hi all. I recently thought of a project that would combine both my hobbies, precision rifles and electronics. I have what i think is a great idea however I am not familiar with solenoids enough to know if this will work so i am asking the smart people. I want to develop a system that allow me to practice dry firing drills that are more realistic. the system will track a laser to monitor shot placement. this portion i have under control. but i want to add a solenoid that will re-cock the hammer after each shot. My plan is to source/make a tubular solenoid that will fit in the buffer tube and simulate cycling the bolt. the tube is .975 in diameter and about 9.5 inches long. i need the stroke to be 1.5 to 2 inches. the hammer springs can be up to 5 lbs(aprox. 23) in pull weight which may be tough to do in this small space.. is this possible or is it too small of a space? if so any rough ideas on current required? i dont want it to be unsafe. I have lots of electronics experience but very little with solenoids or EMs.
any input would be much appreciated.

requirements:
max OD: 0.975 inches
max length of coils: around 7 inches( 9.5 total length - 2.5 inches for piston travel and clearence)
stroke: 2 inches
force: 23n or 5lbs(most likely less)

thanks

 

That is asking a lot of a solenoid, but might squeeze in a linear actuator. Just checked gear reduced DC motor & is .8 in dia. a mite slow-2 RPS maybe driving a 6-32 screw, 32 sec. one way. Or as Air-Soft does it- store power in a spring.

 

hi thanks for responding. you have confirmed my fears. Ill check into your ideas. and maybe neumatics as well

 

Speaking of Air Cylinders from Surplus Center, Lincoln NE, USA, Item 4-1726, single acting push with spring
return, 9/16 bore, 2 in. stroke, 250 lb. max air pressure which by my calculation gives 62 lb. 10/32 port on end.
2017 Cat. $ 5.95. Food for thought ??

 

While it is nice to be able to combine two hobbies in this case I really don't see this idea playing out very well. I never gave much thought to the force required on the charging handle but getting a solenoid to do what you want won't be easy considering the force required into the restraints of the space you have to work with. It is an interesting thought for dry firing exercises though.

My own AR 10 is an early Armalite AR 10(T) about maybe 22 years old now. When I started on it the selection was pretty limited. Currently has a 24" free floated Douglas match barrel as seen below with the match sights. The sights are Centra including the front globe.



The sights are Centra including the front globe. While I seldom use them I also have a scope and original open sights from the factory.



My best advice for a dry fire exercise is assume a standing, sitting or kneeling and then a prone position and manually jack the action and squeeze one click at a time working on holding and squeezing one click at a time holding your sight picture & sight alignment as you work on breathing control. If there is a short cut around this I haven't found it in over 40 years.

Anyway, happy shooting and enjoy that range time.

Ron

 

If there is a short cut around this I haven't found it in over 40 years.

Not having an AR-10 but having a few AR-15s are the trigger groups the same or similar? The 15 trigger group is easily removed in one piece, couldn't a separate TG be made with lighter springs for dry fire practice? And then incorporating a solenoid to cock the hammer.

 

What you are describing sounds like the range system they have been using in US Navy boot camp for quite some time. I went through in 2004 and it wasn't quite "new" then. The target down range tracks laser placement at time of fire. A pneumatic solenoid in the gun releases a burst of high pressure air from the muzzle which simulates recoil. They use dummy guns so there is no slide or charging handle to force back.

For your purpose, do you think that 120PSI into a blocked-off barrel is enough to utilize the rifle's own gas blow-back system to force the bolt back? I realize that the muzzle pressure which typically performs this task is much higher than 120psi, but it's also not working with a sealed barrel. Probably won't work but maybe worth a try if you have time. If it works, then an air hose and two solenoid on the gun; one to pressurize the barrel and blow the bolt back, and one to simulate recoil.

Just thinking out loud... Maybe look up the navy boot camp range for inspiration.

Edit:
If you do anything like this, best to use an overkill air dryer and maybe an air tool oiler in line. Otherwise you'll blow water into the gun and infect it with a cancer that won't be easily cured.

 

Not having an AR-10 but having a few AR-15s are the trigger groups the same or similar? The 15 trigger group is easily removed in one piece, couldn't a separate TG be made with lighter springs for dry fire practice? And then incorporating a solenoid to cock the hammer.

The AR 15 trigger group can be a one piece assembled trigger group or consist of all of the parts held in place by the pins. The nice thing about the AR 15 is standardization, you can swap parts around easily. The AR 10 which is sort of like an AR 15 on steroids is another story. You can't for example yank a trigger group out of one and put it in another. Even the magazine designs are varied. My old Armalite above uses a modified M 14 type mag and later versions of the same rifle use a different design.

As to the original post I don't see an easy way to do what they want to do. Good idea but I can't see an easy way to make it happen.

Ron

 

Sorry i haven't been back on to reply i had a big project due for a project management. My goal is to have a system that will allow practice/ simulation with as close to the real rifle as possible. If i change any of the trigger group parts it will not develop the same muscle memory. Blocking the muzzle and using the actual rifles gas system is a good idea as well, I would like the laser to come out of the bore but i may look into this further. Right now im toying with the idea of an air solenoid in place of the buffer assemble. im thinking of making a specialized bolt carrier (i have access and experience with lathes and mills) that would house the laser(directed down the barrel) and either a hook of some kind/ or some strong magnets that will connect pneumatic actuator to bcg / laser housing. this would allow the two to connect when the upper is lowered into place. for the air supply im thinking of running a line thru the hole where the charging handle goes but im not super fond of the idea. IDK may be a waste of time but im a big time tinkerer and i think if could pull this off and incorporate a first person shooter game engine I would probably never leave the house.

 

I would like the laser to come out of the bore but i may look into this further.

They do make LASER Bore Sight Cartridges Sighting range 15 to 100 yards – Recommended distance is 25 yards indoors. Which will tell you how much you shake.

The main problem is always going to be cycling the action in the allotted space you have. Even if you fabricate your own BCG (Bolt Carrier Group). Something which may work and while it will not simulate in detail the actual full recoil energy which the shooter absorbs while holding sight picture and sight alignment would be to operate the gas system as it was designed to operate.

While I have no idea as to the actual gas port pressure on my AR 10 I can say that with a 308 Winchester cartridge (7.62 X 51 NATO) when fired in a M1A or M14 is about 1200 PSI at the barrel gas port. All of which depends on obviously the load, bullet weight, distance to gas port and other variables. Figure also within a time frame of about 1.5 to 2.0 mSec the entire party is over with the bullet exiting the muzzle. From ignition to gas port, again depending on the powder burn rate we are looking at roughly 500 uSec. A typical high pressure nitrogen cylinder has a cahrge pressure between 2200 and 2700 psig. Easily regulated down to 1,000 psig or a pressure of your choosing. Using the existing trigger group and fitting the existing trigger with a small micro-switch (or other type switch) could fire using a pulse, a high pressure solenoid allowing a burst of gas to the rifle's gas system. This would allow the gas system to function as normal and as designed. You would need to fit a modified gas tube system to the rifle but if it works it should not have any effect on the trigger pull force which you want between about 4.5 and 5.0 Lbs with service rifle match being a minimum of 4.5 Lbs. A small charged cylinder should last a thousand shots depending on cylinder size and volume obviously. Bimbo, Asco and Parker Hanafin being among those making the solenoid valves.

This is likely how I would approach doing what you are looking to do. I would think you really don't want top screw with the rifle's internals as you want the action to simulate live fire and cycle as it was designed to function.

Ron