Monday, November 30, 2020

Justification for Packable AR15 Pistols in Vehicles

The PWS MOD2 MK107
is the top tier of AR15 pistols.
Justification for Packable AR15 Pistols in Vehicles

An unassuming $40 Eddie Bauer
pack has a suprise in it
Just a few years ago, I would have rolled my eyes at the idea of having a packable AR15 pistol tucked into my vehicle though I have kept a stowing and cased AR15 or Tavor in the truck for years. More times than I can remember that rifle came in handy during impromptu range trips plus the assurance 30-rounds of M855 5.56 can provide when you are stranded at night alongside the road. It also delivered personal assurance that I would have more than just a handgun in an extended survival or personal defense situation with the ability to deliver high precision shots under 100-yards and connect assuredly out to 400+ years if needed. Over the last six months I have worked through a set of theories based on some discussions with some deep experienced friends which I would like to share. One high ranking Army friend formerly a Night Stalker, said “There is no one perfect small arm for any situation, the dynamics of the environment you expect to be engaged in dictate the armament.”  For several reasons, it is my theory that an AR15 pistol is the better personal defense and road travel firearm to have stowed in your vehicle.

Discussing my ideas with a few folks who have been there and done that, I began gaming out a few potential theories.  Beyond the zombie apocalypse type events, there only a couple logically probable scenarios which could occur:
  • Personal defense and security during an active shooter situation
  • General support of survival and security needs (such as being stranded or coming home to forced entry situation)
  • Support of movement to a safe location during a hostile/riot situation
  • … and of course an extremely unlikely situation where everything goes to hell and you need a weapon (EMPs, Solar Flares, invasion, zoombies...etc)

In any other immediate threat situation, the speed and reaction time would require your smaller conceal handgun inside the waistband to come into play first. The logical needs were for a PDW - Personal Defense Weapon which could deliver 90% of the capabilities of a full length rifle with an acceptable tradeoff of shooter comfort. In all those situations Accuracy, Legal Transportation, Accessibility, Maneuverability, and Concealment would all be factors for a firearm stowed within a vehicle.

Over the last couple years I have changed my perspective of AR15 pistols from just range toys to serious viable PDWs - Personal Defense Weapons. The accuracy of these little AR15 pistols has shocked me. One particular AR15 pistol owned can deliver sub-MOA groups from its 7.5” match barrel - yes it will outshoot most rack grade rifles. Most of my other AR15 pistols with premium match barrels can stay well under the 1.5” 100-yard group mark and will keep my 6” steel target clanging away all the way out to 400-yards with ease. After all, AR15 pistols are in essence just short barreled rifles without the stock or rifle classification. The pace at which these little pistols can lay down precision hits is pretty amazing to the degree that I have questioned whether a full sized rifle would really give me that more of an advantage over a PDW for use in around and out of a vehicle.

The SIG MPX pistol tucks into
almost any small pack
If we look at the reality of most urban combat shooting engagements, they occur statistically well under 100-yards which is a sweet spot for a short accurate PDW - Personal Defense Weapon. Statistically it is also unlikely that any more than 10-20 rounds would ever be needed to address a single situation, but the PDW can still deliver plenty of firepower with a 30 or 40-round PMag attached. Four or five extra mags thrown into the carry bag delivers a substantial firepower capability. From very light 40gr high shock hollow points to M855 steel core rounds, the 5.56/.223 offers a lot of options for defense, survival and threat engagement. It is also statistically unlikely to have a need for supporting a long term armed engagement, but again the PDW can still handle that requirement as well. Though I was a little sore afterwards, I did spend an afternoon hammering 500 rounds through my truck AR15 pistol. That problem-free beatdown of that AR15 pistol changed my perception of what AR15 pistols could deliver drastically in just one afternoon. The PDW format can bring the firepower. I would gladly suffer a little discomfort for a one foot shorter gun that is 2-3 lbs lighter for this particular use.

A 7.5-inch Aero Precision AR15 pistol
in an ultralight small pack.
One of the most important points as a civilian is the assuring your are arming yourself in a legal manner. If you have a rifle stowed in your car, it can be problematic as you drive from one city to another or across state lines. Many cities and states have goofy rifle laws which can include requirements for rifles to be partially disassembled and cased and almost always un-loaded. This can be troublesome.

Conversely if you have a concealed carry permit, carrying an AR15 pistol is covered under your permit because after all an AR15 pistol is not a rifle… its a pistol. Unless you are purposefully doing something illegal or demonstrating how easy it is to shoulder a Sig Brace in front of the police, having a loaded AR15 pistol is just as legal as the handgun on your hip. I would suggest referring to your AR15 pistol as a “legal AR format pistol” rather than just an AR15 if questioned. The point here is that in many cases having an AR15 pistol can avoid unintentionally breaking the law should your rifle not fit the widely varying locals regarding stowage for rifles.

Having a legally stowed, cased, and unloaded full sized AR15 rifle in the back of the vehicle is a viable concept, however accessibility to that gun to put it into action fast is another matter altogether. It hardly seems a sound idea to have an accessible loaded AR15 rifle on the front seat of your vehicle with a blanket over for concealment - you’ll likely get arrested. One the other hand, a concealed carry license allows loaded pistols to be concealed, on the person or within a vehicles or in personal belongings. It would seem that if the need arose, playing a legally stowed, loaded and accessible AR15 pistol in a backpack in the front seat would be far faster than walking around to the trunk, opening it, unzipping the rifles case, and loading the rifle.

Mrs Pandemics Trump Trunk Gun
With a 3X optic, 400-yards is not a
long way at all for an AR15 pistol
Maneuvering a rifle inside a vehicle is a tough situation and most would agree that a short AR15 pistol is more appropriate. Thinking through a multitude of situations which could occur on the road, my theory is that it would be preferable to have a short maneuverable AR15 pistol if facing a survival situation or stranded roadside camping inside a vehicle. If clearing between or around vehicles or through an urban environment to make haste back home, a shorter AR15 pistol would also seem to be the better tool than a rifle.

Though Legality is a big issue, discretely being able to move with an AR15 pistol is probably the biggest advantage of all. There is no way even a disassembled rifle is going to slip into a standard sized backpack. If you need to move discretely with your rifle from your vehicle it is going to be really quite obvious you are carrying a rifle around - Hey over here everyone I am got a rifle!  A 10.5” barreled AR15 pistol equipped with a Law Tactical folding buffer tube adapter or stowed with the upper and lowers receivers unpinned slips nicely into any standard backpack or messenger bag and no one will know.  A 7.5” barreled AR15 pistol with Law Tactical Folding stock can fit into pretty much any smaller pack.

It is my belief that any firearm permanently stored in a vehicle should be easily concealed, and clandestinely moved in a public setting without undue attention. There was one situation where my truck needed unexpected overnight service due to an accident and another where the hotel only offered valet parking. In both situations I had to de-weaponize my truck and walk through some rather public areas with what was clearly a gun case. Those incidents taught me a lesson that discrete cases should always be used to house firearms in vehicles even if it is just one of those non-tactical square soft cases. A similar situation occurred more recently again when I forgot to remove my firearms from my truck before routine oil change, however I was able to grab my Eddie Bauer backpack containing my AR15 pistol and backup Glock 17 and walk over to the coffee shop to wait without anyone taking a second look. A standard AR15 rifle is just not going to give you that option unless it is disassembled and in a more discrete case.

A simple two-point sling or a convertible ALG Defense Quad Dual QD sling delivers a carry option which enhances both concealment and handling. If “it” did happen during a hostile situation where LEO and government officials were on high alert and you did have to trek on foot back home, it would be much better to have a little PDW AR15 pistol concealed and slung under a long rain jacket than walking home with a rifle slung over your shoulder.

