How can a BCG change recoil impulse?

[me2hootyhoo]

I have one particular bcg that causes a noticeably sharp increase in felt recoil in my rifles. I do not want to name the manufacturer, I just want to understand why. I have compared different bcg’s and the only obvious difference I can see is they all seem to have a slightly different cam path. It is nickel boron from a respected manufacturer. Manufacturer does not have an answer.

[MorphCross]

Is the difference in your perception of the recoil uniform when using this BCG on all of your rifles?

Have you tried a different bolt in the carrier?

I would be curious as well what certain SME/Industry Pro's make of your situation...

[me2hootyhoo]

Is the difference in your perception of the recoil uniform when using this BCG on all of your rifles?

Have you tried a different bolt in the carrier?

I would be curious as well what certain SME/Industry Pro's make of your situation...

Yes, guns that run smooth, run like a jack hammer with this particular bcg.

I have not swapped the bolt only, just the complete bcg.

Manufacturer claims headspace issues can not cause this.

[Mjolnir]

I have one particular bcg that causes a noticeably sharp increase in felt recoil in my rifles. I do not want to name the manufacturer, I just want to understand why. I have compared different bcg’s and the only obvious difference I can see is they all seem to have a slightly different cam path. It is nickel boron from a respected manufacturer. Manufacturer does not have an answer.

That “slightly different cam path” makes a much more than slight difference.

The “more aggressive” the path the more “perceived violent” the bolt will lock & unlock. And it IS/WILL BE more violent.



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[me2hootyhoo]

That “slightly different cam path” makes a much more than slight difference.

The “more aggressive” the path the more “perceived violent” the bolt will lock & unlock. And it IS/WILL BE more violent.



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The interesting thing I noticed, was when comparing 4 different bcg’s, all appear to have slightly different cam paths. What I did was pull the bolt out until it starts to turn. At that point, without using anything to measure, I could see all four were at different lengths extended from the carrier.

Now when you say more aggressive, does that mean the cam pin turns almost immediately or one that can go strait longer the turn more abruptly? I have a good amount of bcg’s floating around and it’s interesting to see and feel the differences when comparing them.

[Gunfixr]

Interesting

[hotrodder636]

I don’t know that I would have equated difference in cam path to change in felt recoil. Interested to find put the learnings on this one.

[Stickman]

At that point, without using anything to measure, I could see all four were at different lengths extended from the carrier.

I’m going to assume, and I know what that gets me, that the worst recoil is with the farthest extended? The other option would be least extended, but I think that would be creating other issues.

[Mjolnir]

The interesting thing I noticed, was when comparing 4 different bcg’s, all appear to have slightly different cam paths. What I did was pull the bolt out until it starts to turn. At that point, without using anything to measure, I could see all four were at different lengths extended from the carrier.

Now when you say more aggressive, does that mean the cam pin turns almost immediately or one that can go strait longer the turn more abruptly? I have a good amount of bcg’s floating around and it’s interesting to see and feel the differences when comparing them.

The one that has the more aggressively (makes the complete turn in the shortest linear path) would be the most violent.


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[me2hootyhoo]

I’m going to assume, and I know what that gets me, that the worst recoil is with the farthest extended? The other option would be least extended, but I think that would be creating other issues.

Yes, I believe you are correct, it is the one that extends the most. It is noticeable, the rest are fairly close.

[me2hootyhoo]

I’m going to assume, and I know what that gets me, that the worst recoil is with the farthest extended? The other option would be least extended, but I think that would be creating other issues.

Okay, so I/we were wrong. One stood out as being the least extended at the point where it starts to engage the cam path.
https://i1119.photobucket.com/albums/k634/heyyoustoopid/2DA4B3FC-A4C2-4942-AED7-8E04495B674E_zpspvd9i7xz.jpeg (https://s1119.photobucket.com/user/heyyoustoopid/media/2DA4B3FC-A4C2-4942-AED7-8E04495B674E_zpspvd9i7xz.jpeg.html)

[me2hootyhoo]

I wrote down two numbers for the TC bcg due to it seeming to hit a bump in the road to say, it was hard to get a measurement on that one. To get the most reliable measurement, I twisted the bolt as hard as I could while pulling outward to get it to hit the face of the cam path. The RTB, Stag, DD and SOLGW were very easy to get that feel and measurement. The TC was difficult, but was noticeably shorter distance to hit that cam path. I did measure many more of the bcg parts, all other parts measured nearly identical to the 1 1/thousandths of an inch.


Okay, so I/we were wrong. One stood out as being the least extended at the point where it starts to engage the cam path.
https://i1119.photobucket.com/albums/k634/heyyoustoopid/2DA4B3FC-A4C2-4942-AED7-8E04495B674E_zpspvd9i7xz.jpeg (https://s1119.photobucket.com/user/heyyoustoopid/media/2DA4B3FC-A4C2-4942-AED7-8E04495B674E_zpspvd9i7xz.jpeg.html)

[Uni-Vibe]

How interesting! I learn much from M4C. makes sense; steep cam path means inertia is overcome quicker.

[formula11]

So the TC gave the most perceived recoil?

[markm]

It is nickel boron from a respected manufacturer.

NiB and respected manufacturer don't really go hand in hand. :confused:

[rjacobs]

NiB and respected manufacturer don't really go hand in hand. :confused:

AAC NiB bolts/carriers are pretty damn good... although they supposedly machine the parts to account for the thickness of the NiB vs. parkerizing, where as most simply throw the coating on and let it ride.

