450/400 Nitro Express 0.410" & 0.411" Projectiles

Who has the answer on this one for me, I've done a bit of searching and can't seem to find a clear answer.

0.410" & 0.411" projectiles for the 450/400 Nitro Express. Could I use the 0.411" projectiles in a modern Verney Carron double? I believe the Verney double was regulated with the Hornady 0.410" ammo.

Also if the 0.411" projectile is safe to use in the rifle, do you think it would change the accuracy of the rifle since it was regulated with the 0.410" projectile?

Maybe slug the bore?

I used 0.411" 300gr Hornady soft point (made for 405 Win) in a 0.410" bore regulated for 400gr Hornady bullets. It works fine, for practice, but the regulation and the open sights adjustment is out the window, of course.
If you have a QD scope on the VC, set the scope for one barrel, use it as a single shot rifle for light game at longer range. It works fine. Test where the 2nd barrel hits and know the difference.

The CIP grove diameter is .410 for the .450/400 NE 3”. Therefore, shooting .411 in your double could stress barrel joining especially with monolithic solids.

I did some reading in this. I want to shoot a soft point .411 out of my Ruger No.1.
From reading on the Internet, I do not remember which bullet maker said what, I do not feel like scrolling through pages again, so here goes.
One of the bullet makers advises against doing this as it would be unsafe.
A different maker said the .001 will not make a difference.
There people who have loaded the .411 in a double with no issues.
There are people advise against it.

Basically the advice is split.
If I was going to do this I would pick a powder similar to Trail Boss or 5744 and work from there.

I popped into the reloading area to ask our fellow AH members about this topic.

Bandera said:

I did some reading in this. I want to shoot a soft point .411 out of my Ruger No.1.

Click to expand...

I would not expect a stress/strain problem with your No.1 because it is a single barrel. Joined double barrels are subject to barrel joint stressing.

Schüler Jumbo said:

The CIP grove diameter is .410 for the .450/400 NE 3”. Therefore, shooting .411 in your double could stress barrel joining especially with monolithic solids.

Click to expand...

This is solid advice.
Woodleight makes the solid (FMJ) only in 0.410" diamter for both barrels - 0.410" AND 0.411".
There is no 0.411" solid for a reason. I would not try a monolithic 0.411" bullet in a 0.410" barrel.
Hornady 300gr 0.411" is a cup and core soft bullet. Using it there is no problem.
@Bandera is correct - I'm using Accurate 5744 reduced loads to get within the speed enevlope of the original Win 405. (I've pushed them too fast and then I backed down for better results).

I have personally verified all the above with Ed Hammond.

I'll include the link below for various 0.400" reduced loads.

cup and core bullets, i suspect you could use .411 bullets but why? the guns bore is very likely .410 and was likely regulated for such a bullet so why use one that is overbore?

i suspect mono metal bullets would likely stress the barrels on the gun if they were .411. the cup and core bullet would compress/conform to the .410 bore and be less likely to hurt anything but @V.Veritas has it right.

I'll just stick with the 0.410" projectiles, I managed to get my hands on 200 of them so I've got enough for quite a while now. Mind you I will probably use quite a few during load development.

Slug your bore and you will know. Just get a fishing sinker a bit bigger and drive it through with a wooden dowel. Make sure you measure with a micrometer not a caliper.
There’s a chance your barrel is .411

So I had my gunsmith slug the bores while it's there having a new recoil pad fitted. His response below.

Bores slugged, left 0.4105" & right 0.41075". Recommend using the 0.411" Woodleigh projectiles.

I must admit that I am really a double rifle novice, even though I own a few. I am a custom bullet maker and lifelong reloader for 45 years. It seems to me more than any other rifle type, doubles require a lot of "buy and try." Like others have said, I would not shoot ANY overbore mono-metal bullets, EVER, in any double. These fine guns are just to expensive to take the chance, and you could start a progression of ballistic consequences that could leave you chasing your own tail for a while.

1. For pure mono-metals, or premium bullets with mono-metal bases or mid sections, stick to .410,

2. For lead core, buy and try. You can always try them at .411 since your gunsmith says they are safe, then order a custom bullet sizing die to reduce them .0005, or .001 and try that. Stay with whichever regulates the best AND has best first shot accuracy.

As stated, I am a custom bullet maker so I swage my jacketed bullets to .416 for use in my .416 Ruger, Then run the bullets through a reducing die to get them to .411, .410, or whatever I want for my 400 Whelen. There is a much greater selection of .416 bullets if you have to buy them, and they will easily reduce to .410 or .411. This opens up all new possibilities, especially with supply chain issues being what they are. Even though I make my own, bullet swaging dies are costly and I have no problem with using reduced bullets, as long as you do not reduce a jacketed bullet more than .008 or so lower than original diameter. I only need one set of swaging dies for .416 to .410. If I have to reduce more than that, I buy a new set of swaging dies in the smaller caliber. If there is ever any question, I will order swaging dies .001 bigger and then reduce if needed. Reducing dies are cheap and time to reduce is negligible. Some calibers have a range of bore sizes depending on age and manufacture of the firearm, like the 450/400.

I’ve used both in my Westley 450/400. Can’t tell a difference. About 10-15fps faster with the .411’s.