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Maxim Defense RDB review (Page 1 of 11)
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Posted: 6/8/2023 12:14:36 PM EDT
[Last Edit: amphibian]
Created this thread for feedback on this new system.
I haven't seen any first hand reports on it.  I ordered one on 6/7 with no tracking info yet.
Please check in with any first hand deliveries or testing feedback
https://maximdefense.com/product/244978/



Link Posted: 6/8/2023 2:43:08 PM EDT
[#1]
Ordered Friday 6/2, no shipping updates yet.
Link Posted: 6/8/2023 3:21:46 PM EDT
[#2]
This should be an interesting thread. Look forward to hearing about it from you gentlemen.
Link Posted: 6/8/2023 4:39:52 PM EDT
[#3]
Originally Posted By amphibian:  Created this thread for feedback on this new system.
I haven't seen any first hand reports on it.  I ordered one on 6/7 with no tracking info yet.
Please check in with any first hand deliveries or testing feedback
https://maximdefense.com/product/244978/

https://maximdefense.com/wp-content/uploads/2023/04/RDB-Carbine_2-scaled.jpg
View Quote


https://maximdefense.com/product/244978/
Link Posted: 6/8/2023 11:00:50 PM EDT
[#4]
Wonder how it would compare to the Scheel RDB
Link Posted: 6/8/2023 11:14:06 PM EDT
[#5]
Ordered one on 6/4. Was told it would ship early next week. We'll see! They may have gotten more orders than they expected after it was covered on here.
Link Posted: 6/9/2023 12:45:25 AM EDT
[#6]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By jrtatonka:
Wonder how it would compare to the Scheel RDB
View Quote



It is of a similar principle, but what I like is the fact that everything is self contained and internal.  Pull your buffer and spring, drop this in, go to town
Link Posted: 6/9/2023 6:40:55 AM EDT
[#7]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By s4s4u:



It is of a similar principle, but what I like is the fact that everything is self contained and internal.  Pull your buffer and spring, drop this in, go to town
View Quote


I agree, but i can't help but wonder about the lack of adjustability of the Maxim unit.  Can it be used with 357sig, 40s&w, 45acp, etc.

Its about half the cost of the Scheel system, but the adjustability of the scheel system theoretically allows you to keep the bolt in battery as long as possible which i assume will increase velocity and keep the gun cleaner.

The downside to the scheel system is the buffertube, it should be easy enough to reproduce on any tube you own if you have access to a milling machine.  Although I wonder how it would work with a pdw stock system (how would you remove the buffer)

I'm in the market for 3 of these systems for more than just 9mm, so im looking forward to the feedback from you guys.
Link Posted: 6/9/2023 9:19:08 AM EDT
[#8]
Originally Posted By amphibian:
Created this thread for feedback on this new system.
I haven't seen any first hand reports on it.  I ordered one on 6/7 with no tracking info yet.
Please check in with any first hand deliveries or testing feedback
https://maximdefense.com/product/244978/

https://maximdefense.com/wp-content/uploads/2023/04/RDB-Carbine_2-scaled.jpg

View Quote


Hey Amphibian,
There isn't much info on their website, and I realize that you obviously don't have this yet and have no experience with it, but I am wondering your thoughts on this.

I am one of your converts to the A5 buffer tube/tubbs 556 flatwire/kynshot buffer setup recommendations. My current SBR lower has
BCM Intermediate RE A5 tube
Tubbs 556 flat wire spring
Kynshot RB5007 hydraulic buffer

I use my 8" CMMG 9mm RDB upper on it, along with a standard blowback 9mm 4.5" upper along a Stern Defense MAG-AD9 9mm Mag Adapter.

In order to use this new buffer, would I just take out the flatwire and buffer or would I need to change back to a carbine length buffer tube on my lower? What do you plan on doing with your lower?

I also shoot 223/556/300blackout on this lower with this setup. Will it work with those uppers as well on my lower with this?

For the most part I am happy with the above setups, but always looking for smoother and more reliability like yourself.

