do chamber pressures effect recoil?

dgang · September 27, 2002, 06:25 PM

This may seem as a simple question to some, pure physics, but I'm forced to ask it. If a reloader were to load, say a .45-70 cartridge, with a fast burning powder that propelled a 300 gr. bullet at 2000 fps. that generated 30,000 CUP of pressure it would produce "X" amount of recoil. Now if that same bullet was sent on its way at the same velocity but instead a slower burning powder was being used that only generated 25,000 CUP of pressure would the "felt" recoil be less? Newton's law of motion would dictate the same recoil would exist for both loads, but would a less severe pressure spike being produced by the slower burning powder result in less felt recoil? And if so, would it be noticable? Thanks in advance and good shootin' to ya'all. dgang

Double Naught Spy · September 27, 2002, 11:45 PM

Newton's does not quite work here I don't think. It is not the weight of the object being propelled as much as the force pushing backwards as caused by the expanding gasses.

Interestingly, I have noticed that some apparently faster burning powders seem to create a different recoil than slower burning powders even when the projectile is leaving at about the same velocity. Faster powder seems to produce more of a slap or sharp feeling recoil whereas slower powders tend to produce more of a push.

Maybe the do have the same actual recoil force according to the physics. I don't actually know if that is true or not. If so, then the key difference difference is in what is felt.

For example, according to Forker's Ammo and Ballistics book, 230 gr. Fiocchi FMJ ammo out of a 5" barrel comes out at about 875 fps. Blazer 230 gr. FMJ comes out at about 845 fps. Hydrashok 230 gr. comes out at 850 fps. Based on my experience and shooting with others, the Blazer and Hydrashok both give the impression of being loaded hotter as they have a sharp recoil and produce a goodly-sized flash. The Fiocchi has a softer push recoil even with the higher velocity. Obviously, you would expect the Fiocchi to have the greater recoil as it pushes out a same weight object at a higher velocity, but that isn't the case - at least not as far as I can tell.

C.R.Sam · September 27, 2002, 11:52 PM

Same bullet
Same velocity...
If there was greater weight of the slower powder...recoil should be slightly greater at the lower pressure.

Probably feel the other way around tho.
The faster powder expends it's push quicker.

So sharp whap vs slower but more total push.

Would probably have to use an instrumented machine rest to tell what is really goin on.

Sam

Steve Smith · September 28, 2002, 12:20 AM

Sometimes you can feel it in your eyes and sinuses.

**Bud Helms** · September 28, 2002, 07:51 AM

What C.R.Sam said. I think pressure only affects recoil in as much as it affects velocity of the projectile. "Felt" recoil probably changes with the "impulse" of the pressure peak. Same energy (bullet mass at some avg velocity) spread over a longer period might feel less. Kind of an "area under the curve" problem. Narrow high pulse vs wide low pulse. Impulse goes something like: the product of the average value of a force and the time during which it acts. Is there a Physicist in the house?

Steve Smith, I might be telling you something you already know, but when you get old enough and your sinuses seem closed for good and your arms get shorter by the day (need glasses), it doesn't seem to bother so much.

KP95DAO · September 28, 2002, 09:22 AM

Given the same velocity, the weight of the ejecta, bullet and powder, will make a difference. The use of "slower" burning powder means more of it. This will increase the "actual" recoil. How it is "felt" is a subjective thing. Another factor is the "jet effect" and its effect on recoil, both real and imagined. There will be more of a jet effect with a much slower burning powder; ie, Hornady's "Light and Heavy Magnum" loads.

BigG · September 28, 2002, 09:29 AM

From loading 45 ACP with same projo to same velocity with both Bullseye (faster) and Unique (slower) - the seat of pants impression is that Unique quicks less. It's actually just a slower kick where the Bullseye rares right back, NOW.

Southla1 · September 28, 2002, 11:31 AM

I loaded some 140 grain Nosler ballistic tips in my 7MM Rem mag to the same velocity (3000 FPS chronographed) as the 150 grain Nosler Partition that I hunt with.

The 140's I used IMR-4895 (because I have so much on hand) the 150's I use H-4831.

The 140 are a tear bringing snot running recoiling SOB while IO don't even seem to notice the 150's. Maybe it's in my mind but I certainly feel the difference.

I know that it should seem impossible to feel the difference in acceleration of almost the same weight bullet to the same velocity in a 24" barrel but my shoulder says different, and to top it off I am not recoil shy.

dgang · September 28, 2002, 01:07 PM

Thank you gentleman for your varied replies. You've shed some light on my question. Good shootin' to ya' all. dgang

September 27, 2002, 06:25 PM	#1
dgang Senior Member Join Date: April 15, 2000 Location: Colorado Posts: 211	do chamber pressures effect recoil? This may seem as a simple question to some, pure physics, but I'm forced to ask it. If a reloader were to load, say a .45-70 cartridge, with a fast burning powder that propelled a 300 gr. bullet at 2000 fps. that generated 30,000 CUP of pressure it would produce "X" amount of recoil. Now if that same bullet was sent on its way at the same velocity but instead a slower burning powder was being used that only generated 25,000 CUP of pressure would the "felt" recoil be less? Newton's law of motion would dictate the same recoil would exist for both loads, but would a less severe pressure spike being produced by the slower burning powder result in less felt recoil? And if so, would it be noticable? Thanks in advance and good shootin' to ya'all. dgang __________________ I shoot, therefore I am.

