BD1 wrote:I'm not an expert either, and I don't play one on TV. However, I've had some experience with varying head space and below is the way that I've come to understand the issue.
All firearms have 'head space". It would appear that your .450B has .006 head space. Even rimmed cartridges have head space, in that case it is the difference between the distance from the face of the bolt or recoil shield to the face of the cylinder or chamber rim groove, minus the thickness of the rim. It's a small number, but it's there. .22 competitors spend hours in the evenings sorting those little cartridges by rim thickness to try and gain an edge in consistency. Without any head space your firearm would tie up after the first few shots from powder residue, or from the first tiny piece of grit. The head space allows clearance for those sorts of contaminants to get shoved out of the way.
Head space in an typical bottle neck rimless cartridge like the .308 or .223 is the difference between the measurement from the case head to the datum line on the shoulder of the case, and the measurement from the bolt face to the datum line on the chamber of the firearm with the bolt closed. Excess head space can be a real problem in high pressure bottle neck cartridges as the increasing length difference between the chamber and sizing dies causes the case to stretch out on firing. Eventually this leads to a case head separation which, when you're lucky, only leaves the gun tied up with the partial case stuck in the chamber. When you're unlucky the escape of high pressure gas into the action causes other, more serious, mischief. This is a constant issue with bottle neck cartridges as that dimension of the case is adjustable to a certain extent depending on how you set up your sizing die in the press, and the pressures involved are often high enough to cause the brass to "flow", and to compress and stretch the locking lugs over time. This can be a real issue when loading for older mausers or smellys.
IMHO, In the rimless case of the .450B the result of excess head space is more likely to be either a misfire due to the firing pin not reaching far enough to ignite the primer, or a failure to extract if the short case manages to stay in front of the extractor all the way through the cycle. The action of the sizing die is not really adjustable in regard to head space, and there's no way to "trim it longer" that I know of. if you want to see an endless argument over whether a cartridge of this design is actually held against the bolt until fired, or not, just go to any major gun forum and search ".45 acp headspace on the extractor"
Be prepared to read for a month or two.
Perhaps we should each take one case and trim it down until it malfunctions, and then compare our results. The average would give us a "too short" dimension based on as many different guns as we can get to participate.
BD
Ding, Ding, Ding...BD wins the little rubber duck again!!!!
Holy Cow! I at first wanted to stay out of this endless pursuit, but BD makes a comment that may eventually prevail. Quote.."if you want to see an endless argument over whether a cartridge of this design is actually held against the bolt until fired, or not, just go to any major gun forum and search ".45 acp headspace on the extractor"..
How to start and then not be drawn into this continuing Saga. Hoot, first of all, in some things you are just too anal, in other things, you are a methodical mad-scientist, doing the good work.
There are +- measurements standards in all of the machining world. The 45acp has a cartridge short length std of .010" and the long end of the chamber is another .010", for a total slop of .020". So, as long as the firing pin can get to the primer...
To answer you questions, somewhat (I hope I just don't open a kettle of fish). About your diagrams, it's a combination of spaces in B & C.
Wiping a dead horse is not fun to me, and we have the most accurate rifle, ever mad (according to the Outdoor Channel). What are we going to accomplish with all this Hyperbole? If my Dragster beats your Dragster by .00001 thou of a second, well, I guess I win.
My advice is to shoot the weapon and if the cases get to short after 20-50 reloads, get some new brass. A better thought, to get to that many reloads, is to anneal them often.
I'm not trying to discourage you at all, but sometimes we need to pick our fights.
BD, again claims not to be a Expert on TV, but we know better, after all he really is Steven Seagal, in real life . Myself, I was at one time a pert, having reformed, I am now an ex-pert..wink.