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Maxim Defense RDB review (Page 8 of 11)
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Link Posted: 7/30/2023 4:10:39 PM EST
[Last Edit: jt526] [#1]
Just got back from range, working with a JP 9mm carrier cut for lightning link. I liked the speed, easy bursts, could pull singles, still a bit sharp on recoil, it for sure was bottoming out, so maybe mess with trimming the  buffer a bit. The main issue I have is the cocking weight. I had 2 hammer follows on FA (new FCG setup needs a little something) and had to rack it at the indoor range and Jesus is it stiff. Like legit I felt uncomfortable, awkward, and unsafe manipulating a loaded weapon with that much effort at a public range.

the pros are there
1) drop in solution
2) works with other barrels/uppers like the SD upper that uses HK cans I have my eye on
3) cheap

i might grab a side charger and try again, but MEAN arms already has my deposit just waiting on the call, and I am sure getting an HK integral can on it is just a matter of how much I am willing to spend
fnh
Link Posted: 7/31/2023 7:37:38 AM EST
[Last Edit: Droppoint] [#2]
Originally Posted By jt526:
The main issue I have is the cocking weight. I had 2 hammer follows on FA (new FCG setup needs a little something) and had to rack it at the indoor range and Jesus is it stiff. Like legit I felt uncomfortable, awkward, and unsafe manipulating a loaded weapon with that much effort at a public range.
View Quote
Same.  Takes about 32# of pressure on that little charging handle surface area to pop the mechanical delay loose *with* the hammer already cocked. 3x a normal AR. I have to brace the stock against my chest to rack it from the fully forward and locked position.  I'll need to measure it with the hammer forward and see how bad it is....

I'm still waiting for this to come in:


https://www.springfield-armory.com/intel/press-releases/springfield-armory-releases-innovative-ar-charging-handle-the-levar/

"When you pull the extended lever to the rear, you have a roughly 3:1 mechanical advantage over a traditional charging handle."

Using the camming action should drop it back down to around normal AR pull force to pop it past the wall.

ETA: Shipped this morning.
Link Posted: 7/31/2023 7:40:02 AM EST
[#3]
@amphibian

I probably missed it - did you do a ROF test on the Maxim by itself in a blowback?
Link Posted: 7/31/2023 9:21:14 AM EST
[#4]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Droppoint:
@amphibian

I probably missed it - did you do a ROF test on the Maxim by itself in a blowback?
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Yes, I have the results on page 6 of this thread.
Link Posted: 8/1/2023 6:12:00 PM EST
[Last Edit: gongo] [#5]
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Originally Posted By gongo:

We'll see if there are any instructions and what they actually say!
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Originally Posted By gongo:
Originally Posted By hdcharlie:
And they say there are instructions included.

We'll see if there are any instructions and what they actually say!

There were no instructions in the box, just the text on the box:

"The Roller Delayed Buffer System from Maxim Defense turns your 9mm AR pattern firearm into a roller delayed blowback system.
This upgrade significantly reduces felt recoil while increasing firearm reliability.
USE ONLY IN 9MM AR PATTERN FIREARMS.
  • Converts straight blow back AR-9 to roller delayed system
  • Fits into standard carbine length buffer tubs
  • Easily installs on Mil-Spec AR15/AR-9 lowers
  • Replaces Buffer and Spring
  • Drop in fix for your AR-9 buffer weight issues
Caliber: 9mm
Weight: 8.3oz"

At first it wouldn't open at all, I think they got a lot of thread locker all over the top section so it was all stuck together to the front end of the rod.
I tried to disassemble the rod but it's cranked down tightly.
It definitely feels better after a bit of lube and working the action a lot.
I have the buffer tube flush with no pre-load and the buffer retaining pin removed.
I probably won't get to the range for at least a week or so, but I'll keep fiddling with it.

I guess I must be a malnourished weakling like Droppoint because this is more than just a little bit of extra effort to charge the action now.
We'll see. I might need a gym membership after all! :D

ETA: A little bit of pre-load made a big difference in getting past that initial "wall".
I had to remove the buffer retainer since it got majorly hung up on it.
Trying to get the unit into the buffer tube was annoying with the hammer getting in the way.
It fits much tighter in one of my buffer tubes but looser in the other.
Since I was adjusting for pre-load and removing the buffer retainer anyway, it was a lot easier to just drop the unit into the tube first and then screw the tube onto the receiver.
I think installation may be super easy in some lowers and much more fiddly in others.
It's probably fine since most people buying this also pieced together the firearm that it's going into, but it's not newbie-friendly for those who just bought a complete 9mm AR and don't have the tools or experience to remove the buffer tube.
Link Posted: 8/2/2023 9:00:14 AM EST
[#6]
Kind of upsetting to hear that not only did I pay more but now I’m waiting longer by ordering directly from Maxim. I have been assured by Maxim customer service that a new batch is forthcoming all the while I could have saved nearly $50 by going to optics planet. Going to reach out to them about at least price matching to what a couple posters here have quoted.
Link Posted: 8/2/2023 9:12:22 AM EST
[#7]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Park-Hit-Run:
Kind of upsetting to hear that not only did I pay more but now I’m waiting longer by ordering directly from Maxim. I have been assured by Maxim customer service that a new batch is forthcoming all the while I could have saved nearly $50 by going to optics planet. Going to reach out to them about at least price matching to what a couple posters here have quoted.
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Why don't you cancel the Maxim order and then place one with Optics Planet? At the moment they still have 7 in stock.
Link Posted: 8/2/2023 10:07:41 AM EST
[#8]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:


