joshua99ta
Well-Known Member
i found this on a forum not pertaining to guns at all but there is a sections for guns and hunting and stuff .... so can SOMEBODY translate the point this guy is trying to make?!?
How many of us here shoot something like a 50 or 55 grain bullet in a 1:8 or 1:9 twist .223? Or maybe a 1:8 twist in one of the various 6mm rounds? We all have at onetime or another.
Last night I was up late with Parker and his wisdom, and here's some thoughts I stole out of his mind:
* the bullet enters the rifeling, and starts a chain reaction as well as the well known reaction. When the bullets enters the rifeling it actually twists the barrel as it is pushed the the barrel, and the the like reaction occurs when the barrel will actually uncoil. In otherwords the barrel becomes a giant coiled spring
* The difference in energy lost from the rifeling in a 1:14 twist barrel and the now in vogue one and eight twist is roughly 25%. It takes much more power to push a bullet thru a fast twist barrel than a slow twist barrel. When you increase the resistance to the bullet going thru the rifeling you also induce a like action into the barrel material, and as the bullet passes by the like reaction occurrs with the barrel trying to "unwind" (I bet Calffee never thought about that one!!). So in the end the more resistance, the more stress is added into the barrel after ignition
* Now that we've completely abused the barrel, lets see what elses happens. The bolt is the next victim. As the barrel tries to twist, it also tries to move the chamber end, and the bolt face (the hotter the load the more pronounced this is). This energy is then transfered to the actual reciever frame. Then of course it over reacts the other way on the return trip to the static position. We ain't done!
* how many of us have just had to have a "speed lock" kit? GUILTY as charged! Light weight firings pins and heavy springs are nothing but a crutch to help fix an engineering problem. (Mauser, Winchester, and 700 Remingtons come to light here). Think about it a minute; the case slides into the chamber very easilly, so it obvious there some clearence there (as it should be). You lock the bolt into position to then set the correct headspace (I hope you did this right). You release the firing pin and it strikes the primer. The rest is history. But alas we all want those magic lock time numbers. We add a titanium firing pin (a harmonic distortion problem in itself), and a spring that looks and feels like it's a left over purple stripe race hemi valve spring. Now the firing pin hits the primer like a sledge hammer, and actually shoves the case forward (so much for headspace). It hits the primer so damned hard that it acts like a tap dancer in the face of the primer. If the firing pin strikes a few thousands off center it cocks the case sideways ever so slightly creating a displacement laterally. What we should be after is one clean strike just good enough to set the primer off on a dead center axis to the centerline of the case. But alas we had an engineer design into this equation a four inch long firing pin and a very short bearing surface to guide the firing pin into the primer. In reality a 1.5" firing pin is all we need in a properly designed bolt. Use a small return spring (both in weight and size). Without the spring being contained inside the firing pin itself; we also take all the harmonics associated with hardened steel out of the firing pin. And the return spring acts as a shock absorber. Anybody here know what the lock time king is? I'll give you a hint; it's none of above and they also are not pretty.
gary
How many of us here shoot something like a 50 or 55 grain bullet in a 1:8 or 1:9 twist .223? Or maybe a 1:8 twist in one of the various 6mm rounds? We all have at onetime or another.
Last night I was up late with Parker and his wisdom, and here's some thoughts I stole out of his mind:
* the bullet enters the rifeling, and starts a chain reaction as well as the well known reaction. When the bullets enters the rifeling it actually twists the barrel as it is pushed the the barrel, and the the like reaction occurs when the barrel will actually uncoil. In otherwords the barrel becomes a giant coiled spring
* The difference in energy lost from the rifeling in a 1:14 twist barrel and the now in vogue one and eight twist is roughly 25%. It takes much more power to push a bullet thru a fast twist barrel than a slow twist barrel. When you increase the resistance to the bullet going thru the rifeling you also induce a like action into the barrel material, and as the bullet passes by the like reaction occurrs with the barrel trying to "unwind" (I bet Calffee never thought about that one!!). So in the end the more resistance, the more stress is added into the barrel after ignition
* Now that we've completely abused the barrel, lets see what elses happens. The bolt is the next victim. As the barrel tries to twist, it also tries to move the chamber end, and the bolt face (the hotter the load the more pronounced this is). This energy is then transfered to the actual reciever frame. Then of course it over reacts the other way on the return trip to the static position. We ain't done!
* how many of us have just had to have a "speed lock" kit? GUILTY as charged! Light weight firings pins and heavy springs are nothing but a crutch to help fix an engineering problem. (Mauser, Winchester, and 700 Remingtons come to light here). Think about it a minute; the case slides into the chamber very easilly, so it obvious there some clearence there (as it should be). You lock the bolt into position to then set the correct headspace (I hope you did this right). You release the firing pin and it strikes the primer. The rest is history. But alas we all want those magic lock time numbers. We add a titanium firing pin (a harmonic distortion problem in itself), and a spring that looks and feels like it's a left over purple stripe race hemi valve spring. Now the firing pin hits the primer like a sledge hammer, and actually shoves the case forward (so much for headspace). It hits the primer so damned hard that it acts like a tap dancer in the face of the primer. If the firing pin strikes a few thousands off center it cocks the case sideways ever so slightly creating a displacement laterally. What we should be after is one clean strike just good enough to set the primer off on a dead center axis to the centerline of the case. But alas we had an engineer design into this equation a four inch long firing pin and a very short bearing surface to guide the firing pin into the primer. In reality a 1.5" firing pin is all we need in a properly designed bolt. Use a small return spring (both in weight and size). Without the spring being contained inside the firing pin itself; we also take all the harmonics associated with hardened steel out of the firing pin. And the return spring acts as a shock absorber. Anybody here know what the lock time king is? I'll give you a hint; it's none of above and they also are not pretty.
gary
