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Home > AR-15 / M16 & Stuff

M16 / AR15 Auto Sear Trip

Part Number AR15ST
review 11 Review(s)
M16 / AR15 Auto Sear Trip
AR15 Auto Sear Trip (To be used with your Bolt Carrier)
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Retail Price:  $37.95
Your Savings:  $8.64
Your Price:   $37.95
On sale: 
On Sale
This is an Auto Sear Trip designed to be used on  AR15 Bolt Carriers. It is made of solid brass so it adds some mass to the bolt carrier assembly. On the M-16 bolt carrier there is approximatly 1.5 inches of steel on the bottom rear of the carrier (see pictures). This allows the bolt carrier to trip the auto-sear when the bolt is within .050 of fully closed. AR-15 bolt carriers have had this area milled short or on some carriers completely removed from the back of the bolt carrier. The Select Fire Auto Sear Trip installs in all AR-15 bolt carriers and turns it into an M16 carrier that can trip an auto-sear when needed. Why spend 100 on an independent M16 bolt carrier when this little unit can be installed in seconds and removed when not needed on all AR-15 Bolt Carriers.____________________________ The body is made from Sold Brass Rod with a 1050 steel trip tang. The unit installs with 2 set screws allowing it to be fully adjustable for correct bolt/auto sear trip timing._______________________ Auto Sear Trip is sold with all necessary hardware to include the hex wrench for installation and removal. All standard AR15 bolt carriers have a 5/8 (.625) hole through the center. the trip body is .615 - .622. in some cases a little bit of filing will create a perfect fit on undersized holes by a few thousandths. NOTE: You may need to perform a little filing and fitting due to some Chinese Bolt Carrier manufactures drilling the bolt carrier with a Metric clearance hole. 
Customer Reviews
Rating ?
Great product, high quality, works perfect!! Much cheaper than buying an m16 bolt. Thanks!!
  Did you find this helpful?    10 of 11 Found Helpful
Reviewed by:  from Oklahoma. - 4/24/2013
Rating Buss Owner
Purchased this item for the sole purpose of adding mass / weight to the bolt carrier. There was a bit of work needed to fit the unit but that is good since it makes for a smug fit that is less likely to shift during firing. Not used as a sear trip for my application, but for adding weight to my bolt it is a great product.
  Did you find this helpful?    6 of 8 Found Helpful
Reviewed by:  from Florida. - 5/21/2014
Rating trip
Great product. Well built. would be nice to have a third hole for additional hold
  Did you find this helpful?    4 of 5 Found Helpful
Reviewed by:  from va. - 9/10/2015
Rating Ar
Great product. Well built. Good fit no adjustments a+++++
  Did you find this helpful?    3 of 3 Found Helpful
Reviewed by:  from Clermont Ga. - 8/9/2015
Rating Sargent
Outstanding quality...good finish...easy install...great for adding mass to the bolt carrier awesome addition to anyone who wants an extra kick on their AR 15... Thank you so much Select Fire...hoorah!!!
  Did you find this helpful?    3 of 3 Found Helpful
Reviewed by:  from Texas. - 3/26/2015
Rating Mr.
fits perfectly, no extra Fitting needed, makes an ar15 carrier an m4 carrier in less than a Minute
  Did you find this helpful?    2 of 3 Found Helpful
Reviewed by:  from austria. - 2/15/2018
Rating Quality Product
Totally amazed at the promptness of shipping. This is a quality made product which is easily installed or removed from your carrier. Although it adapts the AR-15 carrier to act like an M-16 carrier, it also adds weight to the bolt carrier assembly.
  Did you find this helpful?    2 of 2 Found Helpful
Reviewed by:  from Glens Falls, NY. - 9/26/2015
Rating Great idea but cant get to work
Its a great product and great idea but mine just wont work. Its for an original M&P-15X model. The semi BCG is not as short as pictured on this site but not full length so I can only use one set screw point of teh two when properly in place. Would not fit so I filed to fit which took some time and tightened to 40 inch pounds and it still moves after just dry firing a few times.
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Reviewed by:  from GA. - 6/4/2021
Rating Great product
Fine product
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Reviewed by:  from Salem. - 4/19/2021
Rating user
product works as promised good buy
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Reviewed by:  from usa. - 5/23/2019
Rating Quality Product
I received the item three days from the time of order. The product took 20 minutes to install and time. I dimpled the inside of the carrier where the set screws where to go and secured them with thread locker. Performs Great.
  Did you find this helpful?   
Reviewed by: (Verified Buyer)  from Texas. - 2/15/2014
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