Why don't you cancel the Maxim order and then place one with Optics Planet? At the moment they still have 7 in stock.
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Originally Posted By hdcharlie:
Originally Posted By Park-Hit-Run:
Kind of upsetting to hear that not only did I pay more but now I’m waiting longer by ordering directly from Maxim. I have been assured by Maxim customer service that a new batch is forthcoming all the while I could have saved nearly $50 by going to optics planet. Going to reach out to them about at least price matching to what a couple posters here have quoted.


Why don't you cancel the Maxim order and then place one with Optics Planet? At the moment they still have 7 in stock.


"in stock"
Link Posted: 8/2/2023 10:18:06 AM EST
[#9]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By backbencher:


"in stock"
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?
Link Posted: 8/2/2023 11:18:10 AM EST
[#10]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:



?
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Originally Posted By hdcharlie:
Originally Posted By backbencher:


"in stock"



?

Optics Planet has gained a certain reputation over the years of listing things as "in stock" but then taking 6-8 weeks to ship because it wasn't in stock.

I've ordered from them a bunch of times and never had any problems receiving my orders within 2 weeks, but I understand that many people are still reluctant to order from them because of the stories.

My guess is that when a couple of us posted about ordering on Optics Planet, those who already had ordered directly thought "yeah, so you saved $30, but you'll be waiting months to get it". Hence the indignation above that I got my order in just a week.
Link Posted: 8/2/2023 11:21:30 AM EST
[#11]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:



?
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Originally Posted By hdcharlie:
Originally Posted By backbencher:


"in stock"



?

Optics Planet is known for selling things that don't actually exist, so there is a healthy bit of distrust that they actually have the thing they are selling.

For example, they had ADM Ti rings on their site for like 3 years after they were announced, but they never made any.
Link Posted: 8/2/2023 11:32:08 AM EST
[#12]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By gongo:


Optics Planet has gained a certain reputation over the years of listing things as "in stock" but then taking 6-8 weeks to ship because it wasn't in stock.

I've ordered from them a bunch of times and never had any problems receiving my orders within 2 weeks, but I understand that many people are still reluctant to order from them because of the stories.

My guess is that when a couple of us posted about ordering on Optics Planet, those who already had ordered directly thought "yeah, so you saved $30, but you'll be waiting months to get it". Hence the indignation above that I got my order in just a week.
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Originally Posted By gongo:
Originally Posted By hdcharlie:
Originally Posted By backbencher:

"in stock"


?


Optics Planet has gained a certain reputation over the years of listing things as "in stock" but then taking 6-8 weeks to ship because it wasn't in stock.

I've ordered from them a bunch of times and never had any problems receiving my orders within 2 weeks, but I understand that many people are still reluctant to order from them because of the stories.

My guess is that when a couple of us posted about ordering on Optics Planet, those who already had ordered directly thought "yeah, so you saved $30, but you'll be waiting months to get it". Hence the indignation above that I got my order in just a week.


I've had good luck w/ em, but I've had an order held up for something that said it was in stock but wasn't - cancelled that item, and the rest shipped.
Link Posted: 8/2/2023 11:38:55 AM EST
[#13]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By gongo:

Optics Planet has gained a certain reputation over the years of listing things as "in stock" but then taking 6-8 weeks to ship because it wasn't in stock.

I've ordered from them a bunch of times and never had any problems receiving my orders within 2 weeks, but I understand that many people are still reluctant to order from them because of the stories.

My guess is that when a couple of us posted about ordering on Optics Planet, those who already had ordered directly thought "yeah, so you saved $30, but you'll be waiting months to get it". Hence the indignation above that I got my order in just a week.
View Quote

I'll note that as I do not have a "Harambe-like" physique, I have zero interest in the Maxim Defense product; that said, I was "Brownelled" by Optics Planet twice (I try to give a vendor two bites at the apple), so I'll never order from them again.
Best of luck to all.
MHO, YMMV, etc.
Link Posted: 8/2/2023 3:21:32 PM EST
[#14]
Mine got to the local post office today… should be here tomorrow when I get back from work.
Link Posted: 8/2/2023 3:44:26 PM EST
[#15]
My order for additional Maxim units, that were ordered on 7/29 from Optics Planet, are being ordered today. Some of you "doubting Thomases" are missing the boat. This is one of a couple orders I have placed with them recently that were received without issue. YMMV

Please continue to not order from them so there'll be more parts for me.
Link Posted: 8/2/2023 4:17:41 PM EST
[Last Edit: texaspaulhouston] [#16]
So received mine yesterday installed and went to range. By the way no instructions and I received from Optic Planet.

