September 10-11,2018  AR-15 / M-16 / M-4 Armorer Course
September 12-13, 2018 Advanced AR-15 / M-16 / M-4 Armorer Course.

Where:  Weyers Cave, Virginia

We conducted a 2-day (16-hour) AR-15 / M-16 / M-4 Armorer Course, and Advanced AR-15 / M-16 / M-4 Armorer Course that was hosted by the Central Shenandoah Criminal Justice Training Academy in Weyers Cave VA.  This was our first time doing a course at this location, and we look forward to more in the future.  The training room offers great lighting, a projection system and screen which allows us to project some powerpoint and animations onto.   Table top space was interesting, as the room is set up with a desk top / chair combo, which for armorer work on rifles was challenging due to it being small and slightly angled.        

The student base was a mix of local, county, state, and federal Law Enforcement Agencies from all over Virginia and North Carolina.     

Rifles represented were Aero Precision, Bravo Company, Anderson, BCM, Bushmaster, DPMS, Windham, Daniel Defense, Sig Sauer, Palmetto State Armory, Ruger, Colt, Smith & Wesson, Rockriver, and a couple of custom configured rifles from parts kits.

Day-1 started with going through the course manual that all students are given.  Students were supplied with tools, and shown what they are and give sources to obtain them.  Everyone was also given some Slip2000 "EWL" Extreme Weapons Lubricant and #725 Cleaner Degreaser, etc.  A short session of nomenclature was covered, at which time covered every feature and exterior piece of the rifle to include all the hidden design features that most people are not aware of, and everyone prepped the rifles for disassembly work.  Everyone was taught the procedure series of checks that we recommend.   

Everyone was taught our recommended procedure for field stripping a rifle and why.  From there we got into a session on proper maintenance, showing what to clean, where to clean, and how to clean, and followed up with proper lubrication of where and why.     

We went through armoring the bolt carrier assembly showing inspections, maintenance, upgrades, the three different types of gas rings, firing pins, extraction systems, ejectors, etc.  Gas key staking was inspected, and we showed replacements & proper staking.  We also covered bolts, materials, testing, and inspections.   

Note:  Several Officers found unstaked gas keys on their Anderson, and Aero Precision, and Palmetto State Armory bolt carriers.   Some others found light gas key staking on their Ruger,  RockRiver, and Bushmaster bolt carriers.  Officers put the MOACKS and Sully Gas Key Stakers that we brought to good use.

Note:  One Officer found a broken ejector spring on his Bushmaster rifle.  We gave him a replacement.  Broken ejector springs are occasionally found, and can cause ejection issues.  We recommend that ejector systems are pulled, inspected, and springs replaced on a regular basis.         

In the afternoon of day-1 we went through the lower receiver.  We started with the fire control groups (trigger groups).  These were removed and inspected.  We covered single stage and two stage trigger systems.   Everyone learned all the functions of the springs, pins, disconnectors, and how the pins integrate to lock things in.  The last portion of day-1 we showed the eight cycles of firing in great detail, and got into proper timing, the gas system, four gas seals, and the differences between .223 & 5.56, piston vs gas impingement, etc. 

Day-2 started with a review of all that was covered on day-1, at the same time we added more detail and dispelled some myths.  We went back into cycles of fire in greater detail, and then into the timing cycles.  The timing was covered in greater detail, showing issues of guns cycling too fast or slow, stress, and set the tone for troubleshooting throughout the rest of the day. We also covered suppressors, timing issues, stress, maintenance, and mounting.

The rest of the morning was spent back inside the lower receiver, looking at the trigger groups and receiver machining in greater detail.  This detailed session allowed us to show bad factory parts, good quality of parts, single stage vs 2-stage, and how and why these may effect reliability, fail to fires, burst issues during semi-auto fire, etc. 

Once factory machined parts were gone through, we went through where people may alter parts to do a trigger job, the issues with this, and how trigger jobs are done the right way vs screwed up.   We do not recommend that people do a trigger job on a work rifle. The last session on the lower was going through full-auto and burst groups, and illegal street conversions.   

The afternoon was spent on the upper receiver assembly.  We went through the upper receiver, which included the forward assist, ejection port cover, sights & optics issues.  Next was gas tube & piston issues, and how their longevity is related to proper barrel mounting.  Gas tubes were inspected for stress and gauged to make sure they were in spec, this relates to barrel mounting. 

