This month, I’m going to explain and demonstrate
the removal and installation of a Remington 870 stock or grip.
Changing stocks on an 870 is quite simple in theory, and it’s really not hard to find
the basic steps online. However, there are a lot of small details that these basic instructions
usually don’t address, and this has led to mistakes and confusion for many 870 owners.
So, the bulk of this video’s runtime will focus on the details that tend to get glossed
over - such as what length bolt or screw to use, when a stock bearing plate is called
for, which stocks fit which models, etc. I’ll also address some common questions
I’ve seen, and pass on some gunsmithing tips and practices that a lot of 870 owners
aren’t exposed to. I’ll start with removal, but first, a couple
notes: There’s generally no need to remove the
buttstock on your 870 during normal cleaning or servicing. However, stock removal is recommended
if you’re attending to a gun that has gotten extremely wet, or if you’re dealing with
extensive rust or other finish damage. Removing the gun’s existing buttstock is
also required when installing new furniture, of course, and some 870 owners will keep multiple
stocks that they swap on and off depending on what they’re doing at the moment.
Also, some aftermarket or specialty stocks and grips have to be removed in order to get
the trigger plate assembly out of the receiver. In that same vein, you do not have to take
apart the rest of the shotgun to remove or install a stock or grip; but some folks prefer
to strip the receiver, or at least take off the barrel, to make the gun less cumbersome. You can refer to my disassembly video if you need assistance with that. You’re generally fine either way, unless the furniture you’re installing specifically
requires that other components be in place first.
Factory stocks for the 870 mount to the receiver using a draw-bolt that is accessed from the
stock’s butt end. In order to get to this, the stock’s buttplate or pad must be removed
first. Just about all 870s these days use rubber
or foam recoil pads. These are held on by two screws, which are accessed by sticking
a screwdriver through holes in the rear of the pad.
Most buttpad screws are Phillips-drive, and are best removed with a round-shank #1 Phillips
screwdriver. I would recommend using a standard screwdriver over one with interchangeable
bits. Special long bits with narrow round shafts can work, but your typical interchangeable-bit
screwdrivers are too wide to fit into these screw holes without tearing or stretching
the pad. Make sure that whatever screwdriver or bit
you’re using has a tip that’s in good shape to avoid stripping the screws.
You can apply a little oil, grease, or soapy water to the screwdriver’s shaft to allow
it to turn easier inside the pad. I’ve never needed to do this, but if the holes are really
narrow or your tool has a fat shaft, lubricating it can help. Yakko: “Goodnight everybody!” Insert the screwdriver into the pad’s screw
holes, and find the screw head. This may require a bit of fishing around. Once you find the
screw, back it out, lefty-loosey, while applying pressure to keep the driver from camming out
and stripping the screw. If you pull the pad rear-ward as you back
out the screws, you’ll keep the screws from pushing themselves out, which can stretch
or tear the holes in the rear of the pad. Plus, the screws will stay inside the pad
where they’re less likely to get lost. If you’re working with an older 870, you
may have a solid butt-plate instead of a pad. These also attach with two screws. They usually
have a #2 Phillips head; other drive types have been used as well, but if so, it should
be pretty obvious what tool you need. Some stocks will have additional parts like
spacers or shims underneath the buttpad or plate. These don’t normally change removal
or installation, aside from giving you more things to keep track of.
Once you have the buttpad or plate off, you’ll be able to look inside and see the head of
the stock bolt. Factory 870 stock bolts usually have slotted
heads. These can be removed with just about any medium or large flat-head screwdriver
that’s long enough to reach, but it’s best to use a screwdriver that’s a proper
fit in the slot in order to avoid stripping it out.
Brownells makes a special 870 stock bolt bit that attaches to standard 3/8” square drives,
and fits over the bolt head to stay centered. It’s nice to have if you work on a lot of
870s or change stocks frequently; but an appropriately-sized flathead screwdriver works just fine, too.
