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Page AR-15 » Rimfire and Pistol Calibers
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Maxim Defense RDB review (Page 9 of 11)
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Link Posted: 8/14/2023 5:43:42 PM EST
[#1]
I ordered a carbine unit July 12th direct from maxim, no shipping info. Has anyone bought direct around that date and had it ship or been received yet.
fnh
Link Posted: 8/14/2023 6:20:50 PM EST
[#2]
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Originally Posted By hdcharlie:


I've used both the 5007 and the 5015. Didn't see much difference.
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Originally Posted By hdcharlie:
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.


I've used both the 5007 and the 5015. Didn't see much difference.

Here are some 9mm (AE 115 gr. round nose ammo) Rate Of Fire (ROF) numbers (in Rounds Per Minute) yielded by several AR pattern recoil buffers.  The firearm used: Colt M16A1 with a Gibbz side charge upper and Colt 16 in. bbl., standard unknown brand 9mm direct blowback bolt (approx. weight 15.4 oz.), standard stainless steel carbine length recoil spring in a standard carbine length buffer tube.  The only thing changed between test runs (10 rounds each) was the buffer.  Not all tests were performed on the same day. Buffer approximate weight is given in ounces in parentheses, ROF value is after the colon.

Standard “9mm two-piece mechanical” [Baseline; control reference] (5.6): ave. ~875;

KynSHOT RB5007 (low damped) hydraulic (6.1 oz.): Ave. of 2 runs = 930

KynSHOT RB5015HD (6.1): 765; and

B & T AR9 AR15 (6.1): ave. ~700

Disclaimer:  I have no affiliation with or financial interest in any vendor or manufacturer.  I am not a competitive shooter or a blogger who receives any form of compensation or sponsorship for endorsements, or favorable public or private comments.  I do not have a website, podcasts, webinars, or online videos; or books/magazine articles.  Use of vendor and/or product brand names, if any, is for informational purposes only; and products or services were purchased by me from regular commercial sources.

Best of luck.
MHO, YMMV, etc.  Be well.
Link Posted: 8/14/2023 8:51:38 PM EST
[#3]
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


Went back and checked Kynshot's site. The description for the 5007 says it is designed for use with 3.5"-16" barrels firing common types of ammo, but then says the 5015 is for 8" or longer barrels firing any type of ammo. It also states either can be used suppressed or unsuppressed. Conflicting and confusing.
Link Posted: 8/15/2023 7:31:22 PM EST
[#4]
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Originally Posted By StaccatoC2:
I ordered a carbine unit July 12th direct from maxim, no shipping info. Has anyone bought direct around that date and had it ship or been received yet.
View Quote


I placed an order through Maxim for the carbine version on June 13 and while I have had responses via email promising to deliver “in a couple / few weeks“ a few times, I still have not received any tracking info etc.

That’s 9 weeks to the day. I’ll send them another email and see if I get a response. I’m hoping the new batch will have improvements including instructions. We’ll see I guess.
Link Posted: 8/15/2023 7:40:40 PM EST
[#5]
I hope someone comes up with a good reliable delayed system.
I mostly want a delay to minimize the gas to the face I get every time I shoot supressed.
I have a very heavy buffer and a Gibbz side charging upper and Im not sure it even helps.
Of course I shoot lefty most of the time so thats not helping.  I shoot fine righty too but its not 100%.

Lower recoil would be nice but current recoil doesnt bother me.
Link Posted: 8/16/2023 1:05:39 AM EST
[Last Edit: 1168RGR] [#6]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By networkguru:
I hope someone comes up with a good reliable delayed system.
I mostly want a delay to minimize the gas to the face I get every time I shoot supressed.
I have a very heavy buffer and a Gibbz side charging upper and Im not sure it even helps.
Of course I shoot lefty most of the time so thats not helping.  I shoot fine righty too but its not 100%.

Lower recoil would be nice but current recoil doesnt bother me.
View Quote


Do you handload? And what can are you using?
Link Posted: 8/16/2023 9:29:05 AM EST
[#7]
I was able to get in touch with Tim. My interactions with him have been very positive and it sounds like the June / July guys will have a shipment coming by the end of the month. Also Maxim has been quite active in fighting the batfe on the brace issue so I feel even better about at least trying the RDS.

I guess when you make really cool stuff it’s hard to gauge interest. Just based on observations I would say less than 500 of these are in the wild. Anyone remember the number of units available from optics planet early on for the carbine model?
Link Posted: 8/16/2023 10:28:30 AM EST
[#8]
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Originally Posted By Park-Hit-Run:Anyone remember the number of units available from optics planet early on for the carbine model?
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IIRC they had about 25.
Link Posted: 8/17/2023 2:15:10 AM EST
[Last Edit: chevrofreak] [#9]
My Optics Planet order came in several days ago and it is serial number CAR-0004, so either Optics Planet got their first production run or they are recycling serial numbers.
Link Posted: 8/17/2023 9:21:41 AM EST
[Last Edit: SecondAmend] [#10]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By chevrofreak:
My Optics Planet order came in several days ago and it is serial number CAR-0004, so either Optics Planet got their first production run or they are recycling serial numbers.
View Quote

Or maybe by the time it got to the original buyer they had read the reviews at how hard the unit is to cock and decided that they didn't want to deal with it; and returned the one you now have, package unopened, to Optics Planet who then sold it to you.

Or maybe Optics Planet has a stack of them in their warehouse and just grab them in no particular order.

Just sayin'
Good luck.
MHO, YMMV, etc.  Be well.
Link Posted: 8/18/2023 1:35:24 PM EST
[#11]
I have no idea if this will work but hope to find out this weekend:

Link Posted: 8/19/2023 5:51:33 PM EST
[#12]
Shot this setup today...Very smooth and quiet.  
I definitely recommend the Maxim Defense delayed blowback setup in conjunction with the FM9.  
I am glad I have good configuration to use with the Maxim Defense RDB


Link Posted: 8/20/2023 3:23:00 PM EST
[#13]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By SecondAmend:

Or maybe by the time it got to the original buyer they had read the reviews at how hard the unit is to cock and decided that they didn't want to deal with it; and returned the one you now have, package unopened, to Optics Planet who then sold it to you.

Or maybe Optics Planet has a stack of them in their warehouse and just grab them in no particular order.

Just sayin'
Good luck.
MHO, YMMV, etc.  Be well.
View Quote


I purchased another Maxim buffer from a friend that had also ordered from Optics Planet, but about a week after I did, and that serial is CAR-0035.
Link Posted: 8/21/2023 2:21:07 PM EST
[#14]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By amphibian:  Shot this setup today...Very smooth and quiet.  
I definitely recommend the Maxim Defense delayed blowback setup in conjunction with the FM9.  
I am glad I have good configuration to use with the Maxim Defense RDB
https://c3junkie.com/wp-content/uploads/2023/08/FM9-MaximRDB-RPM.jpg
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Thank you for testing that.  You have a very good combination of kewl toys that work together.
Link Posted: 8/25/2023 8:58:40 PM EST
[#15]
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 run both on barrels from 5” to 16” without issues.
Link Posted: 8/27/2023 12:24:43 PM EST
[Last Edit: R1valdez] [#16]
Anybody that ordered on July got a shipment notification yet? I ordered mines on 4th of July and nothing yet
Link Posted: 8/27/2023 1:06:53 PM EST
[Last Edit: Utahshooting] [#17]
Maybe a dumb question, but does this work with a PSA AR-V?  It will be shot suppressed 100% of the time with 147 gr subs. As a Lefty, the AR-V puts out a fair amount of gas. Installed an Odin works Zulu buffer tube/stock with secondary buffer and it helped a lot but it's still gassy
Link Posted: 8/27/2023 1:25:48 PM EST
[#18]
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Originally Posted By Utahshooting:
Maybe a dumb question, but does this work with a PSA AR-V?  It will be shot suppressed 100% of the time with 147 gr subs. As a Lefty, the AR-V puts out a fair amount of gas. Installed an Odin works Zulu buffer tube/stock with secondary buffer and it helped a lot but it's still gassy
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I can't think of any reason why it wouldn't.
Link Posted: 8/28/2023 7:54:06 AM EST
[#19]
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Originally Posted By hdcharlie:


I can't think of any reason why it wouldn't.
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I might pick up one of these for my AR-V after I get it SBR'd.  It currently shoots great with the KAC buffer kit in it but I absolutely HATE the rattle of the weights in the buffer.
Link Posted: 8/28/2023 10:23:54 AM EST
[Last Edit: SecondAmend] [#20]
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Originally Posted By Neomonk21:


I might pick up one of these for my AR-V after I get it SBR'd.  It currently shoots great with the KAC buffer kit in it but I absolutely HATE the rattle of the weights in the buffer.
View Quote

FWIW, tungsten powder, hydraulic, solid, and at least some lead shot filled and magnetic AR buffers don't rattle; and there might be others as well.  However, as a caution; as well as potentially higher cost, some "noiseless" AR buffers do not provide anti-bounce capability generally needed for full auto, and binary trigger or other high speed semi auto operation.

Best of luck.

MHO, YMMV, etc. Be well.
Link Posted: 8/28/2023 3:49:10 PM EST
[#21]
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Originally Posted By Neomonk21:
I might pick up one of these for my AR-V after I get it SBR'd.  It currently shoots great with the KAC buffer kit in it but I absolutely HATE the rattle of the weights in the buffer.
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So, I'm not trying to be a dick here, but when exactly does the buffer weight rattle bother you?  The rattle is so quiet I don't see how anyone can hear the weights move in the buffer, in the tube, under the stock, with earplugs in, over a shot or over spring noise.  Are you sure it's the buffer weights you're hearing?  Or is it just a psychological annoyance that the buffer rattles period?  Not judging, just curious.
Link Posted: 8/28/2023 3:52:49 PM EST
[#22]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By R1valdez:
Anybody that ordered on July got a shipment notification yet? I ordered mines on 4th of July and nothing yet
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Ordered 10th of July and have heard nothing as of yet...
Link Posted: 8/28/2023 7:03:33 PM EST
[#23]
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Originally Posted By Droppoint:

So, I'm not trying to be a dick here, but when exactly does the buffer weight rattle bother you?  The rattle is so quiet I don't see how anyone can hear the weights move in the buffer, in the tube, under the stock, with earplugs in, over a shot or over spring noise.  Are you sure it's the buffer weights you're hearing?  Or is it just a psychological annoyance that the buffer rattles period?  Not judging, just curious.
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I don't notice it when shooting.  I only notice it when handling it at home.  Every time I move it or dry fire with it I hear it.  It is definitely the buffer weights.  I noticed the sound they made when I first put the weights in the buffer when I was putting it together.  

It's kind of like when you notice your ceiling fan isn't balanced and the pull chain rattles.  Once you notice then it is all you notice until you fix it.  Or when some random plastic piece breaks off inside of your TV remote and rattles around.  Every time you pick it up you notice it rattle.  Random sounds like that drive me nuts, especially when I know they shouldn't be happening.  Normal AR rattles don't bother me but for some reason the rattling of the buffer in my AR-V just sticks out so much.  
Link Posted: 8/28/2023 7:12:54 PM EST
[#24]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Neomonk21:I don't notice it when shooting.  I only notice it when handling it at home.  Every time I move it or dry fire with it I hear it.  It is definitely the buffer weights.  I noticed the sound they made when I first put the weights in the buffer when I was putting it together.  
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Are you certain you have the weights spaced correctly and have the proper number of rubber discs between the weights. There shouldn't be very much free play in the weights and they should make next to no noise if the rubber discs are in place.
Link Posted: 8/29/2023 6:39:01 AM EST
[#25]
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Originally Posted By hdcharlie:


Are you certain you have the weights spaced correctly and have the proper number of rubber discs between the weights. There shouldn't be very much free play in the weights and they should make next to no noise if the rubber discs are in place.
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I'm fairly certain.  No directions came with the kit so I looked on their site.  At first I had all the rubber spacers in and the weights barely moved.  After looking on their site, I removed a spacer and that is how I am using it now.