Sneak Bags 31-inch SPYDER accommodates
everything from PDWs, Tavors, and
disassembled AR15s
The discreet carry Sneaky Bags are a wonderful option with plenty of internal tactical storage capabilities. The medium 31” SPYDER sling bag which looks like a modified tennis racket bag can conceal several firearms at once, but the weight starts to add up. The standard Sneaky 31” SPYDER bag can accommodate a variety of firearms, for example: a Tavor bullpup rifle, a PWS MOD2 pistol PDW, nearly any assembled 12” barreled SBR or AR15 pistol, and dis-assembled (upper/lower) rifles. It is a handy and extremely well made case.

AR15 pistols of course easy drop into almost any backpack and no one pays any attention to your standard Swiss Army or Eddie Bauer backpack. 5.11’s Select Carry sling pack is designed specifically for PDW use. It has a innocuous shape/style and rapid draw feature that makes it one of my favorites for my Sig MPX 9mm and other AR15 pistols.

An Aero Precision AR15 pistol with Law Folding
Tactical Buffer tube adapter, Dolos QD barrel
System upgraded with a Brigand Arms 
hand guard
If you own an AR15 pistol you are missing half of the functionality of the firearm if you have not installed a Law Tactical Folding Buffer tube adapter. This accessory negates the need of disassembling an AR15 pistol to stow it in most backpacks. Deployment is fast - pull from the pack, slam the buffer tube over and charge the AR15 pistol and shoot. This is a setup that can deploy instantly from any discrete bag when “it” hits the fan. If you are considering an AR15 pistol for your vehicle, then this would be a must have accessory from my perspective.

From tiny to capable in under 5-seconds.
The DOLOS V2 also chops an AR15 pistol down even smaller. The DOLOS delivers a ratcheting quick takedown option to remove the barrel with assembly and disassembly occurring in under 5-seconds. The DOLOS V2 is compatible with any Midwest Industries thread pattern barrel nut handguard which it turns out is pretty common including the very trick Brigand Arms Carbon Fiber handguards.

The stock Dolos V2 QD Barrel removal system
from Pantheon Arms
Combined with the Law Tactical folding Buffer tube adapter, the DOLOS can deliver a 10”x8” AR15 pistol (7.5” barrel) package that will fit in most Ipad sling packs such as the Drago Sentry and most small sling packs. The shown build features a 7.5” pencil profile Black Hole Weaponry match barrel, Aero Precision receivers, Phase 5 Tactical Hex2 buffer tube, Sig Brace, Nikon 3X BDC optic, and DOLOS adapter with Brigand Arms carbon fiber handguard. This is a 400-yard headshot capable rig that brakes down to only 10”x8” with a 20-round magazine in place ready to party.

Any firearm within a vehicle has a very high potential to be viewed, handled, and checked during any routine traffic stop. It is my belief that most law enforcement folks are tragically uninformed about what “is legal” when it comes to anything other than a classically sized rifle or pistols. I have had more than a few LEO folks ask me if my Tavor or an AR15 pistol was an SBR. Though we all know AR15 pistols are legally just pistols, however if you are pulled over and you are justifiably searched, I would bet that less than 50% of police would have the knowledge to clearly identify your loaded ready to rock legal AR15 pistol as a pistol - hassle initiated.

The Rogers Rail light is a must for any
AR15 pistol for defense and survival

The Streamlight based light snaps 
on/off any pica tiny rail
and works on pistols and ARs.
Additionally, if your AR15 also looks like an SBR with something a non-firearms educated officer presumes as a stock, you can double the hassle. Sure SB Tactical and Sig Braces are "legal", however this is where I suggest a standard buffer tube might be the better less grey option to avoid extra hassle. Add in that the ATF is again getting a bit murky on whether braces are legal, the less to explain to LEOs the better. Notably with the buffer tube extension the Law Tactical Folding Adapter provides, I would submit that shooting configuration to be so comfortable that a Brace is not required.

Recently I had a series of discussions with some badass military, LEO, and security folks who were convinced that PDWs were the more correct choice for a vehicle based firearm vs a full sized rifle. Sorting through those discussions, the main re-emphasized points were compact size, firepower, 0-100 yard accuracy/lethality, maneuverability, stowed concealment, and the ability to move with the weapon discretely when not in play. 

