How important?

 

I pressed out 25 9mm rounds last night, looking for LOA of 1.090 and am getting ranges from 1.09X to 1.142.

 

I've seen a recipe for a 9mm round with an LOA of 1.142 so I think I'm good.

 

I still have to check them in our barrels (removed from firearms) and then Chrono them (thanks Harry).

 

My question, or concern, is really how far can I miss the mark of say 1.142 and still be OK.

 

I don't plan on missing, and once I get the press dialed in a little further, it shouldn't be an issue.

 

Just a noob reloader looking for reassurance...

Assuming your powder charge, primer & bullet selection, and brass are ok, you're probably fine from a safety point of view.

 

Some guns are finicky on OAL, some aren't.   If they end up not feeding well in your particular gun, I'd look first at a different bullet profile (round nose feed best, some guns have issues with SWC, HP, or other bullet designs), then at OAL.   If your loads are close to typical factory power factors, your recoil spring is probably ok.  If you go to lighter loads, you may also need a lighter spring...but that's not an OAL thing.

That's a pretty wide range for bullet seating. Double check you seating die for any dirt or grit. Additionally, your die should have come with 2 different seating stems. One is for a round nose or similar bullet, and one is for wad cutter type bullets. Make sure you are using the correct seating stem. That said, you are still within SAAMI OAL at your longest. What concerns me is the shorter OAL cartrigdes. By seating too deeply, you can create additional pressure issues as case capacity is diminished. You didn't say what bullet you are using, so hard to say if there would be a problem. For great information on relaoding recipes, go to the Hodgdon or Alliant websites. They will list starting and max powder loads as well as suggested OAL's for different bullets.

50 thousandths is kind of a lot, if you are at minimum starting loads it should be safe but you're probably going to have your velocities all over the place.

 

It's hard to say "how far off is too far" as that will depend on your gun and powder. If you're using a fast powder you'll have to be more careful, and if you're loading for an unramped 1911 (seems unlikely if you're working on 9mm) you'll have to be more careful.

Are you loading mixed brass? If yes, you will see a lot of variance, but 0.05 is more than I'd expect. I haven't loaded 9 in forever, but with mixed brass of mixed age in .40, I usually wind up with a spread of about 0.03 give or take.  If I sorted by headstamp on brass I knew the number of firings on, it shrunk dramatically and was much more consistent. 

 

The other possibility is that you suck at measuring. You'd be shocked how inconsistent you cna measure using calipers and a fairly pointy round nose like a 9mm.

 

 

The other possibility is that you suck at measuring.

LOL.

 

Idiot.

 

Yes, using mixed brass.

 

Xtreme copper plated round nose.

 

: )

I can't get extreme plated bullets to seat exactly the same and I use a single stage rock chucker.  It's in the bullet itself.  The round nose isn't the same on each one if that makes sense.

 

The bullet seating stem is curved to accept the round nose of the bullet so it really doesn't push on the tip. The round nose, not being uniform, fits in the stem differently making your seating depth change.

 

The bullets all weigh the same, and are very consistent in diameter - they are not, at least the ones I have, all the same length.

 

In the end,  I really don't get worried about a few thousandths of an inch.  

 

Ever put a caliper on factory ammo????

Using Rainiers plated 115gr 9mm, I seat at 1.140. It's all about what works in the gun you're reloading for. Max OAL for 9mm is 1.169. Not much holding onto the bullet at that point, but still within specs. As for the seating variance, that is WAY too much. My seating depth variance is .003 -/+

My seating depth variance is .003 -/+

I have to make allowance for the mixed range brass and, as much as it pains me, that I just might suck, as my friend Raz-O, illustrated. : )

 

When you think about it, the die is fastened and not shifting, so as long as I'm not short stroking the bullet head should set firmly.  One thing I noticed when me kid was pressing is that he wasn't firmly setting the primer in the pocket and that was affecting the COL, and in most cases rendering the round unusable and in the bucket to be pulled and reused at a later date.