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Flat Point Solid Bullet in .500"
From the GSC website: the 540gr bullet from a .500 NE on the left was recovered from the ground after an elephant was given a security head shot. Compare it to an unfired similar type.
According to GSC the design drivers for a solid dangerous game bullet are the following (I agree): 1. Not break up or shed weight, so that maximum momentum is retained. 2. Be tough enough not to bend in the shaft, as this will cause deflection from the bullet path. 3. Present a vertical face to the direction of penetration. It is the most efficient shape for disruption of tissue. 4. Have a centre of mass that is forwards of the centre line so that it will remain heavy side forwards. 5. Be as short and stubby as possible to minimise the tendency to tumble in tissue. 6. Have as much velocity as possible for elevated shoulder stabilisation, cavitation, momentum and impulse levels.
[comment: The very reason for the historical failure of the .458 Win Mag in Africa].
7. Be as kind to the bore of your expensive double or custom bolt action as possible.
For the non-dangerous game hunter GSC manufactures the following types of bullets:
Hollow Point:
Recovered from game, retaining 95% weight.
In my opinion this is beneficial to the American hunter using a high velocity magnum rifle and still believing in a heart shot through the shoulder without the stomach turning meat damage caused by lesser designs. A clever bullet to bring to Africa where your PH will invariably insist on a low shoulder heart shot. In my opinion this at least equals the Barnes X series with the added advantage of not shedding the petals above 2,600 ft/sec impact velocity.
The new standard: The HV range, utilising narrow drive bands. GRC claims that these bullets shoot consistent groups no matter the velocity:
I believe this is the bullet that the Barnes TSX series needs to emulate: consistent petal development from 1,800 ft/sec to 3,000 ft/sec impact velocity.
Blesbok entrance wound: impact velocity 4,400 ft/sec from a 5.56x64. Orders of magnitude less meat damage than a .243 W.
The Very Low Drag Range. Designed for the tactical sniper, target shooter and the South African professional game culler:
Next post will be some questions I had for GSC on these bullets and their answers.
Until then.
That is subsonic aerodynamics. Once the velocity is over Mach 1.2 there is a change how drag manifests, and then again beyond the critical drag rise Mach number (Mach cdr). Mach 1.8 is a turning point again and we are in the Mach 2.0 regime here.
I must disagree, if only by the Ballistic Coefficients published by the manufacturers. This is why the new automobiles have rounded fronts, etc. The flat fronts create turbulence. Tests prove this to be fact.
The total drag (profile and skin friction) on a straight angled nose to the virtually flat point is less than had the bullet been slightly shorter in the classic straight shank and round nose design like the original Hornady 500 gr FMJs.
Neat! Actually though, the average would be between .149 and .173. My software has slots for these so I will recompute.
Entering the entire table I get 2073 fps at 50 yards.
Look at this here. The .149 is for the drag coefficient of 2,700 ft/sec and up.
http://www.gsgroup.co.za/458450FN049.html
I looked at their web site and it showed 0.149, not 0.173. Maybe a different page than the one I was looking for? I did not see a breakdown of velocity vs BC.
Michael wrote: "The 0.149 BC 450g flat head looses velocity extremely fast according to my ballistics software, which is very well respected. From 2350 fps at muzzle to 2073 fps at 50 yards."
The BC at the average velocity of that bullet if launched at 2,350 ft/sec is .173. My calculator shows 2,114 ft/sec at 50 yds which is just above the theoretical minimum we want.
I only had time last night to thoroughly read through the GSC website. Being a specialist in quality management systems and inter alia cnc production quality control and quality assurance processes I appreciated what is shared here:
http://www.gsgroup.co.za/12about.html
I agree with that assessment. It is actually with great pleasure I note this has turned around. One thing though. The 0.149 BC 450g flat head looses velocity extremely fast according to my ballistics software, which is very well respected. From 2350 fps at muzzle to 2073 fps at 50 yards.
