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We always say "THE LAWYERS DID IT!"
- Thread starter Sevens
- Start date
Peter,
Thanks for some numbers.
(For anyone following this, note that in 1953 everyone still believed copper crushers were reporting pressure accurately, so where Peter quotes their psi, today they would be called CUP.)
SAMMI lists both a 4" revolver type test barrel (with 0.008" barrel/cylinder gap equivalent) and a 10" one-piece barrel (like a Contender barrel). A model 27's 8 3/8" barrel would have about the same length to the recoil shield as a 10" Contender barrel has to its breech, given the different barrel measuring methods used. So I would expect the velocities for the model 27 to be about what SAAMI lists as standard for their 10" tube.
SAAMI doesn't have a 153 grain bullet listed, but for either a 158 grain soft point or semi-jacketed hollow point, the velocity standard is:
1220±90 fps for the 4" revolver type barrel wit 0.008" barrel/cylinder gap.
1600±90 fps for the 10" one-piece barrel.
So I'm not convinced there's a difference in the standard that is real. I looked at a box of Winchester Super-X 158 grain JHP's and one of SP's, and it claims Muzzle Velocity to be 1235 fps, which is certainly to SAAMI's 4" test barrel specifications, so it doesn't look like it's loaded down any.
Your gun probably is not as tight as a 10" SAAMI test barrel and maybe not as tight as the gun HP White used. The SAAMI standard requires each round to be conditioned at 60-80 °F before firing. It has to go through the "SAAMI twist" to keep powder over the flash hole for firing. I don't know how much your testing deviated from that, but differences could certainly tell. I don't know how accurate your chronograph was that day. I've see two side-by-side disagreeing by 200 fps on one occasion.
The ballistic lab sounds like a good project. A couple of things I've noted over time: Denton Bramwell's stats indicated strain gauges are actually more repeatable than either conformal piezoelectric transducers and much more than copper crushers. Jim Ristowe at RSI, the maker of Pressure Trace says 60% of his sales are into the industry rather than to private owner, so it seems to be increasingly a less expensive alternative that is accepted. The main limit it has is that it is 8 bit rather than 10 bit resolution, like an Oehler model 83 commercial test instrument.
The CIP claims its channel piezoelectric transducer system is accurate within 2%. I don't know how they arrive at that, but they certainly are more consistent in the numbers they produces as compared to copper crushers than the conformal transducer is. You do have to drill holes in cases to use their system, though.
Bryan Litz has tested a lot of different chronographs and determined that 15 fps is about as close as the optical ones get, real world. He is currently recommending the long-sabre version of the Magnetospeed product. I keep waiting for the Labradar Doppler instrument to become available and prove itself, as it should be the most accurate, in theory.
Thanks for some numbers.
(For anyone following this, note that in 1953 everyone still believed copper crushers were reporting pressure accurately, so where Peter quotes their psi, today they would be called CUP.)
SAMMI lists both a 4" revolver type test barrel (with 0.008" barrel/cylinder gap equivalent) and a 10" one-piece barrel (like a Contender barrel). A model 27's 8 3/8" barrel would have about the same length to the recoil shield as a 10" Contender barrel has to its breech, given the different barrel measuring methods used. So I would expect the velocities for the model 27 to be about what SAAMI lists as standard for their 10" tube.
SAAMI doesn't have a 153 grain bullet listed, but for either a 158 grain soft point or semi-jacketed hollow point, the velocity standard is:
1220±90 fps for the 4" revolver type barrel wit 0.008" barrel/cylinder gap.
1600±90 fps for the 10" one-piece barrel.
So I'm not convinced there's a difference in the standard that is real. I looked at a box of Winchester Super-X 158 grain JHP's and one of SP's, and it claims Muzzle Velocity to be 1235 fps, which is certainly to SAAMI's 4" test barrel specifications, so it doesn't look like it's loaded down any.
Your gun probably is not as tight as a 10" SAAMI test barrel and maybe not as tight as the gun HP White used. The SAAMI standard requires each round to be conditioned at 60-80 °F before firing. It has to go through the "SAAMI twist" to keep powder over the flash hole for firing. I don't know how much your testing deviated from that, but differences could certainly tell. I don't know how accurate your chronograph was that day. I've see two side-by-side disagreeing by 200 fps on one occasion.
The ballistic lab sounds like a good project. A couple of things I've noted over time: Denton Bramwell's stats indicated strain gauges are actually more repeatable than either conformal piezoelectric transducers and much more than copper crushers. Jim Ristowe at RSI, the maker of Pressure Trace says 60% of his sales are into the industry rather than to private owner, so it seems to be increasingly a less expensive alternative that is accepted. The main limit it has is that it is 8 bit rather than 10 bit resolution, like an Oehler model 83 commercial test instrument.
