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Thread: Moderator-Barrel clearance?

  1. #1

    Moderator-Barrel clearance?

    I am getting a T8 Moderator (Pre-Owned) and would like to put a question to "those in the know".
    The moderator I am collecting today has been used on a heavy barreled rifle so I am almost certainly goint to have to change the delrin (screw in) washer on the back of the moderator to one that suits my rifle which has a sporter barrel. My rifle came with a delrin washer which (I am told) is for a T8 moderator but when I slide it down the barrel to where it would normally sit with the moderator in place it seems to have about 1mm of clearance all the way round between the barrel and the delrin washer.
    Is this right/acceptable or can anyone tell me what the acceptable/recommended clearance should be between the delrin washer and the barrel please.

    Thanks in advance.



  2. #2
    You can just wrap some tape round the barrel to take up the gap as a short term fix.
    I hate to see a barrel scarred by moderator bushes.
    I get my rear nylon bushes cut big enough to allow a couple of layers of tape to protect the barrel surface from being damaged by the bush. The bush can be a nice snug fit over the tape - easily adjust the fit by adding or removing tape. If the tape gets worn I just replace it - Works for me.

    Ian

  3. #3
    Quote Originally Posted by Yorric View Post
    You can just wrap some tape round the barrel to take up the gap as a short term fix.
    I hate to see a barrel scarred by moderator bushes.
    I get my rear nylon bushes cut big enough to allow a couple of layers of tape to protect the barrel surface from being damaged by the bush. The bush can be a nice snug fit over the tape - easily adjust the fit by adding or removing tape. If the tape gets worn I just replace it - Works for me.

    Ian
    Thanks for that Ian, very useful especially as you may well have saved me some money by not having to send off and buy a new delrin washer.



  4. #4
    Can someone explain why there needs to be contact of any sort? A standard moderator doesn't need the extra support, is it just to keep crud out?
    Thanks
    GH

  5. #5
    Quote Originally Posted by Gaothead View Post
    Can someone explain why there needs to be contact of any sort? A standard moderator doesn't need the extra support, is it just to keep crud out?
    Thanks
    GH
    Interesting question. Surely "contact" of any sort could/would effect the barrel harmonics?



  6. #6
    Little or non as its a cosmetic cap mod locks up on shoulder of barrel cutting I use a hardy gen without noo probs so do the lads at RC also did the same on RPA as barrel was to large to have one fitted again no probs. Tape will do but will get very sticky when it hot so would worry about it if you are give jacksons a ring with the OD of your barrel he will get one out for a small charge.

  7. #7
    If the rifle & moderator threads are well cut & true, there is little value in supporting the back end - especially with modern light weight moderators. I just let mine touch the tape wrap lightly - it keeps the crud out & acts as a guide for aligning the thread when putting the mod onto the barrel. Barrel harmonics will be affected by different amounts of bush pressure I'm sure so I tend to keep mine with the same amount of tension in the fit. Moderator weight does affect harmonics & resulting POI changes, so a light mod will have less affect than a heavy one. Also the stresses involved in the reduced vibrations are lower too so it's better in engineering terms. - Less stress = longer service life of threads, undercuts etc etc.

    Ian

  8. #8
    Paul my tape is still good after 2 years on my 308 - not been a problem. It depends on what chemicals / lubes you use.
    Also I don't cook my barrel!

    Ian

  9. #9
    Rpa was a range and working rifle as said 17x1 with a big fat barrel did not allow the bushing tape was just electronic tape use only use KG products and do't melt the tape on other rifles ! mind you mil spec bug spray do's lol. A good tape is rubberised as it only sticks to itself.

  10. #10
    The ASE Utra I use is unsupported at the rear. The thread shoulder supports it well enough, and it's over 600g if I remember right, so I can't see the point of the delrin washer either

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