This is an informational post for anyone looking to run reduced load cast boolits in your AR pistol caliber carbine (PCC). Let me start out by saying I am not an engineer or have a degree in physics. I’m just your average Joe. These loads are the results of my experiments using these powders and boolits in my PCC. Use caution as your results will differ from mine.
I started down the PCC road with an 8” barrel shooting commercially obtained 124 grain copper plated bullets. 5.8 grains Power Pistol is my chosen practice load for a Glock 19 pistol, producing recoil very close to that obtained with commercially loaded defensive ammunition. Out of an 8” PCC however, it runs over 1,300 fps and produces considerable recoil, especially with the combined bolt/buffer mass of 25 ounces slamming back and forth between the barrel face and back of the receiver extension. While this setup is a great defensive addition to a carry pistol, this much recoil is not optimum in a PCC used in competition. If you are into Steel Challenge or other PCC venues, minimizing recoil while maintaining the required minimum power factor (PF) is the goal. I chose a 16” barrel for two reasons; to avoid any NFA implications and the added weight of a longer barrel can help reduce perceived recoil. The benefit of using a reduced load and longer barrel will help mitigate some of the ‘muzzle jump and dip’ that one experiences with blowback firearms as well as enable you to generate enough velocity to reach the required PF.
Reduced load data is hard to find and by ‘cooking’ your own loads you run the risk of sticking a boolit in the barrel or worse. For powders, I used Bullseye, Unique and Power Pistol because they comprise the bulk of my pistol shooting. Instead of using jacketed or plated bullets I chose the Lyman 356402, 120 TC powder-coated boolit. I shot ten rounds of each of the three loads with the following results;
4.0 grains Bullseye, avg velocity 1312, SD 11.95
4.0 grains Unique, avg velocity 1213, SD 18.84
4.2 grains Power Pistol, avg velocity 1178, SD 13.3
I tried only these three loads to give me a starting point. They were fired from a Caldwell Lead Sled at 12 yards. The chronograph was 10 feet from the muzzle. Bullseye was the least accurate at that loading. Ejection was about 3 feet from the rifle. Unique was second in accuracy with one ragged hole slightly larger than Power Pistol and ejection 1 to 2 feet. Power Pistol was the winner in accuracy with a similar ejection distance though some rounds bounced off the shooting bench before landing on ground. Bolt speed was very slow with both Unique and Power Pistol and if you happen to be fast on the trigger the hammer may not be locked back at that point. I guess you could also run the risk of an out of battery ignition which is fairly common with 9mm blowback guns. When firing I could hear the bolt moving after the round had fired. None of the fired cases were covered in soot as it is my understanding this is an indication of an insufficient charge. Feel free to correct me if my assumption is incorrrect.
If I had to pick a winner it would be Power Pistol. Reducing the Unique powder charge below 4.0 grains may also increase accuracy but with the reduced bolt speed I don't think I'll try it. I may try a lighter recoil spring but I’d rather stick with the stock carbine spring. Since this lower receiver assembly does double duty as both a defensive ‘pistol’ and PCC rifle it would be one less thing to carry around and swap out.
If you’ve done similar experimentation I’d be interesting in hearing your results. Thanks for reading.
Mods, if I've posted this in the wrong forum, my apologies.
|
   
   
|
|
Reply With Quote
Originally Posted by 0802