From my perspective the AR15 pistol meets those needs perfectly. One of my friends said it well - “If you are going to war a rifle is prefered, but for shots that might be fired in, around and from a vehicle or just for personal defense, a faster handling compact SBR, PDW, or AR15 pistol are tough solutions to beat.”

Mr Pandemics gold and grey tiger stripe
Trump Trunk Gun. The Extended A2 Rifle length buffer tube
improves comfort for my 6'1" wife's wingspan.
After a whole lot of shooting and testing, I like the compromise of a 10.5” barreled AR15 pistol. Its has an exponentially quieter bark and fireball, delivers a bit more velocity than a 7.5” barrel, and provides a shooting platform that gives the shooter more room to stretch out. 

My new favorite factory AR15 pistol is the PWS MOD2 MK107 AR15 Pistol with Maxim Defense Adjustable Cheek Rest - truly an amazing firearm which packs beautifully in the Sneaky Bags SPYDER.

Since I do not want a $2500 (including the Vortex optic) potentially stolen from my truck, I opted for part-ing together a couple AR15 pistols. The his and hers Pandemic Truck guns are both based on Faxon ultralight 10.5” barrels, Faxon matched headspaced BCGs. 

A very nice, light, and highly accurate AR15 pistol
My wife’s pistol features an Aero Precision upper, YHM Quick Pull Take-Down Pins, ALG handguard, Rogers Rail light, Burris 3X 332 prismatic sight, Black Rain lower receiver, Mega Arms trigger, and Paracord wrapped A2 rifle buffer tube which extends the “cheek weld” for my wife. We call this the Trump Trunk Gun, since Trump likes everything gold plated… maybe minus the tiger stripe.

My truck pistol uses a Clark Carbon Fiber handguard, Rogers Rail light, Nikon 1-4 scope, Aero Precision optic mount, YHM Quick Pull Take-Down Pins, Aero Precision upper, a billet lower, CMC Match trigger, Law Tactical Folding Buffer Tube Adapter, and A2 rifle length buffer tube.

Check BROWNELLS for the best deals on firearms and accessories

All About Adjustable AR Gas Blocks

All About Adjustable AR Gas Blocks

This last weekend, I was at the range with a buddy who was hammering through rounds on his custom 18” Mid-length AR.  It is a great rifle which shoots very well but does not have an adjustable gas block. Then I pulled out a couple ARs with JP, Syrac Ordnance, and even some home brewed adjustable gas blocks for him to feel the difference.  His actual quote was “holy crap, when can you do that to mine”.  I will almost guarantee that first experience with an adjustable gas block will be an enlightening one. The near absence of recoil and almost non-moving sight picture is stunning to say the least, in the “holy crap why did I not do this before?” kind of way.  I have actually had people flip the AR to the left to check if they were firing an .22LR conversion, but rest assured, it is not magic, it is not voodoo, it is though, just simple physics.

After my very first JP adjustable gas block, I was sold on the having the ability to tune the gas pressure on a standard direct impingement AR15 system. The advantages are a plenty with a large reduction in recoil, faster recoil recovery, faster sight picture acquisition between shots, heat reduction at the bolt, and a bit cleaner running, all being the primary advantages. 

All things in the gas system must be in a zen state of balance, and generally on an AR15 direct impingement system, they are pretty unbalanced tipping gluttonously in favor of a guarantee of reliability while making the deep sacrifice of heavier recoil in the process.  
My DIY Adjustable Gas Block on my Model 1 Sales
Dissipator Build - Hidden under a Troy Extreme Rail
A direct impingement system works pretty simply; round fires, bullet travels down the barrel, pressure is leached off via a gas port (small hole) in the barrel which pushes gas up into a gas block, the gas block reroutes the gas back down the gas tube and back into the BCG (bolt carrier group), that pressure presses on the bolt o-rings inside the carrier which unlocks the bolt and cycles the action. Repeat until the magazine is empty.  

