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Old November 25, 2012, 06:16 PM   #26
SEHunter
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hypotheticaly, if the chamber of a belted cartridge has excessive headspace, can this be remedied by using a FL die set at the length of a fired case, thus using the shoulder to headspace the case as if it were a standard rimless bottleneck case?
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Old November 25, 2012, 07:44 PM   #27
Bart B.
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Yes.

You're referring to what's called "shoulder clearance." It happens with new belted cases when they're all the way into the chamber and their belt's against its shoulder in the chamber. When such a case is fired, it's shoulder gets pushed forward against the chamber shoulder and its head gets pushed back against the bolt face. That leaves a small gap between the belt and its chamber shoulder. This also happens with rimmed bottleneck cases such as the .30-30 WCF. As long as shoulder clearance is within specs, it's OK.

Lots of folks use an RCBS Mic to measure fired belted case shoulder headspace. That Mic is set up to do that for belted cases. Setting those cases' shoulder back 1 to 2 thousandths typically lets them headspace on their shoulder instead on their belt. Best accuracy happens doing this. I've been doing it for decades.

Last edited by Bart B.; November 28, 2012 at 04:21 PM.
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Old November 25, 2012, 07:44 PM   #28
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Here's a good article on using the RCBS Precision Mic:
http://www.realguns.com/archives/035.htm
There are several good videos available showing the use of Hornady's Headspace gauge set on youtube.
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Old November 26, 2012, 10:35 AM   #29
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Bart,

Glad you put the glossary in there. I think I'm going to put some direct links up to that and SAAMI's drawing and specs and make a separate reference sticky out of it.


Mr. Guffey,

JRLSH has his account set with receipt of email enabled. That means you can click on his name at the top left of his last post and a little menu will drop down that includes the option to email him through the board. If you do that, your email will arrive at his end with your email address. If he then responds to that email, you'll get his email address as it will then be direct and not going through the board. This feature exists so spambots can't harvest member email addresses for spam, but board members can still email one another.
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Old November 26, 2012, 12:30 PM   #30
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“For over a century, "headspace" has been what SAAMI's glossary says”

Bart B. I can not take you seriously, Sammy got started in 1926, the government was involved, they wanted, standards and coordinated technical data, and safety, they wanted to promote firearm safety. Back to over a century, from 1926 to 2012 is short of a century not “For over a century....” Back to the government, why should I take Sammy seriously if the government does not ( take them seriously)?

Take them (Sammy) seriously as in the government, our government publishes material, FM 23 65 C1, in the field manual Sammie was not consulted, Sammy did not make corrections, Sammy was not politically correct, the Government publication was not intimidated into thinking ‘they’ Sammy was the only source of information, to the government it was their gun, their soldier, their manual. It was the government’s responsibility to eliminate confusion. knowing ‘what is is’ does not trump ‘how to check it’. 120,000 BMG were installed in B17s, P47s had 8 each, Mustangs had 6 each. then there were B 25 and B26s. Millions upon millions have been manufactured with manuals, Sammie was not consulted.

Bart B. you did a search? Again, fantastic. I do not find it necessary to do a search, again, I check can measure the length of a chamber 3 different ways without a head space gage and I can modify a head space gage as in go-gage length to a field reject gage and everything in-between. Bart B., you talk about ‘it’ I do ‘it’, and, I accept that, it is OK with me.

Going to the range with new creations, 3 smiths, 120 years of experience in machine shops, 140 years of smiting, I was not there. One took a prairie dog type rifle he was going to take to the Wyoming and the Dakotas, the barrel was hand pocked by the manufacturer’s owner, when he returned from the range he selected another rifle, when expressing his disappointment in the barrel I ask him if the owner of the company sounded like LBJ, seems when selecting the barrel the owner missed the turn/twist rate by 3 inches.

Then the 50 BMG, chambered 4 different rounds, all failed to fire. Most would think there would not be enough room on top of the 50 BMG, with all that skill and experience, did not happen, they loaded up the 50 and finished their secession. The man with the 50 called me, in about 10 minutes he knew as much as I did, the best part? His rifle has a life time warranty, nothing for him to do but ship the parts and wait for them to be returned, he was surprised head space could be set twice on the same chamber, not all chambers, both of us are form first then fire, and not one time did he say “Sammy says”, and he did not say “Bench resters for years have done ‘it’ this way...”, most of that is hind sight. Again, there are those that can do it, there are those that talk about it.


http://en.wikipedia.org/wiki/File:50_bmg_12.7x99.svg this link furnishes all the information a smith/reloader/machinist needs unless he is too hard wired wired with spouting chapter and verse without understanding the meaning of what they are are quoting.

