Picatinny rail weirdness

VH96

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Dec 6, 2020
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I have some weird things going on with my TRG and the contessa pic rail. Mounted it about 1.5 years ago with screws and blue loctite. For some time, after shooting the rifle hot some how loctite seeped into the chamber. Usually just whiped everything off and went on. A few days ago it happened again after a long time and decided that I would clean out all of the loctite and remount everything. After doing so, my zero shifted 0.2mrad up and 1mrad left at 100 meters. Was kinda surprised about the amount of windage shift. My ocd kicked in and redid everything. This time my elevation shift went back up to normal, but windage shifted again 1mrad left.

Both times shot a group at 100 and 300 meters, and the rifle holds still an amazing group and its zero and there is no weird alignment issues, ie no windage shift at 300m compared to 100m.

Im just super weirded out about the amount of windage shift and especially since it shifted 1mrad left both times so it has shifted a total of 2mrad left from original mounting. Is this in the normal parameters? Everytime mounted the rail with the first screw infront, and the rear most screw in the back to align the rail, and proceed to tighten the rest.
 

Mike Casselton

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    Uh, you know you only need one drop per screw...

    The bottle has enough in it for multiple uses. Sounds like you used the entire bottle.
     

    ma smith

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    story doesn't add up, loctite only sets in airtight environments and its heat-defeated by via embrittlement.

    that being said, PIC rails not being in spec are annoying and I am empathetic to OP's predicament trouble shooting zero shifts.
     

    308pirate

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    story doesn't add up, loctite only sets in airtight environments and its heat-defeated by via embrittlement.

    that being said, PIC rails not being in spec are annoying and I am empathetic to OP's predicament trouble shooting zero shifts.

    This

    @VH96 your theory that thread locker melted and ran off somewhere is bullshit. Find another reason for your poor workmanship.
     
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    VH96

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    story doesn't add up, loctite only sets in airtight environments and its heat-defeated by via embrittlement.

    that being said, PIC rails not being in spec are annoying and I am empathetic to OP's predicament trouble shooting zero shifts.
    Yeah, well I cant didnt have any clue what else it could have been, since it was a blue liquid, so blue loctite was the only thing I could think of.

    I never had a zero issue with the rail installed, only came across this "issue" after removing the rail the first time. And now, there is no issue (minimal testing though) with the rail re installed, the amount of windage shift just surprised me. And more so that once re installing again, it shifted the same amount the same direction again. Assumed that the re install would bring the windage zeroshift back abit. Still held zero after rezeroing and didnt affect max elevation travel
     

    VH96

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    This

    @VH96 your theory that thread locker melted and ran off somewhere is bullshit. Find another reason for your poor workmanship.
    Well can you tell me of a blue liquid sako uses when they assemble their trg in the factory? Dont know why you have to be an asshole about this.
     
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    308pirate

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    I never had a zero issue with the rail installed, only came across this "issue" after removing the rail the first time. And now, there is no issue (minimal testing though) with the rail re installed, the amount of windage shift just surprised me. And more so that once re installing again, it shifted the same amount the same direction again. Assumed that the re install would bring the windage zeroshift back abit. Still held zero after rezeroing and didnt affect max elevation travel

    Jesus Christ..........

    These are mass produced parts with variation in dimensions even within spec. Of course you're going to have a zero shift when you disassemble and then re-assemble.
     
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    VH96

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    when you glue a pic rail you need proper adhesive,like epoxy, not threadlocker.
    The idea behind using loctite was just to give a tiny amount of added support. The rail has 6 screws and two recoil lugs, didnt want a permanent bond to keep options open, ie testing a direct mount to the trg dovetail
     

    VH96

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    Never mind, didnt know sh was this toxic. But what can you expect from a bunch of Mericans boasting their ego on the internet 🤣 pity the people who are getting into shooting who seek any advice from this forum
     

    spife7980

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    Never mind, didnt know sh was this toxic. But what can you expect from a bunch of Mericans boasting their ego on the internet 🤣 pity the people who are getting into shooting who seek any advice from this forum
    Oh, we pity you alright.
    I Pity The Fool GIFs | Tenor
     

    308pirate

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    The idea behind using loctite was just to give a tiny amount of added support.

