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Thread: modifying mod

  1. #1

    modifying mod

    has anyone increased their .25 ase utra a5 to .30 cal? how you do it? what diameter hole?

  2. #2
    Regular Poster buck52's Avatar
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    I had a T8 increased from 25 cal to 30, an engineer did it in a lathe to ensure the hole was dead centre.

    Jacksons website will give you the hole sizes

  3. #3

    Re: modifying mod

    Quote Originally Posted by pete evans
    has anyone increased their .25 ase utra a5 to .30 cal? how you do it? what diameter hole?
    Pete as a rule of thumb you need to bore .75 to 1.00mm bigger than bore size. If I was you I would go 1.00mm to give you a bit to play with, the problem I would for see is how are you going to remove the swarf from inside the mod? You could try putting a small magnet inside to lift it out after boring.

    Best rgds

    Tahr

  4. #4
    I once had a T4 for a .222 and then got a variation to use a mod on a .308 so all I did was run a drill though it and now use it on all my calibres from .222 to .308
    Once done, I dropped a .308 bullet through it to make sure it cleared the hole.
    No swarfe, no magnets, no lathe, just lucky I suppose.

  5. #5
    EMcC

    I guess your drill would self centre on the already drilled/reamed holes. As for swaft burned up? Or blown out when you fire the rifle?

    Best rgds

    Tahr

  6. #6

    Re: modifying mod

    Quote Originally Posted by pete evans
    has anyone increased their .25 ase utra a5 to .30 cal? how you do it? what diameter hole?
    I was under the impression that the internal diameter of the hole in ase utra .25 cal mods is 7.6mm,I don't know what the .30cal bore channel is. However as always - consult a gunsmith before doing anything rash!

  7. #7
    Regular Poster buck52's Avatar
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    Baffle hole diameter

    Standard baffle apertures are 7.5 mm , 8,5 mm, 10,5 mm and 13.0 mm. As a rule, the bullet caliber (bullet actual diameter ) plus at least one millimetre gives the exit aperture diameter.

    7.5 mm hole takes 222, 223, 22-250, 6mm, 243, etc.

    8.5 mm hole takes 6.5mm 270, 7mm, 308 , 30-06 etc.

    10.5 mm hole takes 9.3mm, 338 etc.

    13 mm hole takes 45-70 etc.

    The reinforced "magnum" model (stamped "M") for cartridges above 30-06 case capacity has 10.5 mm exit aperture as standard (other aperture sizes to special order).

    The smaller the baffle hole diameter the better the sound suppression, but the difference between each of the above hole size increments is only 1 or 2 dB. In general, it is better to reduce the sound by adding more baffles than risk making the baffle holes too small.

    All rifle bullets yaw a little on leaving the muzzle. The longer the bullet the more baffle hole clearance we need to accommodate this yaw without risk of a bullet grazing a baffle. If a bullet grazes a baffle, it can cause a "flyer" (a shot which flies well out of the group).

  8. #8
    have been told by jackson rifles that drilling out .25 s5 to.30 cal will knacker the mod. Anyone in the market for a .25 cal s5 1/2 inch unf? or straight swap for .30 cal?

    pete

  9. #9
    Regular Poster buck52's Avatar
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    Quote Originally Posted by pete evans
    have been told by jackson rifles that drilling out .25 s5 to.30 cal will knacker the mod. Anyone in the market for a .25 cal s5 1/2 inch unf? or straight swap for .30 cal?
    pete
    What a surprise they said that, they would'nt be thinking of another sale surely!!! so taking half a millimeter out knackers it as I said, mine was drilled out by a very competent gunsmith (Richard Pope) it didnt "knacker" it and it still works fine after 18 months

  10. #10
    i thought that too. drilled it out at work on lathe. seems ok

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