Another Newbie Question About Partial Length Resizing


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beartooth91
June 3, 2010, 06:18 PM
I'm in the process of working up another load for my new, frustrating .243 (or maybe its the frustrating Sierra 70 HPBT Matchking) and used up all my new brass. I was 3 cases short, so, I decided to try partial length sizing a few of my once-fired cases.
I'm using Hornady dies and the sizer was adjusted so the bottom of the die contacted the shell holder at its max height (just before camming over). This is how the Hornady instructions specify (no additional turns afterwards like my old RCBS).
So, I backed the die off a full turn and started working my in 1/16th of a turn at a time, checking chambering after each adjustment. What I found was "resistive-chambering" (if that makes sense) until the die contacted the shell holder, then normal chambering with no resistance. With the die backed off, the chambering required a little force, but, I wouldn't call it difficult - just a little resistance. And, I can chamber an un-resized fired round with roughly the same resistance or just a bit more.
So A) I'm not sure how to adjust the die with the above results, B) how much chambering resistance is ok, and C) can a .243 be partial length resized? I seem to recall an old Speer manual saying the .243 can only be full length of neck sized.

Thanks,

Mark

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ranger335v
June 3, 2010, 07:05 PM
"A) I'm not sure how to adjust the die with the above results,"

Size for results, not by a formula. Doing that requrires a gage. You can use the chamber itself as a gage, all you want to do it allow the bolt to close with little effort. Hard or no resistance chambering are both poor practice.

A calibrated case head space gage like the RCBS Precision Case Mic or Hornady's LnL tool used on a dial caliper or the Innovative Technoligies dial indicator tool allows us to precisely measure what we are doing. Since even 1/16" turn makes for a pretty large sizing change, about 4.5 thou, or well over half of the proper full headspace tolerance you can see that such a precision gage is a great asset when adjusting a sizer for ideal headspace.

All we really need to do it measure the location of the fired shoulders and restore them to that length when sizing. Going further only increases the potential for excessive case stretching.


B) how much chambering resistance is ok,

That's for you to decide, it's not critical. If the shoulder is properly restored there will be no more resistance to chambering a loaded round than a fired empty case.


C) can a .243 be partial length resized? I seem to recall an old Speer manual saying the .243 can only be full length of neck sized.

So called "partial resizing" can be done on anything. There's nothing unique about the .243 - or anything else.

I perfer the term "custom resizing" meaning my cases are precisely sized to fit my chamber properly. "Partial resizing" is a loose term, it's virtually meaningless and means anything less than jamming a case into the sizer as far as it can go. IMHO.

243winxb
June 3, 2010, 07:21 PM
Put a shim made from a soda can (about .004" thick) between the shell holder and FLRS die when adjusting it. Put a hole in the shim for the decaping pin. If your bolt closes with a little resistance your ok. If you feel nothing, use 2 shims. If bolt will not close, get rid of the shim. Or you can buy these tools http://www.brownells.com/.aspx/lid=11470/guntechdetail/Gauging_Success___Minimum_Headspace_and_Maximum_COL For a load with that Sierra 70 HPBT Matchking try IMR 4064 or IMR 4350 :) Plus a little lube on the bolt lugs will not hurt. Break Free CLP

steve4102
June 3, 2010, 07:43 PM
Full Length Resize(P-FLR).

1. Put the Shell Holder in the press and raise the ram.

2. Screw the Full Length(FL) Die into the press so it is about a "nickle's thickness" above the Shell Holder.

3. Lube a "Fired" case (walls and inside the neck) and squash it.

4. Remove the Lube and try closing the bolt on it in the chamber.

5. If the bolt closes with no resistance, screw the FL Die into the press about 1/8-1/4 turn and repeat steps 3 & 4.

6. As you feel the resistance begin, slow down how much you screw the FL Die into the press so you are at about 1/16 of a turn, or "Fine Tuning". At some point you will not be able to close the bolt and you are extremely close to having the FL Die in the proper position.

NOTE: The reason for this is because the FL Die has begun Resizing the Case-walls down to the Pressure Ring. As it does so, the Case-body lengthens slightly which in turn moves the Case-shoulder slightly forward. Then as the "Fine Tuning" continues the Case-shoulder makes contact with the FL Die and is moved slightly reward(or slightly shortens the Case-head to Case-shoulder dimension).