Through that process, you can see that there are a fair amount of timing dependant items which need to work in concert for everything to function, but lucky for us Mr. Stoner was a genius who built a system which could tolerate a pretty significant amount of slop and manufacturing error and still work.  

Installed -My DIY Adjustable Gas Block on my Model 1 Sales
Dissipator Build - Hidden under a Troy Extreme Rail
But, ah ha, there is more to the story.  The length and internal dimensions of gas tube, size of gas port in the barrel, internal dimensions of the gas block, placement of the gas block on the barrel gas port (correctly or incorrectly), barrel length, type of compensator or suppressor, placement of the gas port on the barrel more forward or backward, friction of the BCG, position and condition of the o-rings on the bolt, weight of the buffer, rate of the buffer spring, weight of the rifle, rate of powder burn of the ammo, amount of powder, how hot the primer is, bullet weight, whether the BCG bounced during the last cycle and is oh-so-slightly out of battery or not, a shooter’s shooting style, and more all play roles which much be kept in a zen-like balance for functioning to work at the rifle’s optimum tuning point.  
Check out the Superlight YM AR15 Carrier.  
Bolts Shown - Del-Ton AR15, Spikes M16, 
Fail Zero M16, YM Superlight, YM M16 National Match, 
Model 1 AR15 with JP Bolt, DPMS AR15 
with Model 1 Chrome Bolt
It would be difficult and irritating to have a firearms which were tuned for an optimum point and then not work right when something as simple as a shooter’s grip could throw off the functioning. The reality is we can tune an AR to perform closer to an optimal state however, we will always have to error on the reliability side with a little extra recoil and gas pressure to assure functioning.  

Today we can control gas pressure with Adjustable Gas Blocks like those from Syrac Ordnance, use light weight BCG from Young or JP and low mass buffers and springs, however as we approach closer and closer to the optimum gas system tuning point the more picky the firearms will become to ammo changes. This is because bullet weight and cartridge velocity begin to proportionally become more and more important to functioning. I have heard of some heavily tuned race focused 3-gun ARs which will only function with rounds within a narrow velocity and bullet weight range, but for those guys they have the option to only use that one ammo if they like.

Generally though, AR15’s are setup for reliability and just blow a shitload of gas back into the action to totally overcompensate for a general lack of engineering or understanding of the other variables. This is kind of like saying you need to kick closed every car door regardless of the car, because you had a Ford Van in 1972 that had a door that needed to be kicked closed.

Syrac Ordnance Clamp on Adjustable Gas Block 
& Set Screw version in forground

With the understanding that all direct impingement even mid and rifle-length systems are over-gassed by a little, or a lot, we have attempted to reduce recoil and run time failures by optimizing the tuning of the gas system.  Unfortunately we have done this not by addressing the main problem of too much gas, but by adding heavier upgraded components typically used to tame full auto cycle rates on short barreled military spec M4 rifles.  

Because we have too much unregulated gas, we can either decrease the gas pressure or increase the mass/weight of the components being affected by gas pressure to balance things out. This has lead to people using marginally heavier M16 carriers, heavier buffer springs, then heavier buffers, even heavier, and wow-really that heavy of a buffer. In most cases, the weight seemed to do the trick, however in my opinion we fixed the issue incorrectly and added weight and stress to the entire system. After all, if a little puff of air to a light bolt, buffer and buffer spring will do the job all while delivering less fatigue to the components, then why would we complicate things? Well for one, the general populace can venture too close to the tuning window edge and begin complaining that their rifle being unreliable... and in fact we have seen that with a few tunable piston systems which require hotter rounds to function. 
The JP Rifle Adjustable gas block is
among one of the most well known.

For many of us, the palm to the forehead/illuminating moment came when we started going back to mid-length and rifle-length gas systems which have less gas pressure than our carbine versions, less recoil, seemed to run longer, cleaner, and cooler to some degree, all while being more reliable. Hmmm, less gas pressure.

