6mm CM or 6mm PRC

[brocksw]

Having some trouble making a comparison here since there isn’t a lot out there for info on the 6mm prc. My goal is to get the 95 lrx up around 3400-3500 fps in a 18-20” tube, without fire forming and trying to get to 1000 round barrel life.

I’ve seen some reports of the 6 cm getting into the 3200s with a 24” tube, but again, I’d like to stick to 18-20”. That’s what is making me think about going up a notch to the prc case.

I’m also aware of the 6 um over on RS, but I have a feeling the formed brass will be very expensive and hard to get with all the demand RS is creating. Dies will also be expensive. Capacity for the UM would be more than the 6mm-6.5 prc as well, which will work against me for barrel life. Plus, I like the idea of buying 6.5 prc brass(easier to find), necking down and shooting and being able to use a standard prc bushing die.

It’ll be a barrel burner for sure, but it has some convenience and cost benefits over the 6 UM.

Let me have it…

 

[Deleted member 16014]

If you really want to get to 3400-3500 I think your answer is pretty clearly prc between those two.

 

[WapitiBob]

I saw Avery say the UM will have the live of a 28 Nosler. Not much reason to own a 6mm at that point. Wouldn't a 6-7PRC get you there without much effort?

 

[brocksw]

If you really want to get to 3400-3500 I think your answer is pretty clearly prc between those two.

I’d agree, but I have yet to see anything that confirms it. Perhaps my title is poor, but there’s also the 6 Saum as a tweener between the prc and UM. Trying to string together information that makes me confident I can get there with a prc and not smoke a barrel. Seems like once you go to the saum categories, barrels take a hit. So if it takes a saum case to get there I may just go the 6 cm route, push it harder, and live with the velocity it gets me.

 

[mtmuley]

You gonna hunt with a pea shooter like that enough to burn a barrel? mtmuley

 

[BackofBeyond]

I think your 6 PRC should get you close. But, hear me out… 6x7 PRC.

If you’re going to be a bear, be a grizzly.

 

[brocksw]

You gonna hunt with a pea shooter like that enough to burn a barrel? mtmuley

I tend to shoot the smaller calibers more. For fun, hunting, having my boy shoot, etc.

I think your 6 PRC should get you close. But, hear me out… 6x7 PRC.

it would do it for sure. 600 round barrel life?

 

[woods89]

Not sure which action you plan on, but it might be a good idea if you just have 2-3 barrels set up right off the bat.

 

[brocksw]

Not sure which action you plan on, but it might be a good idea if you just have 2-3 barrels set up right off the bat.

Tikka. That’s not out of the question. On a cartridge like this that first barrel would see a lot of playing around at the range collecting data anyway.

 

[Deleted member 16014]

I’d agree, but I have to see anything that confirms it. Perhaps my title is poor, but there’s also the 6 Saum as a tweener between the prc and UM. Trying to string together information that makes me confident I can get there with a prc and not smoke a barrel. Seems like once you go to the saum categories, barrels take a hit. So if it takes a saum case to get there I may just go the 6 cm route, push it harder, and live with the velocity it gets me.

You could go 6cm, alpha ocd brass, and lean hard on it. As long as you won’t be too bummed if you do come up a little short of your velocity of interest. More efficient and plug and play high-end brass, I guess just depends how much you want to tilt your odds of hitting the velo #’s you like. Fun to ponder and figure on it either way!

 

[BackofBeyond]

it would do it for sure. 600 round barrel life?

750 at least.

 

[pyrotechnic]

I don't have any experience with the 6 creed or the 6-prc. I have smoked a .243 barrel (1800 rnds) and am working on a second one now after a couple 6.5 creed barrels and a .260.

I don't think you will get those speeds with the creedmoor unless you run all the ksi. Perhaps with the 6-prc. The 6-prc seems alot simpler than the 6UM and you have more brass available than a 6 SAUM.

For me I would do 6 creed and just deal with whatever performance I get. Burning through a barrel figuring out a wildcat sounds like a shit time to me, and being able to find factory ammo if need be is a pretty big plus.

It sounds like you have a very specific set of criteria you want to meet and 6-prc would be the simplest way of getting there although I think that 3400 out of a 20" may still be a tall order.

 

[DFS]

I have a buddy that’s getting 3300 out of a 95 Berger 6 CM 24 inch barrel. I personally would go 6 creed but I am a poor reloader and any time I chase speed it doesn’t work out like I envisioned.

 

[brocksw]

750 at least.

That’s about in line with what I’m seeing guys report on the 6 saum. 700-750.

 

[DFS]

Drop down to a 22 creed and you would have no problems getting the velocity with a similar BC bullet. Been very easy to reload for.

 

[ccc23454]

me i would get the creedmore simply cause lapua makes brass for it, i dont think they make 6PRC brass(yet?)

 

[brocksw]

Drop down to a 22 creed and you would have no problems getting the velocity with a similar BC bullet. Been very easy to reload for.

Funny you mention that. I’m just starting to run numbers on that as well.

 

[DFS]

Funny you mention that. I’m just starting to run numbers on that as well.

Quickest way to get the barrel length and velocity mentioned. 77 lrx available I believe

 

[Carl]

I can’t see you getting the velocities you’re talking about at those barrel lengths in the CM without crazy pressure.

Hodgdon’s data for a 95 Berger (which should produce less pressure than the Barnes) has Superformance making 3300ish @ 24”, the best single base extruded powder is closer to 3200ish. ~60ksi so there’s a little room, but I’d expect to lose 100-150 fps from those numbers just on the barrel length.

I think the PRC should get you in the neighborhood, but might still not make it without some pressure. I’ve followed all the UM stuff myself. I think the PRC case probably gives up ~ 100 fps at like pressures with much simpler logistics. On a Tikka, if running factory mags, a 6-284 is an option too, it’s a whisker short of the PRC in capacity.

I was bored recently and did a ton of bench racing between 22CM - 6 CM - 6 PRC, all with optimized match bullets. I’m sure I’ll experiment, but the 6 CM seemed like the easiest easy button and was still carrying 1800 fps to 1000 yds or so.

 

[mtmuley]

Why not the 90 grain HHT? Or the 75 grain even. They tend to run faster than other bullets. mtmuley