Gas Blocks, Bolt Carrier Groups, Buffer Weights, & You: How To Tune Your AR-15

Gas Blocks, Bolt Carrier Groups, Buffer Weights, & You: How To Tune Your AR-15
June 7, 2022 Edited March 24, 2023 5159 view(s)
Gas Blocks, Bolt Carrier Groups, Buffer Weights, & You: How To Tune Your AR-15

I can’t tune a guitar, but I can tuna fish rifle! Dad jokes aside, tuning your AR-15 can make a world of difference in reliability, durability, potential precision, and felt recoil.

But how to tune it, where it counts the most, and why you might want to do it can be a bit of a complex topic.

That’s why you’re here though, so read on and find out more!


What Is “Tuning” A Rifle?

Tuning an AR-15 basically means adjusting whatever needs to be adjusted so that you have a perfect mix of reliability and felt recoil.

You have several options for how you tune a rifle from the gas system to the buffer system, but the result is basically the same.

Reliability is always the number one, if your gun won't run then it isn’t very good.

Felt recoil is a controversial topic, but only because macho men don’t know any better. To be clear -- minimizing felt recoil rarely has anything to do with making you more comfortable when you shoot, although that is an undeniable benefit, it has to do with keeping your sight picture as undisturbed as possible.

An undisturbed sight picture means your follow-up shots will be faster, more accurate, and can mean the difference between first place and fifth place or being alive and being dead.

Look at any competition shooter and you’ll see that every single rifle on the firing line is tuned to perfection.


Is This A Waste Of Time?

No. Yes. A very solid “shmaybe”.

If your rifle already runs with no issue and you’re not trying to get your split times down or find a way for you to reach out further and faster, then your rifle is good enough and you don’t need to worry about it.

But if you’re planning a new build, or you do want to make your rifle better, or you just like to tinker with something new -- then I highly recommend tuning your rifle.

Personally, I always tune every rifle I own. Not all of them are tuned the same way, but they are all set up with a goal in mind and I take the time to make sure they are tuned for it.


When To Adjust Your Tuning

As stated above: if you want to lower your split times, make it easier to reach out further and faster, or more importantly if you’re having reliability issues. Specifically, short stroking or failure to eject.

Or you’re just feeling like your rifle is really jarring to shoot.

If you switch from brass ammo to steel ammo (or steel to brass) as your primary type of choice.

Or if you get a suppressor.

Any of these events and it might be time to revisit your tuning and make some changes.


Ways Of Tuning An AR-15

Adjustable Gas Block

The easiest way of monkeying around with your gas system is to use an adjustable gas block. Adjustable gas blocks do what you might expect, they allow you to regulate and change the amount of gas that is allowed from the barrel into the gas tube and ultimately to the bolt carrier group.

They are made by many brands and come in a few flavors, but the two main types are ones that click and ones that don’t.

Clicking gas blocks means there are set intervals that are normally held in place by a detent and give a felt “click” as you adjust through the range. Personally, I like this type best since it’s easier to really tell where you are.

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Non-clicking types are generally just a screw and don’t provide feedback.

Both types work very well, so it’s really up to you on what type to get. Generally, non-clicking ones are significantly less expensive.

While different blocks will have different recommended settings (and you should always follow those instructions) what I normally do is basically turn off the gas then open the gas port little by little or a few clicks at a time while firing just one shot from a magazine with just one shot in it between each set of adjustments.

At first, your BCG likely won’t lock back but eventually, it will. Once it does, I add a 1/4 turn on the gas or 2-3 more clicks, then lock it down.

You should always have slightly more gas than you NEED to allow for changes in temperature, conditions, and ammo.

Adjustable Gas Block on Workbench


Buffer Weight

Buffer weights are the second easiest method of tuning your rifle, or maybe the easiest depending on your approach.

The weights in an AR-15 buffer serve a few functions but their main function is to act as a dead blow hammer when the BCG goes forward and the bolt goes into battery. The dead blow effect prevents bolt bounce (the bolt rebounding and coming slightly out of locking once it slams into battery).

They also act to add or subtract weight to the system. More weight = more force for the gas to have to work on.

If your rifle feels a little over gassed (and most rifles are from the factory) using a heavier weight can help fix that.

On the other hand, if you want to use the least amount of gas as possible (normally by way of an adjustable gas block first), using less weight makes it so you can really tune down the amount of gas.

What weight is best also depends on how long your gas tube is. Rifle-length gas systems need less weight than shorter systems like carbine or pistol.

Carbine buffers come in a few types and the most common weight system is the one developed by Colt. A standard carbine buffer is 2.8 Oz, H1 is 3.6 Oz, H2 is 4.7 Oz, and H3 is 5.6 Oz.

However, those weights depend a little on the manufacturer. Some brands make their weights slightly heavier or lighter but still call them H1, H2, and H3. You should read carefully and double-check.

Generally speaking, heavier is better as long as it works. A heavier weight will reduce the wear on your rifle, give more energy to strip rounds from the magazine, and generally increase reliability.

But too much weight and your rifle won’t function well since there is an upper limit to how much gas you can put into the system.

