7mm TCU
- Thread starter 300_whisper
- Start date
Yes, And it's a lot more effective than other cartridges with Ackley improved shoulders. The bore ratio to body is higher. While the Ackley shoulder limits flow of pressure out of the case (what makes the bullet go faster) the narrow shoulder in comparison to the bore allows pressure to flow out of the case upon firing.
Yes, and yes, and no.
The original intent of the Ackley improved, like any improved, was to simply increase capacity. It was found after some time, that increasing the shoulder angle increased the compression as the powder stack ignited. The top pressure curves in a full or even medium case ( .308) become very unpredictable at the top edge. Other "improved case" competitors scaled back the angle to alleviate that phenomenon. Most notably Fred Huntingdon, who created the RCBS series of improved cases that were typically 28 degrees.
The big benefit, that I have not seen drawback from, was the straightening of the case walls. That helps hold the case in the chamber better and reduce bolt thrust. The .308 sort of uses this in that it's case walls are straighter than the .300 Sav. (it's parent case) and the .30-06. At least the principle was, it will hold more pressure than it's predecessors. Due to NATO requirements though, that it be usable across the board with many countries, the pressure in 7.62x51 is kept down. Specifically, early Spanish small ring Mausers.
Added: That's one of the best attributes of the 7mm TCU. You can run a LOT of pressure in it. The overall size means "Total" pressure is lower than a midsize case and the straight walls hold it well. In the TCU you don't have the gas system headache to make it work.
I should have added, and I am really remiss in not saying this in the first place, is that slightly below the top pressures, Ackley cases become VERY efficient. So, if too much pressure isn't getting in the way of pressure flow out of the case, They are exceptional improvements. But, it seems like the ability to test what's really going on came 50 years after the first examples came out.
I know a number of people who've had great success and told me just work up to where it seems to give an advantage over the parent cartridge then stop. Being young and knowing everything, I worked up to max and got great velocities, then blown primers, back down and blown primers(hot barrel)...headaches and can't figure out WHAT? And, doing this while the gunpowder side of the industry is switching to the "new" powders. Not understanding those powders yet is really what threw me for a loop.
So, I would advocate working up Ackley improved cases to where you see a good improvement and stop there. It is a more efficient case, just too efficient when you get to the top pressure line.
I know a number of people who've had great success and told me just work up to where it seems to give an advantage over the parent cartridge then stop. Being young and knowing everything, I worked up to max and got great velocities, then blown primers, back down and blown primers(hot barrel)...headaches and can't figure out WHAT? And, doing this while the gunpowder side of the industry is switching to the "new" powders. Not understanding those powders yet is really what threw me for a loop.
So, I would advocate working up Ackley improved cases to where you see a good improvement and stop there. It is a more efficient case, just too efficient when you get to the top pressure line.
I need a "BTDT -Pulled some hair out" t-shirt
I have always wondered why nobody chambered one of the tcu rounds in a lightweight rifle...I have a super 7tcu but a light rifle would be nice...
Check out Reeder's line of Raptor cartridges
They use the 204 Ruger brass, basically 222 Rem Mag,
I've got a little carbine barrel in 30 Raptor and love it!
They use the 204 Ruger brass, basically 222 Rem Mag,
I've got a little carbine barrel in 30 Raptor and love it!
When I built my 7mm-08AI, I checked them out for load data.
What some people were posting for that cartridge was definitely hot! Neigh on dangerous!
Even starting 3gr below their "data" was giving me pressure signs.
Like gotta use a hammer to get the bolt open.
Needless to say I don't/won't use them!
Nor will I recommend them!
I don't give 'em merit either.
Coincidentally, I'm presently embroiled in a project that utilizes the 7-08 Ackley design on a 307 Win case resulting in a semi-rimmed 7-08AI in the contender! It's called the 7mm JDJ#2 or 7mm Super Bower or 7x307AI
a little fancy woodwork of mine on the back end.... W0W!
SSK Industries offers reliable and safe load recommendations for their barrels.
They made this one from a TC 7-30 Waters.
Coincidentally, I'm presently embroiled in a project that utilizes the 7-08 Ackley design on a 307 Win case resulting in a semi-rimmed 7-08AI in the contender! It's called the 7mm JDJ#2 or 7mm Super Bower or 7x307AI
a little fancy woodwork of mine on the back end.... W0W!
