.45 Colt Chamber Pressure for Model 25

[AJ]

Had a friend tell me one time, when I was shooting hot magnum loads in my M29-2 4 inch. He said "You have a Ruger Super Blackhawk and the M29-2. So why shoot hot/magnum loads in a Cadillac when you have a Chevy to beat up?" After I thought about it, I started shooting .44 Specials in the 29 and hot stuff in the Ruger. The same thinking sort of applies to the .45 Colt. JMHO is all.

 

[steelslaver]

Go fire a 45acp +P load in a model 25-2 (230gr) then go fire a factory 240 gr 44mag in a 29. The 44 will beat your hand up worse than the 45, what in the world makes you think the gun isn't effected by those very same forces????? Now explain to me why you think the model 25s will be beat up by 23000 psi loads and a 29 will last longer with factory 36,000 psi loads. Same thing for for my 260gr 23000 psi loads.

A 240gr 44 at 1,400 fps has 1044ftlb of energy, at the muzzle and ON THE FRAME (at 1300fps it is still 901ftlb)

A 260gr 45 at 1,100fps has 698ftlb of energy, at the muzzle and ON the FRAME (at 1200fps it is 831ftlb)

A 45 260gr 45 colt at 1,100ftps is slamming its frame with just 3/4 of the forces a 1300fps 240gr 44 mag slams its frame.

THINK ABOUT IT

Trajectory A 44 mag 240 gr at 1300 with a 25 yard zero will be 7" low at 100

a 45 COLT 260 at 1100fps will drop right at 10"

Beyond that they are both rainbows where range calculation and knowledge of your guns ballistics are far more of the major factor than which has the most drop.

I need to take my machine rest to the range along with a 629 and a model 25 with the same barrel lengths. I am willing to bet the 44mag with factory loads ends up with the muzzle considerably higher from recoil. than the 45 colt with my 23000psi loads. That is a true measure of how much energy is transmitted to the frame. Same spring loaded clutch and the same grip adapter all being being rotated by the forces transmitted to the frames.

I personally don't worry about the frames as much as the cylinders. The cylinder always lets go first in a KABOOM. But a 25-2 45 acp is rated for +P pressures. A 45 colt cylinder has the exact same wall thickness at the rear of cylinder, just a longer chamber and the same stop notch in the same spot. Why would anyone believe one is fine with 23,000 psi loads and the other one is a ticking bomb???? I have even explained it to an engineer, who works with pressure vessels, tubing and piping and he assures me I am correct in believing what one will take the other will.

 

[jem102]

So, the question remains; is an N frame always an N frame... Some say yes and some say no. I could imagine Model 24's and Model 25's with no heat treatment but not a "separate specification" and heat treat line from 27, 29 and 57 frames. The .45 Colt case has a slightly larger case body diameter which will produce more back thrust on the recoil shield to induce frame stretch at the same pressure level as incurred in the smaller diameter case. That coupled with the decrease in cylinder wall thickness would be an indicator that pressure should be lessened in the .45 Colt. These differences are marginal unless a difference, or lack thereof, in heat treatment can be documented. Meaning Model 24's and Model 25's are capable of safely containing 23,000-28,000 PSI loads and have a normal service life, whatever S&W considers that to be...

 

[Hair Trigger]

A bit hard to believe that S&W produces N frame receivers to two different hardness levels. What proof do you have of this.

None, really, but if the .45C revolver load data limits the M25 to the low end of the pressure scale, where all the N frame magnums are about twice as high, why the limitation? In theory the frame should experience less stretch with .45C than the M57 and M29, and maybe even the smaller bore M27/28. If the cylinders are also not treated, .45C revolvers should be able to handle magnum pressure loads, shouldn't they?

S&W .45 revolvers are the only non-magnum caliber/cartridges in the N-frame.
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What about the M20 through M24? Unless you're just talking about current production since 2008.

 

[steelslaver]

Case heads and back thrust. The 44 mag and the 45 colt have the exact same sized case heads. Both have a rim diameter of .514.

I have checked the hardness of a bunch of frames and they are all very close to the same.

I have made 45 colts from 629s, 1917s, Brazilians, model 28s and fired my 23000psi loads from every one of them repeatedly with no problems.

