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Thread: cmm4 moderator help required please

  1. #1

    cmm4 moderator help required please

    For those that use the cmm4 modetator could you let me know

    What calibre do you use
    What mod size fo you use
    What bullet type/make do you use
    What groupings do you achieve

    Im getting very conflicting advice from jacksons on bullets and want an idea of what other people use before i buy 100 reloading heads

    Cheers

    David

  2. #2
    Not sure if I understood right,
    normally one fits a moderator that suits the caliber. This should not affect
    any bullets that are fired out of it unless one stupidly decides to shoot sabots.

    I tested a new delta ultralight all aluminium moderator last week which is similar to the a-tec.
    It had just about the same POI as the steel version. We had a up to 6.5mm version
    and tested with a 223 and a 243.

    edi

  3. #3
    Im using a cmm4 .30 calibre on a tikka .25-06 using 85 grain and 100 grain ballistic tip Federal, i find it a great mod, havent shot many groups.

  4. #4
    Quote Originally Posted by ejg View Post
    Not sure if I understood right,
    normally one fits a moderator that suits the caliber.
    Just wondered as my friend has a t8 and the one for his calibre caused problems so he swapped for the next size up and had no problems whatsoever (he shoots a 22/250)

  5. #5
    Jacksons initially told me I could not use 100g bullets, non lead bullets or 55g ballistic tipped bullets with this moderator in .243

    I thought this strange as if I want to shoot red deer I would need the 100g bullets from a legal point of view

    When I phoned back and queried this I was told I could use 100g but only norma as they are not boat tailed.

    Seems like a load of nonsense to me and the only factory round I can buy where i stay is federal which in my rifle does not group well.

    Im going to buy bullet heads to load myself but am interested what works for other people with this moderator before i do.

  6. #6
    I have a cmm A-L 6.5 AND use it on a .25-06 75gr V-Max for Fox Vermin an 120gr Nossler Partion for Muntjac up to Big Red's apart from different poi (qr scope mounts an two scope's) both as good as one hole at 100yrd's

  7. #7
    Don't use sabot bullets. ( ok there aren't many about in .243 / 6mm)

    An absolute must is to ensure that your bullets are stable, the correct weight and velocity for your rifles twist rate. Test groups before fitting and moderator. if you are getting keyholing on the target, to not use that ammo.
    Also if you are pushing a frangible bullet very hard and very fast, and it maybe reaching the point of disintegration, chances are if you fire it through a mod, the increase in back pressure will invarable be the straw that broke the donkeys back and may come apart in them mod. A bit of common sense on bullet choice, twist rates and velocity keeps you and your mod on the safe side.

    lets say you had a .223 Rem with a 1 in 12" twist, I wouldn't recomend shooting 70grain + bullets through a mod. chances are they are unstable directly in front of the muzzle and will clip a baffle.

    or a .308win with a 1 in 12" twist. I wouldn't recomend shooting 200 - 220gr bullets, especialy at subsonic velocity chances are they are unstable and will clip a baffle.

    or a 6.5x55 with 1 in 9.5" twist, I wouldn't recomend shooting 160gr bullets. same story.

    There is a relationship between the clearance of the baffle bore, the turbulance caused by propellant gasses excellerating past the bullet, certain types of bullet bieng effected by the turbulance more than others, and innaccuracy( or even catastrophic failure in the worst case senario) when using a moderator, or indeed a muzzle brake,

    Basicaly what it amounts to is that a moderator (or a muzzle brake) needs enough clearance in the bore of the baffles, and the baffles need to be of the right geometry, and the correct distance apart to counter effect any negative influence on the projectile(bullet) during the time of its flight through the muzzle attachment-moderator or brake.

    very tight clearances on the baffle bore to bullet diameter are a recipie for disaster for several reasons.

    you never know if a factory rifle barrel bore is 100% in the middle of the barrel
    you never know if the muzzle therad is 100% inline with the axis of the bore

    from experience it pays to have at least 1.5mm clearance in the bore of the baffles above the size of the bullet to be used. ( so a 6.5mm bullet would idealy have a baffle bore diameter of 8mm)

    firing a smaller bullet, say a 5.56mm ( .223) through the same 8mm bore diameter of baffle gives you 2.5mm clearance ( or near enough) and providing the geometry of the baffles is correct, and the baffles are the
    correct distance apart,
    there is no noticable loss on sound reduction.

    There is a mountain of theory and practice behind sound suppressor / moderator design and manufacture, but in laymans terms, I wouldn't worry about it too much.

    So long as your rifle shoots the bullets-loads you have chosen without displaying bullet instability, and you choose a moderator with enough clearance in the baffle bore,
    then you should be absolutely fine with any moderator fitted.

    rgds Pete

  8. #8
    Hi David

    I have an old type Steel A-Tec CCM I know the baffles are similar but not the same as the Alloy one. I run 95gn SST and 100gn SP boat tails and 95gn Noslers though it with no problems, and despite what has been said, I even shot some 105gn VLDs which were key holing at 50 yards (1 in 10 twist) in truth if I had thought about it I guess I should of tried them with out the moddy on first. But I guess I was lucky or theory is not always born out in practice, I suppose it is down to how much clearance you have between the baffle and bullet.

    I would have thought that any moderator sold for a particular calibre should be designed to work with any bullet type with the proviso that it was stable and did not vaporise the bullet because of too fast a twist rate or too high a velocity.

    ATB

    Tahr

  9. #9
    I suppose it is down to how much clearance you have between the baffle and bullet.

    that, plus distance between baffles, distance through baffles and baffle shape

    I would have thought that any moderator sold for a particular calibre should be designed to work with any bullet type with the proviso that it was stable and did not vaporise the bullet because of too fast a twist rate or too high a velocity

    Thanks Thar, thats what i was trying to say

    rgds Pete

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