Loading the 10mm Snub-nosed Revolver
Back in the early 1980s, the 10mm Auto cartridge was the brainchild of Col. Jeff Cooper, and became the original chambering of the now infamous Bren Ten. The financial woes of Dornaus & Dixon kept the Bren Ten from ever taking off commercially, but the 10mm cartridge was saved from extinction by Colt, Glock, and S&W in the late 1980s. Originally envisioned as a law enforcement/personal defense cartridge, the 10mm ended up finding a niche in the growing handgun hunting community, and in bowling pin shoots.
Originally the guns chambered in 10mm were all semi-autos (e.g. Colt Delta Elite, S&W 1006, Glock Model 20, etc.). In 1989, S&W introduced the first 10mm revolver -- the 5” Model 610 (the 5” barrel was a compromise for both hunting and bowling pin competition). Sales were poor, and the 610 was dropped in 1992. Encouraged by the steady 10mm sales of Colt and Glock throughout the ‘90s, S&W re-introduced the 610 in 1998, this time with a 6.5” barrel (aimed primarily at the handgun hunting market). In 1999, a run of 300 3” RB 610s were made for Lew Horton, and a 4” model was added in 2001. Sales continued to be modest, and the 610 was dropped from the catalog in 2005.
At first glance, one might think that tailoring handloads for the 610 would be similar to tailoring .45 ACP handloads for the 1917 revolvers due to their similarities (rimless auto cartridge, moon clips, N-frame, etc.). While there is some overlap, such reasoning misses the target much of the time. Let’s look a little closer to understand why….
Similarities – bullet profile (ogive) can aid in smooth insertion of the loaded full-moon clips. Anything with a shoulder (e.g SWC) tends to hang up and make insertion more difficult, so the advantage of built-in speed-loaders is lost. Bullets with a RN-FP and TC ogive work best.
Differences – In contrast to the Model 1917 (born of military necessity, with battlefield tolerances), tolerances on the S&W 610s are tight throughout, and this model has a long-standing, and well-deserved, reputation for being very accurate. This is mainly due to the tight chamber and throat tolerances. Carefully tailored handloads go into the cylinder .422” in diameter, fired cases come out at .424”, so I would guess that chambers run about .425”. The throats in my 3” 610 slugged consistently right at .400”. In addition, the chambers are cut with abrupt mouths (i.e. no leade going into the throat) so the cartridge can headspace off the case mouth if single-loaded (I prefer to use full-moon clips). It is important to not let crud build up in the chambers or it can negatively impact headspace (and potentially tie up the gun).
Pressure – The 10mm operates at notably higher pressures (e.g. 25-30 kpsi) than does the .45 ACP. While the .45 ACP is best served by powders Unique and faster, the 10mm is best served by powders Unique and slower. Yes, light target loads (800-900 fps) can be put together using Bullseye, Red Dot, etc. However, assembling anything resembling full-throttle loads is best reserved for slower powders – my favorites for 10mm are AA#7, HS-6, and Unique. Standard primers are preferred for these powders (but I do use magnum primers on those occasions when I load AA#9 in 10mm).
In contrast to the 1917’s fixed sights, the sights on the 610 are the usual excellent S&W adjustable target sights (RR/WO on the 3”, black on black for the 4” model).
Crimping is very important when loading 10mm ammo. First off, roll-crimping is out because there is no roll-crimp in the RCBS seater die, it’s a taper crimp die. That’s ok because none of the bullets I load in 10mm have a crimping groove or cannelure. For jacketed bullets, the recipe for happiness is to seat the bullet to the manufacturer’s recommended OAL (generally seating the shoulder even with the case mouth), and then adjusting the taper crimp die to crimp the case mouth in .001”. With such a light taper crimp, the seating and crimping steps can be performed in either one step or two. For cast bullets, seat the bullet so that the shoulder is about .010” below the case mouth, and then adjust the taper crimp to crimp the case mouth .001” (as above). This will prevent damaging the cast bullet during the seating/crimping process. Applying a longer/harder taper crimp to cast bullets can result in the case mouth “snow plowing” bullet metal from a cast bullet. This not only damages the bullet and wrecks accuracy, but the plowed up burrs of bullet metal WILL cause problems when dealing with the tight chamber tolerances like those found in the 10mm chambers. A light .001” taper crimp is all that is needed for the 10mm.
