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Headspace Comparitor & Bumping

SAAMI chamber drawings show the distance from the rear of the chamber to the datum for headspace. They also list the diameter of the datum. That line exists in every chamber but it is an imaginary line. It can be measured and identified and its proper placement confirmed even though it is an imaginary line.
The dimension on fired brass to a point on the shoulder that is the same diameter as the datum will be closer to the cartridge base than the headspace dimension for the chamber. After firing the case rebounds back toward it's original size.
In the real world none of this matters unless you are reaming a chamber. The gun you have has a chamber and you want to try to fill it as completely as possible while making sure your loads chamber easily. Your chamber might be on the long side or it might be a SAAMI minimum chamber. The reloader simply adjusts his brass to fit the chamber. If the reloader over sizes his cases making them smaller when compared to his chamber the result can be "J" splits in the body or case head separation and shorter case life.
 
That is where reloaders started, they thought there was a line on the shoulder, there was no line and there was no arrow pointing to the line identifying the line as a datum. Some reloaders continue to call the line 'the datum line'. There is no line, there is a circle/hole, most of my datums measure .375" and .400" in diameter but when using a comparator the diameter is not important.

It is not easy to find a place on the shoulder with a line.

F. Guffey

I'm thinking Cliff Clavin might be able to make sense of this^:
 
It never fails... a good thread gets going, good information gets exchanged, people can disagree, and make their case with logic, and nobody is getting ugly...

... and bingo, Ol' Frank Guffey shows up and turns the thread into shit, with his endless monologues about semantics and what the real meaning of "headspace" "is". Frank Guffey went to the Bill Clinton School of Grammar, and he loves to do this - he has no friends and this is the only attention he gets.

It never fails, and he killed this one.

Thanks Frank.
 
It never fails... a good thread gets going, good information gets exchanged, people can disagree, and make their case with logic, and nobody is getting ugly...

... and bingo, Ol' Frank Guffey shows up and turns the thread into shit, with his endless monologues about semantics and what the real meaning of "headspace" "is". Frank Guffey went to the Bill Clinton School of Grammar, and he loves to do this - he has no friends and this is the only attention he gets.

It never fails, and he killed this one.

Thanks Frank.
That's why he's on so many "Ignore" lists. He's not worth the aggravation.

Your mileage, of course, may vary.
 
However he is NOT on my ignore list. I'm retired and no longer do the crossword puzzles on my way to work. Reading or trying to decipher the true intent of his posts is an honest to goodness challenge. I have not been very successful at all.
If Bletchley Park was still up and running.......
 
SAAMI chamber drawings show the distance from the rear of the chamber to the datum for headspace. They also list the diameter of the datum. That line exists in every chamber but it is an imaginary line. It can be measured and identified and its proper placement confirmed even though it is an imaginary line.

It is not an imaginary line; from the very beginning of reloading forms on the Internet reloaders have had no clue, in the beginning they thought there was a line and they explained the line with an arrow and they said "that is how they do it". DO WHAT!? Reloaders have never been able to see the datum from three different sides. I can see the datum from the side, top and front, the datum is three dimentional, the datum is not a line, it is a round hole. The datum for the 30/06 is 3/8" in diameter or .375" and if the round hole has a bevel/radius is is a hole that is nice to have but not accurate. I am the fan of datums that are not case friendly, I want an edge on my datums that will imprint on the case. Hornady uses a radius and everyone makes excuses for it.

F. Guffey
 
It is not easy to find a place on the shoulder with a line.

Of course it is hard to find a line on the shoulder of the cartridge or the chamber. However, it is not hard to find the line on a SAAMI drawing. On the .308 Win for example it is the 0.400" diameter point.

I still have absolutely no idea what your point is...
 
I agree the term "headspace" is confusing. I appreciate that it is "formally" described as the distance from the bolt face or datum line to the shoulder. However, the term itself implies you are measuring a gap or space. And at the end of the day that gap or space is the critical measure for the reloader. Basically there is a useage for headspace for the gunsmith or owner setting up a barrel on the action, and another use of the term headSPACE, for the reloader.

As for the types of press used, cam over or solid stop, I don't see the relevance. I own one of each. They both can do the same job of bumping a shoulder. The rubber hits the road, so to speak when the sizing die hits the shell holder. It is the shell holder/die combination that determines what you can do with the case, not the press.

I think one of the issues in reloading that is not fully understood is that the distance from the base level in the shell holder to the face of the shell holder is critical. I think there is a supposed standard dimension of 0.125". However two I have (Lyman, and no name, Lee?) measure closer to 0.123". They have 0.002 more bump potential built in than a so called standard. Then there is the die issue. Is it made for a 0.125 or a 0.123" or what? RCBS according to their product description claim they size the body of a case to minimum SAAMI, but the shoulder to maximum SAAMI. If you combine a RCBS die built like that, with a fat shell holder, you may not be be able to bump to even maximum SAAMI.

Bottom line is that after the gun is bought or built, a reloader needs a method to measure the SPACE that a sized cartridge has at the shoulder, regardless of what you want to call it. And you need a shell holder that is skinny enough to get the shoulder bump done.

