Warning

 

Close

Confirm Action

Are you sure you wish to do this?

Confirm Cancel
BCM
Durkin Tactical Franklin Armory
User Panel

Site Notices
Maxim Defense RDB review (Page 2 of 11)
Page / 11
Link Posted: 6/19/2023 8:01:26 AM EST
[#1]
Gentlemen, i stand corrected.  Thanks for the responses.
PWS
Link Posted: 6/19/2023 10:15:50 AM EST
[#2]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Silverbear_51:
Gentlemen, i stand corrected.  Thanks for the responses.
View Quote

No worries!  I'm just passionate about that topic and I certainly didn't mean to imply I was directing my displeasure toward you in any way. đź‘Ť
Link Posted: 6/19/2023 9:25:36 PM EST
[#3]
Interesting article here.

https://www.thefirearmblog.com/blog/2016/06/20/operating-systems-101-api-blowback-operation/

My understanding is that the issue for us is that the ATFs determination of open bolts being “easily convertible” eliminated API from civilian ownership (NFA excepted).

Link Posted: 6/19/2023 10:04:21 PM EST
[#4]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By JustaDeplorable76:  Interesting article here.

https://www.thefirearmblog.com/blog/2016/06/20/operating-systems-101-api-blowback-operation/

My understanding is that the issue for us is that the ATFs determination of open bolts being “easily convertible” eliminated API from civilian ownership (NFA excepted).
View Quote


https://www.thefirearmblog.com/blog/2016/06/20/operating-systems-101-api-blowback-operation/

Czech ZK-383 Transferable Submachine Gun
Link Posted: 6/19/2023 10:37:25 PM EST
[#5]
Somebody please explain how API works with a fixed firing pin. I can't get my head around the primer being ignited without the case being seated in the chamber. You can tell I've never studied subguns.
Link Posted: 6/20/2023 2:55:17 AM EST
[#6]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:
Somebody please explain how API works with a fixed firing pin. I can't get my head around the primer being ignited without the case being seated in the chamber. You can tell I've never studied subguns.
View Quote

It doesn't. API is used only in large guns, not small arms.  API is an engineered solution allowing large guns, like automatic cannons, to use blowback operation with a much lighter (1/10) than normal bolt, reducing the overall weight of the entire gun.  It requires firing pin/chamber/ammunition design engineered specifically for API.  Timing of the moment of firing is critical for API to work.  

SMG's are simple blowback, nothing else.  All the references who claim SMG's use API are conflating "advanced primer ignition" as an engineered solution, and unintentionally "firing a cartridge slightly out of battery" because the cartridge stops short due to chamber fouling or other unintended reason.   Open bolt SMG's must be treated by engineers as closed-bolt from the perspective of blowback bolt mass due to the prospect of hang-fires or delayed ignitions resulting from mass produced cheap ammo.  If the cartridge fires slightly out of battery before fully chambering, it's an accident, not part of the engineered design of the SMG.

If API were being used in SMG's, we'd be looking at bolt/buffer masses around 2oz. TOTAL, not the typical 22oz.

Link Posted: 6/20/2023 4:06:06 AM EST
[Last Edit: Droppoint] [#7]
Originally Posted By JustaDeplorable76:
Interesting article here.

https://www.thefirearmblog.com/blog/2016/06/20/operating-systems-101-api-blowback-operation/

My understanding is that the issue for us is that the ATFs determination of open bolts being “easily convertible” eliminated API from civilian ownership (NFA excepted).

View Quote

That article with accompanying video is full of misinformation and is wrong in so many ways, it's very concerning.

API utilizes a hooded chamber that supports and encloses the entire rebated-rim cartridge, a bolt that inserts into the end of the chamber, and ammunition tailored for API.  API is extremely ammunition sensitive because of the need to balance the blowback forces with an ultra-light bolt.  Again, the whole point of API is to use an ultra light bolt, considerably reducing the weight of a blowback cannon.  Open bolt SMG's use full-weight blowback bolts.  That alone should be enough damning evidence against the supposed use of API in SMG's to settle the matter.



In just one example of ignorance, the article states "Note how the ignition of the cartridge precedes the breechblock’s stop against the barrel..." and then shows a dark slow-mo video that really doesn't show anything. The ZK-383 obviously isn't firing using API - it lacks the engineered design, components, and rebated rim ammo do do so.

Here's what is actually happening:  In a simple blowback open bolt SMG the bolt and barrel face should NOT make significant contact during the firing cycle. The cartridge headpaces on the cartridge mouth. The bolt should be stopped slighly rearward from the barrel face by the cartridge, which acts as a "pillar" between the chamber end lip and the breechface.  When the cartridge mouth stops at the chamber's end lip, the bolt continues forward and the firing pin crushes the primer, without the breechface hitting the barrel face.  If the breechface hit the barrel face, the cartridge is sitting too deep in the chamber.

So yes, the cartridge is firing before the breechblock stops against the barrel, but not because of API.  It's because they're held apart by the protrusion of the cartridge case, as designed.

Yikes!  Talk about getting way off topic!   Let's get back on topic...

