6mm Magnum vs 6 CM +P

[B_Reynolds_AK]

The 6 UM and 6 PRC are the top tier 6mm cartridges at the moment. The external ballistics are great and those building them
are accepting of the sub 1,000 rd barrel life.

Defensive Edge +P seems to get mixed reviews. You gain up to 120 fps at the expense of less barrel life and throat erosion, which seems to be the main argument that people make against it.

I really like my 6 CM, with its AnTi X short action, standard bolt face, easy reloading and factory ammunition. As well as being able to spin on other .308 based cartridges such as 338 Fed.

If I was accepting of a hunting barrel with a shorter barrel life, why should I not just have a light contour 18" or 20" barrel spun up in 6 CM +P to be able to shoot 108-115g projectiles at around 3,000 fps, rather than go with a 6 Magnum? My heavier, standard 6 CM, barrel would be for training.

 

[wind gypsy]

A guy should be able to run 108s+ @ 2900+ with an 18" barrel standard creed. My retort would be, why not just keep using that and have another similar barrel ready to go and not worry about switching around at all?

For people shooting enough in varied terrain to stretch distances enough where the juice might be worth the squeeze I can see it. Since I don't see myself shooting in variable terrain enough to truly be competent beyond 500 yards I cant see having to dick around with swapping barrels, additional load dev, zero confirmation, etc being worth the squeeze but can see how it may be for others.

 

[ARK_Ginger]

At that point, why not 6-284?

 

[B_Reynolds_AK]

A guy should be able to run 108s+ @ 2900+ with an 18" barrel standard creed. My retort would be, why not just keep using that and have another similar barrel ready to go and not worry about switching around at all?

For people shooting enough in varied terrain to stretch distances enough where the juice might be worth the squeeze I can see it. Since I don't see myself shooting in variable terrain enough to truly be competent beyond 500 yards I cant see having to dick around with swapping barrels, additional load dev, zero confirmation, etc being worth the squeeze but can see how it may be for others.

Well I need to have another barrel spun up anyhow, as I want a lighter weight 6mm barrel. I definitely have the capability to stretch out my effective range in the environments I hunt in. Was considering going to a 6 Magnum, not only for increased range, but less wind drift.

Also, spinning barrels on and off is really easy at my reloading bench. I have a separate scope for hunting and each caliber, already set up in rings, so when swapping barrels they go back on the AnTi X already zeroed. I popped the ATACR 4-16 back on a couple days ago and immediately ran it out to 1180 yards with no shift in POI. This is a huge benefit of the AnTi X with its integrated rail and using Hawkins or NF rings, over any type of direct mount rings, ie. Talley or even Tikka's rail.

 

[B_Reynolds_AK]

At that point, why not 6-284?

Have not considered that. Will look at into it.
Is it still a short action though?

 

[Rjk300]

If the case has the room for the extra powder and you want more speed with the same components that you already have go for it. You would have to keep on top of the +p rounds vs the non so you don’t load a +p in a non +p chamber.


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[B_Reynolds_AK]

If the case has the room for the extra powder and you want more speed with the same components that you already have go for it. You would have to keep on top of the +p rounds vs the non so you don’t load a +p in a non +p chamber.


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[madcalfe]

do as you wish.
lots of people run 28 noslers and there known for shit barrel life.

 

[Ryan Avery]

I am all for the +P chamberings, but the accuracy of the three 6mm we have done was terrible. It could have been a coincidence, but I won't be doing it anymore.

 

[B_Reynolds_AK]

I am all for the +P chamberings, but for some reason, for the three 6mm we have done, the accuracy was terrible. It could have been a coincidence, but I won't be doing it anymore.

Thanks for weighing in Ryan. Sounds like it might be a gamble then. Might just stick with standard 6 CM, unless I go fully into the magnum realm. That'll be more tempting as UM continues developing more support for Tikka and the 6 UM, ie. Tikka mags, swappable bolt faces, in stock brass etc.

I'd like to continue using my HNT 26 chassis and having poly mags for Tikka that fit longer 6mm cartridges would be awesome.

 

[Shooter264]

RL26 and RL23 are your friend with creed cases. Both powders will offer as much velocity gain as a +p will give you with 4350 or similar burning powders.

 

[Dobie07]

A guy should be able to run 108s+ @ 2900+ with an 18" barrel standard creed. My retort would be, why not just keep using that and have another similar barrel ready to go and not worry about switching around at all?

For people shooting enough in varied terrain to stretch distances enough where the juice might be worth the squeeze I can see it. Since I don't see myself shooting in variable terrain enough to truly be competent beyond 500 yards I cant see having to dick around with swapping barrels, additional load dev, zero confirmation, etc being worth the squeeze but can see how it may be for others.

