The M14 rifle: an Armorer's perspective part III match tuning the last wood and steel battle rifle.
The rifle we are using as a demo for our stock bedding class is a standard grade Springfield MIA with O.D. green composite stock and light profile 22-inch Parkerized barrel (MA9109).
The green composite stock is much more rigid than the GI fiberglass stocks Springfield offered years ago and fits the action well, except there was absolutely no barrel tension on the front band.
The rubber recoil pad is a welcome departure from the GI folding steel unit, and keeps the butt in place on your shoulder. The customer supplied an unfinished Boyd's medium weight laminated stock to be fitted and bedded.
The Boyd's stocks are much more rigid than a standard GI stock due to increased thickness and laminated construction. Laminated stocks are composed of layers of wood (birch, in this case) glued together with a resin infused into the wood fibers under pressure. If a customer specifies a wood stock for his Ml4, a laminate is always my first suggestion.
Preparing the Stock
There's a substantial amount of preparation to perform before glass-bedding. Starting at the back end, I install the buttplate and sling swivel. I install it early to protect the rear of the stock from chipping and damage while thrashing it around on the bench.
Some holes may need to be opened up slightly with a drill for easy passage of the buttplate screws and the end of the stock may be sealed against weather with whatever you are using for a finish. The buttplate fit the Boyd's stock nicely after adjusting the upper screw hole slightly.
Another area of concern is the stock ferrule. The ferrule is a stamped steel piece that provides a hard surface against which the front band can bear when the stock is fitted correctly.
After test-fitting the ferrule, I epoxy it permanently in place.
A tip here: sometimes the wood tab the ferrule fits on is a little longer than necessary. Grind the end of it so the open end of the ferrule is flush with the stock. If you leave it long, there may not be clearance between the end of the ferrule and the front band when the rifle is assembled.
Once the epoxy is dry, I grind the inside bottom of the ferrule and the stock back to the drain hole. This clearance is especially necessary with unitized gas systems, so the ferrule isn't pinched between the gas cylinder and front band. Thin the bottom third of the ferrule so it will easily fit in between the band and gas cylinder with a little wiggle room.
Wood stocks, except for the heaviest target models, are machined to accept the steel GI stock liner. The liner reinforced the M14 stock to prevent cracking when launching rifle grenades. It has been said that we are always fighting the last war, and in this case that may be true. Rifle grenades were in vogue during World War II and Korea, but I don't think the Vietnam-era M14 was employed as a launcher very often.
The liner is useful to us for strengthening the stock when properly installed, but it must first be modified. We want plenty of clearance around the receiver legs for bedding compound, so the inside vertical surfaces of the liner are cut back to roughly half their normal width with a thin cutting wheel on a hand grinder.
A 45[degrees] bevel toward the stock can be filed into the cut surfaces to enhance the bedding process by directing epoxy toward the wood rather than squeezing it out on to the bench.
Then test-fit the modified liner to the stock. I have seen aftermarket liners require some wood removal just to get them into the stock. A slightly loose drop-in fit is perfect.
If you have to tap it in place with a mallet, remove some wood. Make sure the screws will line up and the liner is flush with the wood inside the mag well so there are no mag fit issues later.
Once the liner is modified and fitted to the stock, mix up some epoxy to glue it in place.
A note on bedding compounds is in order here. My bedding products of choice are Bisonite and Marine-Tex (Brownell's 904-303-114). I tend to use Bisonite for wood stocks and Marine-Tex for synthetics, but that choice is more cosmetic than scientific.
At times I also employ Devcon products. Bisonite is the old-school steel impregnated epoxy developed for use by military teams several decades ago. It is not available from Amazon.com or Brownell's. In fact, the only source I know of is Champion Shooter's Supply (champion shooters.com).
Marine-Tex was originally developed for patching boats, and works very well for just about any bedding job. It is quite hard after curing. It is also much cheaper per ounce than Bisonite.
In the photos, I'm using Bisonite to bed our demo rifle. Mix ratio was nine parts base to one part hardener. The surfaces of the liner that make contact with the stock were given a coat of Bisonite, as were the corresponding locations on the wood.
When the liner is installed, epoxy drips out on to the bench so make sure you've got newspapers under the stock while it is drying. After 90 minutes or so, the Bisonite will become rubbery enough to trim away excess material. Let the stock dry overnight.
The next day, begin to fit the barreled action to the stock. Strip the rifle to the receiver, barrel and op rod guide.
