Full legnth sizing issues...

[AlaskanGuy]

Very interesting read..... I started reading when my FL sizing dies was actually not sizing my brass correctly..... Very good read....

Bedeviled by Bump — When Full-Length Dies Don’t Work
Here’s a word to the wise — not all full-length sizing dies are properly dimensioned to carry out the important task of “bumping” shoulders back on fired cases. With some dies the task may simply be impossible (without die or shell-holder modification). In fact, you may find that your attempt to bump the shoulder may actually INCREASE the dimension from base of case to shoulder datum!

We recently had some four-times fired 6mmBR Lapua brass. Using a Harrell’s collar that indexes off the shoulder, we measured the length from base of case to top of collar at 1.570″ (with primer removed). We noticed a little more resistance to bolt closure compared to fresh brass, so we decided to bump the shoulders back two thousandths. As a point of reference, we measured the same dimension (base of case to top of Harrell’s collar, primer out) as 1.5675″ on once-fired Lapua 6mmBR brass.

This Can’t Be Right …
To bump our shoulders we had an RCBS Gold Medal bushing full-length sizing die. Per the manufacturer’s instructions, we started with the die backed off 1/2 turn from contact with the shell-holder with the press ram at full height. We lubed and sized one case and then measured it. The shoulder had not moved. OK, no problem, we screwed the die down to contact the shell-holder (at full ram height) and tried again. This time the measured dimension was actually longer by a couple thousandths. The brass which measured (with collar) 01.570″ before sizing now measured 01.572″ — we were going in the wrong direction!

“Bumped” Shoulder Stretched .003″
Frustrated, we screwed the RCBS die in 1/8th turn past touching to allow “cam-over” which is necessary with some presses to actually push the shoulder back. We sized the case again, and this time the dimension had grown another .001″, to a total length of 1.573″! Wondering if there was something wrong with our calipers, we took the full-length sized brass (which previously had chambered just fine) to our 6BR rifle and tried to chamber it. Sure enough, the headspace had been lengthened by .003″ and the brass would not chamber at all.

Die Was Too Long Inside to Bump Shoulders Properly
What was going on? Here’s the explanation: the interior cavity of the die was too long so the shoulder surface inside the die was never actually making contact with the shoulder of the brass — and the die could not be screwed down any further. As the RCBS die, which was fairly tight in the bottom half, reduced the diameter of the brass, the case actually grew in length. While the brass was sized at the bottom it grew upwards because the “shoulder” section on the inside of the die was too high. As we “squeezed” the brass at the bottom it simply flowed upwards, increasing headspace.

With this RCBS die, in its current configuration, there was no way we could bump the shoulder back, even by .001″. The die would likely function effectively if we ground a few thousandths off the bottom, but we don’t think a die user should be obliged to make such a modification.

Lesson Learned: If your full-length die can’t bump your brass even when it is screwed down all the way (to cam-over if necessary), then you need a different die or you need to modify your die. As proof of this, we took out my trusty Redding 6mmBR full-length sizing die. This was set up (from experience), one-half turn off contact with the shell-holder. In that position, the Redding die easily bumped the shoulder of a fired case .002″ with no trouble whatsoever. We started at 1.570″ and ended up 1.568″ — right where we wanted to be. The task that couldn’t be done with the RCBS Gold Medal FL Die was accomplished easily with the Redding die. After lubing the case, we simply raised the ram to full height, and this moved the shoulder back .002″ as measured with the Harrell’s collar positioned on the shoulder.


Comments on the above are welcome....

AG

[Wayne Smith]

Print this out and enclose it with the die when you send it back to RCBS. I'm real curious what they say.

[Doc_Stihl]

There's one other thing to remember. There are different chambers available. If you have a tighter chamber with closer headspace tolerance you could be under SAAMI specs or whatever RCBS is using.

[Taylor]

I have 2 30.06's I load for,a Winchester M70 and a 1917 Eddystone. I have 2 sets of RCBS dies,one new/current and one older set. I use the newer set most often,once loading some ammo for the Eddystone,I found that they would not chamber,but would in the M70.What to do now?Just out of curiosity I re-sized with the older set,they chambered and shoot fine.Both are full length die sets.???,so I use one set for one rifle and the other for the other rifle.(don't mean this as a hijack,just relating an experience).

[fguffey]

Very interesting read..... I started reading when my FL sizing dies was actually not sizing my brass correctly..... Very good read....

Bedeviled by Bump — When Full-Length Dies Don’t Work
Here’s a word to the wise — not all full-length sizing dies are properly dimensioned to carry out the important task of “bumping” shoulders back on fired cases. With some dies the task may simply be impossible (without die or shell-holder modification). In fact, you may find that your attempt to bump the shoulder may actually INCREASE the dimension from base of case to shoulder datum!

