How I Bed Rifles

Bedding a rifle can drastically improve the performance.  To explain what bedding is, think of a straw being suspended between a salt and pepper shaker (it’s almost dinner time…).  Imagine trying to guide a toothpick through that straw, it will want to bind because the straw is sagging in the center.  Rifle actions have the same problem, when the amount of contact between the stock and the action is small, the torque applied to the action bolts will twist, bend or misshape the action causing accuracy problems and tightness of the bolt.  What you want is a bed that the straw can sit in between the salt and pepper shaker that ensure the straw rests in a relaxed state.

There is a solution to this!  Fortunately, it is not a hard task to bed a rifle action to the stock (create a perfectly matched contour of your action in your stock).  There are LOTS of ways to bed an action to a stock, but I found that the way I do it results in a perfect stress-free bed every time.  I have seen others that use surgical tubing, rubber bands, clamps and even the action screws and bottom metal to tighten the action down to the stock.  All of these methods can (and usually will) induce stress into the setup just as the salt and pepper shaker would the straw.  We are aiming for a 100% relaxed action when it is torqued into the stock.

Prep work is 99% of any gunsmithing job.  The mill will do almost all of the milling work and the lathe will do almost all of the turning work… assuming the operator takes the time to set up the work correctly.  First, I thoroughly clean the action with acetone to remove any oil, grease or debris.  Once the action is perfectly clean I hit it with a coat of Kiwi Neutral Shoe Polish (cheap clear shoe polish).  I apply it with a soft toothbrush over the entire action and the back of the recoil lug, let it dry and buff it with a cotton cloth.  I usually put two coats of wax on the action this way.  I tape off the front and sides of the recoil lug (to provide a small “gap” between the lug and bedding compound, we don’t want it so tight we can’t get the lug in and out of the stock.  I have found that one layer of blue painters tape is sufficient for me and provides a nice clean fit.

Barrel taped and waxed

Barrel taped up and waxed

Next, I lightly sand the existing pads and / or pillars to provide a rough surface for the compound to adhere to.

Stock taped

Stock sanded and taped up

Next, bedding compound is applied to both the stock and the back side of the recoil lug (we want to make sure we have plenty so we don’t get any voids).  As time goes on you get better at judging the correct amount of putty to apply.  I am using Devcon Steel Putty.

Bedding compound applied

Bedding compound applied

I turned the hangers screwed into the bolt holes on the lathe from 5″ hardware store bolts.  I cut off the existing 1/4-20 threads and re-threaded 1/4-28.

Bedding compound applied to recoil lug

Bedding compound applied to recoil lug

Next, the action is carefully lowered into the stock.  NOTE: It is best to leave it alone at this point.  Once the action settles in, resist the urge to take it out or wiggle it around.  The putty will flow over time and make a perfect thin layer without any extra help.  At this point you can wipe any excess off carefully with q-tips.  You can clean any putty off the action with q-tips dipped in WD40 or acetone (do not get any down in the stock though!).

Sitting in putty

Gooped up to cure overnight

I left this overnight and popped it apart the next morning.  A few taps from a small hammer on the 1/4-28 hanger bolts and it popped right apart.

Popped apart

Popped apart

After popping it apart and checking to make sure everything is how you like it, you can carefully trim the top with an exacto knife (trim small strips at a time like you are sharpening a pencil with a knife).  Set the barreled action back in the stock and let it sit at least 24 hours to finish curing before machining.

Once it has finished curing, level the stock in both X and Y in the mill.

Leveling on mill

Leveling in mill

Mill setup

Mill setup

I mill out any excess compound to keep the bedding job looking professional and clean.

Side milled to clean up

Side milled to clean up

Finished milling

Finished milling

After cleanup in the mill, I reassemble the trigger in the action, bolt the action to the stock and mount and boresight the scope.

Completed Job

Completed job

Here is a closeup at the completed bedding job, as seen from the outside.

Completed bedding

Completed bedding

Completed .260

Here are a few pictures of the assembled and completed .260.  I still need to finish the exterior of the barrel, at this point I am thinking a black / green paint scheme with Cerakote.

Completed Gun

Ready for sight in!

I got to the range today (12/02/2012) and shot a few rounds I threw together this morning.  I was mainly wanting to dial in the rifle and fire-form some cases.  I didn’t bother trickle-charging the cases and instead just threw the powder with my Redding BR3 powder measure (34g Varget, Lapua .308 brass necked down).  The rifle shot amazingly, here are a few of the 3-shot groups from 100 yards.

.260 First Targets

Finishing up the .260 machine work

I finally got some time over the Thanksgiving break to finish up the machine work my .260 Remington build.

Dialing in the barrel

I dialed in using the contraption in the posts below, then checked it using a long-reach indicator.  This long-reach indicator is a 1µM B&S test indicator I picked up a while back.  The barrel had less than 1µM of runout (probably around 0.0002 with the long stem) when I finished the process.