September 27, 2002, 11:45 PM	#2
Double Naught Spy Senior Member Join Date: January 8, 2001 Location: Forestburg, Montague Cnty, TX Posts: 12,793	Newton's does not quite work here I don't think. It is not the weight of the object being propelled as much as the force pushing backwards as caused by the expanding gasses. Interestingly, I have noticed that some apparently faster burning powders seem to create a different recoil than slower burning powders even when the projectile is leaving at about the same velocity. Faster powder seems to produce more of a slap or sharp feeling recoil whereas slower powders tend to produce more of a push. Maybe the do have the same actual recoil force according to the physics. I don't actually know if that is true or not. If so, then the key difference difference is in what is felt. For example, according to Forker's Ammo and Ballistics book, 230 gr. Fiocchi FMJ ammo out of a 5" barrel comes out at about 875 fps. Blazer 230 gr. FMJ comes out at about 845 fps. Hydrashok 230 gr. comes out at 850 fps. Based on my experience and shooting with others, the Blazer and Hydrashok both give the impression of being loaded hotter as they have a sharp recoil and produce a goodly-sized flash. The Fiocchi has a softer push recoil even with the higher velocity. Obviously, you would expect the Fiocchi to have the greater recoil as it pushes out a same weight object at a higher velocity, but that isn't the case - at least not as far as I can tell. __________________ "If you look through your scope and see your shoe, aim higher." -- said to me by my 11 year old daughter before going out for hogs 8/13/2011 My Hunting Videos https://www.youtube.com/user/HornHillRange

September 28, 2002, 09:22 AM	#6
KP95DAO Senior Member Join Date: December 30, 2000 Posts: 699	Recoil. Given the same velocity, the weight of the ejecta, bullet and powder, will make a difference. The use of "slower" burning powder means more of it. This will increase the "actual" recoil. How it is "felt" is a subjective thing. Another factor is the "jet effect" and its effect on recoil, both real and imagined. There will be more of a jet effect with a much slower burning powder; ie, Hornady's "Light and Heavy Magnum" loads.

September 28, 2002, 01:07 PM	#9
dgang Senior Member Join Date: April 15, 2000 Location: Colorado Posts: 211	Thank you gentleman for your varied replies. You've shed some light on my question. Good shootin' to ya' all. dgang __________________ I shoot, therefore I am.

September 27, 2002, 11:52 PM	#3
C.R.Sam Senior Member Join Date: October 30, 1999 Location: Dewey, AZ Posts: 12,858	Same bullet Same velocity... If there was greater weight of the slower powder...recoil should be slightly greater at the lower pressure. Probably feel the other way around tho. The faster powder expends it's push quicker. So sharp whap vs slower but more total push. Would probably have to use an instrumented machine rest to tell what is really goin on. Sam

September 28, 2002, 12:20 AM	#4
Steve Smith Senior Member Join Date: December 9, 1999 Posts: 4,131	Sometimes you can feel it in your eyes and sinuses.

September 28, 2002, 07:51 AM	#5
Bud Helms Senior Member Join Date: December 31, 1999 Location: Middle Georgia, USA Posts: 13,198	What C.R.Sam said. I think pressure only affects recoil in as much as it affects velocity of the projectile. "Felt" recoil probably changes with the "impulse" of the pressure peak. Same energy (bullet mass at some avg velocity) spread over a longer period might feel less. Kind of an "area under the curve" problem. Narrow high pulse vs wide low pulse. Impulse goes something like: the product of the average value of a force and the time during which it acts. Is there a Physicist in the house? Steve Smith, I might be telling you something you already know, but when you get old enough and your sinuses seem closed for good and your arms get shorter by the day (need glasses), it doesn't seem to bother so much.

September 28, 2002, 09:29 AM	#7
BigG Senior Member Join Date: May 20, 1999 Location: Atlanta, GA Posts: 4,334	From loading 45 ACP with same projo to same velocity with both Bullseye (faster) and Unique (slower) - the seat of pants impression is that Unique quicks less. It's actually just a slower kick where the Bullseye rares right back, NOW.

September 28, 2002, 11:31 AM	#8
Southla1 Member In Memoriam Join Date: March 19, 2000 Location: Jeanerette, La. Near the Posts: 1,999	I loaded some 140 grain Nosler ballistic tips in my 7MM Rem mag to the same velocity (3000 FPS chronographed) as the 150 grain Nosler Partition that I hunt with. The 140's I used IMR-4895 (because I have so much on hand) the 150's I use H-4831. The 140 are a tear bringing snot running recoiling SOB while IO don't even seem to notice the 150's. Maybe it's in my mind but I certainly feel the difference. I know that it should seem impossible to feel the difference in acceleration of almost the same weight bullet to the same velocity in a 24" barrel but my shoulder says different, and to top it off I am not recoil shy.