.355 bore 357 mag rifle which jacketed to try?

[PB234]

Came into a 357 mag rifle with a .355 bore which begs the question of does one try a 9mm (.355) jacketed bullet or a .357 diameter jacketed bullet. Concerns about using the .357 diameter in a .355 bore include a potential loss in accuracy from the mismatch or an increase in pressure. Advantages of using the .357 selection of jacketed are the wider variety of jacketed bullets available. Mostly this will be a cast boolit rifle, but wondering about the potential constraints presented by the .355 bore.

Thanks in advance

[2ndAmendmentNut]

First question. What type of rifle?

Second question. Are you really sure the bore is .355? What method of slugging did you use?

In the end as long as the rifle is of modern and otherwise safe construction I wouldn't worry about shooting a jacketed .357 diameter bullet in it. Just follow current load data. Even with jacketed bullets you still want them .001-.002 or so over bore size, so a .355 diameter bullet would not be ideal. Would work if you have a bunch of 9mm components to burn up, but I wouldn't feel that you need to limit yourself to .355 bullets.

[JSnover]

Way back in the day I never thought to Mic my jacketed bullets (and I still don't), just load and shoot IAW published load data. I doubt .002" oversized will cause any trouble but if it bothers you the standard warning should suffice: start low, work your way up.

[PB234]

It is a build off a Ruger 77/357 action using a Krieger barrel. Krieger says it is a .355. I'll accept that. I have little experience other than with an older .223 Hornet and the differences reported between using .224 and .223 bullets there, and realize many think matching the bore and the jacketed bullet to be the best course of action. Others suggest the jacketed should be .001 to .002 oversize which would make the .357 in a .355 a good possibility for perfect.

My course of action is to load up a bunch of .355 and .357 and see how they do. I would like the added choices of weights offered in the .357 diameter. Mostly it will be a cast boolit rifle but want to figure out its capabilities over a wide range of projectiles.

My idea behind this rifle is for a 100+ yard rifle that can run anything from very light 75g grain wadcutter loads (my adult BB gun) to 180 grain jacketed moving fast to a wide range of cast boolits at a variety of speeds.

The rifle is a beautiful example of solid exacting gunsmithing by Tim Malcolm. When I have rung it out a bit and get a better feel for it most likely I'll have a stock that fits me perfectly replace the current stock which like most commercial off the shelf stocks is built for the average person's body. It works for me mostly, but the rifle is better than that and deserves better. It is capable of less than 1 inch groups at 100 yards.

The real goal here is to have a cast load do sub minute of angle at 100 yards and use it for everything I do out to maybe 125/150 yards. Others do that and more with a CZ 527 Carbine, but I want a 38/357. One rifle from 75 grain lead wadcutters at maybe 700 fps to 180 grain jacketed screaming downrange is a very versatile rifle.

I'll probably start saving my pennies for a really nice piece of wood to build into a stock. Tim's workmanship is better than commercially produced stocks.

[Scharfschuetze]

My course of action is to load up a bunch of .355 and .357 and see how they do. I would like the added choices of weights offered in the .357 diameter. Mostly it will be a cast boolit rifle but want to figure out its capabilities over a wide range of projectiles.

Good plan PB. I believe that you'll find both diameters probably work pretty well given your bore diameter, but working up loads is de rigueur for both safety and accuracy. Older Colt revolvers had small bores like your rifle and they seemed to hold up pretty well using .357 and .358 diameter bullets.

I shoot my 357 Marlin CB out past 200 yards routinely with 180 grain cast boolits and jacketed bullets over Lil'Gun powder. Velocity is right at 1,750 over the chronograph and while accuracy isn't what your rifle promises, it's still quite usable at 3 MOA using an aperture rear sight.

[runfiverun]

your pressure won't increase enough to even notice it on a trace using 357's in a 355 groove barrel.
it'd be under a 1-k spike.
you'll see a slight increase in velocity.

where you will see a difference is if you use the rifle for hunting.
the extra cutting of the rifling into the jacket will affect terminal performance of the bullet.

[Outpost75]

A .355 is at minimum SAAMI spec for a .357 barrel, same as the standard industrial test barrel would be.

No issue.

Your .357 bullets will be fine.

John Krieger makes as good a barrel as money can buy.

[PB234]

Goodsteel put it together so that this is about as fine a cast boolit rifle as can be had. He shot some jacketed out of it at 100 yards within a minute of angle. My expectation is that with some load development the groups could tighten up. When I get the load worked out to produce less than an inch group at 100 yards using cast it will be time to get a stock fitting me perfectly to complete the effort. Using cast this cheaper than a 22 and it will never wear out using cast so it will be just a beautiful tool that never wears out and gets better as one gets to know it. And I hope to devise an accurate gallery load to make this a fun adult "BB gun" to play with.

[wiljen]

I have several 9mms that do their best work with .357 or .358 diameter slugs. As long as it will chamber the 9mm has never shown any indications of problems shooting slugs that are .003 over. I'd run standard 357 ammo through it and see how it behaves before I made any adjustments. You may find that it does great work with factory 357s and doesnt require a lot of adjustment to get good loads.

[GhostHawk]

If you are really concerned, (not that I would be, not for 2 thousandths) you could always run .357 bullets through a .356 sizer.

And yes you can size fmj though a lee sizer. I had some .310 fmj bullets pulled from 7.62x39 that I wanted to shoot in my .300bo and considered the jump just about 1 thousandth more than I liked. So I sized up 20 and loaded them.

IMO 2 thousandths large in cast is just about ideal. But there are guys who shoot 7.62x39 milsurp ammo which is .310 bullets though a mini 30 which has a .308 bore with no issues. Copper and lead vs steel, it will squeeze under pressure.

[northmn]

Almost every jacketed bullet for a 357 is 358. Saying that, the old Savage 303 and 22 HI-power used oversized bullets by design to get more velocity. Some did load the 303 with 308 bullets but another with the 311. Use starting loads and work up.

DEP

[PB234]

Thanks to everyone for the help. I have high hopes for this rifle : ) .

[mmkt]

.357 should be fine

[Outpost75]

There is no reason for concern firing .357-.358 jacketed bullets in the .355 groove diameter as long as you stay with published data. The SAAMI standard pressure and velocity test barrel for .357 Magnum reflects the minimum chamber, bore and groove dimensions and is a .355"!