Almost every 45 colt cylinder I have was made from a model 29 or 629 cylinder. Not because I think they are any stronger, but if I ream my own I get.452 throats

 

[BB57]

Had a friend tell me one time, when I was shooting hot magnum loads in my M29-2 4 inch. He said "You have a Ruger Super Blackhawk and the M29-2. So why shoot hot/magnum loads in a Cadillac when you have a Chevy to beat up?" After I thought about it, I started shooting .44 Specials in the 29 and hot stuff in the Ruger. The same thinking sort of applies to the .45 Colt. JMHO is all.

Agreed. I don’t see the point in pushing my 625 harder than it was designed to be pushed when I have other options.

 

[jem102]

Case heads and back thrust. The 44 mag and the 45 colt have the exact same sized case heads. Both have a rim diameter of .514.

I have checked the hardness of a bunch of frames and they are all very close to the same.

I have made 45 colts from 629s, 1917s, Brazilians, model 28s and fired my 23000psi loads from every one of them repeatedly with no problems.

Almost every 45 colt cylinder I have was made from a model 29 or 629 cylinder. Not because I think they are any stronger, but if I ream my own I get.452 throats

Trying to agree with you on this however:

Rim diameter is not a factor in back thrust only head diameter has direct impact on it. The rim on the .44 Mag is .514 VS .512 for the .45 Colt = negligent impact.
Head diameter on the .45 Colt is .479-.480 VS .456-.457 for the .44 Mag for a difference of 0.023 = a 5% greater impact area on the recoil shield from the .45 Colt, a small number but notable.



By reducing the 36,000 PSI .44 Mag load by 25%, a significant number, we arrive at 27,000 PSI. "I" would consider this a safe working pressure for the Model 25 in the 5% larger head diameter .45 Colt cambering. This makes 23,000 PSI an easy all day long pressure for the Model 25.



I agree with you and others that an N frame is an N frame and an M27 cylinder is an M25 cylinder is an M29 cylinder is an M24 cylinder is an M57 cylinder as applied to loads under 30,000 PSI regardless of cylinder stop notch location.


All this is only my opinion... As I do not have the equipment to proof the metallurgy we will each have to decide for ourselves how to conduct our loading process unless someone can indeed produce documentation on the metallurgy. If that becomes available we should be able to distill this down to usable load data.


Thanks for taking the time to read along, much appreciated.

 

[TheTinMan]

I searched for “45 ACP +P chamber pressure” and this interesting post popped up:
The SEVEN Levels of 45 Colt Maximum Working Pressure | Single-Actions

 

[Model19man]

I recently got an 8-3/8” Model 25-5 and also have a 25-10. Sierra shows two sets of data for .45 Colt: 14,000 psi and 30,000 psi. They explicitly state that the higher pressure is not suitable for a S&W 25-5. However, the Model 25s have to be more robust than a SAA dont they?

Regardless of that SAAMI limits 45 Colt loading to 14,000 PSI. That is a comfortable number to use in any S&W Revolver be it a Model 29 or a Model 25. Any reloading manual will give you loads that will result in less pressure. Follow those and you won't have any problem with your Model 25.

 

[Model 15-4ever]

I've had split brass in .45 Colt after as little as three loadings at 28,000 psi in a Ruger Blackhawk. This was with nickel-plated brass which work hardens sooner that non-plated. Plain brass I got five loadings at that level with no splits.

High power (28,000 psi) .45 Colt loadings are are effective in the proper revolver. Split brass after numerous loadings does not bother me in the least; brass is relatively cheap considering the small amount of these loads fired. I now only use new or once-fired brass for these loads, and after that they get 14,000 psi paper target loads.

 

[steelslaver]

Going with jems102 fact that it is case head not rim dia that effects the frame impact. The 44 mag is actually 10% smaller. In thinking about it the dia of the rim simply spreads it out not change it

Area of 45 colt case head .181sqin (.480/2)²x3.14
Area of 44 mag case head .164sqin(.457/2)²x314

But a 30,000psi 44 load x.164=4,920# while a 23,000 45 load x.181=4.163 and a 25000psi x .181=4,425

Point being whatever numbers you use the force exerted on the frame by a 45 colt under 25,000psi is still is still way under even the lightest 44 mag loads.

