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Case head seperation

I use this,for head space,and bullet seating. http://www.midwayusa.com/viewProduct/default.aspx?productNumber=479704 Great little tool! ;) I had case head sepration alot with a contender pistol,but after setting up my dies with this,it's a thing of the past! Best money I ever spent! Using smaller bushings,you can measure the COL. of your rounds to the ogive. I just seat a bullet long,close it in the action,measure,then set the seater where I'm .004-.010 back and your set! Ron
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One little tip for when you are using a tool to measure bump (the right way to do it):

Loads of moderate pressure may not leave a primer flush with the case head.

To check for this, take a swipe across the fired primer (while in the case) with a fine file, to eliminate any crater, measure the fired case, remove the primer with a punch, and then remeasure. If the second measurement is less than the first, your load is probably a light one, and you probably need a case that has been fired a couple of times without Fl sizing, and a hot load, as a die setup reference for that rifle (or barrel, if it is a switch barrel).

A faster way to see the same thing (after first removing any crater) is to capture the case between the jaws of a dial caliper, with one jaw across the center of the case head and primer, and hold it so that there is a light source is behind the case head. This will show a gap on both sides of the primer if it is not flush with the case, and you can do the same measure and remeasure after depriming to determine how far the primer protruding.
 
CanusLatransSnpr said:
The dies that intrigue me, haven't tried one yet, are the Forster bushing bump dies. Could be wrong but, the way I understand these is they neck size the case and bump the shoulder a bit, leaving the rest of the case fireformed so to say. Is this right? Would there be a need for full length sizing eventually using this type of die? Just curious.

I use one and that is correct. I actually use the bump die with the neck bushing removed to measure the length of the cartridge. Fired and not sized cartridges fit just as well as sized cartridges. Both hit hard against the shoulder in the die. I just measure the overall length of the die and cartridge and adjust until the bumped length is 0.001" shorter than fired.

I've loaded my cases 5 times and have found no hint so far that they need body or FL sizing. I only size 2/3 of the neck, by backing off the bushing follower.

If you think you have a problem with potential case head separation, all you need is a piece of wire with a small 90 deg. hook at the end. Slide it up and down the inside of the case and it is quite easy to feel that thin spot developing.
 
Re: Case head separation

Here is a picture of another example, this time in .223 caliber. This brass had been sized to bump the shoulder back by .011, and the "stretch marks" and separations occurred on the second firing of this brass.

Note the shiny line on the outside of the case wall at the top of the picture, corresponding in location with the complete separation in the case just below. The bottom case (sectioned) shows the internal thinning of case wall, indicating an incipient separation. At the bottom is a tool made from a paper clip that you can use to "feel" for the internal case wall thinning.

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Randy Sikes
 
Since were showing case head separation here’s one from my trg 300 win mag, this case was on its 12 reload. Just as a trial I wanted to see how many reloads I could get.
I neck sized for 5 and then body sized on the 6 using Redding bushing comp set and Redding Competition Shell holders keeping head space tight.
 

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Below is a animated .gif image of a .303 British cartridge being fired. At maximum military headspace and with American made commercial cases you can have as much as .016 head gap clearance or air space between the rear of the case and the bolt face. (remember you are within military headspace limits)

headspacestretch-1.gif


A trick a Canadian Enfield shooter showed us in a Enfield forum was to fire form our cases with a rubber o-ring around the base of the case to hold the case against the bolt face.

headspacestretch_frame_0001.jpg


After the case is fire formed the case will headspace on the shoulder of the case and care must be taken to not push the shoulder back more than .002 to prevent thinning in the web area.

fireformed-zeroheadspace.jpg


On a non-rimmed case knowing where your headspace is set at and what your cartridge headspace is will prevent the first initial case stretching. Seating your bullets long to hold the case against the bolt face or creating a false shoulder will prevent this.

Another tool you can use is the RCBS Precision Mic to measure your cases before and after firing.

IMGP5130-1.jpg


You can throw your paper clip away if you have a RCBS Case Mastering Gauge and you can actually measure how much thinning is taking place.

IMGP5204.jpg


Just remember the thinning and stretching in the web area can happen on the first firing and not just from over full length resizing.
 
A couple of tools that work well for this process is the sinclair decapping tool, it will knock the primer out without touching the case dimensions, works well if like me youe size brass right before you load, I can push the primer out and clean up the pocket and then not worry about sizing and loading until a more convienient time.

The redding instant indicator, I find this really good when used with an RCBS partner press for measuring shoulder bump, the hole in the case holder eliminates any issues with the primer being crated or slightly raised throwing readings off. A slight readjustment of the dial and I use it to measure the seating depth of my loaded rounds as well...I measure every loaded round as it is very quick.

BTW thanks for the awesome pics on the separation...it is a real help to truely know what to look for.
 