Shot

S&B 115 factory loads, much reduced recoil from previous buffer systems. Cycled 100%
Reload 100 Berry's 3.5 N320. Cycled 100%
Reload 137 BMB coated, 3.1 Clean Shot. Cycled 100%
Reload 127 BMB coated, 3.1 Clean Shot.  Cycled 100%

Factroy ammo had most gun movement, the 100's was really soft and small movement.  The other two was a pinch more than the 100.

I am impressed.  Was worried the light ammo would not cycle, but not the case.  My TACCOM MDRS work equal to this but is much more tunable to the load and is a tad bit softer as it is tuned to the 100 Berry's.  If you run factory ammo and do not want to switch between low PF and high PF ammo, this works.  There is currently on tuning of this unit.

Now the turd in the punch bowl. This thing is hard to charge.  With a normal mid-sized charging handle, it was tough to charge.  Butt plate in center of chest and pull hard and tough on fingers. I then switched to Gibbs side cocker upper, better but still tough on fingers. You could not just reach up while butt plate in shoulder and charge the unit. It took some repositioning of the gun. I shoot steel with this gun so no critical fast charging needed, but if I did need speed this would not be my setup.  I did purchase a Levar charging handle, and this made a big difference on the forced needed to charge.  The downside is it is somewhat cumbersome to flip and un-flip the extended handle.

Overall, it will be in the gun for Steel Challange match this Saturday for a review.
Link Posted: 8/2/2023 8:31:01 PM EST
[#17]
My order from Optics Planet arrived today. Still no instructions, just like everyone else's experience. Evidently Maxim just wants you to install it in the buffer tube and shoot. Don't need no stinkin' instructions.
Link Posted: 8/3/2023 9:51:42 AM EST
[#18]
I just want to say, as someone that is interested in one of these but hasn't bought one yet, I truly appreciate all of you purchasing one and testing them for the rest of us!
Link Posted: 8/3/2023 9:52:38 AM EST
[#19]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Neomonk21:
I just want to say, as someone that is interested in one of these but hasn't bought one yet, I truly appreciate all of you purchasing one and testing them for the rest of us!
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Indeed.
Link Posted: 8/3/2023 5:22:32 PM EST
[#20]
So, I got mine today... same box, no paperwork.

Started off with weighing my AR-9... 6 pounds, 12.7 ounces. Stern conversion that I swapped a slick upper on (6" barrel, 8" forend), Dead Air Odessa, SIG Romeo5, Surefire Scout light, Magpul MBUS, MFT Minimalist stock and an 11-ounce buffer (runs the suppressor at all times). SBRed... in case ATF is looking in.

Pulled out the buffer and retainer pin... put it back together to see how bad it is to charge... DOESN'T MOVE! Duh, got to remove the bolt weight.

Do that, put it back together and noticed that it was preloading the buffer. Wasn't too bad to charge. Since I had it somewhat apart, I backed the buffer tube out a turn. It seems like the bolt and buffer are just touching, but not to the point that it is pushing back on the buffer assembly. Put it back together... it was tougher, but not too much more. Charging handle is a Gas Buster 9mm with the Combat Latch.

I'm leaving it in the backed out position, mainly because I want as much delay as possible... being the gun runs suppressed 100% of the time.

Final weight after the Maxim install... 6 pounds, 6.3 ounces. All the parts removed (buffer, spring, bolt weight, retainer pin/spring) come out to 14.8 ounces. It feels noticeably lighter but did get slightly nose heavy. I'm not off for a decent amount of time until the middle of the month, but I'll be going to the range with it to test it out. Recoil and suppression are the bigger things. If I get the extra turn on the buffer and no worse in the sound department... I'll likely do that (slightly easier to charge). But I have a feeling this is the answer to the 11-ounce buffer.
Link Posted: 8/4/2023 5:56:35 AM EST
[#21]
I finally received and tried out the Radian Raptor LT (R0148) and the Springfield LevAR charging handles. Compared to a Vltor Mod 2 and the Aero Breach, the Radian Raptor is indeed better to use. It feels much better on the hand/fingers, making it easier to apply the force needed to pull the Maxim out of battery. The Raptor would be my choice for use with the Maxim RDB. One-handed charging is more comfortable, but it's not "easier" force-wise. It's the same amount of resistance.

The LevAR's cam system is a very clever bit of engineering and actually reduces the charging force a lot, making it much easier to charge, but it's awkward to use. If I were to use it, I would just deploy the lever arm and leave it out.  If you get one, be sure to oil the heck out of it.  It comes completely dry.

No, I haven't gotten back out to the range to put more rounds through the Maxim.  Hopefully soon.
Link Posted: 8/4/2023 6:12:37 AM EST
[#22]
Has anyone other than myself shot theirs with a suppressor yet?
Curious if others experienced the same thing with poor suppressed performance (loud).
Link Posted: 8/4/2023 9:41:21 AM EST
[Last Edit: gotigers] [#23]
And so it begins.

Ordered 7/27 from Optics Planet, $168 shipped, received 8/3. No instructions. Just a small box and a bit of bubble wrap.

Very good finish and seems to be very well made.

