S12 Knoxx Spec-Ops testing passed

[gregmeboe@gmail.com 3]

I bought the pistol grip-only Knoxx breachersgrip off Gunbroker and hung it on the back of an unconverted S12. A full-length Knoxx Spec-Ops stock was also tested. This required filing, drilling and tapping the supplied aluminum Mossberg adapter block.

 

This gun functions perfectly and recoil is noticeably reduced. All video results at my channel page: http://www.youtube.com/user/TheMysticSmoke

• Birdshot -
  
  
• Slugs -
  
  
• One-handed 3" Magnum -
  
  

Knoxx expressly warns against using their Spec-Ops family of stocks on any semi-automatic shotgun. The unstated implications are that the gun will either not cycle or will become a machinegun. This may have come from their own testing using conventional American autoloaders, but the Saiga is a different animal. I have attempted to put forth a testing regimen which will push the Knoxx-equipped S12 to its functional limits. After reading through the testing matrix attached below, do you think there are additional tests which should be done?

 

Technical mounting details: This is a temporary installation for testing purposes. The Mossberg adapter is nearly the same width as the Saiga receiver. Therefore two compression interface mounting points are created on the lower outer rear edges of the receiver. A long 1/4-20 screw descends from the tang into the adapter. I drilled a hole in the rear face of the Saiga trigger guard for a 1/4-20 hex screw which goes rearward into the adapter. The two screws pull the adapter snug up against the rear of the Saiga receiver to bind the adapter tight. It remains tight after 100 rounds of varying strength, with some compressive deformation at the outer edges of the aluminum adapter. Since only the very outer corners touch this is to be expected. If I had access to a mill then life would be perfect.

Note that the Knoxx axis angle matches the bottom of the receiver (3 degrees downward cant?), instead of parallel to the barrel. With additional work this could be changed to zero degrees in the future. Currently the cheekweld on the Knoxx bare tube is just right for using the stock crappy iron sights.

Testing approach:

Result Scenarios: Gas operated autoloading: Test scenarios were designed to provoke failure of the autoloading mechanism. Four failure modes were envisioned:

1. Failure to Unload - After combustion, the bolt is unable to withdraw the case out of the breech to reach the ejector.
   
2. Failure to Eject (FTE) - The bolt has insufficient rearward momentum to throw the case out of the receiver (stovepipe).
   
3. Failure to Load - The subsequent cartridge is not picked up from the magazine and chambered fully.
   
4. Machinegun - This type of failure would have ended the testing program. The hammer is not held back but slams forward with the bolt, repeating the combustion cycle.
   
5. Normal Function - The spent case is completely ejected and a new cartridge is loaded. The hammer is held back, waiting for the user to release their finger from the trigger, and then pull the trigger again to start the next combustion cycle. (This result is noted as "Held" on the matrix). This is the way an ideal semi-automatic action should behave under normal operating conditions.
   

Failures 1 and 3 were considered unlikely, and therefore were not included on the testing matrix. Failure 2 is included since it's a known issue on these guns. Failure 4 is the biggie: If this failure had occurred even once during these tests, I would have destroyed the adapter and not posted anything to the forum.

 

Parameter 1: Cartridge type: Four shell types were planned, although I seemed to be out of #7 Birdshot when looking through the safe so it was down to three.

1. 1 oz Slug - Winchester Super X from Wal-Mart. This load is quite uncomfortable for me to shoot on a bone-stock S12. This is the first set of tests shown on the matrix (S1-S6).
   
2. 3" Magnum 00 Buckshot - Remington from Wal-Mart. A very heavy & hard-hitting load. I would normally not elect to shoot this due to the high level of recoil. I expected that any machinegun failures would occur with this heavy load (thankfully none did). This is the second set of tests on the matrix (K1-K6).
   
3. #8 Birdshot - El cheapo Federal from Wal-Mart. This is a light recoiling clay target load. This is the last set of tests on the matrix (W81-W86). Note, when using Birdshot and gas setting "1-restricted" an FTE should be anticipated. So tests (W84-W86) resulting in FTE did not constitute unplanned failure, as the instruction manual dictates use of gas setting "2-full" with low-power loads.
   

Parameter 2: Gas valve setting: This gun started life as a 2-hole partially occluded Vodka Special, and was warrantied by CGW who drilled a single larger gas port. Thanks guys! Since then it has cycled just fine. With the "stock" stock, this gun will FTE on low brass birdshot if the gas plug is set to "1-restricted." This is normal and acceptable. Nonetheless, setting "1-restricted" was a part of the testing routine, just for kicks.

 

Parameter 3: Trigger pull: Understanding that some other users are quite adept at provoking recoil-induced repeating firing action (bump firing), three levels of trigger pull were documented:

1. Fast + Heavy trigger - User pulls the trigger with maximum force and speed
   
2. Regular pull - User pulls the trigger with moderation
   
3. Lightest and slowest - User pulls very slowly and gently
   

FWIW I have never "bump fired" a weapon before.

 

After printing up a testing matrix we headed out to the woods. With the Knoxx Breachersgrip fitted (pistol grip only), aiming was accomplished using a $35 Chinese green laser (http://www.dealextreme.com/details.dx/sku.13137), Deal Extreme Green Gun Laser.

Once testing was done we had some fun videotaping silly stuff like rapid fire and one-handed shooting. LOL

 

Since then I bought the full-length Knoxx Spec-Ops stock and tested it at the range. Video results at the above link.

Next step is to take the full-length Spec-Ops S12 to the woods and do a side-by-side comparison with another S12 which was converted using ACE folding stock and small AK-style plastic pistol grip.

 

In all cases of all tests, Failure 4 (machinegun) was never observed. If testing continues to go this well, a subsequent step would be to modify the receiver of the S12 to mount the Knoxx family of stocks in the converted (forward) position.

 

Does anyone in the Seattle area have a high-speed camera they'd be willing to use for this testing, to compare the relative position of the bolt vs. the recoil slide during the firing cycle? The recoil slide completes its full course of travel quicker than the bolt, but how much quicker? PM if yes.

 

Any thoughts on additional tests with the current configuration?

[gregmeboe@gmail.com 3]

Here's the testing matrix:

[joebanda1213 59]

Very thorough lab report... Seems to work well enough.

 

One Question.. Is it worth while and cost to buy one of these and if possible like you said you would like to do. Cut the reciever so you can install the stock/pg combo with forward converted trigger group. When you can buy and install a pistol grip and a separate stock with one of the enindine recoil reducing tubes inside.

 

I wouldnt think one would significantly absorb more recoil then the other.

 

Its cool though that your exploring new options for us.

[Mullet Man 2,114]

Excellent job on all the homework and information but i end up with a one word question...

 

Why?

[Bean.223 365]

Excellent job on all the homework and information but i end up with a one word question...

 

Why?

 

 

Thats what they asked Columbus my friend!!!

 

Its a great looking mod. Nice Idea.

[tover26 18]

Why? So that you can have a one-handed Saiga 12 gauge and save on stock length or folding stock bulk.

 

WTG!

[rugerglocker 2]

Honestly the s-12 doesn't have that much recoil for a shotty, at least to me. In your videos it didn't look like the knox helped much, you were kinda all over the place, maybe cuz you were shooting from a rest. Anyway, I don't mean to shit on your project but those are my thoughts.