Seating depth advice...

[planalpha]

Experts-
I've been seating my 308 bullets (175 SMK) to 2.80 because I can't go any longer with my blind magazine. I've been measuring the cartridge from the bullet tip to the end of the case and noticed that there is quite a bit of variance from bullet to bullet. Should I just trust my seating die and stop checking the COAL or should I fiddle with each round until I get it right at 2.80?

Thanks!

 

[Mordamer]

Re: Seating depth advice...

First you need to make sure that your primers aren't sticking out the bottom of your loaded rounds ever so slightly. They can be sticking out by 3 to 5 thousandths of an inch and you might never notice. This throws off your O.A.L. measurement by that much. The primer seating depth is not very precise from case to case and so that could explain the variance in your measurements if they are sticking out a few thousandths.

How much variance are you actually getting in your measurements?

 

[Jerry m]

Re: Seating depth advice...

What kind of groups are you currently shooting?

 

[gcoulsey]

Re: Seating depth advice...

After checking your primers aren't proud, as mentioned, notice that there is a variance in the tips of the bullets (the meplat),
They can be altering your measurement a few though easily,
How much clearance do you have in your mag, and what seater are you using?

 

[MinorDamage]

Re: Seating depth advice...

The issue is most likely none of the above. The seater seats the bullet on the ogive. So, you are most likely getting consistent base to ogive seating distance. If you have a bullet comparator you can check it that way. The ogive to tip distance on premium bullets even varies significantly at times. If your base to ogive is consistent, don't worry about it.

Josh

 

[i_Adam_i18]

Re: Seating depth advice...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MinorDamage</div><div class="ubbcode-body">The issue is most likely none of the above. The seater seats the bullet on the ogive. So, you are most likely getting consistent base to ogive seating distance. If you have a bullet comparator you can check it that way. The ogive to tip distance on premium bullets even varies significantly at times. If your base to ogive is consistent, don't worry about it.

Josh </div></div>

+1. I had the same issue when I was loading up some cheap .223 bullets. I tried 2 different seating dies and came up with the same thing. The bullets were cannelured and I was using that as a reference and could tell there were obvious variations. But it comes from the seating die going off the ogive, not the tip of the bullet.

You'll never be able to adjust the die to seat them all to the same OAL (which I was suprised to hear with good bullets). And apparently all that matters is base to ogive length. As long as they all fit in the mag still.

 

[gcoulsey]

Re: Seating depth advice...

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> The ogive to tip distance on premium bullets even varies significantly at times.</div></div>

This is what I was trying to say,
The OP is measuring off the tip, not the ogive, so there is room for error in measurement, with the variance in bullets.
In answer to the original question, don't try and alter each round as they will naturally vary, as long as you have clearance in your mag, and they shoot ok, trust your seater.
However, as suggested, a bullet comparitor is the way to go to check your rounds properly,
Good luck!

 

[999yards]

Re: Seating depth advice...

Primer seating will make a difference in OAL measurement if it is not below flush and the caliper arm is placed across the primer. Get a primer pocket uniformer from sinclair and use a bullet comparator. The uniformer will flaten out the primer seat and allow for a more consistent seating depth which will be below flush.

 

[planalpha]

Re: Seating depth advice...

Great info!
I have been checking that the primer isn't extended thus throwing off my results. So it sounds like I need to "set and forget" my seating die and find a bullet comparator to verify. Any suggestions on what/where to get?

Thanks again, all!

 

[bignada]

Re: Seating depth advice...

Load your bullets as far out as you can and still have magazine function.

If you want to load bullets into or just off the lands, sounds like you'll have to single-load.

Not a big deal, just life and learning to cope with all the variables of shooting.

 

[jtac]

Re: Seating depth advice...

I've had the same problems. While setting up my 223 dies, I seated 60gr Vmax, I would seat one at 2.250 and then the next would be 2.240 or 2.260, I fig it was consistent on the ogive and got it right on for one and it should be consistent. I usually measure from ogive but forgot the ogive measurer when I went to my reloading room. To the point, I noticed when you tighten your lock nut if your dies turns some or the tension of the die tightening up can seat it deeper if you don't unscrew it and back in after you tighten the lock nut.

 

[sjm229]

Re: Seating depth advice...

These work well.

Sinclair Bullet comparator body and insert

You can also use the Bump Gauge insert with the same body to set up FL seating dies for minimal shoulder bump.

 

[vman]

Re: Seating depth advice...

I have the Hornady equivalent. They are good products, and worth the money if you do lots of handloading