New Aero Precision M5 build using A5 Buffer tube , Tubbs Flatwire spring and H3 Carbine buffer, 16” Aero Upper with adjustable gas block, help

[Gino753]

As the title says, I just ran this build the other day, and to get the gun to fully cycle, I had to open the gas block 11 clicks from closed..Where the gas block opens to a max opening of 15 Clicks

I am using an Aero Precision M5 Lower with an A5 Buffer tube, a Tubbs Flatwire .308 spring, and an H3 5.4oz buffer

Am i good here or should i open the gas port in the barrel more? So that I have more wiggle room?

Or go with a lighter buffer? Or leave it?

The rifle cycled fine

 

[Eagle1899]

Did the bolt lock back on an empty magazine? You can cut the gas until the bolt won't lock back on an empty mag then increase the gas until it does.

 

[Gino753]

Did the bolt lock back on an empty magazine? You can cut the gas until the bolt won't lock back on an empty mag then increase the gas until it does.

Yes the bolt locked back on an empty magazine and the rifle fed nicely, but it took the gas block to be open, 11 clicks from closed, wheres max is 15 Clicks

So i was concearned in that should I have some more wiggle room?

Also it appears that the Bolt catch lifts high enough that part of it has Nicked the inside edge of my upper

Some people have had trouble with the catch not lifting enough to catch the bolt

My catch covers the whole Bottom lip of the bolt face,

I assume it’s the Magazines that are making the catch lift higher than others, as the P-Mag was the one that did the blemish

The Hex mags don’t lift as high

 

[Eagle1899]

The gas port is probably sized pretty close to correct fir the ammo you are running. Large Format ARs are hard on bolt catches. Having a spare or two on hand is advisable. A heavier buffer helps.

 

[Gino753]

The gas port is probably sized pretty close to correct fir the ammo you are running. Large Format ARs are hard on bolt catches. Having a spare or two on hand is advisable. A heavier buffer helps.

Ok..What i also did was make a Shim out of Tough Nylon, with a vent hole in the center to adjust BOlt face to Bolt catch over travel when the charging handle is pulled all the way back.

I learned of this from some builders and from searching online , in that its a good idea to adjust this gap so that the BCG is not having more forward momentum to slam into the catch

My bolt face to bolt catch gap is about the thickness of 2 Quarters

 

[Oso]

The “sling-shot” effect that is mentioned above ^^^ is the result of too light of a buffer spring &/or too light of a buffer weight. Your buffer system should be balanced so that it stops the BCG before it every bottoms out in buffer tube. If it doesn’t then BCG has full runway to build up momentum often skipping over the next round in magazine and also slamming hard into bolt stop. If it is has enough momentum then it'll snap off the bolt stop. By reducing the amount of captured gas used to cycle the BCG, an adjustable gas block is another solution to help tame to BCG’s movement.

There is something going on with your gas system. Assuming size of gas port is within spec then you should only need 5-6 clicks open. The fact that you are 11 clicks means that either your gas block isn’t properly centered/aligned over the gas port or that there is some other obstruction within the gas block. Before installing the adj. gas block did you test the it by turning the Allen key to make certain the gas port opening freely closed/opened?

 

[Gino753]

The “sling-shot” effect that is mentioned above ^^^ is the result of too light of a buffer spring &/or too light of a buffer weight. Your buffer system should be balanced so that it stops the BCG before it every bottoms out in buffer tube. If it doesn’t then BCG has full runway to build up momentum often skipping over the next round in magazine and also slamming hard into bolt stop. If it is has enough momentum then it'll snap off the bolt stop. By reducing the amount of captured gas used to cycle the BCG, an adjustable gas block is another solution to help tame to BCG’s movement.

There is something going on with your gas system. Assuming size of gas port is within spec then you should only need 5-6 clicks open. The fact that you are 11 clicks means that either your gas block isn’t properly centered/aligned over the gas port or that there is some other obstruction within the gas block. Before installing the adj. gas block did you test the it by turning the Allen key to make certain the gas port opening freely closed/opened?

