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Old January 28, 2012, 09:38 PM   #2
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. FYI, most jacketed/plated RN bullets have worked well for me at 1.125"-1.135" OAL in various pistols.

4. Then conduct powder work up using Ideal OAL and published start-to-max load data. 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 - http://www.midwayusa.com/product/493...hts-605-grains

Not all factory/aftermarket pistol barrels have the same groove diameter, leade length, rifling type as used in the test barrels to develop load data that result in different high pressure gas leakage and may require different powder charges to produce same chamber pressures. If you do not have a chrono (or can't use one because you are shooting at indoor ranges), I typically use consistent shot group sizes as indicator of consistent chamber pressures without exceeding published load data (when shorter OALs are used, I often use a slight buffer headroom near the max load data - maybe .2-.3 gr less).

Variations in the published load data are often due to variations in reloading/testing components (i.e. type/nose profile of bullet nose and how deep the bullet base is seated inside the case neck, etc.).

Starting with the published start charge (or 10% below max), 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 (usually 2-3 powder charges will stand out). On range trip #2 and subsequent trips, I will verify most accurate powder charges with 5 round shot groups at 7-10-15 yards (Typically, I will use 3 consecutive range tests to verify the accuracy of particularly accurate loads).

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.

Some large flake powders like Unique, Promo, etc. may not dispense to .1 gr consistency when using powder measures. Do not get discouraged by this as I still get accuracy from these powders even with .2-.3 gr variations. Go by the shot group sizes.

Last edited by BDS-THR; January 28, 2012 at 09:43 PM. Reason: corrected link for check weights
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