Still no word yet on shipping from Maxim.
Link Posted: 6/20/2023 5:40:40 AM EST
[#8]
Between Maxim and MEAN Arms I am developing a serious case of FARBB (Firearm Accessory Related Blue Balls).  I sure hope someone ships something soon.  Looking forward to some actual test results.
Link Posted: 6/20/2023 6:49:07 AM EST
[#9]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Silverbear_51:
Between Maxim and MEAN Arms I am developing a serious case of FARBB (Firearm Accessory Related Blue Balls).  I sure hope someone ships something soon.  Looking forward to some actual test results.
View Quote

I think you mean RDBBB (Radial Delayed Blowback Blue Balls)

In all seriousness hopefully one of you who ordered this will get it soon and be able to test it out and let us know what you think.
Link Posted: 6/20/2023 8:03:48 AM EST
[Last Edit: amphibian] [#10]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Droppoint:

That article with accompanying video is full of misinformation and is wrong in so many ways, it's very concerning.

API utilizes a hooded chamber that supports and encloses the entire rebated-rim cartridge, a bolt that inserts into the end of the chamber, and ammunition tailored for API.  API is extremely ammunition sensitive because of the need to balance the blowback forces with an ultra-light bolt.  Again, the whole point of API is to use an ultra light bolt, considerably reducing the weight of a blowback cannon.  Open bolt SMG's use full-weight blowback bolts.  That alone should be enough damning evidence against the supposed use of API in SMG's to settle the matter.

https://i.imgur.com/fW2hi4L.jpeg

In just one example of ignorance, the article states "Note how the ignition of the cartridge precedes the breechblock's stop against the barrel..." and then shows a dark slow-mo video that really doesn't show anything. The ZK-383 obviously isn't firing using API - it lacks the engineered design, components, and rebated rim ammo do do so.

Here's what is actually happening:  In a simple blowback open bolt SMG the bolt and barrel face should NOT make significant contact during the firing cycle. The cartridge headpaces on the cartridge mouth. The bolt should be stopped slighly rearward from the barrel face by the cartridge, which acts as a "pillar" between the chamber end lip and the breechface.  When the cartridge mouth stops at the chamber's end lip, the bolt continues forward and the firing pin crushes the primer, without the breechface hitting the barrel face.  If the breechface hit the barrel face, the cartridge is sitting too deep in the chamber.

So yes, the cartridge is firing before the breechblock stops against the barrel, but not because of API.  It's because they're held apart by the protrusion of the cartridge case, as designed.
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Droppoint:

That article with accompanying video is full of misinformation and is wrong in so many ways, it's very concerning.

API utilizes a hooded chamber that supports and encloses the entire rebated-rim cartridge, a bolt that inserts into the end of the chamber, and ammunition tailored for API.  API is extremely ammunition sensitive because of the need to balance the blowback forces with an ultra-light bolt.  Again, the whole point of API is to use an ultra light bolt, considerably reducing the weight of a blowback cannon.  Open bolt SMG's use full-weight blowback bolts.  That alone should be enough damning evidence against the supposed use of API in SMG's to settle the matter.

https://i.imgur.com/fW2hi4L.jpeg

In just one example of ignorance, the article states "Note how the ignition of the cartridge precedes the breechblock's stop against the barrel..." and then shows a dark slow-mo video that really doesn't show anything. The ZK-383 obviously isn't firing using API - it lacks the engineered design, components, and rebated rim ammo do do so.

Here's what is actually happening:  In a simple blowback open bolt SMG the bolt and barrel face should NOT make significant contact during the firing cycle. The cartridge headpaces on the cartridge mouth. The bolt should be stopped slighly rearward from the barrel face by the cartridge, which acts as a "pillar" between the chamber end lip and the breechface.  When the cartridge mouth stops at the chamber's end lip, the bolt continues forward and the firing pin crushes the primer, without the breechface hitting the barrel face.  If the breechface hit the barrel face, the cartridge is sitting too deep in the chamber.

So yes, the cartridge is firing before the breechblock stops against the barrel, but not because of API.  It's because they're held apart by the protrusion of the cartridge case, as designed.
First of all, I agree with your definition of what an API configuration is.
Over 20 years ago when I got my first open bolt UZI SMG, someone on subguns.com 'corrected' me that the UZI is using API which I never understood since in order for the round to be fired, the case mouth would have to headspace at the end of the chamber...so the round must be fully in the chamber which doesn't match the definition of an API gun.
Back then, subguns.com was where all the experts posted and nobody seemed to correct this guy correcting me so I figured OK....  Maybe he is right and I just don't understand.
BTW, below is a picture I took from this book in my collection:

That picture is from page 8 of the book below written by Ian Hogg and John Weeks

I know Ian Hogg (now deceased) was a world renowned small arms experts.  Don't know about John Weeks.  
However it seems whoever wrote this first section titled 'Principles of Operation' got API wrong.

I think Ian McCollum of Forgotten Weapons has it right in his description here:
https://www.forgottenweapons.com/qa-7-video/
20:55   Submachine guns and Advance Primer Ignition (API)

All that said, I do want to re-iterate that an open bolt SMG has a much nicer recoil impulse than a closed bolt straight blowback.
A good example of this would be the UZI SMG fired in full auto in open bolt vs closed bolt.  I have full auto closed bolt configurations in my collection and the bolt weight is actually 3oz heavier in closed bolt but the recoil impulse on closed bolt sucks compared to the open bolt.  
On the open bolt UZI SMG, the bolt shouldn't be slamming into the trunnion until it has run out of ammo on an empty chamber.
Upon live fire, the round is detonated while the bolt is still going forward (but the round is still fully chambered, so it isn't API). This doesn't happen in the closed bolt version (full or semi) of the UZI and the recoil is much sharper on the closed bolt UZI's because of this.

