- December 2, 2016 at 9:49 pm #31772HarterParticipant
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Stay with the needle jet/breaker points guy , there is a lengthy thought train ride .
Lots of racing designs have come and gone . The piston engine has a drive problem with going super sonic .
Because of the negative air pressure in front of the propeller causes acceleration of air and makes thrust by the means of sucking rather than push . The air flow is traveling faster than the than the aircraft , if it doesn’t thrust is lost . By my best math this happens right about 600 knots (1.15 road miles per knot) . With a counter rotating second propeller the second prop draws from compressed air mass . With a perfect model and sufficient horse power the pistol/prop driven aircraft should be able to dive through 650 knots where the propeller is past the trans sonic cavitations . The catch is that the aircraft has to accelerate 75 plus knots in that dive . The cavitation however creates a situation where the propeller may as well be a sheet of plywood ………. It can be done on paper but it doesn’t work in application .
We know about the buffeting in transonic going both ways in aircraft and how that effects bullets .
What if bullets experience a similar event ……. Do bullets experience a similar event ?
The air inside the barrel in front of the bullet has to go somewhere . As such the that air mass has to be moved at least as fast the bullet . If the bullet is subsonic there won’t be a transition area of barrel air with a shock wave in the middle of it . With a longer barrel there is more displaced air and a thicker shock wave area forms . Does that area have enough mass/density to damage a cast bullet ?
What happens physically to the bullet when it goes supersonic inside the barrel ?
What if the bullet doesn’t know it’s supersonic because of the pressurized air in front of it until it “impacts” the shockwave ?
If not the bullet then would be subjected to supersonic shock twice before it was a foot outside the barrel . As I write that it occurs to me that it would get it twice inside the barrel . If the exterior density of the air and the shockwave is even 25% higher than a normal day it could be enough to physically alter the bullet .
I wouldn’t have any idea how to prove this out without making a controlled environment case for the rifle where air density and moisture could be controlled .
This damage at the or just beyond the muzzle goes along with Tims “washcloth” twist / accordion theory .
- December 3, 2016 at 6:15 am #31784ScharfschuetzeParticipant
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Cast bullets are prone to slumping from the inertia created in acceleration if the design is faulty, the alloy is too soft or the velocity is too high for the design.. That destroys accuracy. Before you run into your described problem, the bullets will suffer other more catastrophic damage from their lack of strength against the rifling, failure of the lube and inertia.
I’ve recovered numerous cast bullets from snow that showed no damage from their flight through the sound barrier. Cast a well designed bullet of a proper alloy with lots of support from the bore, size it properly and fire away without worry.
Larry pushes his cast bullets in purposely designed barrels and cartridges to jacketed bullet velocity without a hint of degradation of accuracy all the way to 300 yards. It’s a hoot to see a cast bullet act like a jacketed bullet at such a range with almost Sierra Match King accuracy and not a hint of leading.
- December 3, 2016 at 7:06 pm #31798popperParticipant
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What happens physically to the bullet when it goes supersonic inside the barrel ? Army has proven this to be the case. We ‘see’ anothe shock wave when the boollit leaves the muzzle, per Tim’s pics. So, yes, the nose can get slumped by firing inertia and compression wave of air. Some OP have alluded to gravity playing a part in nose slump but I don’t go along with that. IMHO, gravity and an under 100% fill can have an effect on powder burn thus base damage..
- December 4, 2016 at 6:51 pm #31843Larry GibsonParticipant
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There are just some things that occur to the bullet that we just can’t do anything about no matter how much we discuss, cogitate and dwell on it on forums. I’m not losing any sleep over this one…….
- December 7, 2016 at 8:35 pm #31904Butch WaxParticipant
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Have had cast loads that defied logic.
But as my old captain always said:
“If it’s stupid and it works, it ain’t stupid.”
Dress right Larry, I’m falling in rank with ya.
- December 8, 2016 at 2:43 am #31915popperParticipant
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Only frictional heat, weak structure deformed by high pressure or buffeting from variation of the shock wave can cause damage. Doesn’t happen with boolits.
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