Modify a 4.40" stock to fit a 4.275" action

[DiRTY DOG]

I see very few options to replace my 4.275" receiver tupperware stock. It's a 2005 era model 12 varmint SA blind mag. I'm replacing the barrel with a 20 Practical magnum sporter contour, and replacing the blind mag with a DBM.

But there are some good stocks for 4.40" receivers.

It seems any Bell & Carlson or Boyd's stock simply needs the front receiver screw hole moved back 0.125". (Reduce the distance from 4.40" to 4.275"). Basically drill or grind a new hole through the aluminum bedding block or wood, partially overlaping the old hole. A few minutes with a round file? It doesn't even need to be pretty since the detachable bottom metal covers it up. Atlas makes DBM that fits both 4.275" and 4.400" via an ofset bushing that can be flipped around. A little JB Weld filler in the old hole if needed. I'll probably bed the action with Marine Tex anyways.

Seems very simple. Is there any reason this wouldn't work on Bell & Carlson or Boyd's stock? I've done a lot of searching and I don't see any discussion about this.

[J.Baker]

If it were me I would probably fill in the existing front hole in the stock with JB weld or similar to make it much, much easier to drill the new hole. The screw size is 1/4" so the hole isn't much more than that, and we're only talking moving the hole half of that (1/8") so the tip of your bit would be right on the edge of the old hole and just want to push into the old hole. Or you could just use a course 1/4" rat-tail file to elongate the existing hole rearward.

I've also seen a few people drill out the factory pillar and then make a new one with the hole off-set to move it the required 1/8".

[DiRTY DOG]

Yes, it seems it would be easier to first elongate the old hole with a file. Then fill in the old hole with JB Weld later if necessary, but it wouldn't seem "nesessary" given the remaining surface area of the aluminum bedding block.

[pdog06]

It will work, depending on how it’s currently set up. I have done it on a few stocks.

If it currently has a pillar then I would recommend just opening the hole up and bedding a new pillar in the desired location.

If it is a full bedding block then the hole can just be elongated. Actually did just that on a B&C Medalist a couple months ago. I elongated the front hole since it is an aluminum bedding block and not a single pillar. I could’ve filled in the excess area but chose to leave it so it will fit either screw spacing. The only other thing we did was since it was a larger(longer) hole was we used a small washer with the action screw.

[charlie b]

From what you guys have said it seems all the other locations are marked off the rear screw, ie, recoil lug, bolt handle location, mag opening, etc.

If so, it would open up a lot of options for the different screw spacings. Just about any stock would work with the front screw being relocated?

[DiRTY DOG]

If so, it would open up a lot of options for the different screw spacings. Just about any stock would work with the front screw being relocated?

It seems YES, like pdog06's green B&C stock above. If you can drill a new hole or elongate the old one, you can convert any 4.40" into 4.275" stock. You might need to add a pillar for some stocks, or fill in the old hole (or cover it with a washer) to make it pretty.

Most bottom metals won't work unless you also modify the bottom metal for the new screw location. The Axisworx DBM works because they include a bushing that works with both 4.40" and 4.275".

[pdog06]

That’s correct. Everything else is in the same locations between the 4.4 and 4.275 actions.

The target action with the 3.44” screw spacing is different however. The action itself is the same length but the front and rear screws both have been relocated and allows for a full rear pillar instead of the notched one.

[J.Baker]

Pdog's on point with the info above.

One note I'll make just so someone doesn't mistakenly apply the above thinking to their Gen1 short-action is that the Gen1 actions with the 4.522" screw spacing are 0.310" longer in overall length than the later Gen2 (4.275") and Gen3 (4.40") actions.

[DiRTY DOG]

UPDATE:

I had a 2005 era short action 4.275" Savage 12FV in 223 Remington. I previously bedded the action and bedded an aluminum rod into the forend to stiffen it. It shot great! But I wanted to upgrade the old tupperware stock and add a detachable magazine. There are not very many aftermarket stock options for 4.275" actions.

I decided to try a Bell & Carlson sporter stock for DBM for 4.4" receivers and modify it to fit a 4.275" receiver. All I needed to do was slightly elongate the 4.4" hole in the aluminum bedding block to fit a 4.275" action.

https://www.bellandcarlson.com/index...tegory_ID=1140

I ordered the Atlasworx DBM with a reversable bushing to fit both 4.4" and 4.275" actions. Atlasworx is located in Australia, but shipping to the US was fast arriving in about 10 days.

https://atlasworxs.com/shop/atlaswor...l-10-11-12-sa/




Northland Shooter's Supply shipped me a 24" heavy sporter Criterion prefit in 20 Practical along with a new barrel nut. I already had their action vice and wrench.

