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17 October 2009, 08:26 #1
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FAQ's, BASIC INSPECTIONS AND PROCEDURES
PAGE ONE
- CARRIER KEY-GAS TUBE INTERFERENCE CHECK
- GAS RING SERVICEABILITY CHECK
- BUFFER SPRING LENGTH INSPECTION
- BARREL INDEXING AND FSB CANTING
- DENTED PRIMER….OK?
- CANTED REAR SIGHT ASSEMBLY
- FRONT SIGHT BASE GAS LEAKAGE
- UPPER RECEIVER INTERIOR FINISH
- GAS TUBE CLEANING
- 30RD MAGAZINE WILL NOT LOCK
- PICATINNY RAIL T-MARKINGS
- TRIGGER PIN WALKING
- THE AR15 & COMPONENT STAKING
- AR15 ROLL PIN CHART
PAGE TWO
- AR15 TORQUE VALUES
- BROKEN TRIGGER GUARD EAR
- A2 PISTOL GRIP SCREW SPEC'S
- CUT CARRY HANDLE BUS
- BUFFER RATTLE
- MIL VERSES CIV CLEANING ACCESSORIES
- GAS TUBE REMOVAL
- OPTIC CO-WITNESS
- CONVERTING THE GI CLEANING ROD HANDLE FOR CHAMBER CLEANING
- APPLYING SLIPPAGE MARKS
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17 October 2009, 08:29 #2
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CARRIER KEY-GAS TUBE INTERFERENCE CHECK
CARRIER KEY-GAS TUBE INTERFERENCE CHECK
ADJUSTING THE CARRIER KEY TO GAS TUBE FIT
Below are examples of gas tube wear.
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17 October 2009, 09:24 #3
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GAS RING SERVICEABILITY CHECK
NOTE: A word on performing of the Gas Ring Serviceability Check
There seems to be an alternate method of performing the Gas Ring Serviceability Check, a method I see quite often referred to on the various AR15 discussion boards.
This alternate method involves standing the cleaned and stripped bolt and carrier on a flat surface such as a table top, and observing if the bolt carrier collapses onto the bolt under the weight of the carrier.
While I have spoken to very knowledgeable individuals who have attended industry sponsored AR15 Armorers Courses where this method was instructed, I have yet to find this alternate method published in any manufacturers maintenance publication.
My personal view on the alternate method:
It should provide the same results as the published method, but may result in changing the gas rings a bit earlier than that of the published method. This simply being, the carrier is heavier than the bolt and will most likely collapse sooner onto the bolt verses the bolt falling free from the carrier when suspended.
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19 October 2009, 18:39 #4
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BUFFER SPRING LENGTH INSPECTION
BUFFER SPRING LENGTH INSPECTION
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28 October 2009, 04:29 #5
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BARREL INDEXING AND FSB CANTING
BARREL INDEXING AND FSB CANTING
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15 November 2009, 14:52 #6
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Dented Primer….Ok?
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14 March 2010, 11:08 #7
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CANTED REAR SIGHT ASSEMBLY
ArmaLite addresses this frequently asked question with their Technical Note 18: M16A2 Rear Sights
http://www.armalite.com/
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21 March 2010, 08:54 #8
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FRONT SIGHT BASE GAS LEAKAGE
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27 March 2010, 11:13 #9
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UPPER RECEIVER INTERIOR FINISH
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27 March 2010, 11:15 #10
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GAS TUBE CLEANING
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20 April 2010, 19:59 #11
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30RD MAGAZINE WILL NOT LOCK
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5 May 2010, 18:41 #12
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PICATINNY RAIL T-MARKINGS
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21 May 2010, 08:27 #13
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TRIGGER PIN WALKING
A Trigger Pin that vibrates out of the lower receiver during firing, is often times referred to as a “Walking Trigger Pin”. “Walking Trigger Pins” are usually the result of two common mistakes made by those new to assembling their own lower receivers involving installation of the FCG (Fire Control Group).
Problem Number One: Hammer Spring Leg Placement
Often times the assembler mistakenly places the legs of the hammer spring under the trigger pin, against the bottom of the FCG pocket of the lower receiver along the sides of the trigger assembly. Taking a look at the diagram below, we see that the hammer spring legs actually ride on top of the trigger pin.
The pins utilized for the trigger and hammer, are designed with two circumferential grooves, one groove outboard and one center. When a pin is utilized in the trigger position, it is retained within the lower receiver by the tension of one of the hammer spring legs riding within the outermost groove of the pin. (See View A of the illustration below.)
If the hammer spring legs are not placed on top of the trigger pin, with one leg placed in the outermost trigger pin groove, the firer may experience a “Walking Trigger Pin”.
