Seating depth variance +/- .010". Problem?


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Rmeju
May 10, 2009, 04:37 PM
The title pretty much says it. I've reloaded a lot of pistol, but not so much rifle, and very little 30-06, which I'm working on now.

I'm trying to seat to the max OAL listed in Hornady manual 3.185", but getting variances high & low up to +/- .010".

1. Is that a problem?

2. What are the usual causes of something like that?

RCBS dies. 147gr FMJBT bullets.

Thanks!

Rmeju

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lnlreloader
May 10, 2009, 04:39 PM
You are measuring OAL of the cartridge, not seating depth. Your seating depth is probably much more consistent, and variations in the bullet ogive are giving you a more variable overall length. I do not feel you have a problem.

ChefJeff1
May 10, 2009, 04:41 PM
I'm pretty new to this but measuring my factory .270 140 gr nosler accubonds there is variances too. I measured some sierra 90 gr varminter bullets and they are off by about .002 to .005.

lnlreloader
May 10, 2009, 04:44 PM
The more consistent the bullets are, the less variation you will have.

Walkalong
May 10, 2009, 04:52 PM
The better your seater stem fits the contour of the bullets, the better it will be as well.

You are measuring OAL of the cartridge, not seating depth. Your seating depth is probably much more consistent, and variations in the bullet ogive are giving you a more variable overall length. I do not feel you have a problem.
Yep. Probably not. Get a bullet comparator (http://www.sinclairintl.com/prod_detail_list/Bullet-Seating-Depth-Tools-OAL) and check things. Consistent jump to the lands is more important.

rcmodel
May 10, 2009, 04:56 PM
147gr FMJBT bullets.That right there is part of your problem.

FMJ-BT military type bullets are especially prone to having different ogives in a box of them because they are made in mass quanities, in several different swaging dies, and then dumped in the same bulk containers for polishing & packing.

Minor variations in a bunch of different swaging dies result in minor variations in the bullets.

And in general, 147 FMJ are made to meet military acceptance & accuracy standards, which are much lower then for commercial hunting or target bullets.

Try better bullets, all made in the same die, and your OAL variation will be less.

rc

Rmeju
May 10, 2009, 04:57 PM
Er...yes! I meant to say that I'm measuring OAL, not depth. Normally I don't care up to +/- .005" (what I occasionally get on my pistol rounds). I just wanted to make sure my Garand wouldn't be throwing away my bullets :D

If this OAL variance isn't a problem. I won't worry about it.

Rmeju

Steve C
May 10, 2009, 05:02 PM
You want to make sure your bullet is off the rifling when chambered. To make sure your bullets aren't into the refiling when chambered, smoke or black the bullet of the longest one and see if there are any markes after chambering. If none that +/- .010 won't make any difference.

Rmeju
May 10, 2009, 05:46 PM
@ RC: I'm going to shoot the bullets I have, not the bullets I want to have. The bullets I have on order are better, and that may certainly alleviate the problem, however, I'm not going to throw these ones away. I could've done that on my own. These are just for iron sight plinking, I'm sure it'll be fine.

@Steve: Thanks, I think I'll give that a try!

rcmodel
May 10, 2009, 06:02 PM
however, I'm not going to throw these ones away. I could've done that on my own.Nowhere did I suggest you throw them away.

I was trying to help you by explaining the "why", not disparaging you for shooting FMJ-BT bullets.

Sorry if I ruffled your feathers.
It won't happen again.

rc

Walkalong
May 10, 2009, 06:26 PM
I bet everyone on this board that reloads shoots bulk FMJ-BT bullets in something just for cheap plinking/blasting.

Heck, there cheap, right? :)

Daniel1120
May 10, 2009, 10:26 PM
Mmmmmmm cheap boolits...

Might not all be perfect, but shootin cheap is what its all about, in my case.

Rmeju
May 11, 2009, 07:37 AM
@RC If this isn't what you meant, I think I should take you at your word. Apologies

Rmeju

Jim Watson
May 11, 2009, 08:43 AM
I bet everyone on this board that reloads shoots bulk FMJ-BT bullets in something just for cheap plinking/blasting.