The Upper was fully built including an Aero Precision Adjustable gas block.Factory upper, i just added an Aero BCG and charging handle

The Buffer tube is an A5 Buffer Tube, 7 5/8” long instead of 7” long like these come with fully built

I also have an TUBBS Flatwire Buffer spring as well as an 5.4oz Buffer
As this spring is really long and has to be stuffed in the tube,

Am I still under gassed? And yes the gas block adjuster moves freely,

 

[Oso]

You have a carbine buffer tube and a Tubbs buffer spring that can handle both carbine and rifle length tube. Your buffer weight is on the heavy side. Try swapping it out for lighter weight buffer(s), like 3.8 oz, and see how it runs. No need to go buy new buffer weight (yet)… if you don’t have a spare go borrow one from your AR15 and see how AR10 runs with it.

If this doesn’t solve it then next step is to look hard at adjustable gas block and gas port. You’ll need to remove it to properly inspect and take measurements of gas port diameter as well as confirm alignment. Before you remove it take a fine tip sharpie and draw line around rear of gas block (side facing the receiver) on the barrel. Use calipers to confirm spacing of line to gas port and compare against gas block’s measurement.

Good Luck

 

[Gino753]

You have a carbine buffer tube and a Tubbs buffer spring that can handle both carbine and rifle length tube. Your buffer weight is on the heavy side. Try swapping it out for lighter weight buffer(s), like 3.8 oz, and see how it runs. No need to go buy new buffer weight (yet)… if you don’t have a spare go borrow one from your AR15 and see how AR10 runs with it.

If this doesn’t solve it then next step is to look hard at adjustable gas block and gas port. You’ll need to remove it to properly inspect and take measurements of gas port diameter as well as confirm alignment. Before you remove it take a fine tip sharpie and draw line around rear of gas block (side facing the receiver) on the barrel. Use calipers to confirm spacing of line to gas port and compare against gas block’s measurement.

Good Luck

Ok I will take that rout,

The buffer tube is an A5 Buffer tube also though..im sure you read that, but I just wanted to make sure

The buffer tube is not a regular AR15 Carbine Buffer tube at 7”….instead it’s an extended buffer tube at 7 5/8”

I assume this lets that longer spring stretch its legs a bit and reduce its tension

 

[Evlshnngns]

Your barrel could have a small gas port. Your bolt could be loose tolerance for gas sealing.

If it locks back on empty, What is the problem?

If your rifle was overgassed and you were on setting 1, that would be a problem.

If this is a fine tuning exercise, relating to recoil impulse, please continue.

 

[Oso]

Ok I will take that rout,

The buffer tube is an A5 Buffer tube also though..im sure you read that, but I just wanted to make sure

The buffer tube is not a regular AR15 Carbine Buffer tube at 7”….instead it’s an extended buffer tube at 7 5/8”

I assume this lets that longer spring stretch its legs a bit and reduce its tension

I saw that, but it also isn’t a 10” rifle length tube. Tubb’s indicated that his flat wire buffer spring is compatible in both a Carbine length and Rifle length buffer tube. Based on this the additional 1/2” of length shouldn’t make or break anything.

After you swap out the buffer weight, see how it runs. If it works then test the gas block setting. Completely close the gas block and then open it 6-7 clicks and see if it still works. If it still requires the adjustable gas block to be almost completely open then it’s time to evaluate the gas block and gas port. Good Luck!

 

[Gino753]

Your barrel could have a small gas port. Your bolt could be loose tolerance for gas sealing.

If it locks back on empty, What is the problem?

If your rifle was overgassed and you were on setting 1, that would be a problem.

If this is a fine tuning exercise, relating to recoil impulse, please continue.

I was basically concerned that to get the rifle to run I had to open the gas block up almost all the way..However the more I think about it , the more I think I’m fine for the most part…Maby as OSO mentioned ..check the alignment and the gas port…Go lighter on the Buffer…

As I think about it though..If this rifle had a non adjustable gas block installed from the start, and the rifle running the way it does

I would declare victory, in that at 11 Clicks open from fully closed , The rifle fired every cartridge, fed flawlessly through 50 rounds, grouped the size of a Softball, and locked back on an empty mag.The recoil was non existent..it actually shot smoother than my AK did.

With that said said, these Aero M5’s come out of the bock with (If An Collapsed stock model) a Carbine buffer tube, a AR.308 carbine spring, and an (Cut down) AR15 Buffer “Stubby” stuffed with two Tungsten weights to make 3.8oz

I Built my Aero M5E1 Using a heavier recoil system, and the Gas block still did not require it to be opend all the way to run

So im thinking to maby just run it and let it break in and then check GB Alignment and port size m

My question though, is does a lighter buffer allow less gas pressure to cycle the BCG rearward? Or a lighter spring?

