# 7mm in .223 Brass



## t-tung (Nov 13, 2005)

Watching this video, I started wondering how hard it would be to resize the brass for a 7mm bullet instead of .30 cal and then use some popular 300BLK loads as a starting point to load some 7mm rounds for my AR. The .284 bullets I've been looking at have a better BC in the 100-150gr range than the .30cal bullets. I'd like to be able to use a regular AR receiver, .223 bolt and mags with a 7mm bullet. Not looking for long range petformance; 200-300yds in. Yeah yeah...6.8SPC, 6.5Grendel, there's other rounds out there... I like 7mm; 7-08, 7mag etc. 
So how hard would it be to get set up to load what I've described?


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## REEL CRAZY (Dec 21, 2005)

Should not be to difficult. Look up 7 TCU. I'm pretty sure Midway sells the brass and dies.


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## t-tung (Nov 13, 2005)

Looking into the 7TCU, most guys are shooting this round out of a 10" pistol. You'd think you could get a bit more velocity out of a longer barrel but one guy tried this round out of a 21" barrel and lost 300-400 fps compared to what others were getting out of a 10" bbl. Might be a good round for an SBR/Can build ive been wanting to do.


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## horned frog (Nov 9, 2008)

Making the ammo would not be too difficult. Reaming a wildcat chamber might not be a big deal either. Finding a 7mm bore rifled barrel for an AR-15 might be a challenge.

300 Blackout is close enough.


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## REEL CRAZY (Dec 21, 2005)

There are plenty of 7mm AR barrels out there or have one machined out of a 7mm blank.


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## Ernest (May 21, 2004)

At 200 or 300 yards, the BC really does not matter. 

The benefit of some of these wildcats is cheap .223 brass as the parent round. Beyond the cheap brass angle, the PPC based rounds (like the Grendel) or even the 6.8 beat it hands down. Quite simply, there is inadequate powder volume in the .223 to push a 6.5 or 6.8 or 7mm at modern velocities. 

For short barreled, short range, or suppressed stuff, why recreate the wheel here? The .300 Blackout is where its at. 

But, don't use .300 Blackout load data for a 7mm in a .223 case. The larger bore diameter of the .300 allows it to push larger/heavier bullets at the same speed as a 7mmx223 with lower pressure.


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## t-tung (Nov 13, 2005)

Ernest said:


> At 200 or 300 yards, the BC really does not matter.
> 
> The benefit of some of these wildcats is cheap .223 brass as the parent round. Beyond the cheap brass angle, the PPC based rounds (like the Grendel) or even the 6.8 beat it hands down. Quite simply, there is inadequate powder volume in the .223 to push a 6.5 or 6.8 or 7mm at modern velocities.
> 
> ...


Why? Same reason some guys put 4BT's in Jeeps instead of a regular ol 350... Something different... I just like the 7mm bullets and have a few boxes that I haven't had reloaded for my other 7mm rifles. I headshot pig is going to be no more dead with a 6.8 or 300 than it would with a .223. There's no practical reason for me to load something strange but I think it would be cool. 
You've got me thinking though... How about a shortened 7x30 Waters? Same .30 Remington parent case as the 6.8, just a little bigger projectile. Use a 6.8 bolt and mags with a one-off barrel. It could be a happy medium between the 6.8 and 300BLK. One gripe about the 300 subsonic rounds is you have to run a pistol-length gas system and can (or so I read). Take the can off and you've got a single shot AR. I don't know, just brain-storming.


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## KingIX (Nov 16, 2013)

you are wrong about the 300blk.. while a pistol length gas system functions better a carbine length will work on a barrel at least 16".. If the gas port is the correct size it will function subs and supers with or with out a can. 

the problem with 7mmtcu is over all length in the Ar you have to have it fit. the over all length would limit you to running 110-130gr bullets... so now you have a round with less powder and the same wait bullet going down range as a 6.8spc 
the difference between a 6.8 and 7 is very little as you know
and since you dont reload does making everything 7mm make sense yet...

Now on a side note If you wanna do somthing just to be different Lets put a 7mm in a 6.8 case.. run a 6.8 bolt and mag and have a barrel made
but here is the question how much is being that much different worth to you. the weapon would be almost the same as the 6.8 balisticlly 

its all about money...
maybe seeing this in black and white is better then hearing it on the phone


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## Bird (May 10, 2005)

t-tung said:


> ...One gripe about the 300 subsonic rounds is you have to run a pistol-length gas system and can (or so I read). Take the can off and you've got a single shot AR. I don't know, just brain-storming.


