Here is a photo of the gas checked GS 450 .458 Flathead. I bore down on this with calipers and they hit the gas check first. That tells me the bullet bands are not as tight in the barrel as the gas check. I use these gas checks on 425g Hard Cast Lead bullets for my 45/70 double rifle and they work splendidly to give me 1850 fps with AA2495 powder. I will shoot this bullet next weekend to compare with a non-gas checked bullet. I suspect there will be a difference in velocity. This bullet was extracted from an unfired round. It drops right to the bottom of a fired case without the gas check.
Recovered bullets will tell what happened in the freebore and the barrel. It does not matter if they are deformed, the shaft of the bullets will show whether they sealed or not and whether there was gas blow by.
The GSC FN bullet is 11.64 mm (.4583") in diameter and the throat of a .458WinMag is .469", just ahead of the case mouth, tapering to .450" over a distance of 1.115". The distance from first to last drivebands is 0.567" so there is no question that the FN bullet will seal the gas in the throat of the barrel, if the rifle has a CIP/SAAMI specification chamber. The bullet also has a boat tail with a 6 degree taper and the boat tail is 0.177" long. That is the reason why the last drive band is not at the base of the bullet.
The bullet is designed to work terminally on bone and tissue and any change of dimensions or adding or subtracting of weight will detract from the terminal performance of the bullet.
"The bullet base is convex, not concave". Sorry misread that so was stating the obvious and unrelated to the topic - staying up after midnight to not miss out on the information...
'Recovered', as I understand it, means recovering a bullet from a target after it is fired. We never let seconds out the door, we do not know the meaning of seconds, a bullet is either good or not good. The technical specification is either met or the bullet is scrapped. Our spec from batch to batch and within a batch is the tightest in the industry. From this page: http://www.gsgroup.co.za/12about.html
Bullet Design and Q&A
GSC bullets are designed to the following standard:
Diameter tolerance: + or - 0.005mm (0.0002").
Length tolerance: + or - 0.10mm (0.004").
Weight is within 0.25% of the stated weight.
Uniformity of ogive curve: - + or - 0.005mm (0.0002").
This is an overall standard that is maintained from batch to batch - not just within a batch.
Thanks for the theoretical, Gerard Sir. I measured the bands on this GS bullet to be .4570. I measured the Barnes bullet at 0.4575 with 0.443 channels. My lead bullets are 0.459 and the gas check shown is 0.461. As far as I can determine, there is one band of the GS bullet in the case when the nose hits resistance. I suppose my digital caliper is not lab quality, but the other measurements confirm it is correct with regard to them, so maybe it is wrong ONLY on the GS bullet? I have not slugged my barrel, but know that the Barnes bullets shoot more or less as Quickload predicts. The one session I have had with the GS bullets showed over 200 fps less than Quickload calcs using the data off the GS web site and with the low friction unchecked. To make certain this was not just a bad batch of Win 748, I am going to try what I know is a good batch of BLC2 and / or Xterminator. If the bullets pan out in that test and match the predictions more or less with accuracy, then very good even if I must gas check them.
Quite possible. Less powder space available however. Jury still out. After my next outing, more data available. I don't have any way to capture a bullet at the federal range. Need my private hunting lease for that adventure.
Also, I am using Hornady cases, but they are the same as Winchester I believe. After a load fails I usually pull the remaining un-fired bullets to re-use with a different load. When I knocked the GS bullets out of the cases they came out with hardly any effort at all, wheras I must beat the kinetic puller really hard to get the Barnes bullets out. The difference is very noticeable.
The general experience out here is that most of the imported (from USA) ammunition have thin walled cases. I had recent experience of new Remington cases for my .303 and which I had to discard after the first reload. That was a darn disgrace in fact. The only Remington product I still buy is their primers when I can not get local PMP primers.
Cassie related a light grip experience of GRC and Winchester cases in his 30-06. My own opinion is that with the driving bands the bullet friction is already low and a minute increase in driving band diameter may just be beneficial all round. A barrel slug always has value. In Colorado we in fact are setting up a slug archive system of all the rifles we shoot.
Yep, still not enough information to have a cause of the low pressure.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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Here is a photo of the gas checked GS 450 .458 Flathead. I bore down on this with calipers and they hit the gas check first. That tells me the bullet bands are not as tight in the barrel as the gas check. I use these gas checks on 425g Hard Cast Lead bullets for my 45/70 double rifle and they work splendidly to give me 1850 fps with AA2495 powder. I will shoot this bullet next weekend to compare with a non-gas checked bullet. I suspect there will be a difference in velocity. This bullet was extracted from an unfired round. It drops right to the bottom of a fired case without the gas check.
