338 lapua large shank rechamber to 3338rum small shank

[junkout]

Like the title states..... I'm asking can it be done? Take a factory 338 lapua large shank barrel turn it down to thread to a small shank action and still have room to set it back and rechamber it to 338rum small shank.

[sharpshooter]

Bad idea......

[scope eye]

I don't think it can be done 338 Lapua is a lot bigger diameter than a 338 edge, so you would have to lop off 3" and start fresh. And then you would be in where the barrel starts to taper.

Dean

[junkout]

Sharpshooter please elaborate......... With facts as to why it's a bad idea.

[junkout]

Scope eye. If my figures are accurate......
The lapua case is shorter than the RUM by 0.126"
The lapua is only 0.019" wider at the case before the shoulder and only 0.006" bigger at the base.
I don't think cutting 3" off the lapua barrel would be necessary. With a little more calculations I think you can shorten it just enough to clean up the lapua chamber with a 338 lapua reamer. I don't see these numbers being "a lot" If I'm wrong please explain.
Thank you

[Robinhood]

Sharpshooter please elaborate......... With facts as to why it's a bad idea.

Pressure?

[devildogandboy]

check the dia of the cases.

Bruce

[sharpshooter]

A chamber of that diameter in a small shank barrel is asking for problems. On thing that will happen is sticky extraction. The barrel doesn't have enough meat around it to fully contain the pressure and will expand when the case does. After the pressure drops the barrel will contract, but the brass won't.
The next thing to happen is lug set back. The locking lugs on the bolthead will leave "foot prints" on the lug abutments, also adding to hard extraction.
There is a reason Savage uses large shank barrels and actions.

[junkout]

Shooter thanks for explaining it. I know they started making the RUM in a standard action and switched. So I assume they knew the action would hold up or it would of never been built. Not having enough barrel to hold the pressure is a different story although it's a 1k psi over a 338WM.
I already grabbed up a stainless long action large shank, just waiting on it to be delivered.

[efm77]

Sharpshooter is referring to using a 338 Lapua chamber on a small shank barrel. And he's completely right about that. But I believe you're talking about using the Lapua barrel and turning it in to a 338 RUM right? If so, you'd have to completely cut the chambered portion off. The Lapua is wider than the RUM so you'd have to get past the chamber portion in order to be able to ream a new chamber and as someone already stated, you're where the barrel is starting to taper. You'd be better off starting with a new barrel. You can chamber a RUM on a small shank with no problems. Regarding pressure, you can't just go by the pressure numbers alone. You have to consider that a larger cartridge exerts that pressure over a larger area which results in an increased amount of bolt thrust. So a win mag cartridge running at 60k psi is not going to exert as much force on the bolt lugs as a Lapua or even a RUM running at the same pressure.

[scope eye]

I have never really understood that argument about small shank Savages and WSM and RUM rounds, a Rem 700 is 1.062 compared to the Savages 1.055 so basically the barrels are the same size Dia yet you never hear about barrel expansion or the effects of it. to further expand on this look at any Weatherby whether it is a 257 or a 460 they have the same size barrel Dia. Go figure.

Dean

[efm77]

Scope Eye, those others you mention also have shouldered barrels so the outside diameter of what's beyond the receiver is larger, thus having more meat around the chamber. With a nut, you don't have that extra barrel thickness. I believe that's why Savage went to the large shank because it makes the chamber wall just enough thicker to give a better safety margin for that portion outside the receiver. Now some may argue that the barrel nut itself adds an extra layer of protection around the barrel. I can see that argument too but I'm not sure how true it is.

[scope eye]

I Had thought of the shoulder as part of the design to increase strength, the thing is the shoulder section of the barrel is very short compared to RUM case and is at the rim end of the case oppose to the neck where most of the pressure is.

Dean

[efm77]

I think I understand what you're saying. I always thought the shouldered portion of the barrel was made roughly long enough to cover the chamber area to not be a problem. I could be wrong though. I've always questioned, on a Remington, the portion under the recoil lug (for larger chambers). There you've got the small shank, essentially, with deeper threads than a savage, that's neither inside the receiver nor part of the shoulder. That's probably really overthinking it as I've never heard of any problems with them.