Never tried either before, but the main goal, aside from obvious things like reliability, is light weight.

Thinking of using a light BCG and adjustable gas block, but this is not my wheelhouse. I know I'd like a gas block that I can adjust without yanking the HG.

It will be run suppressed full time. Will be a range toy at least to start.

Still not sure what barrel length I'll go with, but at least 10.5".

Any input for me? TIA

I’ve done it. Works well.

Most of my builds have had a lightweight focus, including a lightweight BCG in nearly all of them. My favorite setup has been to avoid an adjustable gas block and get a BRT EZTune gas tube setup specifically for your build. Takes out the guess work and keeps it simple.

My favorite build to date used a JP LMOS carrier and their SCS along with the BRT. Not the lightest assembly out there as you can get ultra light buffers and reduced power springs, but it was gassed enough to be reliable but still smoother than any other rifle I'd put together.

That gas tube would make my life easier if it works.

Unsure of what BCGs to consider, though. JP is out just because they are $$$$.

I will be running the Geissele Super 42 setup

I've used several different lightweight BCGs. Some cheaper ones that are just milled out standard BCGs, and they work but aren't as smooth as I'd like. Don't blame you on the price though. I was dreading it as I'm starting a new build, but I got a complete JP LMOS BCG for the price of just the carrier by itself.

My only suggestion for the 42 is to go with the lightest buffer they have, you don't need to go heavy since you'll be able to tune the system going with a AGB or the EZTune gas tube. Ideally, to make the most of the lightweight carrier and adjustable gas, you'll want to get a lighter buffer and a reduced power spring.

What are some of the other light BCGs you have had success with?

So now I have to spend more $ on a new buffer & spring? LOL
I already have the Super 42 setup and it has always worked on every build I have used it on. I think I have a plain old H1 buffer in my parts bin. Worst case, it doesn't work then I try the H2.

Ar15discounts.com.  Usually "unadvertised" $240 when in stock.
$240 isn't much for the best.  Most other sites sell them for about $100 more.  I just picked up another Full Mass from them for about the same price.  Good place to buy from.

The other lightweight one I've used was the RTB lightweight carrier (85$ on RightToBear's site) and the Sharps Low Mass (270$ on Sharps site). I just found that the LMOS was smoother than the others.

You are more than welcome to use whatever buffer you want, I'm just saying that using a light BCG and AGB is only two parts of the system that also involves the buffer and spring.

Standard BCG's have always worked well for me, are cheaper by far and plentiful.

I had one adjustable gas block that installed on a Colt 16" H-bar because the case rims were getting damaged by the extractor yanking the case out while it was still under pressure.

A heavier buffer helped just as much. I ended up going back to the original front sight tower.

A lot of items in the AR marketplace are solutions looking for a problem. If your rifle is running fine, don't try to "fix" it. I would try a heavier buffer first, before getting an adjustable gas block. IMO, going with a lighter BCG is a step in the wrong direction suppressed.  We had to get a heavier buffer for my brother's DD Mk18 after we installed a suppressor, I think we ended up with an H3.

I prefer longer barrels than 10.3/10.5", a 12.5" or 13.7" is plenty short. The only reason I have my DD Mk18 is for clone reasons.

I’ve currently got a 6 ARC running an RCA Ti BCG, Unrivaled Technologies Deadblow Competition buffer, and an Aero adjustable gas block. With a can, it’s only got slightly more recoil than my 5.56 guns, which is pretty good for roughly 20% more powder and double the bullet grainage.

First, you really need to lay out what it is you’re trying to do.  Are you looking to solve a problem or enhance certain attributes of the gun with the swap to a LW carrier?  Bottom line, reducing reciprocating mass can have a detrimental effect on the reliable operating envelope of the gun, especially under less than ideal operating conditions (dirty, cold weather, etc).  Trimming a little bit of weight likely won’t have a noticeable effect, but if you start getting extreme, it can happen.

You also need to look at how you’re accomplishing this.  A JP LMOS (non-aluminum) carrier is roughly 2oz lighter than their full mass carrier.  It’s roughly 2oz - 2.25oz lighter than a milspec FA carrier.  You can drop 1.7oz from the reciprocating system by simply swapping from an H2 to a carbine buffer.  You can drop even more if you start removing weights from the buffer. If you don’t want to buy a new buffer, you can always just disassemble the buffer and swap out the tungsten weights for steel.

