Cartridge Length Variances?

[moonzapa]

I am utilizing the following equipment and materials to handload 30-06 Springfield cartridges for my Winchester 70 Severe Weather rifle:

Forster Coax Loading Press
Redding Deluxe Die set (30-06)
Lee Factory Crimp Die (30-06)
Hornady 168 A-Max Bullets
Lapua new brass
IMR-4350, H-4350, IMR-4831, and Varget propellants
Federal GM210M primer

The new Lapua brass did not require trimming after full length sizing. The brass measured 2.4835" - 2.484". However, I placed each brass into my trimmer as a precaution. No discernable brass was removed during the trimming process.

My dummy cartridge COL (ogive) with the Hornady bullet measured 2.692", touching the lans of the barrel. I backed off my seater die .005" for a finished COL length of 2.687".

However, the finished cartridge COL's I measured varied somewhat, with a total variance of plus or minus .004". Is this an acceptable variance in COL's, or should I toss out the Forster lathe case trimmer and go back to the old Lee trimmer? Does anyone have any suggestions? I would appreciate the help.
Thanks!

 

[LUCKYDAWG13]

+or- .004 i think you good to go

 

[rcmodel]

Case length has nothing at all to do with loaded round OAL.
A short case or a long case will have the same OAL after loading it.

Because case length isn't part of the OAL measurement.
The bullet just seats deeper in a long case then it does in a short case.

.004" variation is quite acceptable.
The length variation comes from the difference in bullet ogive's in a box of bullets.
They aren't all exactly the same, and thats what the seating die pushes on to seat the bullet.

BTW: There is absolutely no need to crimp for a bolt-action 30-06, and that may be causing some of the OAL variation as well.

rc

 

[joneb]

What Hornady bullet are you using ?

 

[edfardos]

max variance of .010" is normal for my 30-06 loads (+\- .005"). Standard deviation is probably +\- .003". (half fall within that range).. Don't mess with the die if you get a short one... Only when you get a bunch of short ones.

edfardos

 

[Ridgerunner665]

Dang...I gotta say this...and its NOT a slam against Hornady bullets, its just the truth.

Ballistic Tips don't vary that much...maybe .002", usually closer to .001".

And rcmodel is right...crimping often does push the bullet deeper into the case...FCD or roll crimp...both will do it.

 

[moonzapa]

I'm loading Hornady 168 grain A-Max bullets. Good reputation for accuracy.

 

[USSR]

moonzapa,

Even Sierra MatchKing bullets will vary in the location of the bullet ogive by up to .010", so for that reason, I never load to a base-to-ogive length of less than .010" of the boltface-to-lands length. Having some of your bullets into the lands and some off is not conducive to accuracy. Just MHO.

Don

 

[moonzapa]

I am using a light-medium crimp on my ammo, and that probably is the culprit. I started crimping after an elk hunt in Colorado. After cycling ammo from the magazine to the chamber, and general handling of them, I noted that some of my cartridges were shorter/longer than others. Since going to the Redding dies, I've noticed more pressure to seat bullets, tighter necks, and I probably could do without crimping. Thanks for helping me out.

 

[viper7342]

Don't mean to hijack the thread but

I was wondering if these variations in length also occur with handgun rounds and if so, how much variation is normal with rounds like 9mm, 40S&W, 357 Sig, 45 ACP etc?

 

[rcmodel]

Yes.

If you want a real eye-opener sometime on how good your reloads are?

Measure a box of factory ammo in any caliber you choose.

rc

 

[Ridgerunner665]

Seater dies for pistols seat the bullet from the nose in most cases (hollow points) so the OAL should be more consistent with those...

Round nose bullets...I've never looked into it, but I expect they'll vary some depending on where the die catches them....I've always shot flat bullets in pistols so that about all I can say.

 

[joneb]

Is the seating stem seating the bullet from the polymer tip or the ogive of the bullet ?

 

[GLOOB]

Take the seater plug out and look at it. Most rifle seater plugs are designed to touch on the ogive, cuz most rifle bullets are too pointy to push in by the nose. I'm sure there are exceptions.

 

[USSR]

The problem with seating bullets to be a particular distance off the lands as measured by tools such as the Stoney Point/Hornady O.A.L Gauge and a comparator is, the seating stem of the bullet seating die contacts the bullet in a different part of the ogive (closer to the meplat) than the comparator does.

Don

 

[FROGO207]

As stated above where your die seats from can make a huge difference with OAL. +100 to seeing what the factory ammo quality control is allowed to get by with. I find the handgun ammo can vary a lot if the lube or lead gets into the seater cup so be aware to check OAL for variation as you are loading.
I also go to extra lengths to make sure my neck tension is good enough that crimping is unnecessary unless for a tube feed rifle. I do usually end up polishing the expander for great fit on most of my dies regardless of brand. That combined with a VLD expander to just kiss the case mouth works well for my reloading methods. YMMV