Let's kick this around

OK guys, no need to be contentious.

A bumping practice in common terms was implied by the OP talking about resizing just far enough that 0.001" of excess headspace for the cases was created (i.e., the shoulder set back 0.001" from its as-ejected size). However, even though that is now commonly called "bumping", I don't believe it is the original meaning of the term. I try to remember to call it "setting the shoulder back" as distinct from "bumping", though others disagree.

The reason for the distinction is my aging memory recalls the term "bumping" first showing up among benchrest shooters writing in Precision Shooting Magazine in the 70's or 80's who had got custom sizing dies for their rifles cut from blanks using the same reamer that chambered their rifle. A sizing die like that can move a shoulder back without making the brass narrower than the chamber, retaining a neck-sized-only case body fit with the exception of the 0.001"-0.002" excess headspace from "bumping" of the shoulder. Lot's of references are written to the contrary, though, and they call partially setting the shoulder back in an FL sizing die or in a Redding Body Die "bumping". I still think it originally meant setting the shoulder back without narrowing the body below chamber diameters by doing it in one of those custom chamber reamer-cut dies, but that is often not how the term is used today. That is unfortunate because it means the original type of "bump" resizing is being forgotten by the collective handloading community memory as a possibility to explore.

cw308 said:
There case measures .003 to .004 form bolt face to datum line…
…So with all this going on in resizing cases with .001 headspace dimension…

I have to say that is a little confusing, but I think you don't mean the case is only as long as a piece of paper is thick. I suspect you mean sized until the case leaves excess headspace in the chamber that is 0.001" to 0.003" to 0.004".

tangolima said:
I found 0.004" interference quite hard to chamber, even in a bolt gun.

Oh yes. This is not recommended practice unless you decide you want to try it to see what happens with a really tight fit. I don't think I've ever seen a newly made commercial case that was longer than a minimum chamber in .308, and even that was only in some uncommon foreign-made 7.62 cartridges. I am only saying that making the cartridge that long is within the rules of the game. The manufacturers actually know they would get complaints if they made cases that long. The reason it is within the rules is that all SAAMI cartridge length and diameter dimensions are the critical values beyond which operation of the weapon system is prevented due to an oversized cartridge. In the case of the chamber, the dimensions given are critical minimums, with criticality having the same definition but in the opposite directions; too small prevents operation.
 
Extremely interesting discussion that is an enjoyable meals for enthusiasts! But with an awful subject line that tells literally ZERO about what is being discussed.

Can we give this conversation a name?
 
Unclenick
What I meant was the case headspace dimension is so much greater with match SAAMI store bought ammo , and still very accurate . Promise I won't write any books in the future .

Chris
 
CW308 in regards to your first question my current theory is powder charge is not as important to short range ammo as correct seating depth is and finding the right powder for the bullet and barrel is. Powder charge comes into play with consistent velocity at ranges of 500 and greater. Of course the holy grail is a flat velocity node and the perfect seating depth
 
hounddawg
Never competed in shooting , I shoot with a group of friends each weekend , some have completed . I just like shooting and reloading . The ranges in my area are max. 200 yards , that's what I shoot 200 yards . I load at the low end of the scale ,as long as it shoots where I'm aiming that's all that matters. If I were shooting different distances then that's a different ball game . I don't have a chronograph , some have the ones that attach to the barrel . Two years ago one of the guys first time out with the chrono ,the kind you shoot through a triangle . First shot he mangled that thing , had to walk away , couldn't stop laughing , he was so pissed off at himself . Just gotta love the sport .

Chris
 
"contentious" causing or likely to cause an argument; controversial.- (of a person) given to arguing or provoking argument. Excellent choice of words sir. I am amused at how fast these types of posts are instantly derailed before they even leave the station. We have yet to even consider the OP's question or intent and we are off the rails. To some one like me these types of questions are at the root of my thinking when considering how to "tweak" my loading for optimal performance (not that I can shoot better than a given cartridge in a given chamber).

I am the only reloader that can admit that I might not fully understand something. Weather that be the right terminology to explain something I am new to, or the correct process to use to achieve my goal. I believe that is why we are all here talking about this stuff, well, that and we aren't out shooting.
 
I can not find a reloader that feels comfortable with moving away from the '.002" bump'.

Then, I suggest you aren't looking very hard. I'm not only "comfortable" moving away from the ".002" bump", I don't even approach it.

I began reloading in the dark ages, and pretty much stayed there. Press ram all the way up (no "Cam over") sizer die all the way down, contact with the shell holder. I size everything this way, and don't have cases fail very often. (exception .303 British and SMLE rifles...)

I've got brass I've been loading since the 70s, and its still serviceable. Yes, I have had a few case failures, but nothing like the Internet makes it out to be. Maybe its just me...

I don't load for match shooting, I don't have benchrest guns. I have some varmint rifles, and can do 3/4" groups, (which is probably the limit of my personal ability not the rifle). Most of my guns are sporting rifles, not target guns, and the advanced "tricks" used to get that last 1/4MOA shrinking of group size is irrelevant to me and my guns.

I don't measure to the "datum line" nor do I worry about bumping back the shoulder to a set amount. I take what the FL die gives me, and it works for me.
 
Two years ago one of the guys first time out with the chrono ,the kind you shoot through a triangle . First shot he mangled that thing , had to walk away , couldn't stop laughing , he was so pissed off at himself . Just gotta love the sport .

LMAO

that's what laser bore sights are for, put a piece of cardboard in front of that triangle and a laser bore sight in the chamber and you know exactly where that bullet will be going over the chrono.

I just bought a target cam and was using it at the 800 yard line the other day and another shooter asked me if I wasn't afraid I would shoot the rig. My reply was that if I or my rig was shooting that far off it was God's way of telling me I did not need a new toy. Just to be safe I made sure it was on the upwind side of the target
 
So back on track, "When sizing your brass with minimum headspace dimension is it for case life or accuracy?" "Maybe powder charge is most important?" Or is it a combination of all factors, to fit the case to the chamber + appropriate "jump" of given bullet to the lands and groves + a "flat" charge node? I only ask because I too am interested.
 
308Loader
Went down all the roads , minimum case headspace dimension for accuracy , didn't care how many reloads I got out of them. Jumping and jamming the same bullet , Sierra 168 grain HPBT MK . Found a reload that gave me tight groups , stopped tweaking and started working on my form . You could have the most accurate reload but if your form is off you'll never know it . So I guess both are just as important. Knowing how to shoot accurately should be first , knowing when you throw a shot .

I was even placing a mark on the case to insert the round on the follower in the same position every time . Way to much thinking . I still prep my brass to be as close to exact as possible , same with powder charge and seating . No changes . My only excuse now is me and barrel wear .
 
I was even placing a mark on the case to insert the round on the follower in the same position every time . Way to much thinking . I still prep my brass to be as close to exact as possible , same with powder charge and seating . No changes . My only excuse now is me and barrel wear .

Lonf before the Internet a shooter/writer/reloader purchased 500 cases from one manufacturer; who knows if the 500 cases came from the same lot; but out of the 500 cases he sorted the cases until he was left with 47 perfect cases.

And then:rolleyes: he went back and started over, he found he could get the same accuracy with rejected cases if he indexed them. No one on this forum read the article; with one exception.

F. Guffey
 
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