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Posted: 3/30/2009 3:03:05 PM EDT
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Iv'e been reading about the 7mm TCU........from what I understand it is the 223 case necked up to 7mm....correct?
It's ballistics are just under the 6.8spc. Just wondering why you don't hear that much about it and that it is not more popular. Any insight? |
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Randy,
While I do not have AR experience with the 7mm TCU, I do with the 6x45 which is similar in theory. The 7mm TCU is considerably slower than the 6.8, and suffers the same disadvantage that my 6x45 (pretty much a 6mm TCU) does, namely case capcity. With the 6.8, you have the short fat case advantage, for powder and bullet length. The TCU rounds do a lot better in platforms such as the Contender, as you are reduced to single shot, which allows long seating of the bullets. When you start taking larger (than 556) calibers and stuffing them in the 556 case, you will always fight OAL and case capacity, if you plan on having the gun function with the magazine. When you look at TCU numbers on the web or in reloading manuals, you need to evaluate the OAL listed. I think many times you will find higher velocities associated with bullets that are barely into the case, and way too long for the AR magazine. The TCU series does have some level of usefulness in the AR15 platform, but most folks look at the trade-offs and opt for a little to a lot more gitty-up. Craig |
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It was / is chambered in the Thomson Center (TC) single shot pistol. Easy to load for, and got my last deer & antelope with one.
If you want one check out http://www.sskindustries.com in Ohio. Lots of JD Jones cartridges based on the 223 case. The 6mm is also a good one (have not owned one). |
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I have an AR pistol that is chambered in 7 TCU. For one, I think the magazines have to be modified for the thicker neck, I know mine is. I used it for silhouette shooting many years ago, and I have been able to load 140 gr Nosler BT's to knock down the 50# Rams at 200 meters. |
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Quoted:
I have an AR pistol that is chambered in 7 TCU. For one, I think the magazines have to be modified for the thicker neck, I know mine is. I used it for silhouette shooting many years ago, and I have been able to load 140 gr Nosler BT's to knock down the 50# Rams at 200 meters. Have you tried using the 6.8spc mags with a .223 follower? |
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Quoted: Quoted: I have an AR pistol that is chambered in 7 TCU. For one, I think the magazines have to be modified for the thicker neck, I know mine is. I used it for silhouette shooting many years ago, and I have been able to load 140 gr Nosler BT's to knock down the 50# Rams at 200 meters. Have you tried using the 6.8spc mags with a .223 follower? Huh? I'm still using the same mag I bought with the gun 20 years ago  |
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I had a Pachmyer Dominator pistol chambered in 7 TCU for awhile. I'm not a big fan of the cartridge, especially for hunting. I have shot 100's of game animals over the years with everything from 222 to a 340 Weatherby Mag, and there are two ways I have found to consistantly kill game. With a small fast bullet, or with a big slow bullet. When you combine small and slow, you're screwed.
Tony |
| We just built a bolt action AR in 7 TCU for my dad. Not for any particular reason other than he's got a bunch of TCU stuff. We went with bolt action because he loves to run reduced loads w/cast bullets. I concure with the group, if you are looking for power, 7 TCU is limited compared with other chamberings available in the AR. |
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The 7mm TCU will find the OAL required to operate in an AR15 magazine overly constrictive. Most, if not all available load data would be invalidated by having to seat the bullet .25"+ deeper in the case. The reduced case taper will require you to relieve GI magazines at the shoulder (although there could be some aftermarket magazines that work out of the box.
There are lots of good reasons this isn't done more. |
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Quoted:
It works really well with 110 and 120gr bullets. Very much like shooting an AK round. Here's the best AR mag option for the TCU to-date: http://i129.photobucket.com/albums/p203/CHRIS65-IL/7MM-TCU-PMAG20b001c.jpg Or... take a 17 remington neck it up to .277 and trim to 42.5 mm .... and use 80-115gr SPC bullets. Just as much useful powder capacity , better bullet seating , wider range of bullets available in envelope. Velocity, trajectory, range , energy much improved over M43. advantage : mags , bolt , brass Disadvantage: reamer , dies , bullets .277 (6.9 mm) is almost 7 mm !
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Quoted: It works really well with 110 and 120gr bullets. Very much like shooting an AK round. Here's the best AR mag option for the TCU to-date: http://i129.photobucket.com/albums/p203/CHRIS65-IL/7MM-TCU-PMAG20b001c.jpg How do you file down the inside? I'm thinking getting a file in there isn't easy. If you have a milling machine, this is probably the easiest way.  |
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Quoted:
How do you file down the inside? I'm thinking getting a file in there isn't easy. If you have a milling machine, this is probably the easiest way. No problem - remove mag floorplate, spring, follower, and start filing on inside. Use a file with a handle attached, as it allows you a longer stroke thru whole mag. A good ten minutes on each internal rib and you're done; reassemble; wa-la. 
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