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.