[AGR416]

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.

 

[AGR416]

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.

 

[AGR416]

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.

 

[AGR416]

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.

Well, I think your reasoning is a bit off.

Bolt Bounce is a result of many aspects being off; the gas port is too large, causing a higher cyclic rate than the buffer and spring combination is designed to handle. That is one example of why it happens, ie overgassing. The easiest fix, like I stated, is to add a heavier buffer.

Some manufacturers perform tests to ensure that the system is working smoothly, others just assemble components. And this leads me to another point; how many guns have bolt bounce that is the result of the user building it himself, using the wrong combination of spring and buffer weight for his system?

Here is a vid of a Colt M4 firing in slow motion; no bolt bounce -> a system that has been timed and tested in order to run smoothly.

Hellenic Special Forces M4 carbine in slow motion - YouTube

I'm not saying that bolt bounce is a bonus feature, but it is easy to fix and does not severely impede the function of the system.

 

[AGR416]

I actually had walnut media jam a USP9 tight once, was not to happy about that one.

That tells me nothing. What exactly did the walnut media do to the pistol? Did it prevent the slide from going into battery? Did it prevent cycling after you fired a round? And 'jam' really is not the right phrase, at all.

The areas that I would focus on would be increased opportunity for FOD to enter/jam the action.

This point is moot. I have used many weapon systems over the years, including the HK417, and not just standing on a square range, but in a variety of operational environments (woods, brush, sand/dust, gravel, snow, mud, rain etc). The weapon will not malfunction because of a small gap between the bolt carrier and ejection port allows debris to enter. I can almost guarantee it, 99.9% sure. Weapon systems malfunction for sure, but not because of debris getting into the action because of bolt bounce. When debris is involved, it gets into the action via ammunition or magazines.

(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.

The bolt carrier strikes the face of the barrel extension during locking. The force of the impact from the "bounce" can hardly measure up to the force from the inital impact of the action cycling.

(2) additional cycles on any springs involved, and wear on key components.

The action spring? Hardly a factor considering the level of wear during a normal cycling of the action. In the HK416/Hk417, and civilian equivalents, there is the firing pin spring, but that is hardly a key component of the system. In the M16 FOW there is no firing pin spring.
Extractor spring wear? Hardly likely, as the extractor claw is already gripping the rim of the cartridge. Ejector spring wear? Again, the ejector is not moving, so there is no additional wear compared to a normal extraction and ejection cycle.

Key components? As in the locking lugs of the bolt? There is a vast difference between the forces imparted on the lugs when the weapon fires, compared to the forces imparted during bounce. Cam pin? Again, the minimal movement of the pin as the carrier travels rearwards is nothing compared to what happens during a normal cycling of the action.

Is there some wear over the years and thousands of rounds fired? Maybe. But the wear from this phenomenon is negligible compared to systems running dirty, not lubricated. There are many other causes of malfunctions to worry about than wear or debris in the action, from bolt bounce. The 4 major reasons are; defect magazines, inadequate lubrication, worn parts (mainly extractor) and dirty ammunition.

Also, by your logic, I should not dry fire my weapons, because it leads to excessive wear (reload drills, trigger control etc).....do you advocate that, or is dry firing acceptable?

I think that the issue is exacerbated beacuse of the slow motion film showing an issue you would be hard pressed to notice in full speed. And again, just switch to a heavier buffer if you experience this issue.

 

[AGR416]

I would rather have the gas system dialed in as opposed to just adding extra weight.

Well, I was a bit unspecifc in my reply. It's not just the weight of the buffer that is important, but the internals of the buffer as well, ie how the weight shifts when moving back and forth during cycling of the action.

A heavier buffer with no weight dynamics may cause bolt bounce in a weapon where a lighter buffer with proper weight dynamics does not cause bolt bounce:

AR-15 Buffer Test - High Speed Video - 420 Frames Per Second - YouTube

Carbine buffer: 2.9oz
9mm buffer: 5.5oz
BCM H buffer: 3.8oz

Anyways, it seems that you have made your mind up about the issue, so good luck in finding that wear-free weapon system....

