308. 168gr sierra seating depth?

[cobaltbomb]

i have been trying out reloading today for the first time with the help of an experienced friend. we have been using 168grain hpbt sierra bullets, 41 to 43 grain n140 powder in 0,5grain increments, and RWS brass, to develope a load for my howa 1500 varminter. i got sub MOA 5 shot groups on 100 meters with the 42,5 and 43 grain loads, allthough there was wind and quite heavy snowfall.

we seated the bullets half a millimeter away from the rifling, what do you guys recommend should i use more than the half milimeter? maybe 1 or 2 milimeter?

 

[jdgray]

Re: 308. 168gr sierra seating depth?

I run my 168s, right at 2.800, the same as GMM ammo. This is .013" off the lands in my Savage 10FP. I'm no MM conversion wizard, but thats not many.

 

[TapoutSniper]

Re: 308. 168gr sierra seating depth?

Like he said... stick close to 2.800 coal and you should be real close.

 

[biglakesrule]

Re: 308. 168gr sierra seating depth?

2 millimeters is like 78 mils. There's not much point keeping track of the distance off the rifling when it's that far out, I don't think. Switch your caliper to read out in mils, unless you prefer converting "10 mils" to "0.254 mm"

A lot of precision shooting sources say something like start at 15 mils off the lands and move it up closer while watching for pressure signs. Some benchrest folks have the bullet touching the lands, or 1-5 mils out. Of course, they have the gun chambered to match that scenario, so the bullet is still well into the case and not "just hanging there", and they choose a powder charge to work well there.

If having a bullet that close to the lands means you don't have it seated very far into the case (as might be with a "factory-like" chamber), you might be doing more harm than help. Also, if you end up with it seated too long, it might not fit in a magazine anymore.

My suggestion, like others, would be to stay at 2.800" or 2.810" if you get acceptable accuracy there.

 

[mdmp5]

Re: 308. 168gr sierra seating depth?

All rifles' throats are different. 2.800" COAL is roughly 0.07" from the lands in my rifle, which is a pretty big jump. You need to measure the distance to YOUR lands with a dummy round. That is the only way to know. Keep in mind that factory ammo is designed to run in the majority of rifles, so they will be seating the bullets at a length that will be short enough so they are not jammed into the lands.

 

[biglakesrule]

Re: 308. 168gr sierra seating depth?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: palmik</div><div class="ubbcode-body">All rifles' throats are different. 2.800" COAL is roughly 0.07" from the lands in my rifle, which is a pretty big jump. You need to measure the distance to YOUR lands with a dummy round. That is the only way to know. Keep in mind that factory ammo is designed to run in the majority of rifles, so they will be seating the bullets at a length that will be short enough so they are not jammed into the lands.</div></div>

Agreed. In the end, I am advocating staying in SAAMI specs and not worrying about the jump distance if you can achieve "good enough."

 

[LoneWolfUSMC]

Re: 308. 168gr sierra seating depth?

Magazine length and gass on!

SMK's don't seem to care about he jump in my "deep throat" remmy.

 

[vman]

Re: 308. 168gr sierra seating depth?

LOL "Deep Throat" remmy

I have the same issue with my 700P. MEh !

As soon as the AICS turns up im just going to load all my rounds to 2.800 COAL

 

[dagwood]

Re: 308. 168gr sierra seating depth?

the conversion from .013" to mm is .3320 mm and if you are going from 0.07" from lands it is 1.77800 mm

 

[skinnypitt]

Re: 308. 168gr sierra seating depth?

my 700PSS seems to like the jump as well. I tried pushing it out towards the lands but my groups opened up like crazy. i went from .5 MOA to 1.5.....so i backed off and went back to jumping it. By the way i am loading 44 grains varget behind the 168 SMK and it seems to shoot just a little higher than the GMM

 

[Xshot]

Re: 308. 168gr sierra seating depth?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jdgray</div><div class="ubbcode-body">I run my 168s, right at 2.800, the same as GMM ammo. This is .013" off the lands in my Savage 10FP. I'm no MM conversion wizard, but thats not many.</div></div>

+1 on your recommendation for the 10FP. My 10FCP chamber is the same for Sierra 168's - OAL at 2.800 puts me .013 off the lands. In addition, I can safely run my brass to 2.025 - that's .010 over max trim length. Makes for a lot less brass trimming.