Low Mass Operating Systems Setup

[Ape_Factory]

My current favorite is probably an RCA TI carrier paired with an Unrivaled Technologies magnetic captured buffer. It's different from the SCS in that it's very light but uses magnets to hold the BCG in battery rather than buffer weights to eliminate any potential for bolt bounce.

Dude. I've been an RCA Ti fan for a while and have a few in various rifles. I recently ordered the Unrivaled dead blow buffer (comp version) after reading your post/watching video and threw it into a spare parts build in 300 blackout. I usually curse you guys for spending my money but I tell you what...this thing actually works really well in the recoil mitigation department. The difference between this build and the Sig LT in 300 blackout is STARK, subs or supers. Makes the Sig feel like a 300 Win Mag in comparison, even with subs.

I only built this thing to shoot all the supers I have loaded up since they're bonded bullets and I don't feel comfortable shooting them in the Sig (fast barrel twist rate). But holy hell, with subs, it really is like a .22LR. I have the JP SCS and I may have to swap them back and forth to experiment but I think it'll crush the JP. Money well spent, IMO.

I'd already tuned the gun with a standard spring and Odin adjustable buffer. Threw in the Unrivaled and it worked like a charm right off the bat.

I'll likely be purchasing a few more and kinda wondering if the duty version will work in my POF Revolution DI and bring it that much closer to a hot 5.56 load in felt recoil.

 

[TonyTheTiger]

Dude. I've been an RCA Ti fan for a while and have a few in various rifles. I recently ordered the Unrivaled dead blow buffer (comp version) after reading your post/watching video and threw it into a spare parts build in 300 blackout. I usually curse you guys for spending my money but I tell you what...this thing actually works really well in the recoil mitigation department. The difference between this build and the Sig LT in 300 blackout is STARK, subs or supers. Makes the Sig feel like a 300 Win Mag in comparison, even with subs.

I only built this thing to shoot all the supers I have loaded up since they're bonded bullets and I don't feel comfortable shooting them in the Sig (fast barrel twist rate). But holy hell, with subs, it really is like a .22LR. I have the JP SCS and I may have to swap them back and forth to experiment but I think it'll crush the JP. Money well spent, IMO.

I'd already tuned the gun with a standard spring and Odin adjustable buffer. Threw in the Unrivaled and it worked like a charm right off the bat.

I'll likely be purchasing a few more and kinda wondering if the duty version will work in my POF Revolution DI and bring it that much closer to a hot 5.56 load in felt recoil.

 

[Yondering]

Kind of on topic, but when tuning your AR for suppressor use, any go-to tips that you guys use?

I started out with a standard AR15 type rifle with a non adjustable gas block and two different flow through suppressors. Which worked just fine.
Then I started tinkering with regular suppressors and quickly found out that an AGB was very much needed. The amount of backpressure that some suppressors create was surprising to me. Im thinking about getting a buffer with adjustable weight system to really fine-tune. Is it worth it or should I be looking at other stuff?

You'll do better adjusting gas to delay that unlocking. And if you're already tuning the gas, IMO you don't need to adjust buffers as well.
Lots of different opinions on this of course; this one is mine and works for the 20 or so ARs I'm currently using suppressed.

 

[VargmatII]

You'll do better adjusting gas to delay that unlocking. And if you're already tuning the gas, IMO you don't need to adjust buffers as well.
Lots of different opinions on this of course; this one is mine and works for the 20 or so ARs I'm currently using suppressed.

Yeah, it seems to work pretty well. The rifle is really soft shooting now, but I was thinking that I might be able to tune it even softer? But maybe I should be satisfied where it is?!

The suppressor I currently use creates a lot of backpreassure, I run the AGB 1/6 from fully closed and the gun still cycles and locks up just fine. But with almost no felt recoil.

