The following data was developed in an A-SQUARE Hannibal model rifle. The rifle weighed 13.6 pounds. No effort was made to shoot it for group accuracy, as the whole purpose of this rifle is as a last resort stopper for animals that are intent on changing the make up of your anatomy! Suffice to say that all groups with all powder charges, at various velocities, went into a group of approximately 8 inches, at 100 yards, with the majority of the higher velocity loads grouping in less than 3 inches! This is fantastic accuracy for a rifle of this power, with open sights.

We could not approach the published velocities in the excellent A-SQUARE reloading manual, with their listed powders. As an example, they listed 177.5 grains of Reloader 19 for a velocity of 2473 fps. We used 178 grains of our lot of Reloader 19 and only managed to get 2283 fps. That is almost 200 fps less! Their data was apparently developed in a barrel of 26 inches, while ours measured only 23 inches. Still, this is no criticism of A-SQUARE, it just shows the differences you might get by using different rifles and different lots of powder. In the velocity department, we were able to increase the velocity to over 100 fps more than the maximum published by A-SQUARE, by using a powder they did not use. There was no sign of excessive pressure at all, in fact, we think that 2600 fps is quite feasible in this rifle without too much trouble – except recoil! We only stopped because we ran out of bullets!

And talking of recoil, this rifle has is it in spades! Admittedly, it is fitted with the A-SQUARE Coil-Check stock, which has three mercury reducers and the pad area is significantly larger than a normal stock. Both of these modifications to the stock will help reduce recoil. Still, any cartridge that produces over 11,000 foot pounds of energy is going to give you a good whalop. And I guarantee you, you are not going to be disappointed!

Credit must be given to A-SQUARE for designing and bringing out a number of very high velocity cartridges in their caliber, like the 300 PEGASUS and the 338 EXCALIBUR. Also they produce factory ammo for many wildcats and old cartridges. We have one of their HANNIBAL rifles in 300 PEGASUS here for load development. As soon as our testing is complete, we will put it up on the site.

I have a Ruger #1 rechambered for the 460 Weatherby magnum, and a Dakota 76 custom rifle chambered for a wildcat cartridge based on the 416 Rigby case necked up to 475. The recoil of the 577 Tyrannosaur at velocities of 2150 fps and below is comparable to the above mentioned rifles. Once the velocity gets to 2400 fps, then the recoil is very severe. And at our maximum of 2581 fps, it is plain painful!

Personally, I would take my chances with a charging elephant or buffalo armed with a 460 Weatherby magnum, or even a lesser cartridge like the 375 H&H magnum, rather than the 577 Tyrannosaur. I know I would be scared of the recoil! Also, please bare in mind that WHERE you place the bullet is more important than the SIZE of the bullet! I have shot a number of elephants, and dozens of cape buffalo. Most of them with a 375 caliber wildcat based on the 404 Jeffery. The majority of them are one shot kills, and according to my professional hunter, with over 30 years of guiding, they do not seem to go any further than when shot with larger caliber rifles.

We have a HEYM bolt action rifle chambered for the 600 Nitro Express cartridge. We are still waiting for our supply of bullets, and as soon as we get them, we will try to develop some loads for it. It would be interesting to see this cartridge performs in a bolt action rifle.

We used the Federal 215 primer, and the Barnes monolithic solid 750 grain bullet, and the overall cartridge length was 3.710 inches.

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