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TheFull9

Bolt Bounce in GBB ARs

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I'd imagine fixing this will be pretty similar across GIM platforms, but I might as well mention that I have LM4s.

 

The one I've actually 'finished' (externally) has worked just fine so far, it's a woodland skirmish laser by any means but the rifle and mags are solidly reliable.  However filming the BCG cycling with my phone's slow-mo, there's a fair bit of bounce to the bolt carrier, not the actual nozzle/bolt itself (that seems to stay in battery once it's gone forward).  I think the AGM gun I had years ago was probably doing this, hence why it kept double feeding, with one BB getting caught inbetween the front of the carrier and the chamber/barrel extension, causing a sort of out-of-battery firing that would just vent all the gas in the mag.

 

The only thing I've had mentioned to help lessen the bounce is a buffer unit filled with heavy metal powder to create a dead blow type effect, but since the stock buffer is plastic and weighs nothing I can't help but feel a metal unit with a heavier metal fill is going to use up massively more gas given how much more pressure will be needed to get the BCG moving rearwards.

 

Any thoughts folks?

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Use dead blow buffer and swiss cheese bolt carrier to compensate? Or stick a small, relatively weak spring in the gas key to slow the bolt some before impact.

 

The spring's a good shout, ever tried something along those lines in your own guns?

 

I do have one LM4 carrier that's had a load of material milled out, 'unfortunately' the steel they use is apparently some strong stuff and the guy who did the work got through quite a few mill bits.  Going to be a case of picking up a buffer with floating weights to try and experiment with different weights I think.  Used to have loads of different ones floating around when I had all my WOCs but alas no more.  No idea if the KWA tube accepts common buffers for other systems but I'll have to bite the bullet and find out.

 

If the nozzle is not bouncing but only the bolt carrier, you're probably not gonna get double feeds or any problem.  So really, it's a non-issue

 

In terms of feeding yes, but every extra bounce of the carrier is beating up the system that little bit more.  Not going to be an issue except in the very long term, I just like to fix these things if I can to get the smoothest running possible even if it is basically a non issue for the function of the gun.  Gives me something to do as well.

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Not to an LM4 but I tried putting o-rings as a buffer on an old "closed bolt" WE in an effort to suppress bolt noise and while it worked for that purpose it also killed any bolt bounce. I figured anything to absorb the impact would work similarly be it a spring or o-ring and the LM4 has a convenient hole in the gas key to experiment with.

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Got same issue with my WE AR, I can pull trigger quick enough to release hammer out-of-battery while the bolt bounces....... :(

 

 

I made a make shift buffer with a few weights of different lengths cut from brass stock, tested some combinations and liked the way how long+short works. My theory is that you'll want a bigger one as primary damper and a smaller one to serve as bigger one's damper, while still leaving enough room to let them bounce back.

 

 

...... and yes, this does slow cycle quite a bit but still bearable

 

j3dN9Uy.jpg

 

 

 

This is how it works I believe...

 

 

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Had a number of WE 416 had bolt bounce, but not so much the WE M4s or WE M16s. 

 

The thing is, bolt bounce occurs because of a few factors:

- Heavy barrel

- Light spring + heavy bolt

- Too quick return (quick cycling buffer with extra spring)

- High gas pressure causing quick cycling.

 

This video explains it:

 

https://www.youtube.com/watch?v=8boc8aFgfT8&t=94s

 

Its all about the tuning.  Most stock GBBs don't have problems but some do out of the box.  WE 416s do, however there are also other guns which also has issues, such as the VFC MP5, VFC M4s.  

 

Most bolt bounce I have seen caused a light strike instance where it wouldn't fire auto.  However, I had a VFC 417 with an instance where the bolt bounce did cause it to feed 2 rounds in hot weather.  I removed the extra heavy spring at the end of the stock buffer and that solved the issue. 

 

You can buy airsoft anti-bounce buffers for under $15 USD, or make your own with a few brass weights as above.  I actually make mine on my AR15s converting stock carbine buffers to have extra brass and lead weights.

 

WE M4s have a lot of issues as their system is very inefficient, and can be made to use a lot less gas for each round.

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You can buy airsoft anti-bounce buffers for under $15 USD, or make your own with a few brass weights as above.  I actually make mine on my AR15s converting stock carbine buffers to have extra brass and lead weights.

 

There a specific brand/item you'd recommend?

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I bought this a while back:

 

https://www.uncompany.com/pageproductdetails.asp?prodid=25351

 

Thing is, with the WE M4 systems, to make the system a lot more efficient and recoil better, the mods required are:

 

- Remove the brass roller at the top of the bolt carrier, that allows the bolt carrier to cycle properly with a winter spring

- Use a winter spring (even in summer)

- Anti-bounce buffer

- Trim the flute valve spring by 1 1/2 rungs.

 

This will minimise bolt bounce, but also increase efficiency of the gas use, and increasing recoil.   

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