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Old November 26, 2012, 12:47 PM   #31
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Unclenick, forgive,

I said:
"JRLSH, I can make a gage, again, the 50 BMG is not difficult, the one thing I can not do is use a reloading forum, I need your email address, a phone number would help"


“the one thing I can not do is use a reloading forum” JRLSH ask a question, Bart B.’s answer, to me in my opinion, sounded like deterring the color of a shirt with a yard stick, wrong standard, again, I make gages, I said the 03 chamber length is the easiest, the 50 BMG requires more time and equipment, but there is no excuse for a reloader, smith, machinist for not knowing how it is done, not my job to convenes Bart B. there is something beyond ‘quoting’, quoting is rather shallow if the ‘how’ is left out.

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Old November 26, 2012, 03:05 PM   #32
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JRLSH, your original:
Quote:
OK guys, then I have a question concerning headspace. I am reloading for a .50BMG and recently purchased a Lyman headspace gauge. Some of my cases are spot on between the minimum and maximum on the gauge but some of my cases are up to .010 shorter than the minimum on the gauge. When loading for a caliber this large I would think this is a large problem but in doing research some say that this measurement is within acceptable ranges, but is that a measurement that will lead to case head separation upon firing in my bolt gun? I have not shot any cases yet and have only reloaded the cases that were completely spot on. AND some of the cases that are short on headspace dimentions are all spot on for OAL after trimming. Any help on this?
Are you using the distance from the BMG round's case head to the mouth as headspace?

If so, that's not what headspace gauges for 50 BMG chambers are set up to measure. They measure the distance between the bolt face and some reference on the chamber shoulder that's at a 15 degree 44 minute angle. I've not found anyplace that states what headspace should be relative to that. It's somewhere between 3.0056" and 3.2790". For a reference diameter of .6600" on the shoulder, it's about 3.1000" as I calculate from available dimensions on this drawing:



Contact Manson Reamers at:

http://www.mansonreamers.com/

then ask them what the GO and NO-GO headspace dimensions are for the 50 BMG round. They make those gauges so they have to know.
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Old November 26, 2012, 03:54 PM   #33
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Bart B., I was told typing slow was rude, or I should say telling someone no matter how slow I type when I hit the post button all of it comes out at the same speed.

Shouting is also rude, telling someone “What you do not understand is etc.., etc..” is rude.

I do not know how to tell you all of that information you posted is not necessary, in the book written by R. Lee about modern reloading is all the information that is necessary/nice to know.

You went to the trouble to furnish information regarding a link, omitted is the price of the tool they make, again, the tool is not necessary.

. “I've not found anyplace that states what headspace should be relative to that”, again, the information is not necessary, this stuff does not run me into the curb, none of this stuff lock me up, I can thumb to the back of the R. Lee’s book on modern reloading to page 703, write down one dimension then say “Mr. Lee, thank you, thank you very very much”, even that effort is not necessary. (effort: thumbing to page #703)

Many years ago in Internet time I got the impression reloadrs/smiths/ shooters thought gages came from Mars and made by Martins. I did not agree, I am not a Martin I am a people, I make gages, again, when the bolt closes the chamber gets dark for most, it should not be that way, or it does not have to be that way.

The man ask for help, I ask, ‘What is he going to do with the information you posted?”

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Old November 26, 2012, 04:35 PM   #34
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Guffey:
Quote:
The man ask for help, I ask, ‘What is he going to do with the information you posted?”
I don't know. If you must know, ask him.
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Old November 26, 2012, 05:25 PM   #35
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Tool & how to use it. http://www.brownells.com/.aspx/lid=1...nd_Maximum_COL
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Old November 27, 2012, 10:56 AM   #36
F. Guffey
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He was using a feeler gage, I use a feeler gage called a thickness gage, in his efforts he is attempting to sell tools, my interest lies in the use of the tools, again, most of the tools demonstrated are nice, but not necessary.

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Old November 27, 2012, 11:37 AM   #37
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Bart B. I do not “...must know...”. There are two specs for the 223 Remington, Sammy and Government/NATO, there are two specs for the 308 Winchester, Sammy and government/NATO. I do not wonder why that is, there is the public sector, there the government/military/NATO sector. When Sammy decides to include the 50 BMG into the public sector there will be “SAMMY SAYS” and there will be what the government/military/NATO says.