You lose. The only FMJ rifle bullets I have ever loaded were surplus military match to see what a .30-30 bolt action would do with spitzers. I think I have pulled more 55 gr .223s to make Mexican Match than I have shot.

Walkalong
May 11, 2009, 08:46 AM
Oh well..... 99%? :D

jbkebert
May 11, 2009, 09:00 AM
http://www.cabelas.com/cabelas/en/content/Pod/04/45/17/p044517sq01.jpg

I use this setup it measures the bullet across the ogive not the bullet tip. You will get more consistant measurements. Like was posted above the bullet tip will vary a little bit depending on bullet make and manufacture. The ogive will not change from one bullet to the next. As long as you are comparing the same type of bullet over and over.

lnlreloader
May 11, 2009, 09:27 AM
If you are using a bullet comparator as shown above, where do you find data on what the length from the case head to the ogive should be? Reloading books only give OAL.

jbkebert
May 11, 2009, 09:33 AM
The OAL that the manuals give you is maximum SAMI safe recomendations. You could load a round and take the measuement off of one cartridge to verify OAL. Then remeasure with the Bullet comparitor attached. Once you have that the rest should stay consistant. That is one reason why if someone asked for a load recommendation I never give a OAL. All of mine are based off of the bullet comparator. I do see the problem that you are asking about I base my OAL off of the lands not SAMI specs. This only works if you have a OAL gauge and modified cases and all of that extra stuff.

lnlreloader
May 11, 2009, 09:48 AM
Ok that makes sense.

We all know what OAL is, but what is the name of the distance from the Ogive to the Case Head as measured by a bullet comparator?

jbkebert
May 11, 2009, 10:03 AM
http://www.geocities.com/rocketguy_101/ogive/OgiveNoseCones_files/image002.gif

http://www.geocities.com/rocketguy_101/ogive/OgiveNoseCones_files/ogive_2.gif




"There are two basic types of ogival nose shapes: the tangent ogive and the secant ogive. A tangent ogive has an arc which meets the body contour smoothly, thereby creating no break in line where the ogive joins the cylindrical body. In other words, the center of rotation of the arc is in the plane of the base of the nose. If the center of rotation of the arc is aft of the plane of the base of the nose, you’ve got a secant ogive.



This has been the only definition of a secant ogive I could find. The following diagrams illustrate: Basically the Ogive is the radius where the bullet meets the cone of the bullet. Hornady uses a Secan ogive while Berger and other use a Tangent ogive. The bullet comparitor will measurer either. The length of the Ogive will change from bullet maker to bullet maker. It will also change in weight of the bullet. Like a 168 gr A-max will be longer in length than say a 150 grain Interbond. As long as you measure the ogive on the same type bullet it will not change where as the bullet tip can change a little bit.

Walkalong
May 11, 2009, 11:53 AM
what is the name of the distance from the Ogive to the Case Head as measured by a bullet comparator?I don't think there is a name for it. Just log it and go from there.

30Cal
May 11, 2009, 12:22 PM
1. It's your bullets
2. It has no effect on target

USSR
May 11, 2009, 12:37 PM
The OAL that the manuals give you is maximum SAMI safe recomendations.

Nope. It's simply the OAL that they chose to use. There is no SAAMI cartridge OAL spec, since OAL will vary according to what bullet is used.

Don

jbkebert
May 11, 2009, 02:36 PM
USSR
thanks for the info. I did not know that. I always figured since most manuals are almost carbon copies on OAL that it was a industry lawyer standard.

Jim Watson
May 11, 2009, 02:47 PM
Strange, the SAAMI drawings in my old NRA Handloading show minimum and maximum cartridge OAL in all calibers. .30-06 is 2.970 minimum to 3.340" maximum, which covers a lot of bullet types but makes sure everything will go in a standard magazine.

The 3.185" in the OP probably IS Hornady's maximum OAL for their bullet(s), though.

Afy
May 11, 2009, 04:31 PM
30Cal... while I do not have your expertise... I always thought bullets do have an effect on the target.
As would the jump and BC...

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