We recently had some four-times fired 6mmBR Lapua brass. Using a Harrell’s collar that indexes off the shoulder, we measured the length from base of case to top of collar at 1.570″ (with primer removed). We noticed a little more resistance to bolt closure compared to fresh brass, so we decided to bump the shoulders back two thousandths. As a point of reference, we measured the same dimension (base of case to top of Harrell’s collar, primer out) as 1.5675″ on once-fired Lapua 6mmBR brass.

This Can’t Be Right …
To bump our shoulders we had an RCBS Gold Medal bushing full-length sizing die. Per the manufacturer’s instructions, we started with the die backed off 1/2 turn from contact with the shell-holder with the press ram at full height. We lubed and sized one case and then measured it. The shoulder had not moved. OK, no problem, we screwed the die down to contact the shell-holder (at full ram height) and tried again. This time the measured dimension was actually longer by a couple thousandths. The brass which measured (with collar) 01.570″ before sizing now measured 01.572″ — we were going in the wrong direction!

“Bumped” Shoulder Stretched .003″
Frustrated, we screwed the RCBS die in 1/8th turn past touching to allow “cam-over” which is necessary with some presses to actually push the shoulder back. We sized the case again, and this time the dimension had grown another .001″, to a total length of 1.573″! Wondering if there was something wrong with our calipers, we took the full-length sized brass (which previously had chambered just fine) to our 6BR rifle and tried to chamber it. Sure enough, the headspace had been lengthened by .003″ and the brass would not chamber at all.

Die Was Too Long Inside to Bump Shoulders Properly
What was going on? Here’s the explanation: the interior cavity of the die was too long so the shoulder surface inside the die was never actually making contact with the shoulder of the brass — and the die could not be screwed down any further. As the RCBS die, which was fairly tight in the bottom half, reduced the diameter of the brass, the case actually grew in length. While the brass was sized at the bottom it grew upwards because the “shoulder” section on the inside of the die was too high. As we “squeezed” the brass at the bottom it simply flowed upwards, increasing headspace.

With this RCBS die, in its current configuration, there was no way we could bump the shoulder back, even by .001″. The die would likely function effectively if we ground a few thousandths off the bottom, but we don’t think a die user should be obliged to make such a modification.

Lesson Learned: If your full-length die can’t bump your brass even when it is screwed down all the way (to cam-over if necessary), then you need a different die or you need to modify your die. As proof of this, we took out my trusty Redding 6mmBR full-length sizing die. This was set up (from experience), one-half turn off contact with the shell-holder. In that position, the Redding die easily bumped the shoulder of a fired case .002″ with no trouble whatsoever. We started at 1.570″ and ended up 1.568″ — right where we wanted to be. The task that couldn’t be done with the RCBS Gold Medal FL Die was accomplished easily with the Redding die. After lubing the case, we simply raised the ram to full height, and this moved the shoulder back .002″ as measured with the Harrell’s collar positioned on the shoulder.

Comments on the above are welcome....

AG


sizing, bumping and camming over, then there is “I bumped the shoulder back .002” And, as always I ask: “How do you do that?”

A reloader has a press, it is assumed with the press they have a shell holder and die, or they are like me, I have press, dies and shell holder. Luke everyone else I have more than one set of dies for a particular chamber. I also have dies for the same chamber from different manufacturers. If I have a set of dies that will not size a case back to minimum length/full length sized I can determine ‘WHY’, if a set of dies is out of specs I can determine ‘BY HOW MUCH’. If I have a shell holder that is out of spec. I know it as soon as I measure the shell holder deck height, the deck height of a shell holder is .125”. IO have no infatuation with head space gages because I am a reloader, my dies and presses have threads, threads make my die adjustable in the press.

Anyone with a head space gage should learn to use it, the head space is a standard, the head space is a transfer. A reloader should be able to insert a head space gage into a shell holder then place the full length sizer die over the case then measure the distance from the top of the shell holder to the bottom of the die. With all the guessing and the bad ‘ol’ dies, the absence of a gap should tell the reloader the die can not size a case because the die hits the shell holder before it hits the shoulder of the case, meaning a reloader can screw the die in an additional 2 turns (.142” +/- a few) with out sizing the case because the case the die can not be crushed.

The reloader wants a gap between the shell holder and bottom of the die when the die is supported by a head space gage. It should not be new news to a reloader the chamber is longer than a minimum length case. The go-gage is used to determine the length of the chamber from the shoulder of the chamber to the bolt face. The size case is shorter from the shoulder of the case to the case head. How Much? A reloader should know, I am a reloader, I know, I start with measuring the length of the chamber, I am not concerned with SAAMI’s chamber, I am only considered with my chamber.