Then there is ‘always’ the question” What is the difference between 5.56 NATO and 223 Remington?

http://thefiringline.com/forums/showthread.php?t=463212

http://dutchman.rebooty.com/1895Chile.html


Gages existed before Sammy, I have had old 30/06 gages that did not agree with Sammy type gages, for me, nothing changed, I measured the length of the chamber, I measured the length of the case from the usual places, I subtracted the difference, the difference was in thousandths, this method meant nothing to no one else but for me I knew the effect the chamber would have on the case before pulling the trigger. And firing pins, my firing pins are mechanical driven, my favorite firing pins hit like a go-rillo.

I know what Sammy says, I know what the government/NATO says, they do not agree, me? nothing changes, I determine the length of the chamber from the bolt face to the shoulder of the chamber, I determine the length of the case from the head of the case to the shoulder of the case.

Old gages, some required the extractor to be removed.

F. Guffey

Last edited by F. Guffey; November 27, 2012 at 12:46 PM. Reason: change 232 to 223
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Old November 27, 2012, 05:04 PM   #38
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Quote:
I know what Sammy says,
Mr. feeler gauge, AKA f. guffey

Sammy who?

You wonder why few people bother to read your ramblings, you can't be bothered to use proper nomenclature. Yeah, I get it, you mean SAAMI. But do the new people just getting into reloading make that journey from your use of how it sounds instead of how it's actually written? Quit being cute, use the actual words!

Is it okay with you if I don't want to mess around with feeler gauges, mathematics, and seat-of-the-pants-guessing to know how my brass is being sized? I'll use my precision mic made by the fine folks at RCBS.

Drop the case in the mic, take the reading, adjust the die. So simple "a cave man could do it"!
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Old November 28, 2012, 08:26 AM   #39
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Let's not get snarky. Everyone's got a different comfort zone.
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Old November 28, 2012, 11:33 AM   #40
F. Guffey
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Unclenick, again, forgive me for my part in all of this.



Snuffy,



"Bart B., I was told typing slow was rude, or I should say telling someone no matter how slow I type when I hit the post button all of it comes out at the same speed.

Shouting is also rude, telling someone “What you do not understand is etc.., etc..” is rude.

I do not know how to tell you all of that information you posted is not necessary, in the book written by R. Lee about modern reloading is all the information that is necessary/nice to know"



And, I posted the page number. No one on this forum ask me what do I see on page #703 they do not see. In the real world I walked into my favorite gun parts store, while I was there a proud owner of one very fine rifle with a very exotic chamber came in and ask for someone to check the head space? My friend, owner of the gun parts store said "I can not check the head space on your rifle because I do not have a head space gage for your chamber" The owner of the very fine rifle thanked him and left, I did not get involved.



After the owner of the very fine rifle left I informed the owner of the gun parts store, "I can check the length of the chamber on any rifle without a head space gage in thousandths", and he ask "How?". The only participants on a reloading forum that are capable of asking "HOW?" are the ones that are asking for help. Anything 50 BMG is expensive, it was suggested he contact a company that made gages for the 50 BMG, again, that is not necessary, knowing the nature of a reloading forum I know no one will ask "WHY?".



Snuffy I do not know why that is my problem, long ago I had to decide 'I DO NOT PROVOKE', that does not mean I do not provoke people to think and help themselves. Sometimes in my effort, others are provoked, that is not my problem, I quoted from the book, the book for the 50 BMG, Bart B. was quoting Sammy, again, not my intent to provoke, I understand Bart B.s claim to fame is what comes after "Head space is etc..", there is 'What it is' and there is 'How to check it', For those that do know how to check it is the standard answer 'purchase a head space gage' then I say after purchasing a head space gage the reloader will remain in the dark about the length of the chamber from the usual places because..... and no ones ask 'WHY?' I will say I can modify a A GO-GAGE to a go to infinity gage and no one ask 'HOW?' back to not being my problem, I am not so vain that I can not ask 'HOW?' Opinionated? I can measure the length of a chamber 3 different ways, If I was opinionated I would be able to check the length of the chamber one way, as in purchase another tool like a head space gage.

And I say the length of the chamber (like the M1917) can be checked with a 280 Remington case, and no one ask "How?"


F. Guffey

Last edited by F. Guffey; November 28, 2012 at 12:44 PM. Reason: remove when
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Old November 28, 2012, 12:38 PM   #41
SEHunter
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"Yes.