You need a bedding fixture to determine when the rifle is positioned at the correct angle to contact the stock ferrule at the lip of the front band and induce downward pressure on the barrel to mitigate vibration.
No part of the barrel assembly should contact the stock except the lip of the front band. The fixture we used at MTU I still use is two parts: A bent piece of coat hanger and a unitized gas cylinder assembly with the tab on the front band cut off and ground flush.
The gas cylinder/bedding fixture is installed on the rifle and the position of the barreled action in the stock is adjusted with the coat hanger between the stock ferrule and barrel until the bottom edge of the front band is flush with or very slightly higher than the bottom of the ferrule.
Check for clearance around the op rod guide and remove wood as necessary if it touches the stock. I usually only have to adjust op rod guide clearance on the fat target stocks.
The receiver should be a loose fit in the stock before you mix any epoxy. Clearance around the receiver is essential to provide room for bedding compound and so the position of the rifle can be adjusted to the necessary slight upward angle.
The receiver legs on some commercial receivers may be a bit wider than original GI spec and require fitting just to get the rifle into the stock.
The Boyd's laminated stock was a tight fit, and I spent some time with a chisel, sandpaper and Dremel removing wood. Make sure the receiver can be centered in the stock so the inside of both receiver legs are flush with the liner. Otherwise, the magazine may not fit.
Once the stock interior looked good, I traced around the receiver with a pencil at the heel and rails. Now, groove the top deck of the stock for bedding.
With a 3/16" ball end mill in the mill/drill, I cut a groove approximately 3/16" deep just inside the lines traced around the receiver. This can be done with a Dremel, but be careful. The cutter can grab, sending it down ' the "outside of the stock and leaving an unsightly gouge (ask me how I know). The line around the heel of the receiver will have to be done by hand.
Preparation of the receiver involves claying up any voids epoxy could fill, locking the action into the stock. This is important. Use common modeling clay, pressing it into the hole and slicing it off flush with a razor blade.
I fill the opening for the op rod spring guide, the holes for the connector lock and the locking recesses in the receiver legs for the trigger guard. I fill the heel area so epoxy can't get inside it. Also, there is a shelf above the rear receiver legs where they meet the receiver that should be blocked.
The second step of receiver prep is applying release agent to all surfaces coming in contact with epoxy. You can use common paste wax on the metal, but I use Brownell's Acra-Release Aerosol (081-028-000) and hose down the receiver twice.
Be careful not to miss any spots. The receiver will be locked into the stock if you screw this up. I haven't personally lost any M14 stocks (fingers crossed) to lack of release agent, but 25 years ago there was an issue with a Model 70 target rifle I'd like to forget ...
One last step before bedding is taping off the areas of the stock where bedding epoxy might drip, using masking tape. Post bedding cleanup will be easier if you don't have to deal with cosmetic issues later.
I like to bed the barreled action first and then do the trigger assembly in a separate step. You can do both at once, but I find it better to do the bottom metal later so I have access to the inside of the stock for clean-up of excess bedding epoxy before it is completely dry.
The Bisonite is mixed in a ratio of 9:1. It can be prepared in ratios of 7:1-10:1. A higher ratio of steel base to hardener lengthens the drying time, and the theory is that a longer drying time allows more air bubbles to escape.
I measure by volume in old kitchen measuring spoons. Three tablespoons of steel base to one teaspoon of hardener gives a 9:1 ratio. I don't want the resulting epoxy to be real runny, or it will quickly drain out of the stock before it hardens, so a thickening agent is called for.
I have always added fine powdered fiberglass (flock) to adjust consistency. Mix in a pinch at a time until the epoxy will not drip off the popsicle stick used for stirring.
Apply epoxy to the routed areas of the stock with your popsicle stick/stirrer. Don't be stingy. Apply Bisonite to the receiver (don't forget to apply release agent first!) paying special attention to the rear of the receiver legs, which act as the recoil lugs on the M14.
When everything is coated, set the rifle into the stock and push it down slowly to squeeze out excess epoxy and air bubbles. Make sure the piece of coat hanger is in place at the stock ferrule and the bottom edge of the front band on the modified gas cylinder assembly is flush with the bottom of the ferrule.
I lock the receiver in position with a Badger Ordnance M1/M14 bedding clamp. As far as I can tell, these clamps are no longer in production, but a piece of surgical tubing tied around the receiver and stock will also work.
Set the rifle aside for around 90 minutes until the Bisonite is rubbery enough to trim with a knife, and trim away as much excess as possible. Looking into the mag well, inspect the epoxy around the receiver legs for voids and press more into place to fill weak areas if necessary.
