I am building my first AR15. I have this problem.....

When I installed my Timney 667S trigger, I used the KNS .154 standard Stainless Pins. I noticed that when I turned the gun sideways, the pins freely fall out when the hammer is locked back.

Should I have purchased the .155 pins desinged for a match trigger?

Does the smith M&P 15 lower receiver accomodate the .155 pins to stop the pins from walking?

Use the same pins that were used with the original trigger. There are two set screws in the Timney trigger assembly that need to be tightened down to stop the pins from walking out. Read the directions that came with the trigger. It takes about 5 minutes to get everything tightened down. That will cure the problem.

Here's a You Tube video that may help.

http://www.youtube.com/watch?v=8VkbUeoPk1A

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gunfighter48
NRA Life Member