I was thinking about getting a 6mm223 upper but I'd like to know if any one had any problems issues. Good bad?   I like the idea but  is it worth it or should I just get a 6.8 SPC.  

Quoted: I was thinking about getting a 6mm223 upper but I'd like to know if any one had any problems issues. Good bad?   I like the idea but  is it worth it or should I just get a 6.8 SPC.

6mm223 ?

6mm is bigger than 5.56mm (.223)...never heard of any such thing called 6mm223....

I built a 6mm-.223 (6X45) about a year ago, using a barrel from Randall at ar15barrels .com.  It's a great cartridge.  Easy to form and load, accurate, and a great bullet selection.  Mine has been extremely accurate and reliable.  The advantage over a 6.8 is the use of standard mags and bolt.  Disadvantages are lighter bullets, and it is a handload only proposition.  If you don't mind handloading all of your ammo,  go for it.  I wouldn't hesitate to build another.  

I know an older guy who used to neck up 223 to 6mm. He claimed accuracy was worth it. Ammo is easy to make and inexpensive. Not a fast or long range round though.

6X45 is an outstanding round in the AR!

It has been around for a long time and most people that own one would never part with it... bullets in the high 70s are out of the muzzle at around 2700fps and more efficient than the smaller bore rivals -- it is well respected in the bench rest gangs for its accuracy, easy to make, and works in the AR with only a barrel change.

I have said before, this is a round that really needs commercialized... imho

There was a thread about the pros and cons in the AR variants section last month.  I load the 6mmTCU which is close and it is a great little round.  Not as much power as the 6.5 or a 6.8, but uses the same bolt as the 223 and about the same recoil.

I have 2 friends that have 6 ppc AR's. One shoots 1 hole groups and one shoot 2" groups if he is lucky! Both have the same barrel, twist, and share the same loads. You couldn't do any worse than the 2" guy and might do as well as the one hole guy. Depends on what you are looking for. This is just my opinion, but anything but .223 is a table gun and can be a lot of fun, just depends on what you want it for. I have a DPMS super bull which I have had cut to 18", and fluted 3/8" to lighten the gun. I shoot .52 gr. match hp with ww748 in match cases and out shoot both of them on a 10 target shoot (100 and 200 yds).  I also have a 16" tac gun with red dot and open, that I shoot 55gr and 62gr factory, shot off hand,  that kills steel chickens at 100 yds. all day. Go for it and let us all know how it works.  Good luck and good shooting!!!
Al

I don't see the point, with .224" bullets available from 45 grains to 90 grains.

Thanks guys I was looking for a little bit bigger bullet out of the AR platform.  The heavy .224 loads start to push the envelope as far as chamber pressure, case life velocity etc, and they need a fast twist to work well.  If I'm going to change barrels (1-7-8 twist to shoot heavy bullets I might as well go with a 6mm223.  Also some states will let you hunt with a 6mm bullet and not with 22 cal bullets.   So that is a plus, I've loaded 60 grain 243 bullets for varmints before and I have a lot of 6mm projectiles on my loading bench so I don't mind loading for it.   I have a progressive dillon press and can crank them out, just not getting them mixed up with 223 is the trick.  Who's barrels are the best?  762

I agree with what Tcmers and Gunzilla have said about the 6x45mm or 6mm/223 as you call it. Another plus for necking  up to 6mm is that like bullet weights will be about 100 FPS faster in the larger bore of the 6mm, with the same pressure levels.

Tcmers had his barrel made by Randall at AR15 BARRELS.COM I had one made by White Oak in 20" SS rifle last spring around the same time. Liked that one so much had them make a 16" mid length in SS for me also. White Oak Precision

You will not need to do any extra steps for reloading this cartridge just one pass through the resizing die and the case is formed. I have had the best luck with once fired brass as new brass may come out of the sizing die a little shorter than 1.750". Powders like H322, H335, WC844, have worked well for me and have just started to use Benchmark.

This is a real fun cartridge and one which I think you will enjoy.

Joe

Quoted: I don't see the point, with .224" bullets available from 45 grains to 90 grains.

There is a secret to selecting a cartridge, and that is to not try and compare it to something else. Look at it like this, I have an AR15 lower what are the different chambers that will work with it. Now that a need has been established to try different cartridges we can feed our AR habit.