Again, I know you don't have any actual experience with this yet, but just wondering what your thoughts are on it as I am thinking or pre-ordering it depending on your thoughts.
Thanks,
Mav
Link Posted: 6/9/2023 9:33:25 AM EDT
[#9]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By jrtatonka:


I agree, but i can't help but wonder about the lack of adjustability of the Maxim unit.  Can it be used with 357sig, 40s&w, 45acp, etc.
View Quote View All Quotes
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Discussion ForumsJump to Quoted PostQuote History
Originally Posted By jrtatonka:


I agree, but i can't help but wonder about the lack of adjustability of the Maxim unit.  Can it be used with 357sig, 40s&w, 45acp, etc.
It says right on the product description on their website: "Our new RDB system is designed to convert your straight blowback AR-9"
No mention of other calibers.  That said, I know a straight blowback 357 Sig, 40SW, 45ACP uses the same parts minus the bolt face so I'm sure it could be used but for something high pressure like 357Sig, 40SW or 10mm, I would think it would definitely be sub optimal and who knows may even damage it and then when you tell them what you did, they may say well it wasn't designed for that.

This thing is new and as I posted in another thread, myself and everyone else that just ordered are in this Gen1 boat together.  Who knows what tune-ability if any they will offer.   Most people run 9mm so I'm sure they are just trying to appeal to the masses right now.

Its about half the cost of the Scheel system, but the adjustability of the scheel system theoretically allows you to keep the bolt in battery as long as possible which i assume will increase velocity and keep the gun cleaner.

The downside to the scheel system is the buffertube, it should be easy enough to reproduce on any tube you own if you have access to a milling machine.  Although I wonder how it would work with a pdw stock system (how would you remove the buffer)

I'm in the market for 3 of these systems for more than just 9mm, so im looking forward to the feedback from you guys.
I never liked the idea of using the buffer to for roller engagement so I stayed away from that design.

Depending on how the Maxim works out after my initial testing, I'm already thinking of ways to tune it like using different springs (like flat springs that slow the cyclic rate).  
I know typical AR9's use longer buffers to prevent the nasty malfunction where a case gets stuck behind the fixed ejector in the lower but IMHO that is very rare.  I'd like to do some tinkering with this system for max stroke length to decrease the cyclic rate by increasing the bolt travel which yes I know will also give the bolt more inertia for the BHO to stop and possibly break but also this design looks like it will require removing the weight from the bolt.
Removing the weight from the bolt means less mass that the BHO has to stop so maybe it is a wash.
I would have to most likely make a new rod on the lathe for this extended stroke but that shouldn't be a big deal.  If the initial testing is good, I'd probably just buy a second one to frankenstein or who knows maybe they will offer a bunch of tuning options.

I'm just happy to see more options to make the straight blowback AR9 less crappy.
Link Posted: 6/9/2023 9:50:31 AM EDT
[Last Edit: amphibian] [#10]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Mav3rick:


Hey Amphibian,
There isn't much info on their website, and I realize that you obviously don't have this yet and have no experience with it, but I am wondering your thoughts on this.

I am one of your converts to the A5 buffer tube/tubbs 556 flatwire/kynshot buffer setup recommendations. My current SBR lower has
BCM Intermediate RE A5 tube
Tubbs 556 flat wire spring
Kynshot RB5007 hydraulic buffer

I use my 8" CMMG 9mm RDB upper on it, along with a standard blowback 9mm 4.5" upper along a Stern Defense MAG-AD9 9mm Mag Adapter.
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Mav3rick:


Hey Amphibian,
There isn't much info on their website, and I realize that you obviously don't have this yet and have no experience with it, but I am wondering your thoughts on this.

I am one of your converts to the A5 buffer tube/tubbs 556 flatwire/kynshot buffer setup recommendations. My current SBR lower has
BCM Intermediate RE A5 tube
Tubbs 556 flat wire spring
Kynshot RB5007 hydraulic buffer

I use my 8" CMMG 9mm RDB upper on it, along with a standard blowback 9mm 4.5" upper along a Stern Defense MAG-AD9 9mm Mag Adapter.
So for your straight blowback 9mm 4.5" upper, to use the new Maxim Defense RDB assembly, you would need to drop in a spacer like below so you don't have to swap your buffer tube.
Or get some quarters or whatever to shove in there to basically give your A5 tube carbine length depth.