The cylinder gap runs about .006” in my 3” S&W 610.
I have heard some folks describe the 10mm as “a semi-auto .41 Magnum”. Such thinking is pure fantasy. In terms of power the 10mm falls about midway in between the .357 Magnum and the .41 Magnum. I tend to think of the 10mm as a .357 Magnum on steroids, with added bullet weight and bullet diameter. This description is not intended to denigrate the 10mm in any way. Quite the contrary, this is a very useful power level for a compact easily carried handgun. Velocities from the 3” 610 tend to run about, about 75-100 fps slower than those of the full-size 10mm handguns – again a very useful level of ballistics (and pretty much exactly what Elmer Keith and Bill Jordan were asking for in the early 1960s for a .40 caliber law enforcement revolver).
The loads discussed below are, in general, not red-line maximum loads. These are loads that I have worked up for my Colt Delta Elite, and not wanting to beat up the 1911 frame, I have kept them at somewhat below maximum level. These loads work beautifully in the 3” S&W 610.
Cast bullets
Bullet profile (ogive) is important for getting the loaded full-moon clips to slide easily into the cylinder. TC and RN-FP ogives work very well, SWCs do not feed as smoothly because of their pronounced shoulder. The S&W 610s have .400” throats, so all cast bullets were sized .400” and lubed with 50/50 beeswax/moly grease (cast bullets sized .401” were significantly less accurate).
Lee makes 175 grain TC that makes a fine plinking/practice load, and a 6-cavity mould makes casting bulk quantities easy! Sized .400”, these were seated over 7.0 grains of Unique with a light taper crimp over the shoulder. So loaded, this ammo produces about 1050 from the 3” 610 and good accuracy. Erik Ohlen (hollowpointmold.com) also offers moulds that produce a 169 grain HP version of this bullet, which produces similar velocity and accuracy with this load. Both versions make dandy varmint loads, and varminting is an excellent way to gain important practice and familiarity with a carry gun. Cast HPs make dramatic varmint loads!
Speaking of cast HPs, Miha Prevac makes some of the most beautiful bullet moulds in the world, and he makes an excellent 150 grain HP version of his 160 grain .40 caliber RN-FP. I size the MP 150 grain HP .400” and seat it to an OAL of 1.235”. When loaded over 7.5 grains of Unique this bullet generates about 1160 fps. I am looking forward to using this bullet next varmint season!
My favorite cast bullet for the 10mm is the 200 grain RN-FP from Accurate Molds. I seat these to an OAL of 1.225”, and use a light taper crimp over the shoulder. When loaded over 9.3 grains of AA#7 with a CCI 300 primer, the 3” 610 delivers about 1020 fps and excellent accuracy. This is my all-round, general purpose load when I carry the 3” 610 in the woods (speed-loader pouches make a convenient way to carry spare loaded full-moon clips).
Jacketed bullets
The TC ogive of many commercial jacketed .40 caliber bullets work very well for feeding full-moon clips into the S&W 610 cylinder. The 180 grain Hornady XTP loaded over 10.1 grains of AA#7 with a CCI 300 primer gives good accuracy and about 1050 fps. The XTPs expand very well at this velocity.
Likewise, the 200 grain Hornady XTP loaded over 9.3 grains of AA#7 also produces about 960 fps, and is the most accurate load I have found to date for my 3” 610. If forced to choose only 1 load to use in this gun, this would be that one load.
As a brief aside, since headspace is provided by the full-moon clips, the shorter (and more common) .40 S&W ammunition can also be safely fired in the S&W 610 revolvers. This is just like shooting .38 Specials in a .357 Magnum revolver. While there is no problem getting complete ejection of fired 10mm cases, the shorter .40 S&W cases eject even more quickly and easily, and might prove advantageous in some forms of competition (i.e. faster reloads). In the limited experiments I have done so far, .40 S&W ammo shoots just fine in the 610 revolvers.
The 10mm has gained a steady following, and is more popular today than ever before. Even more manufacturers are making 10mm handguns today, including 1911s by Springfield, Ruger, and Kimber -- heck Ruger even made some 10mm single-action Blackhawks! S&W didn’t make very many of the 3” 610s the first time around, but the fact remains that a 3” N-frame 10mm makes a convenient, powerful, and accurate carry gun, and when it’s loaded with full-moon clips it has it’s own built in speed-loaders as well! All in all, a superb little package.