Recovered bullets will tell what happened in the freebore and the barrel. It does not matter if they are deformed, the shaft of the bullets will show whether they sealed or not and whether there was gas blow by.
The GSC FN bullet is 11.64 mm (.4583") in diameter and the throat of a .458WinMag is .469", just ahead of the case mouth, tapering to .450" over a distance of 1.115". The distance from first to last drivebands is 0.567" so there is no question that the FN bullet will seal the gas in the throat of the barrel, if the rifle has a CIP/SAAMI specification chamber. The bullet also has a boat tail with a 6 degree taper and the boat tail is 0.177" long. That is the reason why the last drive band is not at the base of the bullet.
The bullet is designed to work terminally on bone and tissue and any change of dimensions or adding or subtracting of weight will detract from the terminal performance of the bullet.
"The bullet base is convex, not concave". Sorry misread that so was stating the obvious and unrelated to the topic - staying up after midnight to not miss out on the information...
This is not a recovered bullet and your claimed measurements are not jiving mine in hand. Just saying wondering if I have seconds?
'Recovered', as I understand it, means recovering a bullet from a target after it is fired. We never let seconds out the door, we do not know the meaning of seconds, a bullet is either good or not good. The technical specification is either met or the bullet is scrapped. Our spec from batch to batch and within a batch is the tightest in the industry. From this page: http://www.gsgroup.co.za/12about.html
Bullet Design and Q&A
GSC bullets are designed to the following standard:
Diameter tolerance: + or - 0.005mm (0.0002").
Length tolerance: + or - 0.10mm (0.004").
Weight is within 0.25% of the stated weight.
Uniformity of ogive curve: - + or - 0.005mm (0.0002").
This is an overall standard that is maintained from batch to batch - not just within a batch.
Thanks for the theoretical, Gerard Sir. I measured the bands on this GS bullet to be .4570. I measured the Barnes bullet at 0.4575 with 0.443 channels. My lead bullets are 0.459 and the gas check shown is 0.461. As far as I can determine, there is one band of the GS bullet in the case when the nose hits resistance. I suppose my digital caliper is not lab quality, but the other measurements confirm it is correct with regard to them, so maybe it is wrong ONLY on the GS bullet? I have not slugged my barrel, but know that the Barnes bullets shoot more or less as Quickload predicts. The one session I have had with the GS bullets showed over 200 fps less than Quickload calcs using the data off the GS web site and with the low friction unchecked. To make certain this was not just a bad batch of Win 748, I am going to try what I know is a good batch of BLC2 and / or Xterminator. If the bullets pan out in that test and match the predictions more or less with accuracy, then very good even if I must gas check them.
Talked to Cassie Nienaber (internal/intermediate ballistics expert - Gerard may know of him). Two things:
a) the drive bands of GSC certainly make for a less tight bearing surface in the case mouth.
b) combined with the known Winchester / Remington thin walled cases this may very well produce low starting pressure. PMP cases would mitigate that.
Quite possible. Less powder space available however. Jury still out. After my next outing, more data available. I don't have any way to capture a bullet at the federal range. Need my private hunting lease for that adventure.
Also, I am using Hornady cases, but they are the same as Winchester I believe. After a load fails I usually pull the remaining un-fired bullets to re-use with a different load. When I knocked the GS bullets out of the cases they came out with hardly any effort at all, wheras I must beat the kinetic puller really hard to get the Barnes bullets out. The difference is very noticeable.
The general experience out here is that most of the imported (from USA) ammunition have thin walled cases. I had recent experience of new Remington cases for my .303 and which I had to discard after the first reload. That was a darn disgrace in fact. The only Remington product I still buy is their primers when I can not get local PMP primers.
Cassie related a light grip experience of GRC and Winchester cases in his 30-06. My own opinion is that with the driving bands the bullet friction is already low and a minute increase in driving band diameter may just be beneficial all round. A barrel slug always has value. In Colorado we in fact are setting up a slug archive system of all the rifles we shoot.
Yep, still not enough information to have a cause of the low pressure.
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.
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.
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.
That's if I can get the GS to 2300 fps at the muzzle. The others are already proven.
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.
Asked around here - popular bullets in all the categories - .375 H&H and the .458s particularly. Demand outstrips production.
Test related comments to be posted in the Bullet Behaviour Category.
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.
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.
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.
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.