.45 Colt Chamber Pressure for Model 25

[Bryan Austin]

The "weak link" (per this discussion) in revolver strength is typically the thickness of material between the cylinder wall and cylinder lock detent.

 

[AJ]

The "weak link" (per this discussion) in revolver strength is typically the thickness of material between the cylinder wall and cylinder lock detent.

That is what I was trying to say in my original ost. But others told me that I was wrong. Post #2, maybe I worded it wrong?

 

[TheTinMan]

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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I don't want to beat a dead horse but do want to clarify when and in what models this "bolt block" mechanism was added. Am I correct in thinking now that it was not part of the endurance package introduced with the 29-3E/629-2E? If so when did appear?

 

[SlamFire]

The logistics of tracking frames with 2 heat treats don't make any sense, plus having done heat treating and knowing others who do it, as well as someone who was a foreman at the shop that HTed all the Leather man tools, I don't know how you would save much, if any, time or cost doing some with an inferior method and others with a best quality one.

Any production line set up to run garbage one day, and good stuff the next, would eventually only produce garbage, and the company would go out of business.

Plus, I have an Ames harness tester and I have found the frames to all be very close to the same hardness. But, then hardness is only one indicator. With cylinders and frames you need really good yield strength. Usually higher hardness indicates higher yield strength, but all the frames I have tested were fairly soft. So far down on the RC scale I got more consistent readings using a ball indicator and the B scale rather than a diamond and the C scale.

That yield strength is the point at which a material takes a load and still return to its original shape. Whereas tensile strength describes the maximum stress that a material can handle before breaking.

I would think as long as the recoil shield is hard enough not to deform due to cartridge pressure, that's probably all the hardness needed for the frame. Raising hardness reduces the fatigue life of a part. Each round fired, stretches the frame, but since the material is in the yield range, that's not a problem. Only becomes an issue when the fatigue life is low, because frame cracking would be a problem.

I will also state, if someone wants 454 Casull performance, go buy a pistol built for a 454 Casull. Trying to find the design limits on something that was never designed or built for a high pressure cartridge, its your money. And you are free to do whatever you want. So blast away, and see what happens.

I ain't going to do it.

 

[steelslaver]

No one is looking for 454 Casull performance. Just stepping up the MODERN 45 Colt to moderate pressure levels. Going from 750fps to 1000fps with a 255 slug with the colt. A 454 Casull moves a 260 gt out at 1800 fps Big difference

 

[BLUEDOT37]

Endurance Package

I don't want to beat a dead horse but do want to clarify when and in what models this "bolt block" mechanism was added. Am I correct in thinking now that it was not part of the endurance package introduced with the 29-3E/629-2E? If so when did appear?

The Endurance Package came in segments, on succeeding revisions, for the 44 Magnums that provoked the change. It consisted of five significant changes as detailed in the attached articles: -1) yoke bearing surface increased, -2) yoke heat treated, -3) radius stud package, -4) longer cylinder stop notches, and -5) the bolt block.

As already mentioned it's apparent not all of the features are applied to all caliber/cartridge N-frames, namely the bolt block.

While I strongly suspect all of the others are I can tell you that the longer stop notches are oddly not on my 45ACP Performance Center 625-8, mfd. Feb-2016.

The cylinder on this model is unique to it & is not the standard length as other 45ACP revolvers, it being ~1/8" shorter. Why the stop notch difference is anybody's guess though.

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Handloader# 241 excerpt:
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John Taffin "Book of the 44", excerpts between the red lines
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625PC with standard length cylinder stop notches (not Endurance Pkg length)
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[EfRed]

Some Thoughts on the .45 Colt

Everything I've read says cylinders fail at the cylinder lock notch, due to there being very thin metal there. When the cylinder fails, the top strap fails as well.

14,000 psi vs 23,000 psi (pressure limits on .45 Colt and .45 Auto). The .45 Auto is 0.04" smaller in case base diameter than the .45 Colt, so the bottom of the cylinder notch may be 0.02" thicker in the .45 Auto cylinder than in the .45 Colt cylinder, or 7%. The argument for using the .45 Colt at .45 Auto pressures may break down a bit due to this.

