Maxim roller delay AR9 buffer

[smdub]

Oh, this is really interesting! I'm going to have to stare at some pics for a while to figure out how its working. Looking forward to your feedback.

 

[teratos]

Oh, this is really interesting! I'm going to have to stare at some pics for a while to figure out how its working. Looking forward to your feedback.

Of course you will!

 

[alucard0822]

Oh, this is really interesting! I'm going to have to stare at some pics for a while to figure out how its working. Looking forward to your feedback.

This pic kinda sorta shows how the ball bearing rollers and 3 parts work. The ball bearings serve as the roller locks. the inner guiderod acts as the wedge, the angled surface on the outer collar is what gets pushed rearward at a mechanical ratio. Basically the carrier blows back against the front roller housing, that starts to move rearward. The bearings hit a wedgs in the guide rod that pushes them outward, they lock into pockets on the inside of the rear buffer section, accelerating that rearward faster than the front section and carrier are moving. Once the rear section detatches from the front, both move together at 1:1 to complete the inertia driven cycle.

The higher velocity compared to the 1:1 movement of traditional blowback= an increase in force of a far more massive carrier. This delays the blowback operation, resulting in better timing, less gas, and lower mass needed to control cycling. You can see in this pic the front section of the collar has moved about 1/3 as far as the rear section, so being the buffer at least initially is forced to accelerate 3x faster than the BCG and front section, it has resistance like it has 3 X the mass if this was a traditional blowback. I dropped some info about my day job and automotive engineering stuff, Maxim engineering folk are pretty cool, and might have an idea taking shape with a couple I've been in contact with, just have to makes sure I'm not causing issues with intellectual property things at work over it first.

the gif is an HK roller delay setup, with the mechanism in the bolt/carrier. The Maxim buffer works the same way, but red bolt head = front roller housing section, green wedge locking peice= guide rod and blue carrier = rear section / buffer weight

 

[smdub]

Yeah, the pics on their website did it for me. I'm well versed in how the HKs and roller locks in general work.

It took me a while to figure out they had pics of two different length versions. In the CAR version above, the rod and moving 'CAR-0001' part are effectively the trunnion and locking piece ramps of an HK - just inside out. Wonder if different angles will be available for either the rod or moving part to tune. They will have point contact from the bearing since the rod (and presumably the inside of the moving part) are just cones and not scallops to develop a line contact. There might be brinelling over time. Its interesting to note the new (yet to be released) Mean Arms bearing delayed BCG uses proper semicircular tracks for line contact.

The short CQB version is also clever. It looks like the gentle ramps in the rod at full compression are to allow the two moving parts to collapse back together to allow full bcg travel.

 

[alucard0822]

Yeah, the pics on their website did it for me. I'm well versed in how the HKs and roller locks in general work.

It took me a while to figure out they had pics of two different length versions. In the CAR version above, the rod and moving 'CAR-0001' part are effectively the trunnion and locking piece ramps of an HK - just inside out. Wonder if different angles will be available for either the rod or moving part to tune. They will have point contact from the bearing since the rod (and presumably the inside of the moving part) are just cones and not scallops to develop a line contact. There might be brinelling over time. Its interesting to note the new (yet to be released) Mean Arms bearing delayed BCG uses proper semicircular tracks for line contact.

The short CQB version is also clever. It looks like the gentle ramps in the rod at full compression are to allow the two moving parts to collapse back together to allow full bcg travel.

Yes, so far they have no plans on different angles, so hopefully they did a good job tuning it. There will be a ton of point pressure in spots as you said, not sure what steel/hardening and coating they are using, no idea how durable it will be, guess I'll find out. I have been watching the Mean arms delayed BCG for some time, think they have "announced" it 5 years ago, and keep changing it, so no idea how long till they actually sell them. The way the short CQB version works is indeed very cool, but doing some quick measurements and things, there is a way the system could work with the even smaller SCW tube, probably with some tungsten and a short stroke BCG.

 

[Bountied]

This pic kinda sorta shows how the ball bearing rollers and 3 parts work. The ball bearings serve as the roller locks. the inner guiderod acts as the wedge, the angled surface on the outer collar is what gets pushed rearward at a mechanical ratio. Basically the carrier blows back against the front roller housing, that starts to move rearward. The bearings hit a wedgs in the guide rod that pushes them outward, they lock into pockets on the inside of the rear buffer section, accelerating that rearward faster than the front section and carrier are moving. Once the rear section detatches from the front, both move together at 1:1 to complete the inertia driven cycle.

