7mag load help

[Carbon_15]

I'm trying to develope a load for my Father-in-law for a guided whitetail hunting trip in Kansas. He wants a 7mag load that will stay in a 5 in circle out to 300 yards. By my calculations he need a 140 grain bullet to be traveling at about 3200-3300 FPS from the 26 in barrel of his Thompson Pro-Hunter. On hand I have Benchmark, IMR 4895 and IMR 3031.
I would like to avoid buying another powder just to load 40 or so purpose built rounds for a specific hunt.
Anyone know a load using these powders that will get me in the 3200-3300fps ballpark safely from a 26 in single shot Thompson.
Thanks
Jason

 

[rbernie]

Not likely gonna happen - those powders are too fast to give top velocities for a chambering like the 7mm Mag. The best you're likely to get is 3100 fps from a max load of IMR 4895 (55gr or thereabouts - work up to this as usual), and only that because of the 26" barrel.

You'll do far better using a slower powder like Reloader22 or IMR 7828, or simply accepting the fact that the PBR of 5" is just too optimistic.

 

[HSMITH]

Reloader 19 and 160 grain Sierra Gamekings. Work the load up to best accuracy and call it good.

I don't like 140 grain 7mm bullets, not even for whitetail deer. Finding a bullet that will hold up to the 3200 fps impact velocity of a 40 yard shot is also tremendously challenging.

Pick a quality heavy for caliber bullet and load for accuracy, that is far more important than 2" flatter trajectory at 300 yards.

 

[GooseGestapo]

H4831sc (short-cut)

(I'M ASSUMING YOU ARE TALKING ABOUT A 7mm Remington Magnum)
You need to verify WHICH 7mag you are loading for;
7mm RemMag
7mm Weatherby Mag
7mm Rem Ultra Mag
7mm Rem Ultra ShortMag
7mm Win.Short Mag
ect.......................

Start at 62.5gr under a 140gr Sierra BTSP GameKing. Seat to 3.250".
Federal #215primer. Cases trimmed to min. spec.
Work up at 1.0gr to 65.5gr. Then 0.5gr to max of 67.0gr (Hodgdon's Max) (7MM REM MAG.)

I've found that most rifles peak on accuracy at 65.0 to 66.0gr.
These will chrono at 3,250fps at ~66.0gr (where I usually stop)
(from a 26"bbl, 24" will run slightly lower)

To get your point blank range: sight in 3.0" high at 100yds. Peak rise will be 4.0" at 170yds, and 5" drop will occur at 363yds.

To confirm this, go to www.Norma.cc/htm_files/javapagee.asp
Select "define your own bullet".
The Ballistic Coefficient of the Sierra BTSP is 0.418
For the following:
Nosler BallisticTip and Accubond: .485
Nosler Partition: .434
Hornady BTSP Interlok: .453
Hornady SST and Interbond: .486

A friend of mine for whom I worked up this load for his Savage M110 used this load to kill a 245lb field dressed 12pt. whitetail at a lased 440yds across a pasture. He held just over the top of the deer's back, and held approx 18" into the wind (I gave him the phone# for the local airports automated weather reporting service to call before he got into his shooting house, and gave him a "windage chart" to go with the "drop chart".
One shot, DRT! Bullet exited far shoulder.
That was in 1999. He's still shooting out of the same box of 50 I loaded for him.
I failed to mention that the rifle shoots sub-moa with 66.0gr of H4831sc.

 

[dakotasin]

foolproof 7 rem mag load: 162 hornady interlock btsp, and ~70 grains rl-25.

rl-22 and h-4831 are excellent 2nd choices w/ 140-160 grain bullets.