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" barrel....you'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