Survival: Advanced Marksmanship, Understanding Twist Rates and ballistics.

reply to post by jibeho

Being successful in the art of survival means having a firm understanding of skills and equipment...

knowing and understanding the inner workings of your firearm is every bit as important knowing how to build a fire or sharpen an axe... maybe more so as a firearm is one tool that is expected to protect and feed yourself and your family... not learning all you can about that tool just sets yourself up to fail in your attempt to use said tool when it's needed most...

reply to post by DaddyBare


"The Golden rule in ballistics is
The heavier a bullet is… the faster it must spin to stabilize in flight and the higher the velocity, the slower twist is required."

Close, but it's actually the longer the bearing surface on the priojectile to bore, the faster twist needed to stabilise.

What you said is correct in most cases, as a heavier projectile will usually have a longer bearing surface than a lighter projectile of similar design.

The design of the ojive of the given projectile has an effect of the bearing surface length.

Do a google for tangent vs secant ojives & boat tail vs flat base projectiles.
For example, a boat tail and a flat base, will vary in regards to twist rate, even if the projectile weight and other variables are equal.

The greenhill formula has been used for ages. but it's been superceeded by others, namely the Miller Formula..
JBM is software that calculates trajectories and ballistics for small arms projectiles and can use this formula.

www.jbmballistics.com...

Originally posted by afaik
reply to post by DaddyBare

 

"The Golden rule in ballistics is
The heavier a bullet is… the faster it must spin to stabilize in flight and the higher the velocity, the slower twist is required."

Close, but it's actually the longer the bearing surface on the priojectile to bore, the faster twist needed to stabilise.

What you said is correct in most cases, as a heavier projectile will usually have a longer bearing surface than a lighter projectile of similar design.

The design of the ojive of the given projectile has an effect of the bearing surface length.

Do a google for tangent vs secant ojives & boat tail vs flat base projectiles.
For example, a boat tail and a flat base, will vary in regards to twist rate, even if the projectile weight and other variables are equal.

The greenhill formula has been used for ages. but it's been superceeded by others, namely the Miller Formula..
JBM is software that calculates trajectories and ballistics for small arms projectiles and can use this formula.

www.jbmballistics.com...

you are of course very right and I did debate whether or not to go into details such a sectional densities and ballistic coefficients as well as going into variables and inner workings of lands and groves... but I worried that this would turn into a tech white paper.... when I was going for a simplified layman's guide...

maybe I missed the mark in trying to keep things to simple????

reply to post by DaddyBare


All good,
Just clarifying for the readers,

I don't get to do it often

All I do is pull the trigger until it goes "click".

Originally posted by DaddyBare
reply to post by jibeho

 

Being successful in the art of survival means having a firm understanding of skills and equipment...

knowing and understanding the inner workings of your firearm is every bit as important knowing how to build a fire or sharpen an axe... maybe more so as a firearm is one tool that is expected to protect and feed yourself and your family... not learning all you can about that tool just sets yourself up to fail in your attempt to use said tool when it's needed most...

edit on 19-7-2011 by DaddyBare because: (no reason given)

I wasn't cracking on you. It just seems a little data rich for a survival topic. Fortunately for me, I am well trained with the firearms that I own and effective in the most common weapon platforms. In a survival situation I will make do with whatever is available to me whether its my weapon or not.

Therefore, IMO the mastery of the fundamentals of weapon handling, function and the proper use of iron sights alone is essential to surviving. Twist rates and ballistics are not going to save my life but may help me win at Camp Perry and the effective use of an iron sight and knowing the basic principles of simple windage and elevation will certainly put a meal on my table or allow me to defend my home. Keep it simple in survival..

By failing to prepare, you are preparing to fail - Benjamin Franklin (that used to be in my signature line) and has remained on my bumper for the past 4 years and has guided me for years. The foundation of my survival knowledge was learned on the water when simple, lightweight and effective will certainly save your life. I carried the same principles into the arena of light weight backpacking and adventure/bicycle touring.

Clearly we have different views on this specific topic however, I still enjoyed this thread and enjoy many of your other threads.

reply to post by jibeho


My bumper sticker reads
"Don't tell my wife I'm a contractor, she thinks I play piano at a whorehouse"

you know I always respect all you input and views... it's more along the lines where I don't feel there is such thing as too much information... even if they only understand one tenth of what I write... that might just be enough to make a difference... besides I never did like it when people talk down to me so I'm not going to do it to others...

anyway today I have fishing on my mind... no not survival fishing, but a fast boat and my wife in a bikini zipping across the lake... kind of fishing

reply to post by DaddyBare


Cheers and have fun. Stay cool because I suspect you are still getting cooked in Kansas.

reply to post by jibeho


Want to see just how bad it is here in Kansas???
go check this latest thread out
www.abovetopsecret.com...

reply to post by DaddyBare


Good info. Can you link to the first part thread you made on this topic? Thanks.
BTW, starred and flagged.

Wow thats alot of information,very interesting though,thanks OP.

Ever though im not a firearms buff or own a firearm, its still good to understand how things like that work,i understood it farely easily,just didnt know the maths,formulas and such that relate to it properly.

Cheers

Originally posted by ElectricUniverse
reply to post by DaddyBare

 

Good info. Can you link to the first part thread you made on this topic? Thanks.
BTW, starred and flagged.

Over the years I've written dozens and dozens of threads on the subject
but here is the one mentioned
Basic Marksmanship (Proper Sight Alignment),
www.abovetopsecret.com...

then you might want to peek at this one too
What Really Happens In A Gunfight
www.abovetopsecret.com...