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Discussion Starter · #1 ·
Does the 17" bbl on the 21 make the cyclic rate on a 21 run faster than if you had a 21" bbl?
 

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HK 21 Barrel length

No it doesn't... No change with either 17" or 21" HK barrel...

If you want the cycling rate changed on the HK 21 you must buy different locking pieces for the rate of fire effect...

17 locking piece to reduce rate of fire

Standard # 9 HK 21 locking piece for higher rate of fire...
 

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there are a few things that make the rate of fire go up or down.
to make it so you can see and feel it.

the locking piece is only part of it. you also have the recoil spring.

you have 2 types of recoil springs that are made to run with 3 types of locking piece's

lets start with the first set of parts. (Hk21 1960's gun)
and say this would be the base for the Hk21 and a 950rd a min Gun.
**note the Hk21 recoil spring is about 12 to 15lbs stronger then the Hk21E recoil spring)even with them saying it's 10lbs more..

this locking piece and the heavy recoil spring of the Hk21 work well with ea other and most ammo. thats on the nato side of good ammo.
and the Hk21 feed mech.

you then have the Hk21E locking piece and the Hk21E recoil spring.
this 2 parts are made to work with ea other in a diff feed mech.(Hk21E) but do work in a older Hk21 feed mech with Good ammo. this will give you a slower rate of fire..this and the Hk21E buffer will tame the Gun down a bit. on recoil.. and Give you a slower rate of Fire..about 800rds a min.
but remember you are moving a lighter parts in a Hk21E then you are in a Hk21. and a diff feed mech.

and the recoil is moving more mass on a Hk21 then the Hk21E
this in turn make's it seem like. it Kicks less. and in fact slows down the rate of fire..also. but it's just not the locking Piece.

you want the gun to rip out a belt?
and your gun is made to run with Hk21E back end?

load up a Dm1 belt Made to fit a Hk21
install a reg HK21 recoil spring on a Hk21E recoil rod
install that with a reg Hk21 locking piece..and shoot.

now do the same with a #17 locking piece and see the diff.

now go have fun

Note: you will get diff rates of fire with Diff trigger packs
and reg sears.. but you will see a diff in how the gun works. and runs...aka FAST AND FASTER
 

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Intersting. I have #9 locking piece installed in my RTDS HK21 and Ralph told me that it is slower than a #17. Is the #9 the standard 21 locking piece?

Also, Ralph mentioned that the locking piece is a Pain in the @$%# to change. Do you have any tips on doing this?

Thanks,

Andreas
 

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Intersting. I have #9 locking piece installed in my RTDS HK21 and Ralph told me that it is slower than a #17. Is the #9 the standard 21 locking piece?

Also, Ralph mentioned that the locking piece is a Pain in the @$%# to change. Do you have any tips on doing this?

Thanks,

Andreas
just swap out. when cleaning the gun it's easy..(check your gap before running the gun!)after you swap out parts!

the locking piece sets how much force. is used to unlock the bolt and run the gun.. and at what time.. it can also make the gun run slow or fast.. but as you speed the gun up. you must have the right parts to run the gun fast.. a better recoil spring and buffer!

Hk21E parts(locking piece) fit in a Hk21. but are made to run a diff feed mech. recoil spring
and Buffer.. so you should have the right parts from ea Gun. in a combo that work right for what you want to do.

it's just like any thing you do.. the right tools for the job.

you will see that the Hk21 is a fine Gun. i use mine in 3 gun shoots in the long gun part of the shoots. and it has never let me down...some of the guys snivel about it..(it's not mag fed)..lol ..but hey. it's all about the right tools for the job..and having a blast doing the Job!..right?
 

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HK 21 Operation...

Ryan

Did you ever perform any measurements or have any guess as to how much the ROF was reduced by using the 17 unit?
Sorry for the delayed reply...

Yes I have Ed, several times to speak of...

A good bolt gap gauge and field testing is all that's required...

The # 17 HK 21 locking piece reduces the rate of fire down by 300 rnds per minute...

The # 9 HK 21 locking piece is the current factory 21 locking piece installed on the HK 21 guns... Higher rate of fire @ 950 rounds per minute...

The # 17 locking piece allows you to enjoy the shooting comfort of the HK 21 with-out the beat down effect from the recoil system...

I recommend having both locking pieces at your disposal for different rates of fire...
 

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Thanks for the info Ryan.

Sounds like the #17 would definitely be the way to go to extend the life of the gun and be controllable.
 

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also install a Hk21 spring on a 21E recoil spring rod.
after all if ya want it to last (the gun) then go all out.
this makes the gun feel a bit more perky..when shooting
 
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