I thought that maby a lighter buffer would maby cause the BCG to return to battery faster? And with less authority? Maby causing feeding issues?

 

[Oso]

There are several ways to skin a cat and tame an AR15/AR10. Regardless of recoil, the least amount of weight reciprocating back and forth between/during shots will be a smoother shooting gun allowing you to stay on target easier and be positioned to more quickly take follow-up shots if needed.

There is a balance between the buffer system (spring and weight) and the momentum of the BCG (mass of BCG and volume/pressure of gas pushing it). Too light of a buffer spring &/or too light of buffer weight can result in buffer system not being effective in catch & return of BCG. The momentum of BCG is determined by the mass of BCG (standard vs lightened) and the pressure (location of gas port along barrel) and volume of gas (size of gas port).

The advantage of adjustable gas block is that you can dial down amount of gas used to drive the BCG. Less gas means less wear on components as well as ability to use lighter components. With less gas driving the BCG, you can use a lighter buffer.

My personal philosophy: There is no reason not to have a reliable gas gun that also shoots softer/smoother.

 

[Gino753]

There are several ways to skin a cat and tame an AR15/AR10. Regardless of recoil, the least amount of weight reciprocating back and forth between/during shots will be a smoother shooting gun allowing you to stay on target easier and be positioned to more quickly take follow-up shots if needed.

There is a balance between the buffer system (spring and weight) and the momentum of the BCG (mass of BCG and volume/pressure of gas pushing it). Too light of a buffer spring &/or too light of buffer weight can result in buffer system not being effective in catch & return of BCG. The momentum of BCG is determined by the mass of BCG (standard vs lightened) and the pressure (location of gas port along barrel) and volume of gas (size of gas port).

The advantage of adjustable gas block is that you can dial down amount of gas used to drive the BCG. Less gas means less wear on components as well as ability to use lighter components. With less gas driving the BCG, you can use a lighter buffer.

My personal philosophy: There is no reason not to have a reliable gas gun that also shoots softer/smoother.

Thank you very much for staying with me on this

So, you recommend an H2? Maby to start?

I have an H2 Ar15/Standard Carbine length Buffer that I originally bought for it, and weighs 4.6oz? Do you think that would make a difference?

This Buffer, I bought for $10 and the bumper felt cheap when I got it so, with that and after researching a little more that the AR10 Originally came with a 5.4-5.6oz buffer, I scrapped that plan and just bought a better quality Novesk H3 5.4oz buffer

 

[Oso]

Hopefully, you should see an improvement with the H2 (4.6oz). If this works then you can consider buying a lighter buffer. My range is just a couple of miles away so a quick range trip takes no effort. If for you getting to the range is costly &/or a drive then you might consider buying a lighter buffer beforehand and trying both of the lighter buffer weights to see how your gun runs.

 

[Gino753]

Hopefully, you should see an improvement with the H2 (4.6oz). If this works then you can consider buying a lighter buffer. My range is just a couple of miles away so a quick range trip takes no effort. If you getting to the range is costly &/or a drive then you might consider buying a lighter buffer beforehand and trt both of the lighter buffer weights to see how your gun runs.

Ok and what would you say is the lightest that an AR.308 Should run? Or where would my limit be potentially

 

[Oso]

Google recommended buffer weight for .308 AR10 and see what is recommended. I think the lightest is somewhere in the 3.8oz.

 

[dellet]

The problem with many of the large frame AR’s is lack of standardization. You really need to look to the manufacturer when it comes to the gas system. This is why buying a barrel from one and lower from another, then a carrier from a third can get entertaining. Most barrels sold separately, are ported for the heaviest buffer for the gas length provided.

When lightening a buffer system keep in mind ejecting a case, is only half the battle. It has to strip the next round from the magazine, chamber it and close the bolt. It’s possible to go too slow and light.

So if you have an adjustable block almost opened all the way to get the rifle to cycle, it was already tuned pretty well. Still doesn’t mean you can’t improve it.

