High Standard Model 10 Bullpup Maintenance
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Author:  BioHazard [ Tue Jan 17, 2012 8:14 am ]
Post subject:  High Standard Model 10 Bullpup Maintenance

Since there's not a lot of info on these guns and since most of the info is incomplete or incorrect, I thought I would post some photos of a complete tear down of my Model 10 B for an internal cleaning.

And since there's not a High Standard section here and since the Model 10 was the fore runner of the "tactical" shotgun, this seemed the logical place?

The original design was by Alfred Crouch in the late 1950s.
He designed the bullpup housing with integrated lighting around a shortened Remington 11-47. Actual production version by High Standard was based on their Sears Model 66 and HS Supermatic/C1200 series in the mid 1960s.

The Model 10 is 26.1" long with an 18.1"'d be hard pressed to find a more manueverable shotgun. It weighs just over 10 pounds loaded. It can be fired one handed with practice.

For those not familiar, there were two versions:

The Model 10A with light in the carry handle:

and the later Model 10B with a thumbscrew detachable flashlight:


The Model 10s are gas operated, not recoil operated as the Wikipedia states.

The original High Standard shotguns they were adapted from were field guns and some versions actually had gas regulator systems for adjusting the gas system for different loads but since the Model 10s were intended to be fighting shotguns, the gas regulator was replaced with a solid piston with fixed bleed ports. The magazine tube still has the milled groove in front of the gas port for the regulators, but it is blocked off on the M-10s.

The intent was to use only full power loads and the gun is marked "for High Wall brass and magnum loads only".

There is a difference in the gas piston of the Model 10A and 10B and I've heard some owners say their Model 10A would work with lighter loads. I've never heard a Model 10B owner say that....the 10B needs full power loads and will not work reliably with light weight loads or reduced recoil loads. Light skeet loads will barely move the bolt.

Since the entire shotgun is enclosed in a plastic housing, it's a little more effort to disassemble than a normal shotgun. Also, since HS changed the yoke attachment without telling anyone, a lot of later Model 10B owners didn't know how to remove the yoke and couldn't get their gun apart. All 10As and the early 10Bs used and Allen bolt in the center of the yoke. The manual with my 10B showed removing an Allen screw, but that had been changed to a detent pin on the rear of the receiver.

The picture below shows the small hole in the yoke to access the pin that releases the yoke from the receiver.


Depress the pin, jiggle the yoke and it will slip right off. Now you can slide the rear bullpup housing off. Unscrew the forend cap screw and then twist the forend cap off the front and slide the housing forward about 2" and you can remove the left side cocking lever and track. This will release the bottom half of the housing. Loosen the Allen screw in the front sight and thread the sight base off the barrel and you can slide the top half of the housing off the muzzle.

Now you have a plain old shotgun receiver with a short threaded barrel.
Push the two receiver pins out to drop the trigger group.



Pictured is both the original factory 4 round tube and the extended 7 round tube.
There are some obvious differences.


The gas piston has recesses milled both outside and inside. This system is designed so the piston actually floats on gas for the first several inches of travel. The gas not only blows the piston rearward but by virtue of the groove milled in the mag tube, gas also fills the inside of the piston and creates a cushion between it and the mag tube it rides on.

High Standard autoloaders are gas operated and gas lubricated!


The gas bleeds out through tiny slits cut in each side of the piston.




This picture shows how the two mag tube would align with the brrel gas port. The way the gas system is designed, the mag tube not only has to have the right tolerance range for the piston, but the last few inches has to be oversized to seal the front of the gas port. The aftermarket tube I bought years ago has a slot milled with an o-ring the seals the front of the gas port. The factory tube is .004 oversized where it fits the gas port to provide a seal.

I usually clean then buff the magazine tube for about 3-4" with a scotchbrite pad....something that will polish the surface without removing metal.

The most important thing to remember about a High Standard autoloader is that they were designed to function without oil.

I know that sounds weird to some folks but High Standard said you can oil their autoloaders if you wanted to, but you should then wipe every part completely dry afterwards.

In at least three different places in the manual it clearly states that you should not use any lubricant around the gas system.

It's a tight tolerance gas system, designed to be self cleaning by literally blowing the debris out the action and into the housing.
If you add oil of any type to gas system, the gun will start jamming within a few rounds. The oil holds the powder residues that would normally be blown free and .001 clearance doesn't allow for any build up.

