How do you run m11/9 Closed bolt?

Gaujo

UZI Talk Supporter
Feedback: 10 / 0 / 1
Joined
Sep 11, 2013
Messages
4,149
Location
Raleigh, NC
I've heard for years you can do it, and I've got a early CFW full size bolt with a firing pin. How does one convert the system to closed bolt?
 

KickStand

UZI Talk Life Member
Feedback: 15 / 0 / 0
Joined
Jan 2, 2018
Messages
939
Location
USA
CoffeeFreak did it if I recall.
He might be able to chime in as he’s posted recently.
TheColtCollector might be able to help as well.
 

strobro32

UZI Talk Life Member
Feedback: 69 / 0 / 0
Joined
Sep 4, 2007
Messages
7,850
More than a few people did it, including me, but everyone of them said it was overly complicated and added no benefit in reduced recoil or ROF to the platform.

A closed bolt M11/9 system needs to let the sear drop a spring loaded block of steel onto a semi bolt or a spring loaded rear plate/ firing pin on closed bolt like a closed bolt mini Uzi system. I think coffeefreak had a cable linkage to drop a separate firing pin plate.

uzi-5218_1892_detail.jpg
 

Garrett

Well-known member
Feedback: 9 / 0 / 0
Joined
May 19, 2004
Messages
2,758
Location
Michigan
Best way might be to build it in a MAX-31. There is a lot more room in the receiver to fit a closed bolt setup. But then, that configuration already runs at a pretty good ROF with a steel bolt, with not much to be gained by using your W bolt.

As strobro notes, not a lot of advantage to the CB system in a subgun. The first round accuracy issue is way overblown at subgun distances.

The only reason I played with the CB setup was to be able to shoot another category at the KCR subgun match. In the MAX-31, CB vs OB feels pretty similar, with CB just slightly faster. The closed bolt setup in the Uzi is just stupid fast, which can be fun on occasion, but it runs so fast to cause reliability issues.
 

Garrett

Well-known member
Feedback: 9 / 0 / 0
Joined
May 19, 2004
Messages
2,758
Location
Michigan
And one clarification: Richard recently stated not to use (unmodified) CFW bolts in the MAX-31, due to the sear engagement surface on the bolt not being ground at the correct angle for how the sear engages on the 31.

For that matter, you would have to permanently modify the bolt to work in a closed bolt setup in the 31, which is not a great idea with that bolt.
 

Deerhurst

Registered User
Feedback: 0 / 0 / 0
Joined
Apr 27, 2020
Messages
866
Location
Oregon
Going closed bolt is something I do a lot with rewelds. It always increases complexity and reduces reliability compared to the original open bolt.

For a Mac conversion kit will run closed bolt only for the first round or in semi auto. In FA every round after the first round will be essentially open bolt as the striker will not wait for the bolt to close.
 

Gaujo

UZI Talk Supporter
Feedback: 10 / 0 / 1
Joined
Sep 11, 2013
Messages
4,149
Location
Raleigh, NC
Going closed bolt is something I do a lot with rewelds. It always increases complexity and reduces reliability compared to the original open bolt.

For a Mac conversion kit will run closed bolt only for the first round or in semi auto. In FA every round after the first round will be essentially open bolt as the striker will not wait for the bolt to close.
Thanks for all the feedback so far! Can you explain further what "the striker will not wait for the bolt to close" means
 

chili17

Moderator, FFL/SOT, UZI Talk Life Member,
Staff member
Feedback: 60 / 0 / 0
Joined
Jun 21, 2003
Messages
6,803
Location
North Texas
with the sear depressed the striker just follows the bolt closed
 

Deerhurst

Registered User
Feedback: 0 / 0 / 0
Joined
Apr 27, 2020
Messages
866
Location
Oregon
Thanks for all the feedback so far! Can you explain further what "the striker will not wait for the bolt to close" means
With the sear held down there is nothing to retard the striker so the striker will just follow the bolt forward. There is no disconnector in the Mac that functions in FA like there is in an AK or M16.

It'll be basically open bolt with more parts for everything after the first round due to the sear following the bolt.
 

Hey...