 

[Cascade Hemi]

Dude. I've been an RCA Ti fan for a while and have a few in various rifles. I recently ordered the Unrivaled dead blow buffer (comp version) after reading your post/watching video and threw it into a spare parts build in 300 blackout. I usually curse you guys for spending my money but I tell you what...this thing actually works really well in the recoil mitigation department. The difference between this build and the Sig LT in 300 blackout is STARK, subs or supers. Makes the Sig feel like a 300 Win Mag in comparison, even with subs.

I only built this thing to shoot all the supers I have loaded up since they're bonded bullets and I don't feel comfortable shooting them in the Sig (fast barrel twist rate). But holy hell, with subs, it really is like a .22LR. I have the JP SCS and I may have to swap them back and forth to experiment but I think it'll crush the JP. Money well spent, IMO.

I'd already tuned the gun with a standard spring and Odin adjustable buffer. Threw in the Unrivaled and it worked like a charm right off the bat.

I'll likely be purchasing a few more and kinda wondering if the duty version will work in my POF Revolution DI and bring it that much closer to a hot 5.56 load in felt recoil.

Do you know how much the buffer weights weigh? They list the weight for the M4 but not the ultra lightweight model.

 

[Ape_Factory]

Do you know how much the buffer weights weigh? They list the weight for the M4 but not the ultra lightweight model.

I shall weigh it for you sir! BRB...

Ok looking at 6.6oz on my crappy scale which going by years of use, reads about .2-4oz high.

 

[srt-4_uk]

I shall weigh it for you sir! BRB...

Ok looking at 6.6oz on my crappy scale which going by years of use, reads about .2-4oz high.

The weight of the part that moves is what matters.

 

[Ape_Factory]

The weight of the part that moves is what matters.

I get that but I'm not disassembling it to weigh the individual components. With that said, my old buffer weight was about 2.3oz. and there was no change in function switching to the Unrivaled comp.

 

[Cascade Hemi]

I shall weigh it for you sir! BRB...

Ok looking at 6.6oz on my crappy scale which going by years of use, reads about .2-4oz high.

I hadn't considered overall weight, I was really interested in just the reciprocating mass. However that overall weight is pretty heavy. Here's a 3.0oz buffer and spring.

 

[Ape_Factory]

I'd take it apart but if you've seen one in person, there's a good chance something will go flying, LOL. Not willing to take that risk right now.

The rod down the middle obviously doesn't reciprocate and I'd say it makes up a good bit of the overall weight, likely 50%.

 

[Cascade Hemi]

I'd take it apart but if you've seen one in person, there's a good chance something will go flying, LOL. Not willing to take that risk right now.

The rod down the middle obviously doesn't reciprocate and I'd say it makes up a good bit of the overall weight, likely 50%.

No problem. It looks a little complex and I wasn't intending for you to take it apart. I appreciate the info.

 

[Bluedog82]

I’m excited to run my RCA Ti BCG with the competition buffer in my 6 arc. Hopefully I can get out and shoot it soon…perfect weather for tuning the gas block.

 

[Bluedog82]

The Unrivaled Competition Buffer is 2oz reciprocating weight per their Instagram.

 

[Yondering]

Yeah, it seems to work pretty well. The rifle is really soft shooting now, but I was thinking that I might be able to tune it even softer? But maybe I should be satisfied where it is?!

The suppressor I currently use creates a lot of backpreassure, I run the AGB 1/6 from fully closed and the gun still cycles and locks up just fine. But with almost no felt recoil.

No, you won't get a softer recoil by going to a heavier buffer, if the rifle is already tuned correctly at the gas block. You will get a slower recoil impulse that actually moves the rifle more, not less. Very light reciprocating mass with proper gas tuning provides the least recoil IME.

(That doesn't take into account something like that Unrivaled magnetic buffer, where the benefit in recoil reduction is due to other factors besides just reduced mass - I'm speaking about conventional style buffer systems which I think is what you were asking?)