I will shoot with it this weekend and report back.

Attachment Attached File
Link Posted: 8/4/2023 5:44:05 PM EST
[Last Edit: gotigers] [#24]
I was able to put 60 or so rounds through my AR9 with the new buffer after work.

- Before and after is amazing. This is the softest shooting AR9 i have shot. I cannot stress how nice this is to shoot.

- The first few charges were very stiff, but now it is no much stiffer than the old buffer spring.

- I had one auto-type burst. I was lightly holding the grip and forearm trying to see how it fired with very little applied force. It could have been a bounce off my shoulder and a double tap of the trigger. The trigger is a Geissele B-GRF rapid fire trigger. It resets faster than any trigger i have shot.  I am not to concerned about this issue since it was a one off and probably caused by me.

- My only real concern is that I had 5-6 dead triggers. Maybe a short stroke. The trigger did not reset. Anyone have this issue?


edit: my build :
Barrel: 16" Kaw Valley Precision 4150 QPQ
Upper: Spartan 9MM/45ACP Non-Reciprocating Side Charge Billet Upper Receiver w/ LRBHO
Lower: Spartan-9mm Glock Magazine Compatible Billet Lower Receiver
Bolt: Kaw Valley Precision 9mm BlowBack Bolt Carrier Group
Trigger: Geissele B-GRF rapid fire trigger

buffer before the Maxim Defense RDB was a KYNTEC CORP AR-15 AR HYDRAULIC
Link Posted: 8/4/2023 7:44:03 PM EST
[#25]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By gotigers:
- The first few charges were very stiff, but now it is no much stiffer than the old buffer spring.

- I had one auto-type burst. I was lightly holding the grip and forearm trying to see how it fired with very little applied force. It could have been a bounce off my shoulder and a double tap of the trigger. The trigger is a Geissele B-GRF rapid fire trigger. It resets faster than any trigger i have shot.  I am not to concerned about this issue since it was a one off and probably caused by me.

- My only real concern is that I had 5-6 dead triggers. Maybe a short stroke. The trigger did not reset. Anyone have this issue?
View Quote

I think the spring on this thing is too stiff. I'm storing it with the bolt locked back to see if the spring will "take a set" and loosen up a little.
Still haven't shot mine yet but I see that the Optics Planet units have earlier production serial numbers than the ones people have been receiving from Maxim directly.
I found that it's actually easier to just remove my trigger hammer when pulling out the buffer unit rather than fiddling with it and having to wrestle it over the hammer.
It seems to me that adding a little mass to the spool/cylinder that gets blown back would increase the mechanical disadvantage and slow the bolt more than the heavy spring.
Link Posted: 8/4/2023 8:13:09 PM EST
[#26]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By gotigers: My only real concern is that I had 5-6 dead triggers. Maybe a short stroke. The trigger did not reset. Anyone have this issue?
View Quote


As I believe I noted earlier, mine would do this with regular 115gr ball, but worked perfectly with anything hotter or heavier. That was early on and I haven't tried 115 again since having fired a bunch of hotter stuff. I'll give it another chance when I return to the range.
Link Posted: 8/4/2023 9:49:49 PM EST
[#27]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By gotigers:
I was able to put 60 or so rounds through my AR9 with the new buffer after work.

- Before and after is amazing. This is the softest shooting AR9 i have shot. I cannot stress how nice this is to shoot.

- The first few charges were very stiff, but now it is no much stiffer than the old buffer spring.

- I had one auto-type burst. I was lightly holding the grip and forearm trying to see how it fired with very little applied force. It could have been a bounce off my shoulder and a double tap of the trigger. The trigger is a Geissele B-GRF rapid fire trigger. It resets faster than any trigger i have shot.  I am not to concerned about this issue since it was a one off and probably caused by me.

- My only real concern is that I had 5-6 dead triggers. Maybe a short stroke. The trigger did not reset. Anyone have this issue?


edit: my build :
Barrel: 16" Kaw Valley Precision 4150 QPQ
Upper: Spartan 9MM/45ACP Non-Reciprocating Side Charge Billet Upper Receiver w/ LRBHO
Lower: Spartan-9mm Glock Magazine Compatible Billet Lower Receiver
Bolt: Kaw Valley Precision 9mm BlowBack Bolt Carrier Group
Trigger: Geissele B-GRF rapid fire trigger

buffer before the Maxim Defense RDB was a KYNTEC CORP AR-15 AR HYDRAULIC
View Quote


So I was playing around with some different triggers and found that some triggers wouldn't reset for me and the hammer would follow. I have the same BCG as you. Milspec, works great. CMC trigger worked. Geissle SDE didn't reset. RiseA - Rave didn't reset for me.  

Currently using a Trigger Tech and it works 100%.
Link Posted: 8/5/2023 9:39:53 AM EST
[Last Edit: SecondAmend] [#28]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By gongo:
I think the spring on this thing is too stiff. I'm storing it with the bolt locked back to see if the spring will "take a set" and loosen up a little....
It seems to me that adding a little mass to the spool/cylinder that gets blown back would increase the mechanical disadvantage and slow the bolt more than the heavy spring.
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A better solution would be to use a flat wire spring with a lower spring rate but with more coils hence longer overall length such that the same total kinetic energy absorption is achieved, as is commonly done on pistols.

