Home Forums Hunting & Shooting Custom Rifles & Wildcats 6X45 AI, 6X47 AI, or 6X204?

I'm looking to rebarrel my current 6X47 and trying to decide if I want to stick with the chamber or not. The reason for the rebarrel is I want to go from a 12 twist to an 8 twist. I need new dies as well as my current set of Hornady dies overwork the brass and I have to anneal every other reload. So I figure I'm pretty much starting from scratch, I might as well look at my options again.

Colorado law requires a 6mm bullet minimum for big game or I'd just run a fast twist .223/AI. I've taken deer, pronghorn, coyotes, an prairie dogs with my current set up mainly with 70 grain NBT bullets. However 70 grain bullets are the heaviest bullet I can get to shoot accurately from my slow twist barrel.

.222 RM brass has been a PITA these last couple of years to replenish and there is no short supply of .223 or .204. I'm thinking 20-22" barrel finishing .600 at the muzzle. Throat it for 105 grain A-Max at magazine length and hope for 2600 fps. Is this a pipe dream or not?

I'd go 6x47 with Redding dies and necked down Lapua brass. 90 or 105 scenars.

I can't use the 6X47 Lapua it doesn't fit my bolt face, which is .384". The original 6X47 cartridge is based of the .222 Remington Magnum case and roughly has the same case capacity as the 6mm PPC.

Brian Pearce did an article (in Rifles' Varmint edition) a few years back on the 6x204. I don't think it was twisted as tight, but he was getting decent velocity out of the the lighter bullets out of a shorter barrel. I had thoughts of doing a rebate of a m700 with that chamber twisted 1-8 with an eye towards deer and coyotes. Haven't gotten that off the ground though.

Kaiser Norton

Have you thought about a 25-204?

I am doing a 6x45 on a Rem M7. 1-8 20". Makes it easy.

I have the Hodgdon annual magazine from 2012 IIRC that has a good article on the 6-204. I'm just more worried about getting good neck tension on the heavy 105's. I guess I need to make some dummy rounds at max length for reliable feeding from my current rifle. That'll will probably let me know which case is better suited for the longer bullets.



I like quarter bore rifles but they really lack bullet options when comparing to the 6mm options. The 6mm bullet will just keep velocity and energy longer than a .257 caliber bullet can.


That is easy and may be the way I go if I think I can get 2600 fps minimum with a 105 A-max.

I got 2,700 with 90 Scenars in mine but only had it 1:9, so no idea on 105's. 1:8 20" Montana will be next if I do another.

90 grain Scenars are definitely a viable option at that speed. What chamber are/were you running?

6x45, BR4's, H335, moly. Flies like a 308/175SMK without the recoil.

6mm TCU is one I'm going to try soon with a 105gr. I have a friend that runs one with 70gr with awesome results.

That's the kind of performance I'm looking for, punching paper and ringing steel at respectable ranges. Then still have something that weighs in the <8 lbs all up and Colorado legal for hunting deer, speed goats, yotes, and shooting PD's.

Have a Montucky based 6x45 in the works,wearing a 1-8" Bart' duped in contour and lopped at 18.5". 105's are the only things of interest to me and will be the express fodder,with an inkling that 2500fps will be plausible.

6x MQ being a given and 40+ Mils pending on the erector being factored in the equation,as per the OEM 223's spout coughing up 42.7 Mils from it's 225yd zero.

It'll be a Handy/Dandy Wrecking Ball...destined for FAME.(grin)

Hope to have it this week.

I would love to hear the results you get. I don't think I want a barrel shorter than 20" though. I shoot a lot of PD's in current form with the 70's so it's running a VXII 4-12X40 LRD. However, if I can get 105's the speed I want I'm going to give your 6X chicken a try. What do you think DD base and rings or give a 20 MOA rail a try?

To me, the 6x204 would be the easiest route to a familiar setting. What is there not to like?

For some it could be having a stash of 223 brass to use. That's the only thing I can think of?

I'm anxious to see his opinion after shooting the 6 next to the 223.

Lake City and Lapua. Nuff said......

Magazine length and seating depth will be the biggest issue with 105 grain bullets and the 204 case. Where the bearing surface of the bullet aligns with the case neck will be the deciding factor as I'm still wanting a repeater. Luckily I'm not using AR mags and restricted to 2.25" COAL.

What action are you building on?

I would think just about any 223 receiver can have about as long of a mag box as you might want. You might have to massage a spacer or two, maybe shorten a bolt stop too, but the room will be there.

Stevens 200 or a M700 have both donors available. Maybe both who knows, but I was thinking of doing a 1:7 .223 on the other. Money and time will tell.