I'm not sure if it was your intent, but the comment about how much adjustment you have on your gas block is really only relevant to your particular rifle; it doesn't mean anything for the rest of us. You should be adjusting it for proper tuning, and don't worry about how far closed or open it is - doesn't matter.

 

[VargmatII]

No, you won't get a softer recoil by going to a heavier buffer, if the rifle is already tuned correctly at the gas block. You will get a slower recoil impulse that actually moves the rifle more, not less. Very light reciprocating mass with proper gas tuning provides the least recoil IME.

(That doesn't take into account something like that Unrivaled magnetic buffer, where the benefit in recoil reduction is due to other factors besides just reduced mass - I'm speaking about conventional style buffer systems which I think is what you were asking?)

I'm not sure if it was your intent, but the comment about how much adjustment you have on your gas block is really only relevant to your particular rifle; it doesn't mean anything for the rest of us. You should be adjusting it for proper tuning, and don't worry about how far closed or open it is - doesn't matter.

I was thinking somewhere along the line that the restriced gas from the AGB along with a heavier buffer would slow things down an reduce the overall pressure for the system of the rifle, which in turn would give lower felt recoil. But I also understand that less weight moving back and forth should be the best option.

Yeah, the comment about the needed amount of gas in my rifle is just that, a comment. There are probably way to many variations of barrels, gasblocks and gastube lenghts for my comment to mean anything for anyone else than me.
All im really saying is that I am surprised by the amount of back preassure that a suppressor can create. Way more than I could imagine.

 

[Cascade Hemi]

Heavier buffers require more energy to cycle. The energy has to go somewhere and it turns into felt recoil. There are tradeoffs though, low Mass has a narrower operating window for ammunition and environmental conditions.

 

[Milirad]

I've got at least 8 rifles set up with low mass systems, so you can probably guess that I think they are worth it.
However, as nice as the quality of the JP parts are, there is no performance advantage over less expensive BCG's, like those from RCA, Toolcraft, Youngs, Odin, etc. Even the AIM Surplus house brand BCG's are serviceable.

The SCS is nice and makes things feel smoother while charging but there is no performance gain over a standard buffer at a weight that you like.
An AGB is a must, lightweight parts without gas to match will be harsher than it needs to be.

The step up to ultra low mass is noticeable but not huge, and aluminum carriers are short lifespan parts. Titanium is forever, but a lower quality TI carrier with anything less than a glass polished surface can hog out your upper receiver.

Make sure to play with spring rates as well as different buffer weights while you're tuning the setup.

I've been doing low mass stuff extensively for the last seven years, in rain, sand, mud, snow, ice, temps from 0-100, and anything that has made my systems fail is also making the next guy with a mil-spec systems rifle fail. Nothing is malfunction proof, but with at least a tiny bit of maintenance and lube a low mass system isn't far off in reliability from anything else out there.

Is there a nice, reliable LMOS with forward assist, or are they all lacking on this?

 

[TonyTheTiger]

Is there a nice, reliable LMOS with forward assist, or are they all lacking on this?

Off the top of my head, RCA, Odin, Faxon, Brownells/Toolcraft all have FA notches. I'm sure there are more also.

 

[Milirad]

Off the top of my head, RCA, Odin, Faxon, Brownells/Toolcraft all have FA notches. I'm sure there are more also.

Thanks. Doing a fighting rifle build and had decided not to go JP LMOS due to no forward assist, but now I can check out these others.

 

[Yondering]

low Mass has a narrower operating window for ammunition and environmental conditions.

That's the conventional wisdom for sure, and I believed it for quite a while. My own experience hasn't proven that true though, and I'm one of those guys who rarely cleans my ARs. Out of about 20-ish rifles at last count, I think 7 or 8 of them have low mass systems of some sort, and once they were tuned they all pretty much run flawlessly. That includes my 308 as well, where I took the 308 bolt carrier down to the same mass as a standard M16 carrier - it's still flawless too, even in the freezing cold.