(edited to include updated chronograph data)
Back in the early 1980s, the 10mm Auto cartridge was the brainchild of Col. Jeff Cooper, and became the original chambering of the now infamous Bren Ten. The financial woes of Dornaus & Dixon kept the Bren Ten from ever taking off commercially, but the 10mm cartridge was saved from extinction by Colt, Glock, and S&W in the late 1980s. Originally envisioned as a law enforcement/personal defense cartridge, the 10mm ended up finding a niche in the growing handgun hunting community, and in bowling pin shoots.
Originally the guns chambered in 10mm were all semi-autos (e.g. Colt Delta Elite, S&W 1006, Glock Model 20, etc.). In 1989, S&W introduced the first 10mm revolver -- the 5” Model 610 (the 5” barrel was a compromise for both hunting and bowling pin competition). Sales were poor, and the 610 was dropped in 1992. Encouraged by the steady 10mm sales of Colt and Glock throughout the ‘90s, S&W re-introduced the 610 in 1998, this time with a 6.5” barrel (aimed primarily at the handgun hunting market). In 1999, a run of 300 3” RB 610s were made for Lew Horton, and a 4” model was added in 2001. Sales continued to be modest, and the 610 was dropped from the catalog in 2005.
At first glance, one might think that tailoring handloads for the 610 would be similar to tailoring .45 ACP handloads for the 1917 revolvers due to their similarities (rimless auto cartridge, moon clips, N-frame, etc.). While there is some overlap, such reasoning misses the target much of the time. Let’s look a little closer to understand why….
Similarities – bullet profile (ogive) can aid in smooth insertion of the loaded full-moon clips. Anything with a shoulder (e.g SWC) tends to hang up and make insertion more difficult, so the advantage of built-in speed-loaders is lost. Bullets with a RN-FP and TC ogive work best.
Differences – In contrast to the Model 1917 (born of military necessity, with battlefield tolerances), tolerances on the S&W 610s are tight throughout, and this model has a long-standing, and well-deserved, reputation for being very accurate. This is mainly due to the tight chamber and throat tolerances. Carefully tailored handloads go into the cylinder .422” in diameter, fired cases come out at .424”, so I would guess that chambers run about .425”. The throats in my 3” 610 slugged consistently right at .400”. In addition, the chambers are cut with abrupt mouths (i.e. no leade going into the throat) so the cartridge can headspace off the case mouth if single-loaded (I prefer to use full-moon clips). It is important to not let crud build up in the chambers or it can negatively impact headspace (and potentially tie up the gun).
Pressure – The 10mm operates at notably higher pressures (e.g. 25-30 kpsi) than does the .45 ACP. While the .45 ACP is best served by powders Unique and faster, the 10mm is best served by powders Unique and slower. Yes, light target loads (800-900 fps) can be put together using Bullseye, Red Dot, etc. However, assembling anything resembling full-throttle loads is best reserved for slower powders – my favorites for 10mm are AA#7, HS-6, and Unique. Standard primers are preferred for these powders (but I do use magnum primers on those occasions when I load AA#9 in 10mm).
In contrast to the 1917’s fixed sights, the sights on the 610 are the usual excellent S&W adjustable target sights (RR/WO on the 3”, black on black for the 4” model).
Crimping is very important when loading 10mm ammo. First off, roll-crimping is out because there is no roll-crimp in the RCBS seater die, it’s a taper crimp die. That’s ok because none of the bullets I load in 10mm have a crimping groove or cannelure. For jacketed bullets, the recipe for happiness is to seat the bullet to the manufacturer’s recommended OAL (generally seating the shoulder even with the case mouth), and then adjusting the taper crimp die to crimp the case mouth in .001”. With such a light taper crimp, the seating and crimping steps can be performed in either one step or two. For cast bullets, seat the bullet so that the shoulder is about .010” below the case mouth, and then adjust the taper crimp to crimp the case mouth .001” (as above). This will prevent damaging the cast bullet during the seating/crimping process. Applying a longer/harder taper crimp to cast bullets can result in the case mouth “snow plowing” bullet metal from a cast bullet. This not only damages the bullet and wrecks accuracy, but the plowed up burrs of bullet metal WILL cause problems when dealing with the tight chamber tolerances like those found in the 10mm chambers. A light .001” taper crimp is all that is needed for the 10mm.
The cylinder gap runs about .006” in my 3” S&W 610.
