6x45 (6mm-223) AR build

[suzukisam]

Got the itch to build a new AR. Considered a big bore (450,458) but finally settled on a 6x45. I load for a couple 223/556 rifles, and a couple 6mm as well so I have everything needed for this build.

I was hoping to get some feedback from anyone who is running an AR in 6x45. I just ordered a satern 20" stainless and rcbs small base dies. I would like to keep the topic on this particular caliber.

My first question is which buffer would be best?

Rifle has system. 750 has block size

 

[adcoch1]

Always wanted one. My uncle used one to knock off a few deer years ago. It was a nice little shooter with a 20" rifle length gas system. Maybe thats what I'll build next...

 

[cfullgraf]

I have a 6x45 AR-15 with a 20" barrel and have a standard buffer system in the gun. It functions well.

I've really not been impressed with the 6x45 in the AR-15 platform. The case capacity does not do the 6mm bullets justice in an AR-15 platform.

It is just my experience and opinion.

 

[Oldschool shooter]

Why not the 6mm ARC? It looks to be a solid performer.

 

[gotboostvr]

I came to the conclusion that there's just not quite enough case capacity to push 6mm bullets of much weight to the velocities I'd like to see. A 20" barrel will help, sticking to light for caliber bullets will as well.

What are your goals for this build?

 

[LoonWulf]

I had a 6x47, but in a bolt gun with a coal of 2.4-5. If sticking with 85s or 90s the 6x45 in an AR should do fine.

 

[Walkalong]

A bolt gun can beat the 6 ARC any day, but the whole idea is performance in a standard AR package. Seems to be a good answer there.

 

[horsemen61]

A bolt gun can beat the 6 ARC any day, but the whole idea is performance in a standard AR package. Seems to be a good answer there.

if CZ makes the 527 in 6mm arc I’ll have one of them as well so I’ll have both an ar and a bolt action!

 

[army_eod]

How would it compare to 6.5 Grendel?

 

[Varminterror]

A bolt gun can beat the 6 ARC any day, but the whole idea is performance in a standard AR package. Seems to be a good answer there.

To be fair: A bolt gun in 6 ARC will “beat” the 6x45 in a bolt gun any day also. The 6x45 can ramp pressures in a bolt gun to exceed the lower pressure AR platform across the board, as can the ARC. Once you’re at the same pressure standard, there’s no replacement for displacement.

Bolt 6 ARC > bolt 6x45 > AR 6 ARC > AR 6x45

 

[Varminterror]

How would it compare to 6.5 Grendel?

6x45 in a gas gun will attain similar speeds to the Grendel, but with a ~20-25grn lighter bullet.

 

[suzukisam]

Thanks for all the replies! I'm running an LR-243 (308) with a WOA medium contour barrel. So even though the case capacity is low, I'm not in need of 243 velocities, I have about 1k various 6mm projectiles. I load 223 and 243, so this is like free ammo .

I don't have any experience with the 6mm arc

Mostly planning on shooting whitetail, hogs, prairie dogs. My son is addicted to his 300 blackout bolt rifle. Might try to get him to shoot this a little

 

[suzukisam]

So I went ahead and ordered a carbine spring and buffer and will be putting a collapsible stock on it.

 

[Armorer 101]

I have owned a 6 TCU and now am running the 6 Mongoose in an 18”. The Mongoose and TCU are both based on the 223 case. You will find a good bit of information about the little 6mm cartridges on the Mad Dog Weapons Systems forum.
The 6x45 is simply the 223 necked up, The Mongoose is basically the same capacity using a slightly shortened case, body blown out and a 40 degree shoulder, for easier feeding of heavier bullets in the AR mag. The little 6s like H-335 and W-844 with 80-105 pills. My 1-8 twist SS 18” shoots .3 inches with the 80s at 3,000 fps using 844. So far it has dispatched a song dog at 100, DRT. It is a nice little cartridge, like the 6x45, a bit loud, but accurate and deadly.
If you want a light, easy to handle 6mm the 6x45 is a fine cartridge. Due to the case capacity you should be using a mid length gas system.

 

[suzukisam]

I have owned a 6 TCU and now am running the 6 Mongoose in an 18”. The Mongoose and TCU are both based on the 223 case. You will find a good bit of information about the little 6mm cartridges on the Mad Dog Weapons Systems forum.
The 6x45 is simply the 223 necked up, The Mongoose is basically the same capacity using a slightly shortened case, body blown out and a 40 degree shoulder, for easier feeding of heavier bullets in the AR mag. The little 6s like H-335 and W-844 with 80-105 pills. My 1-8 twist SS 18” shoots .3 inches with the 80s at 3,000 fps using 844. So far it has dispatched a song dog at 100, DRT. It is a nice little cartridge, like the 6x45, a bit loud, but accurate and deadly.
If you want a light, easy to handle 6mm the 6x45 is a fine cartridge. Due to the case capacity you should be using a mid length gas system.

That's great info thanks. As far as the mid length gas system I could literally find one company sellng barrels. Luckily satern has great reviews. I'm hoping I like it as much as my WOA SDM barrels.

I love 6mm in general, I've been wanting to try one for a while.