[DiRTY DOG]

First I had to bed the receiver into the stock. After that I could set the final depth and position of the DBM to ensure the magazine fed correctly.

I removed the factory barrel with the NSS vice and wrench, and then stripped the action and bolt for Cerekote. I installed the new barrel and set the headspace so the stripped bolt head would just barely close on a go guage.

The barreled action fit poorly in the B&C sporter stock. The heavy sporter barrel was a little too thick for the stock's sporter barrel channel, so I used 80 grit sandpaper on a dowel to remove stock material. I had to remove a lot of material to free float the barrel, mostly depth, especially at the front of the forend. Nasty void in the forend.



Once the barrel was free floated in the barrel channel, I saw that the action was not resting on the internal full length aluminum bedding block. More cutting and sanding was required around the action. And some more dremmel and sanding to free float the tang.

[DiRTY DOG]

I modified the stock's front receiver screw hole. It was positioned for 4.4" screw spacing. I used a drill bit by hand to elongate the hole to fit 4.275" spacing. I should have used a jig, the hole was a little messy, but nobody will see it. Maybe I'll fix it with JB Weld but it seems unnessesary.

Before and after.



After the barreled action sat flush on the aluminum bedding block, it was time to work on the recoil lug. The lug was not touching the aluminum bedding block at all, it had about a 1/8" gap between it's rear face and the aluminum bedding block. I bedded the action and recoil lug with MarineTex without too much difficulty. I've done this a few times before.

[DiRTY DOG]

The B&C stock inlet was slightly too narrow to accept the Atlasworx DBM mag well to fit up inside the stock. I had to remove some of the thickness of the B&C full length aluminum bedding block to make room for the DBM. I eyeballed the dimensions and started removing aluminum.

The best Dremmel bit turned out to be this super aggressive one, which easily removed chips of aluminum.



Before.


After, the shiny metal is where I removed material with the dremmel by hand.


After some careful measuring and test fitting, the DBM inletting looked like this. I removed material slightly higher than necessary in case I had to adjust the magazine height for proper feeding. Maybe I'll bed it in place later, but it fits snug as is so probably not.

[DiRTY DOG]

The only 5-rd 223 AICS magazine I could find was from AccurateMag. They are steel construction, and very high quality, but pricey.



I needed to set the correct DBM depth to ensure the magazine would feed correctly. It sat too deep because the rear pillar was about 1/4" too short to reach the DBM. With a longer rear pillar, and a little bedding material under the trigger guard, the DBM had something to seat against for proper fit and torque.



Starting to fit like a rifle now!


With everything assembled and in place for test functioning, it would not feed from the magazine. The original short action bolt baffle with the extended arm (travel stop) would not allow the bolt to travel back far enough to pick up a round off the detachable magazine. A new short style front baffle was an easy fix, but a problem I overlooked so I had to wait a week for a $5 part to arrive.

With the new stock and DBM assembled, the front action bolt required shortening to 1" and the rear bolt needed lengthening to 1.9". I found the right hex head bolts at ACE Hardware and trimmed a 2" bolt down to 1.9". Both bolt heads were too wide to fit into the DBM so I ground them down to original spec via a hand drill and file. I torqued the front bolt to 35 ft lbs and the rear to 25 ft lbs.



Dummy and live testing showed that feeding was 100% from AICS magazines so far. Everything fits like a glove.

[DiRTY DOG]

Long story short, yes you CAN transform an older 4.275" action into a newer 4.4" stock and add a modern detachable magazine with a little inletting and pillar/bedding work.

[DiRTY DOG]

But does it shoot?

It now has 100 rounds through the new barrel. Groups are looking good but I'd like to reduce the SD/ES hopefully once the brass is fireformed and annealed. 5-rd groups like these are common from a bipod/rear bag.

20 Practical
Criterion 24" 1:11 heavy sporter
B&C sporter stock
Atlasworx DBM & 5-rd AccurateMag
RifleBasix-1
EGW 20moa hunter rail
Leupold Backcountry rings
Leupold VX-5 3-15x44

24gr Hornady NTX
26.0gr - 27.0gr 8208xbr (4100 - 4300 fps)
Starline
cci450
seated 0.020" off the lands

Seems to like 26.0gr the best so far @ 4100 fps, but 4300 fps is enticing for a ground squirrel and rock chuck load.