I have a couple 458 Lotts. I was thinking of converting a Ruger RSM to 450 Rigby.

Is this doable??? Would there be any headaches getting the rifle to feed correctly??

Thanks!!

According to AmmoGuide, Yes.

However, in the diagrams the Lott has a .481" outside neck diameter while the Rigby is .475" outside neck diameter. This may be neglible and may even be desirable, giving your Rigby more margin in the neck while still having headspace on a shoulder.

On feeding, a good gunsmith can open up a control-feed boltface and modify the claw. McGowen can do a barrel with an integral, forearm recoil lug, a la CZ. The rails may need slight enlarging though a person needs to go conservative on this. Otherwise a round may pop up and out too easily. Finally, the biggest item of all is the feed ramp. This must be checked for use with flat-nose solids. If necessary, the sides and bottom of the feed ramp can be slightly opened up with a dremel. This opening of the feed ramp applies to the Lott as well as the Rigby.

In my view, the 450 Rigby is a GREAT use of the .458" diameter. It has the capacity to drive bullets at velocities that make the 450 an all-around rifle for DG and plains game, flat out to 300 yards. Try the 400grain GSC for all around plains game. 2600fps should still be fairly comfortable, relatively low pressure, and you can go faster if you wish. A 450 or 500 TSX will provide outstanding penetration for buffalo and a flat-nose solid is a great back-up round.

yes, its doable -
do understand that the 450 rigby is a NEW round -- labeled, if not invented, in the 90s.

if i was looking at this, since i have hundreds of brass, i would do a 450 dakota - headstamped brass is cheaper .. lots and lots cheaper

reamer, open the bolt face, get a 416 rigby mag box, and you should be done ... might even get lucky and find a 416 rigby bolt, and use that

can be done, simple job, will result in a larger case, though 500gr at 2300 is always a good answer

i think i need to do a 460 AccRel -- take my 500/490/476 case down to .458 .... though, in all honesty, that results in a short 450 dakota ... might be too crowded a field

Maybe better would be to trade/sell one of the 458s and get a 416 to rebore. Some of them had quite heavy barrels iirc.
That seems like a more straightforward conversion to me.

quote:

i think i need to do a 460 AccRel -- take my 500/490/476 case down to .458 .... though, in all honesty, that results in a short 450 dakota ... might be too crowded a field

Jeff,
Maybe I'm glad you didn't do a 460 based on a Hawkeye action Rigby casehead. I might not have gone all the way to the 500, which is quite a balanced DG load. Not to mention the $1.27/piece brass, but alas, a one time opportunity.

Since the thread writer already has a long action, a 450 Rigby should be in the cards over a shorter 460 wildcat.

quote:

Maybe better would be to trade/sell one of the 458s and get a 416 to rebore. Some of them had quite heavy barrels iirc.That seems like a more straightforward conversion to me.

+1. I have one of those first generation RSM's in 416 Rigby. Plenty of meat in those barrels for a 450 Rigby rebore. You could also go with a 470 Mbogo.

That is good to know about the 'meat' on the 416 Rigby in the RSM. Before going to a 470 one should consider bullet selection available. Admittedly, the 500Mbogo might need a new barrel, but bullet selection is a desideratum before a new build. If you find a .474?" bullet, go for it and fit the barrel to the bullet diameter. But there will almost certainly be some great .458" bullets.

Duncans Gunworks in San Marcos CA has a Ruger RSM rechambered to 450 Dakota on the used gun rack. Great condition and I think its around $1250.

Let us fondly recall the Ruger Model 77 RSM,
with reference to the "Blue Book of Gun Values" and collective memory of sumbuddy who know:

Model 77 RSM:

1990: The Generation I RSM
Chamberings are .375 H&H and .416 Rigby.
Barrels are 24" long and as fat as 0.810" muzzle diameter for the .416 Rigby.
Front sling base is on a barrel-band that is imbedded through the forearm.

