[bowzette]

My understanding is the 9mm doesn't group as well as 357/38 due to case/bullet length and smaller diameter of the 9mm. What size groups are you getting from the 9mm compared to the .38 at 25 yards? I realize this will vary with the revolver, the shooter and good days v bad days. I just kill paper, metal targets and tin cans. But only "accurate guns are interesting" and there is no point to me in paying for the 9mm cylinder if it doesn't group decently.

 

[rmichael63]

i get pretty good groups with my P-95 (9mm) I don't have a 38/357 to compare it to though ...

 

[Radco]

Are you asking about shooting 9mm in a .357 revolver? or a difference between a 9mm revolver and a .357 revolver ? I know the 9mm and .357 are real close in size. Just curious Thanks

 

[Magnum cum loude]

My understanding is the 9mm doesn't group as well as 357/38 due to case/bullet length and smaller diameter of the 9mm. What size groups are you getting from the 9mm compared to the .38 at 25 yards? I realize this will vary with the revolver, the shooter and good days v bad days. I just kill paper, metal targets and tin cans. But only "accurate guns are interesting" and there is no point to me in paying for the 9mm cylinder if it doesn't group decently.

As long as the projectile is obturating properly in the barrel, it leaves the muzzle with the correct diameter.

Revolvers obturate or resize twice, once in the chamber throat and again in the barrel.

This is for lead projectiles see correction below"Magnum cum loude, It takes in excess of 45k psi for a jacketed bullet to obturate so what you said only applies to lead bullets."

 

[fboyj]

I have a 6 inch Blackhawk convertible in 357/38/9mm and it is very accurate. On a man size target I was trying for pelvic hits at 25 yards and group size was approx 2.5 inches. These Blackhawks are very accurate and with the ability to fire 3 different types of cartridges it's flexibility is outstanding.

 

[bowzette]

I have a 6 inch Blackhawk convertible in 357/38/9mm and it is very accurate. On a man size target I was trying for pelvic hits at 25 yards and group size was approx 2.5 inches. These Blackhawks are very accurate and with the ability to fire 3 different types of cartridges it's flexibility is outstanding.

Thanks this is the information I was seeking. My question may not have been clear. No point in buying a 9mm cylinder-convertible model- if it will not shoot accurately.

 

[Iowegan]

Magnum cum loude, It takes in excess of 45k psi for a jacketed bullet to obturate so what you said only applies to lead bullets.

bowzette, I've bench test fired several Ruger Blackhawk convertibles (including my own 4 5/8" BH) and found 38 Special ammo with 148gr lead HBWC bullets are the most accurate ... sub-inch groups at 25 yards. Full power 357 Mags with 140gr jacketed bullets come in a close second (1" groups @ 25 yds) and jacketed 9mm 115 or 125gr rate a distant third place (2~2.5" groups @ 25 yds). Further, when chronographing 9mm ammo in my CZ-75b (4 3/4" barrel), in theory it should be very close to my 4 5/8" Blackhawk .... but it isn't. I lose about 100 fps with the Blackhawk when shooting exactly the same ammo.

Is this a deal breaker? No, it just means the 9mm is not quite as accurate in a Blackhawk. If you have much experience, you will find very few 9mm pistols will group much tighter than a Blackhawk so you're really not losing much ... just 10% of your velocity. The advantage is .... 9mm ammo is much cheaper and is plenty accurate for anything but bullseye competition. That said, I reload and find the cost to load 9mm versus 38 Specials is pretty much a dead heat .... so my 9mm cylinder just gets lonesome sitting in the little red bag.

 

[Magnum cum loude]

"Magnum cum loude, It takes in excess of 45k psi for a jacketed bullet to obturate so what you said only applies to lead bullets.
"

I didn't know that before. Thanks, I corrected my post to reflect your correction. Obviously
my experience was with handcast.

 

[bowzette]

Thanks Iowegan. I would shoot .38 most of the time but the cost of 9mm is appealing. I'm not reloading at this point.