In order to use this new buffer, would I just take out the flatwire and buffer or would I need to change back to a carbine length buffer tube on my lower? What do you plan on doing with your lower?
I just posted while you posted so you can read what I have planned above.
I also shoot 223/556/300blackout on this lower with this setup. Will it work with those uppers as well on my lower with this?
You mean you want to use the Maxim RDB assembly with rifle caliber??  It is designed specifically for 9mm straight blowback drop in.  I would think if this thing worked on rifle caliber they would have made a big deal about some new universal buffer system.  As I mentioned above, this thing is designed for the shorter stroke of a straight blowback 9mm so pretty sure it is a no-go for rifle caliber.
As you can see in my post I just made, I'm already planning on possibly making a new guide rod for extended stroke for tinkering with 9mm but I personally wouldn't use this for rifle caliber.  For rifle caliber, IMHO #1 is controlling the gas (many methods and for all you adjustable gas haters, yes I am also saying fixed gas block using something like a restricted gas block like a YHM suppressor gas block, BRT tube, gas block insert, properly gassed barrel...whatever) then #2 is buffer / spring selection.
For the most part I am happy with the above setups, but always looking for smoother and more reliability like yourself.

Again, I know you don't have any actual experience with this yet, but just wondering what your thoughts are on it as I am thinking or pre-ordering it depending on your thoughts.
Thanks,
Mav
I have a new high speed camera and will be doing some high speed video footage of what I think are the smoothest setups for 556 as well as 9mm in the future.  I already have some on my Youtube channel but those were pretty crappy resolution.
I personally think an optimized gas port, using a larger volume gas tube, then my preferred tube/buffer and spring is the way to go for 556 (especially for suppressed)...but we are getting off topic so I'll stop.
Link Posted: 6/9/2023 3:05:49 PM EDT
[#11]
I just received an email that my order is being processed.....not shipped yet.
Link Posted: 6/10/2023 6:12:33 AM EDT
[#12]
Just placed my order for the carbine version.  Eager to give this system a try.
Link Posted: 6/10/2023 11:43:46 AM EDT
[#13]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By jrtatonka:
Wonder how it would compare to the Scheel RDB
View Quote


I’m going to compare the two, but it’ll be a couple of weeks. Have some family shit going on.
Link Posted: 6/11/2023 2:31:17 PM EDT
[#14]
Please post reviews after testing. I am extremely interested in this.
Link Posted: 6/11/2023 4:35:13 PM EDT
[Last Edit: bruh44] [#15]
I’ve got the CMMG, I’m very happy with it. I’m definitely interested to see where this thread goes though. It would like something like this for 45.
Link Posted: 6/11/2023 5:10:36 PM EDT
[#16]
Tagged.

I want to try this full auto.
Link Posted: 6/12/2023 6:20:03 AM EDT
[#17]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By jaqufrost:

I want to try this full auto.
View Quote
+1.  I will be doing the same with a 4.5" upper and an integrally ported/suppressed upper.
As I posted on the other thread, I am anticipating like around 900 RPM with this setup which I don't like.  However, if it smooths it out, should be worth it and at the price point, I may tinker with it to see if I can slow it down.
Link Posted: 6/14/2023 12:33:05 PM EDT
[#18]
I placed an order on this as well but order the CQB version to be used with my short buffer tube. Still no shipping updates as of yet.

I did send an email to Maxim to ask about compatibility and they said "The RDB’s are only for 9mm at this time."

Link Posted: 6/14/2023 8:49:39 PM EDT
[Last Edit: jt526] [#19]
I ordered one on the 6th, and still nothing. Fingers crossed shipping soon. Will still likely go through with the MEAN upper as well to compare them. But with this I can maybe do one of the integral MP5 SD style suppressor barrels and a B&T can
Link Posted: 6/14/2023 11:14:07 PM EDT
[Last Edit: hdcharlie] [#20]
Read the first line under the item for sale! Why can't companies just say things like this up front. That line wasn't there when I placed my order.

