6mm TCU

[Jason]

I think you hit the best combo yet according to the numbers, especially with the crazy low recoil and still hitting 1.2 for momentum on rams. Let's hear more about the 6.5-04 and the 140 A-Max bullets, though...

[DanDeMan]

I think you hit the best combo yet according to the numbers, especially with the crazy low recoil and still hitting 1.2 for momentum on rams. Let's hear more about the 6.5-04 and the 140 A-Max bullets, though...

Jason,

I"m thinking that the 6.5-04 should be able to launch the 140 A-Max bullets to 2,620 fps with 30.5 grains of N150. Maybe RL-17 could push the bullet to close or maybe over 2,700 fps.

[DanDeMan]

redundant...

[DanDeMan]

Ladies and Gents,

I posted this on Jason's "Momentum required for for pigs?" thread, but thought it should also be on this one.

The projected 7-04 CPT load will have 4.3 ft-lbs of recoil when launching the 139 SST to 2,000 fps with 20-gr of H4198. Pigmentum should be about 0.94 lb-s. The strongly constructed SST's should kick-azz on pigs, no ringers for sure. Hey, what's not to like.

[DanDeMan]

OK...Dang,

Here's some more to chew on with respect to the 6.5-04. First, I already have an optimized reamer for the HP silhouette game, my current 6.5 TCU chamber reamer. All that needs to be done is run the reamer in a bit more, oh silly me. And, I've got an 8-twist Krieger barrel in an appropriate contour ready and willing to go there. Just might have to make the 7-04 a switch-barrel.

For the 6.5-04's CTP load, a 123 A-Max at 2,300 fps launched with 22.0-gr of H4198, the perfect powder for CPT with the 123 A-Max, sounds mighty tasty. Having a little used 8-lb keg in the powder magazine also helps. Pigmentum is 0.982 while recoil is 4.7 ft-lbs.

[DanDeMan]

Shooters,

Here's a link about my first 6.5mm TCU rifle used for HP silhouette, including a match report, if any of you are interested in more info. The 6.5-04 will be able to launch the 140 VLD's to at least another 100 fps over the 6.5 TCU.

http://www.go2gbo.com/forums/index.php?topic=25310.0

[Bob Mc Alice]

That was some good reading, Dan. I had no idea you were/are that into cartridge design and experimenting. Those postings are from 2004, prior to 2006 I had never even touched a computer. Wished I had. Keep us informed on progress with the 7-04 rifle. I am looking forward to reading a full blown, in depth shots fired report. I would expect no less from you.

[DanDeMan]

Bob,

I've been heavily into cartridge and bullet design, HP, SB and BPCR, for a long time, as well as rifling design for BPCR rifles. My first reamer design was back in 82, a JGS reamer for my original 7 TCU-on-steroids, based on the 5.6 x 52 RWS case for pistol silhouette, designed around the 162-gr Nosler bullet. That round coupled with the tough as nails 162 Nosler Bevel-base bullet drove the 308 and 708 guys crazy. I never rang a ram while those guys did at times. Bullet construction is the name of the game when slamming steel, as you well know. As a matter of fact, I was called for damaging rams, a lighter bullet was used for CPT's, by the match director one day. When I showed him what looked like a 7 TCU he stammered after yelling at me, paused and walked away shaking his head. Ahhhh, life was sweet that day. Since getting into BPCR silhouette, mid-range, long-range and gong matches, I've gotten further into my addiction. At BP Target Rifle Nationals, a substantial portion of the top competitors shoot my bullet designs and have barrels chambered with my chamber reamers. I've also taken to publishing articles in gun mags; BPCR stuff. Most of the custom bullet-mould makers for BPCR bullets make my designs. Here's a link to the BPCR "candy store" that makes my designs. There are probably 50 or 60 of my designs made by Buffalo Arms. The winner of the 2011 championships was my shootng pard, Doc Lay. He was shooting a bullet of my design made by the mould master, Paul Jones. The link notes that the 2010 and 2012 winners were also shooting my designs.

http://www.buffaloarms.com/Detail.aspx? ... 1&CAT=4157

[Jim T.]

