6mm cm
- Thread starter bedrock
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Already have 2 6brs a 243AI and a 6-284 but planning to order another 6mm barrel or at least set the 6-284 back when the time comes. Since I will likely be buying a reamer I'm
thinking either a Dasher or a CM. Sounds like the CM is good for 1000 and easy on barrels. Kinda like my 6's.
thinking either a Dasher or a CM. Sounds like the CM is good for 1000 and easy on barrels. Kinda like my 6's.
I haven't seen a reamer diagram as yet. Talked to Dave Bruno in the States on the net and he suggests a long leade. I'll call Dave Kiff one of these days and get his opinion. The CM is basically a 243 Ack but a 30 degree shoulder rather than 40. Apparently with a slow powder like H1000 and heavy bullets you're still around 3000 fps and 3500 rounds down the pipe seems to be the norm. It's been around for some time but under a different name (which I forget) and Redding makes the dies. Dave Bruno stocks the dies and will ship to Canada. It seems a 4 grove barrel rather than a 5 or 6 is reccomended. If you go to 6mmbr and punch in 6MM CM there's quite a bit of reading there. Also Winchester brass is reccomended with no turn. I know my 6-284 will eventually have to be set back so I think I'll try the CM down the line.
Mystic Precision
CGN Ultra frequent flyer
- Location
- Summerland, BC
I would be very surprised if you got much over 2000rds of accurate rifle with that big of a case. Likely more like 1500rds.
But then, define accuracy.
As a frame of reference 6BR's are loosing F class accuracy around 2 to 2500rds. Hard to imagine burning almost twice as much powder at elevated pressures and getting more bore life.
Yes, there are several variants on the same theme. Some even use a 6Rem as the parent to get a really long neck.
Jerry
But then, define accuracy.
As a frame of reference 6BR's are loosing F class accuracy around 2 to 2500rds. Hard to imagine burning almost twice as much powder at elevated pressures and getting more bore life.
Yes, there are several variants on the same theme. Some even use a 6Rem as the parent to get a really long neck.
Jerry
You very well could be right Jerry. All I have to go on is what's on 6br. I really don't
know if I can set the 6-284 back and expect another 1000 rounds or not. Probably optomistic. Other than reamer cost, a FL die and chambering cost it's not going to cost a ton to play with it. If I can get 500 or a 1000 out of it I'll know if I'm going to chamber
a fresh barrel for it.
know if I can set the 6-284 back and expect another 1000 rounds or not. Probably optomistic. Other than reamer cost, a FL die and chambering cost it's not going to cost a ton to play with it. If I can get 500 or a 1000 out of it I'll know if I'm going to chamber
a fresh barrel for it.
This is the 6mm cartridge i am looking to build. There are several differences from the SLR and original 243. the 3000 rounds seems to be a common theme and appears to have supporting evidence
as the previous name of this cartridge is called the "Egolf"
from joesr the co-designer
It is basically a 243 win case with a 31 degree shoulder. In changing the shoulder length from 20 to 31 degrees I split the difference and added a little to the neck and a little to the body.
What is the advantage over the 243 AI. It depends on what game you are shooting. The reason I kept the 243 Win tapered body was for feeding in rapid fire competition.
This cartridge works exceptionally well for me.
However, if you are shooting slow fire only then you can get better velocity with the 243 AI.
The key is not the cartridge but how you load it. Stay away from faster burning powders, even H4350 is too fast and burns barrels. H1000 is the best powder I've found for the 6cm. Possibly with the 243 AI there is enough room for Retumbo or N170.
Fire Forming for the 6CM is fairly easy. I size my virgin 243 brass with a 243 die (not the 6CM die).
Then I use 47 grains of H1000 behind a 105, 107 or 108 bullet seated 10 to 20 into the rifling. You have to seat the bullet into the rifling to fire form so that it pushes the back of the case against the bolt face.
Shot it and the brass is formed.
some neck dimensions
the .243 neck length is .241
The .243AI neck lenght is .245.
The 6CM's neck lenght is .264.
The 6SLR's neck lenght is .321.