Even my 3.8 lb ultralight 5.56 has been flawless, and that one is using an empty buffer and lightened spring, along with a very light carrier.

I think most of the difference is tuning (LMOS without good tuning can sometimes outrun a dirty mag and cause feed issues, or extraction failures), and the other part is using oil instead of grease for lube. A decent gun oil softens the fouling and lets it be pushed away, grease just builds it up into a thick cake IME. I love the slick feel of a clean and freshly greased AR action, but don't like the results after a lot of shooting, especially with muzzle brakes and dust.

With low mass carriers becoming more popular now, I'd like to say that a lot of people will realize that conventional wisdom doesn't hold true - but sadly I don't think most people will see that, because the general shooting public is frankly pretty dumb and most of them will just drop these things in a rifle without tuning the gas appropriately. I've even heard of a few people using low mass carriers combined with extra heavy buffers to make them cycle right. (Insert facepalm emoji here)

 

[Yondering]

My current favorite is probably an RCA TI carrier paired with an Unrivaled Technologies magnetic captured buffer. It's different from the SCS in that it's very light but uses magnets to hold the BCG in battery rather than buffer weights to eliminate any potential for bolt bounce.

Everyone seems to be sold out of the comp version of this buffer so I can't try it yet, but curious on your take - is it worth the ~$170 compared to the other decent captured buffer systems on the market? From what I can tell based on pics and description on their site, the primary difference seems to be the magnets, which they say is for bolt bounce. (And no mistake, bolt bounce is real and worth taming down.) Does the magnetic system also make any noticeable difference in unlocking? Can you feel it as you start to pul the charge handle back? I'm wondering if the magnet system in that buffer does anything to delay unlocking, which in theory would allow use of both lighter spring and buffer compared to a conventional system.

It sounds like it might provide a similar effect to a flat bottom firing pin stop in a 1911, where additional force is required in that first little bit of travel to unlock the action, but then not continued throughout the stroke or put back into the action as the bolt/slide rides home.


As an aside, there's been some comments above about using different buffer spring weights, and that can be a significant part of tuning a low mass system (as you know). A method I like to use, rather than buying a bunch of different spring weights, is to start with a handful of standard carbine springs and collapse a few coils. (Use a propane torch to heat coils on one end of the spring to a dull red, then press the spring against a hard flat surface to collapse the coils. Let them air cool, don't water quench.) If you start with a bunch of the same spring, it's easy to count the number of collapsed coils to have an idea how much softer a particular spring is - one with 4 collapsed coils is softer than one with 2 collapsed coils, etc. I mostly use 2-3 coils collapsed, and rarely go lighter than 4. This is a better method than cutting coils off, BTW, because it leaves that end of the spring very stable, and the fully compressed spring length remains the same as stock. Just another easy method of trying lighter springs.

For example, left to right: stock, 2 coil, 4 coil

 

[Bluedog82]

Everyone seems to be sold out of the comp version of this buffer so I can't try it yet, but curious on your take - is it worth the ~$170 compared to the other decent captured buffer systems on the market? From what I can tell based on pics and description on their site, the primary difference seems to be the magnets, which they say is for bolt bounce. (And no mistake, bolt bounce is real and worth taming down.) Does the magnetic system also make any noticeable difference in unlocking? Can you feel it as you start to pul the charge handle back? I'm wondering if the magnet system in that buffer does anything to delay unlocking, which in theory would allow use of both lighter spring and buffer compared to a conventional system.

It sounds like it might provide a similar effect to a flat bottom firing pin stop in a 1911, where additional force is required in that first little bit of travel to unlock the action, but then not continued throughout the stroke or put back into the action as the bolt/slide rides home.