We went through barrels, this included mounting & indexing, types of metals, finishing, longevity, harmonics, etc.  Everyone was allowed to rebarrel their rifles or make adjustments, and few people took advantage of this time and tools being present, and did barrel work.  Several barrels were removed, and none of them were mounted to the Milspec.  All of the barrels that were removed, were remounted, torqued, and gauged for proper indexing they left the class.

Once all the rifles were put back together, everything was inspected and gauged to make sure it was in proper working order.  Everyone did chamber inspections, checked & gauged the four gas seals, firing pin protrusion, trigger press, and headspace.    


Here is a brief overview of a few things that were covered:
History of the Weapon
Cycles of Function
General Disassembly & Assembly
Identification of Common Problems and Parts
Identification of Group Components
Semi, Burst, and Full Auto Parts and Conversions
Complete Armoring Disassembly / Assembly
Barrel Replacement
Cleaning and Maintenance
Sight and Distance Considerations
Ballistic Issues
Barrel: Twist, Length, and Profiles
Gas System
Parts Interchangability, including Brands
Firing Pin Protrusion
Trigger Jobs
Chamber Inspection and Issues
Troubleshooting, diagnosis & repair
Gauging, Inspections, Stress & Interval Issues
Accessories and Customizing
Tool Options and Selection
Iron Sights
SOP/MOD Accessories and Additions



Days 3 & 4:  We started with a review of the standard course.  Everyone was then tasked to do a complete disassembly of their rifles, to include barrel removal.  Everyone did a complete disassembly of their bolt carriers.  We inspected everything for erosion and corrosion.  Examples of the different types of forged, cast, and MIM extractors were shown.  We showed several examples of MIM extractors, failures, and steel cased ammunition issues.  We showed several different types of finishes on extractors, and showed how these perform.  We went back through all the different types of extractor springs, generations of inserts, and differences in springs and treatments, O-rings and D-rings.  Ejectors were inspected along with their springs.  Several examples of different ejector springs were shown, and how spring treatments and materials perform.  Tuning ejection was also covered.  

Firing pins were inspected for length, damage, wear, corrosion and erosion.  We showed competition firing pins, and the why and how for these.  We showed why it is our preference to use stock firing pins in battle rifles and not competition ones.  Bolt and cam pins were inspected up close, noting erosion and stress.  We passed out numerous examples of broken and stressed bolts and cams, and showed why this happens.  We showed what types of testing that bolts and other parts can go through.  We showed how to die test things, and showed several examples of where the die showed stress cracks.  Bolt carriers were inspected closely, with attention to the machining and finishing.  We showed a couple of examples of badly machined bolt carriers, and what their effects on the parts are. 

We replaced several gas keys, to include the use of the MOACKS & Sully Gas Key Staking tools, and then showed our personal preference for counter-staking.  We showed several examples of over-torqued gas key screws, and what problems happened from it.  We showed several examples of damaged & plugged gas keys, and erosion from bad assembly work.  We showed several different carrier key screws in both Allen and Torx style that are available, and showed which ones are better.  

We had people swab out their barrels so we could do a close inspection and gauging.  We showed how and when to use a borescope, and everyone was allowed to go hands on to view the entire internals of the barrel.  We got a closeup view of the chamber, throat & lead areas, rifling, gas ports, muzzle erosion, etc.  We supplied a couple of new barrels that had no erosion or fouling, which allowed everyone to get a close up look at machining, chrome vs non-chrome lining, parkerizing & nitride. Students then scoped their own barrels, noting fouling, erosion, and damage from things like cleaning procedures.  Everyone was tasked with cleaning their barrels, given the options of using solvents like Butch's Boreshine, JB Bore Compound, Barrett Heavy Bore Cleaner, Breakfree CLP, Sweet's 7.62, Slip2000 #725 Cleaner Degreaser & Carbon Killer/Cutter, and Kroil.  We showed several concepts and methods for cleaning, and everyone was turned loose and tasked with cleaning.  Clean barrels where then gauged for straightness.  We showed how barrels get bent & warped.  We showed a couple example of barrels that wouldn't group (15" or more at 25yds), and how these barrels were problematic before they left the manufacturer.  