Here is a pic
6cm 243 Imp 6mm Slr
ray whitney
The .243 Win is a bear on the throats of barrels in part because of its case design (i.e. short neck and 20Ëš shoulder angle) which has a tendency to put the focus of the hot gasses right up in the barrel (i.e. people call it a "barrel burner" for that reason). Both the 6CM and the 6 Super LR have longer necks (6CM only slightly longer, and 6 Super LR a lot longer) and steeper shoulder angles than the .243 Win. (6CM 31Ëš and 6 Super LR 30Ëš) which changes the focus of the gasses and the efficiency of the cases. Running slower burning powders can help as well (H4831SC, H1000, etc. that provide more push further down the barrel than back at the chamber
as the previous name of this cartridge is called the "Egolf"
from joesr the co-designer
It is basically a 243 win case with a 31 degree shoulder. In changing the shoulder length from 20 to 31 degrees I split the difference and added a little to the neck and a little to the body.
What is the advantage over the 243 AI. It depends on what game you are shooting. The reason I kept the 243 Win tapered body was for feeding in rapid fire competition.
This cartridge works exceptionally well for me.
However, if you are shooting slow fire only then you can get better velocity with the 243 AI.
The key is not the cartridge but how you load it. Stay away from faster burning powders, even H4350 is too fast and burns barrels. H1000 is the best powder I've found for the 6cm. Possibly with the 243 AI there is enough room for Retumbo or N170.
Fire Forming for the 6CM is fairly easy. I size my virgin 243 brass with a 243 die (not the 6CM die).
Then I use 47 grains of H1000 behind a 105, 107 or 108 bullet seated 10 to 20 into the rifling. You have to seat the bullet into the rifling to fire form so that it pushes the back of the case against the bolt face.
Shot it and the brass is formed.
some neck dimensions
the .243 neck length is .241
The .243AI neck lenght is .245.
The 6CM's neck lenght is .264.
The 6SLR's neck lenght is .321.
Here is a pic
6cm 243 Imp 6mm Slr
ray whitney
The .243 Win is a bear on the throats of barrels in part because of its case design (i.e. short neck and 20Ëš shoulder angle) which has a tendency to put the focus of the hot gasses right up in the barrel (i.e. people call it a "barrel burner" for that reason). Both the 6CM and the 6 Super LR have longer necks (6CM only slightly longer, and 6 Super LR a lot longer) and steeper shoulder angles than the .243 Win. (6CM 31Ëš and 6 Super LR 30Ëš) which changes the focus of the gasses and the efficiency of the cases. Running slower burning powders can help as well (H4831SC, H1000, etc. that provide more push further down the barrel than back at the chamber
Mystic Precision
CGN Ultra frequent flyer
- Location
- Summerland, BC
There is a better chance of getting more life from a "fast" burner as the rifling further down the barrel is less charred.
A palma 308W that has over 4000rds will have toasted rifling for a very very long ways.
As with any of these wonder chamberings, you have to define what is accuracy.
Many SR BR shooters are taking off 6PPC barrels after 800rds and that is only burning around 26gr of powder. But those barrels are still shooting sub 1/4 min.
Best way to prove to yourself is to build it and shoot it.
For F class, we have yet to find a F Open competitive set up that will go much over 2000rds. The vast majority start to loose their edge at 1000rds.
Some of the best wind cheaters are getting tired around 800rds.
If the 6BR can't do it, makes you wonder how burning almost 80% more powder can. 30 deg and a very long for cal neck.
For comparison, I shot a 6.5 Mystic/260 improved for several years. This one has a 40deg shoulder and a decent length neck for the bore. Burning right around 48gr of H4831SC, 1500rds was risky going into a match
Peak is before 1200rds and that is with both cut and button rifled top tier barrels.
YMMV
Jerry
This is the 6mm cartridge i am looking to build. There are several differences from the SLR and original 243. the 3000 rounds seems to be a common theme and appears to have supporting evidence
as the previous name of this cartridge is called the "Egolf"
from joesr the co-designer
It is basically a 243 win case with a 31 degree shoulder. In changing the shoulder length from 20 to 31 degrees I split the difference and added a little to the neck and a little to the body.
What is the advantage over the 243 AI. It depends on what game you are shooting. The reason I kept the 243 Win tapered body was for feeding in rapid fire competition.
This cartridge works exceptionally well for me.
However, if you are shooting slow fire only then you can get better velocity with the 243 AI.
The key is not the cartridge but how you load it. Stay away from faster burning powders, even H4350 is too fast and burns barrels. H1000 is the best powder I've found for the 6cm. Possibly with the 243 AI there is enough room for Retumbo or N170.
