I'm considering 6.5 MPC or the 6.5 TCU, I currently have a 6.5 Grendel with an 18" barrel. I would like to get close to the same ballistics of the Grendel, but be able to use the cheaper 5.56 brass. Is it realistic to use bullets weights in the range of 107 to 123 gr? I would really like to stick with Hornady's new 123 A-Max, I don't know if this possible considering the 123 a-max is 1.230 in length. Loading a 123 a-max using Grendel dies and 5.56 brass I was only able to 21 grs of H335 before I started to compact the load.
After talking with SSK industries they told me you have to cut, size, and fire form brass for the 6.5 MPC. On the plus side they have 6.5 MPC brass in stock and ready to load for .40 cent a piece. SSK also sent me load information with velocity's from different length of barrels. Looking at the 6.5 MPC velocity, it doesn't seem that much different than the 6.5 TCU.
Do you have to fire form  brass for the 6.5 TCU or can you just run it through a sizing die? I really don't want to have to mess with fire-forming brass. Could the 6.5 TCU get close to 2550 fps with an 18" barrel using the 123 AMAX?

Here some of the velocity's for the 6.5 MPC form SSK

108 Lapua168022.02500  16” AR
107 Sierra168022.42525  16” AR
107 Sierra168022.42650  20” AR
95 V MaxN20022.92697 20” AR
95 V MaxN20022.92515 12” AR
120gr. Match KingN 13019.61946  12" AR
120gr. Match KingN 13020.62033   12" AR

Yes, you have to use a sizing die and fireform on the 6.5 TCU.

6.5 TCU 2,550 w/ a 123gr V-MAX out of an 18" barrel AND AR-15 Magazine Length?

See this and the COAL: 6.5mm T/CU

I use 100gr to 108gr Bullets in my Grendels.

H-335 is the wrong gunpowder to use for a 123gr V-MAX 6.5 Grendel.  You should be using a slower powder.

For the 120gr to 125gr bullets, I used AA-2520 and H-4895 in my Grendels.

I've been using use H Varget for the Hornady's 123's in my Grendel because a got a great deal. I had a pound of H335 setting out so that's what I grabbed to see how much powder I could fit in the case before I started compacting the load. I was talking about loading the 123's at mag length 2.260.

Here are those velocitys again, hopefully they smash together

108 Lapua             1680            22.0                     2500 16” AR
107 Sierra              1680           22.4                      2525 16” AR
107 Sierra             1680             22.4                       2650 20” AR
95 V Max               N200           22.9                      2697 20” AR
95 V Max               N200             22.9                      2515 12” AR
120gr. Match King                   N 130          19.6         1946 12" AR
120gr. Match King                   N 130           20.6           2033 12" AR

No need to bold the text, I read it years ago.

Did you look at the COAL for the 6.5 TC/U?  The answer is there for you.

Out of an AR, I would not use the 123gr V-MAX bullets in the .223 case, TC/U or MPC.  IMO, it is too heavy and too long.

Out of my 18" Grendel, the 100gr Scenar Match bullet will remain supersonic to 800M, in most all conditions, though I have not shot it past 320M or so (it is a long drive to the Western part of the state to get to the longer distance ranges). 30.0gr of AA-2460 w/ Remington 7 1/2 Primers.

The issue with the TCU is loaded OAL with the heavyer bullets. Keeping it to 2.25 the longer bullets start to get into trouble. The MPC looks the same. I did not like the fact that 1/2 or more of the bullet was in the case. To give me some flexibility with bullets I shortened the 6.5TCU to 1.55. This seats the base of the 100g nosler BT at the neck/shoulder junction & gives me 2.25OAL. This was my prefered bullet for hunting here. My 16" brl gives me 2500fps with said bullet. 120/123s will run 2200fps. These will net another 100fps with the 20" tube & lose 150fps with my 12" setup.

Hello Fellas, Red is correct...you must use the faster burning powders for both the 6.5 MPC and the 6.5 AR-TCU. The SSK MPC round according to JD maxes out to a COL of only 2.240", which is
why I get annoyed with the 6.5 MPC vs. 6.5 AR-TCU.

When I ordered the MPC Upper with dies and brass and started to load/test the MPC round I was not able to chamber a round...when I talked
to JD he told me the Max COL was 2.240" for the MPC !

I also later found out that resizing die must be backed-out 3 full turns,Instead of the usual 1 or 2 turns,otherwise you will get shoulder set-back/buldging of the case. Then to add Insult to Injury I wound up getting a stuck case in the the sizing die even with plenty of case lube, apparently using virgin 5.56 brass with a combo of a tight new chamber and new dies= stuck case Just bad luck I suppose, so back to SSK for a
new die and a cartridge checker ($30 plus shipping). You would thiink SSK would give you more load data and cartridge/chamber print (which I requested btw) and maybe some chamber pressure charts...but no.

So back to the 6.5 AR-TCU...yes to do have to fireform the cases,but so what? You can load a new round at normal to near max, fire it and then save the fireformed cases. I have had no Issues with both 223 and 5.56mm brass with the TCU round. I can load the 6.5 AR-TCU to Max Mag length(2.260" to 2.300" depending on the Magazine you use). You do get 2 to 3 grains of extra powder capacity with the fireformed AR-TCU
case.

As to the bullets with regard to bullet length...yes, overall you will find the the super high BC's of the 123 grainers are about Max. for good performance with both MPC and TCU rounds, however, the TCU does have the edge with the longer/heavier bullets.

I have not tested for velocity yet,but you should get around 2,300fps-2,400fps with the MPC w/ 18-20" bbl.
The AR-TCU should get around 2,420-2,600 fps w/ 20-24" bbl. with the 123 grainers.

Oh, btw both rounds have to be trimmed (cases) to about 1.629" (41-42mm) and sized to proper dimentions.

I will be doing some more testing with both rounds hopfully soon...stay tuned.