The topic of anti-rotation / anti-walk pins comes up now and then, and we'd always regretted not saving this splendid article Chad wrote about the use of anti-walk, or anti-rotation pins, we got a chance to see it again lately and will now make it a page we can come back and point to folks that ask us about it.
For the record, we're against them. They're unnecessary for properly designed and made triggers. If your triggers require them, our advice is to get a properly designed trigger that can hold the trigger and hammer pins without needing external help in the form of screws and anti-walk/anti-rotation pins, AR15 and M16 triggers and hammers should not need them. Vietnam war era M16s, and M16s/M4s in US military service since then have never needed them, these weapons see far more use and go through many users than most of the AR15s and M16s in civilian hands, that alone should be clue enough. Properly designed and made triggers don't need anti-walk pins, nor do they benefit from them.
Below is the article written by Chad Albrecht of SOTAR (School of the American Rifle), it's a very insightful read.
1) The use
of Anti Walk/Anti Rotation pins shows the Manufacturer of these devices
and the consumers who buy them dont understand how the AR15 or M16
trigger mechanism is designed to work.
Eugene Stoner and Jim Sullivan designed the weapon so the Hammer and Trigger Pins would float (Rotate) each time the weapon is fired or the bolt cycles. When a user installs Anti Rotation Pins, the Pins are locked in place and they can't float/rotate as intended. This slows down lock time (Hammer Speed) due to friction and increases the chance of a Trigger failure to reset or a fail to fire (Light Strike) if the Fire Control Group gets fouled.
These issues get worse if there is not sufficient lubricant present in the Lower and the moving components.
2) In my experience almost all Anti Rotation Pins are softer and will gall or break long before a GOOD Milspec Hammer or Trigger Pin. FWIW, Nitrided ARP's do have much better durability than their bare stainless steel counterparts. When Anti Rotation Pins gall it can cause the F.C.G. to not reset or fire in the same ways mentioned above.
Users of ARP's can allow MORE damage occur when Anti Rotation Pins break because you won't know the Pins are broke. Standard/Floating Hammer and Trigger Pins will walk out of the Lower when they break giving you and indicator that they are broken. That is a good thing.
I have worked on and observed Registered M16, Commie State Pre-Ban, and S.B.R. Registered Lowers that got chewed up because the ARP Hammer Pin broke and didn't walk. When this happens, it chews up the Hammer Bore in the Lower Receiver and requires sleeving to fix.
3) Almost all versions of Anti Rotation Pins require tools to remove the Fire Control Group. With Standard/Floating Hammer & Trigger Pins, the Firing Pin can be used in the field to remove standard/floating F.C.G. Pins. This should NOT be done often as it can damage the Firing Pin Tip. Why would you need to remove the pins in the field or the range? If you get a popped/blown primer in the F.C.G. pocket in the lower, it will require removal of the F.C.G..
The screws that are used for ARP's are not very strong at all, so if you are dead set on using them, please use a Inch # Torque Wrench to install them. 10 IN# is a good setting to use. Too much torque can stretch or break the screws and the torque wrench takes away the human capacity to break them. I have also seen cases where they can slightly collapse the FCG pocket in the Lower Receiver which will cause additional FCG binding.
4) ARP's can cause problems in user completed 80% Lowers. Galvanic corrosion can happen if you have bare stainless ARP's sitting in a the Non-Anodized Hammer and Trigger Pin Bores. All it takes is insufficient lube and some moisture for the corrosion to begin.
5) Amateurs removing/installing the F.C.G. improperly or excessively is what causes the Hammer and Trigger Pins to wear.
Rotation of the Hammer and Trigger Pins are not what causes significant wear to the Hammer and Trigger Pin Bores.
6) Other issues that can cause the bores to enlarge can be wear due to contaminants and fouling combined with a lack of proper lubricant. Lack of lubricant can also allow galvanic corrosion to occur due to dissimilar metals making contact. This only happens once the finish wears off on the Hammer/Trigger Pins and the anodizing wears down in the Hammer and Trigger Bores.
7) M16 owners buy them out of unsubstantiated fear of their investment wearing out, but data does not prove this out. AR15 owners buy them for the same reasons but sometimes just want another "doodad" on their gun.