It is a long winded answer and may be why many will just say, uh yeah it is API when it really isn't....
Yikes!  Talk about getting way off topic!   Let's get back on topic...

Still no word yet on shipping from Maxim.
+1...no word from Maxim either.
Link Posted: 6/20/2023 8:07:40 AM EST
[#11]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Mav3rick:

I think you mean RDBBB (Radial Delayed Blowback Blue Balls)

In all seriousness hopefully one of you who ordered this will get it soon and be able to test it out and let us know what you think.
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Mav3rick:
Originally Posted By Silverbear_51:
Between Maxim and MEAN Arms I am developing a serious case of FARBB (Firearm Accessory Related Blue Balls).  I sure hope someone ships something soon.  Looking forward to some actual test results.

I think you mean RDBBB (Radial Delayed Blowback Blue Balls)

In all seriousness hopefully one of you who ordered this will get it soon and be able to test it out and let us know what you think.
Yeah...the wait is killing me.
Link Posted: 6/20/2023 8:57:28 AM EST
[#12]
FWIW, the (.45 ACP, open bolt) Thompson submachine gun, with the M1 and M1A1 variants, presents a direct comparison of hammer fired (M1) v. fixed firing pin (M1A1) operations where the reciprocating mass is virtually identical (approx. 28.5 - 29 oz.).  Tests where the only change was swapping bolts have shown the the M1A1 variant generally results in about 15% lower rate of full auto fire for the same ammos.

In the case of the Thompson, the M1A1 variant was designed and produced to provide lower cost as the manufacturing was more simple and the parts count was reduced.

MHO, YMMV, etc.
Link Posted: 6/20/2023 9:48:19 AM EST
[#13]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By SecondAmend:
FWIW, the (.45 ACP, open bolt) Thompson submachine gun, with the M1 and M1A1 variants, presents a direct comparison of hammer fired (M1) v. fixed firing pin (M1A1) operations where the reciprocating mass is virtually identical (approx. 28.5 - 29 oz.).  Tests where the only change was swapping bolts have shown the the M1A1 variant generally results in about 15% lower rate of full auto fire for the same ammos.

In the case of the Thompson, the M1A1 variant was designed and produced to provide lower cost as the manufacturing was more simple and the parts count was reduced.

MHO, YMMV, etc.
View Quote


Just askin', how does an open bolt work in a gun with a hammer?
Link Posted: 6/20/2023 9:53:59 AM EST
[#14]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:


Just askin', how does an open bolt work in a gun with a hammer?
View Quote
Here is one example and since we are on AR15.com, relevant....
Colt LMG Open bolt:
https://john1911.com/the-open-bolt-m16-lsw-colt-model-950/
Link Posted: 6/20/2023 10:02:52 AM EST
[Last Edit: SecondAmend] [#15]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By amphibian:
Here is one example and since we are on AR15.com, relevant....
Colt LMG Open bolt:
https://john1911.com/the-open-bolt-m16-lsw-colt-model-950/
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By amphibian:
Originally Posted By hdcharlie:


Just askin', how does an open bolt work in a gun with a hammer?
Here is one example and since we are on AR15.com, relevant....
Colt LMG Open bolt:
https://john1911.com/the-open-bolt-m16-lsw-colt-model-950/

The (now discontinued) Alliance Armament and currently produced Lage Manufacturing AR mag pattern uppers are another example. ETA: Though not as directly on point as the Colt example.

MHO, YMMV, etc.  Be well.

Link Posted: 6/20/2023 10:59:56 AM EST
[#16]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:


Just askin', how does an open bolt work in a gun with a hammer?
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:
Originally Posted By SecondAmend:  FWIW, the (.45 ACP, open bolt) Thompson submachine gun, with the M1 and M1A1 variants, presents a direct comparison of hammer fired (M1) v. fixed firing pin (M1A1) operations where the reciprocating mass is virtually identical (approx. 28.5 - 29 oz.).  Tests where the only change was swapping bolts have shown the the M1A1 variant generally results in about 15% lower rate of full auto fire for the same ammos.

In the case of the Thompson, the M1A1 variant was designed and produced to provide lower cost as the manufacturing was more simple and the parts count was reduced.

MHO, YMMV, etc.


Just askin', how does an open bolt work in a gun with a hammer?


Hammer is tripped by the bolt closing - or in an API gun, at a predetermined point when the cartridge is in the chamber.
Link Posted: 6/20/2023 1:13:14 PM EST
[#17]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By SecondAmend:
FWIW, the (.45 ACP, open bolt) Thompson submachine gun, with the M1 and M1A1 variants, presents a direct comparison of hammer fired (M1) v. fixed firing pin (M1A1) operations where the reciprocating mass is virtually identical (approx. 28.5 - 29 oz.).  Tests where the only change was swapping bolts have shown the the M1A1 variant generally results in about 15% lower rate of full auto fire for the same ammos.

