38 Special +P loading

[Unclenick]

…For .38 Special, however, CIP's max pressure is 22,000 psi which is greater than even SAAMI's 20,000 psi limit for .38 Spl +P (CIP does not recognize any +P designations).

Note that CIP numbers are measured by a Kistler 6215 or similar piezoelectric transducer screwed into a hole in the pressure test gun that is aligned with a hole drilled into the case at 12.5 mm forward of the head in the pressure gun chamber. The U.S. pressure is measured through a hole in the pressure gun that is coupled to the transducer via a short steel connecting rod that is contoured to match the chamber at 0.600" (15.24 mm) forward of the head. This is done on the theory that pressure outside the case is what the chamber will experience and is, therefore, more important to know than the pressure inside the case as measured by the CIP method. There turn out to be drawbacks and advantages to both approaches, but the bottom line is the methods typically don't get matching results unless the transducers are first cross-calibrated with the other organization's reference ammunition. So, while the CIP method may produce a magnitude of 22,000 psi as the maximum average peak pressure, there is no way to know a load that matches that specification won't read 17,000 or 20,000 psi on SAAMI-style equipment without doing that cross-calibration.

 

[Nick_C_S]

At the risk of pulling us out of the quagmire, I do have some practical data you might find useful:

Using Win 231, with an Everglades 125 grain JHP, I got these results from a S&W Model 67 (a "38 Special +P" gun, as stamped on the 4" barrel).

5.2 grains: 955 f/s
5.4 grains: 966 f/s
5.6 grains: 978 f/s (5.6gn is Speer's published +P max)

With a 125 grain bullet, Win 231 is an excellent choice for +P ammo. Burns are consistent. Recoil and flash are quick and modest. It works really well. Slower propellants will deliver more velocity, but it'll come at the price of more flash and recoil (I get that we're not talking magnum level boom and blast here, but it is more than with faster propellants.) Example:

I loaded 125gn bullets to likely +P pressures using AA#2 and AA#5. Then I chronographed this ammo through my 4" Model 67, and my 2" (1.875", actually) Model 60. Here are the results . . .

Model 67, 4" bbl:
5.2 gn AA#2 - 934 f/s
7.4 gn AA#5 - 967 f/s

Model 60, 2" bbl:
5.2gn AA#2 - 866 f/s (5.3gn is Accurate Arms' published max)
7.4gn AA#5 - 871 f/s (7.5gn is Accurate Arms' published max)

The takeaway here is that there is very little gain moving from a fast propellant (AA#2) to an intermediate propellant (AA#5) - especially with snubby barrels. Flash and recoil was quite a bit more with the intermediate.

I load and shoot 38 Special more than than any other - for four decades. Almost every trip to the range, I shoot at least some ammo that is likely in the +P pressure range. I have used many propellants to load 125's to likely +P pressures: N-310, Nitro 100, Bullseye, W231 (& HP-38), AA#2, AA#5, HS-6, BE-86, and Power Pistol. It's all about doing safe work ups; and, understanding that max +P is only some 15% more that max non-+P.

 

[Webleymkv]

Originally posted by Unclenick
Note that CIP numbers are measured by a Kistler 6215 or similar piezoelectric transducer screwed into a hole in the pressure test gun that is aligned with a hole drilled into the case at 12.5 mm forward of the head in the pressure gun chamber. The U.S. pressure is measured through a hole in the pressure gun that is coupled to the transducer via a short steel connecting rod that is contoured to match the chamber at 0.600" (15.24 mm) forward of the head. This is done on the theory that pressure outside the case is what the chamber will experience and is, therefore, more important to know than the pressure inside the case as measured by the CIP method. There turn out to be drawbacks and advantages to both approaches, but the bottom line is the methods typically don't get matching results unless the transducers are first cross-calibrated with the other organization's reference ammunition. So, while the CIP method may produce a magnitude of 22,000 psi as the maximum average peak pressure, there is no way to know a load that matches that specification won't read 17,000 or 20,000 psi on SAAMI-style equipment without doing that cross-calibration.