Run it dry with full power ammo and it will work every time....
run it wet or with mouse loads and you'll hate the gun.

This photo shows those clearances and how each mag tube used a different method of sealing the front of the gas port.


The piston fits the magazine tube with < .001 clearance!
Any replacement magazine tube has to be very close to 1.014" or you're going to bleed gas around the piston.


This is one area that is very easy to clean once you get this far.....
I usually just stick a small allen wrench through the two ports and roll it around. Use something that fits loosely and won't ream them out oversized.
(That might get it to working with skeet loads?!)


Inside the receiver.

And back together again for another 1000 rounds!



This sort of teardown is something Model 10 shotguns need about every 800-1000 rounds (or at the first sign of jamming).....once the shotgun has been broken in thoroughly it will go many hundreds of rounds before needing attention.

If the gun is new (or newish?) and the gas system is still tight, then it may need the gas piston and ports cleaned every 100 rounds or so.

I've blasted many thousands of rounds through this gun and it's still fun every time you take it out.

edit for additional pictures

Author:  oldolds442 [ Tue Jan 17, 2012 9:53 am ]
Post subject:  Re: High Standard Model 10 maintenance

remember seeing these in the law enforcement books and in some of the gun magazines when i was growing up. got good write ups if i remember correctly. they sure were futuristic looking. dont think i have ever seen one in person, though. what do they go for nowadays?

Author:  Fallschirmjäger [ Tue Jan 17, 2012 12:20 pm ]
Post subject:  Re: High Standard Model 10 maintenance

As a fellow 10B owner, I must applaud this post. I've learned things that I never even suspected.

p.s. That's NOT rust on the bolt, it's just an artifact of the lighting used. (Trust me; after seeing that pic I went over things with a very fine toothed comb.)

Author:  BioHazard [ Mon Jan 23, 2012 4:56 am ]
Post subject:  Re: High Standard Model 10 maintenance

I'm glad someone found this information useful.

To answer the PM from Ken:

On the magazine tubes..........
I don't think anyone is actively making extension tubes for these guns.

The first post shows why it's difficult as an aftermarket part, since the magazine tube is an integral part of the gas system. Many of the Model 10s that get bad functioning reports have had an extension tube installed by someone who didn't know that the dimensions were critical and that the tube had to seal the front of the barrel's gas port. Since these guns were designed and tuned for maximum loads, any gas leaks will guarantee FTE malfunctions. At the very least everything between the receiver and gas port has to have proper tolerance and most stock mag tubes are undersized for the Model 10.

From the gas port forward, the mag tube diameter isn't critical and a tube could be be made by extending the existing tube, but even that requires modifying the housing nut that also acts as the mag tube cap.
If extended, the mag tube has to pass through the housing nut that holds the top and bottom plastic housing together.


On the Kel Lite flashlight and mount.......

The Kel Lite flashlights for these things are now worth about $300 in mint condition to a collector. Even in mint condition, these are 40 year old technology and are not remarkable in any way when compared to newer LED and halogen lights. A few (very wealthy!) owners have paid to have their Kel Lites converted to modern lithium batteries and high lumen LED lighting. It may be original, but it's not too practical.

The Kel Lite attaches to three pins on the left side of the rear sight base.
That puts the light's switch right over your left hand on the forend.





The flashlight is secured by two 3/16" pins and a 10/32 thumbscrew. The pins deal with the recoil and the thumbscrew just secure it on the pins.

The flashlight has an aluminum rail with 5 holes. Two of these use flathead Allen screws to secure the base to the aluminum flashlight housing, two are 3/16" for the recoil pins and the center one is tapped for the 10/32 thumbscrew.


A cheaper and more realistic solution for good lighting is to use a solid Picatinny rail blank and drill and tap it for the Model 10's mount.....then you can take your pick of all the modern accessories offered today.

I used a 12" piece of blank Picatinny rail .61" thick (to get a little stand-off room) and cut it to the length I wanted then drilled and tapped it for the Model 10's thumbscrew mount.

The Model 10 B might be the perfect candidate for a Warhammer type rail that extends from the muzzle all the way back to the ejection port.

Just replace the rear sight base with 24" of rail....then you could mount a nice set of HK diopter front and rear sights! :)
(that's a dream of mine for this gun.)


that's Dufus, the "tactical" cat....
Like all things tactical, he's black and totally worthless for anything except trouble.