As an aside, there's been some comments above about using different buffer spring weights, and that can be a significant part of tuning a low mass system (as you know). A method I like to use, rather than buying a bunch of different spring weights, is to start with a handful of standard carbine springs and collapse a few coils. (Use a propane torch to heat coils on one end of the spring to a dull red, then press the spring against a hard flat surface to collapse the coils. Let them air cool, don't water quench.) If you start with a bunch of the same spring, it's easy to count the number of collapsed coils to have an idea how much softer a particular spring is - one with 4 collapsed coils is softer than one with 2 collapsed coils, etc. I mostly use 2-3 coils collapsed, and rarely go lighter than 4. This is a better method than cutting coils off, BTW, because it leaves that end of the spring very stable, and the fully compressed spring length remains the same as stock. Just another easy method of trying lighter springs.

For example, left to right: stock, 2 coil, 4 coil

Yeah, you can definitely feel the magnets in the last inch or so when pulling back the charging handle.

 

[TonyTheTiger]

Everyone seems to be sold out of the comp version of this buffer so I can't try it yet, but curious on your take - is it worth the ~$170 compared to the other decent captured buffer systems on the market? From what I can tell based on pics and description on their site, the primary difference seems to be the magnets, which they say is for bolt bounce. (And no mistake, bolt bounce is real and worth taming down.) Does the magnetic system also make any noticeable difference in unlocking? Can you feel it as you start to pul the charge handle back? I'm wondering if the magnet system in that buffer does anything to delay unlocking, which in theory would allow use of both lighter spring and buffer compared to a conventional system.

The magnets do nothing for lock delay that I can tell. They add the dead blow effect but they in no way stick to anything on the gun that would slow down unlocking.
I really can't say if they're better than other captured spring systems, the only other one I have much experience with is the JP, which is just a captured spring with changeable parts, no novel locking/unlocking component. It's smooth no doubt, but functionally it does nothing a standard buffer/spring isn't doing.

Cool tip on the collapsed coils too, I never would've thought of that.

 

[stefan73]

I’m thinking of swapping to a low mass setup in my competition rifle. This is my run & gun setup so it needs to be reliable even if it gets wet/dirty and it needs to provide a notable difference in recoil mitigation for fast follow up shots.

2 questions for you guys who have experience in these:

1. Is it worth the cost? ($500ish)

2. Is there anything else you’d recommend?: JP Low Mass steel BCG, JP Silent Capture System, JP adjustable gas block.

I am running a Rubber City Armory skeletonized titanium bolt carrier group in one rifle and in another I am running a Brownelss titanium bolt carrier group. The Rubber City Armory skeletonized bolt carrier group with standard springs on the JP captive buffer doesn't have enough mass to strip the rounds out of the mag so I had to up the spring weight on the JP captive buffer springs (sorry I wrote that wonky, but you will need to up the spring weight to provide enough force to strip the rounds out of the magazines, I am using magpul mags with good success). I am using a Superlative adjustable gas block to help mitigate beating the crap out of everything and then I tied it together with a nice trigger and muzzle brake that shakes Xi out of bed every time I fire my rifle from America (and gives the RO's a mild case of TBI). I have used this rifle to about 5 or 6 local 3 gun events, probably 4 or 5 two gun events and two run and gun biathlon type events with Third Coast Tactical.

To me, it is worth the cost. I like the recoil impulse better.
You will need to pick your ammo and tune your rifle to the ammunition you are using if you are running factory ammunition.

 

[stefan73]

Another update for anyone who’s trying to set up something similar.

To recap - before my last run n gun I swapped to an RCA low mass carrier and the JP SCS with the lightest spring. It made a noticeable difference and stayed reliable throughout the run. I finished as top shooter with about 60 people in my division.

I recently bought an APA Answer brake. Got to hit the range today and get it dialed in. It made a ridiculous difference.

After dialing in the right combination of ports the sights basically do not move now. I was able to do hammered pairs on a 10” plate at 300 yards.

I’ve got another comp in a few weeks so looking forward to seeing how it works out in the cold this time. AND I’m just gonna apologize to the RO’s ahead of time because it will rattle your teeth out, lol.