    You idiot, thread locker is not a liquid shim. Amazingly, Loctite (and Henkel its parent company) makes one and two part epoxies that you could have used to successfully bed the base to the receiver.

    This has nothing to do with "getting into shooting" and everything to do with you having zero common sense. IDK maybe you have an office job all your life and have never used tools to assemble anything before.

    Don't you understand why people are laughing at you?
     

    VH96

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    You idiot, thread locker is not a liquid shim. Amazingly, Loctite (and Henkel its parent company) makes one and two part epoxies that you could have used to successfully bed the base to the receiver.

    This has nothing to do with "getting into shooting" and everything to do with you having zero common sense. IDK maybe you have an office job all your life and have never used tools to assemble anything before.

    Don't you understand why people are laughing at you?
    Lets try to have an actual conversation: Im used to the accuracy of my spuhr mount, which I never have to rezero my scope when I use the same setup on my 22lr. Every time I remount it to my rifle its dead on. This was the first time I ever took a pic rail off and remounted it, so how can I know how much zero shift to expect after remounting?

    And the first mounting was succesfull, there was nothing wrong with it. The only thing prompting me to remove it and clean up the action and base was this blue gooey liquid on my case after firing it. Next cartridge I chambered and pulled out and it had the same thing. Since you have so much knowledge, can you please use it and explain what the substance could be if not loctite? The only reason I came to the conclusion that it could be loctite is thats the only blue liquid I know that has ever touched the rifle.

    Maybe my use of loctite was wrong, but when removing I did have to use some force to pull the rail off so it did do something. I know there are epoxies, but like I said I didnt want to make a "permanent" bond.

    Like I said after test firing I didnt find any windage shift from 100 to 300 meters which a crooked base should cause. So I guess everything is still aligned correctly.

    Maybe it would have been easier to just ask has any one ever tested how much zeroshift you get when removing and re-installing a picatinny scope base, since that is what I really was curious about.
    And if you must know, I work at the most prestigeous gun store in our country.
     
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    spife7980

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    And if you must know, I work at the most prestigeous gun store in our country.
    Youre new but theres a running joke that people selling guns in a store dont know shit about em.

    Hard to say what the blue stuff is in your chamber without a pic to see for ourselves... but it shouldnt be loctite. If it is loctite in your chamber you used loctite seriously wrong. Thats all anyone is saying.

    We cant say whats a typical amount of shift would be with your personal set up but 1 mil isnt a whole lot nor very surprising after a full breakdown. Especially if the base was floating on a sea of loctite.
     

    VH96

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    Youre new but theres a running joke that people selling guns in a store dont know shit about em.

    Hard to say what the blue stuff is in your chamber without a pic to see for ourselves... but it shouldnt be loctite. If it is loctite in your chamber you used loctite seriously wrong. Thats all anyone is saying.

    We cant say whats a typical amount of shift would be with your personal set up but 1 mil isnt a whole lot nor very surprising after a full breakdown. Especially if the base was floating on a sea of loctite.
    Yes Im new and that doesnt surprise me 😄 my best shooting merrit is hitting 1126 meters at a prs comp with a 308, before that the furthest I could go and shoot was 650 meters, so I guess I did something right. The load was handloaded 175 scenar-l at approx 808 ms mv going subsonic at about 950 meters.

    Thanks for the helpful response. For me the biggest thing weirding me out was that when I re installed the re install, it shifted left 1mrad again, so basically 0 elevation shift and 2mrad shift left from the original install 1.5 years ago. After whiping the cartridge the substance seemed very similar to loctite. But I cant really figure out where it could have hidden for 1.5 years without curing and having a hole to get into the chamber. Every screw hole had remnants of brittle loctite after removal like expected.

    I have twice done a "full" break down with removing the scope mount, and barreled action from the bedding block for a clean and after reassembling didnt have any zero shift at all. But as mentioned, never have I before removed a pic rail after it has been mounted.

