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Moderator problem

  • 20-12-2008 12:23PM
    #1
    mcevoyger
    Registered Users, Registered Users 2 Posts: 15 ✭


    Just wondering if anyone can help me with this. I have a sound moderator for my tikka .243. When the moderator id on the rifle it is too long to fit back in the gun slip I have fro it. So when I am finished shooting I take it off. My problem is that when I take it off and put it on again The rifle and the scope are no longer zeroed. I have to zero the scope once again. Is it possible that by doing this I am throwing the bullet off in a different direction every time or am I just imagining things. I have a schmidt and bender 8X56 scope mounted on the rifle so I dont think it is it and th rifle is only one year old. I clean it after every outing. Can you reccomend a moderator that I can leave on the barrell or am I doing something else wrong.

    Thanks


Comments

  • #2
    Tackleberry.
    Registered Users, Registered Users 2 Posts: 1,269 ✭✭✭Tackleberry.


    what mod is it?? if its a T8, is the plastic bung at rear machined to fit your barrel tightly? if not it could be your prob, if its a good fit put it all together(zeroed) as if to go shooting then put a mark (paint or something of your liking) across the mod onto your rifle barrel,now when you take off the mod you should be able to screw it all back together using the mark to line it all up.Everything should be the same as when you last used it, hope this helps, i'd buy a new gun slip myself.


  • #3
    Jonty
    Registered Users, Registered Users 2 Posts: 1,830 ✭✭✭Jonty


    Ideally you should be removing the moderator each time for storage. Moisture in the air mixes with the sediment in the moderator which causes an acid to be formed which will eat the crown on the rifle. Tack is right about "lining" up the moderator. Also, there is no need to over tighten the mod. Finger tight should be fine.


    Is there any burring on the exit hole on the moderator? If there is it could be the fact that the threading job isn't actually true to the bore and the bullet could be glancing off the baffles in the moderator.


    I've a tactical t3 with a t8 mod which I remove before storage and I find no need to rezero each time.


    How big are your groups exactly? Could it just be the case that the first few shots need to settle into an over clean barrel?

    If the bung is too big that its not touching the barrel, make up the distance beteween the barrel and bung with insulation tape.


  • #4
    pm.
    Registered Users, Registered Users 2 Posts: 2,147 ✭✭✭pm.


    i have a T8 on my steyr .243 and i never need to zero when im finished with the rifle i take off the mod and spray oil into it and when i want to use it again simply screw it back on and as the last poster said dont over tighten it


  • #5
    Tackleberry.
    Registered Users, Registered Users 2 Posts: 1,269 ✭✭✭Tackleberry.


    How big are your groups exactly? Could it just be the case that the first few shots need to settle into an over clean barrel?

    ya this also is a good point :i only clean the inside of my barrel at the start of the season and at the end of the season I'd look to stripping the gun down fully, how many rounds are you firing it cant be huge numbers, I'd not fire a hundred rounds in a season.try to not clean inside the barrel as each time you clean it 4 or 5 rounds will be needed to get a tight pattern again,and if your shooting often it will mind itself, but if your leaving it up for a while run a oiled patch true it. Some people might not agree with this but it works well for me, i also shoot a 243 Sako finnlite in stainless,it will handle a harder life... also a tiny i say again tiny bit of copper greese on the thread is a good thing,your mod will never stick,and you can see if it moves with your painted mark.


  • #6
    rogern
    Closed Accounts Posts: 6 ✭rogern


    Had the same prob myself, make sure that the delrin bush at the back of the mod is clearing the barrel by a couple of mills, if it is not have it reamed out by an engineer, until I found out that this was causing my problems I left the bush off until I got it done.

    The other guys are right, do not leave the mod on after shooting, it will eventually bugger up the crown by corrosion.


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  • #7
    ejg
    Registered Users, Registered Users 2 Posts: 807 ✭✭✭ejg


    The plastic in the bushing is only to avoid scratching of the barrel and to keep the dirt out. It is wrong to try and center the mod with the bush and the shoulder of the thread at the same time.. who is going to win ?? shoulder or bush.?? Is it going to depend on torque applied? Why do the "not over barrel" cans work so well??? because they don't have a bush!! So I think the bush should be at least 0.3mm larger than the barrel at that point.
    A quick test, take the bush out and shoot without for a while, but tighten mod well.

