The new Kel-Tec KS7 shotgun is possibly the best pump-action bullpup shotgun ever marketed in the USA, but even it can benefit from smoothing of a few key areas.
It's obvious the Kel-Tec engineers learned a lot from the older dual magazine KSG model, and they built that knowledge into the new KS7.

My KS7 bought in mid-2020 operated right out of the box much smoother then my older KSG but I decided to further smooth the KS7.
It needed very little work on the metal to accomplish that.
Actually I spent most of my time using a fingernail board to lightly break the sharp mold edges from the plastic parts, especially around the loading port.
This simply gives the gun a smoother, more comfortable feel.

The KSG and KS7 are variations of the old John Browning Ithaca Model 37 shotgun design.
The critical operations occur in the last 1/2 inch of movement of the forend to the rear, and the last 1/2 inch of movement to the front.
The last 1/2 inch of movement to the rear is when the right shell stop is operated and ejects a shell into the receiver for chambering and the left shell stop is operated to catch the next shell in the magazine and prevent a double feed.
In the last 1/2 inch of movement to the front is when the left shell stop is reset to allow the next shell to move slightly to the rear in the magazine into the next to feed position where the right shell stop catches it.
Anything that can smooth the operation of these functions will give a much smoother, more reliable gun.
After this my gun is one of the smoothest operating shotguns I've ever had, and smoother then my KSG even after working it over.

Before starting, I recommend first reading my article on the details of what "fluff & buff" actually means and the techniques and tools used to do it......

The key here is that gun parts can be SMOOTHED to make operation easier, but NOT polished.
When professionals talk about "polishing" we don't mean "like a mirror".
What we mean is that roughness left by machining of parts can be smoothed just enough to reduce any catching or rough operation. Polishing to a mirror shine does nothing to aid in smoothness of operation and is often the reason gun parts are ruined when metal is removed and critical surfaces are changed.
Do ONLY enough work to lightly reduce roughness. That doesn't require a perfectly smooth surface.

The entire job on the KS7 can be easily done with wet or dry abrasive sheets in the finest grits.
Most any hardware store will stock these in the sand paper area.
Even finer grits can be bought at auto supply houses that sell car painting supplies.
You'll need to back the abrasives by wrapping strips around flat files, wood strips, and round dowel rods so you can control where the metal is smoothed and keep it in the original contour.
Use the abrasives like you would a file.
To remove sharp casting edges from the plastic parts, a fingernail board from the cosmetics section of a Walmart works very well.

For reference this is a link to Kel-Tec's Owners Manual and the schematic of the KS7. I'll use the factory part numbers where needed......

The first step is to field strip the gun according to the Owner's Manual.

I recommend NOT disassembling the trigger group.
First there's really no need since the KS7 already has the best trigger of any bullpup firearm, and the assembly is not easy to reassemble.
If you decide to do so anyway, I strongly recommend viewing the video on the Mcarbo web site where they show how to install their replacement trigger assembly.
This will make reassembly easier and prevent damaging the plastic trigger group sections.

Once it's field stripped, unscrew the four button head screws from the rear sides of the forend, Parts S008, and remove the bolt carrier assembly Part 185.
You'll need a 2mm metric Allen wrench for all the bolts on the KS7.
The rear of the forend needs to be spread slightly to allow removing the bolt carrier.

I began with the buttstock and shell lifter assembly.
Use the 2mm Allen wrench to unscrew and remove the bolts in the stock.
One bolt is longer then the others so note which hole it goes back in.
Don't loose the tiny lock nuts, some will fall out and some won't.

Separate the two halves of the stock assembly and lift out the shell carrier, Part 352.
While it's apart, now is the time to use the fingernail emery board to lightly break the sharp mold marks on the plastic parts.

The shell lifter is a key part to smooth and this goes a long way to a smoother operating gun.
The key areas are the curved section on the bottom-rear. That curved area is where the bolt carrier contacts the lifter and operates it.
The idea is to lightly smooth the curved area and lightly break the sharp edges on the sides so the bolt carrier can slide smoothly over the surface.
Lightly smooth these areas and bevel the sharp edges.
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Lightly smooth and bevel the sharp edges of the tines on the front.
These areas are where the shell slides during the feed and ejection process.
DO NOT TOUCH the two notches on the underside of the lifter.
Those are the actual ejectors and any changes may cause ejection problems.

After the lifter is smoothed, apply a light coat of grease to the curved areas on the bottom-rear and the two pins in the sides of the plastic stock, then reassemble the buttstock assembly.
Grease will not evaporate, dry out, run off, or leave the lifter contact surfaces dry of lubricant.

