.45 Colt Chamber Pressure for Model 25

[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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Regardless of the rest of this conversation, this clear visual representation of the bolt block is very helpful. Thanks!

 

[TheTinMan]

Everyone - thank you for this interesting conversation.

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

Huh - I’m almost certain that my 25-10 doesn’t have that mechanism. But that was a special production run and does not have a frame mounted firing pin. For a moment I was wondering “What the heck is that odd mechanism above the cylinder latch (probably wrong words)?” I’ve never seen an infernal lock from the inside

 

[jem102]

BLUEDOT37


Onboard with your refined calculations and thank you.

 

[alwslate]

The elongated cyl locking notches are the indication of the endurance package, not a frame mounted firing pin.

 

[DR505]

Everyone - thank you for this interesting conversation.



Huh - I’m almost certain that my 25-10 doesn’t have that mechanism. But that was a special production run and does not have a frame mounted firing pin. For a moment I was wondering “What the heck is that odd mechanism above the cylinder latch (probably wrong words)?” I’ve never seen an infernal lock from the inside

The 25-9 has a hammer nose, not a frame mounted firing pin. It does not have the "infernal lock". We are discussing the Endurance Package which was started, IIRC, during the Model 29-3E run.

 

[steelslaver]

The endurance package is to keep the cylinder from coming unlocked under recoil. Mostly while firing heavy bullets at absolute max. pressures. I have never had that problem with any of my 45 colts using my heaver loads.

I firmly believe the longer stop notch used on the endurance packages has to weaken the cylinder some what. I know from pressure testing and inspection of pressure tubes that the the larger the thin spot the less pressure needed to cause a rupture. If someone believes making the notch longer doesn't make the cylinder weaker, ask them it they would be fine with one the full length of the cylinder. Thats what I thought.

Everyone talks about the stop notch and how thin it is right on center of chamber. But, how many realize that the area of it comes into play. I would bet you could drill a .050 hole completely through a chamber wall and neither it nor the brass would rupture. Remember it is psi. If the hole is only .050 you only have an area of .00196 sgin for the brass case to take the pressure. Not that I advocate drilling holes in cylinders. Make the cylinder notch longer and you increase the area of the thin spot in the cylinder

Here is another fun fact, A Ruger Super BlackHawk cylinder is the same OD (1.73) as a S&W N frame (1.72). Due to the Ruger design the stop notch is slightly off set from center of Chamber

 

[steelslaver]

If I ever get all my other projects done i want to make a heavy steel frame that holds a N frame cylinder and barrel and see just what it takes to blow up a 45 colt cylinder. I know for a fact that 21 gr of 2400 behind a 250 gr hard cast won't do it and that was in a cylinder that had chambers oversized enough that the brass swelled with normal loads

 

[Rpg]

The M25 and M57 and M29 frames are the same size, but the steel is hardened in the magnum caliber guns to withstand magnum pressures. .45 Colt was originally a black powder cartridge and once smokeless powder replaced it, they were operating at a higher pressure than black powder presented. Since it is still considered (in the smokeless powder world) a low pressure cartridge, the guns were not beefed up for higher pressures. The Ruger and Thompson guns are engineered for higher pressure ammo.

I think this is correct, but have no evidence it is. I’d be particularly interested in seeing the evidence that Smith has two or three different treatments for their N frames.

 

[jem102]

I think this is correct, but have no evidence it is. I’d be particularly interested in seeing the evidence that Smith has two or three different treatments for their N frames.

Exactly, but "I" don't know how we obtain that information. In the manufacturing world I retired from you would do everything possible to streamline the process meaning an N frame is an N frame is an N frame.


"If" we could obtain it we could really do something with our collective knowledge.

 

[steelslaver]

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. Then there is the liability issue. If it were important and there was any way possible one or more no treated frames became magnums, the lawyers would have fits. How many miss stamped frames have showed up here???

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.

 

[jem102]

I don't know if it's true or not but I was told by a ceramics engineer that was also an enthusiast like us, he passed from a sudden heart attack, that the RC is low on firearms to keep them "elastic". This enables them to stretch at the peak of the pressure pulse and then contract to design dimensions. He believed the steels used are alloyed to accomplish this but as the round count stacks up the continued cycles take the dimensions beyond design to the point they just don't function correctly such as head space becoming to great and barrels need set back etc.



I said "oh, you mean work hardening" and he said "no fatigue" and went into an explanation way over my head. It distilled down to that at some juncture in these cumulative cycles the steel says, I'm tired and I'm not coming back and becomes a wall hanger.


"I" don't know if this is correct but it sure sounds correct to me.

 

[Doug M.]

From a logistics and liability perspective, accepting that any one "N" frame can potentially be made into any model, it would be dumb to have different standards for the raw frame.

Hot tip: almost any sane .45 Colt load will do what it needed, at least in CONUS. If you need more power, get a .454 Casull or .500 or 460 or a rifle or a 12 gauge. This conversation is interesting, although the math is over my head, but in virtually all uses, utterly irrelevant.

