View Full Version : Buffer bumper material
From a most interesting but very long thread I do not wish to lengthen further with ancillary digression:
Possibly, but probably not.
People don't know a good portion of the forward velocity comes from the buffer tip rebounding off the end of the RE.
The action spring can't really deliver much energy during the 1/4" of over travel, but the buffer tip returns some % of the rearward velocity nearly instantly.
Assuming this rebound is undesirable, as I understand it to be, is there no material with greater hysteresis that is sufficiently rigid and durable? Polymer science has likely improved since the original material was specified.
I'm no engineer, but it strikes me that you're searching for a problem with the buffer system that doesn't seem to exist. I mean... in my years of running this platform, I've found the WAY bigger problem is incompetence from those who've set specs for gas ports.
"We" shot the AR for decades with over gassed ports that lead to all kinds of functionality issues and false hysteria on the system's reliability; and also all kinds of ridiculous aftermarket gizmos (pig tail gas tube, for example) to treat the symptoms of these over gassed nightmares.
I'm not trying to be argumentative, but it seems that the buffer system in place is just fine.
It's not necessarily undesirable.
It just means the closing velocity during the normal cycle is higher than the closing velocity of the first round chambered when using the bolt catch or charging handle.
BTW, one of the other things that pesky little A5 biasing spring does is reduce the rebound energy.
From a most interesting but very long thread I do not wish to lengthen further with ancillary digression:
Assuming this rebound is undesirable, as I understand it to be, is there no material with greater hysteresis that is sufficiently rigid and durable? Polymer science has likely improved since the original material was specified.
markm, I cannot disagree. I find the exploration of the physical properties of the system interesting in itself. I read the entire exchange between lysander and StainlessSlide for example.
Clint, thank you.
We tested a lot of different designs and materials for the LARB tail cap for those reasons...
Interesting product. The conical contact face makes sense to me. How does the thermal and chemical stability of your material compare to the original? What is its fatigue life? Have you measured energy return for the two bumper types?
Magnetic eddy current braking should be excellent here, if damping is desired, and searching for that I found the Omni Robusta LLC M.A.R.R.S. Buffer. It doesn't appear quite ready for market to me—I don't like the abrupt ledge between the body and the tail—however with development I think the concept could become the reference design.
Interesting product. The conical contact face makes sense to me. How does the thermal and chemical stability of your material compare to the original? What is its fatigue life? Have you measured energy return for the two bumper types?
Magnetic eddy current braking should be excellent here, if damping is desired, and searching for that I found the Omni Robusta LLC M.A.R.R.S. Buffer. It doesn't appear quite ready for market to me—I don't like the abrupt ledge between the body and the tail—however with development I think the concept could become the reference design.
The material we use will last the life of the weapon, we have yet to wear one out and every been trying for the last 4 years. Unless you’re cleaning your weapon with aircraft paint stripper, we haven’t had any chemical issue whatsoever ever. We did energy absorption testing by way of bolt velocity/ rate of fire.
We did energy absorption testing by way of bolt velocity/ rate of fire.
Do you publish those values?
Do you publish those values?
No, only thing we released was a percentage, which was around 20% reduction. You don’t let everyone see all your cards. ��
From a most interesting but very long thread I do not wish to lengthen further with ancillary digression:
Assuming this rebound is undesirable, as I understand it to be, is there no material with greater hysteresis that is sufficiently rigid and durable? Polymer science has likely improved since the original material was specified.
Rebound on the back end IS desirable. It allows for a greater velocity when closing than the spring can deliver without becoming difficult to open.
It's rebound off the barrel extension that is undesirable.
OH, and the original material was a polyether urethane with a hardness of 95 Shore A. It was chosen because of its good rebound properties. Remember the original buffer design was a stiff spring.
Rebound on the back end IS desirable. It allows for a greater velocity when closing than the spring can deliver without becoming difficult to open.
If that's the case are the many comments and products relating to slowing cyclic rate misguided or do I misunderstand?
If one were to accept the more difficult to open action could a stronger spring that has the buffer never quite touch the back of the tube, something like my limited understanding of the "constant recoil" concept, be made to work or would it fail for another reason?
I've been running some Jones EAB buffer tips for some months now. They do make a difference but it is subtle. They have been holding up well also.
If that's the case are the many comments and products relating to slowing cyclic rate misguided or do I misunderstand?
If one were to accept the more difficult to open action could a stronger spring that has the buffer never quite touch the back of the tube, something like my limited understanding of the "constant recoil" concept, be made to work or would it fail for another reason?
It all depends. If you have excessive bolt velocity, then you need to slow it down. That can be done in a variety of ways, a stronger spring, less gas, absorbing energy on the rebound, etc. But, a stiff buffer bumper will cause a higher recoil impulse to the firer's shoulder, more felt recoil, and a "jumpier" gun. It needs to be balanced.
However, if you stiffen the spring up enough that the buffer never bottoms out, you will never open the action by hand.
The bolt on an M16 (20 inch barrel, full length and weight buffer, .96 lbs), needs about 18 fps bolt velocity to reliably work the cycle of operations, you can figure out how stiff a spring you're going to need to stop that in less than 5 inches
However, if you stiffen the spring up enough that the buffer never bottoms out, you will never open the action by hand.
The bolt on an M16 (20 inch barrel, full length and weight buffer, .96 lbs), needs about 18 fps bolt velocity to reliably work the cycle of operations, you can figure out how stiff a spring you're going to need to stop that in less than 5 inches
Fascinating. I would not have guessed! I suppose then attempting to come at this from the other direction by valving off gas until the buffer just taps the back of the tube with a standard weight spring the system will not attain the necessary 18 fps for reliable cycling?
The effort required to reliably extract an empty case and clear the barrel extension enough to eject is what governs the bolt velocity.
If you want to experiment, remove the action spring, and close off an adjustable gas block. Gradually open the gas as you shoot, and see what the minimum amount of gas is required to reliably eject a case, and see if you can keep the carrier/buffer from bottoming out in the RE.
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