SLR15 RIFLES AR15 / M16 / M4 / AR308 ARMORER COURSE & ADVANCED ARMORER COURSE
When: June 23-26, 2026
Where: Fridley, MN
We conducted a 2-day (16-hour) AR15 / M16 / M4 / AR308 Armorer Course, and Advanced Armorer Course that was hosted by the Fridley Police Dept. This was our 7th time teaching an Armorers week of courses at this location, and we look forward to more in the future. The training room offers great lighting, a large multi HDTV system that allowed us to project some powerpoint and animations onto.
The student base were Law Enforcement Officers from Minnesota, Michigan, Wisconsin and Missouri.
Rifles represented were SLR15, APF Armory, DPMS, Smith & Wesson, Colt, Rockriver, Sig Sauer, BCM, LWRC, JP Rifles, Bushmaster, Windham Weaponry, Daniel Defense, Aero Precision, Anderson, Palmetto State Armory, and a couple of custom configured rifles from parts kits.
Day-1 started the day by going through the course manual that all students are given. Students were supplied with their own set of basic tools that are necessary to do 95% of the work on their rifles (short of restocking and rebarreling, of which wrenches and sometimes fixtures are necessary), 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 way to field strip a rifle, and why we do it this way so as not to cause damage, premature wear or stress on anything. We covered maintenance of where and what to clean, and what needs lubrication to keep it running. We showed why not to use the firing pins as tools. We showed everyone our recommendation of how to remove fouling and why, and everyone got to use our methods. We also showed how to clean suppressors and why.
The entire bolt carrier assembly was covered, to include inspections, maintenance, upgrades, 3 types of gas rings, and differences in finishing and machining. carrier key (gas key) installation and staking, ejector systems, etc. Everyone was introduced to the different types of gas rings. We went through what each types does, and their proper installation order. Bolts were fully gone through, which included extractors, extractor springs/inserts/O-rings. The ejectors were removed, cleaned, and inspected.
Note: Several people found no extractor spring insert in their extractors. We supplied them with new ones.
Note: Several of the APF bolt carriers were found to have gas key staking that was not touching the screws. We supplied the Officers with a torque wrench to make sure they were within proper specs, and then they used our gas key staking tool to get them properly staked.
We got into the lower receiver assemblies, starting with the fire control group (trigger group). We teach this in a building block format, starting with baby steps of getting things out and in, then build into how things work. Everyone learned how to install and remove things so you don’t cause damage. We went through detailed inspections of all the sear engagement surfaces, spring types, single stage, and two stage trigger systems.
Day-2 started with a review of everything that was covered on day-1, with some greater details and myths covered. We then went back into trigger groups in great details, covering single stage, 2-stage, good and bad triggers, differences and options in spring systems, diagnosing problems when semi-auto turns into burst, and showing the differences in quality of triggers that are on the market. Once done with semi-auto trigger systems, we went into select fire trigger groups covering full-auto and burst trigger groups, to include replacement and diagnosing and repairs when experiencing malfunctions.
After trigger systems, we went through the rest of the lower receivers. We covered the proper mounting & gauging, and proper castle nut staking on the collapsible stocks. Several people found unstaked castle nuts, so this allowed everyone to take advantage of our tools and get things done correctly.
Everyone stripped their lower receivers, which allowed a chance for further inspections, and we went through a session on troubleshooting. Once everyone was comfortable with the entire lower receiver assembly, they were put back together, inspected, and made sure everything is in proper working order.
We then got into a session on the timing. This is where we cover proper cycling, covering what effects timing, and how & what happens when it is out or proper time, dwell time, suppressor issues, etc, and how to get things into proper timing. This also led us into piston systems. We covered how the piston system works, break down and maintenance of the system (Yes piston systems do get dirty and have to be cleaned and maintained), how to properly adjust for timing changed, and trouble shooting. We also covered dwell time, and how it pertains to cycling issues, and hopefully got the point across of why we do not recommend barrel lengths shorter that 11.5" on unsuppressed rifles.
