Cross posted from GD where it got plenty of traffic but no answers:

Are the barrels screwed in on a GSR?

Who can do this, I want one?

I want a relatively short, light, large caliber, detachable magazine, iron sights at the rear receiver bridge, integral 1913 optics rail, in .450 Bushmaster. I want it as a travel companion and a bolt rifle will make it through most states without undue hardship. Canada is also a consideration so if anyone is familiar with Canadjian laws pertaining to travel with a firearm please weigh in.

Anyone aware of these being done?

On a Savage maybe?

You need to be looking at cartridges based on the 308 (bolt face and magazine compatibility). A gunsmith should be able to rebarrel to 338 Federal or 358 Winchester. With the GSRs stepped barrel profile, this could get pricey for custom work.

Thanks for the reply, but I specifically want .450 Bushmaster.

I want to buy a .223 model so the magazines will work, and switch bolt faces to a .308.

I realize this will require a new custom barrel and that doesn't bother me, I'm just looking for a 'smith to do it.

I see McGowen makes Savage pre-fits so maybe they can do one which would take the gunsmith need out of the equation, although I like the Ruger much more than the Savage as an over all package. I know the Savage are good guns and have an old 110FP which has been a good rifle, but I think by the time I make the Savage as nice as the Ruger is off the showroom floor I'll have the same money in it..
.

Might look @ the Mossberg - DPMS mags, .473" boltface, interchangeable bbls like a Savage.  Would have to have a custom bbl.

Tromix is already converting 'em for .458" SOCOM, but I'm sure you've got your reasons for the Bushmaster.

I haven't thought about the Mossberg, thanks.

The mags need to be 5.56/.223 over all length or extensive magazine mods will be required, which is why I am leaning toward a .223 model and changing the bolt head, or relieving the bolt face.

I have an AR in .450 which is one of the reasons, and the principle reason I bought a .450 to begin which is reasonable and readily available factory loaded ammo.

The .450 is no slouch, and I would trust it for a one shot stop on man or most beast scuffling about North America.

Then you need a Tromix bolt for the Mossberg in .223", use Bushmaster mags, and you'll need a custom bbl - Tromix might do it, but he's set up for the .458" SOCOM, since he helped develop the cartridge.  Might buy the Mossy in .300"; if you don't shoot it, flip the bbl, will be worth more than flipping a .223" bbl you'll probably never use.  Don't get the Mossy in .308", then, get the short action.

He sells some .450 barrels and odds and ends, I was just looking at his site and didn't see any of the MVP conversions or barrels for sale, but did see some trigger guards, mag wells etc.. I'll contact him and see what he says.

I was also looking at the Mossberg site, and the "Scout" configuration looks like what I want with regards to a rear sight mounted on the rear receiver bridge but no .223/5.56, so maybe they will sell that part or it is a third party part. I don't like how it bridges the receiver though and would prefer a stand alone rear like is on the GSR with a forward mounted rail. The MVP's look to be nicely priced as well.

Thanks for the redirection.

ETA: with further reading it looks like Tromix has scrapped their MVP barrel project, never got the .458's into production, and make only trigger guards and mag wells for the MVP.

Well, bugger.  My brother will be disappointed.  ETA:  Savage might be the way to go then.  Easy enough to screw on a different bolt w/ a larger face & change out the bbl.