Outboard Spider Adjustment

Inboard Spider Adjustment

Tenon and Bolt Nose Recess

After dialing in the barrel, I cut the barrel tenon, threaded the barrel tenon and cut the bolt-nose recess.

Facing the Chamber End

Cutting the Tenon

Testing Recoil Lug Fit

Tenon Threads Cut

Cutting Bolt Nose Recess

Finished Tenon

Ready For Chambering

Chambering

Next, I cut the chamber.  Since I detailed this process in an older post, I’ll just post a few pictures.

Starting The Chamber

Beginning Of Chamber

Still Cutting…

Finished Chamber!

Muzzle Threading

After chambering, I flipped the barrel around and dialed it in again.  This time, to cut the muzzle threads (of course we are shooting suppressed!).

Facing The Crown

5/8-24 Threads Cut

Suppressor Tested (after thread mic)

Making a Thread Protector

Unfortunately, I didn’t get as many pictures of this process as I would have liked.  I did get a few though.  The thread protector is a screw-on cover for muzzle threads to keep them from getting dinged up when a muzzle-device (break / silencer) is not in use.

Drilled and Bored

Threads Started

Threads Completed

Conclusion

If you have made it this far, I am impressed with your attention span!  I am very happy with the machine work on this barrel.  The threads all came out looking very nice and all are class 3 (a “perfect” fit between male and female, not what you get from a hardware store nut and bolt), the machined surfaces are all very smooth (600 rpm and 0.010 cuts) and the bolt drops on the go-gauge and test case with very little pressure.  I hope the rifle shoots as good as it looks!

Building a K&M expander and mandrel

After necking down .308 brass to .260 (with a 7mm-08 in the middle).  The necks need to be neck trimmed to be brought back into the correct dimensions.  There are many commercial neck trimmers available, but I decided to go with the K&M Precision for various reasons a few years back.  Instead of spending too much money to buy a new expander and mandrel, I decided to design and build my own.  I pulled a few dimensional differences from my .308 set and interpolated the numbers to come up with a set for .260 Remington.

I used some 1/2″ oil hardening drill rod for this project.  It was quite tough to get a good finish, but I found that carbide at about 600 rpm / 0.010 finish cut at a moderate feed rate provided a good-enough surface finish.  It doesn’t look too spectacular, but feels very smooth and doesn’t shave the brass when expanding.

Original CAD drawing (Autodesk Inventor)

Turned to initial size (+-.0005)

Expander turned to size (+-0.0005)

5 degree angle turned on expander (using compound)

Hole center drilled, drilled and being tapped, notice the spring center in tailstock

Expander completed and mounted

Mandrel completed and mounted

Newly trimmed case (still needs to be fire-formed though)

Reaming a go-gauge

This project was two-fold: 1) To create a go-gauge to use for my hand loads that measures exactly to my chamber specs and 2) To practice with my chamber reamer before I cut the real chamber.

I started out by dialing in the muzzle-end of my barrel (the waste part) to my normal tedious specifications: 0.0002″ or better (a 1/10,000 indicator barely moves).  Next I marked my reamer at a rough stopping point, oiled it up good with some thick sulfur-based cutting oil and went to town, very very slowly.

First cut

The reaming process produces very short, curly chips and leaves a mirror-like finish.

Chips

Here is my ghetto cutting depth indicator setup.

Depth indicator setup

And finally, the finished chamber (took about an hour to cut).

Finished chamber

Recoil Lug Jig

After opening up my receiver to 1.075″, I needed to open up the recoil lug to match.  Unfortunately, I had no way to accurately hold the recoil lug in the lathe, so I had to create yet another jig.  I think the numbers seem to be working out pretty well… 90% of my machining time is spent building fixtures and jigs and 10% is spent working on guns =)

Here is my initial layout.  All bolt holes were measured very precisely so only part of the washer would overlap.

Initial Layout

Here is a picture after the holes were drilled and tapped.

Drilled and tapped

Here the fixture is dialed into the 4 jaw and indicated to 0.0005″.  I made very light boring cuts to open it up to the exact 1.075″ dimension.

Cutting

And the final product:

Completed product

.260 Remington Build

My first gun build is going to be a .260 Remington.  Here is a list of components I have gathered for the build:

  • Remington 700 ADL (.243)
  • Bartlein 6.5mm barrel, 1/8 twist, 5R rifling
  • AICS 1.5 stock
  • Timney trigger
  • US Optics SN-3 3.2-17×44 T-Pal MIL/MIL with EREK

I completely stripped the receiver of all internals and popped the rifle apart using my barrel vise and an action wrench.

Factory rifle disassembled

Since it seems to be pretty standard to post “before and after” pictures of the threads in the receiver, here is a picture of the threads before doing any work.  The receiver itself is actually in pretty good shape, probably because the original rifle was never shot.

Receiver before work

The reason for truing factory receivers and bolts is to bring all of the surfaces back in to line with the datum through the center of the part.  The receiver abutments and face need to be perfectly perpendicular to the center-line of the action and the barrel tenon threads need to be concentric with that same center-line.  I had to remove quite a bit of material to true everything up.