UZI Talk Life Member
Feedback: 14 / 0 / 0
Joined
Apr 10, 2016
Messages
3,304
Location
Atlanta
CF’s used the semi auto hammer (modified with an 2nd sear notch) and bolt.

The full auto trip was set up that when the bolt came forward and tripped, it would move linkage that released the hammer.

So the bolt would be closed as it trips the FA disconnect, hammer falls, and semi-auto firing pin hits the cartridge.

Thats the simplest I can describe it. I have nothing else to offer.
 

MitchWerbellsGhost87

Well-known member
Feedback: 5 / 0 / 0
Joined
Dec 11, 2022
Messages
493
Location
USA
With the sear held down there is nothing to retard the striker so the striker will just follow the bolt forward. There is no disconnector in the Mac that functions in FA like there is in an AK or M16.

It'll be basically open bolt with more parts for everything after the first round due to the sear following the bolt.
Not to derail the thread but I was just recently wondering if the Intratec 9 would function reliably as a closed bolt full auto if someone were to disable the disconnector. it’s a striker fired gun, same floating firing pin on an SMG FCG kinda set up as a semi auto Uzi, so this would probably apply to the Uzi as well. I know hammer follow doesn’t produce reliable full auto function but what about “striker follow”? Do semi auto closed bolt striker fired guns function as closed bolt full auto (on the first round) if the trigger disconnect process is eliminated from the firing sequence?
 

Garrett

Well-known member
Feedback: 9 / 0 / 0
Joined
May 19, 2004
Messages
2,758
Location
Michigan
Not to derail the thread but I was just recently wondering if the Intratec 9 would function reliably as a closed bolt full auto if someone were to disable the disconnector. it’s a striker fired gun, same floating firing pin on an SMG FCG kinda set up as a semi auto Uzi, so this would probably apply to the Uzi as well. I know hammer follow doesn’t produce reliable full auto function but what about “striker follow”? Do semi auto closed bolt striker fired guns function as closed bolt full auto (on the first round) if the trigger disconnect process is eliminated from the firing sequence?
Possibly.

One of the differences between the semi- and full-auto Uzi bolt is the absence (semi) or presence (full) of the lower lip on the breech face. You can see pictures of the differences in the Uzitalk library.

If the firing pin is in the forward position as the round is chambered, the protruding firing pin will catch the cartridge rim as it slides up the breech face, if there is no lower lip. On a full auto, the rim rides over the lip, then snaps into place just as the bolt closes fully, smashing the primer into the firing pin.

The TEC-9 would need a breech face with a lower lip to function reliably as a full auto. I haven’t ever seen a f/a TEC-9, so I can’t say for sure how they were set up.
 

Deerhurst

Registered User
Feedback: 0 / 0 / 0
Joined
Apr 27, 2020
Messages
866
Location
Oregon
Not to derail the thread but I was just recently wondering if the Intratec 9 would function reliably as a closed bolt full auto if someone were to disable the disconnector. it’s a striker fired gun, same floating firing pin on an SMG FCG kinda set up as a semi auto Uzi, so this would probably apply to the Uzi as well. I know hammer follow doesn’t produce reliable full auto function but what about “striker follow”? Do semi auto closed bolt striker fired guns function as closed bolt full auto (on the first round) if the trigger disconnect process is eliminated from the firing sequence?
It would likely run fine. I've even had closed bolt striker fired guns runaway just due to a stuck firing pin. Ran fine. One actually ran more reliability than it ever has as a closed bolt semi! Surprised the hell out of me. Moral of that story is do not forget the firing pin bushing.

On FA a closed bolt striker gun will be closed bolt for the first round or every round on semi but run as open bolt on every round after the first on FA.

With striker follow through you have weight on your side. Most striker guns I've played with have full FP protrusion with the striker forward. Usually a firing pin by itself self does not have enough mass to pop a primer by interia.

Converting a striker gun to FA is usually pretty easy. Making it select fire is harder. Things like a Glock may be more difficult. Things like an Uzi is likely really easy.

I probably shouldn't have to say this but without the proper SOT and paperwork and approvals, etc you should not be doing these things intentionally. If you are doing a build and you have a FA issue you should be fixing the issue and preventing it from happening again.
 

