Gas vs mass tuning?

KOPFJÄGER13 · Wednesday at 3:20 PM

I was thinking a well tuned AR15 should cycle 100% with the minimum amount of gas needed (from adjustable gas block) right? So shouldn’t you always pick a low weight buffer and then turn down the gas on gas block? How’s that effect the cycling compared to a heavier buffer with more gas? How’s recoil impulse change or does it? The only difference I see is with lighter buffer and less gas it would run cleaner…… are the principles the same when suppressed?

Light buffer + lower gas = ?
Heavier buffer + more gas = ?

Are they equal??

Edsel · Wednesday at 3:44 PM

Some people do attempt going light on everything (coupled with really good muzzle brakes) and when things go well, these rifles are a joy to shoot - but are much less forgiving of charge weights, fouling, etc.

However, you do need the brute force of that mass “to overcome adversity.”

Overgassed, overmassed - for a teeny .223 Remington cartridge - you get the picture.

KOPFJÄGER13 · Wednesday at 3:49 PM

Edsel said:
Some people do attempt going light on everything (coupled with really good muzzle brakes) and when things go well, these rifles are a joy to shoot - but are much less forgiving of charge weights, fouling, etc.

However, you do need the brute force of that mass “to overcome adversity.”

Overgassed, overmassed - for a teeny .223 Remington cartridge - you get the picture.

I’m not sure what you’re saying…. Elaborate?

hafejd30 · Wednesday at 3:50 PM

I had a AR setup with a lightweight bolt/buffer combo and tuned gas on mid length gas system. Was unbelievably smooth compared to something like a factory carbine setup. Like shooting a 22 mag.

The downside to running that light is you don’t have the spring pressure and weight of the system pushing the next round up. So when things get dirty or cold/wet you can run into issues.

I wouldn’t have set that rifle up for duty or defense use. But for range it was fun

KOPFJÄGER13 · Wednesday at 3:55 PM

hafejd30 said:
I had a AR setup with a lightweight bolt/buffer combo and tuned gas on mid length gas system. Was unbelievably smooth compared to something like a factory carbine setup. Like shooting a 22 mag.

The downside to running that light is you don’t have the spring pressure and weight of the system pushing the next round up. So when things get dirty or cold/wet you can run into issues.

I wouldn’t have set that rifle up for duty or defense use. But for range it was fun

So what would you say, for suppressed use on a dedicated range gun

hafejd30 · Wednesday at 4:09 PM

I’m no expert on AR’s by any means. Just a few I’ve played with and used for work

My personal ones are a 11.5” centurion barrel running a saker ASR 556 with I believe a non adjustable Geissele gas block. I tuned it with a bootleg carrier. The carrier in full suppressed setting ejects at 3 O’clock with the can on. H2 buffer

My other is a 18” white oak barrel, H2 buffer, adjustable block, rifle length gas. Shoots amazing and is gassed just enough to cycle the gun. I would definitely open the gas block up on this if I used for any type of defense scenario.

Both rifles above have the M16 full auto BCG for the extra weight.

My truck rifle is a factory Springfield saint. Mid length gas, I think h2 buffer (whatever they come stock with) and a AR15 BCG. It cycles very smooth as well. But nothing close to the tuned rifle length gun.

For range and if you keep up on maintenance of the rifle either would be fine. The extra mass will help cycle when the suppressor gums up the action. But if you keep the gun clean and oiled a lightweight setup can be fun for the range. It’s definitely a smoother gun to shoot

You’ll get others to chime in with much more experience than me. Personally I feel a lightweight setup for range/gun games is great. For something I may need for defense I prefer the heavier gassed/heavier mass system

KOPFJÄGER13 · Wednesday at 4:18 PM

hafejd30 said:
I’m no expert on AR’s by any means. Just a few I’ve played with and used for work

My personal ones are a 11.5” centurion barrel running a saker ASR 556 with I believe a non adjustable Geissele gas block. I tuned it with a bootleg carrier. The carrier in full suppressed setting ejects at 3 O’clock with the can on. H2 buffer

My other is a 18” white oak barrel, H2 buffer, adjustable block, rifle length gas. Shoots amazing and is gassed just enough to cycle the gun. I would definitely open the gas block up on this if I used for any type of defense scenario.