Thanks for all the advice!

I might have to look into that APA brake.

 

[357Max]

2024 Shot show brings you this gem.

The opposite of low mass operating system could be yours for only $6599 & it mostly guaranteed to shoot better than 2moa.

They ship on April Fools, how apropos

 

[TonyTheTiger]

2024 Shot show brings you this gem.

The opposite of low mass operating system could be yours for only $6599 & it mostly guaranteed to shoot better than 2moa.

They ship on April Fools, how apropos

Wasn't this debuted last year? If not there was something similarly silly in 2023.

 

[357Max]

Wasn't this debuted last year? If not there was something similarly silly in 2023.

Don't know if it was there last year.

Off topic from LW systems. I've never really been a fan of Foxtrot Mike's stuff, but damn I like where their headed.
A lot of good new innovations from them shown at shot. I'll be keeping an eye on them to see if they offer builder friendly components with these changes.

 

[TonyTheTiger]

Don't know if it was there last year.

Off topic from LW systems. I've never really been a fan of Foxtrot Mike's stuff, but damn I like where their headed.
A lot of good new innovations from them shown at shot. I'll be keeping an eye on them to see if they offer builder friendly components with these changes.

Will watch tomorrow. Cliff notes?

 

[357Max]

Will watch tomorrow. Cliff notes?

1 pc barrels with keymo brake 45 degree GB & oversize extension. Oversize Super Bolt sim to the ones Constructor made. Flat on top of extension instead of pin & thermal fit receivers. Interesting gas tube attachment. Monolith upper receiver shown also.

Not explained, but possible with this set up would be the ability to always have the gas port hit in a groove.

 

[Ape_Factory]

Got the Unrivaled "duty" buffer in but haven't had a chance to compare at the range just yet. I have the JP SCS in the rifle now and will switch it out for the Unrivaled. It'll be at least a month before I have a chance to shoot it and I'll try to swap them back and forth before reporting back.

With the comp system, I do feel the magnets release the weight at the very end of the BCG's travel backwards. It's not a bad thing but the impulse is definitely different and softer on a precision upper in 5.56. I don't notice the impulse as much when I switch the lower over to a 300 blackout SBR running supers but it does reduce felt recoil.

Just fondling both, there's a lot more slop between the weights on the JP and overall the Unrivaled just feels tighter with the magnets holding things in place.

I do have a Smoke Composites buffer tube on the rifle it'll be going into (POF P415 SBR) and the Unrivaled is a very precise fit. While there's no weird resistance felt when pulling the charging handle back, I lubed the body so it's slick.

Here's a weight comparison between the JP and the Unrivaled duty.





And gratuitous gun photo just because.

 

[Jnull]

I’m excited to run my RCA Ti BCG with the competition buffer in my 6 arc. Hopefully I can get out and shoot it soon…perfect weather for tuning the gas block.

Have you gotten a chance to run this setup yet?

I’m putting together a 6 ARC using an 18” proof rifle +1, flow 762 full time, JP bolt I’m planning on changing the gas rings out on, rifle speed gas block, Armaspec stealth recoil spring kit with C H and H2 weights. I have to order a carrier still and I’m considering low mass. This will be a coyote rifle using factory hornady 80 grain VT. Anyone else running a similar setup in 6 ARC?

 

[Bluedog82]

Have you gotten a chance to run this setup yet?

I’m putting together a 6 ARC using an 18” proof rifle +1, flow 762 full time, JP bolt I’m planning on changing the gas rings out on, rifle speed gas block, Armaspec stealth recoil spring kit with C H and H2 weights. I have to order a carrier still and I’m considering low mass. This will be a coyote rifle using factory hornady 80 grain VT. Anyone else running a similar setup in 6 ARC?

Only a bit before the barrel (whole upper included) had to go back to Rainier for some issues, unfortunately. Seemed sweet though!