Next look at the bolt assembly.
On my KS7 I found nothing that really needed attention, it was much smoother then my KSG.
Areas to inspect for possible roughness are the operating surfaces on the locking block Part 174.
Unless these are very rough, just apply a light coat of grease to these surfaces.
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Inspect the top-rear of the locking lug.
Often in shotguns that edge can wear and develop a burr that can cause rough operation.
If a burr is forming, JUST LIGHTLY break the sharpness. DO NOT remove any metal.
Apply a dab of grease to the rear and top of the lug.
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I saw nothing on the extractor, firing pin, or the bolt body that needed any attention.
I would recommend cleaning off the factory storage and shipping lube and applying your favorite lubricant.
Apply a little grease to the bottom of the bolt where it slides on the bolt carrier.

The next step is to bevel the lifter operating and hammer operating surfaces of the bolt carrier.
These are the surfaces that contact the shell lifter to operate it and push the hammer back. Beveling these
surfaces will give a good reward in smoother operation of the gun.
Lightly round and smooth these areas.
Apply a dab of grease to all three areas.
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The lower-rear surface of the rear slot in the carrier is what causes the "bump" as the carrier slides over the hammer when the forend is moving forward.
Lightly beveling it reduces that bumping, hesitant feel.

On the front of the carrier is the "box" that operates the two shell stops,
Lightly break the right-top-rear inside of the box.
Just lightly bevel and smooth the right-top-rear inside area.
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I don't recommend disassembling the shell stop assembly. It's surprisingly difficult to work with.
I did so just to see how smooth it was and if it could be improved by any work.... It couldn't.
What appear to be two black steel bushings are actually two hard plastic collars that are a very tight press-fit on the retaining pins and make it difficult to reassemble while also resetting the spring.
Because of the difficulty I'd recommend just leaving it alone, on my gun it needed nothing done. Unlike the KSG the slots in the KS7 shell stop is so smooth no work would be of any benefit.

The top surface of the right shell stop, Part 331 needs to be smooth and the edges need to be lightly beveled.
It was here that I found indications of some possible hand smoothing done at the factory.
DO NOT do a lot here since any metal removal will cause failure of the shell stop to properly release shells during the feed cycle.
Apply a coat of grease to the surfaces and slots shown.

Inspect the locking lug recess in the rear of the barrel, and if the edge is very sharp or is developing a burr LIGHTLY bevel the edge. Again, do not remove any metal.
Apply a dab of grease to the locking lug recess and grease the flat area behind it.

Lightly round off the "lumps" on the hammer.
This will reduce the "Bump" and sticking feel when the action starts to close.
Apply grease to this area.

The barrel of the Kel-Tec shotguns are parkerized inside and out, including the bore and chamber.
It's the roughness of the parkerized finish in the chamber that may cause some problems with extraction, especially with cheap, low brass shells.
Kel-Tec recommends that no low brass steel or aluminum head shells be used in these shotguns, however these days most shells may have brass plated steel case heads. A magnet will detect steel case heads.

If you experience extraction problems, polishing the chamber may cure it, and usually allows use of even budget low brass steel head shells.
You can polish the chamber, and the bore if you like, by chucking a 12 gauge cleaning rod in a drill and wrapping a used 12 gauge bore brush with some 0000 steel wool.
Run the drill at medium speeds and keep it constantly moving up and down the chamber, and the bore if desired.
This doesn't take a lot of time so don't over do it.
After polishing thoroughly clean the bore and chamber of all residue and apply a rust prevention lubricant.

NOTE: Running steel wool with a drill in a SMOOTH BORE gun is a valid method of polishing and cleaning stubborn fouling from shotguns, but NEVER run a brush or any abrasive in a RIFLED bore.
It WILL ruin it and do so fast.

This completes the "fluff and buff" work and the final step is cleaning off abrasive and plastic dust and applying lubrication and rust proofing before reassembly.

I recommend cleaning out the magazine tube and the spring to remove factory storage lube and applying whatever working lube you like.
I've experimented with WD-40 Dry Lube With Teflon as a lubricant and preservative in the magazine tube and on the spring.
I've found that a dry lube does not seem to lubricate the inside of the tube very well and I got a lot of spring "squeak" as I loaded the gun. So, I went back to a light coat of very thin grease or a thick oil on the spring and in the tube.
Standard liquid lubes will migrate down the magazine tube and into the action, so I use a thin grease on the spring and in the tube.
Since the spring has to be removed for normal disassembling and cleaning of the gun, it's no problem to inspect and wipe out any fouling or debris that gets in the magazine tube.

To prevent rusting of the gun I apply a fine coat of CLP Breakfree to all surfaces.
I do this by putting a few drops of CLP on a soft toothbrush and "scrubbing" all surfaces. This will leave a very thin coat of CLP that will go a long way toward preventing any rust or corrosion.
Use grease or your favorite lubricant on the actual operating surfaces to limit friction.

Following this simple process will give you a KS7 that operates much smoother and will reduce chances of short stroking the gun and causing stoppages.