[me2hootyhoo]

So the TC gave the most perceived recoil?

Yes, it is quite noticeable, to the point I thought there was something wrong with the gun. It was in a BCM 14.5 mid with their pin and welded comp/flash hider. I was ready to have the muzzle device replaced due the abnormal recoil impulse, it was the only thing I could think of. Then by chance I swapped bcg's with another AR. Magically the BCM ran butter smooth like they are rumored to be, and the DD that I put the TC bcg then had that same sharp recoil impulse.

[me2hootyhoo]

NiB and respected manufacturer don't really go hand in hand. :confused:

Yeah, not too impressed with NiB in general, but had to try it. TC has to at least have a decent bcg. The phosphate TC compared to the DD bcg, yeah the DD seems a few notches up in quality vs TC. My PSA TC bcg is rough, I also have a Core15 that appears to be a TC and is nicer than the PSA but still not as solid and tight as DD/microbest.

[npena84]

Anecdotally I feel my recoil impulse changed after installing Sprinco ejector, and extractor springs. Could be the extra oomph, of spitting the brass out.

[me2hootyhoo]

Anecdotally I feel my recoil impulse changed after installing Sprinco ejector, and extractor springs. Could be the extra oomph, of spitting the brass out.

I run Sprinco 5 coil extractor springs and have not noticed a difference.

[markm]

Why on earth are you boys installing strange aftermarket springs into your bolts? You're getting me cranky on my Saturday morning.

[me2hootyhoo]

Why on earth are you boys installing strange aftermarket springs into your bolts? You're getting me cranky on my Saturday morning.

Is it strange and aftermarket if manufacturers are using these parts?

http://www.defensereview.com/the-big-m4-myth-fouling-caused-by-the-direct-impingement-gas-system-makes-the-m4-unreliable/

[AndyLate]

Is it strange and aftermarket if manufacturers are using these parts?

http://www.defensereview.com/the-big-m4-myth-fouling-caused-by-the-direct-impingement-gas-system-makes-the-m4-unreliable/

I know Sionics uses the Sprinco extractor springs, and IG recommends them, along with Colt copper washed and BCM enhanced springs.

Npena84, I would never have thought of extractor springs affecting felt recoil - are you pulling our collective legs? :)

[me2hootyhoo]

I know Sionics uses the Sprinco extractor springs, and IG recommends them, along with Colt copper washed and BCM enhanced springs.

I would never have thought of extractor springs affecting felt recoil - are you pulling our collective legs? :)

I'm not too sure I believe an extractor spring changes recoil, but anything is possible and I won't argue or bet against it. So, yeah, if IG and Sionics run em, I will too. Just ordered 6 more last night actually. I run Sprinco extractor springs and Tubb buffer springs all around just for the reliability and longevity.

[Vegasshooter]

I’m surprised it has taken 3 pages to get an explanation on how the recoil is affected by the bolt/BCG. It all has to do with the timing of when the cam path is allowing the gun to unlock, and come out of battery. The LMT Enhanced BCG alters the cam path to keep the rifle locked up a nanosecond longer. By staying locked up that longer time, the pressure curve is altered. That causes the pressure from the round firing to drop quite a bit. By the time the gun unlocks, the pressure has dropped quite a bit. This will absolutely cause the gun to feel lighter in the recoil. It will also be easier on your brass, reduce the chances of a case head srperation, and allow parts to last longer. I’m not trying to sound like an advertisement for any particular brand, because I don’t even use them. I shoot all stock sandcutter BCG from KAC.
The logic is there, and the pressure spike being lower at unlock makes perfect sense. I just haven’t felt a need since KAC are by far the softest guns I’ve ever shot.
SureFire JUST released their new BCG that, among other things, does exactly this. The cam path is altered to stay locked up longer.

If this did get answered in the prior pages, I apologize. I didn’t catch it. It’s Sunday morning, and I got cheated an hour of beauty sleep last night.

[C1-2DG]

I’m surprised it has taken 3 pages to get an explanation on how the recoil is affected by the bolt/BCG. It all has to do with the timing of when the cam path is allowing the gun to unlock, and come out of battery. The LMT Enhanced BCG alters the cam path to keep the rifle locked up a nanosecond longer. By staying locked up that longer time, the pressure curve is altered. That causes the pressure from the round firing to drop quite a bit. By the time the gun unlocks, the pressure has dropped quite a bit. This will absolutely cause the gun to feel lighter in the recoil. It will also be easier on your brass, reduce the chances of a case head srperation, and allow parts to last longer. I’m not trying to sound like an advertisement for any particular brand, because I don’t even use them. I shoot all stock sandcutter BCG from KAC.
The logic is there, and the pressure spike being lower at unlock makes perfect sense. I just haven’t felt a need since KAC are by far the softest guns I’ve ever shot.
SureFire JUST released their new BCG that, among other things, does exactly this. The cam path is altered to stay locked up longer.

If this did get answered in the prior pages, I apologize. I didn’t catch it. It’s Sunday morning, and I got cheated an hour of beauty sleep last night.

This man is right on the money. Beat me to the reply.

Elongated cam pin slots (actual term) are valuable for configurations outside of what the gun was originally meant to be, such as 10" 5.56s, and even large frame gas guns shooting hotter 7.62 or .260/6.5

To a point, longer dwell time and case contraction is a thing.

S/F