Friday, December 11, 2020

Brownells AR15 Upper Receiver Lapping Tool - It Works

Brownells AR15 Upper Receiver Lapping Tool - It Works

Back many years ago a number of very high end manufacturers of receivers and match barrels had recommended lapping upper receiver faces to optimize accuracy. Some of those folks were JP Rifles, White Oak, Shilen, Lilja, Black Hole, and Hart just to name a few of the experts delivering that advice. At that point I was younger, less wise, an inexperienced builder and was happy to just screw together one AR after another. 

This advice came back to me as I was chasing down some accuracy issues with an AR15 which should have been a tack driver - instead my first couple rounds were essentially touching and then the groups would string and wander.

Having eliminated all the usual culprits of barrel nut tension, bad crown, scope mounting, I fired up a browser and picked up a Brownells AR15 Upper Receiver Lapping Tool and a tub of Garnett Lapping compound. After using to tool to lap the face of the receiver I was shocked that the $50 investment allowed the premium barrel to deliver tight ½-MOA groups which I knew it was capable of.

THE CONCEPT OF THE BROWNELLS UPPER RECEIVER LAPPING TOOL
The concept of the Brownells Receiver Lapping Tool is pretty simple. The lapping rod is sized to slip all the way into the A15 upper receiver and is then heavily lubricated - thus providing a perfectly straight alignment which the lapping face of the tool can square up the front face of the receiver.  A little lapping compound is applied to the lapping face and the tool is spun with a simple electric hand drill, or in my case I mounted it into my drill press. The lapping tool spins and the lapping compound gently cuts and trues up the face. Usually less than a few thousands of an inch are actually removed in the lapping process. 

The process is a two-three minutes process where new fresh lapping compound is added to the face and fresh oil is added to the spindle inside the receiver. In most situations receivers only needed a little lapping to remove anodizing and true up the face. I did have a couple receivers which did require much more lapping, but that is a story a little later in the article.
Notice how the 4-o'clock to 11-o'clock
position is nice and shiny, but the
other 
11-o'clock to 4-o'clock position
is still black. Keep lapping until
the entire face is silver. Less than a few
thousands of an inch are actually
removed in the lapping process. 

VOODOO OR PHYSICS
Honestly the whole idea seemed like voodoo to me initially. I thought - Why would it make that big of a difference if the barrel is held mechanically solid by a properly torqued barrel nut? I circled back with those same experts to understand what was going on and why this tuning fix worked. The answer was simple physics and the problem is usually to do with unpredictable and often uneven anodizing and/or receiver coatings.

If the barrel extension is not perfectly squarely seated against the receiver face there will be a small gap on one side or the other. The barrel will expand as it heats and then start to wander usually toward that gap as the barrel torque begins to change. What the shooter sees is 2-3 good shots and then shots wandering off in a direction it is a good indication that receiver truing might be the solution. Another symptom is to only see their best groups while the barrel is hot. White Oak noted receiver lapping is critical, as did others, and even a well trained gunsmith. Everyone noted that a barrel will become less and less affected by barrel nut torque the more true the receiver face is.

Sure it could be something else as well. Too loose or tight of torque, a out of round barrel, bad crown, or out of spec headspacing. JP Rifles noted another culprit is too loose a fit between the barrel extension and receiver - they noted when seating the barrel, it should not drop in and wiggle around in there. JP Rifles actually sizes the barrel and receiver so tight that they need to sweat all the barrels into their receivers for the best possible receiver/barrel fit.
Mounting in a drill press allows for
less side to side lapping tool and
receiver movement and thus a better
final result.

PROOF IT WORKS
I was able to secure a group buy on 17.3” AR15 .223 chambered barrels based on Feddersen blanks. After already owning two of these barrels and several Feddersen AR15 pistol barrels, all of them have been insanely accurate ½-MOA capable barrel. Actually I have even seen ¼-MOA after long0term break in. Even the 7.5” Pistol Barrels were delivering 1” 100-yard groups - Accurate I tell ya. One of the friends had put together a build with one of the Feddersen barrels. Though an extremely capable and accomplished long-range precision shooter, he was at best seeing extremely varying 1.25” - 1.75” groups with a serious problem of the groups stringing. I offered to take a look and true up the face and assure the barrel nut was properly torqued.