The higher velocity compared to the 1:1 movement of traditional blowback= an increase in force of a far more massive carrier. This delays the blowback operation, resulting in better timing, less gas, and lower mass needed to control cycling. You can see in this pic the front section of the collar has moved about 1/3 as far as the rear section, so being the buffer at least initially is forced to accelerate 3x faster than the BCG and front section, it has resistance like it has 3 X the mass if this was a traditional blowback. I dropped some info about my day job and automotive engineering stuff, Maxim engineering folk are pretty cool, and might have an idea taking shape with a couple I've been in contact with, just have to makes sure I'm not causing issues with intellectual property things at work over it first.

the gif is an HK roller delay setup, with the mechanism in the bolt/carrier. The Maxim buffer works the same way, but red bolt head = front roller housing section, green wedge locking peice= guide rod and blue carrier = rear section / buffer weight

View attachment 418072

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View attachment 418068

The red balls look like they're on the wrong end of the green shaft.

 

[smdub]

I have been watching the Mean arms delayed BCG for some time, think they have "announced" it 5 years ago, and keep changing it, so no idea how long till they actually sell them.

Yeah, I did their $50 'reservation' pre-order earlier this year. Haven't been holding my breath for them to contact me. I've had a couple decent interactions w/ their VP of sales pleading to sell just the BCG and barrel/extension but have been mostly met w/ marketing non-answers.

 

[erwos]

Yeah, I did their $50 'reservation' pre-order earlier this year. Haven't been holding my breath for them to contact me. I've had a couple decent interactions w/ their VP of sales pleading to sell just the BCG and barrel/extension but have been mostly met w/ marketing non-answers.

I talked with them at SHOT back in 2022, and I was really impressed with their solution. It seems very well-engineered. I'm just surprised they've been having so much trouble getting it into production.

I have to admit that I will probably give in and buy the Maxim buffer if it doesn't suck. I tried the TACCOM magnetic one, and it just did not work well enough for my use.

ETA: I'm a terrible person and bought one. YOLO, etc.

 

[alucard0822]

Ordered on the 10th, just shipping today on the 21st so there is that.

 

[alucard0822]

Simple review----buy it, works as advertised.
The reciprocating weight is 4.2oz, and taking the 2.5oz weight of a 9mm BCG cuts over a 1/2lb in mass over the best, smoothest and heaviest blowback setups.

Got it Yesterday, tested it today. Soon as I had it in my hands, I took it apart. It is very well made, up there with the best JP competition parts in fit and finish. Like a JP SCSS it's tough to get in with the buffer retainer in place, so best to remove it, and of course had to remove my BCG weight. Even then, my Geissele trigger's hammer was too tall, so I had to lower the hammer while the skinny section of the buffer body was next to it, and then I could slip the buffer around the side of the hammer, and have enough room to slip it in the buffer tube. Closing the upper, there was just a tiny bit of pressure between the bolt and buffer face. I could see this being a problem if your buffer tube's tolerence is a little short, it could partially unlock the buffer, although it did fit perfectly on my Maxim PDW stock's buffer tube. It is a true delay, as the 5 bearings lock the 2 pieces of the buffer together to the guide rod, and when it starts to move back, the rollers accelerate the rear portion of the buffer rearward at about a 3:1 ratio, but it's very very short, and only delays for a couple MM of bolt travel. Racking the bolt isn't bad, IMO a little better than racking the scheel. Racking it fast, you don't really notice it, but slow, you definitely feel the handle "stick" just for a hair bit of movement, then it charges nice and smooth. Essentially designed like a JP SCSS with a thick nylon bumper and skinny spring on a guide rod, that slips in the BCG tail while cycling. It is very smooth and quiet in use.

Noticed right away when shooting, it works. Recoil is quick, light, and smooth. So far it beat all my blowback setups in lack of dot movement, in recoil, in splits. It has just a quick little jolt as it bottoms out, and had kind of a quick metallic clack sound and feel I noticed when firing suppressed, vs the thump or thud of my cushioned short stroke setups. My softest recoiling blowback setup is a 10oz KVP buffer with floating weights, a AR308 carbine spring, and 2 90lb/in wave springs with a metal disk and bonded silicone bumper spaced just right for the Taccom short stroke BCG. This buffer has always been very soft, and quick, very pleasant to shoot suppressed, little port pop, little gas in the face, and the 2nd stage wave springs are really stiff, works kinda like HK USP's recoil cushion spring. The Maxim is softer, and has just a quick little smack instead of the slow smooth push of my 10oz blowback setup, it also is the new champ in suppressed shooting, less gas, less port pop than ANY blowback system I have tried.

