6mm Competition Match by MCR

Discussion in 'Gun Photos' started by Kevin Cram, Jul 20, 2012.

  1. Kevin Cram

    Kevin Cram <b>SPONSOR</b>

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    Here's another one I recently finished up. It's chambered in a 6mm Competition Match or 6mm CM. It's a 243 Winchester with a 31* shoulder. Shooting H1000 powder from this cartridge and a 115 Berger it yields velocities around 3100 fps. The biggest advantage to this round is its barrel life. 4000 plus rounds and the 6mm CM will still shooting as good as the day it was made. I'm sure you'll start seeing more of these pop up in the near future as a prairie dog rifle. These make a great F-Class or across the course cartridge too. Here's the specs, hope you all enjoy.

    Fully Blueprinted Rem. 700
    Holland Recoil Lug
    Brux Rem. Varmint Contour / 1-7.5 twist / 28" Finished Length
    Factory trigger tuned
    Wyatts MBE-5 Mag Box
    HS Precision Stock
    Full Action Bedded
    Metal Cerakoted Coyote Tan

    Tim Connelly 6mm CM #1.jpg

    Tim Connelly 6mm CM #3.jpg
     
  2. trebark

    trebark Well-Known Member

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    4000 rounds of barrel life! that's quite a statement. Would you really expect that from a competition rifle where tenty rounds in quick succession will be pounded down the barrel on a regular basis?
     

  3. Kevin Cram

    Kevin Cram <b>SPONSOR</b>

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    I've been researching this round for a couple years now. Watching those that I knew were shooting it in competition. Most are F-Class an NRA across the course where 20-50 round in succession is the norm and 1000 plus rounds per year is typical . I contacted Joe Hendricks who as far as I'm aware is the originator behind the 6mm CM. There were only a couple smiths that even have access to the reamer as it was proprietary so there are not hundreds of rifles chambered in 6mm CM yet. Those that are are yielding 3500 - 4000 plus rounds with no loss of accuracy and are still winning or are a competition threat. I'm just starting into my personal 6mm CM so it may be awhile until my round count gets up there but there are a few guidelines to follow to ensure superior barrel life and accuracy. Attached is some of the general information I've received from Joe.

    View attachment 6mm CM.pdf

    View attachment 6mm CM Start.pdf
     
  4. JamesBailey

    JamesBailey Member

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    makes a helluva tactical match cartridge too.... nice work Kevin. Sticking w/ 6.5 for now, but 6mm certainly competes with the best.
     
  5. Outlaw6.0

    Outlaw6.0 Well-Known Member

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    Chad Dixon at LongRifles Inc. has built a handful as well. He is touting roughly the same numbers for barrel life, crazy long. Very interesting. Good looking build Kevin.

    Makes me wonder if a rechamber is in order after I torch the barrel in my 6-284... :rolleyes:
     
  6. blipelt

    blipelt Well-Known Member

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    What kind of groups are they getting? Are they in the .1's with five shot groups? What is the typical powder charge grains? How many reloads before brass issues? I would love to get some info/experience on this caliber.

    I am building a hunting rifle again in one of the 6mm's. I was planning on a Dasher but with a thousand more rounds of barrel life and about 50-100fps faster with a 115 instead of a 105 I am interested.

    Brent
     
  7. blipelt

    blipelt Well-Known Member

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    Sorry Kevin saw the links after I posted. I will be curious if this will be the caliber to finally top the Dasher. Only time will tell.

    Brent
     
  8. Kevin Cram

    Kevin Cram <b>SPONSOR</b>

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    As of right now I'm only aware of 3 smiths that have the 6mm CM reamer. Chad Dixon, Dave Bruno and me ( Montour County Rifles ). I got permission from Joe Hendricks to have PTG make the reamer. PTG claimed it is proprietary, after I e-mailed Joe for permission he gave it his blessing and the reamer was made. I've built a couple of these already and have 3 more orders for rifles chambered in 6mm CM. I shoot long range varmint benchrest silhouette and woodchuck hunt so this will be my new cartridge.
     
  9. Outlaw6.0

    Outlaw6.0 Well-Known Member

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    I know Chad has been very enthusiastic about the 6mm Competition Match, get him talking about 6mm & grab your popcorn! :D

    I can only imagine what a melonited barrel & BN coated bullets would yield!
     
  10. blipelt

    blipelt Well-Known Member

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    Thanks Kevin I will do some digging before I call, I have a couple big bench rest matches coming up. Sounds like the perfect caliber for dispatching medium size game and smaller.

    Yeah those 6mm's are fun to shoot, cheap to shoot, and accurate like 1.5" group at 550yds accurate. Kind of saddens me to put my bench rifle away. Thats why I want another 6mm hunting rifle.