Hope this helps with your questions.

Author:  TNLightning [ Fri Aug 10, 2012 6:49 am ]
Post subject:  Re: High Standard Model 10 maintenance

BioHazard: More than "one" person has found your post useful. Myself for instance. I needed to have a better understanding of the science behind this gun. I've had a Model 10A that I purchased back in the early 1970's when I was in law enforcement. (No lasers in those days.)

Anyone who thinks that this shotgun is not a fine instrument has never had to choose an arm to use in a hurry. I came up on a robbery of a drugstore one night in my patrol unit, and had at my side a S&W .38 and a Model 10A. I had a Colt AR-15 hanging in the rack behind the front seat, but when I approached the front of the drugstore, one of the robbers rushed out yielding a .45 auto. I went to the Model 10 that I kept loaded with 00 Buckshot. I always kept one in the chamber (Which we were told NOT to do.) and it proved to be the right decision. The would be robber went down very quickly. There happened to be a doctor close by who witnessed the incident who was able to control the bleeding that the shotgun blast had caused. There was a second robber still in the drugstore who I captured using the AR-15. But the short design and manuverability of the Model 10, clearly gave me an advantage in that split second situation.

I'm retired now, and still have the Model 10 for a home defense weapon. I had noticed a feed jam recently after I installed a green laser on the barrel. Thanks to your post, I now know how to clean and correct the problem. THANKS!

Author:  BioHazard [ Fri Aug 10, 2012 1:07 pm ]
Post subject:  Re: High Standard Model 10 maintenance

I'm glad you found it helpful, sir.

Since so many of the Model 10s are now in museums or private collections for "display purposes only", I'm always happy to hear of another "shooter" out there, still serving on active duty.

I've heard rumors that some company (one source claimed it was SureFire?) is now making an LED replacement head for the Model 10A only, but I've never seen one and can not find anything specific about the who or where, just rumors posted on several forums.

Please post a picture of your 10A, if possible.

Author:  TNLightning [ Sun Sep 30, 2012 4:55 pm ]
Post subject:  Re: High Standard Model 10 maintenance

There is a picture of my 10A posted in the "other" category on this site. It's in a file called "WWN" which stands for "Worked When Needed" Sorry about the quality of the photo, it was taken with a cell phone camera. I've searched for a led replacement head also. So far... nada. But it is a small problem to overcome. I did however take the gun apart since I read your article. I also found a copy of the original High Standard Model 10A manual that my son downloaded for me, written back in 1967. It advises owners NOT to take the tube a spring out of the shotgun, but instead send it to a credited gunsmith or the manufacturer for in depth work. Anyway, I was able to clean the gas ports and she's working as well as she did when she was new. For the imediate cure on the light system, until someone comes up with a drop-in, or until I make one that works myself, I've ordered an NCStar 200 lum led with a pic mount & touch pad to "brighten up" the background more now that these old eyes are dimming. The in handle D cell was good in the old days when I was younger, but leaves a bit to be desired today.

Author:  BioHazard [ Mon Oct 01, 2012 1:01 pm ]
Post subject:  Re: High Standard Model 10 maintenance

I've seen the same warnings on disassembly of the mag tube and gas system.....
here's the potential problem:


The gas action and the recoil spring rides the mag tube.

In the front of the recoil spring is the gas piston. In the rear of the recoil spring is the spring base. In the picture above, the spring base is actually REVERSED from the way it should be installed on the mag should be installed with the small end towards the receiver and flanged end forward, in contact with the spring.

It is deceptively simple when assembling. The gun will go together either way, but it will not cycle properly with the spring base reversed, narrow end forward.....a Jam-o-matic.

Apparently, a lot of police armorers made that mistake while reassembling the M-10.

Author:  TNLightning [ Tue Oct 02, 2012 9:28 pm ]
Post subject:  Re: High Standard Model 10 maintenance

Yep. It reminds me of the flange on my Browning A5. It appears to be properly installed when it is actually reversed. It will still shoot a shell, but won't cycle and eject properly if it is in the worng posistion.

Author:  zavala [ Thu Oct 04, 2012 10:49 pm ]
Post subject:  Re: High Standard Model 10 maintenance

i still want one of those extended magazine tubes soooo bad

Author:  Fbahena [ Fri Oct 05, 2012 11:55 am ]
Post subject:  Re: High Standard Model 10 maintenance

That cat has mean intentions...

