O.A.L changing during reloading

[boatdoc173]

Hello

 

My  550c for  9mm reloading has been consistent for years.  I have noticed lately that the solidly locked-in bullet  seating die  is moving just enough to change  my O.A.L.  by  -0.001--0.003 every so often(. Often enough that I find my self taking  time out away  from  reloading the verify OAL every 500-1000 rounds.) I only use my Dillon dies and their lock rings. , I am baffled as to how the OAL  can change  when the lock ring is locked  down tight and the die  has  zero play 

 

anyone else had this happen?

 

any ideas on how to stop this?

 

 the first 50,000  rounds were loaded @ 1.140" to fit into a fussy CZ  A01.   NO issues were noted when I made  them. it  was set it--forget it  2020-2022

 

 the  new need to check OAL  way too often is more than annoying.

 

thanks in advance for any insight  ad help offered

Edited December 14, 2023 by boatdoc173

[GrumpyOne]

Clean the die. Stuff gets built up in them and causes some of these issues, but .001 isn't anything to worry over.

[Maximis228]

Brass and projectiles can have larger variances alone than what you mentioned above. Depending on your projectile of choice, you may see a larger variation. 

 

Are you continually drifting in one direction? That could show that a die is moving on you. I would witness mark your dies and lock rings with the toolhead with a paint pen. 

 

My current 9 major ammo I'm loading has an OAL range of 1.164 - 1.170. No issues at all with that spread. 

 

Edited December 14, 2023 by Maximis228

[ddc]

The only time I see an OAL variation of 0.001" is when I compare a maximum of two cartridges; then I might get lucky.

 

For any reasonable sample size I'm happy if the variation is around 0.005".

 

For example my target OAL for current 9mm load is 1.125" to 1.130" and even at that I might see a few that exceed that spread.

[Nickb45]

I don’t worry about anything unless it’s more than +-.005. 
if you’re shooting for less than .001 variance calipers are not the correct tool for that measurement. 

[Farmer]

Are you saying .001-.003 Longer? If the die is tight I would check shell plate or tool head. If it’s shorter check for die crud or bullet mash. Have seen up to .005 from a tight fit and mashing the bullet nose especially on HP’s. Like the others have said under .005 is gtg unless you’re OCD. 

[Sarge]

Mixed brass will vary wildly. If you are sorting then I’d guess maybe not enough lube to even distribution. 

[shred]

Most likely bullet profile, especially if you have a round-nose seating stem in there.

 

[boatdoc173]

great answers. thoughtful and to the point  guys. THANK YOU. I was baffled.  thought about it all night too

 

I will address some of the ?  in my post below

 

 I think  the brass  length varying  is part of  the issue.

 

I clean my dies regularly.

 

I do NOT sort brass by name brand though.  I sorted out all of the brass that caused issues when priming in the past.

 

I use hornady one shot regularly. that said , using a plastic baggie to spread the one shot around might leave  some cases lacking in enough lube.

 

I am very glad that  you   guys have  posted that such small variances do not make reloading or shooting  dangerous( pressure increases).  my variance is  0.001-0.003  shorter   than the desired OAL. 

 

I use RMR  .355"  124 gr    FMJ round nosed  bullets and my die has the round nose  tip installed.

 

again, much thanks for the  thoughtful replies

Edited December 15, 2023 by boatdoc173

[boatdoc173]

@Nickb45--what would you  use for the best measurement outcome?

 

I have noticed that my  calipers ( digital from dillon when I bought my initial reloading  supplies)  has to be  zeroed every time .  After  reading the  replies   so far, I am guessing that the calibers might contribute to my issue..   exact measurement depends on consistent placement of the cartridge  in the calipers when measuring. a more reliable way to measure  OAL  would make a difference

Edited December 15, 2023 by boatdoc173

[Nickb45]

I have a set of Brown and Sharpe dial calipers on my reloading bench.
For most tolerances calipers are fine, a micrometer that goes to 4 decimal places will be better… but totally unnecessary for reloading pistol ammo. 

[HOGRIDER]

10 hours ago, boatdoc173 said:

@Nickb45--what would you  use for the best measurement outcome?

 

I have noticed that my  calipers ( digital from dillon when I bought my initial reloading  supplies)  has to be  zeroed every time .  After  reading the  replies   so far, I am guessing that the calibers might contribute to my issue..   exact measurement depends on consistent placement of the cartridge  in the calipers when measuring. a more reliable way to measure  OAL  would make a difference

@boatdoc173  I have also found when loading my standard PD 124g JHP, that I can rotate the finished round and get different OALs!  This is using a Mitutoyo 0.0005" Resolution digital caliper.  I attribute this to the slight variances in the hollow point forming of the bullet; plus my Redding micrometer seating die is seating off the ogive.

 

But I can still get a "standard" variation of +/-.002" once the press has filled the shell plate.  Just have to make sure the round is in the "sweet spot" when measuring.......

 

 

 

[boatdoc173]

@Nickb45--thanks for the info

 

@HOGRIDER--I agree.  that is one cause for variation. brass and bullet size and shape  being others

 

. My concern  was the potential for an  increase in pressure when a cartridge  would shorten down to  1.137, 1.136, 1.135" even.

 

I  did shoot a couple of the  1.136"  rounds yesterday and as predicted  by our members, the ammo shot  fine.

 

 

Edited December 16, 2023 by boatdoc173

[Farmer]

@boatdoc173 If you’re shooting minor loads you would have to seat the bullet about .025” deeper to bump the pressure and at that it isn’t going to get you necessarily into a danger zone. Maybe a bit hotter but generally nothing to worry about. Now if you’re at major that’s a little different story. 

[boatdoc173]

@Farmer--just plinking  loads. not loaded too hot. however with titegroup, the powder charge range is very tight.

 

thanks for the reply.it is reassuring

[IVC]

I wish my variance was as little as 0.001 - 0.003.
 

Coated bullets and mixed brass even in principle won't produce that level of consistency - the bullet is seated by pressing off-center, towards the ogive, so the tip of the bullet is not touched and any deposit (coating or lead below) will change the OAL. Look at the bullets before you load them and you can see with naked eye that the tips are a bit off. Also, it's easy to measure the length of each bullet and you'll see variability. Note that this doesn't even mean that the base of the bullet is seated at different depth, the depth could be anything. But it will be close enough...

 

Brass is another issue. I'm pretty sure that the press won't hold the brass within 0.001 at the seating die. Maybe at the sizing die, if overcammed, but not at other stations. 
 

You don't have a problem

[boatdoc173]

thanks  @IVC