This adapter was never for sale by anyone. It didn't have a part number or picture in the manual that came with the V3 Tac 13.
I had my Tac 13 adapter professionally scanned and had some printed using Nylon 12. A good durable nylon.
The fit is excellent, the texture is not far from the original and matched the Magpul 870 SGA stock quite well. The test gun stock.
I added a 10-24 set screw to the bottom tab to adjust out the small amount of play (in the original as well) and to hold the SGA stock higher in position.
I've run 900 rounds thru the V3 with this adapter installed for testing. Almost all trap rounds at 1 1/8 oz loads, 1200 FPS.
This adapter is locked in place quite well and has no side or top loading to do its job.
Check out the part pics and installed pics using the Magpul SGA 870 stock. Paintable as well so pick your pleasure.

STL?

STL file? What is your question? First item I had professional blue lite scanned. Pricey.

So cool.

How about an overall pic of the whole blaster?

This V3 is set up with a Magpul SGA stock, my nylon 12 printed stock adapter, a 21" smooth bore Hi Viz barrel with chokes. As it comes from Remington.
This barrel is new, un fired, lots of oil. I wanted to show what it comes with.
The Hi Viz front sight, a white lined V rear sight machined into the rib, first post, chokes, and the same non venting gas plugs found on the V3 Tac 13.
This gun will end up being shortened. I don't want to cut this barrel as they are really hard to find, so I will use a 28" camo barrel I have, remove the camo of course. Or maybe not!!!
Overall shot of the V3 Field Sport as it is today.


The gas plugs.


Front and rear sights

This part actually was for sale, but no one in the US had one.

I found a dealer in Canada who had some but they wouldn’t sell or ship it to me - luckily I have friends in Canada.

My TAC-13 came with an adapter that had a mil-spec AR receiver extension screwed into it and a pistol brace attached.

I wanted to put a birdshead grip on it so I needed this adapter.

This is the place where my buddy got it for me:

https://store.gravelagency.com/gaen/f417439-v3-stock-shim-adapter.html

The Remington part number is F417439, it looks like they still have 39 of these in stock.

Yes, the Gravel Agency. I actually called them and because of agreements with Remington, they wouldn't sell to the states.
If you had a friend in Canada, thats your option. and yes, there is now a part number.
I spoke with them maybe two years ago. But now, Remington arms is no longer. Maybe that agreement is no longer valid.
I have no clue if Rem Arms is going to produce the Tac 13 or that adapter. Time will tell.

There was always a part number for that adapter, that’s how I was able to search for it and locate one.

I called JD at AIP Tactical and he looked up the part number for me, this was back in 2022.

Midwest Gun Works has also had this part number listed on their website for a long time, they were the first place I called.

The guy said they hadn’t received any new Remington parts since they filed bankruptcy in 2020 and didn’t know when they’d be getting more.

I have no idea how that shop in Canada ended up with so many of these adapters.

I first got in touch with the Gravel Agency somewhere in 2020. I was chasing down the 18.5 Extra Barrel for the Remington V3, the Tac 13 barrel clamp and gas plugs.
They had the parts but as we know, they won't ship to America.
Don't think the parts are restricted by the US, don't know why they would be because of US manufacture, so I think just a matter of making the connections.
I might just drop them (The Gravel Agency) a line to see if the aggreement with Remington is still valid, since Remington Arms is no longer in business. Now Rem Arms.
If I get a response, I'll post on here.
You still have the buddy up there?