Considering a rebarrel to 6x45. Opinions wanted

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steveNChunter

New member
I've got a Ruger M77 MKII target in .223 I've been trying to figure out what to do with for awhile.

The factory barrel has a 1:12 twist, limiting me to around 55-60 gr bullets or lighter. I thought about just putting a 1:7 .223 barrel on it, but if I'm going to put the money into fitting a new barrel, I want to have something a little different. I've pretty well decided on doing a 6x45 (aka 6mm-223). I've got plenty of .223 brass and it's easy to come by, and it's just a simple neck-up to make 6x45 brass out of it.

I want to do a magnum or semi-bull profile barrel, and I'd like to know what length is sufficient for getting most of the velocity out of the cartridge, but no longer than it needs to be. I'm thinking that's somewhere around 18-20" but I'm not sure. I'm also considering what twist rate to get. I'd like to shoot the 105-107 grain bullets, so I'm thinking a 1:8 would work well.

I'd just like to hear what y'all think of the idea, and what barrel length/twist rate would work best.
 
Too many technical questions for my level of expertise in 6 mm chambering. However, IMHO the only good argument I can think of for a 223/5.56 bolt action rifle is inexpensive ammo, not the cartridge's utility.
 
I reload so I'm not really concerned with ammo prices/availability. If I have 223 brass then I have 6x45 brass, just one run through a 6x45 sizing die and it's good AFAIK.

The twist rate/barrel length questions are just because I have never owned or loaded for a 6x45. I hope to hear from someone who has, and might know what I need.
 
My biggest question is do you want to run it as a single shot rifle or from the magazine? While you'll get a velocity increase with a longer barrel, I doubt you'll see much benefit going longer than a 24" barrel. While I don't run a 6X45 but I do run a 6X47 the .222 Remington Magnum version with a 20" barrel.


105 to 107 grain bullets for the 6mm are really, really long. There just isn't enough magazine space to run a bullet like that and have any kind of decent velocity. Just like the 90 grain bullets give .223 shooters fits keeping them at magazine length in an AR magazine. Plus with certain bullets you might be seating the bullet ogive past the case mouth to get them to fit in your magazine.

If you run as a single shot then you can probably run the bullets but I don't know what kind of speed you'll get. I'm guessing you'll have a hard time reaching 2500 fps even if you have a 24" barrel. However, you'll have to throat the new barrel accordingly for a single shot, and when you go to lighter bullets there will be massive jump to get to the lands. So that could affect accuracy with lighter bullets, and that is where I think these smaller cartridges shine.

There are a ton of great light weight bullets out there that will get you to at least 500+ yards. The 6X45 just isn't a 1000 yard cartridge, and I don't think you'll enjoy trying to make it one. 55-90 grain bullets is where I'd stick with this cartridge, 100 grains max with standard cup-and-core bullets. VLD's probably in the 80 grain range if you want to run at magazine length.
 
You could probably to to a 40 inch barrel before noticing any velocity reductions. But a 26 inch 1:8 twist one's probably the best compromise regarding usability and maximum velocity as well as accuracy with heavy bullets.
 
Thanks guys that's the kind of advice I was looking for. My mag box has a spacer in it that could be removed/modified to accommodate longer bullets, but I get what Taylorce1 is saying about the heavier bullets not being the best idea. So maybe a 1:9" twist and staying 100gr and under is more what I need. As for length, I'm not that concerned with getting every last fps out of it so I'm still thinking 20" or so.
 
I have the spacer as well in my X47, but then your still talking about a new follower, and possibly the magazine not retaining the cartridge because of how far back you moved it. I know in my Stevens if I pulled the spacer then the lips on my magazine wouldn't have as much of the cartridge body to hold onto, I don't know how your Ruger would fare. I've looked into it as well, but decided 60-75 grain bullets are all I really need to shoot.

Then you still have the issue of the throat, and the jump for when you get back to lighter bullets. IMO if you really want to run long bullets and keep around a .223 OAL, open the bolt face and run the 6mm BR or a wildcat 6mm Grendel/AR. Both should be just the ticket for using the heavier bullets without sacrificing powder room for seating to magazine length.
 
MWM, I've considered the 6 tcu, but it's basically just an improved shoulder on the 6x45 case. It seems like a lot of fire forming for not much gain. Certain cases benefit more than others from sharpening the shoulder angle, but I just don't see this one as being worthwhile. That doesn't mean that I'm right though. I'd rather get the barrel a couple inches longer if I'm that desperate to get a little more velocity
 
I'm new to the world of the 6x45 myself having just acquired a 16" AR upper. After studying the round, bullets, and mag length restrictions I came to the conclusion the 6x45 shines with bullets from 55-90g. Barrel length on a handy AR should be 16-20". Twist should be 1/9". On a bolt rifle a 22-24" barrel will get you more velocity without too much loss of handiness. Anyway these are my conclusions. I think it is a handy, efficient round with capability/utility for varmints, predators, and whitetail deer.
 
Mine will be used for mostly targets and maybe deer or coyotes. IMO the 6x45 is an almost ideal balance of low recoil, inherent accuracy, and capability on game deer size and smaller.
 
Mine will be used for mostly targets and maybe deer or coyotes. IMO the 6x45 is an almost ideal balance of low recoil, inherent accuracy, and capability on game deer size and smaller.
Yesterday 07:07 PM
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exactly the reason for the 6.8 chambering in my custom 700 ( wish my SPC - 2 reamer would get here... was in stock, until the week before I went to order it, then sais out 6-8 weeks :o )

anyway... looking forward to see how your build turns out:)
 
I see. I already have a ton of .223 brass and it's easy to come by so I want to stick with the .223 parent case. I have read about people making a .257 and 6.5/.223 wildcat, but they never got very popular. I think the 6x45 hits a "sweet spot" with the .223's case capacity. Plus there are a lot of good 6mm bullets out there between 80-100 grains that have a pretty good BC and will still allow me to seat the bullets out to the lands while still fitting in my magazine. I realize from a hunting standpoint it's inferior to the .243 or 6mm rem at longer ranges but short range hunting and benchrest shooting is where it shines. If I did go with a different parent case I would most likely have the bolt face opened up and do a 6 PPC
 
I have a few 6mm wildcats and have loaded for a friends 6 x 45 ar upper. I now have rifles in 6mm from the 6 x 47 to the 6 - 300 SWM. These are just my thoughts on bullet for the 6 x 45. Heavy for cal. bullets are best for long range shooting, but the 6 x 45 is not a long range round and of no real advantage in the 6 x 45, especially if you going to feed from a magazine.
 
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