- #1
dshield55
- 17
- 1
This question really does the need assistance of somebody trained in physical sciences. I've asked countless gun people and they are very opinionated but few of them can put forward answers that show they know anything about physical science.
I myself dropped out of Engineering school halfway through, and 10 years ago I could have pulled out formulas and stuff and diagrammed this out, but it's been soo long, I just can't do it anymore. I'm getting confused looking at formulas for springs and stuff.
I need to know if changing the weight of the moving parts of an AR15 can reduce recoil, or if the principal of conservation of energy overrides any changes in weight, whether lighter or heavier. The gas from the barrel of the AR15 travels down a tube from the barrel, and hits what's called the "gas key." The gas key is connected to the BCG (bolt carrier group.) When the gas hit's the BCG's gas key, that's what starts the rearward travel of the parts. Behind the BCG is a metal part about 3 inches long called a buffer. It's just a weight. The BCG and buffer are two separate parts, but they act as a single unit when moving. Behind the buffer is a spring. The spring keeps constant pressure on the buffer which means the buffer is always in contact with the BCG. As the BCG and Buffer move backwards against the spring, eventually the BCG/Buffer will hit the very back of the tube that they're traveling which starts their return trip back into battery. I setup a system with a stronger spring and tuned gas port so that the BCG/Buffer never actually hit the back of the tube, but rather they're fully arrested by the spring's pressure before returning it all back into battery.
My question is, if I change the weight of the BCG and/or Buffer, will that make any difference at all in felt recoil? Conservation of energy would tell me that if I doubled the weight it would just mean that the BCG/Buffer travel at half the speed but would still compress the spring just as far and impart just as much energy into the shooters shoulder. Conversely, if I cut the weight in half, it would just mean that the BCG/Buffer move at twice the speed but still compress the spring just as far and impart just as much energy into the shooters shoulder as if I did nothing at all. Is that correct? Or are there ways that cutting or increasing the weight might actually decrease felt recoil?
For instance, right now I'm leaning towards cutting the weight would decrease felt recoil because since it's the same momentum in the system but traveling twice as fast, that means that the same amount of force is being applied to my shoulder but for half the time, right?
Please keep in mind there are two different types of recoil that I'm aware of when shooting. The first is from the bullet and gasses traveling down the barrel and leaving the barrel. In a bolt action rifle, that would be the only recoil. But in a semi-automatic, the bolt parts start flying rearward creating recoil too. The latter is what I'm concerned with in this discussion.
If somebody is interested in point of data. A light BCG/Buffer system would weigh approximately 11oz. The travel distance is 6 inches, and the cyclic rate is 800 rounds per minute if it were full auto. A heavy system would probably weigh 16 oz. I don't have any data for spring pressures or anything. And the above data points are best guesses.
Here's the post I made at AR15.com that I need the answer to, please take a look at what the gun hobbyists are saying: http://www.ar15.com/forums/t_3_118/..._BCG_for_less_recoil__isn_t_it_the_same_.html
If you don't know how an AR15 works and my description above wasn't helpful, here's a youtube video demonstrating the operation:
I myself dropped out of Engineering school halfway through, and 10 years ago I could have pulled out formulas and stuff and diagrammed this out, but it's been soo long, I just can't do it anymore. I'm getting confused looking at formulas for springs and stuff.
I need to know if changing the weight of the moving parts of an AR15 can reduce recoil, or if the principal of conservation of energy overrides any changes in weight, whether lighter or heavier. The gas from the barrel of the AR15 travels down a tube from the barrel, and hits what's called the "gas key." The gas key is connected to the BCG (bolt carrier group.) When the gas hit's the BCG's gas key, that's what starts the rearward travel of the parts. Behind the BCG is a metal part about 3 inches long called a buffer. It's just a weight. The BCG and buffer are two separate parts, but they act as a single unit when moving. Behind the buffer is a spring. The spring keeps constant pressure on the buffer which means the buffer is always in contact with the BCG. As the BCG and Buffer move backwards against the spring, eventually the BCG/Buffer will hit the very back of the tube that they're traveling which starts their return trip back into battery. I setup a system with a stronger spring and tuned gas port so that the BCG/Buffer never actually hit the back of the tube, but rather they're fully arrested by the spring's pressure before returning it all back into battery.
My question is, if I change the weight of the BCG and/or Buffer, will that make any difference at all in felt recoil? Conservation of energy would tell me that if I doubled the weight it would just mean that the BCG/Buffer travel at half the speed but would still compress the spring just as far and impart just as much energy into the shooters shoulder. Conversely, if I cut the weight in half, it would just mean that the BCG/Buffer move at twice the speed but still compress the spring just as far and impart just as much energy into the shooters shoulder as if I did nothing at all. Is that correct? Or are there ways that cutting or increasing the weight might actually decrease felt recoil?
For instance, right now I'm leaning towards cutting the weight would decrease felt recoil because since it's the same momentum in the system but traveling twice as fast, that means that the same amount of force is being applied to my shoulder but for half the time, right?
Please keep in mind there are two different types of recoil that I'm aware of when shooting. The first is from the bullet and gasses traveling down the barrel and leaving the barrel. In a bolt action rifle, that would be the only recoil. But in a semi-automatic, the bolt parts start flying rearward creating recoil too. The latter is what I'm concerned with in this discussion.
If somebody is interested in point of data. A light BCG/Buffer system would weigh approximately 11oz. The travel distance is 6 inches, and the cyclic rate is 800 rounds per minute if it were full auto. A heavy system would probably weigh 16 oz. I don't have any data for spring pressures or anything. And the above data points are best guesses.
Here's the post I made at AR15.com that I need the answer to, please take a look at what the gun hobbyists are saying: http://www.ar15.com/forums/t_3_118/..._BCG_for_less_recoil__isn_t_it_the_same_.html
If you don't know how an AR15 works and my description above wasn't helpful, here's a youtube video demonstrating the operation: