Oal for 9mm

[ezbobdad]

I think this all is making sense. Thanks for all the help. Don't hesitate to keep talking about anything in reloading because I think this is great. You guys are awesome.

[harkamus]

You want to go as long as possible without engaging the rifling where you can still insure jump gap. Always remember that the shorter you seat the bullet, the higher the pressure will be upon ignition. Pressure = force divided by area. Decrease the area (internal volume of the cartridge) = pressure will increase.

[painter]

You want to go as long as possible without engaging the rifling where you can still insure jump gap. Always remember that the shorter you seat the bullet, the higher the pressure will be upon ignition. Pressure = force divided by area. Decrease the area (internal volume of the cartridge) = pressure will increase.

That is true, but if you decrease the charge proportionately to the change in OAL, or seating depth, the pressure doesn't rise.

[laserdoc]

OK I have a question,,,,,, my push test was 1.09 and with .015 subtracted it gives me 1.075. Seems that 1.069 to 1.070 is better on the plunk test. With all this talk of the OAL what is the min  OAL
9 mm  115 grain LRD bullet

[harkamus]

You want to go as long as possible without engaging the rifling where you can still insure jump gap. Always remember that the shorter you seat the bullet, the higher the pressure will be upon ignition. Pressure = force divided by area. Decrease the area (internal volume of the cartridge) = pressure will increase.

That is true, but if you decrease the charge proportionately to the change in OAL, or seating depth, the pressure doesn't rise.

Also true, but there's a limit to how much you can do this and still have the gun cycling properly. How much will depend on which gun, what components, and what power factor.

[harkamus]

OK I have a question,,,,,, my push test was 1.09 and with .015 subtracted it gives me 1.075. Seems that 1.069 to 1.070 is better on the plunk test. With all this talk of the OAL what is the min  OAL
9 mm  115 grain LRD bullet

It depends on what your rule of thumb is. If your push test yields an over length of 1.09, meaning at 1.09 the projectile engages rifling and at 1.08, it spins freely, and you subtract .015 to get 1.075, I would of course try to get every cartridge length as close to 1.075 as possible. My min would be 1.072 and my max would be 1.078. It depends on gun.

My over length is 1.099. So after subtracting .015, I get 1.085 rounding to the nearest 5th. I will do my best to keep the measures consistent, but at the same time if a cartridge measures 1.095, I'm not gonna pull it and do it again because it's within my specs. To me that is the max length I'd allow, but I have to be bleep sloppy to get 1.095 when I'm aiming for 1.085. I also would not pull a cartridge if it measured to be 1.080, because that's ~.02 shorter, and there are folks that will load to .02 shorter. I just want tighter tolerances so I go with .015. This is for range shooting and I measure every single cartridge if I'm not lazy, or every third cartridge if I am lazy.

If I shot competition, I would tighten the tolerances to +/- .002.

Those were all hypotheticals for my reloading. Generally, they're already +/- .002.

[painter]

OK I have a question,,,,,, my push test was 1.09 and with .015 subtracted it gives me 1.075. Seems that 1.069 to 1.070 is better on the plunk test. With all this talk of the OAL what is the min  OAL
9 mm  115 grain LRD bullet

Anything below 1.00 would most likely be too sort to feed reliably.

Also true, but there's a limit to how much you can do this and still have the gun cycling properly. How much will depend on which gun, what components, and what power factor.

Yes, but...

The only limiting factor will be an OAL that prevents reliable feeding. If the load is adjusted correctly the pistol will still cycle as if published data was adhered to.

[laserdoc]

So if my calculated OAL is the 1.075 and say I load them at 1.070 do I need to drop my powder charge if at first I stated to use 4.4 gr.

[harkamus]

So if my calculated OAL is the 1.075 and say I load them at 1.070 do I need to drop my powder charge if at first I stated to use 4.4 gr.

Dunno the bullet nor the powder brand to say, nor what you started with before loading. I'm inclined to say no, but that's just me. I'd work up charges before blindly trying a certain charge.

[johnnyrees]

So if my calculated OAL is the 1.075 and say I load them at 1.070 do I need to drop my powder charge if at first I stated to use 4.4 gr.

Dunno the bullet nor the powder brand to say, nor what you started with before loading. I'm inclined to say no, but that's just me. I'd work up charges before blindly trying a certain charge.

plus one Hark,I just thought I'd throw in the fact that the oal will probably be different every time you change bullet style and weight...hence charge etc will change...aaahh the reloading adventure

[laserdoc]

So if my calculated OAL is the 1.075 and say I load them at 1.070 do I need to drop my powder charge if at first I stated to use 4.4 gr.

Dunno the bullet nor the powder brand to say, nor what you started with before loading. I'm inclined to say no, but that's just me. I'd work up charges before blindly trying a certain charge.

plus one Hark,I just thought I'd throw in the fact that the oal will probably be different every time you change bullet style and weight...hence charge etc will change...aaahh the reloading adventure

Sorry, I'm using HP-38 and 115 gr. LRD from Missouri bullets. Gun is my cz 75 compact . I just pulled 4.4 out of my hat. Was planning on starting at 3.8 and working up 0.2 grains at a time . I believe 4.4 is mid anyway.

[Added a decimal place. ]

[painter]

So if my calculated OAL is the 1.075 and say I load them at 1.070 do I need to drop my powder charge if at first I stated to use 4.4 gr.

If you have data at 1.075 then I would not adjust the load.

I would start at the starting load and work up as always. A .005 difference would be very difficult to calculate, much less measure, a proportionalized load.

While some keep tolerances to less than +- .005 that figure is not out of the realm of reason.

[Wobbly]

OK I have a question,,,,,,  With all this talk of the OAL what is the min OAL

The load recipe determines the Min OAL out of concerns for safety.

 

[Wobbly]

Don't hesitate to keep talking about anything in reloading because I think this is great. You guys are awesome.

Really now. You've got to set yourself some higher standards !! 

 

[laserdoc]

Thanks Richard!