You're referring to what's called "shoulder clearance." It happens with new belted cases when they're all the way into the chamber and their belt's against its shoulder in the chamber. When such a case is fired, it's shoulder gets pushed forward against the cheer shoulder and its head gets pushed back against the bolt face. That leaves a small gap between the belt and its chamber shoulder. This also happens with rimmed bottleneck cases such as the .30-30 WCF. As long as shoulder clearance is within specs, it's OK.

Lots of folks use an RCBS Mic to measure fired belted case shoulder headspace. That Mic is set up to do that for belted cases. Setting those cases' shoulder back 1 to 2 thousandths typically lets them headspace on their shoulder instead on their belt. Best accuracy happens doing this. I've been doing it for decades."


Good, thats what i plan to do for my .300 Wby. I have been neck sizing it too but i will be picking up the Redding bushing die for it as well and begin to headspace at the shoulder.

Got a bunch of neck dies i need to get rid of now
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Old November 28, 2012, 04:27 PM   #42
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SE, folks shooting belted cases back in the '50's and '60's learned that the first time a belted case is fired, it typically gets a tiny ridge about 1/32 inch in front of the belt. That's where the case body in front of the belt expanded against the chamber headspace shoulder edge. Unless that ridge gets sized back down to the rest of the body diameter, best accuracy won't be had. It causes inconsistant positioning of the back end of the case in the chamber.

We used to cut the middle section out of a standard belted case full length sizing die square up its bottom then set that in the press to size a previously full length sized case all the way to the belt. Standard dies stop about 1/16 inch or more forward of the belt. If that ridge ain't sized back down, it'll interfere with perfect case positioning at the back of the chamber. That'll make the barreled action not wiggle and whip the same for each shot.

Nowadays, a collet die's available to do that. www.larrywillis.com is a site that has them. Read the stuff about this die; good to know.
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Old November 29, 2012, 01:06 PM   #43
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ok-so as far as the condition that you spoke of goes, is this die the only one you recommend or the only one that can size that close to the belt to eliminate the ridge?
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Old November 29, 2012, 01:36 PM   #44
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Belted Magnums-Neck Sizing

If the shoulder keeps the case head against the bolt face, the area in front of the belt becomes unsupported. This can lead to what looks like a case head separation, but is not. May depend on how loose/sloppy the chamber is.
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Old November 29, 2012, 02:28 PM   #45
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SEHunter,

AFAIK that Willis die is the only off-the-shelf solution. A conventional die that would do it would have to be custom made for your chamber and brass lot. That's because some brass brands don't have the belts at exactly the same distance from their heads as others do.
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Old November 29, 2012, 03:32 PM   #46
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Back to the OP's original question -- presuming a bolt action.
Quote:
Originally Posted by OP
...goal right now is to determine head space and correctly adjust my dies. I use RCBS standard dies
Chamber Headspace is the distance forward from the bolt face to (about) midway on the shoulder portion of the chamber. It's usually "X" inches, and manufacturers are allowed ± a few thousandsths leeway.

Case Headspace* is the distance measured similarly -- from the base of the case to that same midpoint on the case shoulder. It's usually "Y" inches.

If Case 'Y' exactly equals the Chamber 'X' dimension, you have a perfect headspace match. But normally the case should be a few thousandths shorter/smaller to ensure reliable bolt closure.

~~~~~~~~~~~~~~~~~~~~
How to precisely determine/set up the sizing die?
Use EITHER the Hornady Headspace Comparator set, ...OR the RCBS precsion Mic.
It makes no difference.
~~~~~~~~~~~~~~~~~~~~

1. Fire a few rounds. Assuming the fired cases will actually go back into the rifle and the bolt close on them, carefully measure/average the resulting case headspace dimension. That is your DEFAULT case headspace number.

2. Screw the sizing die into the press and down firmly to the shellholder. Then back it off one full turn.

3. Using plenty of case lube, size one of the fired cases. Because the sides are being squeezed in, the case length (and headspace dimension) will likely grow.

4. See if the case will chamber in the rifle. If the bolt will close with no feel, measure the new (probably longer) case headspace and write it down as the new #2_DEFAULT case dimension.

5. If the case will not chamber, gradually screw the sizing die down (1/16 at a time) until the bolt will close with just the barest of feel. Measure the case headspace again as the MAX case dimension.

6. Size several other cases with this die setup to make sure the bolt will just barely close on all of them. Measure them all and write down the AVERAGE MAX.