When I was the service manager at a large Harley dealership, I had the rep of under promising but over delivering. Most companies these days seem to work at doing just the opposite! I asked via email when my order might be shipped and was told late last week or early this week. That time has passed and there can't be so many orders placed before mine that they didn't know that time-frame was b.s. I don't mind waiting when I know the situation up front.

https://maximdefense.com/product/244978/
Link Posted: 6/15/2023 3:44:53 AM EDT
[Last Edit: 1168RGR] [#21]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:
Read the first line under the item for sale! Why can't companies just say things like this up front. That line wasn't there when I placed my order.
View Quote

No, it was not there last week.
Link Posted: 6/15/2023 7:49:23 AM EDT
[#22]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By 1168RGR:

No, it was not there last week.
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Originally Posted By 1168RGR:
Originally Posted By hdcharlie:
Read the first line under the item for sale! Why can't companies just say things like this up front. That line wasn't there when I placed my order.

No, it was not there last week.
I think they just added that yesterday or the day before.
Anyone else get emails that their order was in a 'processing' state like I did?
Link Posted: 6/15/2023 9:05:52 AM EDT
[Last Edit: hdcharlie] [#23]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By amphibian:
I think they just added that yesterday or the day before.
Anyone else get emails that their order was in a 'processing' state like I did?
View Quote


My order showed "processing" on their website as soon as I placed the order, which was on 6/4. That term is obviously meaningless.

I wonder if they didn't just throw it up on the site to see what kind of response it would get.
Link Posted: 6/15/2023 9:11:27 AM EDT
[Last Edit: amphibian] [#24]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:


My order showed "processing" on their website as soon as I placed the order, which was on 6/4. That term is obviously meaningless.

I wonder if they didn't just throw it up on the site to see what kind of response it would get.
View Quote
Yeah, I find it odd that I can't find any reviews or articles on it.  Did a quick check on their FB page also.  You guys find anything on it other than their website?
Link Posted: 6/15/2023 10:39:50 AM EDT
[#25]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By amphibian:
Yeah, I find it odd that I can't find any reviews or articles on it.  Did a quick check on their FB page also.  You guys find anything on it other than their website?
View Quote

Nada.
Link Posted: 6/15/2023 11:54:28 AM EDT
[#26]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:


My order showed "processing" on their website as soon as I placed the order, which was on 6/4. That term is obviously meaningless.

I wonder if they didn't just throw it up on the site to see what kind of response it would get.
View Quote

Could be just trying to get big enough batch to minimize per item cost by keeping tooling setup per job down.

MHO, YMMV, etc.  Be well.
Link Posted: 6/15/2023 1:20:28 PM EDT
[Last Edit: Droppoint] [#27]
Link Posted: 6/15/2023 4:35:24 PM EDT
[#28]
Well, I just got the shipping notification so it looks like they are starting to ship! Should be here 6/17/2023. I ordered on 6/11/2023.

Link Posted: 6/15/2023 5:20:28 PM EDT
[#29]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Kiranslee:
Well, I just got the shipping notification so it looks like they are starting to ship! Should be here 6/17/2023. I ordered on 6/11/2023.
View Quote



Now I am pi$$ed. I ordered on 6/4 and yours from 6/11 is being shipped.
Link Posted: 6/15/2023 5:50:48 PM EDT
[#30]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:

Now I am pi$$ed. I ordered on 6/4 and yours from 6/11 is being shipped.
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Originally Posted By hdcharlie:
Originally Posted By Kiranslee:
Well, I just got the shipping notification so it looks like they are starting to ship! Should be here 6/17/2023. I ordered on 6/11/2023.

Now I am pi$$ed. I ordered on 6/4 and yours from 6/11 is being shipped.
Maybe only the CQB versions in stock
Link Posted: 6/15/2023 6:03:39 PM EDT
[#31]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By amphibian:
Maybe only the CQB versions in stock
View Quote


That could be, since poster didn't specify.
Link Posted: 6/15/2023 6:06:24 PM EDT
[#32]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:

That could be, since poster didn't specify.
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Originally Posted By hdcharlie:
Originally Posted By amphibian:
Maybe only the CQB versions in stock

That could be, since poster didn't specify.

