Gunsmithing Flush Cup Swivels

ptaylor

Sergeant
Full Member
Minuteman
Dec 15, 2003
165
2
central texas
I've got an A5 and love it but it only has the flush cups on the bottom and I would love them on the sides. Can I add them? If so, is this something me or my smith can do or do I need to send to McMillan?
 
Re: Flush Cup Swivels

you can buy them from Brownells in a bag of 10 or 100, fairley cheap, like a buck or less each.

You can do it or your smith can do it. I just plunge with a 1/2" endmill to a depth that lets the cup protrude ever so slightly. FInd some screws that fit the bottom of the cup, make sure your swivels will lock in (that the screw isn't sticking up) and I simply epoxy and screw them into the stock
 
Re: Flush Cup Swivels

I got mine from McMillan but wherever you get them from follow these directions and you'll be good to go.

McMillan Flush Cup Installation

Good thread. Some interesting solutions. Here's the way I would suggest you do it, at least with our cups. The flush cups measure (O.D.) about .557" to .558". Use a 9/16" end mill or drill (.562") and drill a hole about 1/4" deep. This will let the flush cup slide in about 1/2 deep so that it will not chip the gelcoat if you try to screw it in. Then use a 17/32 drill bit and go another 3/8" deeper. This will let the threads "bite" about .015" on both sides. Then swab the inside of the hole with glue of choice, degrease the outside of the flush cup, and start the flush cup into the hole. Use a 1/4" hex wrench to screw in down into the hole until it is flush with the stock. Making the 17/42 hole about 1/8" extra deep leaves room for the glue to puddle up without oozing up into the cup. Using the threads to control the depth lets you put it right where it has to be for the swivel loop to function, and this is the reason we designed the external threaded cup that the old U.M.'s plant makes for us. Too much hassle trying to control the depth with the old smooth or grooved sided cups. Also, our cups are stainless steel to meet mil-spec rusting standards, and then blackened. The standard U.M. cups are carbon steel.
We do so many of these that I have some solid carbide stepped cutters ground on old dull 5/8" cutters that do all this on one pass. You just run it down until the lip of the full 5/8" diameter starts to kiss the stock and you are good to go. If any of you gunsmiths does a lot of these and wants one of the carbide step cutters let me know and I will get a current cost on having one ground for you.
Dick D.

A colleague and I did a couple of stocks and the whole thing took about an hour using a drill press and the required bits, in the end it looked like they were done at the factory.
 
Re: Flush Cup Swivels

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: brazos609</div><div class="ubbcode-body">I thought Grovtec sold the ones with heavy threads on the outside of th ecups but I only see the ones like Uncle Mikes uses. </div></div>

grovtec sells the ones with threaded outside and the hex cut for insertion and/or threading.

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i've used quite a few of them now and they appear to be a quality product. hope this helps. FWIW, the part number you see under them in the first pic is correct to my knowledge...
 
Re: Flush Cup Swivels

If I were going to install the flush cups from Grovetec I would recommend using the stainless steel version.

You won't wear the edges out after lots of repeated uses over time and they won't rust either.

Don't ask me how many "over time" means that is what they told me at their booth yesterday. I'b be more inclined to think that the "wearing" out would be from slowly rusting and corroding due to exposure over time than from repeatedly installing and removing the flush cup swivel.
 
Re: Flush Cup Swivels

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ptaylor</div><div class="ubbcode-body">I've got an A5 and love it but it only has the flush cups on the bottom and I would love them on the sides. <span style="font-weight: bold">Can I add them</span>? If so, is this something me or my smith can do or do I need to send to McMillan? </div></div>

on an A5 it is pretty simple. the forearm area has plenty of "beef" so you can mount them flush without issue. some stocks like the A3 have a pretty narrow forearm and they can be dicey if you don't dial it in just right. it isn't a problem, but you have very little room for error...

also, the pics you see are of a B&C, so the forearm is foam filled and the buttstock is hollow. those require a bit more work, thus you see the allen wrench coated in release agent, taped to hold the insert, and taped into place so the insert won't move while hardening... the manners and macs are much easier to work with in this regard.

hope this helps.
 
Re: Flush Cup Swivels

Awesome guys thanks for the help. Reason I asked, I slung my rifle the other day over my back so I could drag a 150lb pig out of the woods, the bolt handle dug into my back so bad it about ruined my back, I had trouble sleeping for a couple days. Never again, flush cups on the sides are a must.
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Re: Flush Cup Swivels

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Furner</div><div class="ubbcode-body">Ive been looking for the threaded flush cups online, cant find them anyways. Grovtec does not seem to list them anymore. </div></div>

IIRC McMillan has them.
 
Re: Flush Cup Swivels

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: USMCj</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Furner</div><div class="ubbcode-body">Ive been looking for the threaded flush cups online, cant find them anyways. Grovtec does not seem to list them anymore. </div></div>

IIRC McMillan has them. </div></div>

I just shot them an email to see if they have any.
 
Re: Flush Cup Swivels

Grovetec. Buy a 9/16" fine tap and stick them anywhere your heart desires!

I just use a 1/2 drill bit to drill a hole the correct depth, thread the hole with the tap and use some Devcon to make the install permanent.
 
Re: Flush Cup Swivels

You wish you had them on the sides....

I wish I had them on the bottom, the side mount is pretty much useless when you toss a butt-pack on the rifle...