7. Subtract 0.002" clearance from the AVERAGE MAX and set the die up (lock the lock ring down) every time to produce cases with that same dimension: (AveMAX - 0.002")
~~~~~~~~~~~~~~~~~~~~

8. Check the first several cases in each loading session (making sure you've used a good/standard amount of lube) to ensure you are producing cases with this dimension. Adjust as required since brass springback/stiffness can effect things a thousandth or two between firings.





* Yeah, I know there's supposedly no such thing. But that's too bad. It helps explain/work in the real world.

Last edited by mehavey; November 29, 2012 at 05:07 PM.
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Old November 29, 2012, 08:18 PM   #47
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Uncle nick, I think a standard full length sizing die for a belted cartridge could have its bottom cut off and squared 1/10 inch above its case belt clearance shoulder then its edge barely rounded and smoothed. Then do the same thing just below the die's body-shoulder junction. Set the die in the press so it body sizes a previously full length sized belted case all the way to the belt. If it doesn't size the body right in front of the belt back to about new case diameter, cut more off its bottom.

This is how folks in the '60's made them. I made mine from a .30-.338 FL die and it's been well used on several belted cases with similar body tapers. We called 'em "belted case body dies" back then.

On headspace gauges for barrel chambers.....

I made a set of them in .001" increments for .308 Win. chambers. First, I full length sized some fired cases such that their case headspace ranged from 1.631" to 1.636" or thereabouts. Then put each on in a Wilson case trimmer reversed and squared up their heads just enough so they measured 1.629" to 1.634" in .001" steps on my RCBS Precision Mic with my Forster 1.630" GO headspace gauge as a reference. Then I filled them with plastic steel to the case mouth. With a stripped bolt, they could be used to see what a chamber's headspace was within .001" of exact as long as the bolt handle dropped from its own weight snugging up on the case head. That brass case would shorten its headspace .001" or more if I forced the bolt closed on one so that epoxy inside made them less suseptable to shoulder setback.

Last edited by Bart B.; November 30, 2012 at 03:33 PM.
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Old November 30, 2012, 12:39 PM   #48
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Quote:
Originally Posted by SEHunter View Post
To determine the headspace for a specific gun (and the sized cases for that same gun), does my headspace measurement come from measuring the head space of a once fired case in that gun or do i measure the chamber with a tool and then use that measurement to set my die?

What guages/tools do i need to purchase to be able to measure head space? There are so many products and i get them confused as to which one i need and what they do.

My main goal right now is to determine head space and correctly adjust my dies. I use RCBS standard dies-are these good enough to perform good sizing? Please use laymans terms

Forgot to add- im FL sizing

Am looking at the Redding FL bushing die. What size bushing do i need for the 22-250?
I use a Dillon 550 with Dillon Dies, just an fyi. But the way I do it is eith a Dillon case guage. I first screw the FL sizing die down to the shellplate, then move the shellplate down and turn the die another quarter to half turn down.

Then I take a lubed case and run it through. Then i drop it in the csse guage, I make sure that it is lower than the top step, flush with the lower step is perfect. Then I check it in my rifle to see it the bolt closes either in an ar or bolt action rifle.

If everything checks out, I run that same shell through again and leave it in the die as I lock down the die to the press. I do the same thing everytime ai lock down a die setting as well.

After that, youre good to go. Get a case guage and check it there and then use the rifle as well to confirm it works and youre all set. Its very easy, yet very much a pain in the butt if you dont get it right before you begin to reload.. good luck!

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Old November 30, 2012, 03:40 PM   #49
F. Guffey
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The Belted H&H case, in the beginning, was never given much consideration in front of the belt, like a rimmed case the belt held the case to the rear and the case body filled the chamber when fired.

There was never a need for a plug type gage as go, no and beyond. Because of the lack of shop skill training among reloaders the go-gage, the no go-gage and the field reject were nice to have. Like the 303 British with a rim, the thickness of the rim off set the gap between the bolt face and the beginning of the chamber body, again, little consideration was given to the chamber in front of the rim. Back to the part where the rim held the case to the rear, same for the belt, the belt held the case to the rear when fired, when fired the case body filled the chamber, meaning the case did not get longer when the case body expanded. When fired the case gets shorter, again, there are different receiver designs.

Reloading, in the beginning reloaders had discipline, they would limit the number of times they would size and shoot belted cases, a good number was 4. A belted case that can not be sized was/is caused by full length sizing and reloaders that could not measure the distance from the bolt face the the beginning of the case body ahead of the belt. After all, if they had a gage it would be the go-gage, by now everyone should know the go-gage is going to allow the bolt to close, by how much? No one knows, except?