I have heard some folks describe the 10mm as “a semi-auto .41 Magnum”. Such thinking is pure fantasy. In terms of power the 10mm falls about midway in between the .357 Magnum and the .41 Magnum. I tend to think of the 10mm as a .357 Magnum on steroids, with added bullet weight and bullet diameter. This description is not intended to denigrate the 10mm in any way. Quite the contrary, this is a very useful power level for a compact easily carried handgun. Velocities from the 3” 610 tend to run about, about 75-100 fps slower than those of the full-size 10mm handguns – again a very useful level of ballistics (and pretty much exactly what Elmer Keith and Bill Jordan were asking for in the early 1960s for a .40 caliber law enforcement revolver).
The loads discussed below are, in general, not red-line maximum loads. These are loads that I have worked up for my Colt Delta Elite, and not wanting to beat up the 1911 frame, I have kept them at somewhat below maximum level. These loads work beautifully in the 3” S&W 610.
Cast bullets
Bullet profile (ogive) is important for getting the loaded full-moon clips to slide easily into the cylinder. TC and RN-FP ogives work very well, SWCs do not feed as smoothly because of their pronounced shoulder. The S&W 610s have .400” throats, so all cast bullets were sized .400” and lubed with 50/50 beeswax/moly grease (cast bullets sized .401” were significantly less accurate).
Lee makes 175 grain TC that makes a fine plinking/practice load, and a 6-cavity mould makes casting bulk quantities easy! Sized .400”, these were seated over 7.0 grains of Unique with a light taper crimp over the shoulder. So loaded, this ammo produces about 1050 from the 3” 610 and good accuracy. Erik Ohlen (hollowpointmold.com) also offers moulds that produce a 169 grain HP version of this bullet, which produces similar velocity and accuracy with this load. Both versions make dandy varmint loads, and varminting is an excellent way to gain important practice and familiarity with a carry gun. Cast HPs make dramatic varmint loads!
Speaking of cast HPs, Miha Prevac makes some of the most beautiful bullet moulds in the world, and he makes an excellent 150 grain HP version of his 160 grain .40 caliber RN-FP. I size the MP 150 grain HP .400” and seat it to an OAL of 1.235”. When loaded over 7.5 grains of Unique this bullet generates about 1160 fps. I am looking forward to using this bullet next varmint season!
My favorite cast bullet for the 10mm is the 200 grain RN-FP from Accurate Molds. I seat these to an OAL of 1.225”, and use a light taper crimp over the shoulder. When loaded over 9.3 grains of AA#7 with a CCI 300 primer, the 3” 610 delivers about 1020 fps and excellent accuracy. This is my all-round, general purpose load when I carry the 3” 610 in the woods (speed-loader pouches make a convenient way to carry spare loaded full-moon clips).
Jacketed bullets
The TC ogive of many commercial jacketed .40 caliber bullets work very well for feeding full-moon clips into the S&W 610 cylinder. The 180 grain Hornady XTP loaded over 10.1 grains of AA#7 with a CCI 300 primer gives good accuracy and about 1050 fps. The XTPs expand very well at this velocity.
Likewise, the 200 grain Hornady XTP loaded over 9.3 grains of AA#7 also produces about 960 fps, and is the most accurate load I have found to date for my 3” 610. If forced to choose only 1 load to use in this gun, this would be that one load.
As a brief aside, since headspace is provided by the full-moon clips, the shorter (and more common) .40 S&W ammunition can also be safely fired in the S&W 610 revolvers. This is just like shooting .38 Specials in a .357 Magnum revolver. While there is no problem getting complete ejection of fired 10mm cases, the shorter .40 S&W cases eject even more quickly and easily, and might prove advantageous in some forms of competition (i.e. faster reloads). In the limited experiments I have done so far, .40 S&W ammo shoots just fine in the 610 revolvers.
The 10mm has gained a steady following, and is more popular today than ever before. Even more manufacturers are making 10mm handguns today, including 1911s by Springfield, Ruger, and Kimber -- heck Ruger even made some 10mm single-action Blackhawks! S&W didn’t make very many of the 3” 610s the first time around, but the fact remains that a 3” N-frame 10mm makes a convenient, powerful, and accurate carry gun, and when it’s loaded with full-moon clips it has it’s own built in speed-loaders as well! All in all, a superb little package.
(edited to include updated chronograph data)
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