.455 converted to .45 Question

[andorra]

I have a .455 S&W made 1916 converted to .45 Auto Rim. Marked .45 AR. Everything I read says do not use .45 ACP ammo, pressure is too high. According to SAMMI the max for .45 ACP is 21, 000 psi. The max for .45 AR is 16.000 psi. The 2 have the same case capacity, shoot the same weight bullet at the same velocity. Looking in reloading manuals, the same powder charges gives the same velocity for both cartridges.

If both cartridges shoot a 230 gr bullet at about 850 fps, from the same size case, how can one be safe and other not.

 

[huthike]

Interesting question. Perhaps the 45 AR case is stronger at the web partially because of the rim addition?

Also, your gun may be altered to 45 Colt - drop one in and see if it fits.

 

[andorra]

It is converted to .45 Auto Rim. I have been shooting it with reduced loads in .45 ACP cases and moon clips. Every source I checked says these .455 to .45 conversions are unsafe with factory .45 ACP ammo, but safe with .45 Auto Rim ammo.

 

[Muley Gil]

I have a .455 S&W made 1916 converted to .45 Auto Rim. Marked .45 AR. Everything I read says do not use .45 ACP ammo, pressure is too high. According to SAMMI the max for .45 ACP is 21, 000 psi. The max for .45 AR is 16.000 psi. The 2 have the same case capacity, shoot the same weight bullet at the same velocity. Looking in reloading manuals, the same powder charges gives the same velocity for both cartridges.

If both cartridges shoot a 230 gr bullet at about 850 fps, from the same size case, how can one be safe and other not.

Most factory .45 Auto Rim cartridges were/are loaded with lead bullets. Lead bullets generally produce less pressure than jacketed bullets.

 

[willy]

The 455 to 45acp warnings started with the Webley revolvers, S&W didn’t make weaker guns just for the 455 Webley round,, The 1917 revolvers are good to go with factory 45acp ammo,

 

[Muley Gil]

The 455 to 45acp warnings started with the Webley revolvers, S&W didn’t make weaker guns just for the 455 Webley round,, The 1917 revolvers are good to go with factory 45acp ammo,

The S&W 1917s received heat treating per the US Government specifications.

 

[andorra]

Most factory .45 Auto Rim cartridges were/are loaded with lead bullets. Lead bullets generally produce less pressure than jacketed bullets.

The loading manuals show loads for the 45 Auto Rim with jacketed bullets with the same velocity as the 45 ACP with the same powders.

 

[StrawHat]

The 455 to 45acp warnings started with the Webley revolvers, S&W didn’t make weaker guns just for the 455 Webley round,, The 1917 revolvers are good to go with factory 45acp ammo,

As mentioned by Muley Gil, the Model 1917 had heat treated cylinders at the insistence of the Army. They were the first revolvers to be heat treated at the factory. None of the other Models received any heat treatment until after the war. Even then, it was not applied to all models.

Kevin

 

[glowe]

Pressures generated are affected by several things. As for the 45 Colt vs the 45 ACP, the volume of the case is quite different. There is more air space in the 45 Colt, perhaps yielding more oxygen to change the ignition rate of the powder. The 45 Colt has 30% larger capacity than the 45 ACP.

 

[murphydog]

I would say you need to know what load you use and its specifications, instead of relying on its name. As you know, there is .45 ACP in target loads (185 gr SWC as I recall), and a few makers produce .45 AR at full + P pressures, which personally I would not use in a .455 conversion or even a 1917 Army.

 

[Muley Gil]

The loading manuals show loads for the 45 Auto Rim with jacketed bullets with the same velocity as the 45 ACP with the same powders.

Many reloading manuals use the 1955 S&W revolver chambered in .45 ACP for their test model. These revolvers, and the ones built since 1955, are stronger than the WW I .455s that have been converted to .45 ACP.

Just because a cartridge fits in the chamber, that doesn't mean it SHOULD be fired in that particular firearm.

Better safe than sorry when dealing with arms that are over 100 years old.

 

[andorra]

The question is, if the 45 ACP and 45 Auto Rim both have the exact same case capacity, and shoot the same weight bullet at the same velocity, why is one safe to shoot in these converted guns and the other not safe.

 

[Piwo]

My .455 conversion S&W is marked "45AR" on the barrel, as were many. I've never seen one marked "45 ACP." An issue that arises with 230 gr. bullets is that they usually print well below the POA of these old guns. I use only 45AR brass in mine, loaded to the starting level. The data from an older RCBS book and for 250 grain bullets. That book also states 45 AR loads are loaded to a lower pressure Than 45 ACP/ It about duplicates what the original Webley load did. The bullets hit to the point of aim, are gentle on the gun and do anything I should be doing with a 105 year old gun. These guns were never heat treated. Maybe because until 1917 no revolver cartridge was loaded hot enough to warrant it.

