Can a .357 dia 180gr. bullet function in a .366 bore 9.3x62 case & rifle ?


December 3, 2012, 06:09 AM
My CZ 550 American is great! 3 shot clusters at 100, 5 shots in 1 1/2 at 200 with most bullets. Recoil is more a push than a whack. No belt to possibly cause feeding problems, and 1 more round in the mag. Bullets aren't hard to get, see Midway. RL 15 is your friend, Varget is about as good. Guy on the Ruger forum says he runs 375 bullets thru a 366 Lee bullet sizing die, they shoot fine. He has killed a LOT of stuff with his 9.3s. Cases no problem, available from most major makers, even Winchester now. You can also expand the necks of 30-06, possibly a mild fireform, and make them that way. Ruger is now making rifles, too. I myself would stay with the CZ. Did you know they come with a standard set trigger?
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Old Today, 06:44 AM #9

Join Date: February 9, 2011
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Is the "guy" who resizes .375 bullets to .366 limited to cast bullets/will brass work (orig. reply title)

I too am interested in the CZ550 in 9.3x62 as a North American DG rifle, specifically to stalk and shoot wild boars at close range , less than 50 yards. However, I want to be able to feed my hunting habit, without any concern for bullet cost or at least reducing per round cost for the 9.3x62 which is quite expensive in comparison to shooting .223 for most factory ammo. I reload for my other firearms and even considered the possibility of using a .357 dia. 180 gr. pistol bullet and crimp the brass on a .366 dia. 9.3 x 62 case to save costs in making an inexpensive
hog blasting bullet that would fire at approx, 3100 fps. This reloading recipe at this stage was just my guestimation of velocity and practicality. I hesitate on this because of questions and safety concerns about potential excessive pressure. Thus my interest in how does that "guy on Ruger" or anybody else who is knowledgeable
about internal ballistics, make a .375 brass bullet function in a .366 dia. bore rifle ? Can a 357. dia 180 gr. pistol bullet function atop 43.8 gr. H 4350 as a hog round ? Explain.
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December 3, 2012, 08:51 AM
The undersized bullet will likely give mediocre accuracy. But also note that any 357 bullet will be far lighter than what your rifle was designed to use. These short bullets may stabilize due to rifling rate. I suspect proper .366" lead bullets are available but probably not as cheap as the mass produced .357" size.

December 3, 2012, 09:25 AM
As a responsible and ethical hunter and firearm enthusiast, SAFETY is my first concern.This thread is just my speculating on the possibilities of developing a rifle load for a 9.3x62 rifle with a .366 dia bore by using .357 magnum pistol bullets. What would be the effects of the diminished approx. .009 in. neck dia.not just on accuracy ,but most importantly on safe function. The motive being the ability to shoot hundreds of rounds yearly in a BA 9.3x62 reloaded ammo in the price range of .223/5.56.

December 3, 2012, 09:34 AM
Your brass life will likely be seriously reduced. Accuracy will also be pretty awful shooting bullets that are that much undersized.

Jim Watson
December 3, 2012, 09:43 AM
Your rifle does not have a BORE of .366", it has a groove diameter of .366".
If the grooves are .004" deep, then the bore diameter is .358" and a .357" revolver bullet would not engage the rifling at all. Likely European rifling is a bit deeper and there would be a little engraving of the bullet and the short pistol bullet would be stabilized. That does not mean it would be accurate.
Blowing a lightweight undersize bullet out at high velocity would allow a lot of hot gas blowby and I would expect accelerated erosion of the barrel.

In short, I do not consider it worth fooling with.

If you were determined to shoot a 9.3 a LOT, it might be worth investing in bumping dies to enlarge a .358" jacketed RIFLE bullet to .366". The tooling would cost a good bit, but you might save that in cheaper bullets before the barrel was shot out.

The smart move would be cast bullets. Proper fit, proper weight, and you could get maybe 75% performance with the right alloy, lube, and diameter. Barrel wear would be less than with jacketed because the softer bullet seals the gas better. But that would probably call for a custom mould and the rest of the gear. Not cheap, either, but it would bring the per-round cost way down with less wear and tear on the gun.

December 3, 2012, 10:16 AM
Thanks JIM for the well informed explanation of the distinction between bullet dia. and bore diameter as measured between the grroves. The personal inquiry arose from the January 2012 post in which a member cited someone using .375
bullets in a .366 FL die for his CZ550 in 9.3x63. I was speculating that a .357 magnum 180 gr. FMJ TYPE BULLET WITH A LEAD BASE would perhaps expand on firing from the 9.3x62 case in order to engage the rifling for short range, less than 50 yard hog head accuracy. However, your input about throat erosion has created a pause in such reloading plans.
Perhaps because of the longevity and proliferation of guns chambered in 375 H&H a wider and less expensive variety of .375 bullets are available for reloading as compared to .366. It is still not clear if .375 brass bullets can be safely sized in a .366 LEE die for use in 9.3x63. Could someone clarify this point. Thanks,:)

December 3, 2012, 10:57 AM
The smart move would be cast bullets.