The .45 Colt pressure limit is low because pre-1900 revolvers lacked "modern steel." So it seems to follow that using modern steel with greater tensile strength will permit higher pressure loads. The tensile strength for "modern steels" varies by far more than a factor of two, depending on treatment. So its possible that better steel will support a greater pressure limit. It's also possible that a stronger steel may be used on .44 Mags or .45 Autos than on .45 Colts (or not).

Mr. Linebaugh's words comparing the relative performance of .45 Colt and .44 Mag are true.

Bryan Pearce's experience with the .45 Colt revolvers carries great weight. I do believe that any modern .45 Colt revolver taken to 23,000 psi will survive, safely. For 20 years, my Father shot 9 gr Unique w/ 260 gr KT semiwadcutter in his 1939 SAA. I have the gun. It's pretty loose compared to a new SAA, and that may be because the load overstressed it, or just because its a Colt with softer part steel. The load came from Phil Sharp, and like most of his loads tended to push things.

A revolver will usually be proof-tested at something like 2 times its book pressure. So the question would appear to be more wear and tear than failure. Though that takes us right back to Elmer Keith's early experiments, where he tested quite a few .44 Spls, to failure.

You are undoubtedly safe at 14,000 psia for the .45 Colt. You're likely safe at 23,000, though you may wear your gun a bit with prolonged use. Modern Colts and S&Ws probably ought not be loaded to pressures exceeding 23,000 psi.

The final point is: why? A .45 Colt 260 gr at 960 fps may be had at about 14,000 psi. My Father shot a 2000 lb horse through both shoulders with one; the factory load stopped at the skin on the opposite side, his handload penetrated completely and he found it stuck in the fence plank beyond. This is a lot of penetration and very good performance. With a proper bullet and placement, it will stop a charging grizzly. What more is needed from a sidearm?

 

[pmhayden]

This thread is interesting. I appreciate the technical data, and own a M25-5 (with correct throats and perfect blueing). I also have a newer flattop NM Blackhawk in .45LC on the mid-size frame. My experience is that both revolvers will shoot a 255-260 gn cast bullet over 8.5 gn of Unique or BE-86 without any short term problem. This feels like a Tier 2 load, though I have seen various tables that show it to be something else. On the other hand, it is not a fun load to shoot in either revolver, and I stay at 8.0 gn of Unique (or BE-86) in these two guns. I bought a large frame NM Blackhawk in .45 LC, and replaced the grip frame with a steel frame, to shoot the 8.5 gn load. It is a heavier gun, with a larger grip than the flattop. No qualms.

The 8.0 charge under a 255 gn cast .45LC bullet is still a heck of a lot of gun, for hunting, target or self defense. Loading an 1873 bullet to .44 magnum levels is interesting in an academic way. But as a 71 y/o retired guy, I cannot afford to buy another M25, so I want to be careful of this one. I also have two beautiful Model 15-4s. I baby those, too, for the same reason. But your guns, your loads.

I am not able to do more than put my blind faith in the technical data here (not an engineer), but noticed that it was not expressed in powder, bullets, and weights; rather as units of pressure and thickness of steel. But in terms of recoil, the .45LC tells me not to try and prove anything in my nicer revolvers, and to accept it for what it is - a historic 1873 cartridge that still gives good service. I cast these bullets in a Lyman Keith mold, tumble lube with hoarded Johnson's floor wax (LOL), use a powder that Phil Sharpe used before my father was born, in one of the most beautiful revolvers made, and feel blessed to do so.

 

[Garrett-J]

The three-tier approach to .45 Colt loads generally works. Except that there is not a lot of readily available data for the Tier-2 loads, which would be appropriate for the S&W revolvers.

There is data out there in a number of magazines and online articles, but I say it's not readily available as I have never seen any of this mid-range data in a published reloading manual. Searching through years of articles is not the same as just flipping through a book to a section that would be found between Colt SAA loads and "Ruger Only" loads.

Some manuals list pressures for their min & max loads. However, I have not seen manual listing a range of pressures for any given bullet/powder. The min/max pressures can be used as a general guideline, but keep in mind the progression of pressure increase to powder charge is not going to be linear.