The face of the “on sale $39 budget upper receiver” was extremely out of true. Where the lapping process usually only take 2-3 minutes, I spent over 10 minutes lapping down the receiver. I had never seen one this bad before so it was a great test. After cleaning and reassembling the upper for him, the friend retested and was now producing consistent ½” or better groups from the same setup and ammo. That my friends is a result and the reason I will never assemble another AR15 without first truing up the receiver face. I am now tearing down ever AR15 I have and using the Brownells AR15 Upper Receiver Lapping Tool. I have yet to see a build which the lapping process did not improve the consistency and overall group sizes to some degree.

FINAL THOUGHTS
If you are into AR15 building and into building a quality AR15 at home, then you should consider the Brownells AR15 Upper Receiver Lapping Tool along with tools like a good vise, punches and Geissele Action Rod. The tool has proven to me to be a critical tool to assuring accuracy on a high quality build.

SPECS
Brownells AR15 Upper Receiver Lapping Tool - $34.99
Brownells Garnett Lapping Compound - $19.99

SOURCES

Check BROWNELLS for the best deals on firearms and accessories




Monday, December 7, 2020

Feddersen Bronze Nickel Alloy 10/22 Receiver and Barrel Update

Feddersen Bronze Nickel Alloy 10/22 Receiver Review


Many of your know Feddersen from my numerous articles noting the mind blowing accuracy of his 10/22 barrels and also a review of his stunning Bronze Alloy 10/22 billet receiver I reviewed about a year ago. To catch everyone up in the event you have not read the above linked article, this building included:
- Feddersen 10/22 Receiver
- Kidd 1.5-lb Single Stage Trigger Unit
- Feddersen 16.25” Fluted Bull Barrel - Muzzle Threaded
- Kidd Charging Handle
- Kidd Match Bolt
- Victor Titan Stock
- The orignal Nikon 3-9 ProStaff scope worked well, but was not able to really allow this gun to stretch its legs beyond 75-yards accurately... yes beyond 75-yards.

I will save you the scroll ahead. This rig delivers sub-1" groups at 125-yards if I do my part. See attached 125-yard group with CCI Velocitor ammo. This is great news and allows me to not worry about my zero changing all while still delivered very tiny .116-inch 5-shot 50-yard groups with Lapua Center-X. Insane accuracy. I love this gun.

SHOOTING AWAY AN AFTERNOON
1-inch squares still seem a little large
for the precision of this rifle even at
125-yards
Last weekend I was able to just shoot away the afternoon nestled into a friend's range on a gorgeous 60-degree day with a pack full of ammo. These days do not get any better than that when you are just alone on the range, quietly plunking away with your Ruger Suppressor muffling the snap of the Ruger 10/22 to a quiet "plunk". There is no better therapy.

I had decided to swap to a Lucid L5 4-16 optic with parallax adjustment and a very nice fine detailed BDC reticle design. Really more than anything I wanted a very fine reticle and also wanted the BDC so I could quickly snap shots of various ranges.  The Lucid 4-16 did that beautifully. 

At this point I know that I am zero'ed at 50-yards with SKPlus Standard two hashes down for 75-yards, four hashes down for 100-yards, and six for 125-yards.  It really is pretty handy and the precision is close enough to minute of rodent hits. Super precision is just a click of two off from those reference points. 

I have Kidd, Volquartsen, Tacitacl Solutions, Clark, Stock, Whistlepig, and even Force, but time and time again the Feddersen barrels are just problem free with ammo, consistant, and super easy to just pull a SwabIt through the bore and be done. Obviously the accuracy does not suck either. This is an 1/8" gun at 50-yards with the right ammo. The prefered subsonic ammo just cannot hold it together like a hyper velocity round like the CCI Velocitor which the Feddersen loves. 





ABOUT FEDDERSEN
The company is known by many names; Feddersen, R4, 1022rifle.com, and Gunbarrels.net.  Feddersen is a name people in the industry know very well. The company was founded in 1979 by Fred Feddersen and has become rather famous for his world record breaking patented R4 SIPR .50 BMG gun barrels.  Fred prides himself on offering the straightest bores in the industry all thanks to his patented process and machines. Each and every step of their in house barrel production is unique and in fact their entire process is patented and a trade secret process.

Unlike many barrel or firearms manufacturers, Feddersen is not buying pre-rifled blanks and just finishing them to their own specs, they are producing 100% of their barrels in house from solid round bar stock.  They have a special drilling process, a patented ultra-sensitive lapping/honing process, unique patented and proprietary SEPR - Single Edged Polygonal Rifling, and one of the few companies in the world which offer a barrel with near perfect centricity and straightness between the bore and profile. 

