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Discussion Starter #1
Not my video.
Different shooters on each rifle.
Note the bolt bounce.
More importantly note the cartridge bounce as it leaves the mag feed lips.
One of these three is not like the rest.

 

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I saw bolt-bounce on the SIG. Definitely not on the MR762 but could not tell on the Armalite. I suspect that the MR762 might have a tungsten filled recoil buffer like the 416/556 but I'll check for sure once I get home or unless someone with an MR762 wants to check theirs before then.
Not sure, however, how you can accurately put a ROF number on a semi-auto gun.
 

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They all exhibit the typical signs of guns operating at various bolt speeds.

THe AR10 is slightly overgassed and the bolt speed shows this. Outward signs are the fact that the brass doesn't exit the ejection port until the BCG is further to the rear, thusly making the angle of impact on the brass deflector throw the brass forward rather then straight out the side or to the rear. I'd bet that it's also running a lighter buffer then either of the other two due to the speed of the chambering section of the cycle. Assuming the use of a high quality, moderate loaded ammunition for the test, the use of higher loaded ammunition *could* (not necessarily will) cause malfunctions including FTE malfunctions, most likely caused by expended brass actually being fully extracted and ejected, but having such an impact angle on the rear edge of the ejection port that it literally bounces right back into the action. I've seen this malfunction in the AR platform many times in seriously overgassed guns.

The MR762 displays typical "light gas" operation with slower bolt speed and rechambering. This of course can be mimicked by several factors such as a possible stronger action spring and heavier buffer. I know the 416/MR556 come with those, so i'd venture a guess that the MR762 does as well. In all, not a bad thing, but it *can* (not will) make the rifle have reliability issues with lighter loaded ammunition, crappy surplus, etc., manifesting as failure to extract/failure to eject or even failure to feed issues as the system might not get enough gas to properly cycle thebolt.

THe Sig 716 seems to be the closest "dialed in" from the factory rifle in the group with a gas system set up to be able to handle a wider variety of loads. Bolt speed is appropriate, return cycle seems pretty smooth, brass is ejected nearly straight out the side.

Now, I don't know the perameters of this test, such as the number of rounds through each gun prior, the type of ammunition being used, how clean/dirty the rifles were, etc. Everything I said is based on an ASSUMPTION that all rifles were "new" within a few hundred rounds at most, that they were all clean and in proper working order, and that the ammunition used was a good quality factory loaded round and was the same type of ammunition in all of the rifles.

But, since we don't know any of that information, this video without context is simply just a neat thing to watch and really doesn't tell us much of anything at all.
 

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The MR762 displays typical "light gas" operation with slower bolt speed and rechambering. This of course can be mimicked by several factors such as a possible stronger action spring and heavier buffer. I know the 416/MR556 come with those, so i'd venture a guess that the MR762 does as well. In all, not a bad thing, but it *can* (not will) make the rifle have reliability issues with lighter loaded ammunition, crappy surplus, etc., manifesting as failure to extract/failure to eject or even failure to feed issues as the system might not get enough gas to properly cycle thebolt.
+1. It is my understanding that HK went with the heavier recoil spring on the HK416 to increase service life due to the increased energy delivered by a piston system. As a result, they expereinced bolt-bounce and had to tungsten fill the buffer. The MR556 retains these features.
 

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Discussion Starter #6
The neat thing about "bolt bounce" (really it should be "carrier bounce) is that it only really effects FA fire. In a semi-auto gun, it's virtually meaniningless.

Its far from meaningless in semiauto; it does add additional wear and tear, especially if the bounce is hard enough that the ejector is moving the cartridge in the chamber. It also opens another venue for debris to jam things up during that split second.

But, the thing that jumped out at me was the amount of bouncing around the cartridges did before coming to rest against the breech face; the MR762 looked far superior in that regard. It would be interesting to see the difference in magazine feed lips between the rifles. It would be also cool to see if the HK can maintain the "no bounce" over a range of ammo types. It would also be interesting to know what gas setting the Sig was using.
 

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Its far from meaningless in semiauto; it does add additional wear and tear, especially if the bounce is hard enough that the ejector is moving the cartridge in the chamber. It also opens another venue for debris to jam things up during that split second.
And your proof of this is?
 

