Seating Depth Frustration

[rmeyerwy]

I been there. I have done a couple of things and feel I am now getting close enough as a general rule. In my mind a couple of things I feel can affect the outcome..
1. brass ( I now trim the OD of the necks on all my brass )
2. I went to a mandrel, so I took the decapping and resizing guts out of my FL die, decapp in one process
then run the brass thru a mandrel
3. anneal the brass

I have also noticed if I run a brush thru the neck prior to seating, that makes it easier to seat the bullet although I dont do that with my current setup.

 

[Bill Norris]

I found the two most important issues with seating depth variations is make sure the tip of the bullet is not bottoming out inside the seater stem and use consistent force on the press handle. As the ram reaches the top of the stroke don't allow the handle to bounce and hold down (dwell) for a short time with each piece.

 

[jroberts1968]

So, I am setting up some loads for a 308. I am starting with recommended COL of 2.8 and seating .003 back for 4 different loads for accuracy resting. So, objective is
2.8
2.797
2.794
2.791

However, I will get one cartridge measured and the next will be anywhere from .002 to .003 off. I took this that there might be a little tip deformation. So, I broke out the comparator to double check and I am also getting some cartridges with up to .003 difference. With a difference of up to .003 and me trying to seat a .003 difference, makes me wonder if I just wasted a bunch of time.

Am I doing something wrong? Bullets are 168 and 175 Match King. Non-tipped.

Also keep in mind that trim length will matter. If I missed it somewhere, I apologize but, are you using fired brass you have trimmed or new brass?

 

[USAFRet]

Also keep in mind that trim length will matter. If I missed it somewhere, I apologize but, are you using fired brass you have trimmed or new brass?

Fired brass and I trim all of it to suggested trim length.

 

[USAFRet]

I found the two most important issues with seating depth variations is make sure the tip of the bullet is not bottoming out inside the seater stem and use consistent force on the press handle. As the ram reaches the top of the stroke don't allow the handle to bounce and hold down (dwell) for a short time with each piece.

Thanks for that tip. I try to stay consistent and hold down for a sec.

 

[quartermaster]

If you are not getting the same seating depths using the comparator, just a suggestion to take your seating die apart and clean it. If it’s new it has factory rust preventative in it and if it has been used, it could just be dirty.
may be a good starting point b-4 going any further

 

[gunsandgunsmithing]

If you are not getting the same seating depths using the comparator, just a suggestion to take your seating die apart and clean it. If it’s new it has factory rust preventative in it and if it has been used, it could just be dirty.
may be a good starting point b-4 going any further

Good points. I've also seen seater stems crack. Just a fine little hairline crack that's hard to spot. That'll definitely cause erratic seating depths.

 

[Dave Zander]

What helped me was mostly mentioned here.
1.) sort bullets base to ogive.
2.) use a Wilson micrometer bullet seater , they take a arbor press or I use a drill press to push the seating stem down to bottom out and seat the bullet.
3.) lube inside of case neck.

More than once I’ve had .003” difference in seating depth make a good bit of group size change.

 

[mbp708]

Also measure each loaded rounded several times to see if the caliper is giving consistent measurements. Not having the bullet firmly seated in the comparator or cartridge base sitting perfectly flat on the caliper can give false readings

 

[Lone Hunter]

If you have a micrometer seating die you can back the micromenter off and check each cbto. Example back off micrometer .010 and dial it to your chosen cbto. It’s slower with bullets that vary that much but at least you know you have it right.

 

[USAFRet]

Thanks all I don't have a micrometer die. Just standard RCBS. i did not think about breaking the die down for cleaning. I think measuring the bullets by ogive and sorting prior may be helpful. I will do that.

 

[Texas Solo]

That is my thought. I would think Sierra Matchkings would be a more premium bullet.

I found the opposite. SMK bullets were way inconsistent in there length and olive measurements. Go Berger or go home.

 

[Doghed]

I recently noticed the same problem. I think it was mentioned above but I'll restate based on what I measured.
I think the issue we're seeing is caused by the fact that our comparator is measuring a different spot on the ogive than what our seating stem references when seating the bullet (as stated in a previous post).