 

[AGR416]

Actually what I want is a weapon that has the highest probability of functioning when I need it; that is one reason why I prefer HK's and Valmets

Buy good ammo and good magazines and you should be good to go....

Don't worry about bolt bounce. I have shot my HK416 hard over the past 4 years, and I have had two malfunctions; first was ammo related, and happened the first week I had it. One single round failure-to-fire, good dimple on the primer. No other issues with same ammo from same lot. Second time was my fault, for not lubing the gun. As in it being bone dry, all parts. A few mags in rapid succession, and the gun started to experience short recoil, and did not chamber a new round. Had to manually chamber new rounds, before I said **** it. Lubed it up, no issues since.

And can you provide documentation of malfunctions occuring from debris entering the action, due to bolt bounce?

Besides, the biggest reason people have, for wanting to eliminate bolt bounce, is to have the smoothest action possible, with as little movement as possible of the parts in order to reduce felt recoil.

 

[AGR416]

That's good info. DI weapons are known for needing lots of lube, might have thought that a piston driven version would be less prone to lube issues. Any idea what the key friction spot was?

No idea. All I know is that lube fixed the issue.....

And like I said before, the M16 FOW is a piston system also. In the M16 FOW the piston is inline with the bore, and part of the bolt. With the HK416/417/MR556/762 the piston is offsett over the bore. The difference is the op rod.

And again, do you any anything conclusive to show that malfunctions do happen because debris gets inside action during bolt bounce?

 

[AGR416]

yes, it is called opportunity; there is also a well known corollary called Murphy's Law.

Well, okay then. I guess you knocked that one out of the park huh? Nothing trumps the scientific opportunity, and the empirical Murphy's Law.

I have tried to help you, and explain it, but you seem to have made up your mind about this.

Good luck with that.

 

[AGR416]

I want to ask you a question about reliability.

If your rifle, after having shot 6000 rounds, experienced the following malfunctions:

Failure of bolt to lock: 2
Failure to fire: 2
Failure to feed (from magazine): 5
Failure to eject: 3
Failure to chamber: 3
Failure to extract: 1
Failure of bolt to lock to the rear: 2
Other malfunctions: 1

Is it reliable in your eyes?

And, not Grumpy, but I would rely on both.

 

[AGR416]

A yes or no would suffice. Although your answer enforces a certain trend when it comes to minutia and irrelevant information.

Anyways, I set the premise for the question, it is not open to interpretation. It is not based on my experience, I have shot way more than 6000 rounds with my gun.

The question is, if you fire 6000 rounds through a weapon, as part of a test, and you experience the failures in the list above, is the weapon reliable or not? This test also encompasses cleaning and lubrication at set intervals.

 

[AGR416]

Are you not able to answer the question in a proper manner? Instead of trying to insult my intelligence by insinuating that I did not understand your post? And none of the data in your reply is neccessary to answer my question.

1 "litter" of water would be quite useless. As for your lame attempt at an analogy, 1 litre of water is not enough, as we sweat, evaporate and urinate about 2,5 litres of liquid pr day during normal activity. Also, you cannot measure a humans effectiveness on how much water he/she needs. Far to many variables than a given standard to test a weapon.

And it is not my weapon.

I am talking about a test to evaluate the reliability of a weapon system, all factors are equal, no what if's, shooter skill level is irrelevant. 6000 rounds, cleaning and lubrication intervals programmed in the testing, failures as specified in tha table above.

Is the weapon reliable enough for, say, general issue to a standing military?

 

[AGR416]

@tktm:

The numbers I used are from the Mil-Spec for the M4A1, MIL-DTL-71186A, with a total of 9 malfunctions allowed from the list above, but not exceeding the maximum limit in each category. I opted to not inform you of the number of failures allowed, as I hoped it would keep you from over-analyzing the issue.

Guess I failed there.

