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Old February 21, 2012, 09:01 PM   #1
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Bullet Type and OAL

I'm a newbe and I just bought 100 each 9mm Remington 124gr FML RN and 124gr JHP as something to get my feet wet. I'm using Ramshot True Blue for powder. My question is OAL, I looked in my Lee guide for 124 gr and all they show is jacked for true blue which has OAL of 1.145. So if setup fort FML RN with OAL of 1.145 and then switch to JHP do I keep the same OAL?

The Lyman pistol and revolver guide has a 125gr JHP with OAL 1.075 so that's .067 difference. From what I have read about 9mm if you reduce the OAL by even a very small about you can really increase the pressure. I have to say I'm confused.
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Old February 21, 2012, 09:14 PM   #2
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What determines pressure is the bullet seating depth. So to get the same pressure as the load in the manual, use the same bullet and set it to the same depth. But life isn't ever that easy.

Since you aren't using the same pistol as the load was developed in, I always check a couple of things first. Will your loaded round chamber without the bullet hitting the rifling? I make up a dummy round and check before loading.

If the round will chamber at that OAL, calculate if the seating depth for your dummy round is the same as the load in the manual. You need to know exactly what bullet they used (not just weight and bullet type). I find lots of good data here. You also need to check to see if they will fit in your magazine.

If you need to seat deeper (shorter OAL, greater seating depth) then you will want to back off the powder loading. If you seat longer, you may need to increase powder loading. One of the reasons I like the Lyman manual is they list the actual bullet used. Of course the Nosler, Sierra, Hornady, etc. manuals only use their own bullets. This is why having several manuals is a great idea.

But knowing that changing the seating depth changes the pressure is a good starting point.
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Old February 21, 2012, 09:43 PM   #3
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The COL will depend on the bullet profile, the amount of space the bullet takes up in the case effects pressure.
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Old February 22, 2012, 12:07 AM   #4
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Yea, what jibjab says. The bullet shape will determine the seating depth. You may be able to find the information you are looking for in the forum buy doing a search for the bullet you are loading. You can also call the manufacture and see if they have any info about the bullet you are loading (some do some don't) or some of the loaders here may share. Some will and some won't, don't take it personal if someone will not share their recipes it has more to do with liability than spite. Most here have a lot to contribute as info goes and most if not all are pretty good at this, they been at it a long time. I think Ricard Lee has a second edition book on reloading that covers a lot of stuff if you happen to run across it look inside and see if he has something for you in there.
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Old February 23, 2012, 07:32 PM   #5
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Go to their website and download their reloading manual.
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Old February 23, 2012, 11:49 PM   #6
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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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Old February 24, 2012, 07:58 AM   #7
Don P
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BDS-THR right on the money. I just changed all my dies from 3 hole turret to 4 hole turret and had to adjust all dies for the new bullets received. I had to reduce my 9 mm OAL by .020 for the round to chamber from my previous bullets used. I learned this the hard way from my next to last bullet order, Did not do as BSR-THR stated and had inaccuracy/key-holing so all my efforts were a waste of time because of problems with the ammo not to mention the components used to make ammo that at best hit what you aimed at 50% of the time. I make my OAL as long as can be with the round chambering with the familiar sound of thunk. Just what I do.
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Old February 26, 2012, 09:49 AM   #8
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I measure the OAL of both bullets and adjust cartridge OAL of the new to match the case mouth to bullet base measurement/calculation of the old. Also, to someone else'a point, I make up a dummy round to check seating in the chamber before loading hundreds of rounds. Wasn't smart enough to do that twice (slow learner).
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