Case length? Measured from the bolt face to the shoulder, again, a gage is not necessary for the smith and reloaders that have a good, fundamental, basic understanding of shop skills and practices.

L. Willis comparator, not necessary, expensive, nice? but not necessary. I make comparators for my use, a comparator does not cost me above the price of a dial caliper or a height gage and or a feeler gage, the humblest of tools, I take pride in being able to use them, it is one thing to have a tool that has a single function, my feeler gages have a triple function, the feeler gage is a standard, the feeler gage is a transfer, the feeler gage is a verifying tool. It is like knowing how to hammer, knowing how to hammer does not trump ‘ knowing where to hammer’.

A magnum belted case can be modified to a chamber length gage, a magnum belted case can be modified to measure the amount of head space that exist at the belt, does not require a go, a no go or a field reject gage, just guessing but the 3 gages could cost $45.00. Magnum cases have been sized down in front of the belt with collets installed in a lathe. Again, I am the fan of cutting down on all that case travel.


SE, folks shooting belted cases back in the '50's and '60's learned that the first time a belted case is fired, it typically gets a tiny ridge about 1/32 inch in front of the belt. That's where the case body in front of the belt expanded against the chamber headspace shoulder edge. Unless that ridge gets sized back down to the rest of the body diameter, best accuracy won't be had. It causes inconsistent positioning of the back end of the case in the chamber.

1/32” is .031” +, they, the shooters of the 50s and 60s should have gotten their money back, I have belted magnum reamers, there is no radius at the belt/case body juncture, if they noticed a ridge forming on their cases they should have know .031” was greater than the total amount of head space. You will have to tell me, again, how much head space the magnum belted chamber has/had, as I said, I measure the length of the chamber or the length difference between a plug gage and the chamber. Then there is the part that is always left out when pushing L. Willis Tools, there are many shooters of belted magnums that never experience the ‘tiny 1/32 inch ridge’ ahead of the belt. And never is their a mention about the the load as in starting and maximum, never is there a mention about measuring before and again after, always left out is the part where the case head is crushed.

Then there was the Model 70 Winchester with a 300 Win Mag chamber, we had words, they started with thinking I was difficult, after that they decided I was impossible, There is no shortage of dies around here, there is no such thing as ‘a case whipping my (all of) my presses. I have a 300 Win Mag forming/trim die. cases fired in that rifle required the collet mounted in my lathe, question, do you think using a collet to restore the die to full length sizing is a good ideal? I don’t, I informed Winchester I wanted a chamber that fit my dies, or I wanted a set of Winchester dies to fit their chamber. They returned the rifle in a new box, one day I may decide to take it to the range, it was returned 4 + years ago, I have Model 70 Barrels, changing the barrel would require another bolt for 30/06 case heads. Winchester had the rifle, they could not determine the dimensions of the chamber, and they did not ask me how I determined I needed a Winchester die set for their chamber. They instructed their warranty man in the area to polish, hone, or ream the chamber, I ask, how does polishing, honing and or reaming make the chamber smaller, but for most L. Willis collet sizer die is an option.

I am the fan of cutting down on all that case traveling.

F. Guffey
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Old December 1, 2012, 10:53 AM   #50
Bart B.
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Join Date: February 15, 2009
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Some folks have been measuring new, fired and resized case headspace before and after firing since the 1950's. They've been measuring that headspace with tools before and after firing such cases for that long, too. How else would they know what the difference is to tiny dimensional standards?

They've used shims between a die's lock ring and the press since then, too. Most common shim and die this was done with is probably the .38 Special dies when set about 1/10th inch higher in the press so .357 Mag. cases could be reloaded with the same die set. I've been using a set of washers doing this for years.

Problem with shimming bottleneck rifle case dies up is when standard shell holders are used. Unless each fired and cleaned case has exactly the same amount of lube on it, how far it goes up into the die will vary several thousandths. Presses spring different amounts depending on the friction between case and die as the ram pushes fired cases up into dies.

So, shell holders with different heights allows the reloader to use one that when the die barely touches it as the press handle cams over at the top of the ram's stroke, sized case headspace has a much, much smaller spread. And the shoulder's moved to where they want it. Sometimes folks get a spread of less than 1/1000th inch. across several dozen bottleneck cases so sized to reposition their shoulder back a tiny bit.
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