Don't know what to make of it yet.........

http://www.varmintal.com/a243zold.htm

A lot more data there than I need to know. I've an engineer who is a good friend. Maybe he can explain it to me.
Cheers

Too much info for me. I just want to know what time it is; I don't need to know how to build a watch.

Its interesting, but actually a long read for explaining the correlation between case stretch, bolt loading, and chamber smoothness. Well thought out and documented. The animations were neat.

Some might find it interesting or relevent, but for most shooters, it's nothing of consequence I'm afraid. Don't sweat the details. Shoot and have fun.



That pretty much sums it up.

Al was an Engineer where I work, One of the National Lab's.

He, as most Engineers I have worked with, enjoy's taking everything to the N'th degree.

He lives, and hunts Squirrels, about 35 miles West of me. I and many others enjoy his writings.

Allen

What I found very interesting was the very small variation in bolt-face pressure predicted for all but the unrelaistically smooth chambers. This is exactly what was shown in a recent experiment with pressure-sensitive film in an experiment with various cases, including some that were lubricated.

Yea John

I have seen several folks reply that they lightly lube their cases during "fireforming" so that they guarantee the case seats firmly on the boltface before the shoulder is formed, and as many have replied that is a bad idea.

I suspect lube and reduced from full loading might go hand in hand.

Allen

Hope the math is better than the english grammar, in title "effects "should be "affects".
Would wonder how changing taper on the case such as Ackleyimproved cartridges would change results.

Ah, so you know him then.

I understand the type. I was in the military, employed as a wpns technician. I worked for, or around, a gaggle of them. Naturally, they found engineering stuff fascinating...or they wouldn't be engineers. The rest of us left them alone.

We need people to work up the theory - folks that can crunch numbers - but for most of us, what engineers do holds little interest or is dryer than a popcorn fart. Then, as the old joke goes, types like me would make the theory work. Yin and Yang.

My son is a mechanical engineer, their thirst for the answer to any question seems to prevail in all engineers, i don't know if it is inherent or a result of the discipline they study.

"i don't know if it is inherent or a result of the discipline they study."

I know; it's both. No one will go into enginerring unless he's interested in both design and technical things. The learning, and eventual work, absolurely demands abstract analytical thinking and focused attention to details.

Minute details of technical things ARE important, especially when pushing the strength limits of materials. The Morten-Thycol rocket motor engineers warned NASA bureaurcrats that the engine O ring seals might fail because of the slighly cold weather but PR and political concerns over rode engineering and, sure enough, the Apollo craft blew up pretty quickly after the fuse was lit.

Here is a great 66 second video on engineers which explains it well...



John

High level what his study says -

The more polished a chamber is the more force gets transferred to the bold face.

Also the less friction the more likely the brass will flow and thin the case wall by the head.