Joe

Thanks Joe I have a bunch of 1 fired GI brass and 8 lbs jug of Wcc 844 so I'll have to order a barrel for the  6mm223.  White oak I've herd of them.  I wonder who's barrel blanks they use.?  762

Quoted: Thanks Joe I have a bunch of 1 fired GI brass and 8 lbs jug of Wcc 844 so I'll have to order a barrel for the  6mm223.  White oak I've herd of them.  I wonder who's barrel blanks they use.?  762

I think they will use what ever barrel you specify. Think about a few things before you contact them like what length barrel and contour, stainless or chrome moly steel, twist rate of rifling(what bullets you will be using).  Remember they want you to be happy with your purchase so ask some questions and listen to what they suggest.

Joe

This sounds very interseting.

Quoted: I don't see the point, with .224" bullets available from 45 grains to 90 grains.

For many folks, there is no point really... but there are a group of us that are attracted to things simply because they are better -- the 6X45 does not need to prove it accuracy potential, as it achived darling status with benchrest shooters and in fills the need for many who live is states that do not allow hunting with a .224 caliber rifle.

Beyond that, the sort of techical side of things... if you compare bullets you will see a difference in SD and BC that tends to lean in favor of the 6mm, the OAL of the cartridge can be reduced for better use in magazine loaded rifles and the volume of the bore adds to efficency.

Sorry that you have not had a great experience with the round, my findings are that most folks that ever owned one, still own it...

Quoted: Quoted: I don't see the point, with .224" bullets available from 45 grains to 90 grains. For many folks, there is no point really... but there are a group of us that are attracted to things simply because they are better -- the 6X45 does not need to prove it accuracy potential, as it achived darling status with benchrest shooters and in fills the need for many who live is states that do not allow hunting with a .224 caliber rifle. Beyond that, the sort of techical side of things... if you compare bullets you will see a difference in SD and BC that tends to lean in favor of the 6mm, the OAL of the cartridge can be reduced for better use in magazine loaded rifles and the volume of the bore adds to efficency. Sorry that you have not had a great experience with the round, my findings are that most folks that ever owned one, still own it...

+1

My first try at a larger cartridge for the AR was the 6.8 SPC, after months of scrounging brass, Reloading dies, magazines and a upper I kind of lost interest in the whole thing. At this point I still wanted something a little more than 5.56mm so started to really look at the options and all things considered I believe my decision to go with the 6x45mm was the best one.

I live in a shotgun/muzzle loader/ handgun hunting area for deer here in Michigan, but can use a high power rifle for varmint hunting legally. Have hand loaded my own ammo since 1972, and already had bolt action rifles in the 6mm bore size. So for me this was a easy wildcat to try and all I can say is why in the hell did I not do this sooner.

I have known about this cartridge being chambered in the AR as far back as the mid 1980's. Like Gunzilla has said it needs to become a commercial round, then I am sure fewer people would be saying what is the point.

Joe

I had also thought of the 6.8 or 6.5 upper, but now I think I'm liking the sound of a 20" SS barrel in 6mm223 from white oak Precision with a free float tube and flat top heavy DPMS upper,  slap a harris bipod on it it should be a winner.   twist prob 1-9 is about right as far as shooting bullets up to 100 grains.   762

From a ballistics perspective, the 6mm is superior to the 6.8 or the 223 at all ranges, and has better down range energy residual than either of those two. The published load data has been much more thoroughly researched than any other 223 cased variant. Add to that the abundant choices in bullets, and it is a great choice for a handloader.

As a hunting round it is more versatile than the .223, and as good as the 6.8...which is pretty darn good. In my experience, it behaves more like a .243 than a .223...it is definitely a step up.

It fits the AR platform perfectly...better than the 6.8. All in all, I think the 6mm is about the optimum choice for the AR, (if the issue of never being able to buy a box of ammo doesn't bother you. Since I haven't shot any ammo in my guns that I haven't personally crafted for over 20 years, that is not an issue for me.)

However...having said all the above, considering the vast number of bullet choices in 223, including the Barnes TSX for hunting, and the growing availability of 6.8 uppers, I am not sure that I personally would go there at this point. I am more interested now in working with the 6.8 to see if the long range aspects can be improved somewhat...I think that round has a lot of untapped potential... but it's still perplexing to me why they didn't settle on the 6.5, and go with the best choice...

TC

Decisions...decisions...

If I wasn't such a fan of that other cartridge, the second most intriguing AR cartridge in the world, to me, is a 6x41 based on the .223 case, centered around 90-grain, high BC bullets, as explained to me by gun writer Stan Crist.

Now if one of you guys out there would develop such a cartridge, we could have endless wars about 6x41 vs. 5.56. Wouldn't that be fun!