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Discussion Starter #8
And your proof of this is?
Res ipsa loquitur,
additional load cycle on the extractor
additional wear on the chamber from sliding brass
additionally, if the bounce is big enough to have an affect on the disconnector (such as is the problem with full auto fire), then the gap is large enough to allow debris to do the same. A good reason for a forward assist.
as I said, Res ipsa loquitur,
 

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Res ipsa loquitur,
additional load cycle on the extractor
additional wear on the chamber from sliding brass
additionally, if the bounce is big enough to have an affect on the disconnector (such as is the problem with full auto fire), then the gap is large enough to allow debris to do the same. A good reason for a forward assist.
as I said, Res ipsa loquitur,
So you have no proof, only what you "suspect" without empirical data.

Clue #1= Bolt bounce in "normal"* working systems doesn't move the carrier far enough to cause the bolt itself to move at all. Thusly throwing your guessing about extractor wear, and "chamber wear", etc. right out the window...... ESPECIALLY the part about "sliding brass"......do you realize just how far a bolt would have to bounce to unlock the bolt and cause the brass to "slide" in and out of the chamber again????? I mean seriously, how much experience do you have with firarms to think that this would even remotely be an issue?

As to your contention that bolt bounce "allows" forign debris to enter the system and thusly cause malfunctions, once again, this is merely the product of a fertile imagination. Do you realize exactly how fast this process takes place? Do you not understand that if there was that much debris airborn and able to enter the ejection port during the cycle of the firearm that the amount that would enter duing "bolt bounce" is insignificant compared to the debris that would enter during the cycle of the bolt? Crap! Can't fire the gun at all now....stuff might fall inside while it's cycling!!!!

The part that REALLY gets me is your idea that the disconnector is somehow involved in this.

As it were, the issue with FA fire and "bolt bounce" is the hammer dropping when the carrier is at the apex of the "bounce" and the hammer is hitting the carrier instead of the firing pin and riding it forward thus causing a light primer strike and not igniting the round.

*by "normal" I mean that in order to make "bolt bounce" bad enough that it causes the actual bolt to move, one would need to modify the buffer substantially outside of the specifications of the weapon.

Sigh....Seriously dude, you're way out of your league.
 

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Discussion Starter #10
So you have no proof, only what you "suspect" without empirical data.

Clue #1= Bolt bounce in "normal"* working systems doesn't move the carrier far enough to cause the bolt itself to move at all. Thusly throwing your guessing about extractor wear, and "chamber wear", etc. right out the window...... ESPECIALLY the part about "sliding brass"......do you realize just how far a bolt would have to bounce to unlock the bolt and cause the brass to "slide" in and out of the chamber again????? I mean seriously, how much experience do you have with firarms to think that this would even remotely be an issue?
Enough "experience" to qualify the initial statement with the following " if the bounce is hard enough that the ejector is moving the cartridge in the chamber" But just to be absolutely clear, YOU are saying there is no breach face movement from bounce in that Sig?


As to your contention that bolt bounce "allows" forign debris to enter the system and thusly cause malfunctions, once again, this is merely the product of a fertile imagination. Do you realize exactly how fast this process takes place? Do you not understand that if there was that much debris airborn and able to enter the ejection port during the cycle of the firearm that the amount that would enter duing "bolt bounce" is insignificant compared to the debris that would enter during the cycle of the bolt? Crap! Can't fire the gun at all now....stuff might fall inside while it's cycling!!!!
I will hold you to your own standard and quote you: "And your proof of this is? "
But it does seem a little strange that you will acknowledge that a spent case can fly back into an over gassed gun, but some how you cannot envision debris entering during a bounce? Did you consider that the bounce itself might be enough to loosen debris on the bolt, or do you only shoot safe queen clean guns?


The part that REALLY gets me is your idea that the disconnector is somehow involved in this.

As it were, the issue with FA fire and "bolt bounce" is the hammer dropping when the carrier is at the apex of the "bounce" and the hammer is hitting the carrier instead of the firing pin and riding it forward thus causing a light primer strike and not igniting the round.

*by "normal" I mean that in order to make "bolt bounce" bad enough that it causes the actual bolt to move, one would need to modify the buffer substantially outside of the specifications of the weapon.
I apologize if my sentence structure is somehow interfering with your reading comprehension, but I did qualify the statement with an "if"- "IF the bounce is big enough to have an affect on the disconnector" But just to be clear, I don't claim expertise with any of the three weapons above. I would also point out that it would be more courteous and helpful to politely point out that based on your experience that the above weapons are incapable of experience that level of bounce during full auto fire -ie something like "even considering the harmonics, such level of bounce is extremely unlikely in these actions" and maybe quantifying your qualitative analysis. But just to be clear, are you saying that full auto weapons never have enough bolt bounce to engage a disconnector?