Both rifles above have the M16 full auto BCG for the extra weight.

My truck rifle is a factory Springfield saint. Mid length gas, I think h2 buffer (whatever they come stock with) and a AR15 BCG. It cycles very smooth as well. But nothing close to the tuned rifle length gun.

For range and if you keep up on maintenance of the rifle either would be fine. The extra mass will help cycle when the suppressor gums up the action. But if you keep the gun clean and oiled a lightweight setup can be fun for the range. It’s definitely a smoother gun to shoot

You’ll get others to chime in with much more experience than me. Personally I feel a lightweight setup for range/gun games is great. For something I may need for defense I prefer the heavier gassed/heavier mass system

I have an IWI SPR… 18” with an adjustable gas block, geissele super 42 spring & buffer (h2)…. It’s ejecting at 4-4:30…. I will be putting surefire RC2 can on it once it comes in……. Guess I’m wondering if I should put an H1 in to get the ejection at 3…..then tune gas block when I get suppressor on

hafejd30 · Wednesday at 4:31 PM

KOPFJÄGER13 said:
I have an IWI SPR… 18” with an adjustable gas block, geissele super 42 spring & buffer (h2)…. It’s ejecting at 4-4:30…. I will be putting surefire RC2 can on it once it comes in……. Guess I’m wondering if I should put an H1 in to get the ejection at 3…..then tune gas block when I get suppressor on

Personally I run H2 buffers when I put my saker on a rifle. It tamed my 11.5” down where it needed to be and the bootleg carrier took care of the rest

I’m running stock springs though and full auto carriers across the board when suppressed

I ran a H1 on my rifle length White Oak SPR barrel. Has a SLR block on it. It ran fine with the H1. I swapped to an H2 I had laying around though. To be honest I don’t notice the difference between the H1 vs H2. But again I’m no expert. The gun cycles with both at same setting

KOPFJÄGER13 · Wednesday at 4:35 PM

hafejd30 said:
Personally I run H2 buffers when I put my saker on a rifle. It tamed my 11.5” down where it needed to be and the bootleg carrier took care of the rest

I’m running stock springs though and full auto carriers across the board when suppressed

I ran a H1 on my rifle length White Oak SPR barrel. Has a SLR block on it. It ran fine with the H1. I swapped to an H2 I had laying around though. To be honest I don’t notice the difference between the H1 vs H2. But again I’m no expert. The gun cycles with both at same setting

How’d your ejection change from the h1 to the h2?

hafejd30 · Wednesday at 4:55 PM

KOPFJÄGER13 said:
How’d your ejection change from the h1 to the h2?

Can’t really say. I pulled the bootleg from that gun because it benefited the 11.5” more to have that carrier. So I swapped a toolcraft full auto carrier into it along with the H2. Never touched the gas and sighted it back in.

Shot under 1/2” for 3 shots and all the brass landed about 3 o’clock just to my right. It cycled the rifle and locked back on empty but it’s right on edge. Super smooth with the H2 but I’ll likely open the block up when I play with it more this summer

But I ran it with the H1 and bootleg for a few years and it was excellent. I could tune the block or the carrier

Give it a shot with both. Then tune the block. The back pressure of the can will play a factor in how it tunes

KOPFJÄGER13 · Wednesday at 5:05 PM

hafejd30 said:
Can’t really say. I pulled the bootleg from that gun because it benefited the 11.5” more to have that carrier. So I swapped a toolcraft full auto carrier into it along with the H2. Never touched the gas and sighted it back in.