John

Quoted: ..... but it's still perplexing to me why they didn't settle on the 6.5, and go with the best choice...

Because the 6.8 performed better in the tests that mattered to the military...  

http://www.qual-cart.com/6mm-223.htm

6mm-223 (6x45mm)

Use EDIT/COPY and EDIT/PASTE to place desired items on Order Form

Prices Shown are for Retail Customers, Dealers Please Call for your price OR use Dealer Price Sheet.

Bullet Wt. Price (Bx 50)  
Empty Brass* 59.97
Sierra  
55gr SPT 69.97
60gr HP 69.97
70gr HPBT 69.97
70gr SPT 69.97
75gr HP 69.97
80gr SBT 69.97
85gr SPT 69.97
85gr HPBT 69.97
90gr FMJ-BT 69.97
100gr SPT 69.97
100gr SBT 69.97
107gr HPBT 69.97
Nosler  
55gr Ballistic Tip 72.97
70gr Ballistic Tip 72.97
80gr Ballistic Tip 72.97
85gr Partition 77.97
90gr Ballistic Tip 72.97
95gr Ballistic Tip 72.97
95gr Partition 77.97
100gr Partition 77.97
Hornady  
70gr SP 69.97
75gr HP 69.97
80gr FMJ 69.97
87gr SPT 69.97
87gr BTHP 69.97
100gr SPT 69.97
100gr BTSP 69.97
100gr RN 69.97
100gr SST 69.97
Barnes  
75gr S (Solid) 89.97
85gr S (Solid) 89.97
85gr XBT 89.97
85gr XLC 89.97
90gr X 89.97
95gr XLC 89.97
95gr TSX 89.97
Speer  
70gr HP-TNT 69.97
70gr HP Moly 69.97
75gr HP 69.97
80gr SPTZ 69.97
85gr SPTZ-BT 69.97
90gr SPTZ 69.97
100gr SPTZ-BT 69.97
105gr SPTZ 69.97
Swift  
90gr Scirocco 119.97

*Correct headstamp available in this caliber with a 300pcs min order


Looks like this place had loaded ammo at some point. It is marked 2003 but it may be worth a call to see if they are still in business.

Gordon

Let me see if this works:

Yes it does work, click the link and it will show you the Ballistic Comparison.

.223 VS 6mm-223

ammoguide.com/?tool=bcompare&it=132%7c237

Here is a 6.8 VS 6mm-223 load

ammoguide.com/?tool=bcompare&it=263%7c237

I have no problem making my own ammo.  I've loaded 1000's of rounds. I can crank them out on my dillon 650 as fast as I can pull the handle.  As far as wildcats, I'v made 30 Harrett for a TC for years.  In the 6mm223 case it is really not anything at all to do,  just run the 223 case through the 6mm sizing die. Done.  Load.   The reason I want a 6mm223 are basically a few different reasons, one is I already have a 243 bolt gun, So I have lots of 6mm bullets, 223 brass is cheap and easy to come by 6.8 ain't  it will use the 846 surplus powder I have as well.  I have lots of AR rifles, lowers etc.  It would be a target rifle only, If the SHTF.  I'm going to a 30 caliber rifle anyway (a belt fed if possible)  But the AR platform is a very accurate and fun gun to shoot. I think a 6mm223 would add to that fun.  I think I could use a high BC 90 -100 grain VLD or MatchKing bullet and have less wind drift then the 6.8, also I can use existing magazines bolts and carriers, this sound like a win, I don't have to wait for new 6.8 bullets to come out it's all ready to go.   I'm glad  others people have had positive results with this combo. I'm sold getting a 6mm223.    762

Gatman762:
I think you have made a good decision going with the 6mm/223. In some ways I am sorry for those who do not reload their own ammo, as they may never get to try this cartridge to see for themselves its advantages. Then again I kind of like the idea that it is a wildcat cartridge and I am one of the lucky ones to be able to shoot it.

Let use know when you get your AR set up and get a chance to test out some loads for the 6mm/223.

Joe

Gatman...I don't really care for ball powders in this round, as it is not consistent with my purpose in working with the round. I was looking to improve downrange performance out to 1000y, of which accuracy is an important factor. For a cheap blaster, 223 is hard to beat.

But I was pleasantly surprised to find that this round really seems to thrive on 4895 with heavier bullets, which I stock almost entirely as surplus....and it is not real touchy about the loads either.

