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Ken howell and others who understand the black arts of ballistics and finer things. The other evening a friend of mine...yes I have one...called me on the phone all excited or should I say aggitated. He is the know-it-all sort and unfortunatly he is often correct. Any way to elongate this story my friend posts on the Marlin board, I do not tell him where we are....so it goes ...he is in this arguement with several other guys about the point of impact of two rounds fired from the same gun. The aruguement goes like this: A 38 spcl round fired at a target 25 yard distant, using a 158gr bulletit will strike the target 2 inches higher than a 158 gr. bullet from a 357 round fired from the same gun. The arguement is that the cause of the disparity is recoil and and the speed of the bullet traveling down the barrel. The Marlin guys say the 38 strikes the target higher because the bullet is moving slower down the barrel thus the recoil action moves the muzzel upwards more than the the 357 before the bullet exits.I find this pretty hard to buy for several reasons. What do you think.

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Two bullets of the same weight, fired from the same gun but different velocities.The faster of the two will group lower.

As a projectile starts moving down the barrel, the handgun begins to recoil. Regardless of velocity, each will start recoiling at the same time.

The faster of the two will exit the barrel in less time. The muzzle rise is less at that moment. The projectile will impact at a lower point on the target.

Conversely, the slower of the two takes longer to exit the barrel. The muzzle will have risen more by the time the projectile exits the barrel. The impact point on the target will be higher.

Coincidentally, I was at the range today firing my Model 10 with practice and full power loads. The results were as above. The FP loads grouped lower.

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Yeah, he's right, at least for handgun rounds.

The same thing can hold true for rifles, though because of barrel whip all sorts of interesting things can happen when different rounds are fired through a longer barrel. But quite often slower, heavier bullets also strike higher even from a rifle.


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Steve and MuleDeer, I would agree with you fully except i keep letting little things like recoil velocity get in the way. I am not saying you are wrong but a 357 has a greater recoil than a 38 so in my reasoning the time for the bullet to travel the barrel length will offset the the degree of muzzle rise to some percent.This all happens so fast it is hard to envision so inorder to answer my question I will attempt to work this out in an equasion. I suspect you are rite as the facts do indicate there must be some force acting on the gun to make it elevate more for the 38 than the 357 at the time the bullet exits the muzzle. Thus the fulcrum point of the grip design combined with the the recoil velocity and the time of bullet travel down the barrel will dictate the point of impact. If the gun were held in a devise such as a Ransom rest and not allowed to recoil in an upwards ark the POI could be the same or reversed. I need to go do the math, at least as much as I can with out having a method of determining muzzle rise due to design of gun grip fulcrum. Time for the calculator exercise.

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OK due to voo doo math I am now in full agreement with recoil causing the disparity in POI. The time that pressue is exerted on the face of the action is greater in the 38spcl by a very small amount, the resistance to recoil by the grip one has on ones gun is negated mostly by the grip resistance being similar (same for sake of arguement) in the force one holds ones gun. The force exerted is admittdly less from the 38 than the 357 but the time the force is applied is longer than the 357 thus it is possible, probable, that the muzzle rise for the 38 is a few ten thousandths of an inch greater than the 357 thus making the POI of the 38 greater in elevation than 357 at point blank range or less. The results can be varied to make changes in POI by altering powders, primers, cases, ect. So in the real world this is just an arguement for the sake of arguement. I am now a believer.



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Last edited by Bullwnkl; 09/18/03.

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Anything can happen, in either a rifle or a handgun, depending on how a raft of variables work with and against each other. On Tin Cup Creek in 1955, I took an easy, can't-miss shot at a standing buck with an untested load in my .30-06 Improved. I had been shooting 180-grain Bronze Points but had instead -- that day -- a batch of cartridges loaded with heavier bullets (220-grain Core Lokts) and several grains less of the same powder (IMR-4350, IIRC). I expected to shoot a bit low but shot several inches high.

My ballistician professor said that was a common occurrence and explained it as a function of the two bullets' exiting the muzzle at significantly different points in the arc of the vibrating muzzle.

The difference in impacts could easily be otherwise -- even the opposite -- with other bullet weights, powder charges, and barrels.


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When I was first in the service, one of my instructors used to refer to events like this as "Ballistic Magic". IOW, he couldn't provide an answer, or at least one that we could understand. <img src="/ubbthreads/images/graemlins/frown.gif" alt="" />

Years later, when I was teaching, I tried to explain how pressure spikes could move back and forth on a graph. I thought that the time/pressure graph would be self explanatory. I was wrong. It generated more questions than I had answers for. With one young fellow, I said (as Yoda from Star Wars would undoubtedly say-paraphrased) "Accept that the spike will move and accept that you control its movement. As you learn control, so shall you understand the mystery."
It worked. At least it worked well enough to satisfy his curiousity.

Getting back to the subject at hand, test what you don't believe or understand and it will be easier to accept. If you run across and engineer, try this one. I don't have time to understand the theory. I've only got a week to make this crap work!

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Steve Redgwell
303british.com



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Steve Redgwell
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Steve, I have found this usefull as an explanation of the inexplicable at times. When someone asks why does thus and so happen and you know it does but can't really explain why the answer is BECAUSE GOD WANTS IT TO.

You can have that one for free. <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />


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Ken I have long understood the vibration effect of rifle barrels, that is often why we handload to over come one particular effect of that vibration and make the rifle shoot to a particulat POI. A rifle barrel is more prone to show the effects of vibration than a short stiff pistol barrel. A handloader can fine tune his loads to compensate accordningly. This is also possible with the 38-357 but it believe it would be much more difficult, kind of like turning an apple into an orange. I find that when shooting my S&W 586 357 at a 100 yrd target 38 Spcl bullets hit at least 1.5 ft to the left when compared to 357. This is particular to this gun. I will have a very difficult time trying to get my all-knowing friend to buy off on the recoil and or vibration as he has shot his mouth off so much proclaiming that recoil can not be the cause of the disparity in POI nor could vibration...whats left. No I think I will just let him live in his belief that he is rite and the rest of the world is wrong.
On another note Ken can you pass on the loads you use for your 220, need a starting point, The 220 is going on my Mex 34 I ordered a barrel and a will aquire the reamer once the barrel arives. The Ruger #1 is just a bit more trouble than I care to deal with and besides a friend wants it he will trade me a Sako in 22-250 that I have coveted for a long time. Hope to have barrel in a month 26" 3 grove Pac Nor. So perhaps buy Christmas the first rounds will be down range.

Bullwnkl.


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