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Bullet penetration.
woodchuckjohn
Member Posts: 207 ✭✭✭
I found a great site on line by accident, where there was a comparison of 7.65x39
ak 47and 223 AR. The test was bullet penetration. The 223 punched a hole in a cement block while a 7.65 shattered it. Two 4x4's side by side were penetrated clear thru by the 7.65 while the 223 just buried itself in the wood. What I don't understand is why a 30 caliber bullet traveling at 2300 fps would penetrate better than a 22 caliber ball ammo traveling at 3000 fps.
ak 47and 223 AR. The test was bullet penetration. The 223 punched a hole in a cement block while a 7.65 shattered it. Two 4x4's side by side were penetrated clear thru by the 7.65 while the 223 just buried itself in the wood. What I don't understand is why a 30 caliber bullet traveling at 2300 fps would penetrate better than a 22 caliber ball ammo traveling at 3000 fps.
Comments
Try dropping a pingpong ball on your foot. What would the result be if it were a bowling ball instead?
Simplest understanding is the momentum of more weight in the .308 diameter bullet.
Now, take a .224 bullet and a .308 bullet of same design/weight/ pushed to same fps, the .224 might penetrate more? I do not know? Many factors involved.
45er
EDIT-- OOPS, A-cowboy beat me to it.
I can tell you that a hand loaded 30-06 armor piercing bullet will not shoot threw the web of railroad track but a 500 grain hard cast lead bullet from a 45-70 will.
added The hand loaded 30-06 was a full case of H4831 with a black tipped AP bullet pulled from a dud round. It raised a welt on the off side of the web. The rifle was a Savage 110E. The hole in the wed was about 3/4 of an inch deep.
That rifle survived 2 full case rounds of H4895 pushing a swaged to 30 cal. from a 6.5mm 140 gr hard cast with a 270 gas check, made an interesting looking boat tail. I hit the rail down on the foot and it ripped a trench nearly 2 inches long up the foot. Maybe 3/4 of an inch of the trench was almost a tunnel. My buddy loaded the rounds from the wrong sack of powder. That rifle earned my respect that day. 308 ball would leave a copper spot. The 222 would make a small dent. I know where that section of rail is/was I'll try and get by to get a pic. This was shot in the early 70's.
The 45-70 was mine that was built on a Mexican small ring Mauser. IIRC the load was way more IMR 4198 than you find in the books. The bullet was cast with some lead that was contaminated with Kirksite?, very hard to cut the spru. I had a 90#/ft section of Nippon rail I found after walking hundreds of miles of track in the early 80's. It was this one I put a hole in the mid 90's. When I was dying , that section of rail got thrown in the scrap along with my last year of production 283 with fuelie heads.
Earlier with my P.O. Ackley rifle in a 350 Rem Mag blown out to 45 cal. I couldn't find the bullets in a dirt bank. I cut some willow branches and shoved them in the holes. The 405 gr cast bullets were driving in almost 5 feet in the undisturbed earth after traveling 600 yards from the last lane at the range. After about 15 rounds the recoil lug was yank through the factory laminated 600 Rem stock. I put 11 pins in and lots of micro bed in the stock. 1" nylon webbing made a cradle for the rifle with a tire and wheel off a Volkswagens dasher. With a lanyard I fired of 10 rounds, it would slide the wheel back and stand it up on the tire. I did about 10 more rounds offhand, and then shot the rest from the tire. Later HS Precision made me a fiberglass stock. The rifle loaded plus the sling and full peeps is now 5.25 pounds, most folks will only shoot it once.
I took that PO rifle to a unlimited Black powder iron Chicken shoot. I designed and built a breach seater for 540 gr bullets and loaded the case full with Dupont 4Fg held in with a card wad. The first chicken I hit went flying down range, when they found it with a hole I was disqualified and not allowed to continue with that rifle. A old felt sorry for me so he let me finish using a trapdoor in 50-70. It was real treat watching to rams slowly fall over at 200m shooting an unknown rifle offhand. I never went back, the chicken was 3/8 T1 and they told me no one had ever punched a hole in one.
Sectional Density (the mass per cross sectional area), the construction of the bullet (armor piercing vs. full metal jacket), the velocity the bullet arrives at the target with and the rotational rate are all factors in terminal ballistics.
I can tell you that a hand loaded 30-06 armor piercing bullet will not shoot threw the web of railroad track but a 500 grain hard cast lead bullet from a 45-70 will.
I got to call you on this one Charlie. Want to see photos of the RR track. I have shot a bunch of high velocity bullets at steel plates over the years. They either punch through or leave a big divot, in the steel. Lead bullets on the other hand will flatten out, maybe put a descernible bend in the plate. But not pentetrate to the extent of the high velocity jacketed bullets.
I think you are referring to a comparison between the 7.62x39 Russian and 5.56 Nato.
Answer based on Newton's physical laws.
Bullet (kinetic - an object in motion) Energy = 0.5*M*V^2
M = Mass of projectile (mass is not the same as weight)
V^2 = Velocity of projectile squared
Best,
Heavyiron
Wasn't Newton's law based on the "vacuum tube theory"? Not trying to be a smart *, but hard to relate the E=MC squared to todays ballistics. I think[?]
Newtonian/Classical Physics deals with normally observed interactions where Energy is 1/2 M x VxV. Only when things go really fast,ie approaching light speed does the energy approach M x V x V.
The vacuum part is for dealing with "wind resistance", which was necessary to show forces were equal.
The most important factor at play is actually MOMENTUM (not k.e), but things like bullet shape, bullet construction, and target density also play roles.
On paper a .223 yields about 1300 ft-lbs of kinetic energy at the muzzle. The 7.62x39 yields more, about 1500 ft-lbs.
Even more important, the .223 bullet will weigh either 55 or 62 grains; the 7.62x39 weighs 123 grains, roughly double.
Same energy but bigger and heavier bullet means more momentum for the 7.62x39, and more penetration.
Note that this does NOT necessarily mean that the 7.62x39 is the more effective cartridge. . .the super high velocity of the .223 provides a significant hydrostatic shock effect that makes the round more effective as a manstopper than the pure numbers suggest. Shooting bricks is different question than shooting people!
Concrete blocks and 4x4s are not the best or adequate testing material for bullet penetration testing since the properties of either material are unknown and are certainly not uniform. Concrete block is rather brittle and 4x4s can be stringy and twisted due to the wood grain or there can be knots. Is it a better penetration test to punch a hole through the concrete block or shatter it?
However, it does make an interesting demonstration to see things break apart after impact.
Best,
Heavyiron