Overall, it seems to be more forgiving than the 223 as far as powders go, and is about as simple a wildcat as one can imagine. I found that by using commercial brass, I could get a couple more grains of powder in, and that seemed to help out a bit.

TC

TopCat and others with 6x45 experience: Does the complete list of 6mm bullets by Grevels on Page 1 fit in a 45mm case while yet limited to an AR magazine length of 2.255"?

As it was explained to me, some of the higher BC bullets — which I would prefer — would require the case shortened to 41mm to properly seat them to an AR mag-friendly OAL.

I do know that the 6mm 90-grain Lapua Scenar has an ogive length of 16mm. If 2.255" converts to 57.3mm, then that bullet, for example, is going to need a case length not more than 41.3mm.

What do you guys say about the issue?

John

Quoted: TopCat and others with 6x45 experience: Does the complete list of 6mm bullets by Grevels on Page 1 fit in a 45mm case while yet limited to an AR magazine length of 2.255"? As it was explained to me, some of the higher BC bullets — which I would prefer — would require the case shortened to 41mm to properly seat them to an AR mag-friendly OAL. I do know that the 6mm 90-grain Lapua Scenar has an ogive length of 16mm. If 2.255" converts to 57.3mm, then that bullet, for example, is going to need a case length not more than 41.3mm. What do you guys say about the issue? John

I have not used the 90-grain Lapua Scenar myself, but you are correct that there are some bullets because of there length from ogive to tip will not work well with magazine OAL restrictions. Bullets that have worked well for me so far are from Hornady and Sierra in weights from 70 to 87 grain.

The 87 grain Hornady V-Max is a example of a high BC bullet that would end up being to long to feed from magazines. Nosler Balistic Tips are some others that do not work well.

Maybe a 6mm/222 wildcat with a shorter case neck would be better for bullets like the 90-grain Lapua Scenar .

Joe

John...your info is correct. One limiting factor with this round is the length of ogive that can be exposed and still fit into the mag. (The 5.56 and now the 6.8 both run into the same limitations.) I think the 6mm has a slight advantage...and as your handle seems to imply, you have figured out the essential advantage of the Grendel.

The Scenar bullets are pretty loooong...when I was working with the round, the Lapuas were not as common, so I didn't really play around with them. Also, they seemed to need a slower twist, so trying to use heavy Lapuas may not be the best option here. They were not really designed for this mid-range application anyway. They are an exceptional product, but kind of a specialty VLD item.

The goal here for longer range is to find the heaviest bullet that will properly fit the case neck, and not be too long for the magazine. Different manufacturers produce bullets with different bearing lengths, ogive length, oal...etc, etc., you just have to do a little testing to find the right fit in the 90-100 grain range. Lighter bullets are universal.

You are correct that the optimal 6x45 cartridge length for the heaviest bullets would be a hair shorter, but, in my opinion, it works good enough as is, even up to the 90-100 grain area with the right bullet. Realize that there are one hell of a lot of different .243 bullets to choose from, and they are all different. Not all of them will necessarily work out, but having a great selection to choose from is one of the advantages to the handloader.

Though I have always liked this round, the 6x45, I am not necessarily recommending that anyone pick up the gauntlet at this point. As I mentioned in my earlier post, the marketplace has now provided some interesting and more standardized alternative choices, and the 223 has improved as well.

More important is that a lot of very qualified folks have spent a lot of time and money, (their own), researching and refining the alternatives. The 6.8 and the 6.5 are just starting to be viable commercial propositions, and they have a lot of support in the community. Bigger is not necessarily always better, but it usually doesn't hurt. I am not one of that camp who is dissatisfied with the performance of my 223 loads at this point. With the right bullet and load, it seems to get the job done.

Yes, the 6x45 is a very versatile round, and would have been a good solution to address any terminal effects issues some folks have concerns about. If there had been sufficient interest to work out the minor details, it represents a very convenient way to "improve" the 223...like 25 years ago. But we weren't fighting a war then, so the motivation just wasn't there.