Being a reloader gives me a leg up on case forming, back to measuring the length of the chamber from the shoulder to the bolt face: Once a reloader understands the methods and or techniques for measuring the length of the chamber the reloader can use the measurement to adjust the die to the shell holder. As a reloader I have options, I size cases for short chambers without grinding the top of the shell holder or grinding the bottom of the die. Meaning? Anything after bumping makes no sense. I can raise the case head up and off the deck of the shell holder by placing a feeler gage between the deck of the shell holder and case head. Rising the case head increases the ability of the die and shell holder to size the case or as it is said ‘reduce the length of the case from the shoulder to the case head’ Going the other way, I use a feeler gage to adjust the die off the shell holder to increase the length of the case from the shoulder to the head of the case. I could purchase Redding Competition shell holder for $40.00+ a set. slight problem. maximum increase from the deck of the shell holder is .010”. I have chambers that require .014” added to the length of the case from the shoulder to the head of the case because one of the chambers is .016” longer than a minimum length sized case, or as they say, the chamber is .002” longer than a field reject chamber. The next question should be: “Where would a reloader find a case long enough to form for a chamber that long?” I use 280 Remington cases, the 280 Remington is longer from the shoulder to the head of the case .051” than the 30/06, a reloader/case former should have no problem forming the case to fit, all that is required is for the reloader to know when to quit sizing.

Bumping? When I form a case the shoulder is not bumped, it is erased, the shoulder does not move, the new shoulder is formed, to understand? Scribe the case body/shoulder juncture, after forming look for the scribe mark.
Stretch when fire forming, same thing, look for the scribe mark.

F. Guffey

[Char-Gar]

I have not had dies from a major maker that were too long, but I have had a couple that were too short. A case full length sized in one of them produced rounds with too much headspace and all the issues that brings.

[fguffey]

http://www.saami.org/PubResources/CC_Drawings/Rifle/270%20Winchester.pdf

I posted a link to the 270 Winchester case and chamber. There is a head space symbol indicating head space on the chamber drawing. The case drawing does not have a symbol for head space, meaning the case does not have head space, the case has length, the three lengths a reloader should be familiar with is case length from the mouth of the case to the case head and from the shoulder/datum to the case head and the length of the case from the shoulder/datum to the case mouth.

F. Guffey

[bbqncigars]

I think that post #1 would explain why the RCBS die won't size my 50BMG brass enough, but the Lee die will. AFAIK, there is no SAAMI spec for civilian ammo/chamber for that cartridge.

[fguffey]

"This Can’t Be Right …
To bump our shoulders we had an RCBS Gold Medal bushing full-length sizing die. Per the manufacturer’s instructions, we started with the die backed off 1/2 turn from contact with the shell-holder with the press ram at full height. We lubed and sized one case and then measured it. The shoulder had not moved. OK, no problem, we screwed the die down to contact the shell-holder (at full ram height) and tried again. This time the measured dimension was actually longer by a couple thousandths. The brass which measured (with collar) 01.570″ before sizing now measured 01.572″ — we were going in the wrong direction!"

The OP backs the die off 1/2 turn (.0357" or 180 degree). He could have backed the die off 1/4 turn (.0178" or 90 degree), Point? There is a difference between full length sizing and sizing a case with the die adjusted off the shell holder. Then he adjusted the die to the shell holder (still??) adjusting the die to the shell holder is not full length sizing or as I say "restoring a case back to minimum length", problem, he did not measure the length of the case from a datum/shoulder before firing.

Then he has a problem with the case getting longer, I ask: "Why wouldn't the case get longer from the case head to the shoulder? When the case body is sized the case body is reduced in diameter, when the case body is reduced in diameter the shoulder moves forward, when the shoulder moves forward the case body increases in length. SO? He was not going the wrong way, he adjusted the die down to the point the die was able to start full length sizing. Had he adjusted the die down to contact with an additional 1/2 turn (down) the case could have shortened from the shoulder to the head of the case and got longer from the mouth of the case to the head of the case.

50Cal BMG, I was asked to help, the builder/reloader was having trouble sizing 50 Cal cases, I boxed up a few things knowing if I changed any of his methods and or techniques I would find myself wasting a trip. He uses Imperial sizing wax and or Dillon in a can or bottle. He has spent so much time hyping Imperial he will not consider a lube that is not on anyone's approval list.

I lowered the sizing die an additional 2 turns on an Ammo Master press (.1428" below contact) With the ram up to maximum there was a .014" gap between the bottom of the die and top of the shell holder, The .014" gap meant the case did not get pushed into the die, and I thought he was going to brake the press when raising the ram and lowering the ram, pulling the sizer plug through the neck was not much easier. basically all I was allowed to do was watch. I was allowed to improve on his case cleaning methods. I offered to make gages for his 50 Cal rifle. I did make a comparator, problem with a comparator, it does not size cases.

F. Guffey