Factory Base to OGive .308 150gr SST

[Kyle_hill98]

Hi there,

Does anyone have the factory seating depth for 150gr SST .308?

After the base to OGive measurement, any help appreciated!

Cheers,
Kyle

 

[JonC]

Hi Kyle, the only snag with asking for this measurement is that it's comparative - someone else's comparator won't necessarily match the setting that yours gives. Sure it might be 'close', but there's a potential for it to be significantly different. Might be just as well to get the factory average OAL as the tips are reasonably consistent dimensions? I don't have the Hornady App to check, but the Vihtavuori App Load data table says the OAL for the 150gr SST is 2.732".

 

[JonC]

I also just saw this thread: 150 grain hornady sat superformance
Seems someone else was looking for the same info. 69.68mm = 2.743"

 

[Kyle_hill98]

Hi Kyle, the only snag with asking for this measurement is that it's comparative - someone else's comparator won't necessarily match the setting that yours gives. Sure it might be 'close', but there's a potential for it to be significantly different. Might be just as well to get the factory average OAL as the tips are reasonably consistent dimensions? I don't have the Hornady App to check, but the Vihtavuori App Load data table says the OAL for the 150gr SST is 2.732".

I also just saw this thread: 150 grain hornady sat superformance
Seems someone else was looking for the same info. 69.68mm = 2.743"

Legend, thank you very much! Still learning when it comes to reloading

 

[Miki]

The Ogive is essentially the bit that hits the lands first. That distance is often called the 'jump'.
Some people load close to the lands, 10 thou or so and others 30 to 40 thou as they have determined that the resonance of the barrel is pretty much in line with the point of aim as the bullet exits.

Chasing the lands is a whole other ball game and falls within the camp of the Bench Rest and long distance shooter.
That 20 thou of difference is of course directly relative to the seating depth which in turn effects the case volume and consequently the max pressure.

I always advise that you check where the lands are and seat the bullet so that the jump is 35 to 40 thou.
Get your kit set up so that this is consistent, ie practice it several times until you are as close as you can get and then work up a load that suits this case volume/seating depth.
Once you have this load and you are happy with the way the bolt closes and the rounds leave the magazine/breech and the accuracy is where you want it to be ... Nirvana is reached

After a hundred firings its worth checking the jump again and it's always a good idea to check your consistancy with regards to seating depth with every batch you load.

 

[Kyle_hill98]

The Ogive is essentially the bit that hits the lands first. That distance is often called the 'jump'.
Some people load close to the lands, 10 thou or so and others 30 to 40 thou as they have determined that the resonance of the barrel is pretty much in line with the point of aim as the bullet exits.

Chasing the lands is a whole other ball game and falls within the camp of the Bench Rest and long distance shooter.
That 20 thou of difference is of course directly relative to the seating depth which in turn effects the case volume and consequently the max pressure.

I always advise that you check where the lands are and seat the bullet so that the jump is 35 to 40 thou.
Get your kit set up so that this is consistent, ie practice it several times until you are as close as you can get and then work up a load that suits this case volume/seating depth.
Once you have this load and you are happy with the way the bolt closes and the rounds leave the magazine/breech and the accuracy is where you want it to be ... Nirvana is reached

I always wonder where to start, should it be seating depth or powder first?
I was going to see what the ES/SD was like first and get a load then play around with seating depth after, is this wrong?

 

[Cyres]

Surely you want the factory COL. That data will be included in factory reloading data.
If you load a round to that COL you can then measure the OL. Then you can measure the OL of your chamber and determine the jump of the factory round.

Determining the optimal COl for your chamber will take a while. Others on here are better placed to advise scai don't reload for .308.
D

 

[Miki]

I always wonder where to start, should it be seating depth or powder first?
I was going to see what the ES/SD was like first and get a load then play around with seating depth after, is this wrong?

I'd say seating depth first as this effects the internal capacity which effects peak pressure.
To maintain a peak pressure you would use less powder in a smaller space.

If you worked up a load and were near max and then seated your bullet deeper you may possibly exceed.
GRT (an internal ballistics program) shows that if I seat a .224 bullet 1mm (40 thou) deeper (from 4 to 5mm) then I get close to max pressure (and get a warning) going from 48448 to 49734psi with 24.2gr of N130

 

[Kyle_hill98]

I'd say seating depth first as this effects the internal capacity which effects peak pressure.
To maintain a peak pressure you would use less powder in a smaller space.

If you worked up a load and were near max and then seated your bullet deeper you may possibly exceed.
GRT (an internal ballistics program) shows that if I seat a .224 bullet 1mm (40 thou) deeper (from 4 to 5mm) then I get close to max pressure (and get a warning) going from 48448 to 49734psi with 24.2gr of N130

I use GRT too, ill always use it to refference and when i play around with seating depths i'll do it gradually looking for pressure signs like i do with the powder.

Quick question, when using GRT and filling in the seating depths, do you arrive at your seating depths by:

OAL - Case length - Head length = Seating depth?

 

[safer]

I also just saw this thread: 150 grain hornady sat superformance
Seems someone else was looking for the same info. 69.68mm = 2.743"

69.68mm will not be ogive on any 308 round. That is most likely COL.

 

[Kyle_hill98]

69.68mm will not be ogive on any 308 round. That is most likely COL.

It is COL, see how he has measured it in the photo, the data will still help me as a starting point

 

[safer]

The only thing COL is useful for is to check if the round will fit in you mag and nothing else. It is ogive that hits the lands. I can give you ogive for Lapua match 308 that I had some a while back and that was 56.6mm.

 

[safer]

It is COL, see how he has measured it in the photo, the data will still help me as a starting point

As someone said above you could be way off. For example: measuring to my chamber the difference between Scenar 167gr and Siera SMK 168gr is almost 3mm. And that is huge jump if I was loading to COL.

 

[JonC]

69.68mm will not be ogive on any 308 round. That is most likely COL.

Yep, if you look at the photo in the thread, the measurement I've quoted is the picture of the measurement of the COL.

 

[Miki]

I use GRT too, ill always use it to refference and when i play around with seating depths i'll do it gradually looking for pressure signs like i do with the powder.

Quick question, when using GRT and filling in the seating depths, do you arrive at your seating depths by:

OAL - Case length - Head length = Seating depth?

Head length ???
You were doing so well ....

Using a dial gauge I measure the length of the case and the length of the bullet.
Using a Hornady OAL gauge I find the lands and using the same bullet/case/dial gauge measure the OAL - head to nose. If the bullet has a plastic tip, I will pull that and measure to the meplat.
Then I mark the bullet with a sharp, pull the bullet and measure from the base to the mark.
That + the jump = the seating depth.

The key is to then seat consistently, which within +/- 2 thou over 20 rounds keeps me happy, but would probably send long distance/competition shooters into a rage