A Project I Have To See For Myself ..

[HollandNut]

This is the first I have heard of this phenomenon ..

A PH friend was looking thru Art Alphin's "Any Shot You Want" or whatever it's called ..

Seems there is a little side note where they compare the penetration of the 460 A Deuce Short and 460 Webby .. Identical J Bullets .. The Webby has a slight velocity edge ..

Says the A Square consistenetly out penetrates the Webby , doesnt say by how much , but says the only difference is the following :

10" twist A Square out penetrates a 16" twist Webby ..

I have always preferred a faster twist , cause it stabilizes heavier bullets better , but in a lifetime of actual work in ballistics and jus general deep thinking about things , this is the first I have ever had this idea presented ..

Will definetly be some 458 tests to follow ..

[leftiye]

Higher velocity, more expansion (even solids expand sometimes), less penetration? Otherwise it should all go to the WBY. Unless RPMs were to affect expansion, then that should make the A-Sq penetrate even less.

[Nueces]

Mebbe the faster twist bullet stays point-on a bit longer in the target medium...

Mark

[oneokie]

Mebbe the faster twist bullet stays point-on a bit longer in the target medium...

Mark


+1 to what Nueces said

[HollandNut]

Some phenemena like that is the only thing I can think of that may cause it ..

My thought is it must not be to much more penetration , cause if it was , seems you'd hear about it a lot ..

Me , I'm skeptical abt this , I like AA's calibers , his ammo stinks , and his rifles are not designed very well , tho' I do like them ( the rifles ) ..

[Linstrum]

Not a new phenomenon, I read about a similar thing years ago. I think Neuces is onto it, somewhere back around 45 years ago when I was first studying ballistics I read about military penetration tests of 150-grain ball ammunition done with the .30-06 and it was something to the effect that the penetration in soft pine was greater at 200 yards than at 50 yards. Now this sounds bassackwards because the remaining energy is obviously less at 200 yards than 50, so how on earth could less energy yield more penetration? The answer was that at 50 yards the bullets had not stabilized with their rotation at the dead center of the geometrical axis of the bullet yet, I have seen high speed movies of bullets exiting a rifle muzzle and it is amazing just how darned crooked they come out, wobbling about quite a bit! But by 200 yards the bullets were rotating with their points at the center of rotation due to both the gyroscopic effect of rotation along with the aerodynamic shape of the bullet forcing the gyrations to stop and the bullets to rotate on their true center of mass. Now, with the bullets traveling point dead-on they presented a minimum of frontal contact with the target medium with resulting less displacement of material inside the target and hence traveling further into the target medium before tumbling. In other words, at 50 yards the bullets tumbled almost immediately on contact with the soft pine because they smacked into it partly sideways but if they had first stabilized rotation they went in point first and had a chance to go deep before tumbling.

Now with that said, the 1 turn in 10 bullets have much greater gyroscopic stability. Using the physics formula E= 1/2 MV^2 where E is rotational energy and M is bullet mass and V is ROTATIONAL velocity (rpm or angular velocity, NOT muzzle velocity!) we have 1/10 squared divided by 1/16 squared to find how many times greater the stabilizing energy values of the one turn in 10 inches and one turn in 16 inches bullets. In cranking those numbers through my calculator I get a whopping 2.56 times great stabilizing energy for the 1 turn in 10 inch rotation bullet compared to the 1 turn in 16 bullet. To me that shows that the penetration is due to stabilty lasting longer as the bullet penetrates.

Now, what would upset the apple cart is if the bullet material used for the penetration tests were greatly more frangible, to the point where the rotational energy would become a hindrance to penetration instead of a benefit. Since I just discovered this factor I will now name it the "Linstrum Point for Boolits", which is the point where the boolit alloy stength is no longer enough for the rotational forces to provide maximum penetration for a given target medium, such as a clay bank or a stack of wet phone books (let's not get TOO technical here!) Anyway it is something to ponder, have fun!

[Linstrum]

More penetration.

As an aside, a few years back I read an account of an incident that happened during the Vietnam War that took place not too long after the M16 replaced the M14. One of the squads that happened to still use a selective fire M14 was out on patrol when they became pinned down by a bunch of VC hiding behind big trees. The VC were shooting French MAS 36 or Mosin rifles and were penetrating all the way through the trees giving cover to our guys. The VC were pretty safe from return fire from M16s and they new it, but that day they lost since our ground pounder with the M14 took them out one by one behind their trees using 7.62x51 with 147 grain ball ammo. The lieutenant saw that their one and only powerful rifle was their only hope of getting out of the ambush alive so he directed its fire one shot at a time through all the big trees he could see and one at a time they flushed the VC out or took them out where they stood behind the trees until enough casualties had been taken to route them into breaking cover and running, then finishing the job with the M16s.

[Bret4207]

Is it also possible there's a bit of advertising hype here? I have that book and found it to be worth nothing like the money I paid for it. Just my opinion. The twist/expansion idea sounds right.

[44man]

I have always hated the little toy they give our guys and it has cost a lot of lives over time because of the lack of penetration.
Even the 30-06 tracer bullet will penetrate 2 feet of green oak before it stops. The nose will be sticking out.
Ask me what I would want if the BG's were hiding behind cover? I don't want no stinkin .22! Give me a .50 bmg.

[exblaster]

I have always hated the little toy they give our guys and it has cost a lot of lives over time because of the lack of penetration.
Even the 30-06 tracer bullet will penetrate 2 feet of green oak before it stops. The nose will be sticking out.
Ask me what I would want if the BG's were hiding behind cover? I don't want no stinkin .22! Give me a .50 bmg.

44man did you ever try to hump an M2 on patrol?


Exblaster

[10-x]

[SIZE="3"]This could open the can of worms about the .223 vs .30 ..........ammo carried vs MARKSMANSHIP!!!!!!!
I'll take a "Hog"(M-60)......it worked in Vietnam[:Fire:/SIZE]