Effect of Seating Depth

[AR-10 Shooter]

I'm working up a 175 gr load for my stock PSS. Started with 43 - 46 GR of Varget seated to 2.800. 44GR appeared to be "the" load.

I went back to the range with 43.3-44.1 in .3 GR increments to confirm the load but seated to 2.810. 43.3 was "the" load.

I shot the loads in round robin fashion and waited 2 minutes between shots. Will changing the seating depth make this much difference?

Mant thanks in advance for your help and advice,
CT

 

[308sako]

Re: Effect of Seating Depth

Deleted in protest!

 

[montyb]

Re: Effect of Seating Depth

seating depth makes a big difference in pressures. in the 7wsm, a .15" reduction in seating depth will require dropping the powder charge 1 grain to maintain the same approximate pressure. smaller case will affect it even more.

 

[EddieP]

Re: Effect of Seating Depth

In a 357 mag revolver with a 12" barrel, I sat the bullet 1mm deeper and gained about 100fps I think.

 

[Killswitch Engage]

Re: Effect of Seating Depth

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AR-10 Shooter</div><div class="ubbcode-body">I'm working up a 175 gr load for my stock PSS. Started with 43 - 46 GR of Varget seated to 2.800. 44GR appeared to be "the" load.

I went back to the range with 43.3-44.1 in .3 GR increments to confirm the load but seated to 2.810. 43.3 was "the" load.

I shot the loads in round robin fashion and waited 2 minutes between shots. Will changing the seating depth make this much difference?

Mant thanks in advance for your help and advice,
CT </div></div>

i can say that 43.3 varg is the load in my pss as well. i have been running 2.80 but now i have the badger m5 so i can stretch my OAL a bit. the distance to lands in the stock rem chamber is huge. i believe i am around .090 from the lands at 2.80

 

[oneswithfunes]

Re: Effect of Seating Depth

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dgunn</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AR-10 Shooter</div><div class="ubbcode-body">I'm working up a 175 gr load for my stock PSS. Started with 43 - 46 GR of Varget seated to 2.800. 44GR appeared to be "the" load.

I went back to the range with 43.3-44.1 in .3 GR increments to confirm the load but seated to 2.810. 43.3 was "the" load.

I shot the loads in round robin fashion and waited 2 minutes between shots. Will changing the seating depth make this much difference?

Mant thanks in advance for your help and advice,
CT </div></div>

i can say that 43.3 varg is the load in my pss as well. i have been running 2.80 but now i have the badger m5 so i can stretch my OAL a bit. the distance to lands in the stock rem chamber is huge. i believe i am around .090 from the lands at 2.80 </div></div>

That has been my exact experience as well. I seat at 2.870 and hand load each round.

 

[Downzero]

Re: Effect of Seating Depth

2.800" is very short. I remarked in another thread that "nobody" is shooting ammo that short in a factory chamber. My loads are about 2.895".

I suspect that you're giving up quite a bit by loading that short, but if you develop the load at that length that shoots well, you might be surprised at what you gain.

edit...

I recognize that 2.800" is the SAAMI max length for .308. That's all fine and dandy, but those of us with factory "porn star" chambers need to load longer or we're never going to hit anything.

 

[ReaperDriver]

Re: Effect of Seating Depth

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Downzero</div><div class="ubbcode-body">2.800" is very short. I remarked in another thread that "nobody" is shooting ammo that short in a factory chamber. My loads are about 2.895".

I suspect that you're giving up quite a bit by loading that short, but if you develop the load at that length that shoots well, you might be surprised at what you gain.

edit...

I recognize that 2.800" is the SAAMI max length for .308. That's all fine and dandy, but those of us with factory "porn star" chambers need to load longer or we're never going to hit anything. </div></div>

With loads at 2.895 - I assume you are stuck with single loading, correct? I have thought a lot about playing with the seating depth from the lands trick - but I made the decision early on that I will not shoot anything that isn't able to be shot out of the mag (i.e. mag length). I don't routinely shoot F-Class or similar - I want a practical round that can be used to hunt, shoot tactical matches, and other types of "practical" shooting. Granted, I may be giving up a couple fractions of inches of accuracy by not going long - but I've found a really good load that works at Mag length. Just my $.02.

 

[Downzero]

Re: Effect of Seating Depth

My magazine is about 2.840", so yes, those are single load only. If I had to load from a magazine, I'd probably change to a detachable magazine that would allow for longer seating depths.

Is your factory magazine so short that 2.800" is the absolute longest you can seat?

 

[Greg Langelius *]

Re: Effect of Seating Depth

Factory match loads, like BH and FGMM, Lapua and Norma, seem to get by using SAAMI max COAL dimensions. So it can be done.

Greg

 

[Downzero]

Re: Effect of Seating Depth

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">Factory match loads, like BH and FGMM, Lapua and Norma, seem to get by using SAAMI max COAL dimensions. So it can be done.

Greg </div></div>

The entire point of this thread and the other one on reloading is that quality handloaded ammo, fitted to the rifle, will shoot far better than some off the shelf factory ammo that just so happens to use a good bullet.

YMMV.

 

[Greg Langelius *]

Re: Effect of Seating Depth

Thanks, Tim, I appreciate the heads-up.

Greg

 

[Clark]

Re: Effect of Seating Depth

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

I recognize that 2.800" is the SAAMI max length for .308. That's all fine and dandy, but those of us with factory "porn star" chambers need to load longer or we're never going to hit anything. </div></div>

My AR15 lands are not available for comment, at any OAL with any bullet.
I can get better accuracy in a 22 rimfire take off barrel and 100 year old Mauser action, but using a 223 reamer with short throat. That is a $80 cost to build rifle that will out shoot any of my $1k AR15s with factory 5.56 chambers.