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re: A rule of thumb on changing point of impact on fixed sighted guns
Posted on 9/15/14 at 9:28 pm to Ice Cream Sammich
Posted on 9/15/14 at 9:28 pm to Ice Cream Sammich
Initial recoil impulse is not easily seen on that film.
The initial statement holds true, regardless of the reason.
The initial statement holds true, regardless of the reason.
1
Posted on 9/15/14 at 9:33 pm to weagle99
I provided proof. It was even labeled as such.
In all seriousness, please show me "initial recoil impulse". The video provided shows the bullet long gone before the gun even moved.
Powder density and burn rate from a larger projectile seems much more logical.
In all seriousness, please show me "initial recoil impulse". The video provided shows the bullet long gone before the gun even moved.
Powder density and burn rate from a larger projectile seems much more logical.
Posted on 9/15/14 at 9:45 pm to Ice Cream Sammich
Recoil begins the instant the bullet starts to move, regardless if it is captured on film.
I believe a slo mo film with a revolver might show the effect clearer.
Larger projectile? I assume you mean a heavier projectile and not a different / larger caliber.
The OP deals with speed of identical projectiles with different powder charges. I edited the post to clarify.
I believe a slo mo film with a revolver might show the effect clearer.
quote:
Powder density and burn rate from a larger projectile seems much more logical.
Larger projectile? I assume you mean a heavier projectile and not a different / larger caliber.
The OP deals with speed of identical projectiles with different powder charges. I edited the post to clarify.
This post was edited on 9/15/14 at 9:49 pm
Posted on 9/15/14 at 9:51 pm to weagle99
Larger as in larger mass. Additionally, the initial recoil is back, not up. By the time that the recoil goes from back to up, bullet is downrange.
Looking for Revolver video now.
Looking for Revolver video now.
Posted on 9/15/14 at 9:57 pm to Ice Cream Sammich
quote:
the initial recoil is back, not up
I believe there will be an almost instantaneous upward movement also.
quote:
by the time that the recoil goes from back to up, bullet is downrange.
For all barrel lengths?
This post was edited on 9/15/14 at 10:00 pm
Posted on 9/15/14 at 10:02 pm to weagle99
Barrel length slightly addressed in my previous post. Interesting to think about 2" vs 6" vs 12".
Posted on 9/15/14 at 10:02 pm to Ice Cream Sammich
Gun looks like it is moving up to me before the bullet exits. 
Cool video.
Cool video.
This post was edited on 9/15/14 at 10:05 pm
Posted on 9/15/14 at 10:05 pm to Ice Cream Sammich
quote:This. Revolver could be different.
The video provided shows the bullet long gone before the gun even moved.
Posted on 9/15/14 at 10:05 pm to weagle99
First video, yes. I believe that the gun is moving well before trigger is pulled. Video that starts at 14 seconds shows no movement.
Posted on 9/15/14 at 10:05 pm to AlxTgr
Posted on 9/15/14 at 10:07 pm to AlxTgr
Rugger pistol on Glock forum --> clearly bogusly invalid. 
Posted on 9/15/14 at 10:08 pm to Ice Cream Sammich
quote:
First video, yes. I believe that the gun is moving well before trigger is pulled. Video that starts at 14 seconds shows no movement.
Notice all the unburned powder exiting the barrel. The 2nd vid I posted shows burning powder between the cylinder and forcing cone also. Neat.
This post was edited on 9/15/14 at 10:09 pm
Posted on 9/15/14 at 10:12 pm to weagle99
Missed that the first time I watched it. I suspect that we can find a dozen videos showing zero movement and another dozen showing it rising 3"s.
Im done for tonight. I'll sleep on it and get back to it tomorrow.
Im done for tonight. I'll sleep on it and get back to it tomorrow.
This post was edited on 9/15/14 at 10:13 pm
Posted on 9/15/14 at 10:32 pm to Hu_Flung_Pu
quote:
Thought it was more of a trajectory thing because the heavier bullets "rainbow" more.
Are you thinking that a bullet rises when it leaves the barrel?
Posted on 9/15/14 at 10:38 pm to Ice Cream Sammich
That video doesn't really show me much. My response is based on a large revolver shooting rounds with about 1000 feet/second difference out of an 8 3/8" barrel. The results were the same with 3 different experienced shooters.
Posted on 9/15/14 at 10:44 pm to Shexter
quote:
Are you thinking that a bullet rises when it leaves the barrel?
No. Poi would be lower at same distance with heavier bullet. Rainbow was used to to accentuate a higher degree of bullet drop.
Posted on 9/15/14 at 10:47 pm to Hu_Flung_Pu
I may misunderstood the op. Might have meant bullet shoots higher (lands on paper higher) at same aiming point not you have to aim higher.
This post was edited on 9/15/14 at 10:48 pm
Posted on 9/15/14 at 11:40 pm to weagle99
A projectile of mass X will impact lower if it is moving slower, higher if moving faster (same point on aim, same distance, same barrel, etc). That is physics. Fire from a vise or test barrel and this is what will occur. Recoil impulse is one of those subjects with too many variables to even consider the old farm house anecdotes.
This should help.
Now, point of impact will change. The slower bullet of the same mass will indeed be higher at very close ranges, based solely on sight zero per velocity, However, the faster bullies will be higher for a greater majority of distances tested. Therefor, higher most of the time. Also depends on mass, velocity, zero, etc.
To clarify more, the slower moving trajectories show higher impact before the 100 yard zero solely because the different velocities are shown at a 100 yard zero. Bullet drop is indeed faster with slower moving projectiles.
This should help.
Now, point of impact will change. The slower bullet of the same mass will indeed be higher at very close ranges, based solely on sight zero per velocity, However, the faster bullies will be higher for a greater majority of distances tested. Therefor, higher most of the time. Also depends on mass, velocity, zero, etc.
To clarify more, the slower moving trajectories show higher impact before the 100 yard zero solely because the different velocities are shown at a 100 yard zero. Bullet drop is indeed faster with slower moving projectiles.
This post was edited on 9/16/14 at 12:07 am
Posted on 9/15/14 at 11:53 pm to weagle99
quote:
Slower rounds shoot higher.
Faster rounds shoot lower.
ETA: For identical projectiles.
This statement is true. Like weagle99, I've always heard it said that this occurs because recoil of the slower moving load has caused the barrel to move slightly upwards in recoil before the slower velocity round has exited the barrel. That may not be the exact reason, but I've yet to hear of a better alternative explanation. I'm not surprised if there's not a video out there to demonstrate this. The movement of the barrel need be very minuscule to affect the point of impact. I'd think it would take very special equipment to demonstrate this.
I hate to muddy the water, especially since I've defended the original post, but under some circumstances, the round's muzzle velocity can nullify the original statement. For example, I shoot a lot of high velocity, rifle type cartridges (i.e. 223 Remington, 7-08 and 308 Win to name a few) in long barreled specialty pistols like the Thompson/Center Contender and Remington XP-100. In these situations, the higher velocity round has a higher point of impact than does the lower velocity round.
Nevertheless, weagle99 points out an interesting fact that's not known to many.
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