1998, or earlier: The Generation II RSM
Chamberings are still for.375 H&H and .416 Rigby only.
Barrels are still 24" long and as fat as 0.810" muzzle diameter for the .416 Rigby.
Front sling base is now moved to a barrel-band that is beyond the forend tip, no longer in the forearm wood.
The .416 Rigby RSM Gen II weighs 10.75 pounds dry.

2002, no later: The Generation III RSM
Chamberings include .375 H&H, .416 Rigby, and .458 Lott.
Barrels are shortened to 23" long and slimmed to 0.750" muzzle diameter for all of them, IIRC.
Front sling base as on Gen II.
The .416 Rigby RSM Gen III weighs 9.5 pounds dry.

2010: Last year of production for the M77 RSM.

In 1998 I saw Hamilton Bowen had already been turning the RSM .416 Rigby rifles into .505 Gibbs by re-boring.
Member Canuck has a 470 Mbogo similarly done with excellent results, acquired from Dave Estergaard IIRC.

Rip ...

I also have a Ruger RSM in 416 Rigby. It is an older model, from the early 90's. I haven't shot it a long time.

Would it be easier to convert the 416 Rigby to 450 Rigby???

quote:

Would it be easier to convert the 416 Rigby to 450 Rigby???

I'm no gunsmith but I'm pretty sure all that would be necessary is a rebore of your existing barrel. Same case as the 416 Rigby, just necked up to .458 caliber.

BTW - My daughter graduated from Duke.

T B D,

Do you have a goal in mind for this down the line 450 Rigby?
I ask because there is more than one way to attain most goals.
We know neither the 45 cal. Rigby nor Dakota is in the "classic" category.
If you want a non-belted monster you could use 505 Gibbs brass necked down.
If BELTED suits you, Hubel's 585 HE is the same as 505 and can be necked down.
So I'm quite curious as to your goal, max Feet Per Second with 500 grainers???

I just happen to have a .416 Rigby RSM MK II (thanks Biebs) destined for exactly this conversion... when I get around to it and Wayne has time.

I picked up a bunch of new .450 Dakota brass here and there for cheap and figured I needed another .458 (like I need another hole in my head) that sits even with or a little above my .460 Weatherby. That’s the theory anyway, and I’m sticking to it.

Great idea re-boring a .416 Rigby RSM to 450 Dakota.
I like 450 Dakotas.
I like westerns.
Hostiles is worth a watch.
Good acting job by this "Englishman" born in Wales:



Her too, English!:



We gotta import Englishers to play in Westerns?
Hell, I would have taken the job for free!
I'd even shave and wear the dress!

Rip ...

Any of the RSM's would make a dandy 450 Dakota, IMHO.
Rebore any of them with .750" muzzle on 23" barrel,
or .810" muzzle on a 24" barrel.
Here is my phat-barreled .416 Rigby RSM, too accurate to re-bore, I'll re-consider if I ever wear out the rifling: 10.75# dry weight



I like 450 Dakotas.

Here is my 450 Dakota: 9.5# dry weight, slim-barreled, lively







Prechtl action.
Gottfried is on the right below, the one with the red hair on his lip:



The SIG Arms Magnum Mauser 98 has a 25" barrel and only a .670" muzzle diameter, and it does fine.
That is the same length and muzzle diameter as on the CZ .458 WinMag and .458 Lott.
They do fine too.

Preserving the integral quarter rib on the Ruger RSM by reboring either a .375 or a .416 is the way to go,
but re-chambering a .458 Lott eliminates the need to re-bore.
That has a great appeal, and that would be a .750"/23" barrel, with integral quarter rib.
Might be just a little over 9 pounds dry weight.
Mighty spiffy. Slim and lively.
Like the redhead.
The phat-barreled-rebore would be at least a pound heavier. Over 10# dry weight.
Add scope, rings and ammo weight to that.
Flute the phat barrel as possible, while it is off the action?

I would maintain the original bedding system,
which I have found to be extremely accurate on the RSM.
Just be sure the bedding and stock reinforcements are the best possible.

Rip.