MHO, YMMV, etc.

ETA: More coils hence longer overall length does, of course, add slightly more reciprocating mass.
Link Posted: 8/6/2023 1:23:40 PM EST
[#29]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By amphibian:
Has anyone other than myself shot theirs with a suppressor yet?
Curious if others experienced the same thing with poor suppressed performance (loud).
View Quote

I have, and I liked the performance so much that I ordered a second, and then third RDB.    It is the quietest spring configuration that I have found for my 8" suppressed 9mm AR.  Port pop was nearly eliminated.
Link Posted: 8/7/2023 11:17:13 AM EST
[Last Edit: bones12345] [#30]
Appreciate the effort and investment everyone has put into this so far.

Quick question as I don't think it's been mentioned but what do y'all think about short-stroking this thing?

Seems as easy as a longer delrin spacer, but not sure if there are any reasons it's a bad idea that I can't think of.

Thanks!
Link Posted: 8/8/2023 6:43:53 AM EST
[#31]
I just ordered a force meter and a set of JP SCS springs for experimentation.  I suspect we can reduce the spring tension a bit and still benefit from the roller delay.  I have an MP5 to compare it to, so once I can get an accurate force required to overcome the MP5 rollers, I'll see if the Maxim matches it or is stronger (I believe it's stronger) and see if reducing spring tension has a positive effect.

Plus the MP5 only has about 9oz of mass to the bolt/carrier while the Maxim has about 16oz with a normal 9mm bolt - nearly double, making me think we can use significantly less spring tension while maintaining safe operation.  I'll need to fire up the high speed camera and count frames to get some bolt velocity measurements.  Haven't tried that before, but hopefully I can find some software that'll advance frame by frame on the raw video.
Link Posted: 8/8/2023 3:47:10 PM EST
[#32]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Droppoint:
I just ordered a force meter and a set of JP SCS springs for experimentation.  I suspect we can reduce the spring tension a bit and still benefit from the roller delay.  I have an MP5 to compare it to, so once I can get an accurate force required to overcome the MP5 rollers, I'll see if the Maxim matches it or is stronger (I believe it's stronger) and see if reducing spring tension has a positive effect.

Plus the MP5 only has about 9oz of mass to the bolt/carrier while the Maxim has about 16oz with a normal 9mm bolt - nearly double, making me think we can use significantly less spring tension while maintaining safe operation.  I'll need to fire up the high speed camera and count frames to get some bolt velocity measurements.  Haven't tried that before, but hopefully I can find some software that'll advance frame by frame on the raw video.
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When I was showing my Maxim buffer to someone after a recent match, I pulled the collar back to show the bearings, which of course made them fall out.   I had thought they were captured, but they were apparently held in with grease.  Perhaps the unlocking could be tuned by removing a couple of the bearings?
Link Posted: 8/9/2023 9:33:18 PM EST
[#33]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Droppoint:
I just ordered a force meter and a set of JP SCS springs for experimentation.  I suspect we can reduce the spring tension a bit and still benefit from the roller delay.  I have an MP5 to compare it to, so once I can get an accurate force required to overcome the MP5 rollers, I'll see if the Maxim matches it or is stronger (I believe it's stronger) and see if reducing spring tension has a positive effect.

Plus the MP5 only has about 9oz of mass to the bolt/carrier while the Maxim has about 16oz with a normal 9mm bolt - nearly double, making me think we can use significantly less spring tension while maintaining safe operation.  I'll need to fire up the high speed camera and count frames to get some bolt velocity measurements.  Haven't tried that before, but hopefully I can find some software that'll advance frame by frame on the raw video.
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I guess you'll need to measure the force with the hammer down as well as add in the weight of the hammer for both systems?
Maybe it doesn't make a difference, but it seems to me like the hammer and hammer spring would need to be accounted for since the recoil stroke happens with the hammer down after pulling the trigger.
Link Posted: 8/9/2023 9:50:17 PM EST
[#34]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Droppoint:
 I suspect we can reduce the spring tension a bit and still benefit from the roller delay.  I have an MP5 to compare it to, so once I can get an accurate force required to overcome the MP5 rollers, I'll see if the Maxim matches it or is stronger (I believe it's stronger) and see if reducing spring tension has a positive effect.

View Quote


I would think you would want to remove the cap on the front of the MP5 cocking tube, and use a rod centered in the tube to measure the resistance on an MP5.  Measuring at the cocking handle might give you some drag from off-axis force on the charging handle.
Link Posted: 8/9/2023 10:23:14 PM EST
[#35]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Droppoint:
I just ordered a force meter and a set of JP SCS springs for experimentation.  I suspect we can reduce the spring tension a bit and still benefit from the roller delay.  I have an MP5 to compare it to, so once I can get an accurate force required to overcome the MP5 rollers, I'll see if the Maxim matches it or is stronger (I believe it's stronger) and see if reducing spring tension has a positive effect.