Shot under 1/2” for 3 shots and all the brass landed about 3 o’clock just to my right. It cycled the rifle and locked back on empty but it’s right on edge. Super smooth with the H2 but I’ll likely open the block up when I play with it more this summer

But I ran it with the H1 and bootleg for a few years and it was excellent. I could tune the block or the carrier

Give it a shot with both. Then tune the block. The back pressure of the can will play a factor in how it tunes

Cool…. I was thinking I’d go to an h1 so I could turn gas down a bit and possibly it would run a bit cleaner….. was also considering premature wear….. thoughts?

hafejd30 · Wednesday at 5:28 PM

KOPFJÄGER13 said:
Cool…. I was thinking I’d go to an h1 so I could turn gas down a bit and possibly it would run a bit cleaner….. was also considering premature wear….. thoughts?

Cans are dirty either way. Just keep up on basic maintenance. I personally don’t think H1 vs H2 buffer will make that much difference.

There’s trade offs either way on a DI gun. Cut off the gas and try to keep cleaner or have more gas and the ability to cycle longer when dirty and not be as ammo picky.

If you really want to smooth it out and tune it check out the JP parts. They’re expensive but when it comes to tuning a rifle for the range they’re the best

When it comes to premature wear I’ll let someone else comment. I don’t shoot AR’s nearly enough to give that advice. Although I don’t think an H1 vs H2 buffer will make much difference here either.

But after watching many of these meltdown and torture test videos which are running AR’s that many of us would use on the range you’ll see high end rifles crap out before psa rifles sometimes

TonyAngel · Friday at 10:46 AM

KOPFJÄGER13 said:
I was thinking a well tuned AR15 should cycle 100% with the minimum amount of gas needed (from adjustable gas block) right? So shouldn’t you always pick a low weight buffer and then turn down the gas on gas block? How’s that effect the cycling compared to a heavier buffer with more gas? How’s recoil impulse change or does it? The only difference I see is with lighter buffer and less gas it would run cleaner…… are the principles the same when suppressed?

Light buffer + lower gas = ?
Heavier buffer + more gas = ?

Are they equal??

You aren't wrong, but there are other considerations. First, even if you tune your rifle to shoot softly and run a bit cleaner, it's still going to get dirty.

A softer shooting rifle can be a pleasure to shoot, but a softer shooting rifle often means a slower running rifle. What I mean by that is the rifle's recoil cycle becomes more of a roll than a snap. Kind of like the difference between shooting a .45 vs a .40 cal. When the cycle is rolling, I can almost feel the bolt cycling. When the rifle is snappy, it's all over by the time I've reset the trigger and I'm already on the next target.

Sooner or later, the rifle is gonna get dirty and rifles tuned to run on a heavier buffer usually run more reliably when conditions are less than ideal.

On a standard buffer system, I like running an H2 with a Sprinco white hot spring. On A5 buffer systems, I like an A5H2.

kthomas · Friday at 12:43 PM

hafejd30 said:
I had a AR setup with a lightweight bolt/buffer combo and tuned gas on mid length gas system. Was unbelievably smooth compared to something like a factory carbine setup. Like shooting a 22 mag.

The downside to running that light is you don’t have the spring pressure and weight of the system pushing the next round up. So when things get dirty or cold/wet you can run into issues.

I wouldn’t have set that rifle up for duty or defense use. But for range it was fun

It seems like KAC has found the sweet spot on gassing and reliability.

I know my SR15 is incredibly soft shooting and reliable.

That's what I would try to replicate if it was me.

alamo5000 · Friday at 1:06 PM

KOPFJÄGER13 said:
I was thinking a well tuned AR15 should cycle 100% with the minimum amount of gas needed (from adjustable gas block) right? So shouldn’t you always pick a low weight buffer and then turn down the gas on gas block? How’s that effect the cycling compared to a heavier buffer with more gas? How’s recoil impulse change or does it? The only difference I see is with lighter buffer and less gas it would run cleaner…… are the principles the same when suppressed?

Light buffer + lower gas = ?
Heavier buffer + more gas = ?

Are they equal??

Absolutely a huge conversation to be had here. Definitive answer is not forthcoming because there are way too many variables in play. Generally speaking though you have a bell curve.

At X level of gas the offsetting weight needs to be verified to ensure acceptable function. Too much gas and too little weight and you have a perfect malfunction machine. You can probably get a 90% malfunction rate if you try hard enough.