I’m not sure that’s accurate is it? From the research I did it seems most report 2900 is about the max to expect with a 20” barrel without going over pressure. This thread has some good real world input from folks running 6 creed with short barrels. That was what steered me towards a 6 PRC build with a shorter barrel as I wanted to be closer to 3100 fps with the 108’s and over 3000 with 115’s.

 

[Dobie07]

The other consideration is that you can always run a 6 magnum with a milder powder charge to get reduced recoil and then step on it when you want to, a bit more flexibility than running the creed near max to hit top end velocity goals. Whispers to @B_Reynolds_AK “come on, build a 6 mag… all the cool kids are doing it… ”

 

[Shooter264]

I’m not sure that’s accurate is it? From the research I did it seems most report 2900 is about the max to expect with a 20” barrel without going over pressure. This thread has some good real world input from folks running 6 creed with short barrels. That was what steered me towards a 6 PRC build with a shorter barrel as I wanted to be closer to 3100 fps with the 108’s and over 3000 with 115’s.

I’ve got quite a bit of experience with an 18” 6 creed and 42.2 grains of H4350 produced 2944 with the Berger 108’s. I don’t often look at reloading manuals but just for science hornady lists their max load for the 108 Eldm at 41.7 H4350. Given the conservative nature of reloading manuals and the longer bearing surface of the 108 Eldm, 42.2 is not over pressure. Every bbl is different for sure but I’ve ran that load in multiple 6 creeds w no pressure signs with any of them and multiple loadings on the brass

 

[Dobie07]

I’ve got quite a bit of experience with an 18” 6 creed and 42.2 grains of H4350 produced 2944 with the Berger 108’s. I don’t often look at reloading manuals but just for science hornady lists their max load for the 108 Eldm at 41.7 H4350. Given the conservative nature of reloading manuals and the longer bearing surface of the 108 Eldm, 42.2 is not over pressure. Every bbl is different for sure but I’ve ran that load in multiple 6 creeds w no pressure signs with any of them and multiple loadings on the brass

Certainly an interesting data point for sure. Seems like you have a barrel outperforming everyone else that posted in that thread with the same or longer barrels. Tough to say if they are running anywhere near max charge tho, may be backed off a bit. I think that’s kind of the point tho, in order to reach those numbers you need an outlier barrel and a load over published book max.

 

[z987k]

Have not considered that. Will look at into it.
Is it still a short action though?

It's as much a short action as the 6PRC or 6SAUM is. They really shine as mediums.

 

[eoperator]

I went through this same dilemma a couple months ago. The mixed reviews steered me away from a 6cm+p adventure to a 6prc.

20" 6cm will get to 3000fps with the right powder, 6prc should get 150-200fps over that. Is it worth it?

In my experience getting 2950fps from an 18" 6cm & h4350 would require a cheater pipe to open the bolt.

Being you have standard boltface anti and hnt26 a 20" 6cm seems like the easiest and cheapest.

 

[khuber84]

I’ve got quite a bit of experience with an 18” 6 creed and 42.2 grains of H4350 produced 2944 with the Berger 108’s. I don’t often look at reloading manuals but just for science hornady lists their max load for the 108 Eldm at 41.7 H4350. Given the conservative nature of reloading manuals and the longer bearing surface of the 108 Eldm, 42.2 is not over pressure. Every bbl is different for sure but I’ve ran that load in multiple 6 creeds w no pressure signs with any of them and multiple loadings on the brass

This is all rifle dependent. I have a Bart 18" 7.5tw 6cm on a Tikka, 105hyb with H4350 at 2950 with 42.4gr in lapua srp brass. There are ejector marks and intermittent bolt lift present. To get away from ejector marks and maintain good accuracy, I had to drop down to 2860fps. I went back to 95tmk at 3080 with H4350, no pressure here.

 

[B_Reynolds_AK]

Thanks everyone for the experienced input.
I’m going to stick with a regular 6 CM for now and experiment with powder and charge weights to see what I can get out of it safely.

One more thing though. I’ve seen some of the guys that are pushing velocity on the 6 CM using SRP’s. I’m currently using Fed. 210 LRP’s. I’ve read the reports of maybe having more reliable ignition in cold weather with LRP’s, but do the Small’s let you build a bit more pressure and velocity?

 

[khuber84]

Thanks everyone for the experienced input.
I’m going to stick with a regular 6 CM for now and experiment with powder and charge weights to see what I can get out of it safely.

One more thing though. I’ve seen some of the guys that are pushing velocity on the 6 CM using SRP’s. I’m currently using Fed. 210 LRP’s. I’ve read the reports of maybe having more reliable ignition in cold weather with LRP’s, but do the Small’s let you build a bit more pressure and velocity?

Primer pockets generally hold up a bit better in srp when loading warm. I've had a few hang fires in sub zero temps with lapua srp brass with slow powders like rl26 in my 22cm. Lapua uses small flash hole, Alpha uses large flash hole, haven't had the same issue with alpha brass. Moving to a faster burning powder in the lapua brass remedied the issue but did lose some velocity.