Amazingly enough their 10/22 barrels start at only $145, The voodoo that Fred’s patented design and trade secret process delivers superb accuracy which rivals the best barrels anywhere. The 10/22 is a pet project of Fred and he continues to deliver new products for the platform including a wide variety of barrels including take-down models and also these receivers.

THE FEDDERSEN BRONZE NICKEL ALLOY 10/22 RECEIVER
Fred offers the receivers in two bronze alloys and aluminum versions. Fred decided on a high bronze content alloy to deliver several advantages.


The bronze nickel based alloys are considerably heavier than aluminum which delivers a stiffer and more substantial feeling 10/22 build which in turn should deliver improved accuracy. The Feddersen Bronze Nickel 10/22 receiver is also naturally slick and for the most part self lubricating. I can tell you that the Kidd Innovations Match bolt glides back and forth like it is on bearings - it is amazingly smooth.


Feddersen integrated an extended 1913 spec picatinny rail into the receiver. Another notable feature is the barrel trunnion v-block area is spec-ed to precisely fit a .920 bull barrel profile, so instead of a gap around the barrel, the trunnion actually provides support to assure there is no barrel droop without any special mounting requirements.

AVAILABLE FEDDERSEN 10/22 RECEIVER MODELS
Feddersen now are in full production of the 10/22 receivers in Bronze Alloy, Bronze Nickel Alloy, and Aluminum billets versions.  The Bronze Alloy Nickel Alloy are $350 retail, this silver colored Nickel Bronze Alloy $375, and Aluminum $275 billets versions. All are available on his site - https://www.1022rifle.com


ACCURACY
The Feddersen barrels alone deliver stunning sub-¼-inch 50-yard accuracy which deliver tricks such as like slicing cards at 25 to 50 yards with the right ammo. The receiver did indeed tighten up my groups even further compared to factory receivers. For this build I choose a 16.5-inch fluted bull barrel with threaded muzzle to use suppressed. A Kidd Innovations match bolt, 1.5-lb single stage trigger, and V-block were used to complete the build along with a Victor Titan stock and Nikon 3-9 ProStaff optic with adjustable objective.


My a point of impact did not change when suppressed at 50-yards with my favorite SK Standard Plus round with my AAC Ti-Rant suppressor installed or removed.


FINAL THOUGHTS
The Feddersen 10/22 receiver is something unique, delivers many features expected of top tier receivers plus the slippery benefits of bronze and the full support of a trunnion v-block area. The raw material look of the bronze alloy is also unique as nearly every other 10/22 receiver is aluminum and colored with some type of anodizing. I like there there is another high end receiver option for 10/22 builders to choose from beyond the typical options such as Kidd, Volquartsen, and Tactical Innovations. What I liked most from this receiver was that it delivered a solid tight beefy-ness to the build that no other receiver offers and with that the potential for improved accuracy - I am certainly thrilled with .116-inch 50-yard groups.


SPECS
Nickel Bronze Alloy $375 retail


BUILD SPECS
Feddersen 10/22 Receiver
Kidd 1.5-lb Single Stage Trigger Unit
Feddersen 16.25” Fluted Bull Barrel - Muzzle Threaded
Kidd Charging Handle
Kidd Match Bolt
Victor Titan Stock
Nikon 3-9 ProStaff scope


SOURCES

Check BROWNELLS for the best deals on firearms and accessories


FJ Feddersen, Inc. - http://www.1022rifle.com/
Kidd Innovative Designs - https://www.coolguyguns.com



Thursday, December 3, 2020

Heckler & Koch H&K VP9 Tactical 9mm Pistol Review

Heckler & Koch H&K VP9 Tactical 9mm Pistol Review


Recently I reviewed the H&K VP9 and frankly am in love with the pistol, the quality and the features are all top of the line. As a defensive pistol it has a level of refinement that is competitively only seen on Sig Sauers and the high tier Walthers, but with features unique to H&K.  The P30 line has been one of H&K's most popular pistol lines and is the reference benchmark for quality in a defensive polymer handgun. That said, H&K fans have been demanding a modern production H&K striker fired option built on the popular P30 ergonomics and magazine. H&K delivered the hugely popular VP9 and now is extending the line with this VP9 Tactical model featuring a threaded barrel. What really sets the VP9 apart from other Heckler & Koch pistols is the common man's price tag and is the company's first sub-$600 priced gun in recent history.  