End of the day, if weight savings is the primary goal, it’s certainly going to be cheaper to swap a buffer than an entire carrier, so I’d maybe look at that first.  I wouldn’t swap the carrier and leave the H2 because you’re essentially sacrificing nearly all the weight savings you buy with the carrier upgrade.

Did you read my post? I'll be building a new AR from scratch. This is not a case of changing something I already have.

Thank you.

Oh yes, I know, did not mean to come off as saying otherwise.

Trial & error. I can try the H1 first and if the gun is not reliable, put the H2 in. Was just saying I planned to use the Super 42 H2 is because I already have it and it has never failed me in anything.

So what exactly are you trying to accomplish with a LW carrier if using an H2 buffer is on the table?  A standard steel LW carrier with an H2 buffer leaves you with essentially the same amount of reciprocating mass as a standard FA or SA BCG with a standard carbine buffer.  Seems fairly pointless, although it’s entirely possible I’m missing something.

I say this as a guy who has done the whole low reciprocating mass thing to minimize recoil.  This was with an LMOS carrier, gutted carbine buffer (no weights inside), and an AGB.  It was stupidly soft shooting when tuned to a specific light accuracy load.

As someone who uses AGBs and lightweight internals extensively for race guns there’s no way in hell I’d use them for anything real world.

This is just a range toy & I want to see how light I can make the gun without spending a fortune

This 100%

If that’s the goal, it seems a bit counterintuitive to keep a heavy buffer in the gun.

I already stated I'll try H1 first.

What are the best lightweight gas blocks that can be adjusted without removing the HG?

My 3 gun AR for the last decade runs a light gas system.

Ace Ultralight rifle stock with rifle buffer, empty. maybe 2 oz.

Tubb's constant force flat wire rifle buffer spring.  A good spring is a must with a light buffer. This prevents bolt bounce.

JP low mass BCG.

Stretch16 barrel with intermediate gas port. The longer the gas system, longer the dwell time.

I forget the brand, maybe SLR, but low pro adjustable gas block. Adjustable GB is a must with a low mass system. As far as which manufacturer to get, just one of the good names with a from set screw. A long hex wrench will make it easy to adjust.

Titan brake. (loudest MFer on the planet)

This gun has NO muzzle rise and very little recoil. Least recoil of any 5.56 AR i have shot. AR with Vortex PST Gen 2 1-6x weighs just under 7 lbs.

Follow up shots are super fast. I can get 5 shots of on target in less than 1 second.

If you go too light, you will suffer when shooting suppressed. If you go too heavy, you defeat the purpose of lightweight reciprocating mass and have to up your gas setting to match that weight.

If you want a set it and forget it adjustable gas block... one that is gassed ideally for unsuppressed to minimize how  overgased you are suppressed... I only reccomend the Superlative Arms gas block at this point. It has the best reliability, fit inside rails, high(est) number of settings, reasonable price and least likely to freeze up.

You set it up once and leave it. I only use the restrictive mode on all mine. They come in steel or in titanium if you are doing a lightweight build. The titanium is way too expensive if not doing a dedicated lightweight build and offers no other benefit IMO.

If you want to adjust the gas between suppressed and unsuppressed on the fly, I would only consider the RifleSpeed. It is expensive and heavy compared to the Superlative, but allows for tool free adjustment to get the suppressed setting dialed in perfectly when suppressed and the unsuppressed setting dialed in perfectly when removing the suppressor. Plus you can add a single click to either in adverse conditions when dirty.

For weight... I don't like the titanium or aluminum carriers. They are too light for a single setting gas block tuned for usuppressor if you intend to shoot suppressed IMO. I only run LMOS carriers at this point. I know you don't like the price, but the JP bolts are THE BEST bolts you can buy for a precision build and worth the extra IMO. The JP carriers are THE BEST machined carriers made, and I have pretty much tried them all. If you buy one you won't be disappointed in the quality.