One thing to Note. Sometimes in a mild load, it takes 2 to 3 firings for the virgin case to be at full length and only then does the Full length doe need to be set to set back the shoulder. One way to find this out is to stick your once or twice fired empty brass in the rifle. If the bolt closes hard its time to set up your shoulder bump die or Full Length die to bump the shoulder back. If the bolt closes easy just neck size it and shoot it again. I take the firing pin and spring out for this job.

If you set your die off the virgin brass after the first firing you may be seting the shoulder back alot more than what you think your setting it back.

RussT
 
Great thread Russ,
Here is a description of what I use to accurately measure shoulder set back. Every time I get a new barrel, and as most of you know the gunsmith cuts off an inch+ off the muzzle end and tosses it in the scrap bin. I have him take that piece and after he is done chambering the bbl. I have him chuck it in the lathe and run the same reamer into the stub to the depth of the shoulder/body junction. I'll then mark the caliber on the stub, and now I have a true reference point to set up my dies to give me the absolute minimum shoulder set back for the cartridge. After firing a few rounds, slip the stub over the neck, and it will firmly contact the shoulder. Take an average measurement with your calipers and record it. Now set up your dies so that when you recheck it, the shoulder has been bumped by .001+.
I hope this helps,
Lloyd
 
One little tip for when you are using a tool to measure bump (the right way to do it):

Loads of moderate pressure may not leave a primer flush with the case head.

A Davidson base helped me with that issue, also seem to get more consistent measurements with it. The Sinclair inserts for ogive and shoulder measurements are made out of stainless not alloy like the hornady so they won't wear.
 
A Wilson Case Gage is a tool every reloader should have on their bench. It makes it very easy to check for proper sizing of the case. Midway and Sinclair both sale them.
 
K22: Your rifles chamber is the best "gauge" to measure headspace lengths by using one of the excellent tools out there, like the one made by Larry Willis/ Innovative Technologies. The case gauges made by Wilson, Dillon, etc. tell you only if the case is within SAAMI specs. I stopped using them many years ago.
 
I own Savage rifles and I don't have this problem
I full length size a case then set head space to that case then my head space and die are the same. I don't have to buy a lot of other tools to see what is what.
I did have a head seperation once but it did not hurt anything. but that was before I had my savages.
 
"case head separation" like 'donuts' are the results of bad habits, not the least of which is, Chamber a round, close the bolt then pull the trigger, not even the Shadow knows what is going to happen. The bad habit is chambering a round in a chamber without knowing the effect the chamber is going to have on the case when fired. If reloaders got out of the bad habit if firing first to determine the effect the chamber had on the case when fired and instead measure the length of the chamber to determine the effect the chamber 'WILL HAVE' on the case when fired they, the reloader could off set the effect of the chamber by increasing the length of the case.

Then there is the bumping thing, again, that sounds like an accident, I form cases, when forming the shoulder does not move it is erased, for example I form 8mm57 cases from 30/06 cases, by definition reloaders claim the shoulder is moved back, that does not happen, the shoulder does not move, part of the shoulder becomes part of the neck and part of the case body becomes becomes part of the shoulder, had the shoulder been marked the reolader should notice the neck shoulder did not move, it was erased and formed .121 thousands further back, there could be a bump theory as bump ends and forming begins after the shoulder is moved/formed/bumped back .00??thousands, for me? that does not happen, if I had a shoulder bump die??? I would want to measure before and after, I have a pile of datums, to determine if the effect of bumping the shoulder back caused the case to squat/bulge/expand, and that is the reason I form cases with case body support with the versatile full length sizer die, I would not need the support if bumping was effortless, reloaders as in reloading is the only group that can move brass back without support, except me, I can not do it, but I use datums, I measure before and after, and, my favorite die is the versatile full length sizer die.

The difference between case formers and reloaders, reloaders fire to form, a case former will forme a case to fit the chamber then fire. The case former will eject a case that is once fired, the reloader claims they eject a fire formed case, and, that is ware case head separation starts, a case former knows the length of the chamber and cuts down on all that case travel, as to determining the length of the chamber, again, the shoulder on the 8mm57 is .121 further back than the 30/06 shoulder (in the perfect world) I do not live in the perfect world so when forming the 8mm06 I back the forming die/full length sizer die off the shell holder .010 thousands, after forming and full length sizing with an additional .010 thousands added between the case head and shoulder I attempt to chamber, if the case does not chamber I reduce the case length an additional .002 thousands and continue the process until the case chambers. Verify? I use the companion tool to the press, the feeler gage, I make the adjustment of the die to the shell holder with the feeler gage, bad habit, cutting it too close (or showing off), I have one rifle Eddystone M1917 with .016 thousands head space, I form cases for that chamber using 280 Remington cases, the shoulder is forward of the 30/06 by .051 thousands, I adjust the gap between the bottom of the die and top of the shell holder to .014 thousands, then attempt to chamber, remembering the case length is no longer 2.494, I add the .014 thousands to the length of the case between the head of the case and shoulder.