In the case of the Thompson, the M1A1 variant was designed and produced to provide lower cost as the manufacturing was more simple and the parts count was reduced.

MHO, YMMV, etc.
View Quote


I don't mean to be argumentative, but I don't see how an M1 could be converted to an M1A1, or vice-versa, just by changing bolts. In the exploded diagram I saw of the M1A1, it looks like the bolt mates right with the trigger, the same way as most of the really simple, open bolt designs I'm familiar with. There doesn't appear to be any hammer in the M1A1 trigger group, or any need for one.
Link Posted: 6/20/2023 1:19:08 PM EST
[#18]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By amphibian:
Here is one example and since we are on AR15.com, relevant....
Colt LMG Open bolt:
https://john1911.com/the-open-bolt-m16-lsw-colt-model-950/
View Quote


Ok, I suppose I should have asked that differently. How does a hammer work with an open bolt setup that has a fixed firing pin? What would be the point of the hammer?
Link Posted: 6/20/2023 1:29:32 PM EST
[#19]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:


Ok, I suppose I should have asked that differently. How does a hammer work with an open bolt setup that has a fixed firing pin? What would be the point of the hammer?
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:
Originally Posted By amphibian:  Here is one example and since we are on AR15.com, relevant....
Colt LMG Open bolt:
https://john1911.com/the-open-bolt-m16-lsw-colt-model-950/


Ok, I suppose I should have asked that differently. How does a hammer work with an open bolt setup that has a fixed firing pin? What would be the point of the hammer?


Not all open-bolt designs have fixed firing pins.  Those that do don't have hammers.
Link Posted: 6/20/2023 1:33:57 PM EST
[#20]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:


Ok, I suppose I should have asked that differently. How does a hammer work with an open bolt setup that has a fixed firing pin? What would be the point of the hammer?
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:
Originally Posted By amphibian:
Here is one example and since we are on AR15.com, relevant....
Colt LMG Open bolt:
https://john1911.com/the-open-bolt-m16-lsw-colt-model-950/


Ok, I suppose I should have asked that differently. How does a hammer work with an open bolt setup that has a fixed firing pin? What would be the point of the hammer?
In the case of the Colt LMG, the hammer is acting as also the sear to hold the carrier back as their is a notch in the carrier and does double duty to hit the floating FP.
The AM15 uses some of the Colt LMG fire control parts and has a fixed firing pin so the purpose of the hammer in that setup is just engage the bolt.
https://www.tacticalinc.com/catalog/product/id-420



Link Posted: 6/20/2023 2:06:40 PM EST
[#21]
Just got mine today- ordered last week. CQB length. Attachment Attached File

PAttachment Attached File
Link Posted: 6/20/2023 2:27:22 PM EST
[#22]
Discussion ForumsJump to Quoted PostQuote History
View Quote
Awesome, please give us some feedback after you get a chance to try it out!
Link Posted: 6/20/2023 2:29:40 PM EST
[#23]
Discussion ForumsJump to Quoted PostQuote History
View Quote

Can you pull the entire mechanism down so we can see if there's a notch where the bearings lock into the guide rod?
Link Posted: 6/20/2023 2:35:25 PM EST
[Last Edit: Droppoint] [#24]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By amphibian:
First of all, I agree with your definition of what an API configuration is.
Over 20 years ago when I got my first open bolt UZI SMG, someone on subguns.com 'corrected' me that the UZI is using API which I never understood since in order for the round to be fired, the case mouth would have to headspace at the end of the chamber...so the round must be fully in the chamber which doesn't match the definition of an API gun.
Back then, subguns.com was where all the experts posted and nobody seemed to correct this guy correcting me so I figured OK....  Maybe he is right and I just don't understand.
BTW, below is a picture I took from this book in my collection:
https://c3junkie.com/wp-content/uploads/2023/06/MilitarySmallArmsofthe20thCentury_p8.png
That picture is from page 8 of the book below written by Ian Hogg and John Weeks
https://m.media-amazon.com/images/I/51XSVNGTE9L._SX365_BO1,204,203,200_.jpg
I know Ian Hogg (now deceased) was a world renowned small arms experts.  Don't know about John Weeks.  
However it seems whoever wrote this first section titled 'Principles of Operation' got API wrong.

I think Ian McCollum of Forgotten Weapons has it right in his description here:
https://www.forgottenweapons.com/qa-7-video/
20:55   Submachine guns and Advance Primer Ignition (API)

All that said, I do want to re-iterate that an open bolt SMG has a much nicer recoil impulse than a closed bolt straight blowback.
A good example of this would be the UZI SMG fired in full auto in open bolt vs closed bolt.  I have full auto closed bolt configurations in my collection and the bolt weight is actually 3oz heavier in closed bolt but the recoil impulse on closed bolt sucks compared to the open bolt.  
On the open bolt UZI SMG, the bolt shouldn't be slamming into the trunnion until it has run out of ammo on an empty chamber.
Upon live fire, the round is detonated while the bolt is still going forward (but the round is still fully chambered, so it isn't API). This doesn't happen in the closed bolt version (full or semi) of the UZI and the recoil is much sharper on the closed bolt UZI's because of this.

