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  1. #1
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    Default RRA NM trigger/hammer pin size in Mega lower

    This seems like such a basic question, but my search yielded no results, so here goes: I'm on my first build, with a Mega stripped lower on its way from Addax Tactical. My RRA LPK w/ NM trigger arrived a couple of days ago, and I'm just now reading some of the included information.

    The trigger/hammer kit emphasizes being sure that your lower receiver can accommodate RRA's oversize trigger and hammer pins (.156").

    Will the Mega lower have the appropriately sized trigger and hammer pin holes, and, if not, what are my options? I have researched the RRA NM trigger exhaustively, and know that it is used on a plethora of lowers, and this is the first I have seen any mention of a pin sizing problem.

  2. #2

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    Have you tried calling Mega?

  3. #3
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    I measured my Mega's hammer pin, this might help...sorry for the dusty camera lens
    Last edited by redyak3; 03-26-2011 at 05:16 PM.
    Vaporize...

  4. #4
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    Quote Originally Posted by sc191cwp View Post
    Have you tried calling Mega?
    No, not yet, since it's the weekend. I did reach someone at Addax Tactical, and was told they did numerous builds with the RRA NM two-stage trigger with lowers of various manufacturers and had no difficulty with pin size.

    I thought perhaps the opinions of some of the forum members who have had experience in their builds might be more informative as a starting point.

    Most of the information I've been able to get from other internet sources is that the pins are tight, but very doable with light taps of a hammer on a lightly greased pin.
    Last edited by treehugger49; 03-26-2011 at 06:01 PM.

  5. #5
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    Thanks for the pic, redyak3. I guess when my lower arrives I'll see whether .002" makes enough of a difference to keep the RRA pins from being able to be tapped through.

    I still have to think if this were that big of a problem, I would have heard more about it, given the amount of attention the RRA two-stage triggers have been given.

    I'll follow up with my results when the parts come in, and thanks.

    Any more of you with experience with this would be appreciated.

  6. #6
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    OK, for those of you that might share my concerns about the RRA NM trigger/hammer pin size concerns. Here are the responses from (a) the vendor that sold me the kit, (b) Rock River Arms, and (c) Mega Machine, the manufacturer of the lower I will be using.

    (A)The Rock River NM 2stage triggers are designed to work with .1555 pins. The
    pins they come with are .1555 in the kit. The pins will fit in any standard
    lower, but will just need a tiny extra "nudge" to get in. The Rock River
    kits work with .154 (standard pins) but "some" of them experience problems
    apparently with .154, as they were designed to be used with .1555. For
    whatever reason, about 1/3 of them will not work properly with the .154. You
    shouldn't need to modify your lower, tap in the hammer/trigger pins just
    like you would any other LPK. They are just a slight bit tighter than the
    standard pins.

    (B)It means you want to use the .156 pins for a tight fit in the lowers .154
    holes. This will not damage the lower but will give a very tight fit.

    (C)The RRA trigger set does come with the oversized pins, but I would not recommend using the with the tight tolerance of our lower receiver. Even though it WILL fit, needless hammering with a punch will have to be done for installation. My recommendation…. Get the KNS pins in .154 and make it right…

    So...the consensus is that the pins will fit. but may require lubing and some "persuasion" to get them in. Even the manufacturer, although qualifying their response somewhat, says the RRA pins WILL fit, but with some more force than the .154" pin.

    I plan on lubing the holes and pins liberally with Tetra grease and giving them a persuasive tap or two. I'll let you know how the actual install goes. Thanks to those who showed an interest in my predicament.
    fficeffice" />> >

  7. #7
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    Interesting... I think I'd lean toward (C), the response from Mega and get the correct size pins. If you have to "persuade" them in, knocking them out to perhaps upgrade over the RRA might not be so pretty.
    Thanks for the info and good luck
    Vaporize...

  8. #8
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    My $.02 is to use some standard 0.154" pins, not the oversize ones that come with the NM trigger nor the KNS. That's what I do, since I don't want to beat the oversize pins in.
    ARP Mk68 DMR-C Walther Upper & bolt, ARP Vortex, MI T-12, Stag 6.8 lower, Emod, SSA-E, Norgon, SWFA 1-6x24
    ARP 6.8x43 NC Recon Upper & bolt, ARP Vortex, MI SS-12, Stag 6.8 lower, Emod, SSA-E, Norgon, PA 2.5X Compact

  9. #9
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    My reluctance to use .154" pins is based on my vendor's experience reflecting a relatively high (33%) rate of trigger problems with that size.

    I don't anticipate any trigger upgrades going forward, but I would be locked in to using the oversize pins in any future changes once having installed the stock RRA kit, and I'm OK with that.

    The KNS pins come highly recommended, but even their literature emphasizes the need to use their .1555" pins with the RRA NM trigger.

    Once my lower arrives, I'll do a careful evaluation and let you know how things turn out.

  10. #10
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    I guess that depends who you listen to. Mr. Giessele, owner/inventor of SSA, DMR, etc. says not to use KNS pins because he has found them to be soft. The pins that come with his non-adjustable triggers will fit into the receiver holes without any force.
    ARP Mk68 DMR-C Walther Upper & bolt, ARP Vortex, MI T-12, Stag 6.8 lower, Emod, SSA-E, Norgon, SWFA 1-6x24
    ARP 6.8x43 NC Recon Upper & bolt, ARP Vortex, MI SS-12, Stag 6.8 lower, Emod, SSA-E, Norgon, PA 2.5X Compact


 

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