Dan:

Could you educate me on the benefits of the 6.5-04 or 7-04 over a 6.5BR or 7BR or even a 6.5 Grendel or 7Grendel? Does it all boil down to case head size? What about short and squat vs long and skinny?

Jim

[kevinbear]

If your going to feed the cartridges from the magazine the 223/204 cases work much better and take less effort{concieveably you could cycle the bolt with the gun on your shoulder} than the short fat rounds. I work the bolt on my 223 quite often mounted when coyote hunting although I don't at silhouette normally but it would be nice to have that option.

[Trent]

I can't tell the difference between my .204 and my 7-08. Kevin, can you really tell?

[edgehit]

I love innovation and I admire Dan's ideas and use of the -04 case. I'm going to rain on the TCU parade a bit and share my 7 TCU experience.

I got caught up in a fascination (infactuation?) with the 7 TCU rifle 2 years ago after shooting a few rams with a borrowed gun after a match. I ended up building one with a 7 twist kreiger bbl on an XP-100 action. I tried 4 or 5 different powders to establish desired ramentum and finally settled on leverevolution. I needed about 2 more grains of case capacity. Dans onto that with his -04. But my 500m accuracy just wasn't there and I lost confidence in my choice. In the end, I rechambered to IHMSA because the TCU's case capacity was just too finicky to deliver 500 m accuracy. Maybe someone with more patience could have succeeded.

My IHMSA ram load delivers a 162 A-Max at 2300 fps and knocks down rams just fine with 0.3 min accuracy with H4350. But I've shot my 260 with 140's at 2720 fps and they have less felt recoil to me. The 107's definitely have less recoil than the 7 IHMSA 120 gr CPT load with better BC to boot.

Right now, my soft recoiling choice would be a 6x47 or 6XC with fast twist to shoot 115 gr bullets at 2600 fps for all critters. Its rumored this is the stuff national champions are shooting. A 243 may be slightly less expensive with lower brass prices. And you wouldn't wince if a case hit the ground or you lost one.

I've exceeded my limit! Carry on!

[kevinbear]

Edgehit, do you think there is enough difference between the 6x223 and the 6x222mag to justify not useing the 223 case? I have thousands of commercial 223 brass casings, {won't all fit in a 5 gallon bucket}.

[DanDeMan]

Dan:

Could you educate me on the benefits of the 6.5-04 or 7-04 over a 6.5BR or 7BR or even a 6.5 Grendel or 7Grendel? Does it all boil down to case head size? What about short and squat vs long and skinny?

Jim

Jim

Case volume is the key. I know plenty of shooters have argued about case proportions, long-skinny vs short-squat, but to be honest I have not yet seen any difference whether the cartridges are HP or BPCR. The smaller the internal case volume for a given bullet and MV, the more efficient the round. That means one can use less powder, have less recoil and have longer barrel life.

For instance, I've got a 7-twist, 223 set up for Palma, reamer designed to seat the 90-gr Bergers optimally. It launches a 90-gr Berger VLD to 3,040 fps with only 28.5-gr of RL-17. That works out to 107 fps per grain of powder. Now, compare that to a 22-250 loaded with the same bullet to the same MV with 36.0 grains of H4350. That load would produce 84 fps per grain of powder and it would washout a barrel quicker and have more recoil; 800 to 1,000 rounds and that barrel would be toast. My original 223 Palma/FTR rig has over 1,500 rounds through it and there is only moderate scaling on the land tops when looked at with a 25X Hawkeye bore scope.

Here's another example of small case capacity benefits. For years I shot the very mild recoiling 6.5 TKS, improved 6.5 BR, in silhouette competition. One of my barrels went over 6,000 rounds and was still shooting 1/4 MOA groups.

[boats]

Dan

Did a search but could not find any of your post on BPCS cartridges, 38/72 in particular. Give me a good link to read about it.

Boats