It is a long winded answer and may be why many will just say, uh yeah it is API when it really isn't....
+1...no word from Maxim either.
View Quote

Thanks for the info.  The big question from my perspective regarding "is it API blowback" is the old "does it look/act/walk/quack like API blowback?"  Since the whole point of API is to use a bolt 1/2 to 1/10 normal weight, and a Sten uses a 22oz (ish) bolt assembly, that's a big "no" for the Sten.  Uzi is even heavier.  It fires slightly out of battery, yes.  Is it enough of a difference to make a difference?  Apparently not.  Seems this type of early OOB firing is a whole different animal.

I'll look up that book - thanks!
Link Posted: 6/20/2023 2:42:55 PM EST
[#25]
Discussion ForumsJump to Quoted PostQuote History
View Quote

Can't wait to start seeing reviews.

@str8shuutr45
Are you able to share the exact overall length of the CQB model?
I need to know... for reasons...
Link Posted: 6/20/2023 3:13:47 PM EST
[#26]
Here is the notch in the guide rod. Once I pull down the bottom portion, the ball bearings gets pushed out and the top portion is able to move down.




CQB Tube is ~5.6". Doesn't fit my SI Pistol Tube sadly, but I have the CQB tube coming in tomorrow so will give this a test then.
Link Posted: 6/20/2023 4:04:24 PM EST
[#27]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By amphibian:
In the case of the Colt LMG, the hammer is acting as also the sear to hold the carrier back as their is a notch in the carrier and does double duty to hit the floating FP.
The AM15 uses some of the Colt LMG fire control parts and has a fixed firing pin so the purpose of the hammer in that setup is just engage the bolt.
https://www.tacticalinc.com/catalog/product/id-420

https://www.tacticalinc.com/images/productextras/numbers-1-500.jpg

View Quote


So, on the AM15, the hammer acts like a sear, rather than like a hammer normally would? Brother, some of these designs are way too complicated.
Link Posted: 6/20/2023 4:41:15 PM EST
[#28]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:


So, on the AM15, the hammer acts like a sear, rather than like a hammer normally would? Brother, some of these designs are way too complicated.
View Quote

If the NFA didn't exist it wouldn't be so complicated.  Just make all the new MGs you want but it is what it is.
Link Posted: 6/20/2023 5:00:54 PM EST
[#29]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By amphibian:

If the NFA didn't exist it wouldn't be so complicated.  Just make all the new MGs you want but it is what it is.
View Quote


I don't understand. What does the NFA have to do with the mechanical complication of some of the designs. An open bolt design should be really simple.
Link Posted: 6/20/2023 5:02:44 PM EST
[#30]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By RDTCU:

Can't wait to start seeing reviews.

@str8shuutr45
Are you able to share the exact overall length of the CQB model?
I need to know... for reasons...
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By RDTCU:

Can't wait to start seeing reviews.

@str8shuutr45
Are you able to share the exact overall length of the CQB model?
I need to know... for reasons...

I’ll post the length tomorrow. FWIW, I tried fitting it into a Q stock from a honey badger that I have on a take down style 9 mm SBR.  It fit in the short buffer tube but I couldn’t get the BCG to move rearward.  I am going to swap stocks (AR15 w/Maxim CQB stock to 9mm SBR) will see what happens
Link Posted: 6/20/2023 5:08:48 PM EST
[#31]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:


I don't understand. What does the NFA have to do with the mechanical complication of some of the designs. An open bolt design should be really simple.
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:
Originally Posted By amphibian:

If the NFA didn't exist it wouldn't be so complicated.  Just make all the new MGs you want but it is what it is.


I don't understand. What does the NFA have to do with the mechanical complication of some of the designs. An open bolt design should be really simple.
Because if it wasn't for the NFA, you would just buy/build a new AM180 instead of shoe horning a new design to run AM180 drums on an M16 lower.

AM180 lower is stupid simple but not many transferable lowers compared to M16s.
Link Posted: 6/20/2023 5:16:03 PM EST
[#32]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:


I don't understand. What does the NFA have to do with the mechanical complication of some of the designs. An open bolt design should be really simple.
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:
Originally Posted By amphibian: If the NFA didn't exist it wouldn't be so complicated.  Just make all the new MGs you want but it is what it is.


I don't understand. What does the NFA have to do with the mechanical complication of some of the designs. An open bolt design should be really simple.


Straight blowback open bolt designs w/ fixed firing pins can be VERY simple.  Not everyone uses a fixed firing pin.
Link Posted: 6/20/2023 5:20:56 PM EST
[#33]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:


Just askin', how does an open bolt work in a gun with a hammer?
View Quote

Thompson 1921, 1928, M1 system here:
https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/1403492
Link Posted: 6/20/2023 5:28:05 PM EST
[#34]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By backbencher:Straight blowback open bolt designs w/ fixed firing pins can be VERY simple.  Not everyone uses a fixed firing pin.
View Quote


Ok, then they're too complicated for their purpose. But, I should know from dealing with Harley engineers, that engineers very often make things way too complex for their use. That usually introduces problems, especially for the end user.