SAAMI Notice the very first word of their statement

""""Voluntary"""" Industry Performance Standards
for Pressure and Velocity
of Centerfire Pistol and Revolver Ammunition
for the Use of Commercial Manufacturers

Also

The use of American National Standards is completely voluntary; their existence does not in any
respect preclude anyone, whether he has approved the standards or not, from manufacturing,
marketing, purchasing, or using products, processes, or procedures not conforming to the standards

The standard for the 45 colt exist because of the original gun was the 1873 colt and any standard ammo has to be safe in it as well as all the rest of the 45 colts that are over 100 years old. I would never recommend such loads in such a gun.

 

[Model19man]

Regardless of your ignorance SAAMI is the accepted standard and while it states "Voluntary" every manufacturer adheres to their standards.

 

[steelslaver]

My ignorance??? I find that absolutely hilarious in face of your own statements.
Regardless of your lack of ability to think beyond the standards set because of some relics, I chose not accept those standards and so do a lot of others. If it had not been for people willing to do so the 44mag, the 45 super and its cousins, the 357mag, the 38 super and a whole host of other rounds would not exist. Discoveries and improvement have never been accomplished by those who only believe in sticking to standards

Your statement "while it states "Voluntary" every manufacturer adheres to their standards" is IGNORANT in the fact that it ignores a raft of manufactures who make 45 colt +P ammo like Buffalo Bores Heavy Pistol and Handgun Ammo, 45 Colt +P Ammo 260 gr. J.H.P. @ 1,450 fps/M.E. 1,214 ft lbs or Underwoods 45 Colt +P 250JHP at 1400fps. Would I fire those in a model 25? No, nor would I fire them in a 1873 colt. Novel thought. The shooter himself bears some responsibility in what he fires.

Although SAAMI NOW LISTS things like 38 Special, 45acp, 38 super and 9mm +P STANDARDS those are relatively new additions, and nowhere are there any 357+P or 38 +P+ standards, yet such ammo AND 45Colt +P exist and is readily available to those who are not so IGNORANT or rigid that they will not make reasoned decisions bases on solid engineering principals.

I am amazed that someone who fires SAMMI 21,000psi 45acp ammo in a model 25 doesn't have the mental horsepower to figure out that the same gun in 45 colt with the exact same chamber wall thickness and frame can't do the same.

Ya, being called ignorant frosts my butt, especially when I am not the ignorant person in the conversation.

 

[jem102]

Regardless of your ignorance SAAMI is the accepted standard and while it states "Voluntary" every manufacturer adheres to their standards.

Well, Buffalo Bore, Garrett, Choice Ammunition, Underwood, Double Tap and Grizzly didn't get the memo.


My reply above, though true, is a flippant one I would not normally use on this forum but the door was opened... It is apparent by reading through the posts those participating are not "ignorant" of the process or lack understanding of safe load development procedures.


Just because SAAMI has not taken measures to list +P specifications for the .45 Colt in modern firearms including the fact "folded head" cases have long since gone out of production does not mean it is not a viable pursuit or that SAAMI has indicated they have reviewed the cartridge and decided it is not a viable candidate for +P consideration.
You may want to section some new .45 Colt cases and compare them to .44 Mag cases as I have to note construction difference VS a a drop of 30% in pressure from the .44 mag cartridge. Just saying...



As has been stated until documented metallurgy becomes available it is up to each of us to evaluate our loading for this round. But ignorance is not at play in these threads if you please but rather some fact finding, intelligent and interesting discussion.

 

[steelslaver]

PS. I have modified several 45 colt cylinders by milling the center of the rear end of them .040 so they will accept 45acp in full moon clips. This leaves 3/4 of a 45 colt case unsupported for that .040,. I have never had a case head separation or bulge because of this even with rounds in the 23-25,000psi range.

same with a K frame 38 special setup to fire 38s or 9mm in moonclips

Some of us learn from actually doing, some only speculate and quiver

 

[BLUEDOT37]

By reducing the 36,000 PSI .44 Mag load by 25%, a significant number, we arrive at 27,000 PSI. "I" would consider this a safe working pressure for the Model 25 in the 5% larger head diameter .45 Colt cambering. This makes 23,000 PSI an easy all day long pressure for the Model 25.

All S&W N-frame revolver (.357, .41, .44, .45) cylinders, regardless of caliber, have a diameter of ~1.710".

At it's thinnest point, the cylinder lock notch, my S&W 45 revolvers average .030" thick (outside chamber wall thickness minus the lock notch's depth).