    Another point, measure the diameter of the exit, find a metall rod with that diameter and see if a baffle inside is off center and might not let you stick the rod through. This should then be bored out.


    edi


  • #8
    Tackleberry.
    Registered Users, Registered Users 2 Posts: 1,269 ✭✭✭Tackleberry.


    ejg wrote: »
    The plastic in the bushing is only to avoid scratching of the barrel and to keep the dirt out. It is wrong to try and center the mod with the bush and the shoulder of the thread at the same time.. who is going to win ?? shoulder or bush.?? Is it going to depend on torque applied? Why do the "not over barrel" cans work so well??? because they don't have a bush!! So I think the bush should be at least 0.3mm larger than the barrel at that point.
    A quick test, take the bush out and shoot without for a while, but tighten mod well.

    Another point, measure the diameter of the exit, find a metall rod with that diameter and see if a baffle inside is off center and might not let you stick the rod through. This should then be bored out.


    edi

    I think you should read this, it says the bush alignes the mod.http://jacksonrifles.com/zz-silencers/files/t8-t4-manual.pdf


  • #9
    rogern
    Closed Accounts Posts: 6 ✭rogern


    If the thread has been cut properly the mod should spin on freely, there is no need to apply any force to tighten, if you are firing a lot of rounds when zeroing keep ckecking that the mod has not come loose, it should not go out of line even if its loose!

    As GJg said, the bush is not there for alignment, I used mine for over a year without it fitted with no probs.


  • #10
    jwshooter
    Closed Accounts Posts: 4,612 ✭✭✭jwshooter


    rogern wrote: »
    Had the same prob myself, make sure that the delrin bush at the back of the mod is clearing the barrel by a couple of mills, if it is not have it reamed out by an engineer, until I found out that this was causing my problems I left the bush off until I got it done.

    The other guys are right, do not leave the mod on after shooting, it will eventually bugger up the crown by corrosion.

    roger, i all ways keep the bust as tight as i can get .i have never heard of anyone keeping in a couple of mill s off the barrel . i would think this would be dangerous as it would leave movement in the t8 and can it not see it doing the threads on the barrel any good long term


  • #11
    rogern
    Closed Accounts Posts: 6 ✭rogern


    jwshooter wrote: »
    roger, i all ways keep the bust as tight as i can get .i have never heard of anyone keeping in a couple of mill s off the barrel . i would think this would be dangerous as it would leave movement in the t8 and can it not see it doing the threads on the barrel any good long term

    I understand your comment jw, but Jacksons (the T8 suppliers) reckon that if the thread is cut professionally there should not be any play even if it not tightened, another thought is that nothing should be touching the barrel as it can upset the harmonics.


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  • #12
    ejg
    Registered Users, Registered Users 2 Posts: 807 ✭✭✭ejg


    Tackleberry. wrote: »
    I think you should read this, it says the bush alignes the mod.http://jacksonrifles.com/zz-silencers/files/t8-t4-manual.pdf

    Well, maybe we should just rewrite every engineering book.
    do not tighten screw... bla bla next is "do not tighten wheel nut..."

    it is simply wrong. One cannot go out into the field hit the mod off things, huge vibration and temperatur changes of the moderator while firing shots and expect a loosely tightened moderator to stay in place. It is a safety hazard to do so. And imagine what the harmonics in a barrel do when firing a half loose moderator, it creates a half dampened vibration??? one will never achieve consistant day to day accuracy with that.

    If the thread on the barrel is cut correctly which it just has to be and the moderator is in order then the centering should be done by the thread shoulder on the barrel. The reflex is not longer forward of the barrel than other moderators.

    I don't mean tighten a moderator by spanner, but at least as tight as one can with one hand. Leaves you to open it with two hands.

    edi


  • #13
    Tackleberry.
    Registered Users, Registered Users 2 Posts: 1,269 ✭✭✭Tackleberry.