To remove the stock bolt, unscrew it counter-clockwise while applying pressure to keep your tool
in the screw. A flashlight can be helpful here for locating the bolt and getting your
tool engaged correctly. If you’re not using a self-centering tool, keep it aligned in
the bolt to prevent it from stripping the slot or gouging the interior of the stock.
If this is an old or neglected 870 and the stock bolt is seized up in the receiver stud,
take the trigger plate assembly out of the receiver, spray a little penetrating oil into
the hole in the receiver stud, and let it sit for a bit. Under the head of the stock bolt itself, there will be a small lockwasher followed by a larger
fender washer. Take care not to lose these, and replace them if they’re missing.
Wrapping a rubber band around the stock bolt works well for keeping these washers from
sliding off to parts unknown. If you’re replacing this stock and won’t
be using it for a while, you can re-insert the stock bolt & washers, then re-install
the buttpad or butt plate to keep everything together. Some aftermarket stocks come off much like factory stocks, but others can be significantly
different. For example, the mounting fastener for the
popular Magpul SGA stock is accessed via the top of its grip, rather than its butt end.
A lot of the more elaborate aftermarket 870 stocks have one component or assembly that
is installed on the receiver first, and then the rest of the setup is mounted and assembled
from there. If your gun came with an aftermarket stock and you’re having trouble figuring
out how it comes off, contact the manufacturer for assistance. Most pistol grips and many aftermarket stocks attach to the receiver using shorter machine
screws that require a hex wrench. Hex keys for 1/4” fasteners are usually 3/16” or
5/32”, depending on the head type, but you may come across some exceptions.
With pistol grips, these mounting screws are generally pretty easy to find, but occasionally
they may be concealed or tricky to get to. This Pachmayer unit, for example, has a separate
rubber grip that has to be removed in order to access its mounting screw. Again, if you’re stumped by an aftermarket grip, contact the manufacturer. If the stock you just took off was a wood one, another component you should find at
this point is the stock bearing plate. This is an important part if you’re using a wood
stock. Wood is an example of what’s called an anisotropic
material; its composition is not regular, and its physical properties and mechanical
behavior vary depending on how it is oriented. At the cellular level, wood consists of hollow
cellulose fibers stuck together in a parallel arrangement by a biological polymer called
lignin. There are other structures present as well, but the fibers and lignin are the
primary load-bearing elements. The cellulose fibers are many times stronger than the lignin,
and the differences between the two are what gives wood its direction-sensitive structural
properties. Consider a bundle of straws held together
by a cheap glue. The bundle will handle a lot of compression or tension parallel to
the straws, and will also resist perpendicular bending and shear stresses quite well. However,
it is far less resilient when the weaker binder carries the load, such as when shear stress
is applied along the straws, or tension is applied perpendicular to them. This is why any properly-made wood gunstock will have the grain running longitudinally.
This orients the cellulose fibers to best handle the compressive forces of recoil, as
well as shear and bending stresses applied vertically or from the side.
Even fancy-figured stocks that give up some strength for aesthetics retain the stronger
and more predictable straight grain in their narrower grip sections. Now, if you look at the rear of an 870 receiver, you’ll see that it does not make contact
with the entire front of the stock; due to this cut-out at the bottom that accommodates
the gun’s trigger plate assembly. If a wood stock was installed directly against
this surface, the loads of recoil and handling would be applied unevenly. This creates stress
concentrations along these edges that strain the lignin, and could cause the wood to eventually
crack or split with use. The steel bearing plate distributes the force over the entire
front end of the grip, preventing these stress concentrations.