Most people view the adjustable gas block in the same mindset as a fad like Shake Weights or Chia Pets instead of the innovation that it is.  Oddly many of these doubters I have talked with seem to embrace the adjustable piston systems which [cough] are in essence adjustable gas systems [cough], but they think adjustable direct impingement systems somehow have less merit.  I am a believer in adjustable gas systems, I have shocked and awed myself and others during testing with the dramatic metamorphosis which occurs from transforming a punchy 5.56 AR15 to a flat, soft, and fast shooting firearm by just by reducing gas pressure.

Because adjustable gas blocks also allow you to adjust the gas pressure, a carbine can have the same shooting feel as a mid-length, rifle-length gas systems or obviously even far less recoil than either of those gas systems. No longer do the carbine length rifle get shortchanged. I you you really want to toy around with reducing recoil, JP makes light weight Low Mass buffers and JP & YM both make low mass light weight carriers as well which will let you dial down gas pressures even further.
Look closely just in front of the picatinny rail and
you can see the adjustable gas block's grub screw I DIY'ed
on this Spikes Tactical ST-15 Front Sight Gas Block
With some exceptions, generally all “adjustable” gas blocks work the same. A screw simply pinches closed the gap between the barrel gas port and the gas tube just like a faucet controlling a stream of water.  Micro-MOA is the only company which uses a sliding plate assembly.

There are now a ton of adjustable gas blocks on the market which offer a screw stuck in a gas block. The idea is so simple even a lightly skilled individual such as myself has converted three standard gas blocks to adjustable versions on a two carbines and one mid-length rifle system. THE most significant problem becomes locking in the adjustment.  On some of my home brew versions, unless I have been studious about permanently lock-tite-ing the screw in place, I begin to see pressures slowly increase as the screw starts to walk out.  This is where the patented Syrac Ordnance or SLR Rifleworks adjustable gas blocks are the best options.. it locks into position with a detent so the adjustment will never move on you.


  1. Assure the firearm is unloaded and the chamber is clear
  2. Syrac recommends tuning on a dry un-oiled rifle with the lightest load you will use.
  3. Carefully, turn the adjustment screw all the way down clockwise until it bottoms out, approximately three full turns and then back off one full turn.
  4. Load one round in the magazine and seat the magazine
  5. Shoot the gun with an offhand shooting position. Bolt should lock back.
  6. If BCG locks back, complete 6A, if not complete 6B.
6A. If the BCG locks back, turn the screw clockwise in ¼ turn increments repeating the steps 4-5 until the bolt no longer holds back, then back out counter-clockwise ¼ turn and proceed to step 7.
6B. If the BCG does not lock back turn the screw counter-clockwise in ¼ turn increments repeating the steps 4-5  until the bolt holds back  and proceed to step 7.
  1. Increase in counter-clockwise ¼ turn increments as needed until the bolt holds back successfully three consecutive single round shots.
  2. If successful, your AR15 is now optimally tuned for that ammo.
  3. If concerned with assuring reliability with a broader range of ammo, then add ¼ or 1/2 counter-clockwise turn. You will get a bit more recoil, however your reliability will increase if you swap ammo a lot. I usually add 1/2 turn and rarely have any problems going forward with any ammo.
  4. NOTE - If you move an upper to a different lower assure you use the buffer and buffer spring from the lower used to tune the upper, otherwise the gas block should be re-tuned.
  5. NOTE - Changes to muzzle brakes or flash hiders may require re-tuning.

SLR Rifleworks Adjsutable Gas Block with Detent
Currently My Favorite Gas Block Made

At this point I have converted nearly a dozen AR15s with adjustable gas blocks in carbine, mid-length, and rifle-length systems of which I have made three of the adjustable gas blocks. I have learned a thing or two in the process, but I am am still learning each and every time I start swapping this or that around and change variable the gun operates under. Once you get things set up and tuned plus that 1/4 or 1/2 extra counter-clockwise turn, you will rarely if ever have any reliability issues all while enjoying a better shooting AR.