Problem Number Two: Incorrect Hammer Spring Installation
Occasionally lower receiver parts kits (LPK) arrive with the hammer and hammer spring separated from each other. If not following the maintenance manual, or detailed assembly instructions, incorrect installation of the hammer spring by the assembler is often times the result. Or, there was a mistake during assembly of the two by the distributor or Mfr., resulting in incorrect installation of the hammer spring.
Taking a look at the illustration below (Position Of The Hammer Spring Legs), we see the correct installation of the hammer spring on the hammer itself. Incorrect installation of the hammer spring on the hammer, can lead to incorrect pressure applied to the trigger pin by the tails of the hammer spring, most critical being the spring tail riding in the trigger pin groove.
This lack of proper spring tail pressure, can often times lead to a “Walking Trigger Pin”.
A not too common problem, but one which I have personally experienced which can lead to a “Walking Trigger Pin”, was caused by the grooves not being cut deep enough in the trigger pin to sufficiently hold the tail of the hammer spring.
In this instance, I had to resort to opening up of the groove, using a small jewelers rat tail file. This was a temporary fix. Removal and replacement of the trigger pin with an in-spec trigger pin would be highly recommended.
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19 June 2010, 12:56 #14
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THE AR15 & COMPONENT STAKING
Definition: Staking is the physical displacement of material into a fastener (screw head, bolt head, ect) in order to prevent backing out or rotation of the fastener resulting in loosening.
The AR15 has two components where staking is beneficial:
- The Bolt Carrier Gas Key
- Carbine Receiver Extension Castle Nut
The Bolt Carrier Gas Key
Below is a cross-sectional view of the Bolt Carrier Gas Key before installation and staking of the Gas Key screw.
Below is a cross-sectional view of the Bolt Carrier Gas Key after installation and staking of the Gas Key screw. Make note of the Carrier Gas Key material displaced against each side of the Gas Key screw head. Serrations in the head of the screw also help grab and hold the Carrier Gas Key material displaced against it.
Bolt Carrier Gas Key after staking.
Carbine Receiver Extension Castle Nut Staking
Below is an example of the Carbine Receiver Extension Castle Nut after staking. In the process of staking the Carbine Receiver Extension Castle Nut, Receiver End Plate material is displaced into the Castle Nut. This prevents rotation of the Castle Nut which would result in a loose Receiver Extension and Stock.
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19 June 2010, 12:58 #15
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AR15 ROLL PIN CHART
AR15 ROLL PIN CHART*
A2 WINDAGE KNOB ROLL PIN
PN: MS16562-103
OAL: 0.673 INCHES MIN AND 0.703 INCHES MAX
DIA: 0.066 INCHES MIN AND 0.069 INCHES MAX
BOLT EJECTOR ROLL PIN
PN: MS16562-98
OAL: 0.360 INCHES MIN AND 0.390 INCHES MAX
DIA: 0.066 INCHES MIN AND 0.069 INCHES MAX
CHARGING HANDLE LATCH ROLL PIN / FORWARD ASSIST ASSY PAWL ROLL PIN
PN: 8448521-2
OAL: 0.257 INCHES MIN AND 0.277 INCHES MAX
DIA: 0.066 INCHES MIN AND 0.069 INCHES MAX
GAS TUBE ROLL PIN
PN: MS16562-106
OAL: 0.297 INCHES MIN AND 0.327 INCHES MAX
DIA: 0.083 INCHES MIN AND 0.086 INCHES MAX
SIDE SLING BARREL MOUNT ROLL PINS
PN: MS39086-93
OAL: 0.678 INCHES MIN AND 0.698 INCHES MAX
DIA: 0.125 INCHES NOMINAL
FORWARD ASSIST ROLL PIN
PN: MS16562-121
OAL: 0.610 INCHES MIN AND 0.640 INCHES MAX
DIA: 0.099 INCHES MIN AND 0.103 INCHES MAX
BOLT CATCH ROLL PIN
PN: MS16562-119
OAL: 0.485 INCHES MIN AND 0.515 INCHES MAX
DIA: 0.099 INCHES MIN AND 0.103 INCHES MAX
CARBINE STOCK LATCH NUT ROLL PIN
PN: MS16562-202
OAL: 0.423 INCHES MIN AND 0.453 INCHES MAX
DIA: 0.083 INCHES MINI AND 0.086 INCHES MAX
STANDARD ISSUE TRIGGER GUARD ROLL PIN
PN: MS16562-129
OAL: 0.610 INCHES MIN AND 0.640 INCHES MAX
DIA: 0.131 INCHES MIN AND 0.135 INCHES MAX
* Part Numbers are from the current Army TM 9-1005-319-23&P W/C #8.