WTK: Forster UM Adjusting Seating Dept?

[samnev]

Following the set up on the instruction sheet for the Forster Ultra Match seating Die. Screw die down to shell holder. Adjust seating stem to approximate seating depth. Then Use micrometer for desired depth.
I'm seating Sierra 52 grain SMK's Lyman manual calls for seating depth of 0.148 for COAL 2.25.
Using the proceedure I get a depth of 0.135 for an COAL of 2.25.
Am I'm doing somehting wrong?

2nd question, when changing to 69 grain SMK's do I have to reset the seating stem then reset the micrometer to the desied depth.?
These dies are new to me so forgive me if I seem dense.
TIA

 

[KYpatriot]

Re: WTK: Forster UM Adjusting Seating Dept?

If you are getting the correct COAL then you are good. I am assuming you are using calipers fitted with a COAL gauge to check for the desired 2.25 COAL. You can expect that <span style="font-style: italic">each bullet</span> will need a slightly different micrometer setting on the die to achieve a constant COAL on your calipers. This is because the ogive is not exactly the same for each bullet. I will purposely set them slightly long, take the cartridge off the press and check with the calipers, find that it is for example .004 too long, adjust the micrometer .004 and then reseat. Each round will be the same length to the ogive this way according to your calipers.

The answer to your second question is yes, because as I explained above the bullet ogive length is not even consistent in the same box of bullets much less between bullets of different weights.

 

[samnev]

Re: WTK: Forster UM Adjusting Seating Dept?

Thanks for the response. That's what I have been doing. I just thought the UM die would do alliviate the constant resdjustment my regular RCBS seater die required. I was pretty sure the seater would would have to be readjusted for each bullet type.
What supprised me most was the variation in bullet length with the 52 & 69 grain SMK's. The variation in was as much as +/- 0.005".
I spoke to Sierrra about this and their answer was "we are the best in the ib=ndustry" but variations in the manufacturing process causes the differences in bullet length.

 

[KYpatriot]

Re: WTK: Forster UM Adjusting Seating Dept?

Yeah, but to me the micrometer style seaters make this process as quick as it can be if you want that kind of accuracy. The bullets will vary in overall length and in ogive length too. I guess that is the way it is unless you got to solid cnc lathed turned projectiles....

 

[BobinNC]

Re: WTK: Forster UM Adjusting Seating Dept?

Everybody has a different procedure, depending on one's goals. Mine is maximum accuracy combined with reliable feeding from a mag. box. I no longer own any single shots, so reliable feeding from a mag is my goal.

My COAL is set at least 0.010" LESS than my max box length. This allows for the normal 0.005" variation in bullet length. Then I don't have to reseat rounds that come out a little long, as they will all work.

I'm not a benchrester so chasing the last .10" of a group is of no use to me. I'm more interested in "minute of steel plate" or "minute of beast"......

Bob

 

[Fuzzball]

Re: WTK: Forster UM Adjusting Seating Dept?

"Am I'm doing somehting wrong?"

Yeah. I think. Sounds like maybe you expected the die's calibration to match a book OAL number? Won't happen. The die will only give you relitive numbers, the only precision the calibrated head can provide is the amount of change you dial in.

 

[samnev]

Re: WTK: Forster UM Adjusting Seating Dept?

As I said I am new to this die and had do do exactly what ypu said. dial in the correction. Just wanted to know waht the story was. It never hurts to ask those who know infinately more than I do.

 

[Fuzzball]

Re: WTK: Forster UM Adjusting Seating Dept?

"It never hurts to ask ..."

None of us were born knowing any more than you, we had to learn too. Glad we can help.

I wish the net had existed when I started and had no one to ask anything; it would have saved a lot of use of my bullet puller!

Ref "OAL"; don't sweat that for great precision. As Sierra said, the bullets themselves vary. No rifle knows or cares where the tip of a bullet is anyway.

All that matters to a rifle is how far the bullet travels prior to rifling contact and even that isn't nearly as critical as some think; the "best" shooting depth is a range, not a spot measurement. Within the good shooting range, which can easily be 10 to 20 thou wide depending on the rig and load, small OAL differences won't matter at all.

Same thing applies to powder charges, by the way. I only do precisly weighed charges for load development. Not only do I learn what shoots good, I learn how wide the good shooting window is.

Find a load's good range for both powder charge and OAL, seat and charge in the middle of it and you won't get twitchy accuracy.