9mm OAL question

[scouty]

Hi all, Just starting my reloading experience. My Lee and Lyman manual says OAL for 9mm is 1.169. I checked a Winchester 115g RN, I came up with 1.163. I'm sure I'm reading my dial caliper correctly. Any insight on this. I did check several cartridges.

[That'll Do]

1.169" is the MAXIMUM length that a 9mm Luger cartridge can be.

Most reloading manuals will have a COL shorter than the max. For example, I load my 9mm to 1.135" COL. Different strokes for different folks. It largely depends on what kind of bullet you are using.

[scouty]

Thanks for the reply. after checking my manuals a little more I see the Lee gives a min. OAL and I'm assuming the Lyman is giving a max OAL. as long as the cartridge chambers and I'm not over or under Min/Max OAL am I safe? And withno dbl loads.

[D. Manley]

Hi all, Just starting my reloading experience. My Lee and Lyman manual says OAL for 9mm is 1.169. I checked a Winchester 115g RN, I came up with 1.163. I'm sure I'm reading my dial caliper correctly. Any insight on this. I did check several cartridges.

Manuals are all over the place with OAL...some just list the maximum, some minimum and some actually have a specific recommendation for their particular brand of bullets such as, the Sierra and Hornady manuals. Lyman is usually a reliable guide for real-world applications but even that is not engraved in granite.

IMO, with a 115 grain FMJ in 9MM you have a lot of latitude. Unless you are loading at or near maximum levels I tend to load *most* bullets in the 1.135 to 1.142 range. I do load a few target-level loads even shorter with some bullets but you should be fine with any RN 115 at 1.135/1.14. Personally, I'd forget the maximum length OAL except for hotter loads which needs the additional safety factor. Loading "long" with mild loads doesn't help to make consistent pressure/velocity readings.

[Cajun]

The 1.169 is the Maximum overall length. Most of the factory rounds I have measured are in the 1.58 range.

The bullet selected is critical in overall length. A lighter bullet or hollow point will need a shorter length because of a shorter bullet. The name of the game is to seat the bullet with the same depth in the case. If you seat too deep, the pressure can rise sharply.

[SL1]

The maximum OAL is really set by what will fit in your gun's magazine and not get the bullet jammed into the rifling. The distance to the rifling is usually not an issue in pistols, so maximum OAL is typically limited by what will fit in the magazine.

Actually, different bullet nose shapes need different cartridge overall lengths to FEED reliably in a gun, and differences in magazine lips, feed ramps and chamber mouths make that reliable OAL for a particular bullet vary somewhat from gun-to-gun.

The OAL listed for a particular bullet in a loading manual is usually the length that was used to generate the pressure data. Reducing that length will increase the pressure, so the length used to generate the pressure data is often referred to as the minimum length FOR THAT DATA. But, shorter lengths can be used if the powder charge is reduced accordingly. The problem is that the reduction in charge weight the is appropriate for a particular reduction in OAL requires some measurements and calculations that are not explained in most reloading manuals.

Small changes in OAL can make unexpectedly large pressure changes in small pistol cases like the 9mm Lugar. How much depends on the bullet, powder type and charge weight. At the extreme, shortening the OAL by as little as 0.030" can produce a pressure change from 28,000 CUP to 62,000 CUP, according to pressure test data produced by Speer and printed on page 349 of their #10 manual. Calculations with programs like QuickLOAD verify that pressure increases that extreme are possible.

So, typically a reloader will start at a OAL that is similar to the OAL of factory ammo with the same bullet nose shape that feeds reliably in HIS gun. Start with the "start" charge and stay above the OAL listed for that data, and you should be OK. Going to a longer OAL to improve feeding will not be a safety issue (unless the chamber throat is so short that the bullets reach the rifling). Going to a SLIGHTLY shorter OAL than the minimum listed for the data while still using the start charge USUALLY will not cause a problem, but increasing the charge with the shorter OAL is uncharted territory as far as the pressure testing data is concerned. IF you need to do that to get reliable feeding, ask here for some guidance, and one of us will explain how to estimate the pressure increase caused by the OAL decrease, and the charge reduction needed to compensate for that.

Auto-loaders are the most finicky types of guns to hand-load, because several factors need to be balanced to make the rounds feed and extract reliably while still producing safe working pressures. One issue that becomes critically important is the grip of the case mouth on the bullet. If that is not tight enough, then the bullet can be "set-back" when it is slammed into the feed ramp, making the OAL shorter than what you loaded it to when the that cartridge is fired. That example from the Speer manual applies in either situation (whether you intentionally made the round 0.030" shorter than the data called for or it was unintentionally reduced by 0.030" by impacting the feed ramp).

So, it is best to first make a few dummy rounds to check bullet grip, and not load primers and powder until you have tested YOUR die setup with the dummies. To do the test, measure the OAL of a dummy with your caliper, then load it into a magazine and load a factory round on top of it. Insert the magazine into the pistol, hand-feed the factory round into the chamber and fire it to auto-cycle the dummy into the chamber. Then carefully eject the dummy and measure its length again. If it is more than a few thousandths shorter, you need to address your die setup before loading powder. You should do that with a few dummies, and try it again if you change case headstamps, especially if the new cases have thinner walls in the mouth region.

SL1

[scouty]

Thanks SL1, You guys are very helpful!!!!

[Cloudpeak]

So, it is best to first make a few dummy rounds to check bullet grip, and not load primers and powder until you have tested YOUR die setup with the dummies. To do the test, measure the OAL of a dummy with your caliper, then load it into a magazine and load a factory round on top of it. Insert the magazine into the pistol, hand-feed the factory round into the chamber and fire it to auto-cycle the dummy into the chamber. Then carefully eject the dummy and measure its length again. If it is more than a few thousandths shorter, you need to address your die setup before loading powder. You should do that with a few dummies, and try it again if you change case headstamps, especially if the new cases have thinner walls in the mouth region.

To add to SL1's very fine post--- When first starting, I load some dummy rounds and cycle them several times them by releasing the slide stop, measuring COAL each time through to check for setback. You will be taper crimping your rounds but this is just to remove the case mouth bell so the round will chamber. It's not like a roll crimp that is used to retain bullet position.

You can use your barrel, removed from the pistol, to check for proper chambering. Drop a factory round in to see how the round fits and then a dummy to make sure it looks the same. The case head should be flush with the barrel hood. Different pistols can have different chamber lengths so this is a custom fit kind of thing.

Bullet setback is a function of the sizing die and expander plug. When I encountered setback, I chucked the expander plug stem in a drill press, spun it up and used fine sandpaper and "Scotchbrite" pads to reduce the diameter slightly and then tested for setback again. If I still had a problem, I'd take a bit more off (we're talking increments of .001" at a time). When I could cycle a dummy round 5 or 6 times without setback, I called it good to go.

I don't separate brass by headstamp and seem to get along just fine but perhaps I should. I'm loading lead bullets sized to .3575" and I can always see the base of the bullet bulging the case slightly so felt that I was in good shape as far as the setback possibilities are concerned.