Once the barrels were totally clean of all fouling, we gauged the gas ports, noting different gas port sizes between makers and barrel types, a reference to common gas port sizes from various makers that are listed in the course material.  We covered gas port erosion and its effects on the performance of the rifle, making note the differences we see in erosion and barrel finishes.  We showed examples of gas ports that were drilled before and after barrel finishing.  We brought a few barrels that had worn out gas ports and erosion, this allowed everyone to get a close up look with the borescope and gauges  

Muzzles were scoped and gauged, with a discussion and examples of when/how erosion effects performance.  Crowns were inspected, and we showed examples of damage.  We showed how to do crown repair, and a couple of barrels were cleaned up.  Several barrels were heavily fouled at the crown, which will effect accuracy, these were cleaned off then inspected.  Fouling build up inside of the flash hider/brake/comp was shown.  All muzzle devices were put back on the barrels.  We showed the difference in the split washer, crush washer, peel washer, and shims, and when & how to use them.  Everyone was also shown the proper way to install and remove suppressor mounts.   

Chambers were scoped with attention on the shoulder, throat & lead areas.  We showed how chambers are cut, reamed, and finished.  This lead to inspecting for headspace, different gauges and chambers were shown.  We provide several types of chamber reamers, and showed where and how these are used.  We moved into chamber casting, and discussed when and how this may be done.  We allowed people to cast a chamber.  This led us to show a few out of spec chambers and how these performed.  We showed a chamber cast from a short barreled rifle from an agency that had the rifle blow up.  This barrel had been blowing primers on Federal XM193, so the agency tried another ammo which blew up the rifle.  When checked by the ammo makers, the chamber gauged at 5.56 NATO.  When we cast the chamber, it was discovered that the chamber was off set to the bore, which is why it was over pressuring and eventually blew up, showing it was the machining that was at fault and not the ammo makers. 

Next we moved into chamber polishing, how and why.  We started with everyone viewing their chambers up close, then allowed them to polish them.  After polishing, everyone noticed that their chambers now had a mirror shine and were very slippery.    

We disassembled some upper receivers, then inspected the machining for stress, corrosion and erosion, and all parts were gauged to make sure things were in spec.  When looking at machining on uppers, we see tolerances all over the place and usually finding more tolerance issues when compared to lowers.  Charging handles were inspected breakage and stress.  We showed several examples of badly machined uppers in the charging handle area, the problems this causes, and how to fix this.  Barrel types, extensions, configurations, types of finishes, receiver types, front sight bases & gas blocks, and finishes were covered in the context of how they integrate.  We showed why people need to use quality and the correct fixture when working with specific barrels and uppers during installation and other barrel work.  Everyone remounted their barrels and gauged them for proper indexing.  Barrel extensions and upper receivers were inspected and we showed how these must integrate correctly together.   We also showed how to true the upper receiver face and why, of which several people took advantage of using the tools to do this on their uppers.  

Lower receivers were disassembled, and we inspected the machining up close.  We showed receivers that were machined so the trigger group was off center.  We showed examples of the different methods that receivers are machined, and how the lower fit works in conjunction with upper receiver fit.  We showed examples of receivers that used different sized hammer and trigger pins and why.  This size difference also must correlate with the lower receiver machining and finishing.  We showed why some students receivers were tougher to get pins in/out and why.  All receiver holes were gauged, and we showed examples of what is the min/max specs for these and why.  We showed several examples of receivers with oval shaped pin holes, why this happened, and why this is bad.  There were several receivers in this class that were machined off center, which was causing stress to the fire controls and receiver. 

Note:  One Officers Smith & Wesson rifle kept breaking hammer pins.   Upon close inspection you could see that the lower receiver walls were thin on the left side and thick on the right, showing that it was machined off center.  Looking at the upper receiver wall thickness, it was thin on the right and thick on the left, indicating it was machined off center.   With further inspection and a little metal die, you could see where the hammer was being rubbed off center as the bolt carrier traveled rearward inside the upper receiver.  

Trigger groups were gone through in great detail.  During our standard armorer course, we go into detail on good & bad triggers, machining and materials used, and their effects.  We reviewed and added on, going back through single stage and 2-stage triggers, trigger jobs, and the differences in quality of materials used and machining.  We provided a bunch of different trigger groups for everyone to go through.  A sampling trigger groups from Colt, Larue, ALG, DPMS, Geisselle, LMT, Rock River, JP Enterprises, and Bushmaster were tried by everyone.  Everyone was tasked with installing several different trigger groups to see their personalities and differences.  When a trigger group didn’t work, we went through them together to show why and where the problem is.   Everyone was also provided with full auto and burst groups.  Once installed, everyone go to see what worked and how.  When something didn’t work, we showed them why.   