He did ... scroll up...to his post yesterday
Link Posted: 6/15/2023 6:11:02 PM EDT
[#33]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By amphibian:He did ... scroll up...to his post yesterday
View Quote


Yeah, should have checked for earlier posts.
Link Posted: 6/15/2023 6:34:10 PM EDT
[#34]
Stupid question:

Why wouldn't this work on an overgassed 5.56 AR instead of an adjustable gas block?

Would a weightless model paired with a lightweight bolt cycle like a rifle with the gas turned down?
Link Posted: 6/15/2023 7:17:31 PM EDT
[#35]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By zukiphile:
Stupid question:

Why wouldn't this work on an overgassed 5.56 AR instead of an adjustable gas block?

Would a weightless model paired with a lightweight bolt cycle like a rifle with the gas turned down?
View Quote
I'm pretty sure the stroke is to short for 5.56.
Link Posted: 6/17/2023 9:32:07 AM EDT
[#36]
I’d love for this to be true but I’m skeptical.

Any delayed blowback mechanism is a nearly locked breach at the moment of ignition, hence why the lugs/rollers are locked into a barrel extension or receiver that can handle the pressure. How will something that “locks” into the buffer tube be able to come close to the same strength?
Link Posted: 6/17/2023 9:40:03 AM EDT
[Last Edit: RDTCU] [#37]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By JustaDeplorable76:
I’d love for this to be true but I’m skeptical.

Any delayed blowback mechanism is a nearly locked breach at the moment of ignition, hence why the lugs/rollers are locked into a barrel extension or receiver that can handle the pressure. How will something that “locks” into the buffer tube be able to come close to the same strength?
View Quote

This isn't like a roller locked HK or CMMG, with a light bolt and heavy mass that must be accelerated by a mechanical DISadvantage..

Think of it more akin to the Stribog A3.
The bolt is the primary mass and it's much heavier than the secondary "locking" mass.
The principal is the same but the inertia vs mechanical delay is a little different.
Link Posted: 6/17/2023 10:44:06 AM EDT
[#38]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By JustaDeplorable76:  I’d love for this to be true but I’m skeptical.

Any delayed blowback mechanism is a nearly locked breach at the moment of ignition, hence why the lugs/rollers are locked into a barrel extension or receiver that can handle the pressure. How will something that “locks” into the buffer tube be able to come close to the same strength?
View Quote


 The whole point of a blowback system is it is NOT locked.  The breech face begins moving to the rear as soon as the bullet begins forward movement.
Link Posted: 6/17/2023 10:54:15 AM EDT
[#39]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By amphibian:
So for your straight blowback 9mm 4.5" upper, to use the new Maxim Defense RDB assembly, you would need to drop in a spacer like below so you don't have to swap your buffer tube.
Or get some quarters or whatever to shove in there to basically give your A5 tube carbine length depth.
https://cdn11.bigcommerce.com/s-15wahz8ybt/images/stencil/900x1800/products/149/586/SK-BS-2__86432.1653300429.jpg?c=1
I just posted while you posted so you can read what I have planned above.
You mean you want to use the Maxim RDB assembly with rifle caliber??  It is designed specifically for 9mm straight blowback drop in.  I would think if this thing worked on rifle caliber they would have made a big deal about some new universal buffer system.  As I mentioned above, this thing is designed for the shorter stroke of a straight blowback 9mm so pretty sure it is a no-go for rifle caliber.
As you can see in my post I just made, I'm already planning on possibly making a new guide rod for extended stroke for tinkering with 9mm but I personally wouldn't use this for rifle caliber.  For rifle caliber, IMHO #1 is controlling the gas (many methods and for all you adjustable gas haters, yes I am also saying fixed gas block using something like a restricted gas block like a YHM suppressor gas block, BRT tube, gas block insert, properly gassed barrel...whatever) then #2 is buffer / spring selection.
I have a new high speed camera and will be doing some high speed video footage of what I think are the smoothest setups for 556 as well as 9mm in the future.  I already have some on my Youtube channel but those were pretty crappy resolution.
I personally think an optimized gas port, using a larger volume gas tube, then my preferred tube/buffer and spring is the way to go for 556 (especially for suppressed)...but we are getting off topic so I'll stop.
View Quote