Now with the popularity of suppressors on the rise, civilians are asking for suppressor ready firearms. The Tactical model is a bit more with a street price usually about $50-$75 more than the initial VP9 model.

Essentially the H&K VP9 Tactical is identical to the original VP9 model with the same supremely awesome trigger break and very fast short trigger reset. The VP9 continues to offer swappable rear backstrap and side grips to customize the grip and the notable charging notches to help with high speed weapon manipulation. Of course the completely ambidextrous design via ambi-slide and paddle mag release is carried over on the VP90 Tactical Model as well. Even the luminous (Glow in the dark) sights and ambidextrous controls are the same. The VP9 and Tactical model are the same guns for all practical purposes.


There was some early rumbling that the VP9 did have a spring which was too weak. I was informed at this year’s SHOT show that all models now feature the same more stiff spring I noticed on this VP9 Tactical. On the show room, you really would not notice, but put an early Gen 1 writers sample VP9 against this new VP9 Tactical and you can feel the recoil spring difference.


There are only two differences between the VP9 and VP9 Tactical. The H&K VP9 Tactical features a threaded barrel and according to H&K’s site the tactical models do not use an O-Ring assisted lockup like other H&K models. Allegedly the O-ring caused problems when a suppressor is attached and only marginally decreases the precision of the barrel-slide lock up. The barrel threading is the infuriating but well thought out 13.5x1 LH thread. Although the intent of was to not allow the suppressor or other muzzle accessory to loosen while shooting due to a right hand barrel twist. It works but irritates me that I need to buy a swap back and forth between 13.5x1 LH and ½-28 thread adapters for my Liberty Mystic X suppressor instead of being able to do an easy swap of the suppressor between other 9mm guns.


Though H&K is usually a little behind the curve in keeping up with the US market, they may actually be a bit ahead of the curve with the pending Hearing Protection Act now having a good chance of becoming law. This is a durable and well tested host that is ready to attach a suppressor whether buyers follow the current tax stamp registration and buying process or get the opportunity to buy suppressors off the shelves if the HPA passes.


I have found the VP9 line of pistols to be extremely accurate with 124gr ammo. At a recent tactical training we had a drill where we had to run from barricade to barricade and pop out and deliver two shots on a steel torso. After the first run and with my confidence instilled in the VP9 Tactical, I ran the course two more times and was delivering quick double tap head shots on the 15-yard steel target. The VP9s are very accurate and with the right ammo notably more accurate than my stock Glocks.


FINAL THOUGHTS
The VP9 pistol represents everything we have asked for and whined about on our Glocks with a level of striker fired pistol refinement which that has only previously been represented in the Walther PPQ. The VP9 Tactical though is not a Walther or a Glock or a Sig Sauer, it is a Heckler & Koch which has its own legacy of extremely high quality, infallible durability and reliability, with leading edge innovations. H&K did not only hit a homerun with this pistol, and the extension of this pistol to potentially capture a new suppressor market with the Hearing Protection Act pending is a very smart move for H&K.


SPECS
Caliber 9mm
Length 7.34"
Width 1.32"
Height 5.41"
Barrel Length  4.09"
Sight Radius  6.38"
Weight (with empty magazine)  25.56 oz.
Weight (empty magazine)   3.28 oz.
Weight (without magazine) 22.28oz
Magazine Capacity 15+1
Trigger Pull 5.4lbs
Trigger Travel   .24"
Return Travel    .12"
Barrel Profile/Twist    Polygonal, 6 grooves, right-hand twist, 1 in 9.8 inches


SOURCES


Check BROWNELLS for the best deals on firearms and accessories



Monday, November 30, 2020

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. 


A HISTORY & WHY WE NEED ADJUSTABLE GAS BLOCKS ON AR15 RIFLES
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.

HOW ADJUSTABLE AR GAS BLOCKS WORK
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.

HOW TO TUNE AN ADJUSTABLE GAS BLOCK FOR PERFORMANCE & RELIABILITY

  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


TUNING OBSERVATIONS
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.


GAS BLOCK RECOMMENDATIONS & FINAL THOUGHTS
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.


SOURCES

Shop the complete selection of Adjustable Gas Blocks at Brownells.com 

JP Rifles
http://www.jprifles.com/

Syrac Ordnance
http://www.syracordnance.com/

SLR Rifleworks
http://slrrifleworks.com/


Read the review of the Syrac Ordnance Gas Block