SSK Industries offers reliable and safe load recommendations for their barrels.
They made this one from a TC 7-30 Waters.
Last edited:
Back to the 7TCU, Junior Doughtry was an interesting guy:
Here's his post on propellant conservation
He was also a bit of a radical experimenter
I'm still a 7-30 Waters fan, tho.
Here's his post on propellant conservation
He was also a bit of a radical experimenter
I'm still a 7-30 Waters fan, tho.
Last edited:
Wes and his kids...mostly Wes...built a rifle for each of his kids. I've shot them and have always wanted to do a rifle for myself. So the reality is hyper-velociy is out. The only one that kind of fits that bill is the 6mm TCU moving light projectiles up to 90 gr.. Well, .25 TCU too. Again light projectiles, 75's-90's.
However, understanding how much energy heavier projectiles give, launching a 140 out of a 7mm TCU at up to 2200 fps gives viable medium game killing ability with next to no recoil at short-medium distances. Good killing ability farther out, but one must know their ballistics with it. To me, going with the lighter 100-120 grain bullets is the way to go. Good killing ability and flatter trajectory. And, don't forget the 6.5 TCU. A great range of bullets that can handle varmints to medium game.
That said, their are a whole range of cartridges that handle what these cartridges can do that are already chambered in rifles. So the turnoff, or rather non-turn on, is that it's too much work to go the TCU route. In limited applications, I think it's worth it.
JEFFPPC
Gold $$ Contributor
I shoot IMSHA with a pair. 139 Hornady Spire Points over 3031. If a range had clay the targets fell into I would shoot the same bullet in 154.
Well I had a few 7 TCU guns before I retired from competition, XPs and TCs
My setup is wih a 145 grain Speer at .003 off the lands then seat the other bullets using that seater die setting, do not change it.
Cast: Alloy is 70ww, 20 Lino, 10 Mag shot water dropped, sized to the groove
145 RCBS Silhouette with 15gr 4227, LBT Blue lube with spherical shot shell buffer 1/2 way up the neck, to compress shot 1/2" in my Sinclair XP-100 load is right out of the Handloadng Annual. Shot through C-R shoot offs 5x5
168 RCBS Silhouette LBT Blue with 6.5 grains of Unique Sperical buffer over powder compressed shot through C-R
All Hornady GCs
Jacketed
130 grain Speer Flat Base Spire Spire Point with 29 gr WW 748 C-T and shoot offs 5x5 chickens at 200 meters
160 grain Speer with 28 gr WW 748 R
Shot the jacketed bullets primarily in the 10" and 14" TC. The 7 TCU, 7 BR and 357 Super Mag all have the same H2o case capacity. Use commercial brass, not military, selected by capacity for match brass
My standing unlimited gun in 7 TCU
My setup is wih a 145 grain Speer at .003 off the lands then seat the other bullets using that seater die setting, do not change it.
Cast: Alloy is 70ww, 20 Lino, 10 Mag shot water dropped, sized to the groove
145 RCBS Silhouette with 15gr 4227, LBT Blue lube with spherical shot shell buffer 1/2 way up the neck, to compress shot 1/2" in my Sinclair XP-100 load is right out of the Handloadng Annual. Shot through C-R shoot offs 5x5
168 RCBS Silhouette LBT Blue with 6.5 grains of Unique Sperical buffer over powder compressed shot through C-R
All Hornady GCs
Jacketed
130 grain Speer Flat Base Spire Spire Point with 29 gr WW 748 C-T and shoot offs 5x5 chickens at 200 meters
160 grain Speer with 28 gr WW 748 R
Shot the jacketed bullets primarily in the 10" and 14" TC. The 7 TCU, 7 BR and 357 Super Mag all have the same H2o case capacity. Use commercial brass, not military, selected by capacity for match brass
My standing unlimited gun in 7 TCU
Attachments
Last edited:
HandgunHTR
Gold $$ Contributor
I built myself one on a Remington 700 action. It has an 18" barrel and with the carbon fiber stock, it weighs just over 7 lbs scoped. It is the perfect short-medium range whitetail rifle. Load is H4198 and 120 grain Nosler BTs.
Attachments
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.