Also, since stocks for the 870 and other related Remington shotguns fit into the receiver,
if a wood stock designed to use a bearing plate is installed without one, the center
of the stock won’t make contact, and all the recoil force will be concentrated on this
small area around the stock tenon. This produces very high shear stresses along the grain - where
wood is weak. The results of firing a shotgun with a wood
stock installed thusly are not pretty. The stock bearing plate acts as a spacer,
keeping these edges from contacting the receiver so that the forces are distributed over a
much larger area, and the stresses are directed through the center of the stock as compression,
not shear. For these reasons, all wood 870 stocks should
be installed with a bearing plate. Even if your gun has an aftermarket or early wood
stock that’s designed to fit into the receiver without a bearing plate, you should take down
its tenon so that it will accommodate one. Now, while wood is anisotropic, materials
like plastics and metals are isotropic - they have essentially the same properties in all
directions, and no orientation is meaningfully weaker than another. Thus, they do not require
the support of a bearing plate. Pretty much all non-wood stocks have taller
tenons that fit into the receiver without bearing plates.
You may come across synthetic stocks that use bearing plates because they copy a wood
stock pattern, but these are unusual. Normally, if you install a synthetic 870 stock
with a bearing plate, you’ll end up with an unsightly gap where the stock and receiver
meet, and the stock may not align itself properly. There are two versions of this part; one for
large-frame 870 receivers, and another for small-frame receivers. Bearing plates for
the small receivers have a notch in the top that makes it easy to tell them apart.
20ga is the only bore size that has been offered for both 870 receiver sizes. If you have a
20ga, and you’re not sure which bearing plate it needs, measure the width of the receiver. Stock bearing plates can be ordered from Remington, and other gun parts sellers; or they can be
found on the used market. You can also check with your local gunsmiths,
they may have one lying around that they’ll let you have for a couple bucks. That’s
how I got the plate for this stock. Since we just discussed receiver sizes, this
is as good a time as any to explain stock interchangeability with the 870.
It’s actually not all that complicated. 870 stocks are made to fit either large or
small receivers, and all stocks are interchangeable between same-size receivers.
Due to the overwhelming popularity of the 12ga, this does mean that the large receivers
have had far more stock options than the small receivers. However, Mesa Tactical recently
introduced a nifty little adapter that allows large-frame stocks to be installed on the
smaller 870s. The match-up isn’t perfect as far as looks go, but it’ll get the job
done. The last thing I want to get into before we
move on to installation is the fasteners. Obviously, you’ll need the right bolt or
screw to properly install your stock or grip. Pretty much all factory stocks use one of
two stock bolt lengths. Long stock bolts are ten and a half inches in total length, while
short stock bolts are eight and one-quarter inches. Which stock bolt a specific stock
needs depends on the stock style and when it was manufactured.
If you have a factory stock that’s missing its fastener, measure the stock bolt channel.
It should be pretty obvious whether you need the 10” or 8” bolt.
If you’ve purchased an aftermarket stock or grip for your 870, it should come with
a complete set of fasteners. However, one thing I’ve noticed with aftermarket
furniture is that the included fasteners are often shorter than they should be. Sling mounts,
adapters, and other accessories that install between the stock & receiver can also space
the stock & stock bolt back, exacerbating these problems.
An 870’s receiver stud has about 8/10ths of an inch of threads in order to provide
a solid mount for the stock. To take advantage of this, stock fasteners should be long enough
to reach the plane where the stock & receiver meet, or even come an eighth of an inch or
so past that point. Luckily, the receiver stud’s internal threads
use a standard ¼”-28 UNF thread pitch, so replacement screws are very inexpensive
and easy to find. Look for the same head type as the original fastener to ensure it’ll
fit correctly, and keep any original washers. Don’t forget to include sling plates or
stock adapters when checking length, if you’re using them.