The JP LMOS is also in a sweet spot for weight/reliability where I 100% trust them for a duty rifle and I would (and do) trust my life to them. They can be expensive, so you want to buy them on sale. Sometimes it is cheaper to buy the bolt carrier group together. Other times it is cheaper to buy the carrier seperate. But I ALWAYS buy on sale. MSRP is a rip off. I usually look all year and buy once per year to keep a spare in my parts bin so I don't ever get stuck paying full price. I have 5 builds with LMOS carriers currently. 2 were bought seperate. 2 were bought with bolt, one carrier was purchased used.

I ALWAYS use a real buffer with real dead blow weights for reliability. This means a standard 3.0 oz carbine buffer. There is NO REASON to use an H or H2 buffer to start. That means you have more  reciprocating weight,  which means a higher gas setting, which is counter productive. The only time I run an H buffer is when the rifle runs 100% at a particular gas setting with a carbine buffer and the H buffer STILL runs 100% on the same setting and I want to reduce my suppressed recoil on a build that is not an "ultralight" build.

I also use a JP polished recoil spring in my bullds which is highly underrated. If you have a nice intermal finish on your receiver extension, the JP polished spring  and LMOS carrier with a thin film of grease on your spring will make your action feel like absolute butter. People actually comment unsolicited and ask how I get the action so smooth on my builds when they try them for the first time it is so noticable.

Remember, weight in the reciprocating mass is your friend if you want to decrease the delta between suppressed and unsuppressed gassing/recoil. However, if you want less unsuppressed recoil and can tune your gas perfectly, I find the LMOS carrier/carbine buffer/JP polished carbine spring to be an excellent sweet spot for lower weight, high reliability, and still suppressor friendly. The heavier buffers are for tuning overgassed rifles with the extra mass or controlling full auto cyclic rate. If you tune the gas down on a semi auto, you don't need them. If you want the absolute lowest recoil suppressed you have to tune the rifle to the suppressed setting, which means a RifleSpeed gas block or using a Superlative Arms setting where unsuppressed your rifle runs but will not lock your bolt back on the last round. I would not trust my life to a rifle tuned to barely run but not lock the bolt back unsuppressed with a single fixed gas setting.

When you tune the rifle, I suggest using .223 brass cased 55 grain FMJ and get the bolt to just barely lock back 100% of the time unsuppressed in cool weather. DO NOT add an "extra click for reliability" as that defeats the purpose. Heavier/hotter ammo, warmer weather, parts wearing in, and gas block errosion will all provide "extra" reliability on their own. Remember, extra click of reliability = extra overgassing suppressed.

Also, keeping your rifle clean, especially when shooting suppressed, will become more important to maintain perfect reliability with a single setting gas block. Locking back on the last round when dirty is litterally the only thing you are risking reliability wise after the first few mags suppressed. But you can't just not clean the rifle over multiple shooting sessions and expect the reliability of a full mass, high gas setting rifle.

I really hope you listen to the advice and go Superlative Arms/LMOS/carbine buffer as it is noticeably lighter, yet still 100% reliable. Hollow or plastic buffers,   extra heavy buffers, "lightweight" skeletonized carriers that are heavier than the LMOS, or titanium/aluminum carriers that are way too light either wont offer any improved recoil or will not play well with suppressors at all in my experience. So do it right the first time. Nothing is more expensive than fixing a screw up with a second set of parts.

A lot of information. Much appreciated. Is the JP LMOs linked below the one you have? It says .223, but fine for 5.56 as well I assume?

https://jprifles.com/buy.php?item=JPBC-3

I don't think I'll ever shoot it unsuppressed. It's just too much fun with a can

I switched to Riflespeed adjustibles and they are bad ass.   The D2 models made by JP are great too

What made you switch?

Yes, that is it. They only make two size carriers... small frame (AR15) and large frame (AR10) but there are many different JP Bolts (calibers, firing pin sizes, finishes, etc.) Everything listed .223 will work for 5.56.

If you're paying for a lightweight carrier, why would you use a heavier buffer than standard, like the H1?  Take a standard buffer & dump all the weights out.

I think you're going to be cleaning quite a bit, I'd suggest a chromed LW carrier.

Thank you

I never said I am married to anything. :)

I clean after every range session anyway. I'm a little OCD