Yes. But (as others have already posted)... but... Context matters.
GC on the right alloy (you can properly assume a properly chosen alloy from a commercial caster, especially one promising crazy velocities)?
Proper hardness/tensile strength for the operating pressures resulting from the powder charge producing those velocities?
And perhaps arguably the most important context: the optimal fit of the bullet into the ball seat/leade of your chamber.
You can simply keep increasing a properly chosen powder to get you to higher velocities, and safely - but that doesn't do you much good if the bullets end up grouping more like a 12 gauge firing buckshot, barrel leading, etc. I've gotten my best results as far as increasing velocity while maintaining grouping ability by learning to be obsessive about bullet fit to ball seat/leade. In cast bullet benchrest competition, some competitors even with their moulds made to their specifications to fit custom cut chambers, as a last stage put their cast bullets through a bump/swage die to get the best fit possible to their rifle chambers. e.g. CBA Rulebook: Enlarging or reducing a cast bullet by bumping or swaging is permitted.
Casting for my No.4 Mk1 Long Branch and a few others, my final stop has been ordering a custom mould from Accurate based on measurements from a chamber/ball seat/leade casting. Done properly, my personal belief is that unless your rifle is capable of extremely good accuracy with jacketed bullets, going the extra route of ordering a custom cast bullet bump/swage die to run your cast bullets through is going to get you nothing more than an expending extra time and effort to be done on the way to the completed ammunition.
As you are purchasing commercial cast bullets, you're limited on bullet form/size to what the commercial caster is offering you, and his advertisement that he can control the dimensions to .001" on all the bullets' surfaces by some coating material (Hy Tech?). A mould from a custom mould maker like Accurate allows you to choose the bullet form you like for your purposes (and preferably close to what your chamber cast dimensions tell you), and then specify the dimensional changes you want for casting with the alloy you specify. Accurate has regularly delivered moulds that dropped bullets right at the dimensions I specified using CWW.
Through sizing your bullets, you have some control/latitude with the finished dimensions of your cast bullets, whether you cast them yourself from an off the shelf mould, a custom mould, or purchase them from a commercial caster. NEIs very nice and very inexpensive bullet sizing system allows you to either size base first, or nose first. Which allows you to not just size the entire bullet from end to end, but alternatively, to size the base or just a part of the base of the bullet, or to size just a portion of the nose, just enough to allow an oversize bullet to just seat into the ball seate/lead.
And finally, to achieve velocity potential while maintaining grouping capability, matching the bullet hardness to working pressure of your loads. I started my bullet casting journey back in the late 1970's under a man who was one of the gurus and leading experimenters with cast bullets, Ken Mollohan. At the time he died a few years ago, he had probably forgotten more about successful bullet casting for rifles than most people like me will ever learn in a lifetime. He was a regular contributor of technical articles in the Cast Bullet Association journal, particularly when it came to cast bullet hardness/tensile strength as well writing small technical portions of some editions of Lyman's Cast Bullet Handbook.
Ken and another cast bullet guru from the 80's and 90's, Tom Gray, could repeatedly develop high velocity loads for rifles. If I recall correctly, Tom Gray for a period was placing in cast bullet bench rest matches with a load in .308 Winchester that was around 2800 fps. That was long before coated bullets, and the rifles they were using in cast bullet competition back then probably weren't your average off the rack rifle without anything done to it like your Ruger. But both put a lot of time into heat treating their bullets to give their bullets the tensile strength they needed to handle the pressures that delivered those higher velocities.
Anyways, a cut 'n paste from my digital library that I believe dates back to the late 1980's/early 90's; I think it's from Ken, but perhaps from Tom Gray. I think it has spread/reproduced/replicated numerous times in the cast bullet world since I saved it. Ken Mollohan was a very fine man and a great friend, and his death a couple of years ago was a real loss to many of us, and not because of his encyclopedic knowledge of technical issues concerning bullet casting.
Hope the tables and whatnot display properly:
HEAT TREATING WHEELWEIGHTS
Heat treating wheel weight alloy is both controllable and predictable ie: It is possible to heat treat wheel weight bullets and predict the final hardness to be achieved.
Hardness does not increase until the quench temp (after a ½ hr heat soak) reaches 420 deg. F. as measured with a digital thermometer shaded from any direct radiant heat.
Temperature vs. Resulting Hardness
410 12 BHN
420 15 BHN
430 17 BHN
440 23 BHN
450 29 BHN
Conclusions:
Exceeding 450 did not cause any significant increase in hardness.
460 deg was very close (read that too close) to the plastic deformation stage of the alloy
OPTIMAL HARDNESS FOR OPERATING PRESSURE OF LOAD
Tensile strength of lead/lead alloys = BHN x 480
****Best bullet performance is usually at pressures between 3 and 4 times Tensile strength.****
ALLOY BHN TENSILE STRENGH (PSI) TIMES 3 GIVES MIN. CHAMBER PRESSURE (PSI) TIMES 4 GIVES MAX. CHAMBER PRESSURE (PSI)
PURE LEAD 5 5(480) = 2400 7,200 9,600
1-20 Pb/Sn 10 10(480) = 4800 14,400 19,200
WHEEL WEIGHTS 12 12(480) = 5760 17,280 22,040
LYMAN #2 15 15(480) = 7200 21,600 28,800
LINOTYPE 22 22(480) = 10560 31,680 42,240
HEAT TREATED WHEEL WEIGHTS 30 30(480) = 14400 43,200 57,600
Common BHN measurements:
Pure lead 5 BHN
Wheel weights 8-13 BHN, composition varies
Lead/linotype 15 BHN, half and half
Linotype 22 BHN
40-1 Lead-tin 8.5 BHN
30-1 Lead-tin 9 BHN
20-1 Lead-tin 10 BHN
16-1 Lead-tin 11 BHN
10-1 Lead-tin 11.5 BHN
Lyman No. 2 15 BHN
Heat treated 25-35 BHN, varies with heat treat and age
Wheelweights