Below is the parts list from their site.  They list 4 rubber spacer disks and 1 spare.  I believe I got 5 in my kit so I am running 4 spacers in my buffer.  I didn't put a spacer between the last weight and the rubber bumper.

Click To View Spoiler
Link Posted: 8/29/2023 1:05:07 PM EST
[#26]
Originally Posted By Neomonk21:


I'm fairly certain.  No directions came with the kit so I looked on their site.  At first I had all the rubber spacers in and the weights barely moved.  After looking on their site, I removed a spacer and that is how I am using it now.

Below is the parts list from their site.  They list 4 rubber spacer disks and 1 spare.  I believe I got 5 in my kit so I am running 4 spacers in my buffer.  I didn't put a spacer between the last weight and the rubber bumper.
View Quote
I have their 10oz (10.8, actual).  They should assembled into the body tube in this order: spacer1-weight1-spacer2-weight2-spacer3-weight3-spacer4-weight4-bumper, so there's always rubber/plastic against metal in the stack, never metal against metal. I really have to shake mine for them to make any discernable noise.  There's not much movement but it's enough to dampen bolt bounce.
Link Posted: 8/29/2023 2:13:41 PM EST
[#27]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Droppoint:
I have their 10oz (10.8, actual).  They should assembled into the body tube in this order: spacer1-weight1-spacer2-weight2-spacer3-weight3-spacer4-weight4-bumper, so there's always rubber/plastic against metal in the stack, never metal against metal. I really have to shake mine for them to make any discernable noise.  There's not much movement but it's enough to dampen bolt bounce.
View Quote



I'll take mine apart and double-check it.  Thanks for the help!
Link Posted: 8/30/2023 11:59:09 AM EST
[Last Edit: PreacherOfGadget] [#28]
I just ordered one through Optics Planet.

With the pre-Labor Day coupon code (LDAY) (10%), it's just below $154, with a bit over $18 back in store credit (bonus Optics Planet bucks) when it ships, with free shipping, for end price of about $136.

From Maxim there's a 15% off coupon available (heat15, on their main page) which drops the price to $171.41, but shipping is $9.95, for a total of about $181.

It's backordered either way, but OP might be more waiting...  and while waiting and having OP store credit isn't for everyone, after I got my Labor Day pre-sale coupon and saw the savings, I thought I'd share for any other budget-minded buyers out there.
Link Posted: 8/31/2023 9:55:21 AM EST
[#29]
I called Maxim yesterday and while they are always pleasant to talk with there is still no eta on the June / July orders. I’m over 11 weeks now. If I had known I wouldn’t see one from Maxim by now I would have cancelled and ordered one of the last few left at optics planet. Just a wait and see but really hoping to not get bit on this.
Link Posted: 8/31/2023 11:05:44 AM EST
[#30]
How are the few out there doing? Better with a fair bit of use but still a pain to charge?
Link Posted: 8/31/2023 7:28:14 PM EST
[Last Edit: jt526] [#31]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By NorthPolar:
How are the few out there doing? Better with a fair bit of use but still a pain to charge?
View Quote
Very hard, mine worked fine, I did maybe 400rds or so, and full auto, but I tossed it up on the EE as I was charged for my mean arms upper which should be on the way. If I already had a side charger I might have kept it for my current 9mm upper. But if the mean arms works that'll go too.
Link Posted: 8/31/2023 7:28:59 PM EST
[#32]
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Originally Posted By NorthPolar:
How are the few out there doing? Better with a fair bit of use but still a pain to charge?
View Quote

I don't think my charge force has decreased at all.  My girlfriend shot my competition PCC this past weekend and was still completely unable to move the charging handle.
Link Posted: 8/31/2023 7:37:16 PM EST
[#33]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By chevrofreak:

I don't think my charge force has decreased at all.  My girlfriend shot my competition PCC this past weekend and was still completely unable to move the charging handle.
View Quote


I hope it's not possible for the charge force to decrease. That could only happen if either one of two things happened, neither of which would be good. The spring could take a set or the bearings could start to wear into their seats. With the number of shots most of us probably have, if either of those things is happening, it won't bode well for long term durability.
Link Posted: 8/31/2023 7:53:34 PM EST
[#34]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By hdcharlie:


I hope it's not possible for the charge force to decrease. That could only happen if either one of two things happened, neither of which would be good. The spring could take a set or the bearings could start to wear into their seats. With the number of shots most of us probably have, if either of those things is happening, it won't bode well for long term durability.
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Agreed.
Link Posted: 9/1/2023 2:08:32 AM EST
[#35]
Thanks guys, I wasn't sure if it was a preload issue, break in, etc.  Guess one of these is off my list until there's a gen 2 version or something.
Link Posted: 9/1/2023 8:39:29 AM EST
[#36]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By NorthPolar:
Thanks guys, I wasn't sure if it was a preload issue, break in, etc.  Guess one of these is off my list until there's a gen 2 version or something.
View Quote


Preload could still be an issue, but unless or until Maxim gives us some guidance, anything in that arena would be speculation. I, personally, don't see preload being the correct setup, but we just don't know.

Hard to charge or not, so far I really like the way the a carbine functions with the Maxim installed.
Link Posted: 9/1/2023 11:18:31 AM EST
[#37]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By chevrofreak:

I don't think my charge force has decreased at all.  My girlfriend shot my competition PCC this past weekend and was still completely unable to move the charging handle.
View Quote


There's a part of me that that likes the idea of a build on which people who are not me may have trouble chambering a round...  not to say I don't see the downsides.
Link Posted: 9/8/2023 1:07:30 PM EST
[#38]
My QCB length RDB system arrived this morning, along with a Maxim QCB length buffer tube.  I have a side-charging FMP-9 pistol, and it had a Phase 5 buffer tube and Armaspec Stealth Recoil buffer system on it.

It only took me 10-12 minutes to replace the buffer system with the Maxim products, including chasing off the curious dogs, and the 5 minutes I took to grind the alignment tab off of my BCM buffer endplate -- the CQB buffer tube does not have an alignment groove on the bottom.  Enough of the Maxim QCB buffer tube is threaded such that it is possible to use a standard end plate and castle nut, and I liked the price on that (compared to buying their end plate stand-ins).  I also am proud of my quality state-local products, so keeping that BCM endplate matters to me, even though I have spare plain ones.  I also appreciate that Maxim is in Minnesota--regionally local.

My post-assembly/pre-shooting (may be a bit before I get out to shoot) reactions:
1 - I was surprised by the weight loss, mostly because I wasn't thinking about it.
2 - The shorter buffer tube is nice.  Since I'm not using a brace, this makes it more comfortable to tuck it in tight to the cheek, but I will want to wrap that tube in something... probably paracord.
3 - Chambering a round felt smoother, less bouncy.  That reduced buffer weight makes a difference, even in this.  I think that how the rollers "lock up" makes any bounce upon closing impossible.

-- to be continued, as I'm newbie limited --
Link Posted: 9/8/2023 1:08:11 PM EST
[Last Edit: PreacherOfGadget] [#39]
4 - From early reactions on here, I was expecting it to be MUCH harder to charge.  It isn't that bad.  I do NOT have an exercise routine, and I do NOT lift weights.  I do NOT work a physically demanding job, and I'm middle aged.  I find it slightly stiff starting the charge.  It's also hard to hammer a nail if you just push it.  Hold the gun firmly, and start out with a little more force when you charge it, and I found it no big deal.  Slow pulling the charging handle makes it feel harder, because you spend more time pulling and nothing happening.


I'm a hair confused how many "hard to charge" reactions are out there from this rough-and-tumble crowd.