Author:  BioHazard [ Fri Oct 19, 2012 1:24 pm ]
Post subject:  Re: High Standard Model 10 maintenance

I recently heard someone say that although they loved their HS Model 10, the bullpup's trigger pull was atrocious, long and creepy at about 12 pounds.

Believe it or not, the M-10 has an adjustable trigger and it can be improved dramatically!
Mine has been lightened from 10 pounds to about 6-7 pounds and I shortened the take-up (free travel before sear engagement) to less than 1/8".

The picture below shows the relevant parts:
part # 68 is the trigger push rod,
part # 52 is the trigger return spring,
part # 82 is the sear nut.


Full sized M-10B schematic

On mine I disassembled the housing's trigger group and after searching through my spring assortment, I found a spring of similar length that was maybe 50-60% of the original's strength. I used this spring to replace the original trigger return spring (part # 52) and safely stored the original with the other OEM parts I've swapped.

At the rear of the trigger push bar, the sear nut (part # 82) is secured with LocTite or the 1965 equivalent. It requires a heat gun to release the locking agent and then the sear nut can be rotated on the threaded end of the push bar to adjust the takeup. My M-10B originally had over 1/4" of travel before it contacted the bobbed-off trigger spur.
I ran the sear nut out until this was about 1/8"....this was mostly trial and error but in the end, the nut was moved rearward about 1 & 2/3 complete turns. The sear nut is triangular, so you get 3 settings per revolution of the nut. Be sure to note the orientation of the sear nut (triangular peak UP towards the sear) and once you've found the right setting for your gun, apply RED LokTite to re-secure the sear nut on the trigger push bar.
I also applied a light coating of grease to the outsides of the twin push bars (part # 68) to reduce drag on the plastic pistol grip housing.

The result is a 6-7 pound trigger pull with 1/8" takeup and no creep.
This procedure also reduces the trigger reset distance.

Be sure to maintain an adequate safety margin if doing this adjustment.
Test the gun thoroughly to be sure the trigger is SAFE and that the crossbolt safety still blocks sear engagement when applied.

HS 10A manual

HS 10B manual

These are from the 1964 High Standard Police Shotgun Training Program

HS Police Shotgun Course Handout

HS Police Shotgun Course Supplement

Author:  ken65079 [ Thu Nov 01, 2012 9:46 pm ]
Post subject:  Re: High Standard Model 10 maintenance

BioHazard: Thank you for sharing your knowledge on this unusual weapon. I recently purchased a Model 10B. After comparing it to other pictures, I’ve come to the decision the carrying handle has been abused at one point as it’s slightly bent down towards the receiver. Is there a way to remove the handle and straighten the support?

I’m still looking for the magazine extension or a gunsmith that can fabricate one for me so any and all suggestions would be appreciated. Thank you again for your response and expertise. Ken

Author:  BioHazard [ Fri Nov 02, 2012 2:49 am ]
Post subject:  Re: High Standard Model 10 maintenance

It's probably more likely that someone removed the carry handle at some time and reinstalled it without the tension spring.

The rear sight block is aluminum, but the carrying handle link is steel. If the link of the handle is bent, it can probably be flattened back out.

The carrying handle is mounted to the rear sight block with an allen bolt, but between the handle and the rear sight block is a "tension spring". When the allen bolt is tightened down, the carrying handle can still flex about 10 degrees IF you push down on it. The tension spring holds it parallel to the receiver at rest but allows it to flex towards the rear if any pressure is applied. The design keeps it rigid and parallel to the receiver when supporting the gun, but flexible in the opposite direction.

The only other possibility is the allen bolt is loose and not holding the handle against the tension spring?

It should be an easy fix either way.....
the carrying handle tension spring (part # 74 on the Model 10-B exploded view in the owner's manual) is still available from GunPartsCorp!

On the link below, scroll to the bottom of the page to the Non Illustrated parts (NI)....
the carrying handle tension spring is listed for $2.90. ... catid=8495

They also have the remaining Model 10 4 round magazine tubes listed.....
buying two of these and having a good welder connect them is the best option available for an extended tube, unless you just stumble on one in some old gun shop. At one time maybe 40 years ago, Choate made some extended mag tubes for the Model 10.