If Y value is the offsetting weight and gas value is X, the solution you need for a reliable rifle is that Y must be balanced out by X.

Top O' Texas · Friday at 1:53 PM

Low bcg's work great, but the low weight buffer can be the problem? Flatware gives the best solution! I'm no "expert", but am well versed on them. I do many test on recoil mass (more so on ar10's). I will state this as a fact, "gas port size is key for best function even with an agb"! There's no need to use anything heavier than a standard weight buffer (unless its a full auto or burst) on carrier weight and an h2 or more IF the gas port is sized properly! Just like the somewhat issues with the 6.5creed? Several go +2, but is unnecessary as the excuse is it gives time for the pressure to be reduced? Although it does, it doesn't solve the operation of it! AP did a very good job on getting the port size correct on a mid (18") and rifle (22") length gas system. I have 0 (zero) cycling or brass issues when using a standard weight buffer and a non-agb. Can't say that for cbi, faxon and even pr's +2. As most know the 5.56 is by nature op'd for reliability to overcome debris. I don't have any suppressors or any full autos, but do have several AR's with lite bcg's (some with light buffers). The things about agb's is you can tune recoil down and to 1's reloads. Yes, it doesn't require as much gas to cycle when using lite weight recoil parts, but timing can be off. I have an ar 308 20" barrel and uses a 4.3oz buffer and a 9.6oz bcg. No cycling issues.

N_Turs · Friday at 3:09 PM

For me I have a built 2 gun Ar that is as light as possible. The bolt carrier, buffer system, and gas are all super light weight and gas is turned down just enough to cycle. This rifle is a pleasure to shoot very low recoil and lighting fast action. My split times can be as good as .12 sometimes with this rifle. This rifle still gets dirty and being low mass operating system I clean this one more then any other gun I own. It has been very reliable but when really dirty sometimes has a hard time going into battery.

This is where the heavier mass of the carrier and buffer system come in to keep the gun running.

I also have an 11.5 duty rifle that never gets cleaned and is also very soft shooter when suppressed. This has a full mass system in it with a H2 and geissele spring. I also have an adjustable gas block that I run open a few clicks past minimum gas needed to cycle. Ive put 2k through this rifle suppressed without cleaning and have had no issues. I do run my guns pretty wet with oil tho...

Low mass + low gas = Range toy / Match gun
Heavy buffer + full gas = Duty gun or all around beater rifle

Both can still be pleasant to shoot if set up right. Im a fan of adjustable gas blocks and might just be lucky but have never had an issue. Ill add that all my bolts and gas blocks are JP stuff they make awesome product and customer service is top notch.

Id say its more of a use case on how you put a rifle together. Im also not an expert but have been building these things sense 2005 and have been shooting them even longer. Ive never owned a complete rifle all of mine have been built. So while I may not be an expert I do have alot of trial and error experience.

Dev L · Sunday at 1:55 AM

Fo4 small frame ARs... Lowering mass and gas lowers the shake weight effect... the chunck, chunk of the moving mass rocking the gun. The downside is a bigger variance when shooting suppressed and less mass and power to push through fouling when dirty and decreased amount of fouling or cold to prevent bolt locking on empty.

There is zero effect on precision. The reliability issue is 99% the bolt locking back on last round vs. any actual malfunction or stoppage.

Mass regulation is very mild. Spring rate is even milder. Gas is fairly strong. Regulating an over gassed gun is a huge difference. Cutting buffer or carrier weight and resetting even lower gas is a smaller change. My minimums are carbine spring, carbine buffer, JP LMOS carrier. This still provides enough gas when tuned to run 55 grain .223 brass cased that it will still cycle (but not lock bolt back) with a full mass carrier and H1 buffer and suppressed function is still good.The negative is slightly more and faster cycling when suppressed.

Mass cycling is essential for controlling full auto rate of fire. Not for recoil control.

