Seating depth variance

[Joefrazell]

What kind of seating depth variance do you typically see. I'm loading some 300 win mag and am checking and most of my loaded rounds are 2.900 cbto but some are 2.898-2.902 so I'm getting a .004" of a variance. I'm using a Lee single stage press and an rcbs seating die. It's adg brass and 225 eldm's. To me this seems like alot of variance but want to get others opinions. When seating I try to always use the same downward pressure and I also, will rotate the case 1/4 turn and seat again. What's a tolerable variance?

 

[Mikecr]

A tolerable variance is that determined through seating testing.
The tightest seating window I've come across so far is 8thou. So I doubt a 4thou variance would be an issue at all.

It's harder to drop CBTO variance lower than yours without sneaking into each one. To make this easier takes ogive radius comparisons & matching. People do this with a Bob Green Comparitor (BGC).

I vote: you don't have a problem

 

[338 dude]

What kind of seating depth variance do you typically see. I'm loading some 300 win mag and am checking and most of my loaded rounds are 2.900 cbto but some are 2.898-2.902 so I'm getting a .004" of a variance. I'm using a Lee single stage press and an rcbs seating die. It's adg brass and 225 eldm's. To me this seems like alot of variance but want to get others opinions. When seating I try to always use the same downward pressure and I also, will rotate the case 1/4 turn and seat again. What's a tolerable variance?

I usually get one thousandth shorter or longer than my target length so basically a variance of up to .002 I had the same problem until I switched from RCBS gold medal match dies with micrometer Seaters to Redding dies with micrometer Seaters it was a big improvement

 

[bill123]

What's your case prep method?

 

[YZ-80]

I'm usually in the +/- .002" around my target seating depth. I don't worry about it. I think it may be more due to inconsistencies with the actual ogive profile than anything else.

 

[aushunter1]

I find if I have had inconsistant neck tension which is usually through cases having a different number passes through the sizing die before annealing.
This is even with a Redding comp seater.

Do you find when seating that the longer seated projectiles have more resistance??
You can usually feel this through the press handle.

Imo annealing will help reduce this.

 

[Joefrazell]

Brass prep is as follows

Deprime
Tumble in stainless media for 45 min
Dry
Anneal
Full length body size bump .002 rcbs
Neck size .002 neck tension Lee collet die
Trim
Chamfer, debur,
Cean primer pocket
Tumble in stainless media for 45 min
Dry

 

[BoomFlop]

I would recommend using Imperial Dry Neck lube. That should reduce your variance.

I believe you necks are too clean and I would guess your seating force is inconsistent.

Steve

 

[bill123]

Brass prep is as follows

Deprime
Tumble in stainless media for 45 min
Dry
Anneal
Full length body size bump .002 rcbs
Neck size .002 neck tension Lee collet die
Trim
Chamfer, debur,
Cean primer pocket
Tumble in stainless media for 45 min
Dry

I think I see the problem and agree w/ BoomFlop.
Wet cleaning methods, ultrasonic and especially stainless steel tumbling make the inside of the necks rough to seat a bullet in. Annealing does as well.
After ultrasonic cleaning and annealing my 6mm necks, I chuck a 30cal nylon brush in a drill and run the brush through the necks. It brings my CBTO variance down to about .001"
After a while, the brush gets worn down, the CBTO variance goes up, I use a fresh brush and the variance goes back down.

 

[nksmfamjp]

I just loaded some brass that was:
new Win brass
fl sized in Forest FL die
trimmed
cham/deburr
expanded
neck turned to 0.013" thickness....cleaned up all but the worst cases
fl sized in bushing die
neck lubed
seated on mec press with Forester micrometer die


depth variation was 0.004", but I did have one round that was 0.002" longer than the longest making total variation 0.006".

 

[aushunter1]

I would recommend using Imperial Dry Neck lube. That should reduce your variance.

I believe you necks are too clean and I would guess your seating force is inconsistent.

Steve

Yes I've had this happen once before as well, only with one cartridge (300wsm) for some reason.
It was when I 1st started loading for the round & I again could feel it in a lot of resistance through press handle.
Was essentially very jerky.
So I ended up dipping the projectile bases into my dry lube container & it helped the seating a great deal.

 

[Bobcape]

I find if I have had inconsistant neck tension which is usually through cases having a different number passes through the sizing die before annealing.
This is even with a Redding comp seater.

Do you find when seating that the longer seated projectiles have more resistance??
You can usually feel this through the press handle.

Imo annealing will help reduce this.

I pay a lot of attention to neck tension and also dry lubing necks with graphite. It has paid big dividends in reducing SD/ES and seating depth variations. Sean explains it well in this video.

Bob

 

[Bobcape]

I use this for the neck lube -

https://www.amazon.com/gp/product/B00PFY0M90/?tag=lrhmag19-20
Bob

 

[RWE]

What??? No set it and forget it?!?!

...dangit.... now I have something else to obsess over....

On the other hand, thanks Bob for an additional prod to get the Imperial dry neck lube! Been meaning to get some.