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Trigger pin size


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So google didn't make things clear for me. I just started shooting a gas gun series and I am trying to take parts and use them I currently have to supplement the cost of another rifle. I have a jp roller trigger with .156 small pin screws. I get you can use 5.56 triggers in a 7.62 gun but sometimes they have problems with military style ammo (primers). How true is this? What ar-10 lowers run small pin holes? I am unclear how common this is. Am I foolish to try and make this work?

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41 minutes ago, RickedRoss said:

 I have a jp roller trigger with .156 small pin screws.

It's a 0.154" pin size. Not 0.156"   You'd never get a 0.156" pin into a lower receiver without pounding the shiit out of it.

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  If you have issues setting off MilSpec Primers , there are several companies that make stronger Hammer Springs to remedy the issue ( the one piece Modular FCG's may be different ) . Most FCG's don't have the issue , I have & I'm sure some here have more , but I have probably a half doz. different FCG's I've tried in 308 AR's & have not had one issue with setting off primers on Milspec ammo .

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I can say for sure from experience timney(ar15 version) and velocity have issues with hard 308 primers. 


I had an RRA trigger that would hit the bottom of the carrier and lock the gun up. Just had to remove a small amount of materiel to fix it but it happens.  

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13 hours ago, RickedRoss said:

Thanks for clearing that up. 98Z5V the box says .156.


I'd measure those things out, and see what's up  - you'll have one hell of a time pounding those into a lower receiver.  I kid you not. 

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2 hours ago, DNP said:

All I'm saying is there are companies making them that size on purpose. I guess you'll need a BFH for the process

 Some manufacturers make loose Pin Holes or they get loose with wear from walking . Usually ya just get over sized pins , but the whole FCG , never seen it till now , could also be someones idea of a proprietary components , ya never know .

Edited by survivalshop
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  • 3 years later...
7 minutes ago, Viper said:

Isn’t 0.172 the spec for the large Colt pins? 

sorry, just noticed the age of this post. 

No, 0.169" is the Colt Large Pin receivers.  They're the only ones that ever did this, too.

Trust Bill Geissele for this information.


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  • 11 months later...

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