TC

I talked to white oak precision today about getting me a barrel for the 6mm223.  He is 12-16 weeks on custom barrels.  Wow business must be good.  I'm going with a 1-7.5" twist 20" stainless steel pac-nor with an evolution stainless gas block.  I'm looking forward to building it up.  Now I need to order some redding dies in 6X45.  I'll have the throat set up to shoot burger VLD 95 and 105 gr. bullets  I'm going to use optics but I'd like to also be able to use a clamp on front and rear iron sights as well.  The carrier will be a 416 stainless JP ent.  not sure about the front tube or upper yet I like the idea of the heavy duty DPMS upper but not sure if I can do with out an ejection port cover?   project begins.   762

Quoted: I talked to white oak precision today about getting me a barrel for the 6mm223.  He is 12-16 weeks on custom barrels.  Wow business must be good.  I'm going with a 1-7.5" twist 20" stainless steel pac-nor with an evolution stainless gas block.  I'm looking forward to building it up.  Now I need to order some redding dies in 6X45.  I'll have the throat set up to shoot burger VLD 95 and 105 gr. bullets  I'm going to use optics but I'd like to also be able to use a clamp on front and rear iron sights as well.  The carrier will be a 416 stainless JP ent.  not sure about the front tube or upper yet I like the idea of the heavy duty DPMS upper but not sure if I can do with out an ejection port cover?   project begins.   762

I have a Mini 14 chambered in the 6x45 and it is sweet but the one problem I've had with trying to load heavier bullets is that keeping the OAL correct for the magazine pushes the heavier bullets too far into the case.  You have a small capasity case and you are reducing the capasity even more by filling it with bullet rather than powder.  When all is said and done, I've found the optimum bullet weight for me was 75 grains, I've loaded some 80's and 85's but my velosity starts dropping in that range.

IMHO, a 105 gr is not going to be an option.  If you find something that will work please post here, I would be happy to be proven wrong.

When I get the upper built I'll experiment with different bullets.  I was told there are guys using the 115 gr bullets, but that may be in the 6mm WOA which is a 6.8 case necked down to 6mm. Interesting.  I'll have to see, the 105's might not be magazine compatible, they may be like the 80 gr 223 round  ie. single load only.  I'm looking forward to working it out, not proving anyone wrong.   I'll post it here.   I shot some very nice groups the other day with my 1-9 twist bushmaster using 75 grain bullets 10 shot one inch groups 100 yards off the bench using a bipod and that twist ain't suppose to shoot heavy bullets well... ya never know.  the load was 24 grains of 4064 75 gr Hornady BTHP molly in a LC case and win primer.  I'm looking for ward to trying a similar load in the 6mm223.  762

I found the 80's and 85's fit into the mags just fine, no single feed required, actually that was never an option.  If the finished cartridge would not feed from the mag, I made no attempt to develop the load.

That's all I needed was a single shot semi automatic

Great thread, as I have a 6x45 coming from Marty at Teppo Jutsu.  My goal is to have the 85 grain Barnes TSX work.  Fingers certainly crossed.  And, as pointed out, the 6mm is the lower limit for hunting in many states.  I am actually going with a 24" tube.

One additional thought for those who are concerned about magazine length and a few milimeters is to try the old cut magazine trick.  I have one magazine that I cut out for longer 5.56 rounds, and the magazine still functions perfectly with standard rounds and 458's.  I found the magazine trick in "black Magic".

Craig

Well I went ahead and ordered the barrel today from White Oak precision.   I'll be using a 1-7.5 Pac-Nor barrel blank but I changed it to 22 inch length instead of 20" its going to be a heavy one inch under the hand guards and .933 in front of the sight block.  I'm going with a evolution arms gas block to be as low profile as possible.  I'm not sure about the hand guards yet.  I think I've decided to go with DPMS upper receiver with the thicker heavy wall thickness  with out the port cover or forward assist.  not sure about weather I'll use the high-rize or regular flat top receiver.   I'm hoping to get the 95 gr in a magazine length load.  I'll use w-w cases as they seem to have the most internal volume for 223 cases, so I can pack the powder in it.  Using molly bullets will help also as they seem to have less pressure spikes using them.    762

I believe Dtech got some Olympic SUM barrels in 6x45mm a while back in 1 in 10" twist, these should be good to stablize bullets around 90 grains in weight. here is a link.

Dtech

I think it is pretty unlikely that the 105 gr bullets will be doable with a mag length load. Since you are going to have a wildcat on your hands anyway...and it will take a while for the barrel to arrive...why not consider the larger 6.8 case? That round would really  rock!

TC

Quoted: I think it is pretty unlikely that the 105 gr bullets will be doable with a mag length load. Since you are going to have a wildcat on your hands anyway...and it will take a while for the barrel to arrive...why not consider the larger 6.8 case? That round would really  rock! TC

I have to agree with TopCat, with bullets above 90 grains the larger case of the 6.8 would be better and with the same case length of 43mm would allow for bullets that you could not seat out far enough in the 6x45mm.

