and more mysterious drama, seating depth changing

[rockwind1]

redding micrometer seating die with the spring loaded sleeve, t7 press, 6.5 cm, berger hybrids, standard shellholder

set up so there is a slight cam over after shell holder pushes sleeve all the way in.

the primers are below pocket level

and my headspace guage is a mitutoyo with the typical hornady set up and having a recent ocurance with headpspace, i checked these and they are all with .001 of each other.

happily seating some bullets, checking every 2 or three with #26 bullet comparetor in dial calipers, the are running within .001 plus or minus,,, all off a sudden, .oo7 difference, longer, go back, some others are like that.

reset micrometer, get a few good ones, then they start to be to short. not the worlds best digital caliper, but can it be that far off.

what is the best way to measure seating depth with calipers?

what the,,,,**

 

[chromatica]

Try this hex comparator from Sinclair:

https://www.sinclairintl.com/reload...r-hex-style-bullet-comparators-prod83792.aspx

 

[Ned Ludd]

Why do you think the calipers are off, rather than thinking the seating depth of successive loaded rounds actually changed? It is certainly possible your calipers could be off, especially if they weren't a from a reputable manufacturer to begin with. However, it's more likely IMO that the loaded rounds measurements actually changed, especially if you didn't length sort bullets prior to seating by some method such as BTO, OAL, or using Bob Green's comparator tool, which sorts bullets based on the distance between the two points where the seating die stem and the caliper insert tool contact the bullet ogive.

To test the calipers themselves, measure the CBTO of a single loaded round 10, or even 20 times. You should get the exact same value every time if your calipers are working properly. Assuming you do and your calipers are working properly, then the chances are the it was your loaded rounds that actually varied.

 

[Uthink Uknow]

Mysteries of the seat. Some year ago we preloaded for a match a couple days before the match. These were 6PPC rounds for a 100 yard match. At the bench for the first match the closure on the bolt was heavier than I would like. I shot the first match and didn’t kill myself but I also checked the OAL of the rest of the rounds, or some of them. They were all about .004 longer than I had seated or thought I had seated them. So, I re-seated the remaining rounds as I went to the bench to shoot each match. Back home that week I seated a number of dummy rounds. The next day they has lengthen about .004 or .005 and I came to the thrilling conclusion there must be some spring back or internal resistance to the seating process. These dummies had no primer so it wasn’t a build up of internal air.

 

[cw308]

I guess you have to think of how could that happen , let's start with sizing the case . Bolt face to datum or shoulder , are they all the same . For bolt action .001 - .002 . Now your seating base to ogive . Could be off .001 but if the sized case measurements are off , maybe the reason . Check your case measurements

 

[mmcu]

Also, make sure that your primers are seated below flush.

 

[rockwind1]

Also, make sure that your primers are seated below flush.

i should have added that, they defintely are.

 

[foxguy]

Possibly the seating die needs a good cleaning??

 

[mikecr]

If you're neck sizing length exceeds seated bullet bearing then you're leaving a binding condition at the base-bearing junction. This functions to dramatically increase bullet grip, nowhere near consistently, and should never be done.
Could be squeezing some bullets forward.

 

[jlow]

It can and has happened. A real EASY way for that to happen is a piece of foreign matter getting under your case on your shell holder.

That's ALL it takes....

 

[hogpatrol]

The T7s have some slop in the turret axle. With varying neck tension, the slop may be affecting the depth. I machined the spacer and lock the turret down so there's no slop.
IIRC, the sleeve is not supposed to touch the shell holder. YMMV.

Edit/Correction: The bottom of the die isn't supposed to touch the shell holder.

 

[JFrank]

Neck tension is varied

 

[rockwind1]

Neck tension is varied

but i mandrelled all the necks so they would be very consistent, and i thought they were, at least i measured them and they all seemed the same

 

[JFrank]

Sometimes brass resists sizing

 

[cw308]

I use the Redding Competition Seating die , the sleeve shouldn't bottom out to the die body , there should be some sleeve exposed when set up right , Back out your die until adjustment lines are facing forward position on your press .

 

[JFrank]

redding micrometer seating die with the spring loaded sleeve, t7 press, 6.5 cm, berger hybrids, standard shellholder

set up so there is a slight cam over after shell holder pushes sleeve all the way in.

the primers are below pocket level

and my headspace guage is a mitutoyo with the typical hornady set up and having a recent ocurance with headpspace, i checked these and they are all with .001 of each other.

happily seating some bullets, checking every 2 or three with #26 bullet comparetor in dial calipers, the are running within .001 plus or minus,,, all off a sudden, .oo7 difference, longer, go back, some others are like that.

reset micrometer, get a few good ones, then they start to be to short. not the worlds best digital caliper, but can it be that far off.

what is the best way to measure seating depth with calipers?

what the,,,,**

Why the cam over on a seating Die?
Just curious

 

[Billy 30-06]

Loads that are tightly compressed can push the bullet back out. Try using a drop tube or reduce the powder.
Billy

 

[cw308]

Cam over for sizing brass not for seating with the Redding Competition Seating die .

 

[foxguy]

When you are seating bullets are you pulling the presses arm at the same rate.
If you pull kind of hard and semi fast one time and constant and slow the next you can end up with different bullet seating depths. I have seen this in my own seating of bullets.

Slow and constant till seated has worked better for me.

 

[lpreddick]

When I get seating depth variation it is due to a varying neck expansion as the bullet is seating. The ogive of the bullet goes into the seating stem. I feel the resistance and often I can see seating stem marks on the bullets ogive. If you let that case sit a min, running in back, the seater pushes the bullet that .005 or so that it did not seat initially. I'll usually mark this case and use as a spotter or fouler. Too many like this, it's time to anneal this brass.