Measuring Case Body Length Correctly

[RBT321]

He's not off to a good start. Lots of numbers seem to be rage these days.

I'm still a beginner and a loooong ways off from being competative, so precison wasn't my purpose with this particular question.

But I do get - and agree - with what you (and others) are saying: For normal reloading precision I don't need all these measurements. As I currently understand it, ogive, headspace and COAL should be sufficient for chasing precision. Add OAL too, if you're concerned about fitting in a mag (currently, I'm not).

I'm collecting all this extra info for a different reason - nothing to do with chasing precision. I just want to better understand what's actually happening to the brass as it is repeatedly cycled through the reloading process - call it "dynamic engineering curiosity". That's all. I was once involved in studying the harmonic resonances and force-feedback system of some solid rocket motors, and the effects of firing brass bear a few similarities - albeit at very different scales!

Once I achieve a sufficient level of understanding to satisfy my curiosity I doubt I'll have any need to continue measuring everything. But right now - because I'm only making a small number of rounds every few weeks - I have an opportunity and the time to scratch this particular itch. And because the body length is not a normal thing to be measuring, I needed to ask the gang here where the correct measurement point is for this particular measurement - and JFrank was kind enough to confirm it, so I'm happy.

 

[RBT321]

See the little asterisk and triangle symbols in the 1.4901 dimension line...they mean something.
Read the fine print.
* = DIMENSIONS ARE TO INTERSECTION OF LINES.
Triangle = REFERENCE DIMENSION

Thank you!

Yup. I should have RTFM!

 

[RBT321]

I’m thinking access to a CMM would be handy and provide the best accuracy.

Unfamiliar with CMM, could you explain?

Google just takes me to a brass catcher!

 

[BKA]

Coordinate Measuring Machine

 

[RBT321]

Coordinate Measuring Machine

Of course! I've used large ones (ours are referred to as MCMM's - Multisensor Coordinate Measuring Machines) but never on anything as small as a brass case. Serious overkill, but an interesting idea none-the-less!

 

[JEFFPPC]

I'm still a beginner and a loooong ways off from being competative, so precison wasn't my purpose with this particular question.

But I do get - and agree - with what you (and others) are saying: For normal reloading precision I don't need all these measurements. As I currently understand it, ogive, headspace and COAL should be sufficient for chasing precision. Add OAL too, if you're concerned about fitting in a mag (currently, I'm not).

I'm collecting all this extra info for a different reason - nothing to do with chasing precision. I just want to better understand what's actually happening to the brass as it is repeatedly cycled through the reloading process - call it "dynamic engineering curiosity". That's all. I was once involved in studying the harmonic resonances and force-feedback system of some solid rocket motors, and the effects of firing brass bear a few similarities - albeit at very different scales!

Once I achieve a sufficient level of understanding to satisfy my curiosity I doubt I'll have any need to continue measuring everything. But right now - because I'm only making a small number of rounds every few weeks - I have an opportunity and the time to scratch this particular itch. And because the body length is not a normal thing to be measuring, I needed to ask the gang here where the correct measurement point is for this particular measurement - and JFrank was kind enough to confirm it, so I'm happy.

I made the comment because I don't like seeing new shooters, if they really want to be competitive, to get headed down the wrong path. You become a good competitive shooter by certain basics not necessarily in this order. A good gun. I did not say a new gun. Attention to detail. A good memory helps. You often hear that's what's most important is barrels and bullets, good advice. Flags every time you shoot. Good bench manners. This is the thing that seems to trip up many..... you need to come up with a tuning method that works for you. Also figure out which of these 3 way you want to go as most end up on one of these paths. Shoot lots of targets tuning and save the good ones to look at, feel good, and show your friends. Go to matches, don't really care about where you place, just have fun. Nothing wrong with that. You want to be competitive, don't need to win every match ( no one does except in their mind) but if you do things right during the match hyou have a good chance of being most often towards the top. If you don't know your destination you seldom luck into it. Good luck. Don't try to reinvent the wheel.

 

[charlie b]

Sometimes engineers try to gather all the information they can. Has happened to me more than once, especially in testing scenarios. Lots of times the data is inconsequential. Sometimes one little tid bit will save a program.

Learning what happens to brass as it is fired is a reasonable thing. May not mean anything to anyone but him, but, it doesn't hurt.

And, yes, someday he may beat some of you at a match if he chooses that route.

 

[JFrank]

Studying brass before and after ignition, learning all you can about datum points, where to measure and how often is good information.
I learned a lot from the cruel tutelage of Mr. Guffey, he was a bit of an odd duck but by golly I know how to measure brass.