Sigh....Seriously dude, you're way out of your league.
Funny, I didn't know there was a competition; heck, I'm even more surprised you have a league. Are your league shirts brown, or just black and tan?
I guess I have learned something, were not all here with the primary priority to help each other out.
 

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Enough "experience" to qualify the initial statement with the following " if the bounce is hard enough that the ejector is moving the cartridge in the chamber" But just to be absolutely clear, YOU are saying there is no breach face movement from bounce in that Sig?
Yup.

The bolt cam pin channel has a fair bit of straight forward/rearward movement when in battery. Matter of fact I have a AR BCG in my hands right this very moment and can tell you that there is easily 1/4 an inch of movement. The "bolt bounce" in the video was not 1/4 of an inch, much less over that amount.




I will hold you to your own standard and quote you: "And your proof of this is? "
But it does seem a little strange that you will acknowledge that a spent case can fly back into an over gassed gun, but some how you cannot envision debris entering during a bounce? Did you consider that the bounce itself might be enough to loosen debris on the bolt, or do you only shoot safe queen clean guns?
Ah....I love it when people argue like my ex wife. All fluff and no substance.

So, how many guns have you had exhibit the issues that you claim, including having debris enter the action during "bolt bounce"?

I'd venture none.

And i'll fully admit that the only time I ever had airborne debris enter the action of amy rifle I owned was either at a training session when we were doing stress fire courses of fire (including having other students throw stuff at the shooter in an attempt to distract them) or while shooting prone next to people with muzzle brakes that were throwing debris to the rear of the line.

So, once again, how many failures have YOU had that you could scientifically attribute to "bolt bounce"? I've had NONE. Hell, i've had mud in the internals of my M4 AND a Beretta 92Fs and neither one malfucntioned during one particular training session where the weather was "non-compliant". Still have pics taken afterwards. After rain had washed most of the mud off as well.

My proof is personal experience of shooting under adverse conditions and close to 17 years of experience with the type of weapons platforms being discussed, and not a single time during that timeframe has "bolt bounce" ever been an issue in a properly built rifle using unmodified parts.




I apologize if my sentence structure is somehow interfering with your reading comprehension, but I did qualify the statement with an "if"- "IF the bounce is big enough to have an affect on the disconnector" But just to be clear, I don't claim expertise with any of the three weapons above. I would also point out that it would be more courteous and helpful to politely point out that based on your experience that the above weapons are incapable of experience that level of bounce during full auto fire -ie something like "even considering the harmonics, such level of bounce is extremely unlikely in these actions" and maybe quantifying your qualitative analysis. But just to be clear, are you saying that full auto weapons never have enough bolt bounce to engage a disconnector?
Yup. That's what i'm saying. That unmodified AR15/M16 type weapons do not EVER experience enough "bolt bounce" to push the hammer far enough back to engage the dissconnector. Either in full auto or semi-auto. Do you even know how far that would be?

So it appears that you are arguing a point that you just admitted to not knowing anything about based on your incorrect assumptions and interpretations of the laws of physics in relation to the topic at hand. Why?



Funny, I didn't know there was a competition; heck, I'm even more surprised you have a league. Are your league shirts brown, or just black and tan?
I guess I have learned something, were not all here with the primary priority to help each other out.
Typical fallback response when you have willfully wandered out of your lane of knowledge.

If you honestly believed your last statement, you would have entered into this topic by asking questions, not by making incorrect statements and trying to justify them as fact when you don't have any experience or even a base knowledge of the system being discussed to even understand what it is you are talking about.

As it were, you are correct, at least as far as i'm concerned, that the point of such sites is to gain or pass on knowledge. Factual knowledge, not supposition or assumption. Remember that and these conversations will be easier for you.
 

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Discussion Starter #12
You would have entered into this topic by asking questions, not by making incorrect statements and trying to justify them as fact when you don't have any experience or even a base knowledge of the system being discussed to even understand what it is you are talking about.

As it were, you are correct, at least as far as i'm concerned, that the point of such sites is to gain or pass on knowledge. Factual knowledge, not supposition or assumption. Remember that and these conversations will be easier for you.
I take it you are talking about your original claim that bolt bounce is "virtually meaniningless" in a semi-auto. In light of our current discussion, what you are saying is that the extra impacts from bolt bounces cause NO additional damage or wear, and that bolt bounces do NOT allow ANY additional opportunity for debris ingress/jamming. That is what you are claiming, right?
 