 

[Magnum cum loude]

"Magnum cum loude, It takes in excess of 45k psi for a jacketed bullet to obturate so what you said only applies to lead bullets.
"

I didn't know that before. Thanks, I corrected my post to reflect your correction. Obviously
my experience was with handcast.

Now that I've checked SAAMI drawings, 9mm Luger, .38 Special and .357 Magnum barrels are all listed as the same 6 grooves, .355" groove and .346" bore.

shouldn't a .355 diameter (9X19mm size) jacked projectile fully obturate?

I'm asking not arguing here.

 

[Iowegan]

Magnum cum loude, Some people load lead bullets in their 9mm ammo ... I don't. All my 9mm ammo gets jacketed bullets and there's a good reason. When I grab a box of ammo, I want it to work equally well in any of my guns chambered for that cartridge and I don't "tune" handgun ammo for a specific gun. When the German Luger was first designed, it had a 1:10 twist rate specifically for jacketed bullets so that became the standard twist rate for nearly all other brands of 9mm pistols. Lead bullets don't play well in a fast twist bore ... almost always resulting in excessive bore fouling. You can get by with lead bullets in a Blackhawk because they have a slow twist rate of 1:18.75 ... almost half that of a 9mm pistol. So ... if you use lead bullets in a 9mm Blackhawk, you may be able to get accuracy almost as good as a 38 Special. The bore in a Blackhawk is rated at .357" +or- .0005", however the cylinder chambers are tight enough where a .356" lead bullet is the max diameter that will fit without having to drive cartridges in with a hammer. As such, 9mm bullets don't seal as tight in the bore, thus a loss of pressure and velocity, plus a reduction in accuracy. If you happen to get a Blackhawk with a bore at the tighter end of the spectrum, it may shoot 9mm ammo quite well, however I have tested several dozen and never found this to be true.

Obturation is a function of chamber pressure versus bullet hardness (rated in Brinell Hardness Number or BHN). The formula is BHN = chamber pressure (in psi) divided by 1400 ... or ... Chamber pressure = BHN times 1400. Typical 9mm jacketed bullets are rated at BHN 32 so to get them to obturate, pressure must be (32 x 1400=44,800 psi) about 45k psi. Hard cast lead bullets are typically rated at BHN 20, which is just about right for a 9mm cartridge with a chamber pressure of 28k psi.

 

[Magnum cum loude]

"Magnum cum loude, Some people load lead bullets in their 9mm ammo ... I don't."

From the mid 1960's I reloaded my sporting rounds using lead projectiles for speeds below 1000 f.p.s., and jacketed or gas-checked for supersonic rounds.

 

[SafetyJoe]

If the cylinder chambers in the blackhawk are .356 and the bore is 357 maybe it's a good idea to open up those cylinder chambers a little so you can load some over sized 9mm hard cast bullets. Maybe a reamer would be too much, but valve lapping compound or some 2000 grit wet/dry sand paper should work. I load over sized 9mm in my pistols. I just have to use 38 special expanding and taper crimp dies instead of the 9mm ones.

 

[Iowegan]

SafetyJoe, There are several options for shooting 9mms in a Blackhawk. For me, the simplest solution is to use the standard cylinder and shoot 38 Specials. I don't think it is worth my time to develop a lead bullet 9mm load and certainly isn't worth the effort to modify my 9mm cylinder. Different strokes for different folks.

 

[SafetyJoe]

SafetyJoe, There are several options for shooting 9mms in a Blackhawk. For me, the simplest solution is to use the standard cylinder and shoot 38 Specials. I don't think it is worth my time to develop a lead bullet 9mm load and certainly isn't worth the effort to modify my 9mm cylinder. Different strokes for different folks.

Yeah, if you're not into lead 9mm then there's no point in widening the cylinder chamber. I have good results in lone wolf glock barrels because the twist rate is 1:16
I also have a GP100 that I use self made lead bullets in, but the 9mm brass cases are 100 times easier to find on the ground at my local shooting range than 38/357 brass. That's why even though it costs me 5 cents per shot for lead 9mm or 38 special the free brass availability factor plays a big role for me.