I compared it to my Blitzkreig comp setup, the 6.5oz HD hydraulic dampened buffer uses a 2.5oz weight and AR10 spring. This is a very fast, smooth buffer, the least dot movement and fastest cycle of any Blowback setup. The Blitzkreig is a little harsher recoiling than the 10oz, being about 2 oz lighter, and less floating mass, but is quicker, sharper, and less dot movment. The Maxim felt just like it, but softer and better in every way. The Blitzkreig isn't as good as the 10oz setup for shooting suppressed, being the 6oz buffer body is floating mass, and the hydraulic dampener compresses some during blowback, leaving less mass to control the initial blowback force. The Maxim has less recoil, cycles as fast, and less dot movement than any Blowback setup including this popular comp setup. I also have tried JP SCSS's short stroke 12oz competition setup(requires removing a BCG weight, so about 9.5oz net), that feels similar to the Blitzkreig, but isn't quite as smooth. The Maxim is better and still cheaper than JPs SCSS short stroke comp setup.

Then came some experimentation, I made a short stroke spacer for the Maxim buffer out of nylon and rubber washers. Basically .9OD, .5id, and 1" thick, it slipped around the guide rod/spring and above the stock bumper. Running this in short stroke was fun, it's stupid fast cycling, had just a little more recoil than without the spacer, but maybe a hair less dot movement, and even less gas to the face suppressed. This could work for competition, but really not a huge difference is speed, recoil or dot movement compared to shooting it in long stroke. It was much less of a difference with the RDB in long vs short stroke than blowback makes. Blowback short stroke can have the same or less recoil, but much better cycling speed and less dot movmement, and makes more of a difference.

It feels much like the JP roller delayed JP5, although the JP5 still was probably smoother and less recoil, but I don't have one, and been a couple months since I tried one. It is as light in recoil as a perfectly tuned CMMG RDB, but faster, less complex, and works with standard AR9 BCGs and barrels. The Maxim is simpler, 0 tuning, and no goofy issues with mag height or extractors breaking like the CMMG. Comparing it to the Scheel, it's half the price. Tune a scheel perfectly, and it's close, but still not as good as the Maxim, and Scheel's rollers lock in cutouts, in the buffer tube, it works, but the cutouts could easily foul or jam up, and they are holes in the highest stress area of the tube. It still doesn't knock the MPX off the throne as the lightest recoiling AR-ish 9mm PCC, but the Maxim IS a game changer. It makes Blitzkreig's hydraulic, Scheel's roller delay buffer, and the best heavy buffer setups Obsolete. It's simple, seems reliable, and requires less changes than any other roller delay conversion. It is a must have, and it is fast and smooth enough that there really is no need to short stroke it, although you still can. It is awesome suppressed, flat out a requirement compared to lighter buffers, little gas, less port pop, doesn't need tuning, I ran light and heavy loads, with and without a can, ran 100% reliably.

 

[smdub]

Well, did you like it?

 

[erwos]

Well, now you've got me excited for when mine comes. Sounds like I need to dig the short stroke spacers for my bolt out, too.

ETA: what ammo were you using to test?

 

[alucard0822]

Well, now you've got me excited for when mine comes. Sounds like I need to dig the short stroke spacers for my bolt out, too.

ETA: what ammo were you using to test?

Tried warm 124(1150fps), 124 comp(1060fps) and 147. Gr subs. You can feel different loads, lighter loads have lighter recoil of course, but not a huge difference. The LRBHO locked every time. Didn't try really hot loads, but the light comp loads cycled just fine, so it doesn't seem picky.

 

[erwos]

Tried warm 124(1150fps), 124 comp(1060fps) and 147. Gr subs. You can feel different loads, lighter loads have lighter recoil of course, but not a huge difference. The LRBHO locked every time. Didn't try really hot loads, but the light comp loads cycled just fine, so it doesn't seem picky.

Perfect. Warm-to-hot 124s are my daily drivers for competition and training, so if that's working for you, that's about what I'm after. Hopefully my buffer will ship soon.

 

[outrider58]

I ordered one. It will start out in my Colt pattern SBR(direct blowback), then decide whether it will be worth replacing my Scheels system in my HD gun. It won't work in my Banshee folder, which is fine.

 

[alucard0822]

My 80lb 11 year old shooting it. Less recoil than a 5.56 AR, less gas in the face, nice and quiet, even with this K can. It's pretty much the ultimate setup for steel plates. All that remains to be seen is how it holds up, but after about 300 rounds there is 0 noticeable wear in the contact surfaces. It did come with a little grease in the ball housing. Cleaning it, and replacing the grease is all I plan on doing. Be careful though, if you pull the rear section of the buffer back, the ball bearings can fall out, there is nothing keeping them inside the front cage peice, in operation they are contained within the buffer, unlike the earlier pic shows.