I'd used a gas check too.

December 3, 2012, 11:37 AM
I posted this in response to your question in the other thread this morning:

Well first of all, no centerfire is going to be as cheap to shoot as a .223, especially one that throws 286 gr bullets. Material costs alone are obviously going to make the 9.3 more expensive to shoot, that said, it will also be far more potent than any .223 round.

Swaging .375 bullets down to .366 is one thing because you are basically forcing a larger bullet (.375) through a bullet sizing die in order to extrude it to a smaller diameter (.366). Your only real concerns here would be ensuring that your final diameter was appropriate to your bore, and that the lead core and copper jacket have had a similar amount of spring-back.... which they don't but it seems like lots of folks have done it successfully, so maybe its not too big of a deal.

As for using a .357 bullet in a 9.3, that idea will not work. even if you crimp a .357 bullet into a 9.3 case, the bullet will still be too small for the rifle's bore. At the very least this will result in a slow load with poor accuracy, but it could also lead to a dangerous situation. Basically, this idea is a no go, but if you really want to shoot .357 bullets in a rifle, why not just get a 35 Whelen? The Whelen would allow you to do exactly what you're describing here.

These are the cheapest bullets made for the 9.3, and should work fine for hogs.

Although they are currently out of stock, Grafs usually has them available, and I imagine they will be back in stock before too long.

Additionally, if you really want an american made bullet, the speer is the most affordable in this caliber.

Here's a link to a post from a guy that's swaging 375 to 9.3, it seems like there is a little machining involved in opening up the dies.

If all of this is still too expensive, you might want to consider sticking with .223, or maybe giving .308 a try.

I would agree with Jim Watson, a .357 bullet in a .366 bore is just really not worth the headache you're going to create. If you're looking for a 180 gr bullet at 3100 fps, why not just get a 300 win mag and be done with it. Also I'm all for saving dough, but you gots to pay to play and if $28 for 100 bullets is too much, the 9.3 is probably not for you.

December 3, 2012, 09:08 PM
Gtscotty : After reading your reply and evaluating the available evidence, one of the first things I did was try to follow the link to Grafs and sons to explore another source for reloading supplies. Previously, I had been content to one stop online shop with Larry Potterfield (gotta love that guy- I even love the name of his company) of MIDWAY USA for most of my reloading materials. But competition in the market is good when it advances product development and good ole AMERICAN INGENUITY is what helps make this country the greatest.

Now, I am touching upon the principle of my inquiry of can a .357 bullet function in a 9.3x63 rifle case, the ideal of improving Otto Boc's well established
cartridge by merging its case capacity with an iconic American pistol caliber .357 magnum. I do believe that Elmer Keith and D.B. Wesson developed this round with game hunting in mind. It is part of our American work ethic to conceive of achieving what most others consider impossible. Those brothers up at Kitty Hawk proved that man was meant to fly and ushered into existence the global airplane industry, both civilian and military.
Perhaps it is the competitive spark in me that thought, hey the Europeans,
Sig Sauer. appropriated the nomenclature of an iconic American cartridge and designed ammunition that sought to duplicate the ballistic performance of the .357 Magnum in a semi automatic platform. IMHO they (SIG) really
have designed a formidable round, based on duplicating proven performance. I believe that we should return the favor to the global hunting brotherhood and design a rifle using the venerable 9.3x62 case of S.African origin and develop a rifle with the optimum twist rate and bore to fire a longer .357 dia. bullet in weights from 125+gr. to 325gr, eclipsing the venerable American made 30-06 Springfield on the upper end of the bullet weight spectrum and delivering DROP DEAD terminal performance to all North American game and most other DG as well.

By the way, the expense of any ammunition to any serious hunter is not a limiting factor, because we realize that in the field, effective ammo is a life and death matter.

Thanks for the feedback to all, I think I will stick to buying proper sized bullets for now and to continue pondering and contemplating the possibilities of achieving the impossible in ballistic performance through American ingenuity.


"The foreign lords have so wheedled and enticed us simple confederates, seeking their own profit, that at length they have brought us into such danger and disagreement between ourselves that we, not regarding our fatherland, have more care how to maintain them in their wealth and power than to defend our own houses, wives and children."- ZWINGLI

Jim Watson
December 3, 2012, 09:51 PM
develop a rifle with the optimum twist rate and bore to fire a longer .357 dia. bullet in weights from 125+gr. to 325gr,

They called that a .35 Whelen in the 1920s. Or a .35 G&H Magnum in the 1930s. Or a .35 Newton in 1915.

December 4, 2012, 12:13 AM
Jim Watson,
The recognition of the 35 Whelan and the several other cartridges that perhaps began as "wildcat" designs that you cited has been duly deposited in my memory bank. I will explore them in more detail later. It is hoped that the continued pursuit of ballistic improvements will not be impeded simply because other similar cartridges exist in the same caliber. Is it productive to acknowledge that since most American designed 30 caliber rifle cartridges use a .308 dia. bullet, then gunsmiths should have never sought any improved cartridge designs and rifles of the same .308 caliber since 1906, with the introduction of the 30-06 Springfield that is still proficient at taking all North American game, including the aggressive Grizzly and Kodiak bears of Alaska.
Personally, I am quite enthusiastic about the derivatives of the 30-06, such as the .308 as well as the early 2000 introduction of the Winchester Short Magnum in .300. All which use the same dia. bullet of .308.