Similarly, there are a few computer models that can estimate chamber pressures for a given load. But again, these only provide estimates.

This is not to say one should not use this info and work up carefully. Just noting some of the potential shortcomings with this approach.

I have an M25-15 that generally only sees Tier-1 loads. I have other revolvers that are capable of safely handling higher pressures. But if I didn't, I would not be uncomfortable loading somewhere between the published SAA-appropriate loads and the Ruger-only loads.

 

[RebCop]

Chuck Taylor did a series of books where he tested guns in Alaska. I was surprised as he used Ruger loads in his test of the 25-5 and had no problems. I would however expect it would contribute to frame stretch and other problems.

 

[steelslaver]

I have pin gauges and have found that initial portion of S&W 45 ACP chambers are the same dia as 45 colt chambers for all intents and purposes. Interestingly they both can vary by .001

The notch is the week point, BUT, the length of the notch also comes into play. The wider or longer the notch the greater the unsupported area surrounding it. An endurance package cylinder is weaker than the earlier cylinders simply because of the longer notch. Don't think so? Try making the notch the full length of the cylinder and see what happens. S&W engineers were well aware of this FACT when they made the chances and did it anyway because they KNEW the cylinder would still handle it.

There is no way a 45 colt frame will suffer frame stretch at 25,000psi and a 44 mag firing rounds at 36,000 won't . It is silly to even believe that. Both will eventually shoot loose. But only after about spending a lot more for ammo (even reloading) that the value of the gun. 10,000 rounds x 10 cents is $1000. Then a shim or 2 and barrel set back might be in order and your forcing cone will probably need it anyway

 

[grice]

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?

Yes they are!

 

[Outpost75]

There are three pressure levels for .45 Colt:
- 14,000 psi for older .45 Colts;
- 21,000 psi for newer modern era smokeless powder .45 Colts; and
-30,000-32,000 psi load for Ruger only and T/C handguns, as well as the Winchester Model 1892 and Rossi 92 lever action rifles.

Those 30,000-32,000 psi loads give essentially .44 magnum level performance. But frankly case life at higher pressures in the .45 Colt is very short. The .45 Colt chamber was made with a .007" taper from base to case mouth to facilitate extraction from black powder fouled chambers and those chamber dimensions persist today for the parallel case wall .45 Colt.

That means the case expands in an increasing and linear manner from mouth to base which stretches the case walls significantly at higher pressures. At 30,000 psi you can expect spider cracks in the case walls in as little as 3 or 4 reloads. At most you'll be lucky to get 5-7 loads in the case before it's scrap.

In other words, if you want .44 Mag performance from a .45 Colt, just get a .44 Mag.

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The S&W 25, like the 625, runs just fine at 21,000 psi .45 ACP pressures. I would not push it to 23,000 psi .45 ACP +P pressures as S&W doesn't recommend it for the 625.

And there's no real point.

People don't understand that the 23,000 figure for .45 ACP+P is NOT a machine loading limit, but represents the maximum probable individual pressure or PMax, defined as the sample mean X-bar plus 3 standard deviations. X-bar+3 Sigma.

Unless a load has excellent MEASURED (not a Quickload estimate) ballistic uniformity you should limit loads to pressure tested data from powder and bullet manufacturers which do not exceed 20,000 psi. Heavier loads are not "dangerous" when used in moderation, but WILL accelerate wear, impairing reliability, maintainability and durability.

In revolvers barrel-cylinder gap has as much influence on velocity as barrel length. In cartridges similar to .38 Special or .45 ACP loaded with faster burning powders similar to Bullseye, TiteGroup, 231, WST the expected Delta-V is about 10 fps for each 0.001" change in B-C gap from Mean Assembly Tolerance. A 4-inch gun at minimum pass 0.004/ hold 0.005 will likely produce higher velocity than a 6-inch gun at maximum pass 0.008 / hold 0.009". These days S&W does not repair an OFG ( open front gage) up to 0.010" - they ship'em.

