243 Imp 30 the same as 6CM (Competition Match) ?

[SteveBurton]

I have been looking at several different 6mm cartridges for my next build and I am confused by these two. I read about the 243 Improved 30 on this site, 243 Imp 30? and it looks slightly better than the 243 AI due to the 30 degree shoulder. I have also read several posts about people shooting the 6CM but I cannot find a page with any information on it. I have read that it can be fire-formed from 243 brass and it has a 31 degree shoulder. Other than the 1 degree difference in the shoulder, it looks the same as the 243 Imp 30.

Here are a couple of pictures showing both cartridges.
The pic on the left shows the 243 and the 243 Imp 30.
The pic on the right shows a 243, 6CM and 6mm Super LR.
Does anyone have more information on these two cartridges? I'm just curious.

I'm leaning towards the 6mm Super LR on the right due to the longer neck so that I can seat 105 grain bullets out farther. It also uses the 243 as a parent cartridge. People are still getting 3100+ fps shooting a 105 AMax with this cartridge.
Super LR

 

[Dgd6mm]

They are close but not the same. Body taper, 6CM necklength is a touch longer, case capacity is a little more. If you don't want to ff brass go with the SLR. If you really want to learn about the 6CM there are pages and pages on 6br. You can Google it or Joe Hendricks, he won at Camp Perry this year with it. I own 3 of them. I think Joe has set 5 or 6 records with his, he designed the cartridge. It is not well known, Joe is a shooter and really doesn't do much to promote the cartridge. He has a mission statement of the 6CM, it has met and exceeded those goals. My 27" runs a 115 DTAC at 3153 fps using H1000, I did have it running 3225 but slowed it down and my 10 shot group at 1000 yards shrunk , 6.5" to just under 4.5". I put it on paper at 3900 rounds, .4 moa at 600 yards 5 shot group. If there was not a 6CM, I'd be shooting the 6SLR. I could go on and on with the group's I have shot with mine. I also have done quite abit of 1000 yard and done well.

 

[SteveBurton]

Dgd6mm,

Thanks for your reply. I did find several threads about the 6CM on the forums at 6br. I also saw several jabs between Joe and Robert about these two cartridges.
These cartridges have slight differences but are also very much alike. Do you know if one has better bolt lift/extraction than the other? What brass do you use? I would like to use Lapua brass because I have had good luck with it and both look to be good candidates. I see that the 6SLR is better formed with Winchester brass. What is your opinion of the bearing surface with the shorter necks on the 6CM/243 Imp 30 when using 105 grain bullets?

Bottom line is this will be for a hunting rifle and I don't need to shoot many rounds in a row. I'm looking for something different than the 243 Win that will push 105-115 grains around 3100 fps out of a 22-24" barrel. I don't know if the longer neck but reduced capacity of the 6SLR would suit be better than the other two.

Thanks,
Steve

 

[Dgd6mm]

First off, Mr. Whitley has an agenda and Joe is just a shooter and does not put food on the table or money in his pocket promoting his 6MM Competition Match. Extraction with Lapua brass becomes difficult after a few firings in both the SLR and CM because the web diameter of the case is a tad bigger then other .243 brass. You can fix that with a small base die if you were to choose to shoot Lapua. You will also have to neck turn the Lapua brass because of a doughnut forming. Some of my Winchester brass has 20 firings on it.I shot Lapua in my Benchrest CM a few times but did not like dealing with the extraction click that came back quickly, so I gave it away. There is NO difference in accuracy between brass....

When you wrote the bottom line part, you really answered you own question. I cannot say if one is more accurate then the other, but what I can tell you is that at :800 yards on a 600 yard IBS target I shot a 99-4x 10 shot group that measured 2"s. This was at a club shoot. This was with my BR 6CM rifle.



Now for the bottom line, if it is for hunting, 6SLR out of a 24" with a 105 Amax. You may have to use a faster powder to get the speed you want, barrel life will suffer a little, but it will be a hunting rifle. I don't go by necklenght, which the 6CM is a little longer then a .243, but the necklenght is not near as long as the SLR. Most 6CM barrels are 27" - 32", I've never heard of H1000 being shot in a 6CM in a 24" barrel.

 

[SteveBurton]

If I go with the 6CM, where can I find a set of dies for it and a reamer for my smith?

 

[Dgd6mm]

Call Dave Kiff at PT&G he will set you up with the one you need depending on your application, he has all 3 reamer prints. Redding sells the die, it is labeled (.243 Egolf ) don't ask me why, also Dave Bruno which is Joe's smith and has become mine, he may have dies in stock.


Robert Whitley shot the 6CM before introducing the 6SLR, and he loved it...