Thanks for getting back to me. I will wait on this for now and see how you like it before I go forward with any changes.
Link Posted: 6/17/2023 12:20:59 PM EDT
[Last Edit: s4s4u] [#40]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By backbencher:


 The whole point of a blowback system is it is NOT locked.  The breech face begins moving to the rear as soon as the bullet begins forward movement.
View Quote


Exactly.  And, systems like the Maxim are designed to simply slow that reaction down a little so some pressue bleeds off before the case leaves the chamber upon firing.  There is no need for "lock up", just a little delay is all it takes.  Hence, "delayed blowback"
Link Posted: 6/17/2023 2:19:16 PM EDT
[#41]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By backbencher:


 The whole point of a blowback system is it is NOT locked.  The breech face begins moving to the rear as soon as the bullet begins forward movement.
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Originally Posted By backbencher:
Originally Posted By JustaDeplorable76:  I’d love for this to be true but I’m skeptical.

Any delayed blowback mechanism is a nearly locked breach at the moment of ignition, hence why the lugs/rollers are locked into a barrel extension or receiver that can handle the pressure. How will something that “locks” into the buffer tube be able to come close to the same strength?


 The whole point of a blowback system is it is NOT locked.  The breech face begins moving to the rear as soon as the bullet begins forward movement.


Nearly locked - the delay uses leverage/friction or some other mechanism so that it’s not pure mass, hence the difference in bolt mass of an MP5 vs AR9 straight blow back or Uzi. Correct me if I’m wrong but the MP5 bolt rollers or the CMMG lugs take a significant amount of pressure in the delay mechanism right?

Hence why those lugs/rollers operate on the extension or receiver. If this function strictly in the principle as a lever delay I’d think if the “levered” mass is low versus the BCG it would not make much of a difference.
Link Posted: 6/18/2023 8:37:50 AM EDT
[Last Edit: Droppoint] [#42]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By JustaDeplorable76:
I’d love for this to be true but I’m skeptical.

Any delayed blowback mechanism is a nearly locked breach at the moment of ignition, hence why the lugs/rollers are locked into a barrel extension or receiver that can handle the pressure. How will something that “locks” into the buffer tube be able to come close to the same strength?
View Quote

Based on what I'm seeing, it's not locked into the buffer tube.  The front-most inner portion of the buffer system that results in the delay is locked into the guide rod.  Look at how the rollers move.  When the outer rear collar moves back, the rollers are allowed to move outward, away from the guide rod, implying that there's a locking groove in the guide rod.

Near as I can figure, the rearward inertia energy at the moment of firing goes from cartridge base, to bolt, to inner roller-locking piece, to outer locking-piece collar, like one of those desktop pendulum toys.  The last thing in line that isn't locked and can move is the outer locking-piece collar.  It moves backward releasing the inward pressure on the rollers.  The rollers release the inner roller-locking piece from the guide rod and then the front portion can move backwards against the spring pressure, releasing the bolt.  The only pressure on the tube is longitudinally, holding the entire system in place during that initial rearward shock (and later impact of the buffer into the plastic cushion) which is what the tube was designed to handle.

The length, front to back, of the locking collar that rests over the rollers is what controls the length of the delay.  The farther back it has to travel before it releases the rollers increases the delay before the inner (front-most) portion of the system can move and release the bolt from battery.

At least that's my best guess.  If I'm right, this is really brilliant engineering.  They took what HK did and reversed it, locking inward instead of outward, allowing them to create a completely self-contained system.
Link Posted: 6/18/2023 12:35:16 PM EDT
[#43]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By JustaDeplorable76:


Nearly locked - the delay uses leverage/friction or some other mechanism so that it’s not pure mass, hence the difference in bolt mass of an MP5 vs AR9 straight blow back or Uzi. Correct me if I’m wrong but the MP5 bolt rollers or the CMMG lugs take a significant amount of pressure in the delay mechanism right?