 

[Patrick L]

I believe Brian Pearce also addressed this in Handloader. IIRC he viewed the .45 Colt as having three pressure tiers.

The lowest was SAAMI spec, that was for Colt SAAs, clones etc.

The top tier was for Ruger Blackhawks, Contenders, and a few others I can't recall.

He had a middle tier for 25-5s and a few other modern .45 Colts. It didn't go as high as the Blackhawk data (and the psi of other N frames like the M29), but it was higher than the tier 1 stuff.

I can't recall exactly when article appeared. Maybe 10-15 years ago??

 

[BLUEDOT37]

I believe Brian Pearce also addressed this in Handloader. IIRC he viewed the .45 Colt as having three pressure tiers.

He's definitely done a lot of articles on 45 Colt reloading.

I can only find one where he had expanded reloading data for three tiers in one article, Handloader #246 which was specifically for the RCBS 45-270-SAA LSWC bullet at 14K psi, 20K psi, & 32K CUP levels.

However in Handloader #217 he did have abbreviated load data for 14Kp, 19Kp, 23Kp, 32K CUP & 50Kp handloads. I'm guessing this was when he was just starting as its not up to his later article detail.

Mostly, in later articles, he's said 45 Colt (+P) loads should be held to 23K psi in modern medium framed revolvers, as in Handloader #337 which only had 23K psi load data.

Several times he's had articles listing 14K & 23K psi load data such as in Handloader #275.

Handloader #292 had Ruger Super Redhawk loads in the 45K-50K psi range only.

S&W M25 strength has come up several times over the years in his Bullets & Brass Q&A section, such as in Handloader #321.

I've got Handloader digital back issues to 1990 that I haven't been completely thru yet so there's probably more.

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[Patrick L]

Also, unlike those who say a 25 and a 29 are both N frames and therefore equal (I'm not in that camp!) wasn't he the one that drew comparisons between the N frame 45 Colts and the N frame .45 ACPs, which are rated for ACP +P loads that are definitely higher psi than 45 Colts? IIRC weren't they where the 23,000 psi tier came from?

 

[BLUEDOT37]

Bolt Block

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

Huh - I’m almost certain that my 25-10 doesn’t have that mechanism.

I definitely can't speak for what S&W did to all of the 45 Colt revolvers that left the factory but my 45 Colt M25-13 Rocky Mountain Ram, mfd. Sep-2003, does not have the bolt block machined into it.

None of my M325 or M625 .45ACP models have it either.

And the M610 10mm Auto (which I've converted mine to 10mm MAG), with its surprising breech thrust nearing the 44MAG, does not have it either.

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[BLUEDOT37]

Also, unlike those who say a 25 and a 29 are both N frames and therefore equal (I'm not in that camp!) wasn't he the one that drew comparisons between the N frame 45 Colts and the N frame .45 ACPs, which are rated for ACP +P loads that are definitely higher psi than 45 Colts? IIRC weren't they where the 23,000 psi tier came from?

The 23K psi max comes from the SAAMI 45ACP (+P) standard that all S&W 45ACP revolvers comply with.

The logic is a S&W 45 Colt cylinder/frame is just as strong as a S&W 45ACP cylinder/frame that's made for 23Kp.

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[alwslate]

Also, unlike those who say a 25 and a 29 are both N frames and therefore equal (I'm not in that camp!) wasn't he the one that drew comparisons between the N frame 45 Colts and the N frame .45 ACPs, which are rated for ACP +P loads that are definitely higher psi than 45 Colts? IIRC weren't they where the 23,000 psi tier came from?

I've read Brian's articles on handloading the .45 ACP and.45 Colt S&W revolvers and that's where the 23,000 psi rating came from. The .45 ACP +P level. The issue isn't the frame but the thin area of the cyl under the locking notches.

 

[StrawHat]

Yet, the Model 25-2 and later Models of the ACP revolver all handle the 45 Super with no problems.

Kevin

 

[BLUEDOT37]

I know for a fact that 21 gr of 2400 behind a 250 gr hard cast won't do it and that was in a cylinder that had chambers oversized enough that the brass swelled with normal loads

John Linebaugh in his article Gunnotes...S&W Model 25-5 listed a cast 260gr LSWC & 20gr/2400 @ 1070mv as "recommended max" and 22gr/2400 @ 1130mv as "ABSOLUTE MAXIMUM".

That same bullet with 24gr/H110 accounted for half of the 5000 rounds he had thru his 25-5 when he wrote the article.

I've shot a limited amount of 250gr P-TCFN bullets with 20gr/2400 in my 25-13 without issues.

I've shot a lot more of my 45WSM (link to thread) using 270gr LSWC-GC at 1100mv (my max.) from my 325TR (Sc frame & Ss cylinder) with no issues also.

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