Cartridge choice....

[Lapuatom]

I am trying to narrow my selection down and am wondering what you would do and why?

I have a NEW (given to me by a friend) heavy 17 contour 29" 6mm 1:7.5 twist 5R Bartlien barrel waiting on a future build. It will go on a 700 trued short action. It doesn't have to be a repeater and would consider running it as a single shot which would allow a couple of the slightly longer cartridges I mention below.

The gun will be a LOW volume varmint gun (coyote, prairie dogs at long range) with the possibility of setting up in an elevated box stand for the occasional white tail. I would like to get 2000 rounds out of it.

The cartridges I'm considering:
6mm Creedmoore
.243 AI
6mm REM AI
6mmx.284

Thanks for your input.

240 Gibbs wilcat. Brass is easy to make (one step), pushes 75gr Vmax just shy of 4000fps. A really unique and old cartridge.

 

[DocDoc]

The best for 2000 rounds would be a 6mm BR. It is historically one of the better 600 yard bench rounds. 6mm Creed will give more speed, but lower round count. There is great brass available for both - Lapua, ADG, ?

 

[lancetkenyon]

I push a 105 Hyb in my 24" 1:7.5" suppressed 6CM @ 3151fps w. H4350, 2gr under max. A 29" tube should get you 3250ish pretty easily. That is plenty for long range low volume shooting. But not sure if 2000 would be doable.

 

[mmgravy]

Despite the lack of love here, the 6 Creedmoor (note spelling) is one sweet little cartridge. A 7.5 twist is about perfect......

 

[Lowlander]

I've been thinking of building a 6RemAI, but only because I have brass for it. I also have 257 Roberts brass I can neck down. You can also make 6Rem brass from 7x57. I'm new to the cartridge so, I'm still learning about it at the moment.

I rolled around this 6mm conundrum for a while. I'm still on the fence about it to be honest, I have a 22BR that I load for. So I have 6BR brass on hand too. Thought about doing a 6BR or even a Dasher.

Too many good choices in 6mm, lol. I guess it all boils down to what works best for you? I've built several rifles with intentions of them having a different purpose than they end up having once built...

 

[demonjigger]

If you want speed, 6mmSLR. Easier to make brass for than the AI. It might make 2k, mine made 1800 rounds and I pulled it and made it into a fire forming barrel for my 6mmBRA.

If you want barrel life, I would do the BR case variants or maybe a GT. They should go over 2k easily. Less powder and easy to load for. Tons of information on them.

Have fun.

 

[Scott Wagner]

Have a 26 in. barrel 6mm Creedmoor. Great choice for LR p-dogs.

 

[Junkysavage]

I doubt it matters but all three stores I went by today had 6cm factory rounds and nothing else

 

[PartsJr.]

Thank you for the reply everyone.

I'm not overly hung up on getting 2000 rounds out of it, but more is always nice. I realize the trade off of velocity vs barrel life.

I don't want anything smaller than the 6CM. I sense there's not a lot of love for this round but it has a lot going for it. No, I'm not going to use it for elk hunting.

I currently have a more or less shot out 1:12 .243ai so I'm kinda leaning that way. I could possibly fire form my brass in that barrel and swap out for my new barrel. I also have a couple of sets of dies.

A friend recently built his 3rd 6ai and has the reamer for it as well. I just wish there was some better or more brass options.

Those of you that have experience with these rounds:
6CM
.243ai
6ai
6x284
Do you see any of these holding an accuracy edge over the other? I think some cases might be more efficient but I'm not sure about one being more inherently accurate.

What is a reasonable expectation for velocity w/105 to 115 gr bullets? When I looked in the Berger reloading manual the 6x284 was not all that fast compared to the standard 6mm.

What can I reasonably expect for barrel life with the above rounds?

Thank you for sharing your knowledge.

 

[JMW67]

if you want decent 6mm brass I have found it best to use 7x57 and neck down and turn its a pain but you can have good brass this way This is why I suggested the 6-284 simple neck down of top end 6.5-284 and you are shooting

 

[sierracharlie338]

6gt cause I'm drinking the gay tiger cool aide or 243ai

 

[1mechanic]

I was just doing research today on 243 wildcats and came across a 243 br-k which has a long neck
with about the same capacity of a straight 243. Was thinking it might help reduce throat erosion and
promote better barrel life. Been trying to find out more information but there doesn't seem to be much on the web about it.

 

[Goldengun]

243AI. Better/more ammo options.

 

[Cuz]

6-47 lapua?