The last part of day-4 was spent on barrels and free float tubes.  We showed the different ways that front sight bases are mounted, and the 3 types of pin that are most often used.  We showed how front sight bases are indexed and mounted, and generally why front sight bases cannot be interchanged between barrels, and how the rear sights are designed to work with the front sight type and how this is integrated with the upper receiver.

We showed how we fixture a barrel and front sight base for mounting, drilling, and reaming.  We allowed people to help ream and mount a few barrels.  We showed how to repair some pin holes.  We then moved into gas blocks, and showed several different styles of how these are mounted.  We showed how to properly index these, countersink mounting screws, and lastly how the drill and pin them and why.  We moved into free float tubes.  Several of the rifles present had free float tubes, this allowed people to see how the different systems work and lock down.

We showed traditional standard feed ramps, along with what people call the M4 feed ramps, and we also showed several different makers versions of M4 feed ramps, noting that there are differences between makers.  We showed a collection of bad feed ramp machining, which caused feeding issues.  Everyone checked how their feed ramps integrated, and we came across a few that needed cleaning up.  Everyone was shown how to clean and polish feed ramps, and then we allowed them to do it.  Several people took advantage of polishing the feed ramps on their rifles, a couple of which were not mating correctly where the upper meets the barrel extension, so after a little work things were cleaned up.  

At the end of the day, all rifles were reassembled and fully gauged to make sure everything was in proper working order.    

Here is a brief overview of what was covered in this course:
Cycles of Function & Diagnosis of Issues
Complete Disassembly / Assembly
Identification of Common & Uncommon Problems and Parts
Identification of Group Components & Rare Parts/Configurations
Chamber Reaming & Polishing
Accessories & Upgrades
Barrel Replacement & Modifications
Internal Barrel & Chamber Inspections
Chamber Casting
Feed Ramps
Crown Repair
Detailed Maintenance
Sight and Distance Considerations
Ballistic Issues
Headspacing & Inspections
Trigger Jobs
Detailed Trouble Shooting & Repair
M16 & Burst Conversions & Problems Association
Free Float Barrels / Foreends and Modifications
Gas Blocks & Front Sight Base (Pinning)
Flash Suppressors/Muzzle Brakes/Comps/Mounts
Tuning, Harmonics & Customizing
Custom Tools & Fixtures

Greg Sullivan "Sully"
SLR15 Rifles
(763) 712-0123

Original Post

Are you seeing a lot of MIM extractors in ARs?


I'm either dead right, or horribly wrong. Either way the results should be entertaining.


"Shoot the MOTHERF$%^ER until he changes shape or catches fire"  the PAT ROGERS

cd228 posted:

Are you seeing a lot of MIM extractors in ARs?

We are seeing more MIM extractors and trigger components, usually from rifles people built themselves using parts kits.  We are also seeing a lot of bolts that are made from something other than Carpenter 158 steel.  Lots of bad springs.  Lots of badly machined bargain basement receivers.  I attribute this to the market being flooded with parts that were made by companies that were going to get in on the possible mass gun purchases if Trump had lost the election and we had a different POTUS.  Many of these companies and machine shops had never made a gun part before.  So for the next few decades we will be seeing lots of these parts flooding the market, and people purchasing them in thoughts that they are getting a great deal. 

My advice is to purchase wisely.  When lives depend upon that firearm isn't the time to be purchasing bargain basement deals.  I view a firearm from a Law Enforcement perspective in that lives depend upon that firearm.  This means that the firearm will need to be 100% reliable right out of the box, in all field conditions imaginable, in all weather, with no break in period to work bugs out as it should be reliable out of the box.

When teaching armorer courses, I will ask a few questions from agencies on firearms like:
How long do we keep a handgun?  The average answer is about 7-10 years. 

How long do we keep a shoulder weapon?   The usual answer is "Forever".  Which usually breaks down to 25-45 years.  


So considering that lives depend upon that weapon being 100% reliable, and that the agency will have the firearm 25-45 years, look at it as an investment, so invest wisely, with things like this in mind:

1.  Get something from a reputable manufacturer, who is using quality parts, and those parts should meet or exceed the Milspec.  

2.  Feed it quality ammunition from a reputable US Ammo Manufacturer, using a good magazine (keep in mind that mags are disposable).

3.  Maintain it proactively, and not from a reactive approach where you only deal with it when it breaks.  IMHO weapons maintenance on a firearm should include cleaning & lubrication, inspections & gauging, and should also include the occasional change of springs.    

Greg Sullivan "Sully"
SLR15 Rifles
(763) 712-0123

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