Taming the recoil - tactical light idea

So, I was pondering what to do about adding a light to my Rem 870 home defence shotgun when I came up with this idea: use a SureFire G3L, put a dummy spacer in there that locks itself into the battery tube, then put two CR123A cells behind it. No need for a shock-proof bezel since the battery stack will not be slamming into the back of the LED module. Anyone see any flaws in my reasoning? I have a miniature mill at my disposal so I can probably make this spacer on my own.

Interesting idea. How do you plan on locking the spacer in place?

Solscud007 said:

Interesting idea. How do you plan on locking the spacer in place?

Click to expand...

If he doesn't play on using the G3L in rain I'd suggest drilling a small hole, tap it, then stuff a polymer set screw in, although an internal short will always be an issue since the battery uses the internal sleeve to conduct electricity

There are two reasons why SureFire WeaponLights have a retaining feature in the neck - firstly to prevent batteries from slamming into the Lamp Assembly and damaging the incandescent bulb, and secondly to prevent the batteries from being able to slam into the Lamp Assembly reducing the damage they cause to each other in the process.

Whilst using an LED instead of an incandescent bulb negates the need for a shock isolated bezel on a SureFire LED WeaponLight, using a handheld light still allows the batteries the move and crush contacts under the forces of recoil.

I suggest that for home defence you can keep a fresh set of SF123As in the light just in case you ever need to use your shotgun for home defence. If you shoot your shotgun you can use a second set of SF123A's that you would monitor for signs of crushing when you clean your shotgun and prepare it for home defence duty.

The thought was to make an expanding sleeve out of Delrin using the locking bolt as the contact. My original plan was to use a G2, complete with Nitrolon head, with something like a Malkoff M30 or some other single-cell LED module. Since it is only one cell it will not be an issue of having it get crushed under recoil. The heat dissipation should not be an issue, neither, since this is a "bump-in-the-night" weapon that will almost never get taken out and when it does it's just to go to the range to function test both the weapon and the handler. The light will rarely ever be turned on and when it is will rarely be turned on for more than a few seconds at a time (function test, mainly). Why not just buy an actual tactical flashlight instead of cobbling this up? Cost.

Please allow me to back up a moment and give some background on this idea. I have a G3 currently with the Dereelight 1SD module in it and a spacer in it to run one SF123A cell. It's my current BITN light and I had thought about mounting it to the 870. My friend has a SureFire 6P that I'm trying to convince to try an LED dropin with. I then thought that, if I buy a G2L, I could give the LED module to my friend (it's important that it be a SF product since he is weird that way), swap bezels between the two G lights, put the 1SD module into the G2, put a Malkoff M60 module in the G3 and run it on 2X17500s as a replacement for my aging MagLites.

As a second thought. The amount of shots you would need to fire to damage it might far exceed the shots you actually fire.

Why work hard when you didn't need to. Then again, I'm not an expert on what one or 100000 shots would do

I don't know flashlights on guns very well, so let me summarize my understanding:

The back of the battery cylinder has a spring already, the front does not. A shotgun will try to ram the batteries through the front of the light as the weapon is suddenly pressed backwards.

A battery-shaped shock absorber, possibly just a spring in a cylinder, seems like your best answer, rather than a fixed cushion. That'd keep the batteries from suddenly hitting the front, without drilling your light. Also the same setup could be used in any such battery replacement?

Springs are not strong enough to hold the batteries in place. Take a standard 6P/G2 style light. the 2x 123 are held in place by the tailcap spring and the P60 lamp spring. that is it. the recoil from the gun will cause the batteries to move due to the low tension of the springs.

weaponlight bodies have a collar machined into the body. only the first cell's button top pokes thru. So now the rest of the battery top is pressed against a collar and has no where to move forward.

However after looking at a simple Surefire Scoutlight, there is no collar. As Size15's mentioned, LEDs do not need shock absorbtion. However if you look at any e-series light, the lamp assembly and the LED heads do not use springs at all.

So in a sense the batteries are pressed up against a wall. the tail cap end also has a collar. the batteries cannot be removed from the tail end of the light. the batteries' movments have been isolated.

Try to emulate the weaponlight body style or an eseries light.

AnAppleSnail, you've pretty much nailed it except that there is a spring on the back of the LA as well as the tail cap spring. The batteries are held in suspension between these two springs. Upon recoil the batteries will try to move forwards into the LA, crushing the forward spring and decompressing the rear spring. In a worst case scenario the rear spring loses contact with the rear battery or the two batteries separate, losing contact. In either case you lose the light for a split second and some poeple don't like this. It's not a good idea to run multi-mode LAs in weapon-mounted lights because of this.

I had plenty of time to think about this some more on my commute to work yesterday and I came up with a very simple, elegant solution: a Delrin spacer tube held in place with two or three O-rings and a captured sliding aluminum piston inside. The spacer tube is sandwiched between the LA and the battery and the O-rings hold it from moving during recoil. The piston is pressed against the battery positive pole under spring pressure from the LA. This system should not allow the batteries to move due to recoil and the only problem may be that the aluminum piston may move under recoil but if it is light enough it should not move. I'll need to get a G2L before I can prototype this, though.