Hence why those lugs/rollers operate on the extension or receiver. If this function strictly in the principle as a lever delay I’d think if the “levered” mass is low versus the BCG it would not make much of a difference.
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Originally Posted By JustaDeplorable76:
Originally Posted By backbencher:
Originally Posted By JustaDeplorable76:  I’d love for this to be true but I’m skeptical.

Any delayed blowback mechanism is a nearly locked breach at the moment of ignition, hence why the lugs/rollers are locked into a barrel extension or receiver that can handle the pressure. How will something that “locks” into the buffer tube be able to come close to the same strength?


 The whole point of a blowback system is it is NOT locked.  The breech face begins moving to the rear as soon as the bullet begins forward movement.


Nearly locked - the delay uses leverage/friction or some other mechanism so that it’s not pure mass, hence the difference in bolt mass of an MP5 vs AR9 straight blow back or Uzi. Correct me if I’m wrong but the MP5 bolt rollers or the CMMG lugs take a significant amount of pressure in the delay mechanism right?

Hence why those lugs/rollers operate on the extension or receiver. If this function strictly in the principle as a lever delay I’d think if the “levered” mass is low versus the BCG it would not make much of a difference.


Would you leave your delayed blowback gun in a nearly locked car in a Diverse, Inclusive, and Equitable neighborhood?

Actions are either locked or unlocked.  The Mk19 40mm grenade launcher is an unlocked action.
Link Posted: 6/18/2023 4:37:56 PM EDT
[#44]
a request of those doing any objective testing, would you comment on the amount of "dot shake" as well as perceived recoil?  with a clocked and modified Miculek brake and CMMG RDS in my AR9, I've removed most of the dot movement, but can live with a little recoil... regards Les   L747
Link Posted: 6/18/2023 7:30:12 PM EDT
[#45]
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Originally Posted By lasnyder:
a request of those doing any objective testing, would you comment on the amount of "dot shake" as well as perceived recoil?  with a clocked and modified Miculek brake and CMMG RDS in my AR9, I've removed most of the dot movement, but can live with a little recoil... regards Les   L747
View Quote

I'll see what I can do to report back on that, but if what you've got works, don't fix it.
Link Posted: 6/18/2023 7:45:06 PM EDT
[#46]
Droppont... thank you ... I like to keep up with the utility of new widgets when they come on the market... I pretty much shoot only Steel Challenge rimfire now
Link Posted: 6/19/2023 1:20:15 AM EDT
[#47]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By backbencher:


Would you leave your delayed blowback gun in a nearly locked car in a Diverse, Inclusive, and Equitable neighborhood?

Actions are either locked or unlocked.  The Mk19 40mm grenade launcher is an unlocked action.
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Originally Posted By backbencher:
Originally Posted By JustaDeplorable76:
Originally Posted By backbencher:
Originally Posted By JustaDeplorable76:  I’d love for this to be true but I’m skeptical.

Any delayed blowback mechanism is a nearly locked breach at the moment of ignition, hence why the lugs/rollers are locked into a barrel extension or receiver that can handle the pressure. How will something that “locks” into the buffer tube be able to come close to the same strength?


 The whole point of a blowback system is it is NOT locked.  The breech face begins moving to the rear as soon as the bullet begins forward movement.


Nearly locked - the delay uses leverage/friction or some other mechanism so that it’s not pure mass, hence the difference in bolt mass of an MP5 vs AR9 straight blow back or Uzi. Correct me if I’m wrong but the MP5 bolt rollers or the CMMG lugs take a significant amount of pressure in the delay mechanism right?

Hence why those lugs/rollers operate on the extension or receiver. If this function strictly in the principle as a lever delay I’d think if the “levered” mass is low versus the BCG it would not make much of a difference.


Would you leave your delayed blowback gun in a nearly locked car in a Diverse, Inclusive, and Equitable neighborhood?