Bottom line -- most people find that an H2 buffer is a pretty great sweet spot for 5.56 NATO in a carbine or mid-length gas system.

If you’re shooting ARs chambered in things like 300 BLK, 7.62x39, or big thumpers like 50 Beowulf, you might want to get an H3.

And if you’re shooting pistol calibers that are blowback systems -- you NEED to get an extra heavy buffer designed for pistol calibers. Pistol buffers range from about 6 Oz to 8.5 Oz. Using too light of a buffer can damage your lower, BCG, and buffer tube… I speak from experience.

3 oz AR-15 buffer


Buffer Spring

While technically a way to change things up and tune your rifle a little, I don’t recommend trying to use buffer springs to effect real change. Really the only reason I change a buffer spring is that the sound it makes can be annoying or you want an ultra-durable spring that will last a few thousand more rounds.

That is assuming you’re working with 5.56 NATO. If you’re shooting larger calibers, you might want a spring with more power so that you can adjust other parts of the system less.

If that is the case, you should look into those caliber-specific use cases.

I would still recommend looking at the spring as the last stop.

Buffer Spring on Workbench


Bolt Carrier Group

Changing your BCG to tune your rifle is an expensive method of doing it, but it is an option.

Normally if you’re going this route it is to use a lighter BCG. Some bolt carrier groups are skeletonized, some are made from lighter metals like titanium.

There are some mad lad companies making BCGs out of aluminum, but those have really bad performance in durability and I frankly don’t recommend them. The only time they should be considered is for dedicated race rifles built by someone very familiar with the process.

Lighter BCGs are less reliable and less durable, always.

Personally, I would never use a Titanium BCG or a skeletonized BCG unless the rifle was a dedicated competition rifle and I was really trying to eke out the last 1 or 2% of performance that I could get.

In my opinion -- use a normal bolt carrier group and tune around it. Except…

There is one exception to that advice and that’s the adjustable bolt carrier group. Right now, as far as I know, only one company makes an adjustable bolt carrier but it is out there. Really, this only makes sense if you’re shooting a rifle that you shoot suppressed and unsuppressed and switch between the two regularly.

An adjustable BCG works basically like an adjustable gas block in that it regulates the amount of gas allowed into the system.

This is pretty cool if you take your can off and on a lot, but for everyone else, it’s not really a feature that is needed and an adjustable gas block is a more reliable method of doing the same thing. It’s just harder to adjust on the fly.

AR-15 Bolt Carrier Group on workbench



Ammo! You know, the stuff that makes all of the energy that we’re playing with to start with.

Different ammo is going to produce radically different amounts of gas and energy for you to play with. Ammo that tends to run a little hotter like true 5.56 NATO might take a little more taming to get down to a perfect level.

Imported steel-case .223 Remington ammo tends to produce a lot less gas energy and requires more energy to extract in the first place, thus leaving less energy to go around. In that case, a lot less tuning might be needed.

If you can, try to find an ammo type that you like and stick with it. That is really the best way of guaranteeing results range trip after range trip.

But if you’re like me and want to keep your options open, tune your rifle with a bit more gas and energy than you require normally and that should keep you running even with the cheap ammo.

5.56 ammo on workbench


Muzzle Device

Technically not really a way to tune your rifle, but your choice of muzzle device might impact your tuning.

Okay, really it’s just suppressors that make a difference.

While the most effective way of combating muzzle climb and felt recoil is a good muzzle brake, a suppressor will reduce the noise of your rifle and greatly increase the amount of gas going into your system.

If you tune a rifle to have minimum recoil with a suppressor on, there is a very good chance that it won’t work at all or at least won’t be reliable with the suppressor off. Tune a rifle with it off and you might find it very over-gassed when you put it on.

In a case like that, the adjustable BCG can help a lot. Otherwise, you might want to get an adjustable block with easy access or find a happy medium between your two settings.

5.56 Muzzle Brake on Workbench


How I Tune A Rifle

I’m not saying my method is the only way or even the best way, but this is what I do.

Personally, I only look at two things when tuning a rifle -- the buffer weights and the gas block.

If I’m just putting together a fairly standard rifle with no frills, a non-adjustable gas block and an H2 buffer weight are good enough.

But if I want to tune it right I get an adjustable gas block and normally an H2 buffer weight -- although on heavy recoiling rifles I’ve used heavier weights.

Like I said before, I adjust the block so that the gas is basically off and then work up slowly adding more gas until my BCG locks back. I leave it at that setting and make sure it’s locking back consistently for 3 or 5 shots, then tune the gas up a little more to provide a buffer of reliability.


Wrapping Up

Tuning a rifle is fun, to me. I like to tinker with my rifles and I like to learn the finer details about them and tuning a rifle is a great way to get to know it.

From my home defense rifle to my precision rifles, tweaking the gas system to perfection always yields different results and different settings for each rifle. But the end is always the same -- ultra-reliable, maximum durability, and minimum sight picture disruption.


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June 12, 2022
Bobby Landers
November 15, 2022
I have your 7.5 300 black out Pistol upper and I would like to know what buffer weight and spring you recommend Thanks
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