Note: During the timing session, we showed examples of adjustable gas blocks, and we also showed the gas control system from https://www.riflespeed.com/, which we like as it is adjustable with a quick turn by hand to one of the 12 different settings, and is well built for durability.
We showed how suppressors are properly mounted and gauged. Several people took advantage of the bore gauges that we make, and checked their alignment on their rifles that had suppressors.
The last half of day-2 was spent on the upper receiver assembly. We covered barrel removal, mounting, fixturing, gauging & inspections. We show numerous ways to fixture a barrel into a vise, and our preference as to which fixtures/methods to use when and how. We showed how to mount, then properly torque and gauge the barrel system, which ensures it is in proper working order.
At the end of the day everyone put their rifles 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.
[u]Here is a brief overview of a few things that were covered:[/u]
History of the Weapon
Cycles of Function
General Disassembly & Assembly
Identification of Common Problems and Parts
Nomenclature
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 Systems & Piston Systems
Parts Interchangeability, including Brands
Headspace
Firing Pin Protrusion
Trigger Systems
Chamber Inspection and Issues
Troubleshooting, diagnosis & repair
Gauging, Inspections, Stress & Interval Issues
Accessories and Customizing
Tool Options and Selection
SOP/MOD Accessories and Additions
SLR15 RIFLES AR15 / M16 / M4 / AR308 ADVANCED ARMORER COURSE
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. We went into great detail about ejection port pattern, which many people think is strictly about over gassing issues, so we showed that there is many other variables that come into play that effect this and how to tune things if necessary or desired, and that in most cases it isn’t something to be worried about as long as the rifle is ejecting the brass with good results for performance.
Firing pins were inspected for length, damage, wear, corrosion and erosion. We showed the evolution of the firing pin assemblies, and 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, everyone took advantage of our equipment and tested their bolts. 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. We showed several examples of bent and warped barrels. We supplied people with muzzle erosion and barrel straightness gauges, which everyone inspected their barrels.
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.
Note: There was a BCM 11.5" rifle that was brought to class for having cycling issues or reliably cycling. The description is that you can manually load it, fire it, the bolt carrier would unlock, but the bolt carrier would not go all the way to the rear to reliably eject the empty casing. The SWAT Team that is using it had sent it back to BCM twice, and supposedly it was checked and found to be fine, and after the second time it was sent back they were told that it had been remounted on a different upper receiver. Upon inspection the screwed on gas block appeared to be properly aligned. The gas key was properly staked, and the gas rings had a seal. The gas tube was within proper spec. It had been properly lubricated with Slip2000 EWL. The gas tube was checked, and appeared to be centered so it didn’t interfere with the bolt cycling. The gas block was pulled and the gas port was measured at .058", which is slightly on the small side. The agency asked if I would take it back with me to our shop and open up the gas port. It was opened up, and sent back to the agency, and it works properly now.
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 casted 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.
Next we moved into chamber polishing, how and why. We started with everyone viewing their chambers up close, then allowed them to polish them. Only one Officer took advantage of polishing his chamber, we did and before and after inspection and people could see a noticeable difference of the mirror shine and it being much more slippery to allow casings to come out easier.
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. Barrels were remounted and gauged 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.
We showed inspection dye testing of parts, bolts and receivers. We showed several examples of cracks in parts and receivers. Everyone who wanted to do dye inspections was allowed to.
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, Schmid, Palmetto State Armory, Anderson 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, this also included making repairs on damaged pin holes. 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 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.
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 / Forends and Modifications
Gas Blocks & Front Sight Base (Pinning)
Flash Suppressors/Muzzle Brakes/Comps/Mounts
Tuning, Harmonics & Customizing
Custom Tools & Fixtures
CY6
Greg Sullivan “Sully”
WeaponsArmorer
SLR15 Rifles
TheDefensiveEdge.com
(763) 712-0123