5 - I'll be curious to see if there's any real difference compared to the carbine buffer length model, once I get that one.  Charging difficulty is the first thing that comes to mind  I can't help but wonder if the spring in the QCB version might not end up having a shorter lifespan, because when that spring compresses, it also twists and folds over a bit as it reaches its full compression.  The thinner section in the center rod gives it the space to do that.  Those extra forces torquing the spring can't be good for it...  but I'm not sure if that would to cause a significant change in their lifespans.
Link Posted: 9/8/2023 5:31:30 PM EST
[Last Edit: SecondAmend] [#40]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By PreacherOfGadget:). ..I also am proud of my quality state-local products, so keeping that BCM endplate matters to me, even though I have spare plain ones.  I also appreciate that Maxim is in Minnesota--regionally local.
.....
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FWIW, the inventor is (or was at the time of invention) a Swiss resident (as can be seen in the U.S. patent linked below).
https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/10619955

MHO, YMMV, etc.
Link Posted: 9/8/2023 10:53:06 PM EST
[Last Edit: PreacherOfGadget] [#41]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By SecondAmend:

FWIW, the inventor is (or was at the time of invention) a Swiss resident (as can be seen in the U.S. patent linked below).
https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/10619955

MHO, YMMV, etc.
View Quote

First, I think it's even more interesting that the patent holder Wyssen Defense AG doesn't seem to offer the same or a similar product for sale on their website.  Or did I miss it?

Second, I think it's interesting that with Maxim Defense being not far off the Mississippi River a few years ago I kayaked and drove past it, and never had a clue.

Third, inventing stuff is awesome, but my preference for local parts is part pride in quality local craftsmanship and part interest in the local economy.  Good businesses -> good jobs.  Good jobs -> better quality of life for the whole area.  I grocery shop down the street from BCM, drive by Vortex on my way out of state to visit my brother, and can drive by Griffin, American Defense Manufacturing, Midwest Industries, Criterion Bbls, Bartlein Bbls, or Krieger Bbls depending on the way I take to visit various friends.  I think that's pretty sweet, but I'm an admitted dork.

ETA:
Fourth, Fig 6 (Force vs Displacement) from that patent with data charted for more springs and spring combinations would be cool--esp with a grid and axis labels.  I'd be curious to see: standard carbine buffer, Armaspec stealth recoil, JP's quiet recoil system, Dead Foot Arms' MCS spring combinations (6 valid combos), Spring Co's springs, and Strike's shortened buffer spring/weight system...  and any other exotic systems.
Link Posted: 9/10/2023 8:48:07 AM EST
[Last Edit: Droppoint] [#42]
Originally Posted By PreacherOfGadget:
4 - From early reactions on here, I was expecting it to be MUCH harder to charge.  It isn't that bad.  I do NOT have an exercise routine, and I do NOT lift weights.  I do NOT work a physically demanding job, and I'm middle aged.  I find it slightly stiff starting the charge.  It's also hard to hammer a nail if you just push it.  Hold the gun firmly, and start out with a little more force when you charge it, and I found it no big deal.  Slow pulling the charging handle makes it feel harder, because you spend more time pulling and nothing happening.


I'm a hair confused how many "hard to charge" reactions are out there from this rough-and-tumble crowd.
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You're assuming everyone else is doing it wrong and you're the only one doing it right.  Based on the reports and the measurements, wouldn't it seem more likely that there's something different about your particular setup?

Either the CQB is machined differently from the carbine system, you're unintentionally preloading the system, or you're not being honest about your physique. The last person I saw who made these types of comments later admitted that they were literally a farrier and blacksmith.  I'm betting that in your case your bolt is pre-loading the Maxim.  Just a few thousandths of movement makes a big difference in the charging force.  I had to unscrew my buffer tube 1 turn to keep the bolt from preloading the RDB when I closed the receivers.  Pre-loaded it was much easier to charge, similar to what you described.

