More from Cousin Wallace:
Loaded up 4 different loads and grabbed 3 different carbines and sallied forth to the range this afternoon. Set up the chronograph and stapled three targets up @ 100 meters. ( would have prefered 100 yards but it was still a good test).
Temp was about 45F but the winds were light so it was a tolerable day. Skies were mostly overcast which was idea for chronograph use. The chrono never missed a shot and worked to perfection. All 3 carbines were also 100% in function which is a rare occurrance. Each was fired from the bench for 5-shot groups, fed from the magazine.
All the carbines shot like......carbines. They will never impress with accuracy but they served their intended purpose and that was to enable a soldier to have a light weight weapon easier to hit with than a .45 calibre pistol. Smallest 5-shot group was 3.5" and the largest just over 9". A couple of the carbines averaged just over 5" utilizing all 4 loads, the third carbine was around 7". Though that doesnt sound impressive, all did stay on the paper and would have hit a jap in the chest provided the shooter did his part.
Best accuracy ( and consistency according to the chronograph ) came from a surplus ball powder ( WC820 ) which I have also discovered works wonderfully well in .44 Magnum loads. H2400 and IMR4227 were also tried and functioned well but neither delivered as good accuracy as the WC820. IMR4227 was more erratic with wider velocity spreads and the worst accuracy. All loads used Wolf small rifle magnum primers but cases were of mixed headstamps. I really dont think mixing cases makes a heck of a lot of difference in accuracy in these carbines....certainly wouldnt hurt though. I just had some that I wanted to use up and will separate headstamps when I get around to loading a batch at a later date.
Since the carbine case headspaces on the mouth of the case, trimming all of the cases to a tad below max length ensures they will chamber fully. Let the cases get past max length and you can expect failures of the bolt to fully lock into battery. I check all cases after sizing and before flaring the case mouths. If they do exceed max length, I only trim they no more than .005" below max. I hate trimming cases but it is a necessary step.
Anyhow, carbines are fun to plink with, just dont expect too many "X's" on the target range!