Pulse Rifle Ammo Counter Help

[thatoneguy04]

Hello all!

Long time lurker, one time poster (so far) and was looking for some help with a Pulse Rifle ammo counter.

Let's start with some background:
I decided to finally build a dream - A live fire M41A Pulse Rifle. My base is a Kahr Thompson M1A1 and an old Remington 870. I managed to fasten the two firearms together using some techniques I found the original prop makers used and utilized the shrouds and parts from my Snow Wolf/ Matrix Pulse Rifle to fully realize the project. I would have loved to use some HGC metal shrouds but those have skyrocketed in price in recent years and are about as rare as hen's teeth. Both firearms have been fully registered as an SBR and SBS per NFA laws.

Now for my question I put out to all of you lovely folks out there. I am in need of some help sourcing a new ammo counter for this build. I currently have the old Snow Wolf ammo counter hooked up to a 7.4 lipo and original switches so it displays "0" when the mag is out and "95" with the mag in but for obvious reasons I can't use the old light gate tech for counting rounds being fired. My plan is to use a shock sensor to register each shot being fired but I need help finding someone who can make a counter that will display only 20 rounds and will only register in semi auto mode and be compatible with the housing's micro switch for the magazine. All current boards I've seen all have only full auto capability. I have so far reached out to a couple of live fire builders and Majenko Technologies but I have not gotten any further sourcing out a board.

If anyone could help point me in a good direction I would greatly appreciate it!

 

[incrediblefruit]

Really wish I could help you because that is a lovely thing...

 

[joberg]

^^
What he said exactly Not a lot of life-fire Pulse rifle in the wild

 

[Xhiwar]

Hi there!
I do have some info here on how I did it on my Pulse Rifle:

The slowest Pulse Rifle WIP ever! (pic heavy)

Keep in mind mine is not a live fire version, so I have no idea whether this will work on yours as well. Most likely not that well directly next to the chamber... But maybe there‘s another place where you could put a switch.

Cheers!
Roman

 

[thatoneguy04]

Thank you all for the replies! I did get into contact with Majenko Industries and he got me a counter out to me so I'll update when I get it all put in!

 

[thatoneguy04]

Alright so I got the new counter in and it works fantastic. The only issue now is the counter comes with 2 wires that when the circuit is complete, it will count down 1 round. I am trying the figure out the best way for the system to detect the recoil of the rifle. I have tried 2 different types of shock switch, both spring type switches and they have not been able to contact property to get the counter to count down. Any one have any thoughts on what kind of switch to use and where I could mount it in or around a thompson?

Thanks in advance!

 

[neophyl]

Wonder if a magnetic pickup could detect the moving bolt ?

 

[laellee]

Wonder if a magnetic pickup could detect the moving bolt ?

I would think a magnetic reed switch could be the way to go if you could spot a small neodymium on the bottom of/around the charging handle between the handle and the shroud? a 2mmx5mm round magnet would be plenty, and will register on a glass-capsule reed switch from a 1/4 inch or so.
I used this method to light an 'energy cylinder' on a revolver design, it let me mount both the reed switch and the magnet behind the mating surfaces of the plastic parts so there was nothing visible at the contact point.

Alternately, maybe just a simple limit switch at the back of the bolt travel somewhere out of the way? I am a huge fan of hiding it completely, but a thin 2mm strip off the switch could be bent/positioned wherever to trigger the cycle. There are also those limit switches with a tiny roller on the end to keep from marring any surfaces.

 

[thatoneguy04]

We are going to attempt a reed switch solution today. I'll post some pictures if it all works out this time!

 

[laellee]

If you go with the glass-enclased, they are more durable than they look but will break pretty easily. I floated mine in with thin shipping foam wrap (like what they would wrap a zippo in) just for extra security. I broke more while soldering and building harnesses than I ever did after install