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the extra impacts from bolt bounces cause NO additional damage or wear
Highly unlikely, and negligible compared to what happens during a normal cycle of operations:

1. Firing
2. Unlocking
3. Extraction
4. Ejecting
5. Cocking
6. Feeding
7. Chambering
8. Locking

bolt bounces do NOT allow ANY additional opportunity for debris ingress/jamming
Compared to when the ejection port is fully open during the cocking phase, it is negligible. If debris entering the weapon during the cycle of operations, or because of bolt bounce, caused the weapon to malfunction (not jam), I would imagine that weapons maufacturers would have developed a different design by now.....most of the debris that gets in to the upper, gets there during reloading. Either through dirty magazines or through debris inside the magazine that sticks on the ammunition.

Also, when you are talking about the hammer engaging the "disconnector" during fully automatic fire, you are actually talking about the full auto sear, right? Because it is physically impossible for the hammer to engage the disconnector during full automatic fire. When the selector is put on full automatic fire, a cam on the selector axle lowers the rear of the disconnector, pushing it out of the way of the disconnector notch on the hammer. If the hammer engages the disconnector, there is something wrong with the triger mechanism, not bolt bounce. As far as bolt bounce causing the hammer to be caught by the sear on the hammer notch.....not plausible, as there would have to be a lot of movement. Actually, it is not possible as long as the trigger is depressed with the selector on fully automatic fire. The hammer notch will not engage the sear.

ETA: With the selector on full auto, there is a 2 cm gap in the ejection port before the hammer engages the sear when I pull the charging handle to the rear. The gap is even bigger, maybe 3,5-4 cm, before the disconnect engages the hammer, with the selector on semi auto.
 

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I think i'm going to leave things to AGR to explain for the most part from now on.

Things that I see as "common sense" and expect people to understand (which some obviously don't), he actually explains better then I can.
 

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Discussion Starter #15
AGR416,
Thanks for the insight.

I took it for granted that the issues were obvious. I could have been more precise in what I wrote; Unfortunately the lack of precision opened up an opportunity to muddy things up. I'll give it another shot

Basically the question is: is bolt bounce "virtually meaniningless" in a semi-auto. From a quantitative standpoint "virtually meaningingless" means that there is ZERO variance in MTBF (mean time between failure) between a weapon with no bolt bounce vs one with bolt bounce. I don't think it is possible to argue that an unnecessary bolt bounce on every cycle doesn't cause unneeded movement, openings, and impact within the firearm, and that those actions MUST cause additional wear and potential for jamming.

Of course, if one does not care that a gun has any additional chance of jamming, or reduced service life then the question is moot because 'virtually meaningless' becomes a personal subjective assessment. People tend spend big money on HK's because those issues are NOT meaningless to them. On the other hand, some people do buy HK's for a perceived snob appeal. From that perspective, the best one can do is claim that such wear,tear and jamming effects are minimal, such as saying the worst case maybe one less round fired over the weapon's life cycle. In that case the question is: what is the value of having that one extra round when you need it? If it is enough to spend $2k more on a MR762 than a Sig716, it ain't so meaningless.
 

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Here's the skinny, no BS, bottom line.

Any extra wear you would experience on account of bolt bounce, would NOT cause an issue in the weapon until long after the barrel has already been shot out several times over and then some. In that time, the bolt will probably have been replaced at least once, and all springs, extractors, ejectors, etc. will have been replaced several times over.

Meaning that the throat and bore will have been worn to the point that it would have been replaced and the whole wear cycle would have started over.

This is why bolt bounce is absolutly meaningless in all aspects to every group that owns firearms, regardless of their reason for owning them. There is no way to measure the effects of bolt bounce because it has that little effect on anything.

You're trying to approach this from an engineering point of view, which strangly enough, I understand. But you're not viewing it from a real world use aspect, nor are you viewing it from the proper life cycle wear aspect of the machine in question.

p.s. for what it's worth, your reference to possible issues created by bolt bounce as "jamming" instead of the proper term, prompts me to believe that you're trying to apply your understanding of machinery in some other aspect to firearms without the necessary experience to back it up. Theoretical vs. real world. Being anal has it's place, just know when to judiciously apply it. Hint: this isn't it.
 

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AGR416,
Thanks for the insight.

