Range Report .45/70 fast load low, slow load high

[DP425]

For some reason my brain is just not functioning right today. Got a guy says his .45/70, when zeroed 3.5" high @ 100yds with 1975fps, will print loads traveling at 1150fps 7-8" high. His theory is the bullet is exiting the barrel during recoil at a higher angle thus explaining his impacts. This doesn't settle well with me.

What is another explanation?

 

[Oneteam]

Re: .45/70 fast load low, slow load high

The slower round is staying in the barrel just a bit longer, thus exits the barrel at a slightly higher angle. Just a millimeter difference in barrel angle has a lot of change at 100 yards. I have experienced this same thing over the years.

 

[former naval person]

Re: .45/70 fast load low, slow load high

Not unusual with the .45-70. Recoil pushes back and up with the muzzle. My neighbor has one of the Long Barrel Buffalo Gun single shots that prints a foot difference when shifting from 300 to 405 grain bullets!

 

[DP425]

Re: .45/70 fast load low, slow load high

hmmm okay

 

[Cape_hunter]

Re: .45/70 fast load low, slow load high

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DP425</div><div class="ubbcode-body">hmmm okay</div></div>

Kinda were I am on this.

I am not on board with this. The bullet is clear of the bore buy the time the recoil transfers back to he shooter and the muzzle rises.

I could be wrong.

 

[The Mechanic]

Re: .45/70 fast load low, slow load high

Sounds like a flinch to me.

 

[Greg Langelius *]

Re: .45/70 fast load low, slow load high

Yout friend is dead-on right.

Third law of motion, every action results in an equal and opposite reaction.

There is no mention of any delay.

The firearm is definitely moving in the opposite direction while the bullet traverses the length of the barrel. Because the direction of freedom is upward as well as rearward, muzzle climb occurs.

This phenomenon is so common it is used to regulate fixed handgun sights by adjusting cartidge loads.

Doubters are welcome to explain the mechanism whch prevents this until after the bullet exits.

Greg

 

[DP425]

Re: .45/70 fast load low, slow load high

Well, I have looked at high-speed video of firearms firing- it is generally pretty clear that brunt of recoil occurs after the bullet leaves the firearm. But it does seem the consensus is the small amount of recoil that is present when the firearm still has the projectile in the barrel is enough to change the path of departure given a long enough barrel and/or slow enough bullet.

 

[Cape_hunter]

Re: .45/70 fast load low, slow load high

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">Yout friend is dead-on right.

Third law of motion, every action results in an equal and opposite reaction.

There is no mention of any delay.

The firearm is definitely moving in the opposite direction while the bullet traverses the length of the barrel. Because the direction of freedom is upward as well as rearward, muzzle climb occurs.

This phenomenon is so common it is used to regulate fixed handgun sights by adjusting cartidge loads.

Doubters are welcome to explain the mechanism whch prevents this until after the bullet exits.

Greg</div></div>

After my post last night I watched several hi-speed videos trying to get a handle on this. Also spent a couple hours reading around the interwebs... looking for data.
From what I can find the change in minimal at best and barely measurable if at all. Now while you are spot on based on the physics, it would appear that shooter anticipation is more the root of the POI change in heavy recoil firearms.

Having said that Greg, I do enjoy threads like this. Lots of good debate and info can usually be had.

 

[Cape_hunter]

Re: .45/70 fast load low, slow load high

Found this little tidbit......
Thread on POI change due to recoil

"Ok, the physics are correct but there's nothing like empirical data so, I called an old friend of mine today. He's a retired engineer from the Rock Island Arsenal. He's done work on the m198 Howitzer and the new 105mm Hawkeye.

His work involves the mechanics and stresses associated with recoil so I asked him about this subject.

He tells me that both sides of the argument have merit but only if we are willing to split hairs. At initial ignition of the charge, there is a small and barely perceptible motion of the barrel/breach. (only detectable by sensitive instrumentation) However, this motion is of so little significance that it has no practical effect on POI.

However, the motion widely accepted as recoil, were it to take place while the projectile were still in the barrel, would make POI so unpredictable as to make any sighting system useless; nothing more than decoration on the weapon.
<span style="color: #FF0000">
In short, recoil occurs only after the projectile has exited the barrel and has no effect on POI"</span>

 

[DP425]

Re: .45/70 fast load low, slow load high

primary and secondary recoil. Primary is while still in the barrel and very small

 

[spawn_mm_jtf2]

Re: .45/70 fast load low, slow load high

may I point back to my topic.. I had a similar issue with slow 150gr vs hot-loaded 140gr...
http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=3178164#Post3178164