.416 to .404 Jeffrey?

Rumrunner · Feb 6, 2026

I have a Model 70 in .416 rem mag I am considering putting in a new barrel. Bought the rifle used. Current barrel has quite a bit of pitting although it shoots well so may be unnecessary. What I am wondering is it possible to re-barrel and chamber to a .404 Jeffery? Would something like this be cost prohibitive?

ThinusS · Feb 6, 2026

If the barrel shoots well, why do you want to replace it? Ballistically there is no noticeable difference as far as performance on game is concerned.
If you really want a .404 for the sake of having a .404, re-barrel it, it is certainly possible, but otherwise, you are not gaining anything. Cost prohibitive is a very relative term, depending on how much you are willing to spend on re-barreling to a caliber that might make you happy but won't offer any real advantage.

Rez Exelon · Feb 6, 2026

I've got a weird wild cat that I have a thread about somewhere. Let me just say you do NOT want to take a 416 barrel and make it into a 416/404 Jeffery (404 Jeffery case using a .423 bullet). Ugh, this project really just bakes my cake.

uplander01 · Feb 6, 2026

If it shoots I wouldn't mess with it. Wait and find the right 404, and buy another rifle

Rumrunner · Feb 6, 2026

Thanks for the replies. Greatly appreciated. Since it’s not broke I won’t fix it. If issues arise in the future I’ll replace the .416 barrel with another .416.
I really would like a .404 Jeffery but I’m too practical to spend money if it’s not going to be a significant difference or capability.
Again the replies are greatly appreciated.

Ontario Hunter · Feb 6, 2026

I think it can be done but involves more than just swapping barrels. 416 has a wider case rim which MIGHT require changing the extractor to one with more claw. The cartridge overall length is also significantly longer than 404J which would require putting a spacer in the mag box and maybe/probably shortening the follower. I THINK there might be enough meat left in 416 feeding rails to hold the narrower 404 cases in the wider box.

If you can get your hands on a couple of dummy 404J rounds, it would be interesting to see if the bolt face picks them up from the magazine. Push both cartridges to the back of the box and try closing the bolt. Hopefully they won't jump out from under the rails prematurely. Too late is okay (but I think unlikely). That means the rails can be reshaped. If the cartridges won't stay under the rails or jump to the bolt face too early, that usually means not enough metal on the rails for a thinner cartridge. If the 404J cartridge dummies load out of magazine okay, then order a barrel and go to work shortening the box and follower.

fourfive8 · Feb 8, 2026

Good decision on staying with 416 Rem! Other than the 404 Jeff being trendy and rolling off the tongue in camp fire discussions, the 416 Rem is as good as if not a better choice to begin with. And, especially so since your M70 action is already set up for it. Very straight forward to replace barrel and chamber to 416 Rem in future if needed.

Mark A Ouellette · Feb 8, 2026

fourfive8 said:
Good decision on staying with 416 Rem! Other than the 404 Jeff being trendy and rolling off the tongue in camp fire discussions, the 416 Rem is as good as if not a better choice to begin with. And, especially so since your M70 action is already set up for it. Very straight forward to replace barrel and chamber to 416 Rem in future if needed.

Exactly!

A .404 Jeffery is nostalgic but not significantly, if at all any better than any of the .416 cartridges. In an older British rifle, a .404 would be a dream. In a modern rifle, it’s just personal preference. Factor in availability of ammunition and/or brass and those .423” bullets compared the .416 Rem or Rigby, and the .404 is but a personal preference. But hey, whatever flips your trigger!

Here's one of my recoil, energy, and Knock Out Factor charts for comparison...

Ontario Hunter · Feb 8, 2026

I thought he had a 416 Rigby. My mistake. Conversion to 404 from 416 Rem would be easier than 416 Rigby. I actually used 416 Rem bottom metal for my 404J build on 98 Mauser. It worked perfectly without modification. The 416 Rem follower and loading ramp should also require no modification. The bolt face might need to be opened slightly but that's not a big deal. Leaves only feeding rails. That should not be a big problem. 416 Rem has a narrower shoulder therefore the 416 Rem in theory will have more metal in the rails. It's possible to trim metal from rails as needed but much more difficult ($$$) to add metal to them.