Next step was to chuck the receiver into a truing jig that allows movement in all directions and dial it in.  I turned down a set of bushings and a drill rod.  The bushings were a very slight press fit with my fingers with no play.

Bushings and drill rod for indicating

Dialing in the receiver

Here is another shot the factory threads before they get recut.

Factory threads – yuck

The next step was to apply layout die to the receiver face and face off just enough to get a complete clean up.  I am using a facing tool that I ground myself – it has become my favorite facing tool and seems to provide a far better finish than any of my indexable carbide tooling.

Facing the receiver

After a few passes (my notes indicate about 0.006″) I got a complete clean up.

Facing finished

Next I bored out the receiver to open the threads up to my new major diameter of 1.075 (factory is 1.0625) and to face the lug abutments inside the receiver.  The lug abutments on this particular receiver were actually really close and only required about 0.002″ to fully clean up.

Lug abutments faced

Next, I cleaned the threads up and cut them to 1.075-16 3B using a plug gauge that I made.

Receiver with plug gauge

Threads recut

Finished Receiver

 

Barrel Threading

This was one of my first projects once I became comfortable with my machine.  I thread the muzzle of my 10/22 1/2-28 for the new Silencer Co. SS Sparrow.  This particular suppressor has an internal o-ring to minimize reverse gas flow (you will see a lip in the completed picture).

First, I dialed in the barrel using a fixture that I saw on sniperhide.com.  This is an interesting way to measure runout in multiple places (moving the rod with the tailstock).  The rod itself does not turn, but instead of bounces up and down over the lands and grooves inside the barrel.  The plumb bob keeps the rod stationary by providing downwards tension the entire time.  The indicator is used to measure the movement of the rod inside the barrel.

Indicating the barrel

This is from a different job, but it shows a 0.0001″ indicator on the rod.

Indicator setup

Once the barrel is indicated, I added layout die to mark the different cuts.  Due to the o-ring cut, this suppressor was just a little more complicated than most.

Layout done and cutting

Here is a picture of the completed threads and o-ring shoulder.

Completed threads

Here is the rifle reassembled with the suppressor mounted.

Completed Rifle

This target was shot the following weekend with the Sparrow on the rifle testing different types of ammo.

Barrel Vise

After looking at options online for barrel vises, I decided to build my own.  Most of what I could find online looked flimsy and overpriced.  I hit up the local metal yard and looked through their drop pile until I found a 24″ long piece of steel 2″x4″.  The chunk of metal weighed in around 60 lbs and I gave them a $20 bill for it, seemed like a fair enough deal.

Like all of my projects, I did some design work first in Autodesk Inventor (my CAD software of choice).  Here is a finished exported drawing.

Completed Barrel Vise

I started by cutting the steel with a hacksaw (I don’t have a metal cutting bandsaw).  I don’t recommend this to anyone.  It took about 45 minutes per cut and the metal was very hard.

Finally made it through

After cutting both pieces, I cleaned them up in the lathe.  I know this really isn’t the right tool for the job, but since I don’t have a mill yet, I decided it would be fine to face all of the sides in the lathe.

Facing

After facing all sides of both pieces, this is how they came out looking, at least they cleaned up pretty well!

Facing Completed

Next, I added some layout die and marked all of my holes to be drilled.

Layout for drilling

Holes were then drilled and tapped.  I drilled the top holes quite a bit oversize to allow the vise top to “float” on top of the bottom.  This seems to work really well with the collets that I machine for the barrel tapers.

Tapping

Once the drilling and tapping was done, the vise was assembled and chucked into the lathe to center drill, drill and bore a hole through it to hold the collet.

Drilling the center hole

After drilling the center hole, I faced an extra 0.100″ off the vise top allowing some “crush” room for the collet.

Facing the vise top

Facing the vise top – closeup

Here is a picture of the finished product.

Finished vise

Vise with bushing

Bolt Drilling Fixture

Since I wasn’t able to find any “non-marring” socket head cap screws to use in my different fixtures, I decided to make my own.  I standardized all of my designs to use 5/8-24 socket head cap screws (SHCS) and ordered a large quantity from Amazon.  I was only able to find one local store that sold fine thread SHCSs, and they were over $1 each.  Amazon was much cheaper in bulk.

First, I created a fixture that I could chuck into a 3-jaw to hold the SHCS.  It is a pretty simple internally threaded cylinder… nothing fancy at all.

SHCSDrillingJig

SHCS in drilling jig

With the SHCS in the jig, I can then center drill it and drill it out to the correct dimensions (I found .198″ to be perfect for swaging in 4 gauge copper wire that measured to be .200″).

Drilled out SHCS

After drilling, I cut the copper wire with a hacksaw, swaged it in with a hammer and put the fixture back into the lathe to turn down the copper (mainly for appearances).

Finished SHCS with new copper tip

The new soft-tipped bolts have been working very well in my fixtures and it is easy to remove any copper residue from the finished part using a copper solvent like Hoppes 9.