 

[Magnum cum loude]

If the cylinder chambers in the blackhawk are .356 and the bore is 357 maybe it's a good idea to open up those cylinder chambers a little so you can load some over sized 9mm hard cast bullets. Maybe a reamer would be too much, but valve lapping compound or some 2000 grit wet/dry sand paper should work. I load over sized 9mm in my pistols. I just have to use 38 special expanding and taper crimp dies instead of the 9mm ones.

"If the cylinder chambers in the blackhawk are .356 and the bore is 357 maybe it's a good idea to open up those cylinder chambers a little so you can load some over sized 9mm hard cast bullets"

I wouldn't jump to conclusions quite yet. There seems to be some confusion concerning terminology, "cylinder chamber" is one thing, the "cylinder throat" is another thing.

Some of my Ruger convertible cylinders came in with very tight throats, but the chambers were normal. These were dealt with simply by reaming. Made an instant change in accuracy with cast bullets especially. When asked if Ruger was interested in reaming them for a fee, they replied that no they would not "custom make a cylinder for a handloader, that the cylinder was designed to fire a large range of commercial cartridges". Ironically the next new Blackhawk convertible one I bought was perfect.

Those convertible cylinders that also fire an ACP headspace off the front rim of the case (no moon clips needed), while their rimmed counterparts headspace off the rim.

Meanwhile I've sent an inquiry to Ruger asking about their design specs for the Blackhawk .357 barrel.

To answer the original poster's question I say yes indeed get the spare cylinder at this time. They won't sell you just the cylinder later, as the gun must be originally registered as a convertible.

 

[SafetyJoe]

"If the cylinder chambers in the blackhawk are .356 and the bore is 357 maybe it's a good idea to open up those cylinder chambers a little so you can load some over sized 9mm hard cast bullets"

I wouldn't jump to conclusions quite yet. There seems to be some confusion concerning terminology, "cylinder chamber" is one thing, the "cylinder throat" is another thing.

Some of my Ruger convertible cylinders came in with very tight throats, but the chambers were normal. These were dealt with simply by reaming. Made an instant change in accuracy with cast bullets especially. When asked if Ruger was interested in reaming them for a fee, they replied that no they would not "custom make a cylinder for a handloader, that the cylinder was designed to fire a large range of commercial cartridges". Ironically the next new Blackhawk convertible one I bought was perfect.

Those convertible cylinders that also fire an ACP headspace off the front rim of the case (no moon clips needed), while their rimmed counterparts headspace off the rim.

Meanwhile I've sent an inquiry to Ruger asking about their design specs for the Blackhawk .357 barrel.

To answer the original poster's question I say yes indeed get the spare cylinder at this time. They won't sell you just the cylinder later, as the gun must be originally registered as a convertible.

Yeah, I was talking about the chamber throat at the front of the cylinder.

 

[North country gal]

To answer the OP's question, we recently added a 357/9mm Flat Top to the collection and our results reflect what others have posted on the question. Happy to report that we get outstanding, sub inch accuracy at 25 yards with several brands of factory 357 and do almost as well with some 38s. 9mm accuracy is well off the mark at two to two and half inches with jacketed 9mm factory stuff.

Now, there is nothing wrong with that kind of 9mm accuracy for a lot of applications, especially for the sake of cheap shooting. We did not, however, buy the gun for its 9mm capability. That was just icing on the cake.

 

[bowzette]

Thanks for the comments.

 

[P89DC]

Best reason to buy a convertible 357/9mm is that you can get at least $150 for the cylinder, lowering the procurement cost significantly. If you decide later you want a replacement cylinder (can't imagine why) Ruger will replace it for ~$200. 38spl ammo is cheap enough that I don't want to waste time shooting less accurate 9mm ammo.