Actions are either locked or unlocked.  The Mk19 40mm grenade launcher is an unlocked action.


Mk19 is an advanced primer ignition, sadly we can’t have those. (Not sure how smart running tons of 9mm through an API would be, seems a kaboom would be a matter of time)
Link Posted: 6/19/2023 6:51:42 AM EDT
[#48]
Well, according to the extensive article on "Blowback" in Wikipedia, API is a feature in almost all open-bolt subguns so literally "tons" of 9mm has been run through them without a problem.  The article is a fascinating read, and includes several methods of delaying blowback that I had never even heard of.

Unfortunately, the AR in 9mm is one of the few closed-bolt 9mms around, so API can't be used.  If someone has come up with an alternative method of delaying blowback that works, it would benefit all of us users.
Link Posted: 6/19/2023 8:48:31 AM EDT
[#49]
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Originally Posted By Silverbear_51:
Well, according to the extensive article on "Blowback" in Wikipedia, API is a feature in almost all open-bolt subguns so literally "tons" of 9mm has been run through them without a problem.  The article is a fascinating read, and includes several methods of delaying blowback that I had never even heard of.

Unfortunately, the AR in 9mm is one of the few closed-bolt 9mms around, so API can't be used.  If someone has come up with an alternative method of delaying blowback that works, it would benefit all of us users.
View Quote


Pretty much every PCC is closed bolt these days. Even semi auto macs are closed since the ATF ruled they were easily convertible years ago.
Link Posted: 6/19/2023 8:51:22 AM EDT
[Last Edit: Droppoint] [#50]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Silverbear_51:
Well, according to the extensive article on "Blowback" in Wikipedia, API is a feature in almost all open-bolt subguns so literally "tons" of 9mm has been run through them without a problem.  The article is a fascinating read, and includes several methods of delaying blowback that I had never even heard of.

Unfortunately, the AR in 9mm is one of the few closed-bolt 9mms around, so API can't be used.  If someone has come up with an alternative method of delaying blowback that works, it would benefit all of us users.
View Quote

API is not used in any open bolt subgun.  Period.  I have researched this topic extensively.  This is another myth in the 9mm blowback community that needs to be eliminated, and another reason why absolutely no academic institution allows Wikipedia to be used as a credible reference source.  Every article I’ve found, including the references quoted in the Wikipedia article (yes, I checked them), that makes the suggestion that API is involved has either no source references, or dead-end references with NO originating source, which means it must be treated as hearsay and nothing more. Advanced primer ignition (API) is only used in some specialized cannon systems, not SMGs.

Anthony G. Williams, in his book which is quoted in Wikipedia, makes absolutely no credible, logical, rational, or engineering arguments why he thinks API is used in SMG's.  He literally mentions it in passing, and with no references for his source of this information.  We must assume it was an assumption on his part.  This is one of the dangers of trusting sources as credible without doing adequate research.

Here's an academic reference as to why API is NOT used in subguns which makes logical and engineering sense:

“Even weapons with fixed firing pins must be considered as firing from a closed bolt. A bolt with fixed firing pin has certain residual energy in forward direction when a normal round is fired. However, with a slow primer/powder ignition or a hang fire this energy is gone when the cartridge fires.” –Submachine Gun Designer’s Handbook by George Dmitrieff, P.10 https://elcombate.noblogs.org/files/2017/05/Submachine_Gun_Designers_Handbook_Dmitrieff_text.pdf

As stated, the problem with API in subguns is the inconsistency of the ammo. If a cartridge hangfires or has slow ignition (not uncommon) the bolt weight would now be dangerously light.  The point of API is to be able to use a lighter than normal bolt (down to 1/10 the mass) for the blowback operation.  Most blowback open bolt subguns and closed bolt guns both have bolts in the 22-24oz range, but bolts even as light as 14oz have shown to be "safe" with 9mm if the receiver is designed for it (Uzi Pro) (don't try this at home), no API required.  If API were actually being used, we should expect to see bolts much lighter.

Sorry for the rant, this is a pet peeve of mine.

Edits for clarification and spelling.
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