Oh, and I'm still waiting on my Maxim RDS, too.
Link Posted: 6/20/2023 5:29:10 PM EST
[Last Edit: hdcharlie] [#35]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By SecondAmend:

Thompson 1921, 1928, M1 system here:
https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/1403492
View Quote


Link won't let me in. And, I changed the question slightly later in the discussion.
Link Posted: 6/20/2023 6:01:31 PM EST
[#36]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:


Ok, then they're too complicated for their purpose. But, I should know from dealing with Harley engineers, that engineers very often make things way too complex for their use. That usually introduces problems, especially for the end user.

Oh, and I'm still waiting on my Maxim RDS, too.
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:
Originally Posted By backbencher:Straight blowback open bolt designs w/ fixed firing pins can be VERY simple.  Not everyone uses a fixed firing pin.


Ok, then they're too complicated for their purpose. But, I should know from dealing with Harley engineers, that engineers very often make things way too complex for their use. That usually introduces problems, especially for the end user.

Oh, and I'm still waiting on my Maxim RDS, too.


Several reasons to use a hammer in an open-bolt gun:

Ability to use a cyclic rate reducer;

Commonality of parts w/ existing designs;

Conscript-proofing - ie, the gun doesn't go off when dropped or the bolt goes forward.
Link Posted: 6/20/2023 7:54:07 PM EST
[#37]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By backbencher:


Several reasons to use a hammer in an open-bolt gun:

Ability to use a cyclic rate reducer;

Commonality of parts w/ existing designs;

Conscript-proofing - ie, the gun doesn't go off when dropped or the bolt goes forward.
View Quote

Owners of Thompson M1A1 submachine guns (both those originally made as M1A1s and those that were rebuilt as such during depot and arsenal rebuilds) sometimes buy an M1 bolt assembly and switch back to the hammer fired configuration to reduce the likelihood of an out-of-battery discharge even though the rate of fire is increased.  I don't recall the timeframe, but a second "safety" sear notch was added to Thompson bolts to help provide the "Conscript-proofing" and weak ammo short stroking runaways.
Link Posted: 6/20/2023 9:29:50 PM EST
[#38]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Droppoint:
Uzi is even heavier.  It fires slightly out of battery, yes.  Is it enough of a difference to make a difference?  Apparently not.
View Quote


I’m lost as to how you concluded that considering you quoted Amphibian’s post on how the closed bolt Uzi, with a 3oz heavier bolt, has a much sharper recoil impulse than a open bolt Uzi.
Link Posted: 6/21/2023 5:47:29 AM EST
[#39]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Kiranslee:
Here is the notch in the guide rod. Once I pull down the bottom portion, the ball bearings gets pushed out and the top portion is able to move down.

https://i.imgur.com/tuHlmLk.jpg

View Quote

Bingo!  And there it is!  Thank you!
Link Posted: 6/21/2023 6:19:50 AM EST
[Last Edit: Droppoint] [#40]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By CJofFL:

I’m lost as to how you concluded that considering you quoted Amphibian’s post on how the closed bolt Uzi, with a 3oz heavier bolt, has a much sharper recoil impulse than a open bolt Uzi.
View Quote

I never said anything about recoil "sharpness".  In fact I never mentioned recoil at all.

The point was that if it was truly API blowback, the bolt would be 1/2 to 1/10 of the weight of a typical straight blowback.

The problem is that we are really talking about two completely distinct and different systems of operation that just happen to accidentally share one feature - premature primer ignition.  

The API blowback systems in automatic blowback cannons were intentionally engineered, designed, and timed to fire the primer in advance of complete chambering in order to greatly reduce the mass of the very heavy bolt needed for these systems. The ammunition for an API blowback system is specifically designed to allow this system to function consistently and predictably.

Open bolt SMGs prematurely fire the primer slightly before complete chambering as a side effect of unpredictable factors such as friction, primer hardness, cartridge alignment, cartridge case thickness, chamber fouling, etc.  This may have the unintentional benefit of reducing recoil slightly (sometimes), but is insufficient to actually provide the primary intended benefit of API blowback.  It's so unpredictable that open bolt guns are designed with bolts the same weight of typical closed-bolt blowbacks in order to protect the user from a hangfire or delayed ignition resulting from ammunition inconsistencies.

Several well-known writers have stated that all SMG's have this "feature".  If this is correct, open bolt SMG premature primer ignition should be considered just a side effect and common characteristic of the open bolt simple blowback design, not an exclusive operating system intentionally precision engineered and designed to solve a very specific problem.  Calling it API just causes confusion between this side-effect of the open bolt system and the actual precision engineered API blowback systems.  It would be more accurate to simply say that open bolt SMG's tend to experience slightly premature primer ignition, resulting in some moderation of the recoil forces.

Hope this helps clarify things.
Link Posted: 6/21/2023 8:32:37 AM EST
[#41]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Droppoint:

Open bolt SMGs prematurely fire the primer slightly before complete chambering as a side effect of unpredictable factors such as friction, primer hardness, cartridge alignment, cartridge case thickness, chamber fouling, etc.
View Quote
Uh...don't think so.  Unless you define chambering differently than I do?  In the case of a 9mm open bolt SMG like the UZI, the case mouth has to bottom out at the end of the chamber otherwise, how is the primer going to go off?  The only other way would be a chamber that is designed with a more aggressive taper but I've never seen any 9mm SMG with a chamber like that.
So IMHO, in a 9mm SMG (open or closed bolt), the round is fully chambered.  To me that is different than whether or not the bolt is fully closed.  Maybe that is what you are saying is not fully chambered?  
Again, in the case of an open bolt, UZI, Sterling, M11, MAC-10, Sten, MP40 etc...the rounds are fully chambered but the round is detonated while the bolt is still going forward.

