I try something different.
So what I have been thinking of doing is to re-chamber and re-barrel the rifle for the .270WSM which does not have the stupid magnum rim at the base of the brass. My question to you gentelmen, is, can this be done? and how is it done.
I am not familiar with the rifle machining jargon. What does truing a rifle actually entail? If you machine the existing action you remove material which would only make things sloppier.
Do you then bore out the action and press in a sleeve of some sort and machine in a new tight, minimum dimension chamber that is perfectly aligned to the barrel?
Can someone please enlighten me on this procedure and tell me if it is possible to perform on a Weatherby Mark V action. And would I be much better off putting a new barrel on the rifle. The current barrel has appox. 250 rounds thru it.

And my final question, financialy speaking would I be much better off just buying a custom gun rather then trying to save the one I have. The reason I hate to part with it, is that it is in a beautiful Lasermark stock and I kind of hate to part with it.

Thanks in advance for any enlightenment.

Vic, out
I believe Chris may be able to help here.

I also believe that the existing barrel will not be much good once it's set back far enough to chamber for a 270 WSM.
Vic ,
Truing the action normally involves machining the faces of the action and barrel where they meet to be perfectly square and ensuring that the threads in the action and on the barrel are cut square . Normally the action is held in a special jig to do this . Some gunsmiths fit special collars on the bolt to ensure accurate alignment with the action .
It is usual to lap the locking lugs on the bolt at the same time so that they bear evenly in the locking lug recesses . This is particularly difficult with the Weatherby Mark V due to the fact it has 9 locking lugs vs the normal 2 or 3 . I'm told that in many cases only about 3 of 9 locking lugs bear evenly . Many gunsmiths wouldn't recommend the Weatherby action as one to use as the basis for a super accurate rifle for this reason .
On top of this I think that if you want ultimate accuracy you may need a better trigger which might be hard to find for a Weatherby .
I'm not saying Weatherbys can't be made to shoot well , just that it is more involved . I suggest that you first decide what level of accuracy you want and then talk to a few good gunsmiths to see whether it is achievable at a reasonable cost.
You might find it's cheaper to sell off your Lazermark , start from scratch and have something custom built using a different action .
I reload for a buddies 270Wby , he shoots the 140gr Nosler Ballistic Tip , the load is 73.5gr of H4831sc , fire formed brass that only has about 3/4 of the neck resized , bullet is seated .07 off the lands
He gets great accuracy and the velocity out of a 26" barrel is just over 3100fps , not smokin fast but it is very accurate.
at 500yds this combo is still holding over 1300lbs of energy , which should be all a mule deer can stand.

As far as rechambering to 270wsm , I believe that you'ld be better off just rebarreling to that chamber. OR rechambering to a wildcat in the 270 family that is bigger cased than the 270Wby
But first off , I'd rty having the barrel set back a bit and rechamber to the 270Wby again but have the throat cut so it doesen't have the "free bore" that Wby puts in their guns , this will help find an accurate load as you can seat the bullets out to closer to the lands.
The Belt on a magnum case is not a bad thing and it realy isin't a problem to reload for you just have to learn to work around it , buy only neck sizing your cases you make your case headspace off the shouler instead of the belt and by only neck sizing 3/4 of the neck this helps hold the case in perfect alignment with you chamber. Look at all the 1000yd BR shooters that are shooitng 300 Ackly and such , they have belted cases.
MY $.02 worth---sell your 270 wby and get a tikka t-3 light. You'll be carrying around a lot less weight, you'll have a new gun for about the same difference as what you might invest in your wby which will now be of very questionable resale value if you do the upgrade?? Just my idea.
Dear Aussie,

Thank you very much for describing the truing process for me. It helps me put the process in perspective. I also think its awesome to be be able to communicate with minds from around the globe.

Thank you for your input as well and many thanks for the .270Wby recipe. I am going to give it a try. As a matter of fact I should be reloading right now rather than on this site.

