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Old February 23, 2012, 11:49 PM   #6
BDS-THR
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Join Date: June 12, 2010
Posts: 474
You do not need to use the OAL listed on published load data as testing barrel fixtures (not real pistols) are used to measure chamber pressures and using published OALs WILL NOT ensure reliable feeding/chambering of finished rounds in your pistols.

Determining OAL should not be a guessing game and I use the following process for semi-auto loads whenever I use a new bullet:

1. Make sure resized cases drop freely into the barrel chamber. If not, adjust the resizing die to ensure the cases are resized full-length (bottom of resizing die almost "kisses" the shell holder/plate) and fall in freely into the chamber.

2. Determine Max OAL - Make a dummy round (no powder/primer) and perform the barrel drop test with the barrel out of the pistol starting with the SAAMI max OAL until the dummy round falls into the chamber freely with a "plonk" and spin without hitting the start of rifling. To determine the amount of taper crimp to return the flare back to flat, I usually add .020" to the diameter of the bullet (So for 9mm .355" diameter bullet, .375" taper crimp and for .356" bullet, .376" taper crimp).

3. Next determine Ideal OAL - Load the Max OAL dummy round in the magazine and manually release the slide without riding the slide with hand. Incrementally decrease the OAL until dummy round reliably feed/chamber. Depending on the pistol/barrel used, Ideal OAL that will work reliably will vary. If you are reloading for multiple pistols, use the Ideal OAL that will work reliably in all the pistols.

4. Then conduct powder work up using Ideal OAL (Regardless of the scale used, I highly recommend the use of check weights to verify the accuracy of powder charges to 1/10 of grain).

Starting with the published start charge (or 10% below max if start charge is not listed), load 10 rounds of each increment of .1-.2 gr in powder charge. If using shorter OAL than published/typical for bullet type, I will decrease my start charge by .2-.3 gr. For initial range trip, 3 rounds are shot at 7-10-15 yards and shot groups are compared to identify charge range that reliably cycled the slide/extracted cases while looking for accuracy trends.

Conducting full work up allows you to identify the most accurate powder charge for the particular bullet/OAL combination and lighter target/plinking loads that still produce accurate shot groups while reliably cycling the slide/extracting the spent cases.
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