I took it for granted that the issues were obvious. I could have been more precise in what I wrote; Unfortunately the lack of precision opened up an opportunity to muddy things up. I'll give it another shot

Basically the question is: is bolt bounce "virtually meaniningless" in a semi-auto. From a quantitative standpoint "virtually meaningingless" means that there is ZERO variance in MTBF (mean time between failure) between a weapon with no bolt bounce vs one with bolt bounce. I don't think it is possible to argue that an unnecessary bolt bounce on every cycle doesn't cause unneeded movement, openings, and impact within the firearm, and that those actions MUST cause additional wear and potential for jamming.

Of course, if one does not care that a gun has any additional chance of jamming, or reduced service life then the question is moot because 'virtually meaningless' becomes a personal subjective assessment. People tend spend big money on HK's because those issues are NOT meaningless to them. On the other hand, some people do buy HK's for a perceived snob appeal. From that perspective, the best one can do is claim that such wear,tear and jamming effects are minimal, such as saying the worst case maybe one less round fired over the weapon's life cycle. In that case the question is: what is the value of having that one extra round when you need it? If it is enough to spend $2k more on a MR762 than a Sig716, it ain't so meaningless.
What possible issues, in regards to wear and malfunctions, do you see arising from bolt bounce and why do they arise? If you could articulate these concerns, rather than "just" a theory that bolt bounce must cause additional wear or increase the likelyhood of malfunctions, it would be easier to address the issue.

For FA, we have already determined that the issue arises when the hammer drops when carrier is moving rearward, striking the carrier instead of the firing pin and riding it home causing light primer strikes, as Grumpy already mentioned.

And if you experience bolt bounce, just switch to a heavier buffer.
 

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Discussion Starter #19
Here's the skinny, no BS, bottom line.
..p.s. for what it's worth, your reference to possible issues created by bolt bounce as "jamming" instead of the proper term, prompts me to believe that you're trying to apply your understanding of machinery in some other aspect to firearms without the necessary experience to back it up. Theoretical vs. real world. Being anal has it's place, just know when to judiciously apply it. Hint: this isn't it.
You are correct experience is helpful, in this case what we are talking about R&M experience. Using the "proper terms" is only helpful if they provide useful meaning to the reader, it wouldn't do much good to start throwing around FMECA terminology, nor would it do much good to use the "proper" German failure mode terms for failures in germanic weapons. But you may find this helpful, what is important in not any individual experience, but rather the population experience; typically a Mean Time Between Failure and a distribution curve describing that population. Its almost the same mistake as thinking firing one shot through a weapon means that it is reliable.

But there is another way to think of it that is even more simple, if the effects bolt bounce in a semiauto were "virtually meaningless" money would not be spent to prevent it.
 

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Discussion Starter #20
Vid of cutaway AR-15 firing:

Cutaway AR-15 - High Speed Video - Preview - YouTube

Extrem bolt bounce, with weights removed from buffer:

AR-15 Extreme Bolt Bounce - High Speed Video - YouTube

Now, if you have bolt bounce like on the bottom vid I can see where you would experience issues.
Thanks for the vids.

As for your earlier question, my main concern is not with the bolt bounce it's rather the bouncing around the cartridge does as it leaves the feedlips on the mag.
Its clear the MR762 is feeding much more smoothly than the other two. That aside, I don't like the bolt bounce for the reasons I mentioned earlier, but what I really wonder is if the MR762 can maintain that no bounce condition over the full range of ammo types.

In that regard, I'm not sure though if it worth the extra $2k to buy a MR762- that is in essence what I am trying to figure out. There is not enough info in the video to determine if there is a bolt bounce difference between the Sig and the HK over the full range of ammo types and gas settings, but it does appear that there is enough info to indicated the feeding on the MR762 is superior.

But if we want to focus on the bounce, and assuming there is some difference between the HK and Sig over a range of ammo, I prefer the one with less bounce.
The areas that I would focus on would be increased opportunity for FOD to enter/jam the action. I actually had walnut media jam a USP9 tight once, was not to happy about that one. Other issues: (1) two impacts on every cycle. On an AR type lockup I'm not totally sure where that impact is -brass, bolt, bolt carrier, etc. (2) additional cycles on any springs involved, and wear on key components. Looking at the first video you posted it would appear that the highest wear point common to bolt bounce in an AR style lockup involves the bolt cam pin; on a Kalashnikov it would probably be on the locking lugs.
 
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