My rifle is a Thompson-Center 21" factory barrel on either of my two Contender frames. It was one of the first barrels purchased for the Contender due to its purported versatility. However, I think the strong suit of the cartridge is that brass is based on the VERY available and inexpensive .223 Remington. I am one of those who doesn't mind using military brass and find it gives very similar results to commercial brass both in forming and in performance. The only reason I prefer commercial brass is that the primer pockets must be swaged to remove the crimp on military brass. My barrel is an early one with only one dovetail lock for attachment of the forearm. That has not been a problem as this is a low recoil cartridge.
I liked the cartridge so much that I later acquired a 10" barrel, the metallic silhouette standard, to see how it would perform in the shorter length. True to expectations the short barrel gave approximately 400 fps less velocity compared to the 21" "big brother". Unfortunately, I'm not that enamored of the short barrel. It works and that's about all I care about it. I really concentrated on the 21" barrel as you can see in the tables below.
|Sierra SSP||130 gr.||H4895||29.4||2040||1201|
|Sierra HP||115 gr.||H4895||29.0||2337||1395|
|Hornady SSP||120 gr.||H335||30.0||2446||1595|
|Hornady SSP||120 gr.||H322||26.0||2234||1390|
|Sierra SSP||130 gr.||H4895||29.4||2460||1747|
|Hornady FP||139 gr.||H4895||29.0||2024||1260|
|Hornady FP||139 gr.||H335||29.0||2117||1383|
|Sierra SP||145 gr.||2400||10.0||1385||618|
While I still have a quantity of these bullets remaining, the Sierra and Hornady SSP bullets have been discontinued as has the Hornady 139 gr. FP originally intended for the 7-30 Waters. Not to worry. John Haviland in Handloader Magazine #264 tested the Sierra 140 gr. SP, Sierra 150 gr. BT and Hornady 162 gr. A-Max and found that they all expanded at only 1000 fps striking velocity. This means that any number of 7mm/.284" bullets are usable in the cartridge.
Although I didn't use it due to lack of availability, AA2460 seems to be the powder to use giving top velocities with bullets of all weights. Regardless of powder I've never been able to attain "book" velocities in my 21" barrel. I'm not sure why, but I hit signs of excessive pressures before I reach the velocities the manual says I should be getting.
- Shooting A T-C 7mm TCU by Junior Doughty