Given my "ruthers" I would rather hunt Kodiak bear at long range with a .300wsm in 2013 than to have faced one a century earlier with a 30-06 at any distance , like other hunters did as I am told and survived to tell the tale. Upgrading my " ruthers " in hunting Dangerous Game at long range, I would opt for the .338 Lapua Magnum. Still within the context of .30 caliber.

I will stitch the above thoughts back into the fabric of this thread and the higher principles and practices of this forum by stating that informed discussion is a good thing for our democracy as well as the right of American citizens to keep and bear arms in order to protect such liberty from all enemies both foreign or domestic.


"The foreign lords have so wheedled and enticed us simple confederates, seeking their own profit, that at length they have brought us into such danger and disagreement between ourselves that we, not regarding our fatherland, have more care how to maintain them in their wealth and power than to defend our own houses, wives and children."- ZWINGLI

Jim Watson
December 4, 2012, 08:56 AM
The key improvement since 1906 has been the development of ever more progressive powders to make use of the available case volumes. The .30 Adolph Express (which the .30 Newton was based on) is about as big a case as you can justify for the .30-.35 range of calibers. That much slow burning powder will generate ample power (And recoil!) for anything needing to be done by those bullets. Even the cases for traditional big bores of .375-.458 are not appreciably bigger. They generate enough horsepower (And recoil!) for any application.

We are now getting the monster magnums. Presumably the game is tougher and warier so must be shot harder and from longer range. And, of course, our hunters are better practiced to make the shot and stand the kick. So if you want to snipe a bear from outside mauling range, you can buy a .338 Lapua sporting rifle. The which I did not suspect the existence of, I was looking up the .338-.378 Weatherby and there is was, a .338 Lap Mk V.

The big advertising campaign of recent seasons has been to promote the short fat case which fits a shorter action with comparable ballistics to the suddenly obsolete cartridges that served well for 50-100 years. I think the "efficiency" of a short fat case and the "stiffness" of a short action are of more value to the benchrest shooter than the hunter, but the companies have to have something to sell. That can be tough when you are dealing in products as durable as a good firearm. You must convince the customer that he NEEDS a .300 WSM which will surely be better than his .300 Win Mag.

December 5, 2012, 04:46 AM
Col. Whelan got it right on point when he designed the .35 Whelan in 1922 by resizing the 30-06 to use a .358 dia. bullet. According to what I read within the last 24 hours, The .35 Whelan rifle cartridge can utilize a 180 gr. .357 magnum pistol round effectively, without the unwarranted risks or die retooling that would make the same pistol round feasible for the 9.3x63.

December 5, 2012, 06:10 AM
Bingo, with the Whelen you can, at least theoretically, go from 158 gr XTP 357 Mag bullets all the way up to 280 gr swift A-frames and 310 gr Woodleighs. They probably won't all shoot with equal accuracy, but the capability is there.

Edit: If you want to try a Whelen on the cheap, you can always pick up a used Savage 110, and swap the barrel yourself with a kit like this:

Its no CZ, but I used that exact kit once upon a time and had a grand total of $450 in the rifle... can't beat that for thrift. If you want something a little nicer, Remington used to make the 700 in 35 Whelen, and you can pick them up used on GB from time to time:

December 5, 2012, 01:48 PM
MB, do you have your grammer-checker set to "Hemingway style"? It is a bit melodramatic.

I concur with the others that say to go with the Whelen. Just a few thousands' of an inch difference. Most likely though you'd be less than satisfided shooting a 180 grain bullet in either caliber. More likely you'll be pleased with something along the lines of 250 grains.

There are two other options not yet mentioned here. You could request a custom .366 swaging die made from I've made swaged bullets for .357 out of .223 cases. You could make .366 bullets the same way.

Another alterative is paper-patching. That is wrapping a sliver of paper around the bullet to increase it's diameter. This is gone with some cast bullets as an alterative to greasing. It would increase the bullet diameter to match the .366 bore.

Jim Watson
December 5, 2012, 05:40 PM
I once had a Remington 600 in .35 Remington, much smaller than .35 Whelen.
It would blow a .357 revolver bullet out at high velocity and adequate accuracy for plinking and offhand practice. I would not try to cut corners on bullet construction for hunting. A pistol bullet has a thin unreinforced jacket and may well come apart on impact at rifle velocity.

December 5, 2012, 06:49 PM
MB, do you have your grammer-checker set to "Hemingway style"? It is a bit melodramatic.

Hilarious, I too thought things were getting a bit theatrical in this thread, but being a simple engineer, I decided to play it cool in case it was just me.

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