I received permission to share this from the author.
This is a link to the original thread posted by Ranch Dog in the bryco-jennings-jimenezarms forum:
Original Post by Ranch Dog:
With the availability of small pistol primers back on my reloading shelves, I'm putting my load development work back into full swing for a number of firearms and cartridges. First is my "Mighty Mouse", a Bryco M38 chambered in 32 ACP.
After purchasing this pistol last year and being in the cast bullet design business, I took a chamber cast from this firearm along with those from all my BJJAs pistols and used the measurements from the cast to develop a bullet specific to these manufacture and model of firearms. In the process, I do not let my wishes interfere with what the firearm wants. You cannot go into this work saying a want an XX-grain bullet. You have to let the firearms throat/lead and magazine feed requirements dictate what is acceptable and even that is tempered by the center of lift and center of gravity of the projectile. The sum of this work is the diameter and weight of bullet. This used to be hard slide rule work but a friend of mine, Tom Myers, has made it easy with the software products he is developing for this specific purpose. Of the dozens of bullet designs I've developed, employing him for this work is money and time well saved. Each and every step taken in this process delivers a bullet that shoots as accurately as possible.
My TL314-70-RF bullet for the 32 ACP just happens to be the first mold I've received from Lee Precision. The bullet has a flat round nose of 72% meplat that is used to deliver as much energy as possible and it happens to weigh 70-grains when cast with an alloy that is a 95/5 (wheelweights/tin). It is air-cooled to help keep a low BHN (soft) so that it mushrooms well. Cast bullets use some for of wax or lube as a seal, my bullets use Lee's Micro-Bands in the design, so they can be tumbled in a tub with Liquid Alox. It is a very simple process and I then pass them through a .314 Lee sizer to make sure they are true.
I use Hodgdon's line-up of my reloading, having all the powders, but also use Alliant's Unique for my pistols when applicable as I inherited quite a bit of it some time back. In that my bullet weighs 70-grains, there was plenty of jacketed bullet data available so I settled into these three powders for my work: Titegroup, Unique and Universal.
I load from a Lee turret press which allows all the dies to be set on a turret plate. The press also uses the Auto-Index which advances a turret to the next position with each lever stroke. It is idea for loading pistol cartridges and the setup is not as complicated as a full progressive press. I do also have the Lee Loadmaster progressive press but do not use it for development work. The Lee setup also uses their Auto-Disk powder dispenser. The Auto-Disk uses fixed cavity disks to measure and charge each case. Measuring each charge on a beam/balance or electronic scale consumes too much time. From the available cavities, you select one that will deliver a charge slightly below the maximum charge for each powder. In the above table, the "Drop CC" is the cavity (they are calibrated in Cubic Centimeters) and the corresponding charge dropped for the given powder.
The 32 ACP (and 25 ACP) actually needs a special "Micro Disk" with Titegroup and Universal because of the fine powder and the small charges. In the image above, the powder hopper has been swung out of the way (gray transparent container) and the Micro Disk is being indexed on the proper cavity on the Auto Disk.
The image on the left shows the dies on the turret along with the powder hopper. I loaded up 25 rounds with each powder. Enough for 3 five-shot trigger exercises and one ten-shot string for the chronograph. The press really dwarfs the cartridge!
The initial load work was interesting. There is quite a difference between the published data velocity and the actual performance delivered from these blow-back pistols! The performance loss is significant! Remember that the published data uses pressure barrels to measure load performance. The same is true with factory ammo. What you see in print is not what you get with a non-locking action!
Titegroup held the highest velocity and the 7-yard accuracy performance of all the powders was mediocre at best. One of the issues of loading this cartridge is that the powder charge fills very little of the case. The powder density leaves a lot of empty space inside the cartridge. As the firearm goes through the rigors of movement and is finally held in the near horizontal for the shot, the powder is dispersed across the length of the case rather than being held against the primer for ignition. This creates large velocity differences between shots which translate to large groups on the target.
One method of correcting the load density issues is to use filler. The powder charge is dropped into the case and then filler is used on top of the powder charge. As the bullet is seated into the case, it compresses the filler which holds the powder against the powder. Most reloaders stay away from "duplex" charges because it complicates the pressure curve. It does provide uniform ignition reducing the velocity spread.
Tom Myers, mentioned earlier, is very versed in duplex loads and his reloading record software is one of the few that considers it. After reviewing my comments he suggested I try Cream of Wheat as a filler and start with a reduced charge. I wanted to use Titegroup, because of the velocity and accuracy, and it also fit Tom's requirements perfectly. The Auto Disk was dropping a charge that was 10% below Maximum which is a normal starting point in load work.
Using the same dispenser, but different cavities, I loaded up another set of cases for the work. First the powder was dispensed and then the Cream of Wheat was dispensed on top of the powder. My case now had a 101% density which means that they were slightly compressed, just enough to hold the powder against the powder.
The results were impressive! The new duplex load delivered much better velocities and the deviations in velocities cut the groups in half!
I'm set, I like this load and it makes the Mighty Mouse into an impressive shooter. It is very satisfying to take a firearm's loading all the way from bullet to a fully developed load. I've shot it enough to know that I can totally depend on it in any CC confrontation, God forbid that to happen please!
Here are my load and performance records from my TMT software.
"Give me a hard focus on the front sight!"
I may have to grow old, but I don't have to grow UP!