    TAKEN FROM JACKSONS RIFLES:
    NOTE #4

    Fitting Instructions
    Standard muzzle threads are ISO M14x1, M15x1, M17x1 or M19x1 with spigot. Thread is selected to suit the calibre and barrel diameter of the rifle. Reflex Suppressors can be supplied with practically any other thread on request.
    1. Remove the front sight.
    2. Fasten the barrel in a 3- or 4-jaw lathe chuck at the position of the back of the suppressor (usually 210 mm from the muzzle) with the muzzle supported on a rotating centre.
    3. Make a metric thread with a relief cut and a cylindrical “spigot” between the thread and the shoulder (see drawing, right). IMPORTANT: for threads other than listed above there is no "spigot", so the dimension from muzzle crown to shoulder is 11.5 mm instead of 30.0 mm (except T8SSR - see special drawing). If in doubt, please ask!
    4. The thread should be slack enough to allow the suppressor to freely align itself by the rear bushing (see note “Muzzle Thread Tolerance” below).
    5. After thread cutting, check the muzzle and re-crown if necessary.
    6. Unscrew the barrel bushing from the back of the suppressor.
    7. Screw the suppressor on the muzzle without the barrel bushing.
    8. Measure the diameter of the barrel at the back of the suppressor (typically 210 mm from the muzzle).
    9. Enlarge the barrel bushing hole in a lathe to the measured barrel diameter + 0.02 mm. A threaded tube for holding the bushing in the lathe chuck is recommended.


  • #14
    rogern
    Closed Accounts Posts: 6 ✭rogern


    Hey edi, I.m not trying to cause an arguement, if the thread is cut properly the mod should spin on, but it should be in line with the bore all the way down the thread so if it did come loose there would not be a danger problem.

    9. Enlarge the barrel bushing hole in a lathe to the measured barrel diameter + 0.02 mm. A threaded tube for holding the bushing in the lathe chuck is recommended.

    The above paragraph confirms my point, the bush shoul NOT touch the barrel.

    Regards


  • #15
    clivej
    Registered Users, Registered Users 2 Posts: 7,132 ✭✭✭clivej


    rogern wrote: »
    Hey edi, I.m not trying to cause an arguement, if the thread is cut properly the mod should spin on, but it should be in line with the bore all the way down the thread so if it did come loose there would not be a danger problem.

    9. Enlarge the barrel bushing hole in a lathe to the measured barrel diameter + 0.02 mm. A threaded tube for holding the bushing in the lathe chuck is recommended.

    The above paragraph confirms my point, the bush shoul NOT touch the barrel.

    Regards

    BUT it must support the mod with the rear bushing on the barrel.
    Just how big do you think 0.02mm is. I have seen this done by a gunsmith on his lathe and it's not a tight fit but a very, very close fit.
    I read on the Jackson site that the bushing will support the mod if it becomes loose on it 's threads.
    QUOTE "the mod is supported in 2 places" or words like that.


  • #16
    ejg
    Registered Users, Registered Users 2 Posts: 807 ✭✭✭ejg


    rogern wrote: »
    Hey edi, I.m not trying to cause an arguement, if the thread is cut properly the mod should spin on, but it should be in line with the bore all the way down the thread so if it did come loose there would not be a danger problem.

    9. Enlarge the barrel bushing hole in a lathe to the measured barrel diameter + 0.02 mm. A threaded tube for holding the bushing in the lathe chuck is recommended.

    The above paragraph confirms my point, the bush shoul NOT touch the barrel.

    Regards

    Rogern, no argument.
    Can't really understand why Jackson would write something like this. I'll actually ask them at the IWA. (especially the bit about not tightening)
    Everyone can do as they like, as long as no one gets hurt.

    People seem to have much more problems with the over barrel type moderators with back bush than people with front mounted moderators.
    Wonder why? I've had both and also had problems with the over barrel type a while back. I discussed this with Pete Lincoln of Roedale precision in Germany who said they fit moderators with plenty play in the bush to avoid touching.

    edi


  • #17
    jwshooter
    Closed Accounts Posts: 4,612 ✭✭✭jwshooter


    i was chatting to dennis today of jackson rifles ,the bush is not meant to touch the barrel it should be .002 tou of a inch off the barrel ,or slide slightly past the point it meets when fixed to the mod .


  • #18
    Half-cocked
    Registered Users, Registered Users 2 Posts: 4,319 ✭✭✭Half-cocked


    I've fitted a lot of suppressors over the years and also re-fitted botched ones fitted by people who didn't know what they were doing. The most common cause of lost zero every time the suppressor is taken off/on is a bad seating against the shoulder at the base of the threaded section. If the undercut is not a smaller diameter than the core diameter of the thread, you can't get a good, positive seating. You should feel your suppressor 'lock' firmly into position with little or no ability to further tighten it (unless you insist on swinging out of it with excessive torgue!). Also, keep the shoulder on the barrel and suppressor free of dirt etc. Try screwing it on and making a couple of alignment marks on the barrel and suppressor. Take it on and off a few times and if the marks don't line up each time you have a sloppy seating. Hope this helps.


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