    But since I didnt have any weird impact shift at range, I guess Ill just leave it be and trouble shoot again if I get weird windage shift or if the zero starts shifting.
     

    DudeBro

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    Mar 17, 2019
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    And if you must know, I work at the most prestigeous gun store in our country.
    LRI? GA Precision? Altus? Preece Precision? Stuteville? I'm a bit new to this precision game too, so I'm not sure what the most prestigious store is.
     

    DudeBro

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    Mar 17, 2019
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    I have some weird things going on with my TRG and the contessa pic rail. Mounted it about 1.5 years ago with screws and blue loctite. For some time, after shooting the rifle hot some how loctite seeped into the chamber. Usually just whiped everything off and went on. A few days ago it happened again after a long time and decided that I would clean out all of the loctite and remount everything. After doing so, my zero shifted 0.2mrad up and 1mrad left at 100 meters. Was kinda surprised about the amount of windage shift. My ocd kicked in and redid everything. This time my elevation shift went back up to normal, but windage shifted again 1mrad left.

    Both times shot a group at 100 and 300 meters, and the rifle holds still an amazing group and its zero and there is no weird alignment issues, ie no windage shift at 300m compared to 100m.

    Im just super weirded out about the amount of windage shift and especially since it shifted 1mrad left both times so it has shifted a total of 2mrad left from original mounting. Is this in the normal parameters? Everytime mounted the rail with the first screw infront, and the rear most screw in the back to align the rail, and proceed to tighten the rest.
    You're stacking tolerances by adding a pic rail to the TRG then rings on top of that. Your OCD might benefit by going with spuhr mount or sportmatch rings (both clamp directly to the factory dovetail).


     

    VH96

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    You're stacking tolerances by adding a pic rail to the TRG then rings on top of that. Your OCD might benefit by going with spuhr mount or sportmatch rings (both clamp directly to the factory dovetail).


    I have a spuhr mount for the picatinny rail. I did think about it when I got the trg, but went with picatinny since all of my rifles were pic so swapping scopes between them was a factor.
     

    ma smith

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    Never mind, didnt know sh was this toxic. But what can you expect from a bunch of Mericans boasting their ego on the internet 🤣 pity the people who are getting into shooting who seek any advice from this forum
    In Finland
    Sako is a great company and both Sako and Tikka recommend bedding PIC rails.
    As does Nighforce (USA) the last time i talked to them about it.

    The recipe for global peace and harmony :ROFLMAO:is as follows IMHO:

    (1) RTFM on a bottle of locktite 243; and then
    (2) go buy a different bedding adhesive for your PIC rail.

    Don't forget that "acceptable" tolerances on NATO-spec PIC Rail are notoriously shit,
    so a "within nato-spec" rail can still be all over the place.

    Contessa is a quality product, I have one of their rails and it has good repeatabilty.


    Good luck!
     

    DudeBro

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    I have a spuhr mount for the picatinny rail. I did think about it when I got the trg, but went with picatinny since all of my rifles were pic so swapping scopes between them was a factor.
    Understand why you want the versatility of a pic mount. I'm just pointing out that if your OCD is concerned about modest shifts during complete disassembly and reassembly, then you may be better served by removing one component in the tolerance stack.
     

    Part Timer

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    And the first mounting was succesfull, there was nothing wrong with it. The only thing prompting me to remove it and clean up the action and base was this blue gooey liquid on my case after firing it. Next cartridge I chambered and pulled out and it had the same thing. Since you have so much knowledge, can you please use it and explain what the substance could be if not loctite? The only reason I came to the conclusion that it could be loctite is thats the only blue liquid I know that has ever touched the rifle.
    Blue gooey liquid... You didn't happen to clean the rifle prior to this happening, did you? Possibly just didn't clean out the chamber well enough and had leftover residue on the cases? Doesn't explain the POI shift, but might be the source of your slime.
     

    DudeBro

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    You didn't happen to clean the rifle prior to this happening, did you? Possibly just didn't clean out the chamber well enough and had leftover residue on the cases? Doesn't explain the POI shift, but might be the source of your slime.
    Good catch. Many solvents turn blue after reacting w/ copper.
     
