6mm: x223, x45mm, x45AI, tc/u, x47mm, x47ai, x204, x204ai, raptor etc, etc

[johnfred1965]

I have been gathering information on these cartridges, and all I can find is this one is a "hair" bigger, "a little bit faster", same as this or that. Here are some things I think are correct, and if anyone actually has information to support or deny these statements, I would like to hear them.

1.the 6x45ai is close to the 6tcu with similar 40 degree shoulder and similar case and neck length.
2.the 6x45 and the 6x47 have nearly the same body, the extra 2 mm coming from a longer neck.
3.simply necking up the 204 give you a 30 degree shoulder and 204 case taper.
4.the 6x204ai and the 240 raptor are similar due to the short neck, straight taper and 38 to 40 degree shoulder.
5.the 6x47ai is similar to the the 6tcu but with a longer neck.

If can find a reamer and a barrel maker, I would prefer the x204ai or gary reeder's 240 raptor for absolute max volume of these small cases. If any of these assumptions are wrong, please enlighten me. I am looking to build a 20-22" encore barrel.

 

[swd]

I've had a few 6x45's. The great thing with them is unlimited brass availability. Very high in fun factor! One of them is my go to rifle for the small black tail deer we have around here.

The 6x204 and it's variants would have the most case capacity. One thing to consider is dies. You can take stock 204 bushing dies and open up the neck slighly have 6x204 dies without the custom die price. The other thing is all these cases with the small rim diameter don't take a ton of pressure. You can kill brass real fast if you get too ambitious. I came home from a steel match with a bunch of dead brass with one firing one it. No matter what you do they arn't a 6BR. For a short while it will look like you can get that kind of speed and then POOF there goes the primer pockets while the primers still look good. Live and learn, lol.

 

[RussellJ]

I've had a few 6x45's. The great thing with them is unlimited brass availability. Very high in fun factor! One of them is my go to rifle for the small black tail deer we have around here.

The 6x204 and it's variants would have the most case capacity. One thing to consider is dies. You can take stock 204 bushing dies and open up the neck slighly have 6x204 dies without the custom die price. The other thing is all these cases with the small rim diameter don't take a ton of pressure. You can kill brass real fast if you get too ambitious. I came home from a steel match with a bunch of dead brass with one firing one it. No matter what you do they arn't a 6BR. For a short while it will look like you can get that kind of speed and then POOF there goes the primer pockets while the primers still look good. Live and learn, lol.

+1 on the 6x45

 

[Kiwi Greg]

I build the 22 Terminator, 22-204 as well as its little sister the 17-204 & bigger sister the 6-204.
They all go extremely well, dies are easy enough, brass is plentiful & they are exceptionally accurate.
Considering you are only using around 30 grains of powder they punch well above thier weight & suppress nicely.

 

[ImBIllT]

I have been gathering information on these cartridges, and all I can find is this one is a "hair" bigger, "a little bit faster", same as this or that. Here are some things I think are correct, and if anyone actually has information to support or deny these statements, I would like to hear them.

1.the 6x45ai is close to the 6tcu with similar 40 degree shoulder and similar case and neck length.
2.the 6x45 and the 6x47 have nearly the same body, the extra 2 mm coming from a longer neck.
3.simply necking up the 204 give you a 30 degree shoulder and 204 case taper.
4.the 6x204ai and the 240 raptor are similar due to the short neck, straight taper and 38 to 40 degree shoulder.
5.the 6x47ai is similar to the the 6tcu but with a longer neck.

If can find a reamer and a barrel maker, I would prefer the x204ai or gary reeder's 240 raptor for absolute max volume of these small cases. If any of these assumptions are wrong, please enlighten me. I am looking to build a 20-22" encore barrel.

At 20-22" the difference in case capacity will make little to no difference. Your determination should be made based up what matter most to you, brass availability/ consistency or neck length. If you want a long neck for ease of reloading, use the 6x47. If you want the best brass on the market without sacrificing availability, go with the 6x45 and use Lapua .223 Match brass. If you want long brass life, AI the above choices. Another positive for the 6x45 is the abundance of affordable dies. Going to an AI or the 6x47 will raise the price of new dies and decrease the availability of used dies .

 

[ImBIllT]

I've had a few 6x45's. The great thing with them is unlimited brass availability. Very high in fun factor! One of them is my go to rifle for the small black tail deer we have around here.

The 6x204 and it's variants would have the most case capacity. One thing to consider is dies. You can take stock 204 bushing dies and open up the neck slighly have 6x204 dies without the custom die price. The other thing is all these cases with the small rim diameter don't take a ton of pressure. You can kill brass real fast if you get too ambitious. I came home from a steel match with a bunch of dead brass with one firing one it. No matter what you do they arn't a 6BR. For a short while it will look like you can get that kind of speed and then POOF there goes the primer pockets while the primers still look good. Live and learn, lol.

I've run 20 reloads with flat Fed 205M's in a .223AI with Winchester brass. Never lost a primer pocket. What brass and primers are you using?

 

[swd]

I've run 20 reloads with flat Fed 205M's in a .223AI with Winchester brass. Never lost a primer pocket. What brass and primers are you using?

Winchester, Federal, LC. There was a time early on I was trying to push 95SMK's too hard with H4895 which can also be an unforgiving powder. 2950 from a straight 6x45 with 95's was asking too much but about 2800 in a long barrel is doable.

 

[johnfred1965]

I've run 20 reloads with flat Fed 205M's in a .223AI with Winchester brass. Never lost a primer pocket. What brass and primers are you using?

If I go with a 204 variant, I already have 500 brand new brass (Win) that I never had to load for my 204. I have buckets of 223 brass, but nothing new. I would hate to buy new brass with all that laying around. Since I already have the 204 dies, it shouldn't be a problem to drop in a 6mm bushing.

 

[ImBIllT]

If I go with a 204 variant, I already have 500 brand new brass (Win) that I never had to load for my 204. I have buckets of 223 brass, but nothing new. I would hate to buy new brass with all that laying around. Since I already have the 204 dies, it shouldn't be a problem to drop in a 6mm bushing.

I was asking because the guy claimed that the small cases lost primer pockets easily. That doesn't jive with my experience.