And at the canadiangunnutz.com you told the OP who was having problems bumping his shoulder back far enough to buy Redding competition shell holders. So with all your worldly expertise how will the OP push the case further into the die using competition shell holders.

Headspace is also the distance between your ears and how well you use that space.

Sorry to this forum but Ron AKA is our Canadian version of F. Guffey!
 
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And at the canadiangunnutz.com you told the OP who was having problems bumping his shoulder back far enough to buy Redding competition shell holders. So with all your worldly expertise how will the OP push the case further into the die using competition shell holders.

Headspace is also the distance between your ears and how well you use that space.

Sorry to this forum but Ron AKA is our Canadian version of F. Guffey!

You don't seem to have any more point to your post than Guffey does.
 
You don't seem to have any more point to your post than Guffey does.

And your the same person who said at the canadiangunnutz.com there was no difference in primer thickness or hardness.

pos·er
ˈpōzər/
noun
noun: poser; plural noun: posers
a person who acts in an affected manner in order to impress others.
synonyms: exhibitionist, poseur, posturer, fake;
informalshow-off
"he's such a poser"
 
On my new 6BR, I decided to use a neck sizing & bump die. I finally got to use My Honrnady headspace comparator and was a little surprised to find some differences in cases that I had fired. Most measured 3.130 with some at 3.129 and few more at 3.135. Is that a normal spread?
Would bumping back to 3.120 make sense or is that way too much?

Appreciate any help.
Regis

When FL sizing once fired Lake City cases I buy in bulk I pause for 4 seconds at the top of the ram stroke. This greatly reduces brass spring back and the cases are more uniform. My Forster bushing bump die produces more shoulder location variations and neck runout than my Forster FL die. I think this is caused because the case body is not fully supported like it would be in a FL die.

At the Whidden custom die website they tell you they get the most concentric ammunition with non-bushing full length dies. And they sell expander kits with five expanders in .001 increments.
 
It never fails... a good thread gets going, good information gets exchanged, people can disagree, and make their case with logic, and nobody is getting ugly...

... and bingo, Ol' Frank Guffey shows up and turns the thread into shit, with his endless monologues about semantics and what the real meaning of "headspace" "is". Frank Guffey went to the Bill Clinton School of Grammar, and he loves to do this - he has no friends and this is the only attention he gets.

It never fails, and he killed this one.

Thanks Frank.
Well heck don't let guys like Guffey and RonAKA ruin things for you here. That is just giving them control. I dont put them on ignore, I just don't read their posts. The only mystery to me is why anybody bothers to read their posts and especially why does anyone waste their time replying to them.
 
Well heck don't let guys like Guffey and RonAKA ruin things for you here. That is just giving them control. I dont put them on ignore, I just don't read their posts. The only mystery to me is why anybody bothers to read their posts and especially why does anyone waste their time replying to them.
Simple, read the posts, the OP was weighing in on some nonsensible replies that could only serve to confuse the subject at hand....thus why we are at 4 pages...."THEN THERE IS" :) the entertainment value for others....a win-win in my book.
 
And then there is R. Lee; he wrote a book about modern reloading. R. Lee is the only company that furnished information for the case datum on case drawings. He includes the diameter of the hole; again, when using a comparator it is not necessary to use the correct diameter datum. Again, I make datums, I collect datums and I have purchased datums. I was at a gun show when I noticed a box on a dealers table; I said "DATUMS!". Standing next to me were three reloaders; one ask me, "What does a datum look like?", another ask, "WHERE?" and the dealer said he did not have no datums.

F. Guffey
The name,richard Lee ,does not belong on a accuracy site!
 
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Over the years, I have enjoyed reading this forum. I have also learned a lot of valuable information from many legitimate experts on here that are willing to be helpful and I appreciate that.
....but for a person looking for info/help on here, please be aware that there are some "alternate experts" that frequent this forum, where the word expert can be defined as follows:

ex - means used to be
spurt - is a drip under pressure
 
I still have absolutely no idea what your point is...

And that is OK, for years the total amount of understanding among reloaders was 'THERE WAS A LINE' they used an arrow to locate it but had no ideal how to use it. It took me years to convince them there was no line, for those with a few shop skills finally understood the concept of a circle/round hole to find a locations on a taper. Not long after that reloaders were going to hardware stores to purchases bushings etc. and they always started out with "This is all I do, I purchase etc.."

After that they could not get anything to agree, it had to be pointed out the bushing had a radius on the inside edge, then it had to be explained to them the datum does not have a radius and the hole is exact. A hole/datum that is not exact and the hole with the radius turns all efforts into a comparator.

F. Guffey
 
And that is OK, for years the total amount of understanding among reloaders was 'THERE WAS A LINE' they used an arrow to locate it but had no ideal how to use it. It took me years to convince them there was no line, for those with a few shop skills finally understood the concept of a circle/round hole to find a locations on a taper. Not long after that reloaders were going to hardware stores to purchases bushings etc. and they always started out with "This is all I do, I purchase etc.."

After that they could not get anything to agree, it had to be pointed out the bushing had a radius on the inside edge, then it had to be explained to them the datum does not have a radius and the hole is exact. A hole/datum that is not exact and the hole with the radius turns all efforts into a comparator.

F. Guffey

Thank you. Now I understand.
 

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