With an adjustable gas block, a standard AR15 BCG, buffer and buffer spring is actually preferred instead of heavier variants and will allow a lower gas pressure setting and net you the biggest benefit of recoil reduction. 
After all, a lighter BCG, buffer and buffer spring requires less gas pressure to move.
Store a hex key conveniently for adjustments

It has been my experience that heavy buffers, heavy buffer springs, and M16 carrier groups increase tuning complexity as this extra mass is more sensitive to gas pressure and ammunition changes. ARs with these heavier components will require a higher gas pressure setting for operation, and will deliver slightly more recoil when compared to systems with standard components. 

If installed on a defensive rifle I would add at least a ½ to 1 full turn to assure reliability and test three round functioning drills with a couple boxes of shells to assure total functional reliability with your chosen defensive round.  Personally I have found that ½ turn extra seems to provide a broad envelope of reliability for a variety of rounds unless you tend to shoot less expensive Tula and Herter’s ammo at the range which are on the bottom of the .223 SAAMI spec range.
Contrary to rumors on some forums, so far none of my adjustable gas blocks have required special cleaning or cleaning of any kind.

One little trick is to attach the appropriate hex wrench with a little high heat silicon tubing (from most hobby stores) through a hole in the forend nut. It is always there handy in case you need to do a re-tune.

DPMS Oracle DIY Adjustable Gas Block
Peeks through a PRI Forend Some forend
modification may be required for side 
adjustable gas blocks
The most optimal tuning state would be swapping out to the lightest BCG, buffer, buffer spring, and gas setting possible while still assuring reliability.  I am planning a future article just on this subject using the Syrac Ordnance gas block and a set of Young Manufacturing YM Super Light AR15 and heavy National Match M16 bolts for testing.
Syrac Ordnance Adjustable Gas Block
Adjustable gas blocks with forward facing adjustment such as Syrac's are much easier to adjust than typical side mounted adjustment, especially when extended forends are utilized. 

With the exception of the Syrac Ordnance detented gas block, permanent Lock-Tite is a requirement for any gas block, home brewed or otherwise.  

Keep a log book of which ammo you have tested in the gun and what adjustments you have made.  This should give you a good high low range of adjustment to work with in the future.

If you move an upper to a different lower assure you use the buffer and buffer spring from the lower used to tune the upper, otherwise the gas block should be re-tuned. Additionally changes to muzzle brakes or flash hiders, changes to buffer, buffer spring, carrier, bolt, and handloads or low velocity rounds may require re-tuning for optimal reliability.

Although, my garage created adjustable gas block concoctions work perfectly, I would recommend JP, SLR or Syrac Ordnance Gas blocks. The JP models offer a top picatinny rail and Syrac Ordnance provide a low profile alternative which slip under even the skinniest handguards.  From my understanding Syrac will be licensing their gas block patent to several manufacturers. SLR has a bit different design which features a detent for each setting to assure that the set screw will not slip out of adjustment.

Adjustable gas blocks deliver a dramatic advantage for AR owners and can be one of the best upgrades you can made to shoot faster, reduce fatigue on you and your firearm, and may potentially make you AR15 shoot longer without the need for cleaning. 
The sizable recoil reduction can made a huge difference to those who are a little sensitive to recoil and I usually start off new shooter with the very light DMPS Oracle build (shown below) with a Phase 5 muzzle brake and New Frontier polymer lower with a home brew adjustable gas block. The build is joking referred to by all as the squirt gun because of how light it shoots after the conversion. 

AKA - The Squirt Gun
Sure adjustable gas block do require a little tuning and if you swap a low end lower pressure ammo you may have to do a bit of re-tuning to get the reliability you want, however the effort is completely worth it. Adjustable gas blocks make a huge difference in shooting comfort and swapping out gas blocks is a fairly simple task especially if your existing gas block is not pinned. This is an upgrade I strongly encourage.


Shop the complete selection of Adjustable Gas Blocks at 

JP Rifles

Syrac Ordnance

SLR Rifleworks

Read the review of the Syrac Ordnance Gas Block