As to the comment about bolt bounce being an aside, lets review your first post:

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.

It does not come across as an aside to me, and when Grumpy made the statement about bolt bounce being virtually meaningless in a semi-automatic, you argued that it caused extra wear, it provided a venue for debris getting inside the action, causing it to "jam" and that it would actually activate the disconnector during fully automatic fire. You then continue to state that you will not dry fire your weapons because of the extra wear.

The only "documentation" you have provided are blanket statements mentioning "opportunity" and "Murphy's Law".

As far as the +p or +p+ comparison, I am not really seeing why it is a valid comparison. Is the PSI increased significantly in a weapon experiencing bolt bounce?

And I find it interesting that you say that we have little grasp that bolt bounce has similar issues to using hotter loads, when you cannot provide proper documentation that it (bolt bounce) affects the weapon system, unless it is a poorly timed system running fully automatic.

 

[AGR416]

What you did was ask a question that was Not well posed; more over what was the purpose of the question? Where you asking if it was reliable enough to protect my family? Where you asking if it was reliable enough to shoot at paper targets? The real question is what were you trying to accomplish? What was the end goal of the question? I give you the benefit of the doubt your asking real questions because you want a real answer; if you are asking questions just to be "tricky", that is a different matter.

A weapons mechanical reliability is measured by how well it manages to go "bang", under a variety of circumstances. There are no other conditions. Was the gist of my question so hard for you to grasp, that you have to add your own conditions to judge wether or not my question is valid? What makes you so entitled?

I asked a simple question in regards to a weapons mechanical reliability. If you need to read something different into it, be my guest.

Unneeded motion, and unneeded openings do cause excess wear and do provide an entry point for debris to jam the mechanism; It is hard to believe that someone would argue that they don't do those things.

I believe we have provided valid information disproving your theory. You are making blanket statements that this happens, "just because you say so". What real world experience do you have to corroborate your position? You have not provided a single piece of evidence, not even an anecdote, describing malfunctions caused by bolt bounce. I cannot find a single problem mentioned at all, except people who experience failure to fire due to the hammer riding the bolt home when firing on fully automatic.

I have shot my weapon covered in dust, snow and in a variety of other austere conditions, no failures to date because of debris in the action at all.

And dude, they are called malfunctions. Jam is something you put on toast.

Moreover, what was said about the disconnector had a big [IF] in front of it.

Well, the post you made pointed to an obvious lack of knowledge of the weapon system, and making assumptions based on that flawed knowledge. If you were familiar with the weapon system at all, you would understand that neither the disconnector (in semi auto) or the sear (in full auto) can engage the trigger in any way because of bolt bounce. A simple test by manually cycling the weapon would have shown it. It is not possible. Also, that you use the incorrect terms does not add credibility to your arguments.

For some of us our weapons are tools to protect our love ones. God forbid we have to use our weapons, but if we do have use our weapons we want them to function with the highest probability of success. People who shoot at paper and don't desire or have the ability to protect loved ones may feel different. As for me, I pay extra for HK because I don't want to compromise my loved ones.

I try to be polite and professional in my replies, but do not ever again patronize me by insinuating that I only shoot paper and thus have no interest making sure my weapon functions reliably. I have carried a weapon as part of my job for 10 years, serving my country. This includes deployment to combat zones. I would say that I am pretty qualified to comment on weapon reliability, based on real world experience in a vast variety of environments. When my life, or the lives of my colleagues/friends, rely on me having a functional weapon, I can assure you that I take care of it. Even if it is an HK.

How much time do you have on the AR platform?

 

[AGR416]

But you have NO capability to actually to determine if bounce actually influenced any failures you may have experienced. The question is how exactly would you know if a failure was influenced by "bounce". What is your detection method?

So you are saying that failures can occur because of bolt bounce, but it cannot be determined if that was the actual cause.

How can you then state that this will cause increased wear and increase the chance of malfunctions due to debris getting in the action, when you claim that there is no way of proving it.....?