Blue Dot + Hammer Hunter for Ruger LC Carbine

General reloading

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whacamole
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Joined: 03 Dec 2022, 22:15

Blue Dot + Hammer Hunter for Ruger LC Carbine

Post by whacamole » 03 Dec 2022, 23:11

Figured I'd share my first attempt at reloading the 5.7x28mm. I used QuickLoad to narrow down powders and establish a reasonable initial guess for minload/maxload.

Firearm: Ruger LC Carbine (16.25" barrel)
Brass: American Eagle once-fired, FL sized using Lee die, trimmed to 1.130"
Primer: CCI 400 Small Rifle
Propellant: Alliant Blue Dot
Bullet: Hammer Hunter 35gr, seated for COAL = 1.455"
Chronograph: Magnetospeed

Code: Select all

gr	 fps
4.5	1792
5.0	1939
5.5	2107
6.0	2326
6.2	2399
6.4	2394
6.6	2538
6.8	2567
7.0	2593
Primers looked "normal", which is to say they all cratered like factory AE rounds do, even at the lower loads. No piercing. However, the primer strike was off center by 0.010".

Energy for the 7.0gr load at 2593 fps is 522 ft-lbs. It also made a really cool contrail (environmental conditions being just right).

As a control, six rounds of factory AE 40gr were also fired, yielding an average of 2028 fps with an SD of 19 fps.

By adjusting QuickLoad's "Ratio of Specific Heats" for Blue Dot from 1.2201 to 1.25 and correcting the temperature to reflect actual conditions, I was able to match predicted fps quite well to measured fps across this range of loads. Assuming this is an acceptable way to anchor QuickLoad's model, the pressure at 7.0gr during this test should have been about 35000 psi, which is max CIP pressure minus 30%. If the model is accurate, a maxload of 7.0gr should not exceed max CIP minus 20% even at 122F powder temperature, and a 0.2gr loading error for an actual charge of 7.2gr should reach only max CIP minus 15%.

Several of the handloaded rounds failed to fire. Inspection of these rounds with a Sheridan Slotted Ammunition Gauge revealed that they did not protrude above the middle step of the gauge, whereas other rounds did. This might have resulted in the primer being slightly too far away for full firing pin effectiveness. Additionally, some rounds were found to bind slightly on insertion into the gauge, possibly due to inadequate deburring and/or malformed shoulders. This might have resulted in rounds being slightly out of battery and then moving forward during the firing pin strike, reducing its effectiveness. Flawed rounds were discarded and a note was made to check cases more closely during the resizing and trimming processes.

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