Seismic Sam
Member
To begin with, please refer to this thread as a preface to what I'm about to say:
http://www.thehighroad.org/showthread.php?t=502850&page=2
While I was loading up a bunch of 357 SIG brass using 125 grain Speer Gold Dots with AA#9 powder, I was experiencing a somewhat frustrating lack of consistency with the OAL of the finished rounds. I had set the seating die to deliver an OAL of 1.130", but I was getting everything from 1.135" down to 1.120", and at the time I was preoccupied with how much the case might be getting shortened or lengthened by the case bulging and then DE-bulging process. At the time I assumed (without really thinking it through) that my OAL variability was somehow coming from brass of different length, and just ignored the situation. The resulting ammo behaved itself fairly well, turning in a velocity of about 1440 FPS with a velocity standard deviation of 14 FPS, which is a typical value that doesn't indicate anything is out of whack at all.
Unfortunately, Speer 125 grain Gold Dots are pushing $25/100 these days, and so I was looking around for a cheaper alternative. Came across some Montana Gold 124 grain JHP bullets for $14.00/100, and the bullet had the long, straight sides that you must have to use this bullet in 357 SIG, so I bought a 100. So I go home, use my Lyman M die (expander die) in .355" to just slightly bell the top .010" of the case, and then prime the cases. Previous trips to the range had shown that the Speer #14 manual was right on the money with it's load data for the 125 grain Gold Dot, with a workup of 1/10th grain increment loads bringing up the velocity in a nice, linear fashion to a max velocity just shy of 1450 FPS with 14.6 grains of AA#9. The manual listed it at 1437 FPS, so it was nearly dead on.
Due to the problems with base bulging at 1400+ velocities, however, I decided to be nice to my brass and go down to 13.8 grains of AA#9 with the Montana Gold bullets. So I charge powder into 50 cases in a block of 100 primed cases, and set my seating die to deliver a cartridge OAL of 1.140" which is the max for this caliber. Just as I had hoped, with this OAL the straight wall of the bullet was still sligthly protruding above the case mouth, so I could add a .003" taper crimp with a Lee factory crimp COLLET die. (Remember, this is a bottleneck case, and NOT a straight wall!!) So I get the seating die set up, and start seating bullets. Once again, I start getting variability in my cartridge OAL.
Whiskey Tango Foxtrot???
This is really starting to bug me, and I grab another case, and seat the bullet. For some strange reason, the seating pressure is really low, and the cartridge OAL is all of a sudden 1.112"!! :angryvillagers: I try 4 more cases, get 4 more light seating pressures, and an OAL of 1.112" :hmm: Then I notice that in my distracted state, I had gone down the left side of the load block instead of across it, and had loaded up 5 rounds WITH NO POWDER IN THEM!! What?? With no powder I get an OAL of .030" LESS??
About that point, it dawns on me that the only variable that has changed is the powder in the case, and I come to the conclusion that I must be compressing the powder to make up for the difference in seating pressure. Once I realize this, it THEN occurs to me that because of the pressure of the compressed powder in the case, I am getting DIFFERENT OAL's that are PROPORTIONAL to the seating pressure.
After some additional fiddling around, I come to an even more unsettling discovery. The OAL is PROPORTIONAL to the SPEED of the press handle!! A quick press stroke procuces a longer OAL that a slow and deliberate press stroke.
Unsettling discovery #2, consistent with #1. Two quick press strokes produce a shorter OAL than 1 quick press stroke.
Putting all this together, what appears to be happening is that the compressed powder is acting like a spring, and keeping the bullet higher up in the case that what you would get with an empty case, by a whopping .030"!! To make matters even more fun, this compression appears to be time dependent, so the longer it takes to seat the bullet, the more the spring effect of the powder goes down, along with the OAL.
From a purely "FEEL" standpoint, it became clear that 2/3rds to 3/4 quarters of the seating force was the pressure of compressing the powder, and once I figured this out I could "double tap" the seating on a hard seating bullet to get the cartridge OAL close to 1.140" almost every time.
About this time I recall a similar peculiar instance with reloading my 50GI cases with a measly 8.0 grains of Herco for the +P load, and getting similar OAL variations. In this case, there appeared to be PLENTY of space left in the case, but a Speer 300 grain 50 caliber Gold Dot apparebntly took up more space that I thought. A that time, I had surmounted that problem by using a slow, deliberate press stroke, without realizing that i was working with a compressed powder charge.
Obviously, this problem/phenomena will be extremely dependant on thre things:
The exact weight of the powder charge. There will be some statistivcal variations here.
The exact volume of that cartridge case. There will be some statistical variations here.
The amount of free air in the settled (but not compressed!!) charge. Obviously, a flake powder like Herco will have more entrained air than a fine grained powder like AA#9, so it can be compressed somewhat further wiout this weird spring effect taking over.
That being said, however, it would appear that if you start getting different cartridge OAL's after locking down your seating die, you may be working with a compressed powder charge, even though your manual isn't telling you that your are in this zone!!