Basic alloy steel fasteners will work fine here. They’ll be cheaper and stronger than
your run-of-the-mill stainless equivalents, and if you’re letting your gun sit and rust
away somewhere, other parts will fail long before you have any issues with the stock
fastener. Because the 870’s receiver stud is not threaded
all the way through, a fastener that’s too long can’t pass into the receiver and cause
problems, so there’s no need to worry about that. If you try a screw and it stops before
your stock or grip is tightened all the way down, you’ll just know you need something
shorter. If you’re not an expert on threaded fasteners,
just take your stock or grip and its original screw in to your local hardware or fastener
store, and someone there should be able to help you find something equivalent in a suitable
length. Now, with all that addressed, let’s move
on to installation. Before attaching your stock or grip, inspect
the receiver stud, and the screw or bolt that will be going in it. The threads should be
clean and intact, and the bolt or screw should thread all the way into the receiver stud
with little to no resistance or looseness. If either are damaged, it’s best to replace
them, though light damage to receiver studs can be remedied with a tap. See this video
for details. If applicable, also check the screw holes
for the buttpad or plate. These can wear out over time, and may need to be filled or shimmed
for the screws to grip properly. Check the length of the stock fastener to
make sure you’re going to get good engagement; including any and all washers, sling mounts,
and the stock bearing plate - if you’re using one.
Make sure the receiver’s stock recess is clean and free of rust or debris. To best
protect this part of the receiver in case water makes its way under the stock, you can
wipe a thin layer of protective grease onto the metal surfaces that will be covered up.
I also like to use a bit of thread paste on the fastener’s threads to retard corrosion
and reduce wear. Some folks use blue threadlocker here. I’ve never had an issue with a stock
bolt backing out, so I’ve seen no need to do this with my guns.
Whatever you’re using, don’t squirt a ton of it into the receiver stud; that’s
just asking for it to be pushed through and make a mess of your trigger plate assembly.
Just apply a small amount to the threads of the stock bolt before screwing it in. When installing, it’s very helpful to set your receiver so that you have both hands
free to juggle your stock, stock hardware, and tools. A padded vise is ideal, but not
always available. Simply laying your receiver on a flat surface works pretty well, and it’s
what I recommend for first-timers. As I mentioned earlier, stocks can be installed
with the rest of the gun assembled, but this can make things a little awkward if space
is limited. To install a factory or factory-style stock,
place the stock bearing plate over the receiver stud if you’re using one. Slide the stock
bolt lockwasher and washer onto the stock bolt. Note the two little teeth stamped into the edges of the stock bolt washer. If your stock
has a flat surface inside for this washer to tighten against, install the washer with
the teeth facing forward. If you have a hollow molded plastic stock with a raised tube instead,
install the washer with the teeth facing back. Insert the stock bolt, line the stock up with
the receiver, and start the bolt in the receiver stud. If your stock allows, it’s helpful
to start the bolt by hand. Be very careful not to cross-thread at this point; stop and
check if you feel anything more than very minor resistance.
Once it’s started, screw the stock bolt in until things just start to snug up. Double-check
the stock’s alignment with the receiver, then tighten the stock bolt down the rest
of the way. I have come across some torque recommendations
for 870 stock bolts, but not from the horse’s mouth, and few are going to be using a torque
wrench for this anyway. For most folks, a good, firm hand-tightening with a screwdriver-type
handle should get you where you need to be. If you’re using a wrench, it’s very easy
to over-tighten, so take it easy. Once the stock’s on, reinstall the buttpad
or buttplate - along with any spacers or reinforcing plates.
For best results, alternate between the screws until both are most of the way in, align things
as best you can, then tighten both screws just until they’re snug and the pad or plate
doesn’t move around. Going tighter than this is unnecessary, and can strip the screw
heads or the threads in the stock. When it comes to aftermarket furniture, some
will install almost exactly like factory parts, while others can be pretty complicated.
All should come with some form of instruction sheet; follow this, and contact the manufacturer
if you have additional questions. But as with factory stocks, start the mounting
screw in the receiver stud carefully to avoid cross-threading, thread in ‘til snug, then stop and check alignment before tightening the rest of the way. Assemble the rest of the gun as needed, then check function to make sure everything’s
working as it should. Well, I hope I was able to pass on something
helpful here. As always, I’ll be happy to field questions; and comments or video ideas are
welcome. If life manages to stay somewhat calm, I’ll
be back next month. Until then, have fun and shoot safe.