If you want to check for pre-load, remove the Maxim.  Loosen your castle nut and retainer plate without moving the tube.  Mark the position of the buffer tube depth into the receiver with a pencil.  Unscrew the buffer tube 2 turns.  Drop in the maxim, close and lock the receivers with the bolt in place, then screw in the tube gently.  Stop when the RDB gently contacts the bolt. If the tube is back further than it was, the Maxim was being preloaded by the bolt when closing the receivers.  Locking the tube in place at that position will remove the preload.
Link Posted: 9/11/2023 8:07:32 PM EST
[#43]
I shot my AR with the Maxim RDB…

I like how much lighter it is. Recoil was cut by a lot… considering I was running a 11 ounce buffer.

Bad… gas to the face. I run that SBR 100% suppressed. I feel it was worse than the standard blowback.

I will take a look at it when I clean it to see if the buffer was preloaded. I don’t think it was, being I backed out the tube when I first installed it. Charging was heavy, but not unbearable. If it was good, I might put the old weight back in and just cut my losses. Definitely not looking into the Mean Arms setup since I don’t want to invest that much.

But today was also the first time I shot my SBRed PTR 9CT. I will be unloading the Glock magazines and loading up my MP5 magazines. Really was happy with it. The AR and SUB-2000 both had an edge because I could use my duty magazines in the guns… but the PTR’s shooting characteristics are so much better than the other two.
Link Posted: 9/12/2023 10:54:35 PM EST
[#44]
Ordered mine on 6/18, just received a shipping notice, it should be here next week
Link Posted: 9/13/2023 6:05:36 AM EST
[#45]
Did you order straight from Maxim?
Link Posted: 9/13/2023 6:07:52 AM EST
[#46]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Screwball:

Bad  gas to the face. I run that SBR 100% suppressed. I feel it was worse than the standard blowback.
View Quote
+1.  I also think it is louder than my straight blowback as I posted in my previous posts.  It only suppresses well with my belt fed FM-9 upper.  Also straight blowback but since it is belt fed, it cycles slower to pull the belts which gives more time for the gas to go out the right way.
Link Posted: 9/13/2023 8:36:39 PM EST
[#47]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By supercomp:
Ordered mine on 6/18, just received a shipping notice, it should be here next week
View Quote


Ordered first week of July and also got my shipping notice. We’ll see how this goes.
Link Posted: 9/13/2023 10:13:07 PM EST
[#48]
Ordered from Maxim on 6/13. Got tracking info yesterday. I’m definitely going to inspect mine when I get it hoping nothing was rushed and also that it’s the same quality as the early ones with imported components.
Link Posted: 9/13/2023 10:21:16 PM EST
[#49]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Park-Hit-Run:
Ordered from Maxim on 6/13. Got tracking info yesterday. I’m definitely going to inspect mine when I get it hoping nothing was rushed and also that it’s the same quality as the early ones with imported components.
View Quote


Where did you get information concerning imported components? I hadn't heard that before.
Link Posted: 9/14/2023 12:40:01 PM EST
[#50]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Droppoint:
Either the CQB is machined differently from the carbine system, you're unintentionally preloading the system, or [...]  I'm betting that in your case your bolt is pre-loading the Maxim.  Just a few thousandths of movement makes a big difference in the charging force.  I had to unscrew my buffer tube 1 turn to keep the bolt from preloading the RDB when I closed the receivers.  Pre-loaded it was much easier to charge, similar to what you described.
View Quote


Thanks, I appreciate the pre-loading advice (more on that below), and it makes sense.  Recalling force vs displacement chart in the patent, a slight displacement at the beginning of the cycle would lead to a significant reduction in overall amount of work necessary needed to move the bolt, and an even more significant reduction in the portion of work necessary with greater force.  

After test firing a few 147 grain and 135 grain subs suppressed, my biggest observation is the recoil and smoothness of cycling are so much better than the 308 spring/buffer that came factory from FM or the JP captured spring system.  My uppers that can function with this lower are two FM side-charging uppers (one with a kaw/faxon bbl), and that may be why I didn't notice excess gas, but I also haven't had a proper trip to the range yet, just some function testing shots.

tbc (newbie length limit)
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Maxim Defense RDB review (Page 9 of 11)
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