SLR15 RIFLES ADVANCED AR-15 / M-16 / M-4 ARMORER COURSE
When: August 29-30, 2018
Where: Des Moines, Iowa
We conducted a 2-day (16-hour) Advanced AR-15 / M-16 / M-4 Armorer Course that was hosted by the Polk County Sheriff's Dept. This was our third time doing a course at this location, and we look forward to more in the future. The training room offers great lighting, plenty of table space for people to spread out, and a projection system that allowed us to project some powerpoint and animations onto.
The student base was a mix of Local and State Law Enforcement Officers and a few gun enthusiasts.
Rifles present were a mix of Colt's, Daniel Defense, Bravo Company, SLR15, Sig Sauer, Yankee Hill, and a few custom builds.
We started with a review of the standard course. Everyone was then tasked during this course to do a complete disassembly of their rifles, which allowed them to do a thorough cleaning and inspection (To include traditional and advanced gauging). 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 removed the barrels again, and swabbed their barrels to make sure they were totally free of any solvents, lube and debris. 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 allowed to clean 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 tasked people to disassemble their upper receivers, then inspect 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.
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.
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.
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 the day 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.
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
Sight and Distance Considerations
Headspacing & Inspections
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