Of course - both have an influence - but it still is not the rated velocity for the load. With the crimp added the rated pressure and velocity will be achieved.
Notice that the 3.48" shot had 2.3 grains more powder than the first shot, as allowed by the increase in volume. This may have had more to do with the increased velocity than the lands.
The classic demonstration that a very slippery bullet needs mechanical hold-back for the pressure curve to gain its required slope in order for the rated pressure to be achieved, and for the correct, fast burning propellant to be used to fill the increasing volume behind the departing bullet with expanding gas at a rate which is quicker than the rate of volume increase.
The extended bullet had that mechanical hold-back supplied by the lands. Crimping the bullet will give it the extra needed hold back and higher inertia to ensure the proper pressure slope for 2,350 ft/sec which is achieved with a standard cartridge length.
Today, Sunday June 4, 2017 I continued my efforts to prep my 458 Winchester Magnum and my 35 Whelen for upcoming adventures in Africa.
I took five shots with the 450g GC Flat Head bullets using BLC2 Powder.
Note that I based this first BLC2 effort on known loads for conventional bullets, planning to use velocity to gauge pressure in accordance with Quickload. I find Quickload accurate for relative changes to book loads, if not always so accurate with absolute calculations.
First Shot: COAL 3.278", 78g Powder No crimp: 2236 fps.
Second Shot same as first with gas check: 2230 fps. Realize the first shot was with a clean, lubricated barrel, so I take this result to mean the gas check made no difference.
Third Shot: COAL 3.25", 78g Powder Crimped : 2286 fps.
Fourth Shot: COAL 3.278", 79.2g Powder, not crimped: 2273 fps **
Fifth Shot: COAL 3.48" hand inserted, 81.5g Powder not crimped: 2316 fps **
There were no over pressure signs at all, and the action cycled smoothly.
So it looks like by simply crimping the loads of the 4th and 5th Shots I am in the 2325-2366 fps range. I consider this a success, and hope to verify the scope settings next time out. I notice that at 25 yards the bullets were hitting in the same place as the Barnes 450g TSXFB. According to the ballistics, the GC Flat Head drops off away from the TSX considerably after 100 yards.
The 35 Whelen needs a little more powder because I was getting 2657 fps first shot with a conservative load of BLC2 and Barnes 225g TSXB bullets. I can kick this up a bit to 2700 fps.
Test related comments to be posted in the Bullet Behaviour Category.
Asked around here - popular bullets in all the categories - .375 H&H and the .458s particularly. Demand outstrips production.
You know the Barnes 450 Banded Solid has a huge band at the bottom. The whole bottom 20% of the cartridge is a solid band. In my opinion GS should take note of this. I am getting 2285 fps out of Factory ammo there.
That's if I can get the GS to 2300 fps at the muzzle. The others are already proven.
The 450 TSXFB is 2117.8 at 50 yards. The 450 banded solid is 2170 at 50 yards. The GS 450g is 2026.8 at 50 yards. The Hornady 480g steel jacket is 2056.5 at 50 yards.
Say again the weight of the Barnes and velocity at 50 yards?
Any amount of engraving into the bands by the rifling will rotate the bullet without longitudinal slippage so I doubt if gyroscopic rigidity will suffer.
Some rifles, especially the most accurate from my experience, have very shallow rifling. That is the case with this rifle. It is a custom barrel, not fired much by the old gentleman I got it from. Got it from his wife actually after he died, for a song so to speak. That, combined with the thin bands may be a combined problem. If that is the case, the gas check should help. On another note, without good contact perhaps the spin will suffer. Won't know unless I can get the speed up. They landed in the same group as the Barnes sight in rounds, about two inches lower at 50 yards anyway. Did not shoot but two GS and then knocked the rest out. Then the Barnes were all inside 3/4" at 100 yards after they got sighted in. Those are still 4,010 foot pounds at 100 yards. Even if I get the GS up to 2300 fps they will be 3142 foot pounds at 100 yards.