Rez Exelon · Feb 24, 2026

So circling back to this thread, I started cleaning the garage and reloading area, and for better or worse I'm back to dealing with the project.

Talked to CH4D regarding dies today, and after checking a series of measurements, they've advised the believe the dies were made back in a time when brass walls were thicker. Or at least whatever brass they used to blueprint the dies was thicker. My measurements were taken with a piece of vintage RWS brass and a new manufacture Hornady brass (which it killed me to take the 404 Jeffery round apart, but it is what it is):

RWS:
Outer Diameter - .439
Wall Measure 1 - .011
Wall Measure 2 - .012
Inner Diameter - .416

On the Hornady:

Outer Diameter - .441
Wall Measure 1 - .013
Wall Measure 2 - .013
Inner Diameter - .415

So the Hornady brass is definitely a bit thicker, but not enough to get neck tension. Both of those are showing below what I think is the neck thickness of .449. Another aspect that I've measured is that after shoving a lead projo through the barrel, it measures out at .416.

So all that said, could the solution to this problem just be to acquire and use the 400ish grain.418 lead projectiles like Hunter Supply sells? To be honest I don't think I've ever wondered if shoving a .418 projo through a .416 opening is a terrible idea or not enough to matter.

deewayne2003 · Feb 24, 2026

Mark A Ouellette said:
Exactly!

A .404 Jeffery is nostalgic but not significantly, if at all any better than any of the .416 cartridges. In an older British rifle, a .404 would be a dream. In a modern rifle, it’s just personal preference. Factor in availability of ammunition and/or brass and those .423” bullets compared the .416 Rem or Rigby, and the .404 is but a personal preference. But hey, whatever flips your trigger!

Here's one of my recoil, energy, and Knock Out Factor charts for comparison...

View attachment 744461

Fully agree, I sold my .416Rigby because it had a 2 +1 capacity and the .404J in a ZKK602 gives me 4+1 capacity.

Dennis Olson has had the barrel and action and parts for 3 years now; I just ordered a B&C stock and had it shipped to him and told him to cerakote it and be done.

Point being I would have been much better off buying a good .416Rigby custom like the one @BJH65 just sold on this forum.

Would have saved thousands, and I think staying .416 is much wiser than my route.

RootballExpress · Feb 26, 2026

I’d keep the 416 Rem Mag as is. It’s an awesome cartridge and the Win Model 70’s is the perfect platform for that caliber IMO. Very versatile. Bullets, brass, and all other components imaginable are readily available.

Rez Exelon · Feb 26, 2026

Rez Exelon said:
So circling back to this thread, I started cleaning the garage and reloading area, and for better or worse I'm back to dealing with the project.

Talked to CH4D regarding dies today, and after checking a series of measurements, they've advised the believe the dies were made back in a time when brass walls were thicker. Or at least whatever brass they used to blueprint the dies was thicker. My measurements were taken with a piece of vintage RWS brass and a new manufacture Hornady brass (which it killed me to take the 404 Jeffery round apart, but it is what it is):

RWS:
Outer Diameter - .439
Wall Measure 1 - .011
Wall Measure 2 - .012
Inner Diameter - .416

On the Hornady:

Outer Diameter - .441
Wall Measure 1 - .013
Wall Measure 2 - .013
Inner Diameter - .415

So the Hornady brass is definitely a bit thicker, but not enough to get neck tension. Both of those are showing below what I think is the neck thickness of .449. Another aspect that I've measured is that after shoving a lead projo through the barrel, it measures out at .416.

So all that said, could the solution to this problem just be to acquire and use the 400ish grain.418 lead projectiles like Hunter Supply sells? To be honest I don't think I've ever wondered if shoving a .418 projo through a .416 opening is a terrible idea or not enough to matter.

Oops....I totally posted this on the wrong thread. Thought I was on my own about what the heck to do with a project of mine.

.416 to .404 Jeffrey?

Rumrunner

ThinusS

Rez Exelon

uplander01

Rumrunner

Ontario Hunter

fourfive8

Mark A Ouellette

Ontario Hunter

Rez Exelon

deewayne2003

RootballExpress

Rez Exelon

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