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    VH96

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    Understand why you want the versatility of a pic mount. I'm just pointing out that if your OCD is concerned about modest shifts during complete disassembly and reassembly, then you may be better served by removing one component in the tolerance stack.
    I see your point, but removing the pic rail isnt part of a normal procedure for me so once I make a more thorough test that everything is still aligned Im probably going to make a more permanent bond.

    And I rarely clean, and usually only clean with oil. Only once have I cleaned with any copper solvent (after about 1500 rounds) and I had the same slime prior to this and now. Basically the "slime" hasnt really been an issue. If I see it I have just cleaned the chamber thoroughly and continued on.
     

    VH96

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    I think I found the reason why the zero shifts after reinstalling the mount. The mounting is solid enough that it holds zero after being mounted, but seems like there is enough play in the system that enables the rail not to align the same way every time. The air gaps are in a location where sako has machined holes for the recoil lugs
    IMG_20220611_175437.jpg
     

    Ledzep

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    So your POI shifts from a complete removal and replacement by ~1" at 100yd?

    100yd * 36"/yd = 3600 inches

    1/3600 * 7" (length of rail, approx.) = .00194"

    So front to back, the rail shifts orientation in the order of a thou or two on the ends by removing and replacing it. Shocking!
     
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    Baron23

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    Yes Im new and that doesnt surprise me 😄 my best shooting merrit is hitting 1126 meters at a prs comp with a 308, before that the furthest I could go and shoot was 650 meters, so I guess I did something right. The load was handloaded 175 scenar-l at approx 808 ms mv going subsonic at about 950 meters.

    Thanks for the helpful response. For me the biggest thing weirding me out was that when I re installed the re install, it shifted left 1mrad again, so basically 0 elevation shift and 2mrad shift left from the original install 1.5 years ago. After whiping the cartridge the substance seemed very similar to loctite. But I cant really figure out where it could have hidden for 1.5 years without curing and having a hole to get into the chamber. Every screw hole had remnants of brittle loctite after removal like expected.

    I have twice done a "full" break down with removing the scope mount, and barreled action from the bedding block for a clean and after reassembling didnt have any zero shift at all. But as mentioned, never have I before removed a pic rail after it has been mounted.

    But since I didnt have any weird impact shift at range, I guess Ill just leave it be and trouble shoot again if I get weird windage shift or if the zero starts shifting.
    Ah....this may be way off base...but do you use a copper remover to clean with and perhaps the "blue" liquid is copper in solvent solution that you let run back down into your action....maybe?

    Can't imagine it being loctite still liquid after 1.5 years


    Ooops, never mind....just saw subsequent post. You only clean with copper solvent after 1,500 rounds? Wow
     
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    Baron23

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    You're stacking tolerances by adding a pic rail to the TRG then rings on top of that.
    Well, yeah....but who gives a damn if after install they do NOT move...because they were properly installed. Its part of the purpose of zeroing to account for any tolerance stacking, right.
     

    Ledzep

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    Gotcha, misread the OP thought they were tenths. Regardless that's not out of line unless the parts are tightly dowel pinned together. I'm not intimately familiar with the TRG but it looks like it's just screws holding the rail to the base?

    eta: Put all of the screws on, hand tight, then back them all off 1/4 turn so everything is loose, wiggle the rail and see how much movement there is. If it really bothers you, pick an orientation to bias the rail as you tighten the screws, and alternate the order that you tighten them (like putting heads on a motor) if it really bothers you. As long as it's not moving during firing, it's not really a problem.
     
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    carbonbased

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    OP, when installing you know you need to shove the rings forward until they contact the pic rail, right? Otherwise there’s a chance that recoil will move the rings forward. There’s always some gap.

    When you install a chassis, same thing. Move chassis foreword until it hits the lug. When installing the rail to the top of the rifle, same thing, shove the rail foreword.

    When not tightened, I have had exactly zero pic rail attachments with zero play, back and forth, when placed in the pic rail. I mean, if that was the case you would be lucky to even be able to install the attachment and have to resort to press fit/hammer or freezing the rings before installing.
     
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