I have not seen much in the way of data for this 6mm SPC wildcat so if it was me I would need to know more about the cartridge. John at White Oak would be the one to ask.

Joe

I used to have a 6x45 and it was not bad but I was always worried about mixing the ammo for it in with my normal .223 ammo.  Anyway once I found the 77gr SMK and worked up a great load for it I sold the 6x45 on to the next experimenter to play with.

The reason I didn't go with the 6mm woa ie 6.8 necked down to 6mm,  although the concept is very cool,  is it requires new magazines, which is added $$ to the project and also it requires a different bolt or the bolt face to be opened up to larger dia.  which again is more $$.  Then on top of that the 6.8 brass is expensive to buy (right now) and is not guaranteed to be a marketing success if the military doesn't adopt it.  I like to shoot a lot so I have thousands of brass cases for 223 which are easy to turn into 6mm223 6X45 cases.   I also own a 243 rifle pre 64 Win mod 70, so I have lots of bullets for the 6mm already on hand.  I'll need dies but that is the case either way, 6X45 dies are available right now from redding for $54  6mmWOA would have to be custom made for $100-200 a set.  Loading data for 6mm223 is also in the loading manuals ready to go.   I can use the existing bolt and magazines.  Theses reason just keep stacking up in the 6X45 favor.  I've always been a fan of the Ar accurate rifle but not really a big fan of 223.  years ago I bought a Oly 762X39 upper but it didn't work out (shot very bad ) and magazines were an issue, so I sent it back stuck to 223.  Now I'm back on the bigger bullet AR-platform again.   The issue of mixing 6mm45 and 223 is something to watch out for...762

Quoted: I used to have a 6x45 and it was not bad but I was always worried about mixing the ammo for it in with my normal .223 ammo.  Anyway once I found the 77gr SMK and worked up a great load for it I sold the 6x45 on to the next experimenter to play with.

I just do not see this as a issue to be concerned about, the bolt will not close on a 6x45mm cartridge in a .223 chamber. The other way with a .223 cartridge in a 6x45 chamber the bullet is to small to cause any pressure problems.

I can understand if you personally are uneasy about this but if everyone thought this way no one should have any combination of rifles chambered .243 win, .260 rem., 7mm-08 and .308 win.

Joe

That is true JAR but it just makes people worry about things when murphy is hanging around.  I've seen thins happen in guns that is a one in a million chance, no way it could happen and it does.  Like a 32 special loaded in a 30-30.  Like the 380 that fires in a 9mm pistol. I had a M1 garand that on feeding pushed the bullet back into the case and fired that puppy off the brass flowed back into the bolt face like molten lead, then gun was locked up, we had to beat it apart with a rubber mallet.  No damage was done to the gun but it sure was a proof load.  
I've decided to Go with JP ent stainless steel gas block and open it up from .933 to one inch and have my barrel a full one inch dia. it will be a heavy beast.  762

John

A 6x41 should launch the 90 grain Scenar around 2500-2600fps from an 20" barrel.   I'd trim cases to 1.615.  You'd have .245" of neck left.

What would you do with it?

David

If a 6 x 41.3 is exactly suited for a 90-grain Lapua Scenar at AR15 magazine length, I suppose I'd hedge a bit toward the majority of bullets that have less-extreme ogives. Thus, I'd end up with a 6 x 42 that could shoot most any 6mm bullet while maximizing case volume. Oh, yes, it would have a 30° shoulder. (Any enterprising souls getting the hint? )

John

Is this the same as the 6mm TCU cartridge of T/C Contender fame?
I have a 6.5mm TCU pistol (10") and carbine (21") barrels for the Contender and love them.
If I remember right the series run 6mm TCU, 25 TCU, 6.5mm TCU and 7mm TCU.
Easy to form brass and dies are available.

Quoted: If a 6 x 41.3 is exactly suited for a 90-grain Lapua Scenar at AR15 magazine length, I suppose I'd hedge a bit toward the majority of bullets that have less-extreme ogives. Thus, I'd end up with a 6 x 42 that could shoot most any 6mm bullet while maximizing case volume. Oh, yes, it would have a 30° shoulder. (Any enterprising souls getting the hint? ) John

Just a Simple thing like mags with a little more room for overall length in cartridges like the 223 and 6x45mm would make a world of difference. Many of the bullets that seat to deep for the 6mm would then work ok. Hint PRI already does this for their mag in the 6.8SPC cartridge, and this would allow around .030" to the overall cartridge length of 2.260".

Joe