Link Posted: 6/21/2023 9:02:19 AM EST
[#42]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By amphibian:  
Again, in the case of an open bolt, UZI, Sterling, M11, MAC-10, Sten, MP40 etc...the rounds are fully chambered but the round is detonated while the bolt is still going forward.
View Quote


I'm trying to understand, not questioning your statement above. So, do all the guns you mention have extractors that push the cartridge to the chamber without hooking the rim until the mouth of the case hits the forward edge of the chamber? I suppose that's the only way they could work as you describe.
Link Posted: 6/21/2023 9:03:34 AM EST
[Last Edit: Droppoint] [#43]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By amphibian:
Uh...don't think so.  Unless you define chambering differently than I do?  In the case of a 9mm open bolt SMG like the UZI, the case mouth has to bottom out at the end of the chamber otherwise, how is the primer going to go off?  The only other way would be a chamber that is designed with a more aggressive taper but I've never seen any 9mm SMG with a chamber like that.
So IMHO, in a 9mm SMG (open or closed bolt), the round is fully chambered.  To me that is different than whether or not the bolt is fully closed.  Maybe that is what you are saying is not fully chambered?  
Again, in the case of an open bolt, UZI, Sterling, M11, MAC-10, Sten, MP40 etc...the rounds are fully chambered but the round is detonated while the bolt is still going forward.

View Quote


I should clarify by adding they *can* prematurely fire....  my fault for typing too fast.

I did the research. You be the judge...

"The precise moment when the cap is detonated depends on a number of factors including: Dimensions of the chamber and round. A chamber of minimum diameter and a cartridge case of the largest diameter will produce early firing, whereas a chamber at the outer limits of toleranced diameter and a cartridge case at the lower end of permitted diameter would fire later. Friction in the chamber. The better, or smoother, the finish of the chamber, the more firing will be delayed due to reduced friction, all other actors being equal. The accumulation of carbon, primer residue, etc. will increase friction and cause premature firing. Grit, dirt, sand, etc. in the chamber and on the ammunition will produce the same effect."  Tactical Small Arms Of The 21st Century: A Complete Guide to Small Arms From Around the World, Charles Q. Cutshaw, page 18
Link Posted: 6/21/2023 9:09:26 AM EST
[Last Edit: Droppoint] [#44]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:


I'm trying to understand, not questioning your statement above. So, do all the guns you mention have extractors that push the cartridge to the chamber without hooking the rim until the mouth of the case hits the forward edge of the chamber? I suppose that's the only way they could work as you describe.
View Quote

AFAIK, they all have extractors that push the cartridge forward of the bolt face.  I'm sure @Amphibian will correct me if I'm wrong.

What I believe @Amphibian is saying is that the bolt is still moving forward after the cartrdidge chambers and fires.  As I understand it, this happens because the fixed firing pin is protruding from the bolt face and hits the primer before the bolt is done moving forward, crushing the FP into the primer.  What I'm saying is that the exact moment of firing (per my citiation above) can be unpredictable if the cartridge/chamber causes enough friction to allow the extractor to snap over the rim slightly earlier due to a number of factors.

This has turned into one wildly technical OT conversation.
Link Posted: 6/21/2023 9:19:54 AM EST
[#45]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Droppoint:

I never said anything about recoil "sharpness".  In fact I never mentioned recoil at all.

The point was that if it was truly API blowback, the bolt would be 1/2 to 1/10 of the weight of a typical straight blowback.

The problem is that we are really talking about two completely distinct and different systems of operation that just happen to accidentally share one feature - premature primer ignition.  

The API blowback systems in automatic blowback cannons were intentionally engineered, designed, and timed to fire the primer in advance of complete chambering in order to greatly reduce the mass of the very heavy bolt needed for these systems. The ammunition for an API blowback system is specifically designed to allow this system to function consistently and predictably.

Open bolt SMGs prematurely fire the primer slightly before complete chambering as a side effect of unpredictable factors such as friction, primer hardness, cartridge alignment, cartridge case thickness, chamber fouling, etc.  This may have the unintentional benefit of reducing recoil slightly (sometimes), but is insufficient to actually provide the primary intended benefit of API blowback.  It's so unpredictable that open bolt guns are designed with bolts the same weight of typical closed-bolt blowbacks in order to protect the user from a hangfire or delayed ignition resulting from ammunition inconsistencies.

Several well-known writers have stated that all SMG's have this "feature".  If this is correct, open bolt SMG premature primer ignition should be considered just a side effect and common characteristic of the open bolt simple blowback design, not an exclusive operating system intentionally precision engineered and designed to solve a very specific problem.  Calling it API just causes confusion between this side-effect of the open bolt system and the actual precision engineered API blowback systems.  It would be more accurate to simply say that open bolt SMG's tend to experience slightly premature primer ignition, resulting in some moderation of the recoil forces.

Hope this helps clarify things.
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Droppoint:
Originally Posted By CJofFL:  I’m lost as to how you concluded that considering you quoted Amphibian’s post on how the closed bolt Uzi, with a 3oz heavier bolt, has a much sharper recoil impulse than a open bolt Uzi.