Also, spring rate has almost zero impact on felt recoil but can cause MASSIVE issues with a lightweight operating system. It promotes bolt bounce issues and you need to up buffer weugh5 to compensate... defeating your objective of less recoil.

Now everything changes with other operating systems. For example, large frame ARs do not have a huge operating window as far as mass. You can't do low mass and suppressed or unsuppressed with a single gas setting. Gas system length is also more critical on large frames. To stop early unlock suppressed on a large frame 6.5 Creedmoor, for example, you MUST use a full mass carrier and buffer. I tried every adjustable weight and gas setting on a rifle length 18" 6.5 but ONLY full mass carrier and buffer prevents premature unlock suppressed.

If you want to use a Riflespeed gas block, you can have separate suppressed and unsuppressed settings and drop carrier or buffer weight even more.

Keep in mind your buffer is to prevent bolt bounce. It should be appropriate to your carrier weight and bolt speed. Don't go too light and too low a buffer weight or too fast of a bolt speed without reciprocating weights, especially suppressed.

Trying to regulate with springs won't slow down your opening of the bolt but it WILL super speed up bolt closing and exacerbate bolt bounce.

Steel+Killer · Sunday at 3:42 AM

Odin Works makes an adjustable buffer that you can set up with internal weights to really play around with buffer vs gas I got one and really like it I run it on my suppressed 7.5" 300BLK.

Adjustable buffer and weights | Shop Now

ODIN Works is always looking for new ways to make your build as customizable as possible to fit you, the shooter. This adjustable buffer does just that. Available to fit AR-10, AR-15 and 9mm platforms, each buffer also comes with multiple weights to customize the weight combination for your...

www.odinworks.com

faylix · Sunday at 12:22 PM

Surprised no one had brought up the adjustable JP SCS.

I've been building rifles for a while and I've been chasing that sweet spot of a rifle that is light weight, accurate, low and smooth recoil, and reliable.

Achieving 2 or 3 of those at once is pretty easy - doing them all at once is tougher.

One of my favorite recent features with the 3 setting adjustable gas blocks is the (r)regular (s)unpressed and (d)irty settings. I think an adjustable gas block which can be changed with a finger on the field will cover 99% of your situations.

I think the combo of a mid - rifle length gas system, 3 setting gas block, surefire compensator (with suppressor qd), JP SCS, and low weight BCG.

Add a good fire grip to that and proper body position and I think you can cover 99% of your use cases.

Of course, just like any sports car - running a super sport class rifle will require more maintenance (cleaning) than a beater (truck gun).

Get ready to be that guy that proof marks every nut and bolt.

I'm interested in everyone's ideas for their perfect setup for a rifle that can put down a blazing fast time on a 3 gun course and crawl through the mud while still making the shots that count.

KOPFJÄGER13 · Sunday at 12:24 PM

Dev L said:
Fo4 small frame ARs... Lowering mass and gas lowers the shake weight effect... the chunck, chunk of the moving mass rocking the gun. The downside is a bigger variance when shooting suppressed and less mass and power to push through fouling when dirty and decreased amount of fouling or cold to prevent bolt locking on empty.

There is zero effect on precision. The reliability issue is 99% the bolt locking back on last round vs. any actual malfunction or stoppage.

Mass regulation is very mild. Spring rate is even milder. Gas is fairly strong. Regulating an over gassed gun is a huge difference. Cutting buffer or carrier weight and resetting even lower gas is a smaller change. My minimums are carbine spring, carbine buffer, JP LMOS carrier. This still provides enough gas when tuned to run 55 grain .223 brass cased that it will still cycle (but not lock bolt back) with a full mass carrier and H1 buffer and suppressed function is still good.The negative is slightly more and faster cycling when suppressed.

Mass cycling is essential for controlling full auto rate of fire. Not for recoil control.

Also, spring rate has almost zero impact on felt recoil but can cause MASSIVE issues with a lightweight operating system. It promotes bolt bounce issues and you need to up buffer weugh5 to compensate... defeating your objective of less recoil.