Unfortunately all the forend caps are gone so you would have to fabricate one of these. The forend cap from a Sears Model 66 or a High Standard C1200 might work....these are the original shotguns the Model 10 was derived from. Fallschirmjager, another Model 10 owner on this forum might be of some assistance, since he actually went this route.
The picture of his extended tube is posted above in this thread.

I would not recommend using any of the original parts on your gun for this sort of them in case you decide to sell it some day or in case your modification doesn't work properly...that's always a risk.
Most collectors prefer all original parts and most will pay extra for that.

Good luck!

Author:  BioHazard [ Sat Jan 12, 2013 6:18 am ]
Post subject:  Re: High Standard Model 10 Bullpup Maintenance

When I made the rail to replace the old Kel-Lite on my 10B, I wanted to figure out a way to mount a scope or red dot sight.


My first thought was to drill and tap the flat between the two rail segments and mount a short Magpul rail there, but I recently found a 90 degree offset that seemed like it might be worth trying. It's mounted on the short segment on the right side of the gun.


The offset 90 is taller than I would have liked, but with the optic removed the base is ~ 1/2" lower than the iron sights plane. It's also about 1/4" to the right of the gun's centerline, but it should be close enough for shotgunning!


If the 90 degree rail adapter ($18 by Lion Gears)... was 1/2" lower I'd be able to see the iron sights at about 6-7 o'clock in the red dot's window. The rail base is mounted the right distance to also allow the use of an extended eye relief pistol scope for shooting slugs at extended range.


The optic I'm going to try out today at the range is an old LaserAim Grand Illusion. It's BIG!... (52mm) but it's stood up to .223 and .308 recoil over the it get's a REAL test.


The HS Model 10s already have a futuristic look but now it almost looks like something Stargate Command might use? :)

The thing I like most about it is with a turn of the thumbscrew, the rail, light, shell carrier and optic all come off the gun in one piece, leaving a small AA light and laser on the mag tube.

It's our monthly 100 yard slug shoot at the range today and I'm eager to try it out.

Author:  Svtom [ Fri Mar 20, 2020 4:14 pm ]
Post subject:  Re: High Standard Model 10 Bullpup Maintenance

I realize this is a very old thread,but so is my 10B.(ME,too,for that matter.)
I have had my10B for a long time and was wondering what if any collector value it may have.
I'm not wanting to 'cash in' on it ,as it were,by selling it. But rather I was wondering if anyone has tried to use the 10B,or 10A shell on a easier-to-find parts for 12 gauge auto. Something such as a 1100 or say,a Mossberg 930. This without changing or modifying the gun or parts so it could be returned to original form whenever. Kinda like putting mags on your vintage Mustang,but not cutting out the wheel wells..TIA,if anyone is listening. :-D

Author:  pakieser [ Thu Apr 23, 2020 11:22 am ]
Post subject:  Re: High Standard Model 10 Bullpup Maintenance

As a new 10B owner, I'm grateful for this thread. Here's mine:


Svtom wrote:
I realize this is a very old thread,but so is my 10B.(ME,too,for that matter.)
I have had my10B for a long time and was wondering what if any collector value it may have.

For what it's worth I picked mine up for $575. That took a lot of patient wating and watching on Gunbroker. I've seen them for as high as $1200, but those are in excellent condition. Mine was missing the carrying handle and had some wear, but looks good and functions flawlessly.

One thing I have been kicking around is converting mine from a 10B to a 10A. I can get the flashlight housing and was considering building it with a newer flashlight inside.

If you wanted to try a build with a different gun, you can get most of the parts from Numerich.

Author:  Ezra Smack [ Thu Apr 23, 2020 9:04 pm ]
Post subject:  Re: High Standard Model 10 Bullpup Maintenance

What is the trigger pull like on these things? My limited experience with bull pup shotguns has been that the trigger linkage results an an atrocious pull.

Author:  pakieser [ Mon Jul 13, 2020 2:23 pm ]
Post subject:  Re: High Standard Model 10 Bullpup Maintenance

OK revisiting this thread -

I took an old Maglite knock-off and I'm fabricating a fake Kel-Lite for my gun. I've also found a carrying handle for it. It appears that 7/8" motorcycle grips will fit it. I've ordered one and we'll see.

Has anyone seen a modification to lock the buttplate and prevent it from rotating? Yes I know it's a neat design idea but for my purposes I'd like to be able to lock it in place. I was thinking of installing a set screw where the detent pin is, which would allow me to lock it down and could also be used for disassembly.

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