.308 varying OAL

[Proarc]

Just bought a Hornady bullet comparator and insert set. Trying to get my OAL determined so I can accurately measure cartage length.

The problem is I could not keep coming up with the same number using the lock and load gauge. So I pulled 10 bullets from the box (175SMK) and measured them, came up with 2.203, 2.207, 2.211, 2.206, 2.205, 2.209, 2.209, 2.208, 2.206, 2.209.

How can the length change that much?
How can you accurately know if you are jumping the bullet or jammed in the lands with a length changing that much?

My chamber OAL measures out to 2.216, but that can change by using a different bullet.
Factory 175 FGMM measures out at 2.21, so factory ammo is jammed into the lands on my gun.

I really did not expect this much variance in OAL. But I have to nail this down before I can work up a solid load.

I did call Hornady tech line, nice folks but they did not have an answer.


Thanks in advance for any ideas!!

 

[MitchAlsup]

Re: .308 varying OAL

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Proarc</div><div class="ubbcode-body">Just bought a Hornady bullet comparator and insert set. Trying to get my OAL determined so I can accurately measure cartage length.

The problem is I could not keep coming up with the same number using the lock and load gauge. So I pulled 10 bullets from the box (175SMK) and measured them, came up with 2.203, 2.207, 2.211, 2.206, 2.205, 2.209, 2.209, 2.208, 2.206, 2.209.

How can the length change that much?</div></div>

Because each bullet is formed in a different die(s).

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">How can you accurately know if you are jumping the bullet or jammed in the lands with a length changing that much?</div></div>

This is one reason we are either 0.010 off the lands or farther or 0.005 into the lands or farther. In addition a change in temperature from the reloading station to the final firing position can have a cartrige change dimensions by as much as 0.005. Thus, we avoid settling on a cartrige dimension where we can't predict jump-or-jam for one that we can tell.

 

[Proarc]

Re: .308 varying OAL



Whats better to start out with, going with a bullet jump or jammed? Just as a general starting point.
Just touching will not work with this much variance in ogive. Even if you were set back.010 these measurements could move toward touching and increase pressures.

 

[IanWRX]

Re: .308 varying OAL

Jammed

Read this!

 

[Proarc]

Re: .308 varying OAL

IanWRX

I have read those stickeys several times. That guy makes it sound easy. And I believe it is easy. My goal is to work up a 1000yd load so the details are important.

I have a problem with a precision reload when the OAL as measured at the ogive varies as much as 0008. If i seat .010 jammed I can come up with a bullet that will load out to .002 jammed and that can not be consistent. As great a bullet as the Sierra 175s are I am surprised at this spread in dimensions.

My reloads are shooting well as far as group size, but I would like to be able to load a cartage .010 jammed and all my rounds be that length.

I have even though my calipers were afu, so I brought mine from work to recheck all my measurements.

Again thanks for all the help and ideas. This site has so much info!

 

[BobinNC]

Re: .308 varying OAL

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Proarc</div><div class="ubbcode-body">IanWRX

I have read those stickeys several times. That guy makes it sound easy. And I believe it is easy. My goal is to work up a 1000yd load so the details are important.

I have a problem with a precision reload when the OAL as measured at the ogive varies as much as 0008. If i seat .010 jammed I can come up with a bullet that will load out to .002 jammed and that can not be consistent. As great a bullet as the Sierra 175s are I am surprised at this spread in dimensions.

My reloads are shooting well as far as group size, but I would like to be able to load a cartage .010 jammed and all my rounds be that length.

I have even though my calipers were afu, so I brought mine from work to recheck all my measurements.

Again thanks for all the help and ideas. This site has so much info! </div></div>

Proarc,

Quit friggin around, just load em and go shoot. Sierra bullets, despite being dimensionally challenged with the length varying all over the place still do shoot well.

Unless you are trying to set benchrest records, you are wasting your time and effort better spent just shooting.

If your really worried about it, shoot a better (dimensionally) bullet like a Berger.

 

[Proarc]

Re: .308 varying OAL

BobinNC

Thanks for the different perspective, Probably trying to hard to make everything consistent. Will have to try the Berger bullets. Just bought 1000 175smk that I need to shoot up first.

 

[memo43]

Re: .308 varying OAL

just load em and go shoot. Sierra bullets, despite being dimensionally challenged with the length varying all over the place still do shoot well.



That is the advice I took without even reading the post. I shot my first f-class (service category) match this past weekend. I used a 5R grabbed a "green box" did the moly trick. went with a common 308 load (found in the load section)

Guess what shot a 197 4x at 600 yards. 20 shots for record 51/2 vertical spread.

load them and shoot them. come back an post the result