The U.S. Government makes a USGI Plug Gauge to check for Hammer and Trigger Bore wear. I own this Gage (Several in fact) and I also have custom ones that I have made to measure the wear graduated wear over the weapons service life. It takes tens of thousands of rounds/F.C.G. Cycles to even begin to wear the hammer bores +.001 on a properly assembled and lubricated AR15 or M16 with a forged Lower. The failure point is +.008 from new (.163). I have spoken to countless Military Armorers who have used the USGI Plug Gage and they have consistently told me that they can count on one hand how many lowers have failed the Plug Gage. Even on heavily abused guns it's rare to fail the USGI Plug Gage.
Does anyone not find it odd that these companies who sell ARP's, don't sell the gauges to actaually check for wear but have no problem selling the public a product to "prevent wear". Sorta backwards isn't it?
If there was a problem with U.S. Government M16/M4 Lower Receivers wearing out then ARP's would be an easy fix, but they are not. The lower receivers don't get replaced for wear from pin rotation. They get replaced due to getting ran over, other service related conditions, and people removing the fcg for no reason.
If ARP's were worth a darn then they would have found their way on to the MK18 or some other DoD PIP. If there was a problem a PIP would have been implemented for the M16 variants, M4 variants in service. If there was an improvement to be made in this area then Colt, Knights, FN, or Geissele would have made use of the concept and pushed it.
So in summary.
If you want good Hammer/Trigger Pins use them from Colt, LaRue, SOLGW, Sionics, Geissele, etc, and just keep the firearm generously lubricated.
As long as you don't take the FCG out repeatedly, and lubricate the firearm the bores in the Lower wont wear out.
FYI, Anti Rotation Pins are also NOT to be used with Geissele Triggers. Email Geissele if you want secondary confirmation.
In my experience the only applications where ARP's may be necessary are when using Cassette/Pack type AR Triggers. My experience with Cassette/Pack Triggers has shown me they are unreliable gimmicks as well so the idea is a wash.
If your gun requires the use of ARP's then you have a problem that should be addressed, not covered with a bandaid fix like Anti Rotation Pins.
Users of Blowback 9mm's and .22's report they can't use regular Hammer and Trigger Pins because they break in their blowback AR. If you are breaking Hammer and Trigger Pins then you have a non balanced buffer or recoil system. It means you need to make changes to the gun such as a tungsten carrier weight, shorter barrel, heavier buffer, or a heavier buffer spring.
If you like your Anti Rotation Pins, keep them, but understand that if you are a competitor, they might cost you a match one day. If you hunt with an AR it may cause you to miss a shot. If you use an AR for defense or L.E. work, it may cause your gun to fail when it's called into service.
God Bless Eugene Stoner and Jim Sullivan's Masterpiece. Lead not his disciples to perform blasphemous deeds to their AR.
Eugene Stoner and Jim Sullivan designed the weapon so the Hammer and Trigger Pins would float (Rotate) each time the weapon is fired or the bolt cycles. When a user installs Anti Rotation Pins, the Pins are locked in place and they can't float/rotate as intended. This slows down lock time (Hammer Speed) due to friction and increases the chance of a Trigger failure to reset or a fail to fire (Light Strike) if the Fire Control Group gets fouled.
These issues get worse if there is not sufficient lubricant present in the Lower and the moving components.
2) In my experience almost all Anti Rotation Pins are softer and will gall or break long before a GOOD Milspec Hammer or Trigger Pin. FWIW, Nitrided ARP's do have much better durability than their bare stainless steel counterparts. When Anti Rotation Pins gall it can cause the F.C.G. to not reset or fire in the same ways mentioned above.
Users of ARP's can allow MORE damage occur when Anti Rotation Pins break because you won't know the Pins are broke. Standard/Floating Hammer and Trigger Pins will walk out of the Lower when they break giving you and indicator that they are broken. That is a good thing.
I have worked on and observed Registered M16, Commie State Pre-Ban, and S.B.R. Registered Lowers that got chewed up because the ARP Hammer Pin broke and didn't walk. When this happens, it chews up the Hammer Bore in the Lower Receiver and requires sleeving to fix.
3) Almost all versions of Anti Rotation Pins require tools to remove the Fire Control Group. With Standard/Floating Hammer & Trigger Pins, the Firing Pin can be used in the field to remove standard/floating F.C.G. Pins. This should NOT be done often as it can damage the Firing Pin Tip. Why would you need to remove the pins in the field or the range? If you get a popped/blown primer in the F.C.G. pocket in the lower, it will require removal of the F.C.G..
