Suppressors  surefire 308 question

jcwarrior87

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For all of you out there with surefire 308 suppressors I would love to know what your difference in zero is for with and with out it on. I zeroed mine at 100 with the can and with out I am about 4 inches low and 1 inch to the left.

I am shooting a trued 700 in 308.
 

Chucky

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Re: surefire 308 question

Is this repeatable? I have never had that much of a shift but with different lighter longer barrels it might be a possibility. I have heard of it on piston guns but have never seen that much of a shift myself on a heavy barrel bolt gun. Next time you shoot it grab the suppressor in one hand the lock ring with the other and twist both at the same time to make sure it locks onto the last notch on the lock ring. I have heard of a larger shift if the suppressor is not on the last notch. My email is in my signature line below and if you have any follow up questions please don't hesitate to ask me. The largest shift on any of the 14 or so suppressed weapons I have is about 2.5MOA at 100 yards.
 

jcwarrior87

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Re: surefire 308 question

rifle is a trued pss that has been cut to 20" and I can only get the lock ring to tighten down to the first tooth until it is tight.
 

Pusher591

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    Re: surefire 308 question

    I can't tell you the solution but you definitely have a problem because I have never heard of a SF having that kind of shift, if any for that matter.

    If you can only lock it down on the first notch, did the smith who installed the mount leave enough for the shoulder of the can to fit over? I ask this assuming you are using a 762SS(reflex) can.
     

    jcwarrior87

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    Re: surefire 308 question

    yes that is the can I am using. Maybe I need to have my smith shave a little bit more off the barrel
     

    HPLLC

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    Re: surefire 308 question

    First thing to check would be mount tightness. Some Surefire end users mention that their cans didn't shoot that hot until they went gorilla tight on the locking ring to get one more ratchet tooth to engage.

    If the mount were very slightly loose- that shift would be somewhat consistent with how it should look- down and possibly slightly to the side opposite the eccentric engagement surface of the locking ring that puts tension on the muzzle mount.

    -----------------------------------------------


    If that doesn't isolate the problem, maybe get a different shop to thread it. Like ADCO.

    4MOA isn't huge- you might be able to fix it by trueing the thread shoulder and barrel face to the bore (this is if there is appropriate tolerance of fit between the threads). I say both because some mounts index on one and some the other and I don't know how the Surefire mount is engineered.

    Since you're at 20" and probably would like to keep it that way, make sure the service provider you use is competent and able to properly fixture the barrel in order to do it right the first time.
     

    lowlight

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    Re: surefire 308 question

    There were some bad brakes from SF running around, my Gladius has one and it creates a bigger shift than it should. Two rifles from competent smiths with the same brake causes the same large shift. My GAP10 with the new brake doesn't and it works fine. Very minimal shift.

    It's marked right but when you use it, it causes a pretty sizable shift. About what you are seeing.

    The answer to is to replace the brake with the right one if you happen to have one like I have... a picture might help. As well do you have the channel behind the brake cut into the barrel ? Again a picture helps...
     

    jcwarrior87

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    Re: surefire 308 question

    I am going to run it out to the smith today we are going to check the clearance of the locking ring, I have total faith in my smith, every thing he build shoots well. When I tighten it on it is always tight. I am hopping to have him look at it and make any changes today, because I am shooting this afternoon, SO I hopefully can re test it.
     

    M21tactical

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    Re: surefire 308 question

    Mine shoots about 1" low and 1/2" to the left and it is repeatable. Good luck with the smith today and hope you find the problem.
     

    Whiskey 2-1

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    Re: surefire 308 question

    2 different surefire 308 cans on 3 different rifles (so 6 combinations) and all had the same shift- 0.1-0.2 mil to 6 oclock. They have all been very repeatable. All were barreled by GAP.
     

    Pusher591

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    Re: surefire 308 question

    I shot a 20 round group today. First 10 were unsuppressed, next five were SF can #1, next five rounds was SF can #2.

    All 20 rounds were in a GAPEING 3/4" hole except for 1 round I pulled low right. I have a pic but no way to post. I can email it to you if you want to see how it looks.

    Hope yours gets worked out cause I think my groups actually tightened up with the can
    smile.gif
     

    patriotunknown

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    Re: surefire 308 question

    i just started shooting my nm m1a with a sf762k on it. has about a six inch shift low. i can take it off and put it back on and the shift is the same. its a 22" nm barrel heavy barrel but m1a's are thin compared to the ar10 barrels of today towards the muzzle end. this surprised me because the other ar10 style guns i have shot (both 18 and 20") had a minimal if any shift. both sf cans repeatably return to zero unlike some cans which i will not mention that must be indexed (what a stupid idea: indexing that front towards enemy crap)

    side note... i swear my 556k has no shift on a 10.5" standard barrel.
     

    jcwarrior87

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    Re: surefire 308 question

    Ok so it looks like there was a bind on the barrel, the smith cut it back and it doesn't touch any more. I took it out and shot one 5 round group (suppressed, non suppressed, suppressed, non suppressed, suppressed. There are two groups that are about 1.5 moa(shot at 100yrds) apart. Is it fixed or can I get it closer. the can still will only lock about 3 clicks on, and I can't get it any tighter( i turn a screw driver all days so it is TIGHT) Any thoughts guys.

    If you guys need picture to help I need to know what you want to see.
     

    Elnino31

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    Re: surefire 308 question

    Threads that are not concentric to the bore can have an effect on the POI shift. Something that ADCO can check, but a competent machinist can do the same.

    If you don't have a buddy who is a machinist.... get one.
    Buddies that are bartenders or golf pros are nice too.
    grin.gif
     

    jcwarrior87

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    Re: surefire 308 question

    The smith that built this rifle is a very good one. I have no reason to believe that it is exactly straight. Plus he is also a good friend of mine also, so I trust him.

    any one have any Ideas?
     

    Jackalope33B

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    Re: surefire 308 question

    Second opinion. Go to another smith

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jcwarrior87</div><div class="ubbcode-body">The smith that built this rifle is a very good one. I have no reason to believe that it is exactly straight. Plus he is also a good friend of mine also, so I trust him.

    any one have any Ideas? </div></div>