 

[lazarus]

I don't see what all the fuss is about.

Every 9mm pistol in my modest collection is direct blowback and I would use any one of them to defend my life.

If you select the correct buffer and spring combination, any AR-9 can be made just as reliable and safe too shoot.

I had some issues with my build initially, but after changing the buffer and spring, it runs perfectly even when fast firing.

All you own are hi points? Only a handful of direct blow back 9mm models have been made. Almost all 9mm (and more powerful) pistols have been locked breech or delayed blowback. For example, browning action.

And direct blowback pistols have substantially more recoil than locked breech pistols for a similar caliber.

Sure direct blowback 9mm PCC work just fine. But they do have more recoil, are heavier, are louder when suppressed, and run dirtier when suppressed. Which is why so many people are interested in delayed blowback.

 

[alucard0822]

All you own are hi points? Only a handful of direct blow back 9mm models have been made. Almost all 9mm (and more powerful) pistols have been locked breech or delayed blowback. For example, browning action.

And direct blowback pistols have substantially more recoil than locked breech pistols for a similar caliber.

Sure direct blowback 9mm PCC work just fine. But they do have more recoil, are heavier, are louder when suppressed, and run dirtier when suppressed. Which is why so many people are interested in delayed blowback.

True, not sure how all of his pistols are blowback, unless talking about braced AR9 pistols maybe? Good points on the reason delayed blowback conversions are so hot right now.


The main advantage of delayed blowback is less reciprocating weight to keep a comfortable, reliable bolt speed. The Maxim is 4.2oz of buffer mass+12.5ox BCG = 16.7oz. To keep a similar bolt speed/ejection pattern it takes a 15oz BCG and around a 10oz buffer, for 25oz. Less weight = less dot movement, and less force impacting your shoulder, then slamming the rifle back forward. Being the initial blowback is delayed by accelerating the buffer rearward around 3X the BCG velocity from the mechanism, it acts like a much heavier buffer than you are actually using. This keeps it in battery longer, less gas leakage, especially suppressed, less dirt in the action.

Soon as the seal between the case and chamber is broken, and the blowback force is over, the buffer just gets pushed at a 1:1 ratio, and the lighter weight, and lighter spring moving with the carrier has less inertia to complete the cycle. It can potentially be as reliable or more so than blowback, less dirt in the action, it is more consistent with a wider range of ammo, being the hotter the load, the faster it tries to accelerate the buffer weight, and the more resistance there is, blowback can be harsh with heavier loads, and jam from short stroking with lighter loads. Even so, this has a heavy carrier with a mild delay compared to something like the MP5 or JP5, so the effect is less pronounced, and there is still a lot of mass to control bolt velocity, but it doesn't need a fluted chamber, and so far is very reliable.

 

[erwos]

Even so, this has a heavy carrier with a mild delay compared to something like the MP5 or JP5, so the effect is less pronounced, and there is still a lot of mass to control bolt velocity, but it doesn't need a fluted chamber, and so far is very reliable.

I wonder if Maxim Defense would ever consider coming out with a lightened 9mm bolt assembly with a custom roller setup to really try to eke out performance from this system. I don't think getting recoil down to JP5 or SP5 levels is plausible, but I think they could probably get really close.

That said, I don't think my MPX is gonna get dethroned ever. Needs cleaning a little too much, but it shoots real good.

 

[alucard0822]

I wonder if Maxim Defense would ever consider coming out with a lightened 9mm bolt assembly with a custom roller setup to really try to eke out performance from this system. I don't think getting recoil down to JP5 or SP5 levels is plausible, but I think they could probably get really close.

That said, I don't think my MPX is gonna get dethroned ever. Needs cleaning a little too much, but it shoots real good.

Yea, the MPX is awesome, bets recoil feel out of any PCC. They should be the top choice for competition, but so many jam up, or get dirty and choke in matches, they aren't as popular as they could be.

The drop-in buffer is perfect for what it is, simple, and a dramatic improvement over blowback. I would love to see a more tuneable version or kit, different wedge angles, different springs, different weights, and a short stroke spacer. Even so, not sure what the limiting factor is, there is a lot of force on the buffer tube, and you still need to overcome the delay system to rack it. That might be why it doesn't reduce weight/recoil as much as a delay system that locks at the bolt/receiver. The best would be a roller delay BCG like the Mean arms design, where the charging handle pulls on the carrier, so no added force, and the bolt locks in the upper to be the most efficient, even better if it doesn't need a buffer tube at all, and is contained entirely in the upper.