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Discussion Starter #1
I've been using 125 grain CNBB hard cast bullets made by R&C Bullets for light/medium .357 magnum loads for several years with excellent results. These particular bullets are sized .357. I also intend to use these same bullets for light loads in my S&W 915 pistol. Should I resize them to .355 or .356 caliber?[/color]
 

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G’day Greysky,

I would probably use the projectiles left as is at .357 if the loaded rounds chamber and function properly.

I am currently shooting a 9mm CZ SP-01 which has a groove diameter of .356 and it shoots more accurately and cleaner with .357 projectiles, the same applied to a custom 9mm “Barsto” barrelled CZ 75 which also slugged at .356+.

If the groove diameter of your S&W 915 is closer to .355 (which I doubt) you could size them to .356. I have found that slightly oversize is better when using hard cast projectiles at standard pressures, as hard undersized projectiles can’t expand to fill the rifling unless the pressures are near maximum and that will cause gas cutting (high pressure gas leaking past the projectile) which will erode the projectile, increase leading and reduce accuracy.

Paul
 

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Discussion Starter #3
Paul said:
G’day Greysky,

I would probably use the projectiles left as is at .357 if the loaded rounds chamber and function properly.

I am currently shooting a 9mm CZ SP-01 which has a groove diameter of .356 and it shoots more accurately and cleaner with .357 projectiles, the same applied to a custom 9mm “Barsto” barrelled CZ 75 which also slugged at .356+.

If the groove diameter of your S&W 915 is closer to .355 (which I doubt) you could size them to .356. I have found that slightly oversize is better when using hard cast projectiles at standard pressures, as hard undersized projectiles can’t expand to fill the rifling unless the pressures are near maximum and that will cause gas cutting (high pressure gas leaking past the projectile) which will erode the projectile, increase leading and reduce accuracy.

Paul
Thank you for your considerate reply.

My main concern is the risk of increasing pressure by not resizing these particular HC bullets, which are quite long, and will have to be seated deeper in the rather stubby 9mm cases to reliably function in my 915 pistol.

Do you think I have cause for concern here?
 

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The increase in diameter is not a problem. The deeper seating is....

You will need to work up a load from below to compensate for the increased seating depth and reduced case capacity.
 

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G’day Greysky,

I agree with 454PB, the seating depth effects pressure much more than diameter when using lead projectiles in small capacity cases, and whole heartedly endorse 454PB’s recommendation that you start out low and work back up when you change any of the critical parameters such as seating depth, bullet weight or powder type.

I have looked at the drawing of the projectile you mentioned on the R&C Bullet web site; I have used an identically shaped .357 projectile in my CZ and Glock 17. The only thing you might encounter, depending how deep the projectiles are seated and the dimensions of your sizing die, might be a bulge in the case at the base of the projectile.

A slight bulge is usually not a problem as long as the ammunition still feeds reliably; it is caused more by the way 9mm carbide sizing dies are made than a “one or two thou” increase in bullet diameter. I even went to the trouble of selecting a 9mm carbide sizing die (from my collection) with the longest carbide insert (Dillon if I remember correctly) and honing it until it sized the case only the required amount for correct bullet tension. The ammunition does not shoot any better, but it looks prettier; and 5000+ rounds over the past 6 months in practice and IPSC competitions without malfunction is an indication that it is not worse.

Paul
 

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Pressure with lead bullest is not a problem, unless far oversized as the hardest lead is still softer than the average jacketed, as long as properly lubed with a quality lube. With lead; lube is a necessity to prevent leading and to optimize accuracy. I shoot a 358 in both my 38 S&W short, 357 and 9mm with excellent results. I adjust the hardness for the S&W as it only needs very soft lead for it's low velocity.
 

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Several years ago, our police department had a large lot of commercially reloaded 9mm, 125-grain JHP loads that we shot through our Smith & Wesson Model 669 & 6906 autos. There was absolutely no problem and that was with a jacketed bullet, so I think you won't have any problem with lead bullet loads. By the way, we were told that these loads were intended for use in Glock 9mms because they "needed" a .357 caliber bullet for their bore size. Has anyone else ever heard of that situation with a Glock 9mm?

Steve
 

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I use alot of 9mm bullets in 38s I size cast 357 for my 9mms and 358 for the most part in 38s and have shot some extreamly good groups with them in 38s As a matter of fact my smith/clark ppc gun does its best work with bulk buy hornady hap 125 grain 9mm bullets and they are 357 diameter bullets.
 
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