How important is O.A.L. 9 mm

[pool67]

I am having a hard time keeping my o.a.l. of 1.125, i am getting 1.118 to 1.126 and i don't think the case length should effect o.a.l. I am using
115 grain fmj with mixed 9 mm casings.
THANKS GUYS

 

[jblomenberg16]

It may be there are some inconsistencies in the bullet shape that mean your seating die is seating each a little differently.


Bullet set back is important on many calibers, especially if you are close to maximum load. In this case the set back is pretty small and probably insiginificant.

If you are running a mild load I think you should be ok. You might shoot a few at the lower AOL to double check for pressure signs just to be sure.

 

[squirrelhntr]

As long as the round chambers in your pistol I don't think the .008's of a inch will make a difference. IMHO.

 

[XtremeVel]

The OAL is important. You say you're looking for 1.125 and the deepest you are seeing is within .007 of that... As long as that's all you're seeing, I wouldn't worry about it as long as your die and seating stem are locked down.

I often times see more variance than that when using FMJ-FP's. The ones I see that check shorter have an slightly larger flat on them... I see this even on more expensive jacketed bullets such as the Hornady 124 gr FMJ- FP for 9mm or 230 gr FMJ-FP for .45 ACP. Look at your bullets and see if you see any little inconsistencies.

You are right... What you are seeing has nothing to do with your case length.

 

[NIFT]

SAAMI shows overall length of 1.000" minimum to 1.169" maximum.
Overall length of a particular 9mm cartridge depends of the bullet shape (and weight.)

One of the best ways to determine a good overall length is to find some top quality factory ammunition of the same or very similar bullet profile and weight. Measure that cartridge's overall length, compare it to the SAAMI specs and reloading manual recommendations. Overall cartridge length of reloaded handgun rounds will very a few thousandths of an inch due to fluctuations in bullets and minute deforming by the seating plug in the die.

The more important dimension for reloaded semi-auto handgun ammunition is the taper die crimp, because these cartridges headspace on the case mouth. Undercrimping can cause feeding problems, and overcrimping can cause ignition and extraction issues.

 

[pool67]

I am using the start of 4.7 grains and the never exceed is 5.1 grains with HP38
i have tried 4.3 grains already and did not have any problems.

 

[BGDave]

Everyone is giving good advice. To put .007 in perspective. An index card on my bench checks .008 in thickness.

 

[U.S. Patriot]

Very important, especially in a high pressure cartridge such as 9mm. Just make sure you are staying at or above the recommended OAL, and do not load above the max charge. You can always increase or decrease your charge .1 grains until you find the sweet spot. I'm using Winchester 115 grain FMJ bullets and the bullet shape is inconsistent, so there is some variance. Same with my case length. I normaly average a variance of .010" in a batch. I load to a longer OAL then what the load data recommends, which gives me a safe leeway. I'm also loading .1 grains under max charge as well.

 

[downrange72]

I run 147 gr. I am now running the upper end. I had a kaboom and learned my lesson with a shorter OAL (running them around 1.005 at that time, official Dx was compressed load from S&W). 1.125 is probably good. I run 1.13-1.15 now without any issues.

 

[jbrooks19]

I'm using winchester 115gr FMJ bullets, Winchester primers, and 4.5gr Bullseye powder, My OAL is 1.14-1.15-1.16.. I shoot out of a Glock 19 and they function perfect.


Good luck fellow reloader!

 

[Broom_jm]

Depending on what powder you are using, and how close to a maximum charge you are, seating as little as .010" deeper CAN take a safe load and make it "iffy". If you're using jacketed bullets from a reputable maker, you shouldn't see that much variation. In your situation, I would perhaps seat out a little further, such that your average is closer to your intended 1.125" OAL. You're better off to be .010" over than under, that's for sure. Within reason, a bullet seated long will just fail to cycle well, whereas one seated too short (and maybe sets back a little) can get you into trouble, fast.

 

[jbrooks19]

Agreed!

Depending on what powder you are using, and how close to a maximum charge you are, seating as little as .010" deeper CAN take a safe load and make it "iffy". If you're using jacketed bullets from a reputable maker, you shouldn't see that much variation. In your situation, I would perhaps seat out a little further, such that your average is closer to your intended 1.125" OAL. You're better off to be .010" over than under, that's for sure. Within reason, a bullet seated long will just fail to cycle well, whereas one seated too short (and maybe sets back a little) can get you into trouble, fast.