 

[Scrateshooter]

,I don't know the answer but many times, albeit wording differs, the question arises is an N frame, an N frame always an N frame? If the answer is yes, why would a 23,000 PSI load in a Model 25 stretch the frame when a 34,000 PSI load in a Model 29 is a working load? There is a difference of 0.024 case diameter between the two calibers as concerns back thrust which would be compensated for by the 13,000 lower PSI in the .45 load. So is the metallurgy or heat treatment among N frames different? If it is, with the Model 25 being of less tensile strength due to these factors, "I" would consider 18-20,000 PSI to be the working pressure for a model 25

I had a S&W 629-6 Deluxe converted to 45 Colt and the pistolsmith still told me I shouldn't shoot any loads over 45acp +p pressure.

Strange...
I figured as you.

 

[Outpost75]

The cylinder walls of the 45 Colt cylinder are quite a bit thinner than the .44 Mag and the thickness under the locking bolt notches is quite a bit thinner. These can cause problems if you overload it.

 

[BLUEDOT37]

Concerning the question about frame stretching: a .45 caliber cartridge exerts more breech-bolt thrust on the frame than does a .44 cartridge when loaded to the same pressures.

Notice the increase in force from a standard power 45ACP -vs- 45ACP (+P) -vs- 45 Super. Also a 36K load in 45 Colt -vs- 44 Mag.

Some numbers to ponder:

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
500Spcl@ 36K psi = 7786 lbf

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[steelslaver]

I would not loat a S&W model 25 to 36,000psi. But I fail to believe that your going to wear or stretch a frame any worse than a 44 mag does loading them in the 23,000m to 25,000 psi range which should not approach the 44 mags 5788 lb

The truth is the heavier bullet and/or the higher the pressure OF ANY round the harder on the gun AND the shooter. But your going to spend multiple time the money on ammo and or reloading components that the gun is worth before you wear one out with loads under 23,000psi, 357, 41 mag 44 mag, or any of the 45s

 

[Imissedagain]

Starline has 45 Colt and 45 Super brass.
Check their specs.
Just received 100 of each.
For the Blackhawk 45 Convertible, bought new around '80, and the WinMiruko '92.
Put a SS frame on the 7.5" BH, and the balance is nice.
Smith at Ruger, long ago, made it a very accurate gun.
Returned with a 50yd, Bullseye target, 6 in under 2".
Dropped some 1911 grips, in the box, when I sent it to him.

Passed on the M25 for 45 Colt, back around '80, as it was advised not shoot Ruger only loads.
3.5" barreled 460s, for carry, when necessary.
Too old to run.

 

[shawn mccarver]

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?

I suspect the higher pressure is meant for the Ruger Blackhawk.

 

[steelslaver]

I suspect the higher pressure is meant for the Ruger Blackhawk.

Thing is a Ruger cylinder is the same diameter as one from an N frame Smith. The Ruger cylinder stop notch is however SLIGHTLY offset from dead center on the chambers

This argument about S&W 45 colt loads goes on and on despite the fact plenty of us fire higher than the 14,000psi loads set to keep 45 colt ammo safe for antiquated guns, which the model 25 ISN'T. The idea that one in 45 ACP is safe at 23,000psi and one in 45 colt isn't defies any kind of logic or principle. I keep thinking of machining out a heavy but simple test frame that I can mount a 45 colt cylinder and barrel in and fire remotely and proceed to blow up the cylinder up. Start at 20gr of 2400 and go up .5 gr at a time. I bet it takes loads over the max 44 mag range to do it. I don't believe in "magnuming" 45 colts, but the 14,000psi limit for model 25s is ridiculous and personally believe a S&W 45 colt cylinder your not all that close to going over the yield strength at 25,000psi. Yield being the point at which a metal deforms, where tensile is beyond that and the point where it fails

 

[unspellable]

Both the S&W 25 and Blackhawk cylinders in 45 Colt will blow out at about 60,000. The S&W is more susceptible to developing end shake, not because the frame stretches, but because the yoke tail cuts a groove in the bottom of the cylinder well. The Blackhawk locates the cylinder by the neck bearing on the frame with a much larger surface area. That said, the S&W and a number of other modern 45s will take a heavier load than the old SAA. The problem is there is no published data for such that I am aware of.