Bad habit, is not knowing the length of the chamber from the bolt face to the shoulder of the chamber, for most it is too much work, and commercial, if a reloader knew how to determine the length of the chamber and was able to use standards and transfers they would not need all the after market tools dies, cases and chambers.

I use the companion tool to the press, the feeler gage for transferring, standards and verifying.

F. Guffey
 
Very interesting fguffey, Thanks for sharing.

Where can I get a some of these datums you use?

Once you get everything the right size, fire and re-size, do you have too trim the case?
 
A couple of issues have been brought up.

The reason that doing it by feel is not a good overall approach is that it assumes that the die is correct for the chamber. It may not be, and if it is a little too big, you will end up pushing the shoulder too far back to get the feel you want.

Being able to get away with a bump die is strictly an issue of how much pressure you load to. Generally, I am on the side of closely fitted FL dies, used every loading, but to be fair, a friend, who uses a grain less powder than I in his PPC has gotten many firings with just bumping. With my load (more typical), I cannot. Looking at his results, I may try his load :D

As to types of gauges, I prefer those that yield measurements in thousandths, over the Wilson variety, particularly since I am shooting for a .001 bump, for most of my applications.

When I set up a die for bump, I use a reference case that has been fired till the shoulder to head measurement has stabilized at its maximum, not a once fired case, and I use a punch to remove the primer before measuring. The primer can easily spoil your precision, with even a slight crater or protrusion.

As to how we got buy all those years without gauges... In the past, dies that were in common use were of the one piece, expander ball variety, that over sized the whole case, and may not have even been able to bump the shoulder of a fired case. Because many calibers (like the '06) have a relatively small shoulder angle, they will chamber without much effort, even if the shoulder is not bumped, as long as the body has plenty of clearance. A die manufacturer once told me that what made small base dies different was not necessarily that they were smaller at the base, but that they were short enough to allow shoulder bumping sufficient for sizing cases for the requirements of a semiautomatic rifle. Given this, it is not coincidental that something like a Wilson gauge is an integral part of setting up one of these dies for a Garand or M1A, where generous bump is required, and the dies will allow for that to be over done.

As an aside, let me say that I am always amused by reloaders that agonize about a tenth of a grain of powder, and are so sloppy about other aspects of their reloading that may matter more for obtaining best accuracy. It is a common phenomenon.

One last piece of advice...Straighten out a large paper clip and bend 1/8" of one end at 90 degrees. Learn how to use this "tool" to feel the interior groove, near the base of a case, that is a positive indication that excessive stretching has weakened a case. Cases that fail this test should have their necks crushed (to prevent its being retrieved and reused) and be discarded.
 
BoydAllen said:
....

One last piece of advice...Straighten out a large paper clip and bend 1/8" of one end at 90 degrees. Learn how to use this "tool" to feel the interior groove, near the base of a case, that is a positive indication that excessive stretching has weakened a case. Cases that fail this test should have their necks crushed (to prevent its being retrieved and reused) and be discarded.

This is excellent advice. See reply #23 above for picture of the paper clip tool.

An even more sensitive test for finding the internal stretch ring is to decap the case, then shine a small bright LED flashlight through the flash hole. When you look into the case through the case mouth, you can seen the internal stretch ring (case thinning) as a bright ring. This works best when you have thoroughly tumbled the cases and the inside case walls are clean. I have found a number of these stretched cases using the light method that initially tested negative using the paper clip tool. It was only in retrospect that I could feel the subtle stretch ring with the paper clip tool in some of these cases.

I think that .223 cases are particularly vulnerable to this case thinning of this type. Most .223 case walls are thinner than other cases (.308, 6BR, etc.). At least this is true for "standard" .223 cases. Lapua .223 cases are much thicker than others, such as Lake City, Remington, Winchester and so on, and I suspect (but can't prove) that Lapua .223 cases are less susceptible to case thinning and case separations than other brands of brass.

Randy
 
"As to types of gauges, I prefer those that yield measurements in thousandths, over the Wilson variety, particularly since I am shooting for a .001 bump, for most of my applications"

I use the L.E. Wilson case gage, it yields measurements in thousands in increments of .001. I have a set-up table for a flat surface and the companion tool to the press the feeler gage with the Wilson case gage, or a straight edge and the companion tool to the press the feeler gage with the Wilson case gage, I could use a depth gage/dial caliper but the straight edge and feeler gage works, (Redding calls it a thickness gage), the advantage to the feeler gage comes in handy when I use it as a transfer gage, or to verify an adjustment.

Again there is datums, the Wilson case gage has a datum, it is round with a radius (convexed), the 30/06 datum/radius is 3/8 inch or .375. (contact point between the case shoulder and case gage, again, I make datums, I collect datums, I purchase datums.

To check the datum of the Wilson case gage insert a case, then with a soft drift that is smaller in diameter than the case head, hit the drift with a hammer to drive the case into the gage, (a large hammer is not required) (and placing the Wilson gage on a lead block is a good ideal) when the case is removed the shoulder will be concaved.

F. Guffey
 

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