Fire Forming for the 6CM is fairly easy. I size my virgin 243 brass with a 243 die (not the 6CM die).
Then I use 47 grains of H1000 behind a 105, 107 or 108 bullet seated 10 to 20 into the rifling. You have to seat the bullet into the rifling to fire form so that it pushes the back of the case against the bolt face.
Shot it and the brass is formed.
some neck dimensions
the .243 neck length is .241
The .243AI neck lenght is .245.
The 6CM's neck lenght is .264.
The 6SLR's neck lenght is .321.
Here is a pic
6cm 243 Imp 6mm Slr
ray whitney
The .243 Win is a bear on the throats of barrels in part because of its case design (i.e. short neck and 20Ëš shoulder angle) which has a tendency to put the focus of the hot gasses right up in the barrel (i.e. people call it a "barrel burner" for that reason). Both the 6CM and the 6 Super LR have longer necks (6CM only slightly longer, and 6 Super LR a lot longer) and steeper shoulder angles than the .243 Win. (6CM 31Ëš and 6 Super LR 30Ëš) which changes the focus of the gasses and the efficiency of the cases. Running slower burning powders can help as well (H4831SC, H1000, etc. that provide more push further down the barrel than back at the chamber
Have you tried N560? It worked very well for me in my 6mm LR
Last year I built a 6 mm slr so far I am happy with it, I went with it because some guys are claiming much longer barrel life than the regular 243 .
I did some testing with some H1000 and magnum primers with 105 bergers and was around 3200fps the creedmore should be along the same lines I would think.
I did some testing with some H1000 and magnum primers with 105 bergers and was around 3200fps the creedmore should be along the same lines I would think.
Hi Coyote
The 6cm is the Competition Match designed by Joe hendrick and is different from the Creedmore.
the 6mm SLR is a nice cartridge and something I was looking at before but the easy of forming 6cm cases is what won me over (still haven't got it built yet). The upside is that the 6cm can scream those 115 at 3200+ but more importantly you can back it down to around 3100 and still have excellent accuracy.
or the 117 matrix..
Trevor
The 6cm is the Competition Match designed by Joe hendrick and is different from the Creedmore.
the 6mm SLR is a nice cartridge and something I was looking at before but the easy of forming 6cm cases is what won me over (still haven't got it built yet). The upside is that the 6cm can scream those 115 at 3200+ but more importantly you can back it down to around 3100 and still have excellent accuracy.
or the 117 matrix..
Trevor
Trevor 60 my mistake I thought it was a creedmore , I have been using my 6br FL die to form the neck shoulder and a 308 FL die to do the body so far this has worked good for me .
I just use a regular 243 forster micro adjust seater , I used my reamer to cut myself a bushing die for sizing the necks .
I think the 6mm CM will be well capable of launching the 115's , when I built my slr I had planned on shooting the heavys but berger came out with the 105 hybrids right about the same time so I throated for the 105,s.
The new hybrid 105's can be launched faster than the 115 grainers and have a slight balistic advantage.
You may want to take a good look at this bullet before you order your reamer .
I just use a regular 243 forster micro adjust seater , I used my reamer to cut myself a bushing die for sizing the necks .
I think the 6mm CM will be well capable of launching the 115's , when I built my slr I had planned on shooting the heavys but berger came out with the 105 hybrids right about the same time so I throated for the 105,s.
The new hybrid 105's can be launched faster than the 115 grainers and have a slight balistic advantage.
You may want to take a good look at this bullet before you order your reamer .
In my 6mm slr I run 243 brass through the fl die to form the neck and 30 degree shoulder load and shoot.
For the 6CM you load 243 brass and shoot, it forms when fired the 6 slr is formed before shooting.
I think either one of these cartridges would be close to equal in performance the 6CM would hold a bit more powder but not much more I would say maybe 2 grains.
When I was shopping around to wildcat a 6mm I stumbled on the 6 slr after I had formed some brass for my idea of a wildcat they were almost identical so I ordered a reamer for the slr instead.
For the 6CM you load 243 brass and shoot, it forms when fired the 6 slr is formed before shooting.
I think either one of these cartridges would be close to equal in performance the 6CM would hold a bit more powder but not much more I would say maybe 2 grains.
When I was shopping around to wildcat a 6mm I stumbled on the 6 slr after I had formed some brass for my idea of a wildcat they were almost identical so I ordered a reamer for the slr instead.