The screws that are used for ARP's are not very strong at all, so if you are dead set on using them, please use a Inch # Torque Wrench to install them. 10 IN# is a good setting to use. Too much torque can stretch or break the screws and the torque wrench takes away the human capacity to break them. I have also seen cases where they can slightly collapse the FCG pocket in the Lower Receiver which will cause additional FCG binding.
4) ARP's can cause problems in user completed 80% Lowers. Galvanic corrosion can happen if you have bare stainless ARP's sitting in a the Non-Anodized Hammer and Trigger Pin Bores. All it takes is insufficient lube and some moisture for the corrosion to begin.
5) Amateurs removing/installing the F.C.G. improperly or excessively is what causes the Hammer and Trigger Pins to wear.
Rotation of the Hammer and Trigger Pins are not what causes significant wear to the Hammer and Trigger Pin Bores.
6) Other issues that can cause the bores to enlarge can be wear due to contaminants and fouling combined with a lack of proper lubricant. Lack of lubricant can also allow galvanic corrosion to occur due to dissimilar metals making contact. This only happens once the finish wears off on the Hammer/Trigger Pins and the anodizing wears down in the Hammer and Trigger Bores.
7) M16 owners buy them out of unsubstantiated fear of their investment wearing out, but data does not prove this out. AR15 owners buy them for the same reasons but sometimes just want another "doodad" on their gun.
The U.S. Government makes a USGI Plug Gauge to check for Hammer and Trigger Bore wear. I own this Gage (Several in fact) and I also have custom ones that I have made to measure the wear graduated wear over the weapons service life. It takes tens of thousands of rounds/F.C.G. Cycles to even begin to wear the hammer bores +.001 on a properly assembled and lubricated AR15 or M16 with a forged Lower. The failure point is +.008 from new (.163). I have spoken to countless Military Armorers who have used the USGI Plug Gage and they have consistently told me that they can count on one hand how many lowers have failed the Plug Gage. Even on heavily abused guns it's rare to fail the USGI Plug Gage.
Does anyone not find it odd that these companies who sell ARP's, don't sell the gauges to actaually check for wear but have no problem selling the public a product to "prevent wear". Sorta backwards isn't it?
If there was a problem with U.S. Government M16/M4 Lower Receivers wearing out then ARP's would be an easy fix, but they are not. The lower receivers don't get replaced for wear from pin rotation. They get replaced due to getting ran over, other service related conditions, and people removing the fcg for no reason.
If ARP's were worth a darn then they would have found their way on to the MK18 or some other DoD PIP. If there was a problem a PIP would have been implemented for the M16 variants, M4 variants in service. If there was an improvement to be made in this area then Colt, Knights, FN, or Geissele would have made use of the concept and pushed it.
So in summary.
If you want good Hammer/Trigger Pins use them from Colt, LaRue, SOLGW, Sionics, Geissele, etc, and just keep the firearm generously lubricated.
As long as you don't take the FCG out repeatedly, and lubricate the firearm the bores in the Lower wont wear out.
FYI, Anti Rotation Pins are also NOT to be used with Geissele Triggers. Email Geissele if you want secondary confirmation.
In my experience the only applications where ARP's may be necessary are when using Cassette/Pack type AR Triggers. My experience with Cassette/Pack Triggers has shown me they are unreliable gimmicks as well so the idea is a wash.
If your gun requires the use of ARP's then you have a problem that should be addressed, not covered with a bandaid fix like Anti Rotation Pins.
Users of Blowback 9mm's and .22's report they can't use regular Hammer and Trigger Pins because they break in their blowback AR. If you are breaking Hammer and Trigger Pins then you have a non balanced buffer or recoil system. It means you need to make changes to the gun such as a tungsten carrier weight, shorter barrel, heavier buffer, or a heavier buffer spring.
If you like your Anti Rotation Pins, keep them, but understand that if you are a competitor, they might cost you a match one day. If you hunt with an AR it may cause you to miss a shot. If you use an AR for defense or L.E. work, it may cause your gun to fail when it's called into service.
God Bless Eugene Stoner and Jim Sullivan's Masterpiece. Lead not his disciples to perform blasphemous deeds to their AR.