Plus the MP5 only has about 9oz of mass to the bolt/carrier while the Maxim has about 16oz with a normal 9mm bolt - nearly double, making me think we can use significantly less spring tension while maintaining safe operation.  I'll need to fire up the high speed camera and count frames to get some bolt velocity measurements.  Haven't tried that before, but hopefully I can find some software that'll advance frame by frame on the raw video.
View Quote


I could be out in left field, but won't it be hard to compare the MP5 to the Maxim, because of the way the MP5 cocking handle uses leverage to break the rollers free, sort of like the way the LevAR works on an AR.
Link Posted: 8/10/2023 12:20:21 AM EST
[#36]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:


I could be out in left field, but won't it be hard to compare the MP5 to the Maxim, because of the way the MP5 cocking handle uses leverage to break the rollers free, sort of like the way the LevAR works on an AR.
View Quote

True story. You would have to stick a rod down from the muzzle so that you're pushing against the bolt face just like the case head does.
Link Posted: 8/10/2023 8:58:16 AM EST
[Last Edit: Droppoint] [#37]
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Originally Posted By gongo:

True story. You would have to stick a rod down from the muzzle so that you're pushing against the bolt face just like the case head does.
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This is exactly what I was planning on doing and just bought a digital force gauge with peak recording for this exact purpose. Should be more accurate than the crane scale I was using where I had to try to catch the peak reading on camera.  Received it yesterday.  Checked calibration, seems to be accurate.  Used an M92 cleaning rod to push against the bolt face down the muzzle.  Maxim has about 100 rounds on it so far, MP5 has a lot more.

Digital force gauge readings: (for all 2 of you that care...)

MP5, standard trigger pack hammer spring:

MP5 @ Down the muzzle:
Hammer back: ~24lbs. to push the rollers out of battery
Hammer forward: ~32lbs.

MP5 @ Charging handle:
Hammer back: ~11lbs to start the handle moving.
Hammer forward: ~20lbs to cock the hammer.

AR9, Maxim roller delay, Aim SSTAT (Rise 140 clone) trigger:

Maxim @ Down the muzzle:
Hammer back: ~24lbs. to push the rollers out of battery
Hammer forward: ~26lbs.

Maxim @ Charging handle (raptor-lt):
Hammer back: ~28lbs. to start the handle moving.
Hammer forward: ~31lbs.

I was going to experiment with the JP SCS springs I just ordered... Looks like it's about as good as it'll get.  I'll have to sell them or return them when I get them in.
Link Posted: 8/10/2023 9:03:57 AM EST
[#38]
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Originally Posted By Droppoint:

Digital force gauge readings: (for all 2 of you that care...)

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I care!  Thanks for doing that!
Link Posted: 8/10/2023 9:23:58 AM EST
[#39]
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Originally Posted By Droppoint:

This is exactly what I was planning on doing and just bought a digital force gauge with peak recording for this exact purpose. Should be more accurate than the crane scale I was using where I had to try to catch the peak reading on camera.  Received it yesterday.  Checked calibration, seems to be accurate.  Used an M92 cleaning rod to push against the bolt face down the muzzle.  Maxim has about 100 rounds on it so far, MP5 has a lot more.

Digital force gauge readings: (for all 2 of you that care...)

MP5, standard trigger pack hammer spring:

MP5 @ Down the muzzle:
Hammer back: ~24lbs. to push the rollers out of battery
Hammer forward: ~32lbs.

MP5 @ Charging handle:
Hammer back: ~11lbs to start the handle moving.
Hammer forward: ~20lbs to cock the hammer.

AR9, Maxim roller delay, Aim SSTAT (Rise 140 clone) trigger:

Maxim @ Down the muzzle:
Hammer back: ~24lbs. to push the rollers out of battery
Hammer forward: ~26lbs.

Maxim @ Charging handle (raptor-lt):
Hammer back: ~28lbs. to start the handle moving.
Hammer forward: ~31lbs.

I was going to experiment with the JP SCS springs I just ordered... Looks like it's about as good as it'll get.  I'll have to sell them or return them when I get them in.
View Quote


So, I gather from the above, the LevAR might be the only way to simulate the cocking effort of the MP5, at least so far.
Link Posted: 8/10/2023 9:48:38 AM EST
[#40]
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Originally Posted By hdcharlie:


So, I gather from the above, the LevAR might be the only way to simulate the cocking effort of the MP5, at least so far.
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So far, yes.  It uses 3:1 leverage to cam the bolt past the "wall".  I swapped in the LevAR this morning and it's definitely easier, but it's a little awkward for me to use because I have to switch hands and it operates in two distinct steps - break free then retract.  I'm used to single-wing cocking from the left side in one smooth motion.

I tried to blade-palm it, and that was a no-go.
Link Posted: 8/10/2023 10:22:10 AM EST
[#41]
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Originally Posted By Droppoint:

So far, yes.  It uses 3:1 leverage to cam the bolt past the "wall".  I swapped in the LevAR this morning and it's definitely easier, but it's a little awkward for me to use because I have to switch hands and it operates in two distinct steps - break free then retract.  I'm used to single-wing cocking from the left side in one smooth motion.

