It belongs here!
My answers on the 6CM are purely from my experiences which is a “team” member shooting one at the same bench for the last 3 years. All answers are my observations, since I spot and call wind for this person (who happens to be my father). I’ve personally shot it and personally borescoped this gun.
So you say you’re considering the 6CM because you need more oomph than the 6 BRX? The 6 BRX is a fine cartridge and would serve you well at 1K, with no issues provided you do your part reading wind. If you’re thinking you’re going to stick with the 6’s you’ll only gain or lose an inch (or a couple inches) from the wind.. Not sure if you can tell the difference in a 5 or 8 mph wind or not? My point is, most of those 6’s including the 6CM are going to be very comparable to what you already have. If your thought is to go to the 110 SMK’s (I recommend, which I’ll indulge why a little later) or 115 Bergers, to gain less wind drift than the 107’s or 105’s, well you aren’t going to gain enough that you could “misread” a 5-8 mph drift and the bullet make up for it.
So on to your questions, and mind you I’m not trying to convince you to go one route or the other, purely give you facts and observations so you can come to your own conclusions on what you want.
First off, barrel life: This is a loaded question with no definite answer. Many factors involved including how good is the steel, what powder you’re running, cleaning techniques, and obviously which bullet. The 6CM was designed by Joe to give folks XC accuracy with longer barrel life.. I haven’t seen that on my bench. How do I know? Well beside that CM there are 3 more (soon to be 4) 6XC’s, all shooting the same amount of rounds. Let’s base this off what the designer recommended for the CM.
Using your typical H1000, and 49.5 grains to push a 105 Berger 3100-3150 fps (real world observations) and where the accuracy node is for that barrel.
I shoot 39.2-39.5 grains of H4350 in all my XC’s to hit the magic 3075fps needed for the 107 SMK’s.
Ok Longer barrel life? Out of a 1# jug of powder I get 177 rounds, my father gets 144 (Basic math of 7000/39.5 or 49.5)
Lets base this off money now. $205 for 8# jug of H4350 or H1000 – 56,000 grains of powder.
6XC – 1418 rounds (cost per round in powder is $ .144)
6CM – 1131 rounds (cost per round in powder is $ .181)
Right now we both have 2500 rounds on Krieger 8 Twist conventional 4 grove barrels that are almost identical. Borescoping and checking erosion with a OAL gauge, he has experience more erosion than me.
So I have spent $360 on powder so far and he has spent $452.50.. a $92.5 difference already.
See where I’m going with this??? We can push this out to where the extra powder you put in a CM actually washes out the “longer barrel life” because you just paid for a new barrel by putting it into powder. Now my one XC is looking like I’ll get an honest 1000-1500 more before I need to worry, but only time will tell. That all depends on the accuracy I expect which is less than ½ MOA by the way.
Lets just use 4000 as a round count.. I’ll probably get that out of my 6XC
$576 vs $724 in powder, $148 difference. Will the 6 CM get 4000? By my observations and his barrel (maybe, maybe not… he’s already ahead of me on erosion) Will my XC get more than 4000.. I’d say no as well. So at the end of 4K rounds, the guy shooting the CM, had to form cases, spent $150 more on powder to only achieve 25-75fps more? Is that the kind of oomph you're looking for?
I really believe it has to do with the short freebore and lead angle I used on my chamber. A reamer that I intend on keeping a hold of for a very long time as it’s proven to.
Again, open to debate from anyone, but these are real world observations of the 6XC an 6CM on my bench. You can see you just can't throw a number like the XC is only good for 1500 rounds and the CM is good for 4500. All depends on the bullet, the barrel, the powder, the cleaning techniques and I believe the chamber (especially the freebore and lead angle)
By the way, the other two 6XC’s are falling right in line with the other one, but they only have 1100 & 1500 rounds on them and show minimal wear and great promise.
Again.. you asked I’m giving you facts based off my observations for you to come up with your own conclusions on whether to stay with the 6 BRX or go with another variation of 6. The question is to what cost? To gain somewhere else (as in barrel life) you’re giving up somewhere else (as in powder costs).
Bullet selection: I’m a Match King dude.. why? Well their tolerances seem to be much tighter than Berger from my observations. You can buy multiple lots and sort by true bearing surface or ogive to base and have very few that are more than .005 off. That can be over the course of several hundred lot numbers. I sort all my bullets by true bearing surface and normally have two piles .001 difference and it’s all in which bullet I used to set my zero on. Which basically means they are all within .002 over the course of 1000’s of bullets. I have not observed that with Bergers, ever. Also I strictly shoot the 107’s and they constantly outshoot the 105 Hybrids in my guns… Hey, it’s what my barrels like! So this may be biased, but the reason I’d suggest the 110 SMK’s over the 115 Bergers is they have the same bearing surface as the 107’s. So what you gain is a better BC bullet, but the same amount of bullet touching steel therefore, the same amount of erosion. Make sure you go with a 7.5 twist to be sure though. 8’s just may not cut it. Only your barrel will tell you what it likes best though so this is purely a "I like this better because discussion"
Donuts: You will get donuts in both rounds, especially if you’re using Redding Type S dies.. both observed around 5-6 case firings. You can get donuts in all rounds if your using that type of die. I have over 12 firings on my XC cases and they are still like new. Anneal every 2 shots. I gave my Father my Tubb sizing die for his other 6XC and I’m not sure he’s seeing the donuts (his is a case and neck bushing all in one) I prepped all the cases and you can either cut them out with a K&M turner with carbide pilot w/ cutter. It’s what he did on his 6 CM since his loaded rounds are into the donut. My XC a custom reamer designed to keep my bullet out even though it’s a shorter freebore. I leave the donut there as it's not hurting me any.
Inherent accuracy: 6XC.. no fuss caliber. Basically I break in the barrel , shoot a ladder and normally have an accurate load that I can tweak in less than 35 rounds. Happened the same on all 3 of my last ones. 6CM you will need to tinker. I've seen my father tinker A LOT more than me with the 6CM. Maybe he just like to tinker though? Also I’ve watched the accuracy come and go, (remember I spot for my father) but you have a different shooter, different reloading techniques, etc… so I can’t compare one to the other, other than look at the scores.. My son and myself are normally beating those 6CM’s with XC’s. Is it the magic caliber or is it the shooter? I'll take the guy behind the trigger.
That’s all I have.. to the rest of your questions, someone with real world experience will need to chime in! Btw my father and I had this discussion about this time last year. He was looking to build another gun in 6CM and I convinced him to go XC. He's glad he did as he's shooting better scores with the light in XC than his heavy in CM.
My 5R’s are in 6.5’s and they shoot great but are irrelevant to this conversation.
Again, this wasn’t meant to start a flame war, just provide info. At the end of the day ANY 6 variation will get the job done well.. in fact, what you have is a great round and I wouldn’t go further. How much “oophm” do you want? You didn’t specify, but likely all of the 6's are comparable. If you need "a lot of oophm" maybe look at something in the 6.5 range possibly?
Maybe it’ll open your eyes to consider something like the 6.5x47L? Run the ballistics… basically the same round as the XC, but smaller primer and bigger bullet. You don’t get screaming speeds with it, but they shoot good as well.
When I started shooting 1K, I was one of those magnum dudes... I now shoot strictly 6's and 6.5's since the 30's can't hold a candle to the accuracy of 6's. Just learn to read wind and you'll be fine! There's no cure all caliber for that.
By the way, you can apply the same logic of BRX to 6XC with powder costs and have a different argument that the BRX cost's less. Although the spread is not as large seeing as how the going load for those is around 4 grains less.
Food for thought……