Pull the masking tape off the stock and scrape away any epoxy that dripped on to the wood. Set the rifle aside for 24 hours to dry.
Once the epoxy is dry, remove the rifle from the stock. With the rifle inverted, support the barrel and the buttstock, and tap the receiver free with a brass drift from inside.
Check the bedding for any large voids created by air pockets. Do a skim coat to touch it up if necessary. Trim excess dry epoxy with files and a Dremel. Check the magazine fit in the stock.
The Boyd's stock was still a bit tight, so I clamped it in the mill and trimmed around the inside of the mag well with a long 3/8" end mill to flush everything off smooth. Magazine fit is one of those things you tend to forget until you're at the range test firing.
Now, on to the trigger housing. The trigger housing should make contact with the stock only in three spots: the left and right pads and the rear of the housing behind the trigger.
When inserting the assembled trigger housing into a commercial stock, you may find that the extended portion of the sear drags on the wood. This is bad and can cause, malfunctions.
The sear extension was originally intended as a part of the select-fire mechanism on the military M14 and serves no purpose on a semi-auto civilian rifle. The best solution is to drag out the Dremel with a cutting wheel and hack it off.
With the sear neutered, test-fit the housing to the wood with the barreled action installed. It was tight in the Boyd's stock, with the sides making hard contact.
I clamped the stock in the mill vise and took a skim cut around the trigger housing area with an end mill. Problem solved.
Once again, I assembled the barreled action and trigger housing to the stock, and traced around the left and right housing pads with a pencil to outline where the wood must be removed for bedding.
The traced areas can be hogged out with either an end mill or Dremel. At the rear of the trigger group opening in the stock there is a slot for trigger clearance, and raised pads where the housing bears on either side. I mill this area out flat.
Apply modeling clay to the slot in the rear of the trigger housing and forward into the opening where the trigger lives. Squeeze some clay into the small area between the trigger guard and housing on both sides so epoxy can't prevent the guard from being opened during disassembly after the bedding dries.
Don't forget to hose the trigger housing with Acra-Release. Apply epoxy to the three pads of the housing and the relevant spots on the stock.
With the barreled action in the stock and inverted on the bench, install the trigger housing but don't rotate the trigger guard fully into locked position.
Leave it open maybe 3/4". Let the assembly dry for 90 minutes or so until the epoxy is rubbery, and trim off the excess. Set the rifle aside to dry overnight.
Once the epoxy has set overnight, the trigger housing may resist removal. Open the trigger guard and tap it out through the top of the receiver with a brass drift. Inspect your work. If all three pads look good, trim off the excess epoxy.
You need to cut a 1/4" wide channel down the center of the rear pad for trigger clearance. If you fail to provide adequate clearance for trigger movement, the rifle may double. I cut the channel at least deep enough to expose wood, and usually deeper.
A rifle firing two rounds per trigger pull can be embarrassing for the armorer and the customer, not to mention dangerous and illegal. Make sure the trigger has full movement without bottoming in the stock.
With bedding complete, check your work. Install the unitized gas system on the barrel with the appropriate shims, and assemble the barreled receiver and trigger housing to the stock.
You should feel substantial resistance when the receiver and trigger housing tighten into the stock.
The lip on the bottom of the front band should be bearing firmly against the stock ferrule. To test for foreend pressure, position a thumb just behind the ferrule as the index finger pulls down on the top of the band and releases. The band should snap back against the ferrule.
If adequate clearance isn't ground into the ferrule area of the stock, the gas system may bind and you won't be able to pull it out of contact. There must be clearance between the gas cylinder and ferrule.
The last step in fitting the stock is the handguard. Most M14 handguards, except for the earliest examples, are constructed of fiberglass or plastic. The earliest rifles had matching wood handguards like the Garand.
Military Ml4s were designed for selective fire, and wooden handguards would char and even catch fire when the rifle was employed as a light machine gun. Fiberglass was found to provide improved heat resistance and cost less to manufacture.
As the original Gl fiberglass handguards dried up, manufacturers such as 'Springfield Armory and Fulton Armory switched to modern commercial plastic handguards, which may be tougher than the original Gl issue part. No matter which handguard you have on your rifle, you want it to fit correctly.
The Boyd's laminated stock arrived with a nice matching wood handguard. It was oversized in length and depth. The handguard should have no contact with the receiver when it is installed.