It was my understanding that, with the same ammunition, CIP's pressure testing method will produce somewhat lower pressure readings than SAAMI's. For example, 9mm loaded to CIP max pressure and tested at such via CIP's method would be overpressure if tested by SAAMI's method despite the fact that CIP's max pressure for 9mm is actually slightly lower than SAAMI's at 34084 psi vs 35000 psi. This also explains why European 9mm ammunition like S&B, Fiocchi, Geco, and Norma often produce a bit higher velocity than their American counterparts though usually not drastically so.

As such, I'd expect CIP spec .38 Special ammunition to produce more pressure than SAAMI standard pressure.38 SPL and possibly be equal to or exceed the pressure of SAAMI .38 +P (commercial ammo is rarely loaded right up to the very edge of its pressure spec so it might be within SAAMI .38 +P specs). While I haven't chronographed it and don't have access to pressure testing equipment, the CIP spec .38 Special ammunition I've shot which includes S&B, Perfecta (Fiocchi), and Santa Barbara all had noticeably more recoil and often shot to a lower POI than SAAMI spec standard pressure .38 Special ammunition of the same bullet weight leading me to believe that the CIP spec ammo was loaded to higher velocity and likely higher pressure.

 

[Deltadart]

Why not contact the manufacture of the piece, with model number and ask if it is safe to use +P ammunition in it, if so then handload to tested and approved +P data from published reliable sources.

 

[Unclenick]

It was my understanding that, with the same ammunition, CIP's pressure testing method will produce somewhat lower pressure readings than SAAMI's.

No such reliable relationship, alas. For example:

357 Magnum
SAAMI: 35,000 psi; 45,000 CUP
CIP: 43,511 psi (3000 bar) by transducer; 46,412 psi (3200 bar) by copper crusher (this is from the 1995 Vihtavuori manual).

44 Magnum:
SAAMI: 36,000 psi; 40,000 CUP
CIP: 40,611 psi (2800 bar); 40,611 psi (2800 bar) by copper crusher (a rare case of agreement between the transducer and crusher).

9 mm Luger
SAAMI: 35,000 psi; 33,000 CUP
CIP: 34,084 psi (2350 bar); 39,160 psi (270 bar) by copper crusher.

223 Remington
US: 55,000 psi: 52,000 CUP, but M855 (equivalent to SS109) 58,200 psi; 55,000 CUP.
CIP:62,366 psi (4300 bar for both 223 Rem and SS109); 53,664 psi (3700 bar) by copper crusher.

38 Special
SAAMI: 17,000 psi. 17,000 CUP
CIP: 21,756 psi (1500 bar), 23,200 psi by copper crusher (1600 bar)

My guess is, given their physical similarities, that the 38 Special will echo the 357 Magnum transducer difference more closely than the 9 mm transducer difference. But as you can see, absolute ratios of behavior are not clear-cut, as differences in the measuring systems cause a lot of apples-to-oranges comparisons. The only way I know to settle the argument for a particular cartridge is to fire the other organization's reference loads after calibrating with one's own reference loads to see if there is a significant absolute difference or not.

Nick reminds me that a SAAMI +P velocity table would be a good indicator of what your loads are achieving if you have guns that copy their test gun styles and barrel lengths or know how to compensate a difference in them for estimating purposes.

 

[Jim Watson]

In a bygone era Norma had a product they called ".38 Special Magnum."
It contained a Secret Sauce Powder said to give high velocity without high pressure.
But when sold here and checked by SAAMI standards, it came out +P and they had to relabel it.

 

[Webleymkv]

Originally posted by Unclenick
No such reliable relationship, alas. For example:

357 Magnum
SAAMI: 35,000 psi; 45,000 CUP
CIP: 43,511 psi (3000 bar) by transducer; 46,412 psi (3200 bar) by copper crusher (this is from the 1995 Vihtavuori manual).