I tried to blade-palm it, and that was a no-go.
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Maybe Springfield could be convinced to put the lever on the left side.

All my favorite AR9s have a NFA left-side charger upper.
Link Posted: 8/10/2023 12:09:38 PM EST
[#42]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Droppoint:

This is exactly what I was planning on doing and just bought a digital force gauge with peak recording for this exact purpose. Should be more accurate than the crane scale I was using where I had to try to catch the peak reading on camera.  Received it yesterday.  Checked calibration, seems to be accurate.  Used an M92 cleaning rod to push against the bolt face down the muzzle.  Maxim has about 100 rounds on it so far, MP5 has a lot more.

Digital force gauge readings: (for all 2 of you that care...)

MP5, standard trigger pack hammer spring:

MP5 @ Down the muzzle:
Hammer back: ~24lbs. to push the rollers out of battery
Hammer forward: ~32lbs.

MP5 @ Charging handle:
Hammer back: ~11lbs to start the handle moving.
Hammer forward: ~20lbs to cock the hammer.

AR9, Maxim roller delay, Aim SSTAT (Rise 140 clone) trigger:

Maxim @ Down the muzzle:
Hammer back: ~24lbs. to push the rollers out of battery
Hammer forward: ~26lbs.

Maxim @ Charging handle (raptor-lt):
Hammer back: ~28lbs. to start the handle moving.
Hammer forward: ~31lbs.

I was going to experiment with the JP SCS springs I just ordered... Looks like it's about as good as it'll get.  I'll have to sell them or return them when I get them in.
View Quote

Aren't the MP5 results going to depend on which degree angle block you have installed?
Link Posted: 8/10/2023 12:14:37 PM EST
[#43]
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Originally Posted By SecondAmend:

Aren't the MP5 results going to depend on which degree angle block you have installed?
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Of course.  It's whatever comes standard in an MP5.
Link Posted: 8/14/2023 10:06:12 AM EST
[#44]
Follow up on my post about dead triggers.

I tried a mil-spec trigger based on suggestions in this thread. It is an ALG ACT with JP yellow springs i had laying around. 4lb break. I still had a couple of dead triggers out of 100.

As i was shooting a good friend came by the bay. He is a machinist and builds all his own guns for competition. He has done it all. He said, he has seen dead triggers a lot with AR9s. The blowback is so hard and fast that the hammer horn bounces the disconnect and is following the bolt. His suggestion was to cut off the horn on the back of the hammer. He said it works without fail for mil-spec triggers.

I cut the horn off the hammer and put another shot another 100 rounds. I had no dead triggers.

This is now my favorite gun to shoot. I spread a bunch of 6" and 10" steel plates all over the bay. Double taps and transitions are just too easy. Recoil is as flat as i've shot.

If it changes, i'll report back.


Discussion ForumsJump to Quoted PostQuote History
Originally Posted By gotigers:
I was able to put 60 or so rounds through my AR9 with the new buffer after work.

- Before and after is amazing. This is the softest shooting AR9 i have shot. I cannot stress how nice this is to shoot.

- The first few charges were very stiff, but now it is no much stiffer than the old buffer spring.

- I had one auto-type burst. I was lightly holding the grip and forearm trying to see how it fired with very little applied force. It could have been a bounce off my shoulder and a double tap of the trigger. The trigger is a Geissele B-GRF rapid fire trigger. It resets faster than any trigger i have shot.  I am not to concerned about this issue since it was a one off and probably caused by me.

- My only real concern is that I had 5-6 dead triggers. Maybe a short stroke. The trigger did not reset. Anyone have this issue?


edit: my build :
Barrel: 16" Kaw Valley Precision 4150 QPQ
Upper: Spartan 9MM/45ACP Non-Reciprocating Side Charge Billet Upper Receiver w/ LRBHO
Lower: Spartan-9mm Glock Magazine Compatible Billet Lower Receiver
Bolt: Kaw Valley Precision 9mm BlowBack Bolt Carrier Group
Trigger: Geissele B-GRF rapid fire trigger

buffer before the Maxim Defense RDB was a KYNTEC CORP AR-15 AR HYDRAULIC
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Link Posted: 8/14/2023 12:25:43 PM EST
[Last Edit: hdcharlie] [#45]
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Originally Posted By gotigers:
I was able to put 60 or so rounds through my AR9 with the new buffer after work.

- Before and after is amazing. This is the softest shooting AR9 i have shot. I cannot stress how nice this is to shoot.

- The first few charges were very stiff, but now it is no much stiffer than the old buffer spring.
View Quote


For anyone contemplating buying one of the Maxim units, the statements above cannot be emphasized too much. I had my 16" barreled AR9 at the range for the first time this morning that has one of these units installed. The difference in the felt recoil compared to the previous Kynshot 5007, Wilson Combat buffer spring combination is nothing short of amazing. The initial cocking effort is horrible, but after about 80 rds of 124gr +P ammo, it is not much worse than the Kynshot setup. And, I have a feeling the cocking effort will continue to improve with more rounds fired.

I wish this Maxim unit had become available before I spent so much money on the Kynshot buffers. There is absolutely no comparison.