I never said anything about recoil "sharpness".  In fact I never mentioned recoil at all.

The point was that if it was truly API blowback, the bolt would be 1/2 to 1/10 of the weight of a typical straight blowback.

The problem is that we are really talking about two completely distinct and different systems of operation that just happen to accidentally share one feature - premature primer ignition.  

The API blowback systems in automatic blowback cannons were intentionally engineered, designed, and timed to fire the primer in advance of complete chambering in order to greatly reduce the mass of the very heavy bolt needed for these systems. The ammunition for an API blowback system is specifically designed to allow this system to function consistently and predictably.

Open bolt SMGs prematurely fire the primer slightly before complete chambering as a side effect of unpredictable factors such as friction, primer hardness, cartridge alignment, cartridge case thickness, chamber fouling, etc.  This may have the unintentional benefit of reducing recoil slightly (sometimes), but is insufficient to actually provide the primary intended benefit of API blowback.  It's so unpredictable that open bolt guns are designed with bolts the same weight of typical closed-bolt blowbacks in order to protect the user from a hangfire or delayed ignition resulting from ammunition inconsistencies.

Several well-known writers have stated that all SMG's have this "feature".  If this is correct, open bolt SMG premature primer ignition should be considered just a side effect and common characteristic of the open bolt simple blowback design, not an exclusive operating system intentionally precision engineered and designed to solve a very specific problem.  Calling it API just causes confusion between this side-effect of the open bolt system and the actual precision engineered API blowback systems.  It would be more accurate to simply say that open bolt SMG's tend to experience slightly premature primer ignition, resulting in some moderation of the recoil forces.

Hope this helps clarify things.


What I'm looking for is a clear, bright line delineating what is API & what is not.  To me, it doesn't matter if Bergman & Schmeisser stumbled on API as part of a straight blowback system, or if that's not API b/c the case is fully seated.  But let's have a clear delineation that has references, not just some guy's opinion on ARFCOM.

API offers significant mass reduction in a bolt; however, designers may choose to use significantly more mass IOT slow the cyclic rate.  So saying open bolt submachine guns w/ fixed firing pins are clearly not API b/c their bolts are as heavy as their closed bolt semi-auto counterparts is not a clear delineation.  The Marlin Camp 9 carbine's bolt is quite arguably too light for a closed bolt gun, but they do work.

You need to offer us a more clear definition of what API is and what it is not, and why, than simple bolt mass.  It seems to me that just as straight blowback is a mechanism that cam be used from .22 LR to auto-cannon, so can API - even if auto-cannon are more sophisticated and have specially designed ammunition to take best advantage of API.
Link Posted: 6/21/2023 9:47:00 AM EST
[#46]
Since this thread was started for Maxim RDB buffer reviews can the API debate go somewhere else?
Link Posted: 6/21/2023 9:56:31 AM EST
[Last Edit: Droppoint] [#47]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By backbencher:


What I'm looking for is a clear, bright line delineating what is API & what is not.  To me, it doesn't matter if Bergman & Schmeisser stumbled on API as part of a straight blowback system, or if that's not API b/c the case is fully seated.  But let's have a clear delineation that has references, not just some guy's opinion on ARFCOM.

API offers significant mass reduction in a bolt; however, designers may choose to use significantly more mass IOT slow the cyclic rate.  So saying open bolt submachine guns w/ fixed firing pins are clearly not API b/c their bolts are as heavy as their closed bolt semi-auto counterparts is not a clear delineation.  The Marlin Camp 9 carbine's bolt is quite arguably too light for a closed bolt gun, but they do work.

You need to offer us a more clear definition of what API is and what it is not, and why, than simple bolt mass.  It seems to me that just as straight blowback is a mechanism that cam be used from .22 LR to auto-cannon, so can API - even if auto-cannon are more sophisticated and have specially designed ammunition to take best advantage of API.
View Quote

I don't need to offer you anything.  Do your own research.  Have fun.
Link Posted: 6/21/2023 10:01:25 AM EST
[Last Edit: Droppoint] [#48]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By RDTCU:
Since this thread was started for Maxim RDB buffer reviews can the API debate go somewhere else?
View Quote

Agreed.

New thread created: API is NOT used in ANY open bolt SMG's. Change my mind.

Still no shipping from Maxim.
Link Posted: 6/21/2023 4:22:27 PM EST
[#49]
I got a notification that Maxim created a shipping label for my order!
Link Posted: 6/21/2023 4:59:52 PM EST
[Last Edit: hdcharlie] [#50]
I also received notification of shipment, or at least, label creation!!!!

My estimated date for delivery is Mon., 6/26. I should have a preliminary report on the following day.
Page / 11
Maxim Defense RDB review (Page 2 of 11)
Close Join Our Mail List to Stay Up To Date! Win a FREE Membership!

Sign up for the ARFCOM weekly newsletter and be entered to win a free ARFCOM membership. One new winner* is announced every week!

You will receive an email every Friday morning featuring the latest chatter from the hottest topics, breaking news surrounding legislation, as well as exclusive deals only available to ARFCOM email subscribers.


By signing up you agree to our User Agreement. *Must have a registered ARFCOM account to win.
Top Top