7. Stop when there is a slight bit of resistance when closing the bolt on the empty case. You now have a "slight crush fit" for the case in that specific chamber, or Zero Headspace.

8. Once you get it where you want it, take some masking tape or a black marker and put a Witness Mark where the FL Die Lock Ring is positioned to hold the FL Die in this position. Loosen the FL Die and return the Lock Ring to align with the Witness Mark and sung up the Set-Screw.

Screw the FL Die back into the press and try squashing another case. It should have the same resistance as the previous one. If not, you need to re-adjust the Lock Ring so it does. But you are extremely close to where you want it, so make very small changes at this point.

beartooth91
June 4, 2010, 07:32 AM
5. If the bolt closes with no resistance, screw the FL Die into the press about 1/8-1/4 turn and repeat steps 3 & 4.

6. As you feel the resistance begin, slow down how much you screw the FL Die into the press so you are at about 1/16 of a turn, or "Fine Tuning". At some point you will not be able to close the bolt and you are extremely close to having the FL Die in the proper position.
I am thinking I want to back the die out, not screw it further in...?
For a load with that Sierra 70 HPBT Matchking try IMR 4064 or IMR 4350
I thought good 'ol IMR-4064 would be the ticket also, but, I shot 5 groups on Wednesday with loads from 39.4 grns to 41.0 grns. The 1st three were right at 1 inch. Group 4 was 15/16 inch and group 5 was 1-3/4 inches. The rifle is a new Savage model 11FHNS with the Accustock, so, I have high hopes. I'm gonna try some loads with H414 (and maybe H380) next. The throat in this rifle is long enough that I can't even approach the lands (I like to seat .020 back) with this bullet, so, I'm seating to the recommended 2.625" COAL. I'm guessing the longer and heavier bullets will give me better results.....

Walkalong
June 4, 2010, 08:19 AM
One sure way is to get some sort of tool to measure where the shoulder is and bump it back a couple thousandths. RCBS makes a nifty set up (http://www.midwayusa.com/viewProduct/?productNumber=375435), , but there are numerous cheap alternatives as well.

Link (http://www.thehighroad.org/showpost.php?p=6270171&postcount=1)

Plenty of articles around the web.

If you are going to do it by "chambering resistance" remove the firing pin assembly from the bolt. People have been doing it that way for years. (decades)

243winxb
June 4, 2010, 09:19 AM
Seating depth- Have the base of the bullet (full diameter, not boattail.) at the neck shoulder junction. Forget about trying to seat into or near the lands. With a 70gr and IMR 4350 & 4064 you need to build pressure for these slow powders. For better accuracy, try some Berger bullets.

fguffey
June 4, 2010, 10:28 AM
You screwed the die down to the shell holder and sized a case then you chambered it, it chambered, then you backed the die out 1 turn (.071 thousands) and neck sized the next case, that is what I do except when I back the die out one turn I pass up 71 opportunities to to size a case and form the case with a shoulder exactly where I want it.

Because adjusting the die down to the shell holder is full length sizing on all of my presses that use dies and shell holders, I start by backing the die out and measuring the amount of 'back off'. When the die is backed out an air gap appears, the gap is relative to the fractional turn of the die in thousands, it is an easy way to convert fractional guesstimates of a turn to thousands (on my presses, dies and shell holders), because I understand this concept I skip the guesstimate of a turn and go straight to the feeler gage to establish the air gap in thousands, (feeler gage: the companion tool to the press).

Not all presses are equal, when sizing for the perfect chamber I know a full length/minimum length size case will chamber with .005 to spare, I know by adjusting the air gap between the bottom of the die to the shell holder I can control the amount of sizing between the head of the case to the shoulder (or reduce the amount of sizing).

I use the versatile die, the full length sizer die, I have neck sizer dies, small base dies, BAR dies etc., but because the full length sizer die has varying diameters adjusting the die down moves the shoulder back and reduces the diameter of the case ( changes the apex created by the angle of the two sides). What this means when controlling the location of the shoulder in relation to the head of the case the case body diameter is also being controlled, difference? when the case fits the chamber after firing the pressure gets serious, full length sizing? the pressure can not get serious until the case fits the chamber if time is part of the factor.

I would recommend a .004 thousand gap between the bottom of the die and top of the shell holder to start with, with the perfect chamber .003 thousands should work for sizing and chambering with little or no resistance to chambering, I am not a fan of resistance to bolt closing because there is more than one reason for a bolt to close with resistance.

F. Guffey

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