I'm using 175 SMK's. I measured bullets until I had 30 that matched bullet base to ogive (BBTO). After seating the selected SMK's (using a Wilson chamber type seater) I remeasured CBTO on all 30 cartridges. While most were the same, some ended up being +/- a thou or two.

I think it's the SMK's. The ogives are not consistent.

 

[USAFRet]

Thanks all. I couldn't really sort bullets as I got 2-24 piece sample packs. I will let my friend know. If we get inconsistent results at the range today, I will suggest researching another bullet.

 

[Doghed]

FWIW...at my current shooting skill level and with a factory chamber (lots of free bore) I couldn't see any negative results on the target.

 

[gldprimr]

So, I am setting up some loads for a 308. I am starting with recommended COL of 2.8 and seating .003 back for 4 different loads for accuracy resting. So, objective is
2.8
2.797
2.794
2.791

However, I will get one cartridge measured and the next will be anywhere from .002 to .003 off. I took this that there might be a little tip deformation. So, I broke out the comparator to double check and I am also getting some cartridges with up to .003 difference. With a difference of up to .003 and me trying to seat a .003 difference, makes me wonder if I just wasted a bunch of time.

Am I doing something wrong? Bullets are 168 and 175 Match King. Non-tipped.

I’m sure others will chime in but I’d start with the CBTO measurement of an average of three to five loaded rounds at your nominal length of 2.80”. After getting that CBTO average length, I’d then reduce in 0.015” (15 thousandths) increments to find a sweet spot. After that, then if needed fine tune with smaller increments. Going 3 thousandths at a time to start will burn a lot of components and time as well as being potentially frustrating. My thoughts FWIW though there are many here more knowledgeable than I.

 

[gldprimr]

So, I am setting up some loads for a 308. I am starting with recommended COL of 2.8 and seating .003 back for 4 different loads for accuracy resting. So, objective is
2.8
2.797
2.794
2.791

However, I will get one cartridge measured and the next will be anywhere from .002 to .003 off. I took this that there might be a little tip deformation. So, I broke out the comparator to double check and I am also getting some cartridges with up to .003 difference. With a difference of up to .003 and me trying to seat a .003 difference, makes me wonder if I just wasted a bunch of time.

Am I doing something wrong? Bullets are 168 and 175 Match King. Non-tipped.

I don’t think you are using VLD bullets however Berger Bullets has an excellent explanation of the methodology to employ looking for the optimum seating depth on their website. See link below:

VLD - Making it Shoot

VLD bullets are designed with a secant ogive. Berger VLD bullets are consistently and exceptionally capable of putting game down quickly

bergerbullets.com

 

[gunsandgunsmithing]

I don’t think you are using VLD bullets however Berger Bullets has an excellent explanation of the methodology to employ looking for the optimum seating depth on their website. See link below:

VLD - Making it Shoot

VLD bullets are designed with a secant ogive. Berger VLD bullets are consistently and exceptionally capable of putting game down quickly

bergerbullets.com

I wonder if that was Walt's method. Lol!

 

[dgeesaman]

FWIW...at my current shooting skill level and with a factory chamber (lots of free bore) I couldn't see any negative results on the target.

Well skill is a factor but equipment too. Whether or not you have wind flags, parallax-free high mag optics, perfectly tuned free-recoil rest and bag setup, barrel mirage heat shield, benchrest trigger, etc it all adds up.

A lot of advice given out here is from competition shooters doing their competition loading things. Context matters I’m afraid.

 

[Mark611]

Well guy's the Serria 175gn Match Kings, I have were purchased about 15yrs ago, I bought several thousand of them, I will agree the ojive measurements vary but I can still put together enough consistent groups of these bullets with the ojive to base measurements, to get them sorted between .5k to 1k in good quantity for consistent loads in large enough quantities to not worry about accuracy, my rifle will shoot a half inch 5 shot group at 200m with these bullets, I have no idea of how or quality or consistency of new production bullets are from Sierra? I have not purchased any 175gn SMK's in 15yrs, IMO if new production bullets are that inconsistent it's due to the demand for ammunition, JMO