One thing often overlooked is bolt bounce. Almost everyone thinks about keeping the buffer from bouncing off the back of the tube, but forgets about driving the carrier home. This is where a shot or powder weighted buffer really helps. Kind of like hitting an anvil with a regular hammer vs a dead blow. If you’re looking through the reticle and drop the bolt, the difference is quite noticeable.

My softest shooting 300 Blackout is a 10.25” carbine gassed barrel. The book says it can’t cycle subs without a suppressor. And reality shouldn’t cycle supers because of lack of dwell time. Don’t believe everything you read. Flip side is I know some of the guys who were early on working on the first 300 win mags hitting the market. It took them awhile to stop pulling case heads off. You can get pretty over gassed if you not careful.

 

[Gino753]

The problem with many of the large frame AR’s is lack of standardization. You really need to look to the manufacturer when it comes to the gas system. This is why buying a barrel from one and lower from another, then a carrier from a third can get entertaining. Most barrels sold separately, are ported for the heaviest buffer for the gas length provided.

When lightening a buffer system keep in mind ejecting a case, is only half the battle. It has to strip the next round from the magazine, chamber it and close the bolt. It’s possible to go too slow and light.

So if you have an adjustable block almost opened all the way to get the rifle to cycle, it was already tuned pretty well. Still doesn’t mean you can’t improve it.

One thing often overlooked is bolt bounce. Almost everyone thinks about keeping the buffer from bouncing off the back of the tube, but forgets about driving the carrier home. This is where a shot or powder weighted buffer really helps. Kind of like hitting an anvil with a regular hammer vs a dead blow. If you’re looking through the reticle and drop the bolt, the difference is quite noticeable.

My softest shooting 300 Blackout is a 10.25” carbine gassed barrel. The book says it can’t cycle subs without a suppressor. And reality shouldn’t cycle supers because of lack of dwell time. Don’t believe everything you read. Flip side is I know some of the guys who were early on working on the first 300 win mags hitting the market. It took them awhile to stop pulling case heads off. You can get pretty over gassed if you not careful.

Yes that’s where I was starting to think as well,.in that, if this ,Prebuilt Aero precision M5E1 16” upper with its mid length gas system, is able to cycle Reliably and smoothly , while locking back on an empty Magazine , with a Much heavier Buffer, than a prebuilt Aero precision M5E1 would have came with from the factory , then the gas port must be near pretty good.

After all if it would have came from the factory with an non adjustable gas block then this would probably thought of as a pretty well gases rifle

In that you could go a little lighter on the buffer/Spring if needed carefully of course

Being that I have an adjustable gas block on this, with 4 more clicks till fully opend, I think I’m not too bad off

Im going to play with a lighter buffer, and maby shaving the gas port a few thousands , but then again I should be able to go down to around 3.8oz on the buffer so im pretty good there I think

To be honest I can’t believe how smooth this shoots now..No shoulder marks or bruise at all

When I first shot my AK, it was a different story

Plus I have a Limbsaver on this M5, witch is an amazing Butt pad

 

[dellet]

Yes that’s where I was starting to think as well,.in that, if this ,Prebuilt Aero precision M5E1 16” upper with its mid length gas system, is able to cycle Reliably and smoothly , while locking back on an empty Magazine , with a Much heavier Buffer, than a prebuilt Aero precision M5E1 would have came with from the factory , then the gas port must be near pretty good.

After all if it would have came from the factory with an non adjustable gas block then this would probably thought of as a pretty well gases rifle

In that you could go a little lighter on the buffer/Spring if needed carefully of course

Being that I have an adjustable gas block on this, with 4 more clicks till fully opend, I think I’m not too bad off

Im going to play with a lighter buffer, and maby shaving the gas port a few thousands , but then again I should be able to go down to around 3.8oz on the buffer so im pretty good there I think

To be honest I can’t believe how smooth this shoots now..No shoulder marks or bruise at all

When I first shot my AK, it was a different story

Plus I have a Limbsaver on this M5, witch is an amazing Butt pad

You kind of lost me there. Maybe because I’m not familiar with the models.

It sounds like you have a heavier than normal buffer installed.
Then you say you want put in a lighter buffer, and enlarge the gas port.
Thats backwards

If you put in a lighter buffer, you should be able to cut off more gas. You certainly should not need to shave more off the port, make it larger, provide more gas.