Thank you for your $.02 worth as well. I have been to the Tika site and looked at their rifles. They look nice and are reasonably priced. I noticed that the Sako's have 3 lugs on the bolt vs. 2 on the Tika, can anybody tell me if this has any kind of significance with regard to accuracey or is it just nice to have a smaller rotation when opening the bolt.
Another rifle that I was interested in is the Kimber. Does anybody have any experience with its accuracey?

Thanks for all your input guys,
Vic, out
Might try and buy a box of wby loaded ammo in different bullet weights and see how they shoot. If the factory shoots about what you think they should I forget what groups size wby test their rifles at may give them a call. May wind up with a bad barrel. I've only see one of the kimber and was in a 270wsm don't know what kind of relaods he had but wasn't that great of a shooter group about 1 1/2" for 3 shot. You got enought advise on most of your question. JDJONES75 gave you a good answer as to what and how he reloads for his buddies wby rifle what he is telling you "tailor your cases to your rifle" just what the BR guys do. Right now your reloading to a chamber(dies) that isn't your chamber but one that has to work for all rifles. I had neil jones make a set of his shoulder bumping dies up for my 30-378 since wilson doesn't make any cost alittle over $200. Once I fire that case my dies never touch the body just the neck and when sizing is need I can bump the shoulder back. Then once you get into alittle more you can get different bushing to handle neck tension big factor in getting small groups as with seating depth. With the wby brass being soft I'll ream the inside of the neck as keep the brass flow down. With all that type of reloading sometimes you just cann't get them to shoot at least for me I then know it's the rifle may be the barrel etc. Well good luck.
You can rechamber a 270 wby to a 270 wsm. You would have to set the barrel back since the wby case is longer than the wsm. Due to the fact that the wsm is fatter and bigger around, the wby chamber would then be cut away when cutting for the wsm chamber.

I am not sure of your exact situation, but the Barnes bullets might be the problem. I would first start trying diff. bullets. Banres may not be the most accurate....but accurate enough for hunting. You say that you are getting .5". What is your ideal group sze? We must remember that guns and people have their limitations. The wby can be accurate, it may be other factors. Like, bedding, trigger, the barrel, the action, etc. By rechambering you may not get what you are wanting. What if you rechamber and then it only gives you a .75" group? It is hard to know, but know when to draw the line. I would work with the wby and check the bedding, trigger, action, etc. Don't forget, some rifles shoot better not being free-floated. Some shoot better with some pressure applied to the barrel. After you have eliminated all of the possible reasons why it is not accurate as you want, go from there.

To answer your question, it is possible to rechamber to a wsm and is probably the least expensive option. Other things to look at are: is it a sporter weight barrel or bull barrel? Who is the maker? Is it a factory or custom barrel? I know that this can get in depth.

Hope I have been of help. Good Hunting!
I went ahead and updated the post by doing a new one. But my first thoughts were that you would NOT be better off rechambering your existing barrel, in fact, I think it would be more expensive. You can read the new post.

In terms of using the Barnes bullets, I have NO experience with their regular X, however, the new Triple Shock is amazingly accurate. I can group with that bullet just as well as the Nos. B-tip or A max. Try the triple shock in 140 if you want to stick with the Barnes.
I think you have a reloaing issue rather than needing a new barrel.The area right in front of the belt on the magnum cases never gets resized by factory dies.Most people tighten down there dies hoping to cure this and end up causing headspacing and case seperation issues.If you measure this area it is usually 0.002-0.003 bigger than it needs to be because the factory dies don't touch it.Many 1000 yard shooters myself included build a custom die that holds bushings that only reduces this one spot.The die doesn't have a top it is just a bushing holder and only works for this one area of the case-can't be used to do necks.Today they make a collet die that does the same thing for around $80 a huge savings. www.larrywillis.com
Is the web address for the die.The company is Innovative Technologies and many long range shooters are using them now rather than tossing the cases after 2-3 loadings.You can measure up a couple cases first to see if i'm pointing you in the right direction but your sticky bolt was a dead give away.
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