Pine derby tungsten weights as Gentle Recoil System spacer weights? With a little work, we may be able to fit a full weight Gentle Recoil System in a carbine buffer tube!
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Option 1:
Over on Reddit u/the_duck17 alerted me to 1″ tungsten rounds used as pine derby racer weights ($24 each). : https://www.maximum-velocity.com/product/solid-tungsten-round-3-25-ounces/
They’re about 3/8″ thick, meaning 2 of them stacked could replace 1 Kynshot 3/4″ stainless steel spacer weight. Since they’re about 3.2oz. each, two would give 6.4oz. With a carbine-length Kynshot RB5000HP weighing in at 4.8oz, together they would equal 11.2oz. If they fit and functioned, 2 of these weights could be used to make a full-weight Gentle Recoil System (GRS) that fits in a CARBINE tube.
That’s a pretty big deal, since the normal full-weight GRS needs a special extra-long 8.5″ Just Right Carbines buffer tube. A normal carbine tube is 7″.
Now, I know the ID of a buffer tube is about 1″, and these are described as 1″ OD, but I thought it would be worth a try.
Aaaaaaand they don’t fit. Frustruatingly close, but no. They’re the exact same diameter as the inside of the tube, so there’s no room for them to slip in.
– Thickness : 0.405″, 0.407″
– Weight: 3.4oz., 3.4oz.
– OD: 1.000″, 1.005″
It says in the description that they’re cut from a solid tungsten rod, but from the texture it looked to me like they’re sintered. I sent them an email to confirm either way, and the seller replied they ARE sintered.
From the seller: “You are correct they are sintered, sorry for any confusion. We had to change manufacturers to keep cost down. We will make corrections to the site, totally forgot it even said was cut from rod. If they are not what you are wanting you can return them.“
I did the math and they have a density of about 18 g/cc, which also confirms it’s sintered tungsten.
I posted all this on Reddit and got some great suggestions on how to work the disks so that they would fit in a buffer tube.
Since these disks aren’t tungsten-carbide, they can be worked with just Dremel sanding disks. Diamond coated tools are not required (but they do help!)
By spinning the disk with a drill as I work around the edge to remove material, it should give a more even result. But how to you hold a flat disk with a drill chuck?
Per one of the suggestions, I super-glued a roofing nail to the center (I just eyeballed it) and it worked like a charm.
I started using a cordless drill, but soon switched to a variable speed 1/2″ drill ($10 at a thrift store) upside-down in my vice to spin the round while I worked on it with a Dremel and Harbor Freight diamond files. I used a shop vac to catch most of the metal dust as I was working the metal. It took about 3 hours of messing around but once they were done they came out really nice.
Last pic shows them compared to a Kynshot spacer weight. Total height is 0.8″ vs the 0.75 of the Kynshot.
Each weighs 3.2oz., so 6.4 together. Combined with a RB5000HP Kynshot hydraulic buffer, these should make a full weight 11.2oz Gentle Recoil System that fits in a carbine buffer tube.
Despite the fact that they are slightly longer than a Kynshot spacer weight, there is enough room for the LRBHO to activate.
Range testing:
Option 2:
Looking for an option that did not require grinding, Amazon sells tungsten rounds for pine derby racing from Midwest Tungsten Service. These come in a 3-Pack. 1.59oz. each, 0.87″ OD, 0.28″ tall. https://a.co/d/8JayNma
5.0oz. total
0.828 height total
0.867 OD (0.995 is optimal)
Unfortunately, instead of being too wide, these are a little too narrow for a buffer tube (I knew this when I ordered them). I’ll need to figure out a way to keep them from possibly spinning or getting stuck in the tube, and how to keep them centered. They will probably need to be glued together and have a 1/16″ sleeve around the outside, or strips of material added to the outside to keep them centered in the tube. I’ll need to work that out.
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