My S&W 44 Magnum's average .039" thickness.

That's makes the 45s ~23% less in thickness.

Making a few calculation (& some assumptions), if the 44Mag cylinder is designed for SAAMI 36K psi (40K cup) loads & the 45acp cylinder is ~77% as thick at the thinnest point, that puts it right at the ~28K psi mark.

(- 44 Magnum SAAMI Proof loads run ~50K psi -)
(- 45ACP (+P) SAAMI Proof loads run ~32K psi -)

.

Not a major disagreement, we're still in the same ballpark, but I don't see where you came up with your 25% reduction figure. The number (23%) I arrived at came from actual production model cylinder measurement differences.

Just as 36K psi is a working max for 44MAG I'd say that 28K psi is the comfortable working max for a modern S&W .45 cylinder.

And again, the cylinders are still proofed for higher pressures that ensure their integrity above that.

.

 

[BLUEDOT37]

Bolt Block

I agree with you and others that an N frame is an N frame and an M27 cylinder is an M25 cylinder is an M29 cylinder is an M24 cylinder is an M57 cylinder as applied to loads under 30,000 PSI regardless of cylinder stop notch location.

There is one difference that 44MAG N-frames have that not all N-frames have & that's the bolt block added as part of the Endurance Package to keep the cylinder from unlocking & rotating back a chamber under recoil.

I've not made a full inventory check for this feature on all of my N-frames but while I do know that my modern 41MAGs (57/357/657) also have this I can say that my .45s & 10AUTO N-frames do not.

So far I haven't remembered to check my .357s while they were apart to verify them.

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329PD bolt block - disengaged
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329PD bolt block - engaged
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[BLUEDOT37]

Breech Thrust can make a difference

Rim diameter is not a factor in back thrust only head diameter has direct impact on it.
The rim on the .44 Mag is .514 VS .512 for the .45 Colt = negligent impact.
Head diameter on the .45 Colt is .479-.480 VS .456-.457 for the .44 Mag for a difference of 0.023 = a 5% greater impact area on the recoil shield from the .45 Colt, a small number but notable.

I agree with your assumption that the .45 cartridge's larger diameter body is the driving force of its increased breech/bolt thrust.

In fact, one of the factors in the formula (Fbolt = Pmax (x) A external) to calculate this force is "the INSIDE area (of the cartridge case head) that the propellant deflagration gas pressure acts against.".

Here's some noteworthy related breech thrust calculations:

Breech thrust:
-------------------
45 Colt @ 14K psi = 2443 lbf
45ACP @ 21K psi = 3664 lbf
357Mag @ 35K psi = 3875 lbf
45ACP @ 23K psi = 4013 lbf
9mm+P @ 38.5K psi = 4533 lbf
45Super @ 28K psi = 4887 lbf
10mm @ 37.5K psi = 5217 lbf
44 Mag @ 36K psi = 5788 lbf
45 Colt @ 36K psi = 6282 lbf

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[ms]

Units?

I agree with your assumption that the .45 cartridge's larger diameter body is the driving force of its increased breech/bolt thrust.

In fact, one of the factors in the formula (Fbolt = Pmax (x) A external) to calculate this force is "the INSIDE area (of the cartridge case head) that the propellant deflagration gas pressure acts against.".

Here's some noteworthy related breech thrust calculations:

Breech thrust:
-------------------
45 Colt @ 14K psi = 2443 ft/lb
45ACP @ 21K psi = 3664 ft/lb
357Mag @ 35K psi = 3875 ft/lb
45ACP @ 23K psi = 4013 ft/lb
9mm+P @ 38.5K psi = 4533 ft/lb
45Super @ 28K psi = 4887 ft/lb
10mm @ 37.5K psi = 5217 ft/lb
44 Mag @ 36K psi = 5788 ft/lb
45 Colt @ 36K psi = 6282 ft/lb

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Thrust in ft/lbs?

 

[DR505]

There is one difference that 44MAG N-frames have that not all N-frames have & that's the bolt block added as part of the Endurance Package to keep the cylinder from unlocking & rotating back a chamber under recoil.

I've not made a full inventory check for this feature on all of my N-frames but while I do know that my modern 41MAGs (57/357/657) also have this I can say that my .45s & 10AUTO N-frames do not.


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The 25-9 (.45 Colt) engineering change has that part of the endurance package.