The CIP claims its channel piezoelectric transducer system is accurate within 2%. I don't know how they arrive at that, but they certainly are more consistent in the numbers they produces as compared to copper crushers than the conformal transducer is. You do have to drill holes in cases to use their system, though.
Bryan Litz has tested a lot of different chronographs and determined that 15 fps is about as close as the optical ones get, real world. He is currently recommending the long-sabre version of the Magnetospeed product. I keep waiting for the Labradar Doppler instrument to become available and prove itself, as it should be the most accurate, in theory.
Peter M. Eick
New member
Thank you for the comments.
I specifically bought a contender with the idea of going the strain gauge route but I was later told the contenders where springy and did not give good strain gauge data like the RSI. I was originally planning on an RSI setup on my contender in 38/357 mag/357 Maximum but have since backed off that approach. Any thoughts or comments?
Your point about the different velocities and the different pressures today vs. days gone past is exactly why I want to build my own little pressure lab and start measuring this stuff once and for all. I have several 8 3/8" pre-27's and all of them are slow it seems relative to what they should have produced with modern ammo. Fire vintage ammo in them and they speed up and are closer to the original velocities.
I have seen this same issue with my 38/44's. Vintage (late 30's, 40's and 50's vintage) ammo over and over again comes close (never exceeds though) to original posted velocities and specifications in my guns. So why should a 357 Magnum be much different than a 38/44?
I tend to agree that the old copper crusher PSI method was flawed. I think we all accept that readily. The real question at the heart of the matter is how do you handle it? I don't know which is why I am looking into this and investigating pressure measuring hardware.
So far, I like the setup that I can get from Wiseman the best but I do see that technology is improving quickly with the strain gauges. For me this comes down to a bothersome question and something to do when I retire. I would just like to be able to sit down and start measuring pressures of various loads and commercial ammo and write a book about what the raw data is. Basically simple dumb questions like how much pressure does 15 grns of 2400 with a 158 LSWC really produce in a 357 Magnum? Or, does a small pistol magnum primer really produce more pressure than brand y's SPM primer and how much?
To me that would be a very entertaining and interesting way of whiling away a retirement.
Back to the point at hand.
I agree with your fundamental point that the there may not be a difference in the standard. I just don't know and that is the basic question in this thread since others are asking the same thing.
I am open to suggestions on how we can sort this out and document it. I have balked on Wiseman so far because frankly to set myself up will be about $60K which is more then I want to drop right now. Until I retire, I can't swing that much so in the mean time, what would your recommend would be a way to acquire data and start evaluating the basic question?
I specifically bought a contender with the idea of going the strain gauge route but I was later told the contenders where springy and did not give good strain gauge data like the RSI. I was originally planning on an RSI setup on my contender in 38/357 mag/357 Maximum but have since backed off that approach. Any thoughts or comments?
Your point about the different velocities and the different pressures today vs. days gone past is exactly why I want to build my own little pressure lab and start measuring this stuff once and for all. I have several 8 3/8" pre-27's and all of them are slow it seems relative to what they should have produced with modern ammo. Fire vintage ammo in them and they speed up and are closer to the original velocities.
I have seen this same issue with my 38/44's. Vintage (late 30's, 40's and 50's vintage) ammo over and over again comes close (never exceeds though) to original posted velocities and specifications in my guns. So why should a 357 Magnum be much different than a 38/44?
I tend to agree that the old copper crusher PSI method was flawed. I think we all accept that readily. The real question at the heart of the matter is how do you handle it? I don't know which is why I am looking into this and investigating pressure measuring hardware.
So far, I like the setup that I can get from Wiseman the best but I do see that technology is improving quickly with the strain gauges. For me this comes down to a bothersome question and something to do when I retire. I would just like to be able to sit down and start measuring pressures of various loads and commercial ammo and write a book about what the raw data is. Basically simple dumb questions like how much pressure does 15 grns of 2400 with a 158 LSWC really produce in a 357 Magnum? Or, does a small pistol magnum primer really produce more pressure than brand y's SPM primer and how much?
To me that would be a very entertaining and interesting way of whiling away a retirement.
Back to the point at hand.
I agree with your fundamental point that the there may not be a difference in the standard. I just don't know and that is the basic question in this thread since others are asking the same thing.
I am open to suggestions on how we can sort this out and document it. I have balked on Wiseman so far because frankly to set myself up will be about $60K which is more then I want to drop right now. Until I retire, I can't swing that much so in the mean time, what would your recommend would be a way to acquire data and start evaluating the basic question?