 

[jreidthompson1]

Accurate powder manual edition 3.5 lists ~20k psi load data.

There's also lots of data listed as Tier 2 45 colt loads in many reloading magazines. Search colt 45 tier 2 load data

 

[Lt.Donn]

I would not loat a S&W model 25 to 36,000psi. But I fail to believe that your going to wear or stretch a frame any worse than a 44 mag does loading them in the 23,000m to 25,000 psi range which should not approach the 44 mags 5788 lb

The truth is the heavier bullet and/or the higher the pressure OF ANY round the harder on the gun AND the shooter. But your going to spend multiple time the money on ammo and or reloading components that the gun is worth before you wear one out with loads under 23,000psi, 357, 41 mag 44 mag, or any of the 45s

Truth...in our collective hundreds of years of shooting...I have yet to see any platform worn out from shooting...shot a little lose, yrs, a fractured part or 2 , yep, but shot to the point of being flat wore out...not me...but I'm certain some maybe pro shooters have

 

[rockquarry]

Truth...in our collective hundreds of years of shooting...I have yet to see any platform worn out from shooting...shot a little lose, yrs, a fractured part or 2 , yep, but shot to the point of being flat wore out...not me...but I'm certain some maybe pro shooters have

I don't know what a platform is in relation to guns, but many moderneers like that term. As for .45 Colt data, what's wrong with using reliable and suggested data from reputable paper load manuals? Am I missing something important? I loaded for this cartridge for about forty years in a variety of revolvers and long guns using cast bullets. I finally lost interest in the cartridge and the guns.

 

[Lt.Donn]

I don't know what a platform is in relation to guns, but many moderneers like that term. As for .45 Colt data, what's wrong with using reliable and suggested data from reputable paper load manuals? Am I missing something important? I loaded for this cartridge for about forty years in a variety of revolvers and long guns using cast bullets. I finally lost interest in the cartridge and the guns.

And you didn't wear the gun out

 

[rockquarry]

And you didn't wear the gun out

No, and I shot them a lot. I have a couple of Model 29s (the newest one I've had for forty years or more) if I get the urge to load powerful. Why beat up a 25-5?

 

[RebCop]

Thing is a Ruger cylinder is the same diameter as one from an N frame Smith. The Ruger cylinder stop notch is however SLIGHTLY offset from dead center on the chambers

This argument about S&W 45 colt loads goes on and on despite the fact plenty of us fire higher than the 14,000psi loads set to keep 45 colt ammo safe for antiquated guns, which the model 25 ISN'T. The idea that one in 45 ACP is safe at 23,000psi and one in 45 colt isn't defies any kind of logic or principle. I keep thinking of machining out a heavy but simple test frame that I can mount a 45 colt cylinder and barrel in and fire remotely and proceed to blow up the cylinder up. Start at 20gr of 2400 and go up .5 gr at a time. I bet it takes loads over the max 44 mag range to do it. I don't believe in "magnuming" 45 colts, but the 14,000psi limit for model 25s is ridiculous and personally believe a S&W 45 colt cylinder your not all that close to going over the yield strength at 25,000psi. Yield being the point at which a metal deforms, where tensile is beyond that and the point where it fails

I believe sir you win the internet.

 

[steelslaver]

No, and I shot them a lot. I have a couple of Model 29s (the newest one I've had for forty years or more) if I get the urge to load powerful. Why beat up a 25-5?

my point IS 23,000psi loads will not beat up a model 25 and certainly no more than a 36,000 psi load will beat up a model 29. I have 3 45 colts I built from 1917 frames, one of them a Brazilian, all have also been machined for adjustable sights, and both of them have been subject to lots of loads in the 23,000psi range, yet neither is loose or "beat up"

 

[rockquarry]

my point IS 23,000psi loads will not beat up a model 25 and certainly no more than a 36,000 psi load will beat up a model 29. I have 3 45 colts I built from 1917 frames, one of them a Brazilian, all have also been machined for adjustable sights, and both of them have been subject to lots of loads in the 23,000psi range, yet neither is loose or "beat up"