    Brent
     
  11. vegas steve

    vegas steve Well-Known Member

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    there are some that are claiming this new cartridge will be a barrel burner due to exactly why you are stating that barrels should last longer instead of shorter.is the chart that shows barrel life with different burn rate powders just old information or is it just therory instead of facts? to me it makes sense that using slower burning powders results in cooler temps and should prolong firecracking ,resulting in longer bore life.
     
  12. Kevin Cram

    Kevin Cram <b>SPONSOR</b>

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    The 6mm CM is not necessarily a new cartridge. I've found information on it from Joe Hendricks as far back as 2005 and I know he's been experimenting with other variations long before that . I'm not exactly sure what year he first chambered one in 6mm CM, but from 2005 to now it has finally gotten to the point where the rifles that were chambered in it have had the time to get 3500 - 4000 rounds through them and prove the longer barrel life.

    Here's some quoted info from Joe Hendrick taken from the pdf attachment earlier in this thread.

    What our research and experience has shown is that barrel life is directly related
    to how much you push the cartridge. There is much we do not understand about
    barrel life, but our experience has proven that what we are doing works and works
    very well.
    When you shoot a cartridge with less capacity you have to shoot faster burning
    powder to obtain equal velocities to a cartridge of the same bullet diameter with a
    larger capacity, or you are giving up velocity while still pushing the cartridge as
    hard as you can. (6BR, 6mm-22-250, 6XC).
    Shooting the faster burning powder does three things to your barrel.
    1) First; the faster burning powder burns at a hotter temperature. Steel, what
    all barrels are made from, is more malleable at higher temperatures. What
    this means is that the hotter the temperature inside the barrel the more
    metal that can be removed by the softer copper bullet. This is especially
    important in rapid fire strings and during practice where there isn’t as
    much time between shots or strings. The difference in temperature from
    the faster burning powders to the slower burning powders is minimal,
    however over 2000 to 3000 rounds it does make a difference.
    2) Second with the faster burning powder, the pressure behind the bullet goes
    up very fast and goes down very fast. The maximum pressure of the shot
    takes place very quickly in or around the throat area of the barrel. This
    puts the maximum force on the most important part of the barrel. Anyone
    who has ever bent a paper clip or wire back and forth understands that if
    you do it enough the material weakens and eventually breaks. Faster
    burning powder is doing this your barrel and overtime it weakens. This is
    obviously a factor in barrel life.
    3) Third faster burning powder burns faster and burns more in the throat of
    your barrel. What this means is that the area where the bullet contacts the
    lands of the barrel takes all of the abuse. Not just from the bullet, but from
    the powder also.
    What has been concluded from this is that faster burning powder stress the barrel
    more than slower burning powder, by the force of the pressure, by the heat that
    weakens the steel, and then by the burning of the powder.

    The reasons for longer barrel life:
    1) First the slower burning powder burns at a cooler temperature than faster
    burning powders. These lower temperatures have a great affect on
    extending barrel life. The barrel is not subject to as hot of a temperature
    and therefore the bullets do not have as much of an affect on the steel as
    with faster burning powders. The barrel’s steel is less malleable because
    of lower temperatures. You are not subjecting your barrel to the same
    temperatures you do with faster burning powder. Keep in mind that the
    temperature difference is minimal to you and I but to the barrel it is
    making a huge difference.
    2) Second the pressure curve is much different with a slower burning
    powder. With a slower burning powder the pressure peak is down the
    barrel much farther. The pressure curve is much smoother and even
    though the peak pressure is about the same it stresses more of the length of
    the barrel. What this means is that you are subjecting your barrel to a
    lower average stress over the length of the barrel on every shot and the
    stress is spread over a larger portion of the barrel’s length. Again, think of
    the paperclip, if you only bend it a little and bend it in different places it
    takes much longer to break it. The lower pressure and the pressure applied
    over a greater amount of the barrel adds to the life of the barrel.
    3) Third, it burns slower. Therefore the powder is burning as it goes down
    the barrel. However, we want as much of the powder to burn in the case
    as possible and that is part of the design of the 6CM. The slower burning
    powder gives a more even affect to the barrel. The burning powder is less
    concentrated in one part of the barrel and barrel ware is more uniform.
     
  13. vegas steve

    vegas steve Well-Known Member

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    yes this all sounds accurate to me,but most of the information on the internet and forums claim just the opposite.i've always been a .243 win fan myself,but have been reading that the .243 has a shorter barrel life than most others.i myself have not found this to be true.especially since i've started shooting heavier bullets and slower powders from mine.
     
  14. Capt Academy

    Capt Academy Well-Known Member

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    How does it compare to the 6XC. Would it be a better more accurate round? How would it work in a tactical match?