44 Magnum:
SAAMI: 36,000 psi; 40,000 CUP
CIP: 40,611 psi (2800 bar); 40,611 psi (2800 bar) by copper crusher (a rare case of agreement between the transducer and crusher).

9 mm Luger
SAAMI: 35,000 psi; 33,000 CUP
CIP: 34,084 psi (2350 bar); 39,160 psi (270 bar) by copper crusher.

223 Remington
US: 55,000 psi: 52,000 CUP, but M855 (equivalent to SS109) 58,200 psi; 55,000 CUP.
CIP:62,366 psi (4300 bar for both 223 Rem and SS109); 53,664 psi (3700 bar) by copper crusher.

38 Special
SAAMI: 17,000 psi. 17,000 CUP
CIP: 21,756 psi (1500 bar), 23,200 psi by copper crusher (1600 bar)

I understand that there's no direct conversion formula between PSI and CUP, but, if I understand what you're saying correctly, there is also no formula to convert pressures measured by SAAMI methods to CIP methods and vice versa? From the examples you listed, it would seem to me that the notion that SAAMI and CIP spec ammunition can be safely used interchangeably may not be correct as CIP ammunition is loaded to significantly different pressure specs, the methods of measuring pressure are so drastically different that we have no practical way of comparing one to the other without pressure testing equipment (which most of us don't have access to), or a combination of both. It has long been my understanding that while there are some differences in pressure between SAAMI and CIP spec ammunition, they're generally close enough that, as Paul Harrell would say, there isn't enough difference to make a difference but, based on the information you've provided this would seem not to be the case.

 

[44 AMP]

Isn't this whole thing just "a rose by any other name.."?

What I mean is, different methods using different systems come up with different numbers, but isn't the pressure being measured essentially the same??

and, whether you call it psi, cup, Kg/cm2 or some other name, the pressure is safe to shoot in each firearm, so, does it really matter? IF so, how much, and why?

 

[Webleymkv]

Originally posted by 44 AMP
Isn't this whole thing just "a rose by any other name.."?

What I mean is, different methods using different systems come up with different numbers, but isn't the pressure being measured essentially the same??

That's what I'm trying to ascertain, but the answer doesn't seem to be as clear cut as I thought it was. If we use the example of 9mm, a cartridge that tests at 34,084 psi per CIP's methodology will test in excess of 35,000 psi per SAAMI's even though it's the same cartridge generating the same pressure. If, as I understand it, because the testing methods are so different, there is no way to convert CIP pressures to SAAMI pressures without sophisticated and expensive pressure testing equipment so we have no way of knowing if a .38 Special cartridge that tests at 22,000 psi per CIP's methods will be equivalent to, less than, or in excess of SAAMI's 17,000 psi limit for their methodology. As such, it would seem to me that at the very least, if one has a gun that cannot/should not be fired with +P ammunition it might be best to also avoid CIP spec ammunition as we have no way of knowing if it's within SAAMI standard pressure or even +P pressure specs.

 

[74A95]

As such, it would seem to me that at the very least, if one has a gun that cannot/should not be fired with +P ammunition it might be best to also avoid CIP spec ammunition as we have no way of knowing if it's within SAAMI standard pressure or even +P pressure specs.

If that were the case I suspect owner's manuals would/could say to avoid ammunition loaded to CIP specs.

Here's what S&W put in their revolver owner's manual;

Use only commercially manufactured ammunition with internal
ballistic pressures which are in strict accordance with the specifications
of the Sporting Arms and Ammunition Manufacturers’
Institute (SAAMI). If you are uncertain, contact your ammunition
supplier for verification.

 

[Jim Watson]

Everybody wants to know the pressure.
All I want to know is whether I am loading within somebody's specifications suitable to my gun and since I do not have a pressure test system, it doesn't matter whether it is in SAAMI CUP or psi or CIP crusher or pizeo.