Now everything changes with other operating systems. For example, large frame ARs do not have a huge operating window as far as mass. You can't do low mass and suppressed or unsuppressed with a single gas setting. Gas system length is also more critical on large frames. To stop early unlock suppressed on a large frame 6.5 Creedmoor, for example, you MUST use a full mass carrier and buffer. I tried every adjustable weight and gas setting on a rifle length 18" 6.5 but ONLY full mass carrier and buffer prevents premature unlock suppressed.

If you want to use a Riflespeed gas block, you can have separate suppressed and unsuppressed settings and drop carrier or buffer weight even more.

Keep in mind your buffer is to prevent bolt bounce. It should be appropriate to your carrier weight and bolt speed. Don't go too light and too low a buffer weight or too fast of a bolt speed without reciprocating weights, especially suppressed.

Trying to regulate with springs won't slow down your opening of the bolt but it WILL super speed up bolt closing and exacerbate bolt bounce.

All good info here, what are the signs of bolt bounce and do you see any possible issues initially with my setup starting out?

MaximusDecimusMeidius · Sunday at 2:13 PM

if you know you're going to be shooting a specific load and you're not shooting both suppressed and un-suppressed, then you can normally get your rifle reasonably well tuned with a combination of buffer springs, buffers, and venting on the carrier. You can always go to a YHM suppressor gas block if you're using a high back pressure can and going 100% suppressed.

Using a lot of different loads with different pressure levels and going back and forth between suppressed and un-suppressed with a high back pressure can will complicate things to where different gas settings are needed with and without the suppressor.

KOPFJÄGER13 · Sunday at 2:17 PM

MaximusDecimusMeidius said:
if you know you're going to be shooting a specific load and you're not shooting both suppressed and un-suppressed, then you can normally get your rifle reasonably well tuned with a combination of buffer springs, buffers, and venting on the carrier. You can always go to a YHM suppressor gas block if you're using a high back pressure can and going 100% suppressed.

Using a lot of different loads with different pressure levels and going back and forth between suppressed and un-suppressed with a high back pressure can will complicate things to where different gas settings are needed with and without the suppressor.

This will be suppressed 100% of the time as long as my RC2 ( on the way) doesn’t hurt group size…… will post groups next outing!

MaximusDecimusMeidius · Sunday at 2:21 PM

KOPFJÄGER13 said:
This will be suppressed 100% of the time as long as my RC2 ( on the way) doesn’t hurt group size…… will post groups next outing!

what barrel are you using or the specs as far as chamber, barrel length, gas system length, gas port diameter ... what load do you plan on shooting?

KOPFJÄGER13 · Sunday at 10:16 PM

MaximusDecimusMeidius said:
what barrel are you using or the specs as far as chamber, barrel length, gas system length, gas port diameter ... what load do you plan on shooting?

It’s a factory IWI SPR….. factory 18” SPR profile…factory adjustable gas block…. Geissele super 42 (h2) buffer/ spring….. surefire brake…

went to range once with it, after bout 30-50 rounds it was shooting 10 round groups moa or better, 6-8 out of the 10 were under 3/4”…. Was ejecting at 4-4:30…. Bolt didn’t lock back couple times out of 20 mags….. this was without suppressor

hafejd30 · Sunday at 10:23 PM

KOPFJÄGER13 said:
It’s a factory IWI SPR….. factory 18” SPR profile…factory adjustable gas block…. Geissele super 42 (h2) buffer/ spring….. surefire brake…

went to range once with it, after bout 30-50 rounds it was shooting 10 round groups moa or better, 6-8 out of the 10 were under 3/4”…. Was ejecting at 4-4:30…. Bolt didn’t lock back couple times out of 20 mags….. this was without suppressor

With the can it will likely be perfect. Or open another click or two and you may get it tuned to shoot with and without can if you want

Just fyi

I learned a lesson while tuning one AR. Shooting one round and bolt not holding open. Adjusting until block was wide open and closed off on the bootleg carrier. Rifle was noticeably over gassed

Turned out to be a bad Magpul pmag. That mag went in the trash and cut the gas in half to tune to other mags

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