Not true. I run a carbine length gas tube on my M4 300blk and have no problems running subs with or without a can. Realistically, there is little advantage to running subs without a can unless you are shooting under the house/in the back yard for minimal noise. Even then there's a pretty good pop without the can.

I think a 7mm bullet in a .223 case would be a fun load to develop in an AR platform. Wouldn't be a good candidate for a sub load but would make a good super load in a 139/140 grain bullet.


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## KingIX (Nov 16, 2013)

Bird said:


> Not true. I run a carbine length gas tube on my M4 300blk and have no problems running subs with or without a can. Realistically, there is little advantage to running subs without a can unless you are shooting under the house/in the back yard for minimal noise. Even then there's a pretty good pop without the can.
> 
> I think a 7mm bullet in a .223 case would be a fun load to develop in an AR platform. Wouldn't be a good candidate for a sub load but would make a good super load in a 139/140 grain bullet.


2 things.. be careful with sub rounds as many dont expand with that low of fps
so over penetration can be an issue

And you couldnt load a 140gr round in a 2236 case for a AR
as the overall length would not fit into the mag. While this
hasnt been tested by me personally but the research I have seen says 120gr max
due to powder load and overall length ...


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## Bird (May 10, 2005)

KingIX said:


> 2 things.. be careful with sub rounds as many dont expand with that low of fps
> so over penetration can be an issue
> 
> And you couldnt load a 140gr round in a 2236 case for a AR
> ...


I'm chunking 220 grain round nose bullets and 220 grain HPBT's in my 300 blk subs. Neither will expand at sub velocities but the bullets while stable in flight, tumble on impact causing a lot of mess inside.

You're probably right. I only considered the fact that I shoot sub sonic rounds only in my 300blk. No issue stuffing a 1.487" long 220 Sierra match king in there over 10.5 grains of A1680. A 140 grain spitzer boat tail 7mm bullet in a 223 case loaded for super sonic, would likely be a compressed load. If loaded to max magazine length and some calculated amount of reduced powder charge, it should fit.

In any event, I hope the OP wildcats something and keeps us posted...


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## KingIX (Nov 16, 2013)

I can not confirm the 7mmtcu load for an Ar
I just read a few places that stated 120 was max
for the Ar mag... now could you go 140 and drop
the powder load yes but then you are not gaining
anything
7.62x40wt would be a good load to run if he wants
somthing different

I run my 195gr over 8.5 gr of lilgun in my blk
and unique powder in my handi and soon my model 700

I have told the op multiple times to get a blk and be done
with it but he wants to use 7mm since thats what his bolt gun is
and wants the same bullet size
granted the op doesnt load and its not like he has tons of extras laying around

But I will force him to create a cool wildcat 
thats what friends are for


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## JimG (May 2, 2005)

It's been done a lot. Google 7mm TCU AR. Lots of data out there. Sounds like a neat combo!


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## Bantam1 (Jun 26, 2007)

One of the manufacturers is playing around with a 7 x 40 round for the AR platform. I can't remember where I read it, but it does exist in the development stages anyways.


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## horned frog (Nov 9, 2008)

7mm TCU is about 1/4 inch longer than .223/5.56 or 300 Blackout. Doubtful it will fit in standard AR receiver and mags as OP desired. 

7mm bullets will be longer than .308 bullets of equal weight. The increased ballistic coefficient will be gained at a compromise of powder capacity (velocity) and frontal area of the bullet on impact (makes a smaller hole) when compared to the already existing 300 Blackout.

Please post up results if this wildcat is created and works in the AR. I'm all about being creative. The 300 BLK is "almost" the same thing, only a lot more practical.


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## KingIX (Nov 16, 2013)

horned frog said:


> 7mm TCU is about 1/4 inch longer than .223/5.56 or 300 Blackout. Doubtful it will fit in standard AR receiver and mags as OP desired.
> 
> 7mm bullets will be longer than .308 bullets of equal weight. The increased ballistic coefficient will be gained at a compromise of powder capacity (velocity) and frontal area of the bullet on impact (makes a smaller hole) when compared to the already existing 300 Blackout.
> 
> Please post up results if this wildcat is created and works in the AR. I'm all about being creative. The 300 BLK is "almost" the same thing, only a lot more practical.


The 7mm tcu does fit but the loades are limited
the load I have thought about was a 7mm in a 6.8spc case
increased case size, more load options, mags and bolts
everywhere and minimum stretching the neck

While I dont think it will be all that better you should be able to push
a 7mm a bit faster as the round would allow a little more
powder behind it.... still not a fan of the idea but the op
has me thinking about it alot


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