So be safe out there, and keep your eyes open for this situation!!
http://www.thehighroad.org/showthread.php?t=502850&page=2
While I was loading up a bunch of 357 SIG brass using 125 grain Speer Gold Dots with AA#9 powder, I was experiencing a somewhat frustrating lack of consistency with the OAL of the finished rounds. I had set the seating die to deliver an OAL of 1.130", but I was getting everything from 1.135" down to 1.120", and at the time I was preoccupied with how much the case might be getting shortened or lengthened by the case bulging and then DE-bulging process. At the time I assumed (without really thinking it through) that my OAL variability was somehow coming from brass of different length, and just ignored the situation. The resulting ammo behaved itself fairly well, turning in a velocity of about 1440 FPS with a velocity standard deviation of 14 FPS, which is a typical value that doesn't indicate anything is out of whack at all.
Unfortunately, Speer 125 grain Gold Dots are pushing $25/100 these days, and so I was looking around for a cheaper alternative. Came across some Montana Gold 124 grain JHP bullets for $14.00/100, and the bullet had the long, straight sides that you must have to use this bullet in 357 SIG, so I bought a 100. So I go home, use my Lyman M die (expander die) in .355" to just slightly bell the top .010" of the case, and then prime the cases. Previous trips to the range had shown that the Speer #14 manual was right on the money with it's load data for the 125 grain Gold Dot, with a workup of 1/10th grain increment loads bringing up the velocity in a nice, linear fashion to a max velocity just shy of 1450 FPS with 14.6 grains of AA#9. The manual listed it at 1437 FPS, so it was nearly dead on.
Due to the problems with base bulging at 1400+ velocities, however, I decided to be nice to my brass and go down to 13.8 grains of AA#9 with the Montana Gold bullets. So I charge powder into 50 cases in a block of 100 primed cases, and set my seating die to deliver a cartridge OAL of 1.140" which is the max for this caliber. Just as I had hoped, with this OAL the straight wall of the bullet was still sligthly protruding above the case mouth, so I could add a .003" taper crimp with a Lee factory crimp COLLET die. (Remember, this is a bottleneck case, and NOT a straight wall!!) So I get the seating die set up, and start seating bullets. Once again, I start getting variability in my cartridge OAL.
Whiskey Tango Foxtrot???
This is really starting to bug me, and I grab another case, and seat the bullet. For some strange reason, the seating pressure is really low, and the cartridge OAL is all of a sudden 1.112"!! :angryvillagers: I try 4 more cases, get 4 more light seating pressures, and an OAL of 1.112" :hmm: Then I notice that in my distracted state, I had gone down the left side of the load block instead of across it, and had loaded up 5 rounds WITH NO POWDER IN THEM!! What?? With no powder I get an OAL of .030" LESS??
About that point, it dawns on me that the only variable that has changed is the powder in the case, and I come to the conclusion that I must be compressing the powder to make up for the difference in seating pressure. Once I realize this, it THEN occurs to me that because of the pressure of the compressed powder in the case, I am getting DIFFERENT OAL's that are PROPORTIONAL to the seating pressure.
After some additional fiddling around, I come to an even more unsettling discovery. The OAL is PROPORTIONAL to the SPEED of the press handle!! A quick press stroke procuces a longer OAL that a slow and deliberate press stroke.
Unsettling discovery #2, consistent with #1. Two quick press strokes produce a shorter OAL than 1 quick press stroke.
Putting all this together, what appears to be happening is that the compressed powder is acting like a spring, and keeping the bullet higher up in the case that what you would get with an empty case, by a whopping .030"!! To make matters even more fun, this compression appears to be time dependent, so the longer it takes to seat the bullet, the more the spring effect of the powder goes down, along with the OAL.
From a purely "FEEL" standpoint, it became clear that 2/3rds to 3/4 quarters of the seating force was the pressure of compressing the powder, and once I figured this out I could "double tap" the seating on a hard seating bullet to get the cartridge OAL close to 1.140" almost every time.
About this time I recall a similar peculiar instance with reloading my 50GI cases with a measly 8.0 grains of Herco for the +P load, and getting similar OAL variations. In this case, there appeared to be PLENTY of space left in the case, but a Speer 300 grain 50 caliber Gold Dot apparebntly took up more space that I thought. A that time, I had surmounted that problem by using a slow, deliberate press stroke, without realizing that i was working with a compressed powder charge.
Obviously, this problem/phenomena will be extremely dependant on thre things:
The exact weight of the powder charge. There will be some statistivcal variations here.
The exact volume of that cartridge case. There will be some statistical variations here.
The amount of free air in the settled (but not compressed!!) charge. Obviously, a flake powder like Herco will have more entrained air than a fine grained powder like AA#9, so it can be compressed somewhat further wiout this weird spring effect taking over.
That being said, however, it would appear that if you start getting different cartridge OAL's after locking down your seating die, you may be working with a compressed powder charge, even though your manual isn't telling you that your are in this zone!!
So be safe out there, and keep your eyes open for this situation!!
Last edited:
, and the word I got third hand was that Speer's defense ammo was running a tad too hot, so they reduced the size of the primer hole to jury-rig it. I could not believe how much pressure it took to resize a Speer Lazy-S case, and after I found this primer hole information out, I could not believe that my decapping pin had hung in there and not broken while it was opening up the primer hole by a good 10 mils with simple brute force. Now I drill out the Speer brass primer hole with a .081" (#46) drill to make it equivalent to the Winchester brass.
