7mm tcu for HP

[RamSlammer]

One of my mates has just got a 7MMtcu rifle and I wonder if anyone has experimented with one as a silhouette round. Also what loads worked best.

[davei]

used one with great results for about 4 years for hp silhouette.  folks laughed at me until i took third at nationals with it.  well...  they continued to laugh at me but, after 17 years, i'm just about over it!  

wonderful rifle.  extremely accurate with very little recoil.  biggest challenge was a very slow velocity which allowed for lots of wind drift.  since then powders and bullets have both improved so, with the right load, one should be able to get better results.  Anyone with recent experience?  Any propellar heads out there with ideas?

[oldnslow]

would be a great little gun to club seals to death with    

[DanDeMan]

RamSlammer,

The 7TCU should work well for your mate.  The first place to start is with the barrel twist.  What is the twist?  From there the appropriate bullet can be chosen for the short animals and rams.  A 9-twist is minimum for good results.  Also, chamber throat has a substantial effect on how well the cartridge will work for HP Silhouette.  It the chamber is not throated properly it will be tough to get enough powder in the case for a decent ram load.

For starters, if the chamber is properly throated, I’d go with the 162 Hornaday A-Max or 168 JLK as long as the twist is 9 or faster.  For ram bullet powder go with RL15, VVO N140 or VarGet.  A full case of powder, somewhere between 29 and 30 grains should launch the bullet to about 2,250 to 2,300 fps.  I’d also shoot the heavy bullet at C, P & T’s with a faster powder at about 1,800 fps.  A powder like N133 with a charge of about 25 to 26 grains should work well for the reduced velocity charge.

If your mate wants to go with a lighter bullet the 139 Hornaday Spitzer BT is a cheap, accurate choice, but the heavier bullet at 1,800 fps will out-shoot the 139’s even at 2,400 fps which is about the fastest a 7TCU will drive 139 bullets.  Wind deflection is reduced by shooting the higher BC 162 A-Max or 168 JLK at 1,800 fps compared to the 139’s at 2,400 fps.  Also, recoil will be noticeably milder with the slower, heavier bullet.

[DanDeMan]

Guys,

I just ordered a few things from OK Weber yesterday.  They sell the 168 JLK 7mm bullet at a cost of $30 for 125 bullets.  This is the best 7mm ram bullet out there for silhouette if a 9-twist or faster barrel is used.  If the 7TCU is throated so that only the boattail is below the case neck/shoulder junction, 29 to 30 grains of N140, RL15 or VarGet will launch the bullet to about 2,300-fps.  Because the 168 JLK has such a high BC it will flat slam the rams.  When launched at 2,300 fps the bullet is still going 1,590 fps at the ram-line.  That translates into a terminal momentum of about 1.2 ft-lbs.  A 142-grain MK launched at 2,700-fps delivers a terminal momentum of 1.2 ft-lbs, the same as the 7mm TCU.  Also, it should be noted that the heavier 7mm bullet will be more effective at knocking down rams as the heavier bullet requires more energy to blowup and that translates to more efficient ram knock-down.