MitchWerbellsGhost87

Well-known member
Feedback: 5 / 0 / 0
Joined
Dec 11, 2022
Messages
493
Location
USA
It would likely run fine. I've even had closed bolt striker fired guns runaway just due to a stuck firing pin. Ran fine. One actually ran more reliability than it ever has as a closed bolt semi! Surprised the hell out of me. Moral of that story is do not forget the firing pin bushing.

On FA a closed bolt striker gun will be closed bolt for the first round or every round on semi but run as open bolt on every round after the first on FA.

With striker follow through you have weight on your side. Most striker guns I've played with have full FP protrusion with the striker forward. Usually a firing pin by itself self does not have enough mass to pop a primer by interia.

Converting a striker gun to FA is usually pretty easy. Making it select fire is harder. Things like a Glock may be more difficult. Things like an Uzi is likely really easy.

I probably shouldn't have to say this but without the proper SOT and paperwork and approvals, etc you should not be doing these things intentionally. If you are doing a build and you have a FA issue you should be fixing the issue and preventing it from happening again.

Makes me wonder why I never see any closed bolt full auto TEC-9s or Uzi conversions on the market. Always figured that “striker follow” was unreliable or something. Guns like the tec-9 would be extremely easy to convert to closed bolt full auto assuming that the striker following the bolt would result in reliable full auto operation, makes me wonder why everyone would take the time to convert the guns to open bolt for full auto function, especially in a gun that’s not selective fire.


I personally have never seen a striker fired closed bolt M11/9 set up, but I’m very curious to see it. I have see the closed bolt select fire UZIs, the micro is a closed bolt SMG, IMI even offered this as an option with the mini-UZI and may have offered bolts for the full size as well, but I can’t say I’ve ever seen it done with a MAC.

Only striker fired MAC I’ve ever seen is the semi auto Jersey arms partisan avenger, which was redesigned as a striker fired semi auto to get ATF approval because they had already manufactured the open bolt lower receivers and didn’t wanna have to trash it all.
 

Doobis

Well-known member
Feedback: 2 / 0 / 0
Joined
Jul 22, 2018
Messages
146
I would be highly interested in something like this on a CFW bolt. My only real complaint about the CFW bolt in my M11/nine is that is HEAVY (duh). Myself and others noticed that the first shot can dip pretty hard if you aren't prepared for it. The weight of that bolt going forward dips the gun a noticeable amount. At approx 20 yards on an USPSA target aiming at the center of the A zone the first shot can be as low as the D zone then recoil walks the gun back up.

With a little experience you can easily mitigate this. Mine is an A bolt so I don't actually have a way to replace the firing pin but if I could Id buy something like this.
 

medphys

UZI Talk Life Member
Feedback: 62 / 0 / 0
Joined
Apr 9, 2008
Messages
7,511
Location
NW Ohio
Another issue with CB conversions of an OB is that the first round is a doozy! They basically run as a CB for the first round, then as an OB during full-auto fire. That first round doesn't enjoy the OB benefit of the round firing just prior to bolt being fully closed (I forget the exact term) which reduces recoil. I believe the CB Max31 had a long enough receiver to minimize that problem.

That first round on my CB was not fun.
 

SecondAmend

Well-known member
Feedback: 13 / 0 / 0
Joined
Apr 3, 2007
Messages
1,722
Another issue with CB conversions of an OB is that the first round is a doozy! They basically run as a CB for the first round, then as an OB during full-auto fire. That first round doesn't enjoy the OB benefit of the round firing just prior to bolt being fully closed (I forget the exact term) which reduces recoil. ...
The term generally used to describe the round firing just prior to the bolt being fully closed is advanced primer ignition (API).
 

Galil#1

Well-known member
Feedback: 1 / 0 / 0
Joined
Jun 21, 2018
Messages
706
Not to jack too much... be more interested IF possible to have last round open bolt... for MAC/and or full size UZI SMG?
 

Please Visit our Sister Sites Below

Sister Board - Sturmgewehr Sister Board - MachinegunBoards


Please consider becoming an UZI Talk Supporter
Top