Our Boyd's handguard made hard contact with the front edge of the MIA receiver so I shortened the rear end about 1/8" on the belt sander. The handguard clip must be installed to test fit the handguard, and installation is frustrating without the proper pliers at hand.
Badger Ordnance produces a handy set of handguard clip pliers no M14 armorer should be without (Brownell's 093-200-050). The handguard was making contact with the stock, so the edges were reduced with sandpaper until there was no wood-to-wood contact.
After fitting, the front end of the handguard is locked in place by the tabs on the front band. Simply bend the tabs up against the wood and the handguard shouldn't be loose.
This technique works on an annealed front band because the tabs were softened as part of the unitizing the gas system. If the tabs aren't annealed, you may not want to bend them. Back in the day, we used to epoxy the handguard to the front band.
The final task as far as the stock is concerned is to seal it against moisture. There are numerous products out there for sealing stocks. Birchwood Casey's Tru-Oil is one I have used in the past.
I was going to use Tru-Oil for this project until I discovered my bottle had semi-hardened and was useless.
Another product I use is not so well known. Velvit Oil by Velvit Products (velvitproducts.com) fills, seals and protects wood products. The Boyd's stock was already well sanded, so I painted it with a heavy coat of Velvit Oil #200 Natural and let it soak in.
As dry spots appeared where the sealer had soaked into the wood, I applied more Velvit Oil. The stock should be well saturated after a few hours and multiple coats. Wipe off excess oil and let the stock dry for a few days.
The next step is wet sanding using 400 grit wet or dry paper and Velvit Oil as a lubricant. This serves to fill the pores of the wood. The Velvit Oil can be cut with mineral spirits to enhance penetration and successive light coats of Velvit Oil can be applied to produce a sheen.
There is a technique to finishing stocks to produce just the right look involving many coats of finish over a period of weeks but it is beyond the scope of this article. A detailed article on proper use of Velvit Oil can be found in the February 2005 American Gunsmith magazine written by Jerry Fisher.
Part 4 of this article will cover sights, triggers, scope mounts and test firing.
For further reading about M14 development and history consider The Last Steel Warrior: U.S. Ml4 Rifle by Frank Iannamico.
Caption: Norcross is getting to the home stretch of this M1A build. A final rub-down with a nylon stocking gives the completed laminated stock a handsome sheen.
Caption: Permanently epoxy the stock ferrule to the stock after fitting. Then grind or file the ferrule and the wood behind it to create clearance for the gas system.
Caption: The steel stock liner helped prevent cracking when launching rifle grenades. Thin the vertical legs to create space around the receiver for bedding compound.
Caption: A field expedient liner screw wrench can be fabricated from a flat tip screwdriver. This is just fine unless you're planning to specialize in M1A gunsmithing.
Caption: Norcross used Bisonite, a steel-reinforced bedding compound used since the 1960s, to bed the steel liner into the stock. It's not going anywhere after this.
Caption: The bedding fixture is an old unitized gas cylinder with the lip of the front band ground flush. A piece of bent coat hanger positions the edge of the front band.
Caption: Recesses in the receiver are filled with clay to prevent bedding compound from seeping into them, If you don't do this part carefully, the barreled action can seize.
Caption: Rout the stock with a 3/16" ball end mill to provide clearance for the bedding compound. Then paint the routed areas with a black marker for clarity.
Caption: Action bedding can be a sloppy process. Be liberal with the masking tape, and I trim off excess bedding compound while it is still rubbery and before it hardens.
Caption: Norcross cleaned up the magazine well with a long 3/8" end mill after the epoxy dried. It's vital to be sure the well is clear; test with a magazine in the shop.
Caption: The full auto sear extension has no function on a semi-auto and may interfere with the stock, so Norcross recommends cutting it off altogether.
Caption: Fill the gap between the trigger guard and trigger housing with clay before bedding. Leave the guard partially unlocked to provide draw on the action.
Caption: Arrows indicate bedding pads for the trigger housing. Note the trigger clearance groove in the rear pad. It is needed to prevent doubling during firing.
Caption: A Badger Ordnance handguard clip tool is invaluable to avoid cracking the handguard. It spreads the clip evenly to avoid cracking, especially with a wood guard.
Caption: The handguard should not touch the receiver or the stock, and it should be attached to the front band. Carefully inspect all those clearances before proceeding.
Caption: Gunsmiths are known for a bone-dry sense of humor. Norcross is one of a vanishing breed who learned the craft on the M14; a rifle that had its peculiarities.
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|Date:||Apr 10, 2017|
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