Oh, and I have had absolutely no dead triggers using a Nickel/Teflon g.i. trigger. In fact, my trigger/hammer have the lightweight KAK spring set installed and work perfectly.
Link Posted: 8/14/2023 1:59:11 PM EST
[#46]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:


For anyone contemplating buying one of the Maxim units, the statements above cannot be emphasized too much. I had my 16" barreled AR9 at the range for the first time this morning that has one of these units installed. The difference in the felt recoil compared to the previous Kynshot 5007, Wilson Combat buffer spring combination is nothing short of amazing. The initial cocking effort is horrible, but after about 80 rds of 124gr +P ammo, it is not much worse than the Kynshot setup. And, I have a feeling the cocking effort will continue to improve with more rounds fired.

I wish this Maxim unit had become available before I spent so much money on the Kynshot buffers. There is absolutely no comparison.

Oh, and I have had absolutely no dead triggers using a Nickel/Teflon g.i. trigger. In fact, my trigger/hammer have the lightweight KAK spring set installed and work perfectly.
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:
Originally Posted By gotigers:
I was able to put 60 or so rounds through my AR9 with the new buffer after work.

- Before and after is amazing. This is the softest shooting AR9 i have shot. I cannot stress how nice this is to shoot.

- The first few charges were very stiff, but now it is no much stiffer than the old buffer spring.


For anyone contemplating buying one of the Maxim units, the statements above cannot be emphasized too much. I had my 16" barreled AR9 at the range for the first time this morning that has one of these units installed. The difference in the felt recoil compared to the previous Kynshot 5007, Wilson Combat buffer spring combination is nothing short of amazing. The initial cocking effort is horrible, but after about 80 rds of 124gr +P ammo, it is not much worse than the Kynshot setup. And, I have a feeling the cocking effort will continue to improve with more rounds fired.

I wish this Maxim unit had become available before I spent so much money on the Kynshot buffers. There is absolutely no comparison.

Oh, and I have had absolutely no dead triggers using a Nickel/Teflon g.i. trigger. In fact, my trigger/hammer have the lightweight KAK spring set installed and work perfectly.

With all due respect, per KynSHOT, the RB5007 should not be used with any barrel length over 8 in. or with a silencer.  You should have tried a KynSHOT 5015HD.  The KynSHOT 5015HD is what I use with a 16 in. barrel and standard recoil spring.

MHO, VMMV, etc.  Be well.
Link Posted: 8/14/2023 2:38:46 PM EST
[#47]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:


For anyone contemplating buying one of the Maxim units, the statements above cannot be emphasized too much. I had my 16" barreled AR9 at the range for the first time this morning that has one of these units installed. The difference in the felt recoil compared to the previous Kynshot 5007, Wilson Combat buffer spring combination is nothing short of amazing. The initial cocking effort is horrible, but after about 80 rds of 124gr +P ammo, it is not much worse than the Kynshot setup. And, I have a feeling the cocking effort will continue to improve with more rounds fired.

I wish this Maxim unit had become available before I spent so much money on the Kynshot buffers. There is absolutely no comparison.

Oh, and I have had absolutely no dead triggers using a Nickel/Teflon g.i. trigger. In fact, my trigger/hammer have the lightweight KAK spring set installed and work perfectly.
View Quote


Awesome.  Thank you for the review.
Link Posted: 8/14/2023 3:37:19 PM EST
[#48]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By SecondAmend:

With all due respect, per KynSHOT, the RB5007 should not be used with any barrel length over 8 in. or with a silencer.  You should have tried a KynSHOT 5015HD.  The KynSHOT 5015HD is what I use with a 16 in. barrel and standard recoil spring.

MHO, VMMV, etc.  Be well.
View Quote


I've used both the 5007 and the 5015. Didn't see much difference.
Link Posted: 8/14/2023 4:42:25 PM EST
[#49]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:


For anyone contemplating buying one of the Maxim units, the statements above cannot be emphasized too much.
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:
Originally Posted By gotigers:
I was able to put 60 or so rounds through my AR9 with the new buffer after work.

- Before and after is amazing. This is the softest shooting AR9 i have shot. I cannot stress how nice this is to shoot.

- The first few charges were very stiff, but now it is no much stiffer than the old buffer spring.


For anyone contemplating buying one of the Maxim units, the statements above cannot be emphasized too much.
My issue is the poor suppression performance.  Maybe I need to put some more rounds downrange and see if things change?....
However, I would think if it gets easier to charge then it would have less delay??
Link Posted: 8/14/2023 4:54:06 PM EST
[#50]
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Originally Posted By amphibian:
My issue is the poor suppression performance.  Maybe I need to put some more rounds downrange and see if things change?....
However, I would think if it gets easier to charge then it would have less delay??
View Quote


Being devils advocate, maybe a break-in was designed into the component. Hell, I don't know. All I know is it's a world of difference from any other buffer setup I've used.

I doubt many people have a suppressor to worry about how the thing works with one. I know I don't. Maybe the delay is what makes it louder.

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Maxim Defense RDB review (Page 8 of 11)
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