 

[glowe]

The question is, if the 45 ACP and 45 Auto Rim both have the exact same case capacity, and shoot the same weight bullet at the same velocity, why is one safe to shoot in these converted guns and the other not safe.

Sorry, got the wrong caliber comparison. The notes I have collected on 45 ACP and 45 AR are below:

Many reloaders have used standard 45 ACP data in 45 Auto Rim for years. The Auto Rim was developed simply to allow shooting a 45 ACP revolver without the hassle of moon clips (at least some people apparently did). Other than the thicker rim on the Auto Rim the cases are identical, as far as case capacity. If you're using a modern gun in good condition, they can be loaded to the same pressures, thus they can use the same data.

The Auto Rim was developed because some people didn't like half-moon clips, in addition there was a war on, and AR ammo meant it works in revolvers when you can't get the clips. If you look at the loading data, some of it is different. That's because it was developed in different guns, semi-autos and/or revolvers. While any standard load is essentially interchangeable, allowances must be made for individual guns. 45AR was intended for use in the S&W and Colt 1917 revolvers, some other guns that have been set up for .45acp and clips may not work with Auto Rim brass. Most will, but not all.

The bottom line for me is to load to velocity. I have generated 45ACP loads that produce 750 fps using starting loads 20% lower than those found in reloading manuals. Using a 200 grain lead bullet, felt recoil is low and velocities are plenty fast enough to give accuracy. Other than that, it appears that "standard" loadings in commercially available ammo have been used in these guns for decades without documented damage, but I still stick with my soft reloads for my converted 455.

 

[Hondo44]

The question is, if the 45 ACP and 45 Auto Rim both have the exact same case capacity, and shoot the same weight bullet at the same velocity, why is one safe to shoot in these converted guns and the other not safe.

Pressure ratings are for standard factory loadings. And as you found .45 AR is only factory loaded to 16,000 PSI; the full case capacity is not utilized. Therefore purposely loaded down from the standard ACP 21,000 PSI loading. That's why factory 45 AR ammo is safe in a 455 converted revolver.

But yes, of course AR can be loaded to the same pressure levels as the ACP.

So only use factory AR ammo and/or only reload them to a factory duplication load to be safe in your gun.

 

[andorra]

"So only use factory AR ammo and/or only reload them to a factory duplication load to be safe in your gun."

The point is, the 45 ACP and the 45 AR have the exact same ballistics. 230 gr at 830 fps. A factory duplication load of the 45 AR is exactly the same ballistics as a factory 45 ACP. 230 gr at 830 fps.

 

[Muley Gil]

"So only use factory AR ammo and/or only reload them to a factory duplication load to be safe in your gun."

The point is, the 45 ACP and the 45 AR have the exact same ballistics. 230 gr at 830 fps. A factory duplication load of the 45 AR is exactly the same ballistics as a factory 45 ACP. 230 gr at 830 fps.

The factory .45 Auto Rim round is loaded with a soft lead bullet; the factory .45 ACP round is loaded with a jacketed bullet.

Lead bullets develop less friction than jacketed bullets. Pressure is higher in the ACP.

 

[andorra]

The factory .45 Auto Rim round is loaded with a soft lead bullet; the factory .45 ACP round is loaded with a jacketed bullet.

Lead bullets develop less friction than jacketed bullets. Pressure is higher in the ACP.

Not true. Checking the Lyman reloading manual, which lists pressures, a .45 230 grain bullet at 850 fps has the same pressure whether the bullet is lead or jacketed.

The jacketed bullet uses slightly more of the same powder to achieve the same velocity, but that does not create more pressure.

A .45 230 grain bullet at 850 fps has the same pressure whether lead or jacketed.

Same for other calibers. A 32-20 115 grain bullet at 1300 fps has the same pressure whether the bullet is jacketed or lead.

 

[steelslaver]

The gun is already modified. Simply fit a 45 acp cylinder in it quit worrying and shoot acp or AR. It is the cylinder that limits the pressure NOT the frame.

 

[andorra]

The gun is already modified. Simply fit a 45 acp cylinder in it quit worrying and shoot acp or AR. It is the cylinder that limits the pressure NOT the frame.

Obtaining and fitting a new cylinder really is not that simple. I like the fact that the cylinder, although shaved, is the original cylinder. The cylinder is not that modified, just slightly shaved at the rear.

I shoot light 45 ACP loads, not a problem. This pressure question is one that no one has been able answer for me over the years.