I was working on a ladder test load the other day. I tried relying on the .001 marks to adjust my seating depth. When I measured from B-O on the loaded rounds, those marks didn’t translate into 1/1000“of movement. Has anyone else encountered similar difficulty? Could the differences be caused by a rough seating stem ?
Forster micrometer seater
- Thread starter Topwater
- Start date
I have.. Usually the seating stem. Using a standard stem to seat VLD bullets can cause inconsistent seating. I've used Redding, Whidden and Forster micrometer seaters. All were consistently inconsistent, even when I used the correct seating stem. I had Whidden make custom stems for the bullets I used. No joy....I now use a Wilson seater and an arbor press. Very consistent. It will move a bullet in .001 increments.
PopCharlie
PopCharlie
Last edited:
Arbor press is the way too go. Just my two cents Tommy Mc
I never trust any of them if you're trying to get exact measurements. Just the backlash in the threading with cause off readings. Go arbor press or always measure them. After a while you will learn the die and get close to your goal.
wkdickinson
Gold $$ Contributor
Here is a thread that offers another perspective:
Bullet Base to Ogive Grouping
I know this topic has been discussed many times and I have read most of the threads regarding it, but I haven't seen much regarding how people actually group their bullets. I just measured 200 Berger 105gr Hybrids all from the same lot, using a Hornaday comparator mounted on a Mitutoyo...
forum.accurateshooter.com
I had bad luck on Forster Micrometer seating die. I got from 1.801-1806", its stem also soft and thin. no compressed charge loading, or un annealed brasses. My L.E. Wilson dies are on my way.
Could it be just the variation in bullet length?
wkdickinson
Gold $$ Contributor
I think it’s more the variation in the ogive between “production” bullets. The place where the seating stem engages the bullet ogive is significantly different from where the comparitor does.
HTSmith
Silver $$ Contributor
They can only be as accurate as the threading and that includes Wilson--though the lock screw on the Wilson may make it less susceptible to backlash. I don't trust any of them 100%. When making a big adjustment I'll leave .005 to .010" long and sneak up on the last little bit.
This also depends on your end goal. If you have a bullet that like a specific jump in very small tolerances, then it's more critical. However, if you have a jump tolerant bullet then a few thousands won't matter much. I try hard to make everything I load jump a little because I hate jamming bullets and I have a few that really like a huge jump, .070 or more.
The reference marks are just that ... they get ya close.
Seating depth varies for a variety of reasons, like neck tension variation, powder compression with bullet, bullet variation, brass spring back variation, operator measurement variation, the quality of the tools used , etc. So .001 thou variation never bothered me. Had to re machine the Forester micrometer seating stem...it was too thin and started swaging out when seating, seating depth was changing. Made it thicker by cutting it down and re pointing it and lapping it for the Berger bullets in the lathe. Also use a Wilson neck sizing mandrel, and now the Forester seating die works great no heavy compressed loads though...checked it for runout against the dasher Wilson seater...both were great, for runout.
wkdickinson
Gold $$ Contributor
An easy way to illustrate this is by starting with 20 identically prepared cases, then seating 20 of the same "production" quality (Berger, Sierra...) bullets in all of them using a quality seating die, a Forster in this case, without touching the seating adjustment, so all 20 were seated exactly the same way. Then using your comparator, measure the CBTO of each. I think you will be very surprised at the variation you find.
The variation can't have come from the die, since it was never adjusted during the seating operation, so it is static. I suppose some of it could come from variations in the neck friction case to case, but I think that is unlikely, if the cases were prepared identically.
I have done this test, and found the results disconcerting to say the least. What would be really interesting would be to then do the same test, on the same equipment, but using custom bullets, such as Bart's.
BoydAllen
Gold $$ Contributor
When a jacket and core assembly is pointed up, depending on a couple of factors the resultant ogive can vary a little. This results in variation in the distance between where the seater stem touches and your ogive to base insert makes contact. This variation translates directly into corresponding variations in ogive to head measurements. Another contributing factor is spring or stretch in the press linkage, that can vary from seating to seating.
Last edited:
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.