I am having a ball working up loads for a friend's 505Gibbs. 3moa 650gr cast bullet in front of 120gr of IMR7828. 2030fps and sub-2moa 5-shot groups at 50 yards. Tomorrow we try the same charge of AA3100. Pray for me.

Rich

found a much better load this morning at the range. 120gr of Vihta Vuohori N160 with the cast 650 RFN.
2089fps avg for three shots off the bench. 88 ft lbs of recoil energy, 21fps recoil impulse speed, 6300ft lbs of ME. Three shots in 3" at 50yds, two touching. Tomorrow we load ten more and have another crack at it. This could be THE load for the 505 factory equivalent cheap cast loads.

Rich

I have now shot almost sixty rounds of this load off of the bench with no ill effects to date..except the need to actually build one myself is growing by leaps and bounds.

Rich

This weekend I'll be testing/ trying out some with the 505 Gibbs as well. 130 grains IMR7828 behind one of Mac's flat nose solids as this was all the coal I could shoval into the case. Will also be loading with reloader 15 and 19 among a few others. Rodney.

I think Rich got his best results with V-160 but he and a couple other guys used RL-15 with that bullet as well. Seems to have more recoil and less velocity than the V-160. Rich might clarify. Any new data would be helpful!!

Have fun!

Shot the 505 this afternoon with the 130grains of IMR7828 and Mac's flat nose solid. No pressure signs to the cases and no hang fire as the long solid just sits flat on the powder with no air space in the case using new un-fired brass headstamped BR&C. The following are estimations: chamber pressure 37,427 PSI, muzzle pressure 8,413 PSI, velocity of 2238 FPS with 88.3% propellent burnt. More experimenting to come. Rodney.

Wanted to add a comment about accuracy and recoil. The rifle weighs in at 9.75 lbs exactly and kicks like a mule so I'm going to be loading only about 5 or 6 rounds at a time until I find a load combination for good accuracy and at the same time technique at firing. I have 5 more solids loaded with the IMR7828 then maybe I'll try 126 grains of N160. All estimations are from Quickload and I've had the maximum average pressure allowed at 39,160 PSI. Thanks to Marty, Derek of {Sportsman Guns and Ammo} Macifej, Jeffeosso, and Idaho Sharpshooter for the rifle. Rodney.

More data about the rifle as I've seemed to have left this out of previous posts: CZ 550 Magnum 9 3/4 lbs, barrel 24"s and 1 turn in 10" of travel or 1 in 10 twist. Currently working out some loads and will loading first of the week. Rodney.

Some results and still working- 130 grains imr 7828 and 558 gr FN solids shoots about 6 inches high at 50 yards with factory express sights. Adjusted loads with imr 7828 to five more at 125 and an additional five with 127 grains powder to reduce velocity slightly- but not too much. Recoil is is there and do not like shooting off the bench bacause I cannot roll with the forces. Shooting sticks are the way to go for accuracy with heavy hitters otherwise get close to your game. Rodney.

The 130 grains imr7828 and 558 grain fn solid load penetrated 12 5/8" of dense-packed magazines in straight line. Velocity about 2230 fps and energy about 6,100 #'s. Different loadings coming soon, thinking about a 132 grains of reloader 22 with same bullet for potential 2300 fps and 500 more pounds of energy. Earlier posting I was adjusting loadings for accuracy and hog plinking. I'm looking for the best combination in speed and accuracy specifically for hunting. Rodney.

Had to lay out for a while due to back injury but I'm getting back to the loading bench and will be starting with 130grains Reloader22 and see what it looks like in case with 132gains being my maximum. This is a fun shooting rifle and expect it will be one tough hog thumper. Rodney