I've seen references here & there about the capacity similarities, & differences, of these three cases, but these have always just been more hearsay, & not from a published source. Also, since I have a Mdl. 1911 setup to handle 45 Super loads & new 45ACP S&W "N" frame revolver, I also wondered about how the strength of the Super & Auto Rim's compared in my Starline cases. 45 Super data & hot 45 AR load data is not very extensive, especially when it comes to powder & bullet manufacturer's load manuals & I wanted to be able to use what data I have in one another, but again wondered about the capacities & if that should be a factor.

I decided to send an email to Starline & asked how the internal case capacities compare between these three. They said the capacities vary quit a bit from lot to lot but they're all around 26grs. of water. Not exactly the detail I hoped for. I replied, reiterating my original question & additionally asked how their case strengths compare. Again, an answer without much detail or specifics. Starline's website states that their 45 Colt cases are "tested to 44 Magnum pressures" (which I've loaded mine to in my Ruger SRH 454 Casull) & that their 45 AR cases are built with the "same integrity" as their 45 Colt cases, which led me to check for myself and see if a ".45AR Super" was doable.

Whenever I need new cases my first choice is Starline because they have the best availability, strength & pricing, which is what I used for this comparison, and I had all brand new cases of each. I've never checked the water capacity of a case before but I decided on using a same dab of plumber's putty in the primer pocket & pushing it in until it filled the flash hole completely. I sat the empty case on my electronic powder scale & zeroed it out, then added water with a dropper until it was to the top. I tried to be as consistent with each as I could & checked a couple of each type. The surface tension of the water causes it to dome up above the rim noticeably, long before it'll overflow, so I only added to a point that represented a full case, not an overfull one. I came up with the following: 45ACP @ 27.3 grs., 45AR @ 27.4grs., & 45 Super @ 26.8grs. So the ACP & AR are essentially the same & the Super case has about 0.5grs., or 2% less capacity.

I already had 185gr. & 200gr. JHP Super loads established for my 1911 (got the data from "Project 45 Super", at RealGuns) & knew they shot fine in my revolver using moon clips & S-L Super brass. Since the S-L AR brass actually has a little more capacity than the S-L Super brass I was comfortable working up, from an ACP +P powder level to the same Super powder level, using all the same components (Hornady XTP JHP .451" bullets with heavy taper crimp, CCI 300 primers, & Power Pistol powder carefully weighed individually) as used in the Super brass. The only other difference was the cartridge OAL. Since my revolver's chambers don't have the same restriction as my 1911's chamber does (the cartridges for my 1911 have max. OAL of 1.200" with these bullets because of the short freebore/leade before the bullet ogive hits the rifling) I seated the bullets in the AR loads out to 1.255" OAL. I worked up to my established Super maximum with no problems. The higher velocity, light weight bullets have a lower point of impact than anything else normally shot, but that's to be expected. The full house Super loads, using Power Pistol, sure gives a nice "light display" out of my short barrel. I like!! I plan on loading a box or two & only use these when the "urge" hits (& shoot my .454 when I wanna really get a thrill), but these are serious loads from a 45ACP form & widen the range of this fun cartridge in a revolver.

This info may exist elsewhere, but I haven't run across it in all my searches for 45 Super or Auto Rim articles. I thought I'd post this in case someone else was interested in it too & can find it helpful. Of course your situation/equipment may differ from mine so approach any changes for you cautiously & only use these in modern large frame revolvers in good condition. You know the disclaimer.

If you want to show your data in volumetric units I found this formula in one of my old manuals:

TO DETERMINE CASE CAPACITY

1) Determine weight in grains of water the case will hold.

2) Divide (1) above by 252.78 to obtain the capacity in cubic inches.

3) Divide (1) above by 15.43 to obtain the capacity in cubic centimeters.

So 45ACP @ 27.3 gr = 1.77cc, etc...

Interesting post! I've long wondered how far the S&W 625 could be pushed. I've tried some plus-P loads in 45AR using Power Pistol, they were stout but safe and I decided to quit there. I'd be interested in seeing some chrony data with your load info, if you have that capability.

Some folks avoid Power Pistol because of the pyrotechnics, but I like it! I've long been a fan of Power Pistol in the 40S&W, this is my standard load on an overcast day. Smile and wait for the flash!

I have been running 45SUPER through 625s for well over a decade.

Bluedot37, you do not mention if that N-frame is stainless or carbon

Power Pistol is a favorite of mine as well. For those that do not know, PP is Bullseye with a different
cut to alter the burn rate.

Wish I had a chrony, but not yet. I've been loading my 185 JHPs with 11.3grs. of P-P. These are supposed to be about 1400fps, which is 804ME, out of a 5" 1911. That seems a bit high comparing it to the scant related data out there? But that is a lot of powder. No idea what they'd be in a revolver. I got started using P-P for the Super & then started using it to load +Ps in my sons' 40S&W & 9mm Luger, which they really like. Yeh, I like a good muzzle flash too (don't blink or you miss the show!). Nice photo!!

Not really either, it's a 325NG.


Humm, didn't know that. Someone once referred to it as "magical fairy dust". Whatever's in it, I'm impressed! I wish there was more data out there for it.

Plenty of PP data here:
Alliant Powder - Reloader's Guide

Super brass is definitely a good thing for the autos but I have not seen a need for it in my 625s. I refuse to chamfer the chambers of any of my three 625s and they all handle some pretty stiff loads with ACP brass, Power Pistol and heavy cast bullets. I get 931 FPS with a 255 gr. SWC out of the 3" barrel . I'm not sure how it compares to actual Super ballistics but my load is quite a handful when shooting DA and I'm quite happy with that velocity.

I also do a lot of shooting with the Glock 21 and I have three different barrels to use and compare. The Gen 1, Gen 3 and Bar-Sto barrels are all different in regard to case head support and how long the bullets can be loaded. Keeping track of all this is a real headache and I don't bother with the heavy stuff in my Glocks.

Dave Sinko

I saw, but I need MORE. I want receipes for everything! I like it so much I wanna substitute it for pepper in my gravy; I wanna use it for sprinkles on my donuts, heck it like it so much I'm thinking about changing my name to PowerPistol37 !! Just messin' around...thanks for the link.