My first centerfire rifle was a Winchester Model 70 in .243 Winchester topped with a 2.5X8 Leupold scope. That fall, I used it to take my first deer with a rifle. I shot the deer at a distance of 75 yards with a 100 gr. Hornady bullet, that at impact, was moving at 2900 fps. The deer was small, weighing less than 100 lbs. The bullet exploded on the deer’s ribcage with the shrapnel from the bone and what was left of the bullet shredding one lung and its heart. The entrance wound was the size of a basketball and there was no exit wound. While the deer only staggered a few yards from where it was hit, I was thankful that I hadn’t hit its shoulder blade. The tracking job might have been longer and the outcome far worse. So, it was with my first rifle shot on deer that I really started to worry about bullet construction. From then on, I saved the 100 gr. Hornady’s for practice and used 95 gr. Nosler Partitions instead. For those unfamiliar with Partitions, they are bullets with a lead front core and solid copper middle that protects the lead filled rear core. If you were to saw them in half length-wise, they would look like an “H”. While the front of a Partition might blow off (and in fact, they usually do), the front jacket will still expand nicely against the partition affording the lead filled shank to completely penetrate game.
Bullet construction became even more relevant when I moved to a .300 Weatherby. It takes exceptionally strong bullets to survive impact velocities in excess of 3000 fps. Here I have limited myself to 150 gr. Partitions, 165 gr. Swift Sirocco’s (a plastic tip, heavy jacketed bonded
core bullet) and 180 gr. Barnes X-bullets (solid copper hollow point bullet). All have given fine performances on whitetail, antelope and muledeer at ranges from 100 feet to 350 yards. When I drew my antelope tag this year, I decided to take my newly acquired Sako Mannlicher Carbine in .308 Winchester. This slick little rifle has a 20 inch barrel and weighs under 8 lbs. scoped and loaded. I could drive tacks out to 200 yards (the limit of my home shooting range) with 150 gr. Sierra Gamekings and a full charge of Alliant Reloder 15. The muzzle velocity of this load is a chronographed 2750 fps; a full 100 fps less than what the reloading manual claims for a 22 inch barrel.
I was happy with the performance of the load but was allured by the Combined Technology 150 gr. Partition. These bullets are the product of a joint venture by Winchester Ammunition and Nosler. They differ from Nosler’s standard partition in that the front core is smaller and the rear lead core is steel reinforced. I loaded these in place of the Sierra’s and found that they were just as accurate and the point of impact was the same. While I had never used the Combined Technology bullets on game, I was more comfortable with them because of my experiences with the Partition. I figured that like the regular Partition, if I hit bone, they would hold together and if I didn’t, the front would still expand. When my daughter shot her antelope with this load at 250 yards, the expansion appeared to be a bit poorer than I expected. The next day when I shot mine at 300 yards, the entrance and exit wound were .308" in diameter: in other words the bullet behaved like a solid. If I hadn’t shot him through the heart he likely would have gotten away. While both antelope were put on the ground with the first shot, both required follow-up shots to what should have been killing shots. While I’m reminded of the old adage, “at what point in the animal’s death did the bullet fail?” I was still disappointed in the outcome.
With this in mind, I decided to determine how the 150 gr. Combined Technology bullets compared to the 150 gr. Sierra’s as a function of velocity. I also decided to test 150 gr. Winchester Power Points that I had on hand. This would cover the range of expensive premium
bullets (Combined Technology), moderately priced, but top quality non-bonded cup and core bullets (Sierra Gamekings) and cheaper mass produced bullets (Winchester Power Points). In this test, I decided to determine how well these bullets would perform at .308 velocities at 300 yards and .300 Weatherby velocities at 300 yards. To do this, I used the RCBS external ballistics program to determine the 300 yard terminal velocity of a 150 gr. bullet with initial velocities of 2750 fps (.308 Winchester) and 3400 fps (.300 Weatherby). According to the external ballistics calculator, the 300 yard terminal velocity of the .308 Winchester and .300 Weatherby is 2100 fps and 2650 fps respectively.
I tied up a 20 inch stack of wet newspapers and placed a one-quarter inch thick section of dry heavy catalog paper in front of the stack (see Figure 1). The wet newspaper would represent the flesh and blood of an animal and the dry catalog paper its hide. While I recognize that this is a contrived test, it would at least allow me to understand the expansion.
Figure 1: The bullet testing medium - a stack of wet newspapers. While not perfect, it does provide
a convenient means of comparing relative bullet performance.
Figure 2: L to R: 150 gr. Sierra at 2690 and 2150 fps; 150 gr. Combined Technology Partition at 2690 and 2150 fps; 150 gr. Winchester Power Point at 2690 and 2150 fps - all recovered from wet newspaper.Since I only had enough newspapers around the house to set up one bundle that I thought would be thick enough to contain the bullets, I needed to place the six shots that I would test (three different bullets at high velocity and the same three at low velocity) into the same bundle. In order to avoid overlapping the six bullets, I needed to precisely place my shots; therefore, I decided to fire all six at a distance of 25 yards.
Since the 300 yard terminal velocity of the 150 gr. bullet in the .300 Weatherby is nearly the same as the initial velocity of the .308 Winchester, I could use the same Reloder 15 powder charge that I used on antelope in my .308 to mimic the 300 yard velocity of the .300 Weatherby. At 25 yards, the external ballistics calculator indicated that this .308 load would be approximately 2690 fps; this, I figured, would be close enough to 2650 fps for the purposes of this test. To approximate the 300 yard terminal velocity of the 150 gr. bullet in the .308 Winchester, I turned to IMR SR 4759 powder. The IMR manual lists a load range with this propellant where one can achieve 2150 fps muzzle velocity for a 150 gr. bullet in .308 Winchester; this will yield a 25 yard velocity that is identical to that calculated for 300 yards.
The results confirmed my concerns about the Combined Technology bullets and dispelled any concerns that I had about either the Sierra Gamekings or the Winchester Power Points (see Figure 2).
In the case of the Combined Technology bullets, the bullet is too tough to properly expand at the 2100 fps. This fired bullet weighs 147.3 gr. As can be seen, the front section barely peels back, so it is much like shooting a solid. This explains the observation that I made on the two antelope shot at 250 and 300 yards. At the greater velocity, it does expand and does what Partitions do: the front core disappears leaving an expanded copper front and solid rear shank. This fired bullet expanded to 0.579" diameter for a 88% increase. It weighs 125.3 grains for 83% weight retention.
The Sierra bullets both mushroomed rather nicely. The lesser velocity test results found the Sierra to expand to 0.480" diameter for a 55% increase, while the greater velocity result shows the Gameking to expand to 0.711 diameter for a 131% increase. Weights were 131.5 and 123.3 grains respectively indicating 88% and 82% weight retention respectively. These bullets have long had a fine reputation. Based upon this performance, its my opinion that it is well deserved.
The most pleasant surprise in the test was the performance of the Winchester Power Points. Both lesser and greater velocity tests resulted in beautiful mushrooms. Bullet diameters were 0.617" at 2690 fps and 0.514" at 2100 fps, while weight retention was 76% and 86% respectively.
Figure 3: Bullets showing penetration obtained in wet newspaper. L to R: Winchester Power Pt- 2600fps; Winchester Power Pt-2150fps; Sierra-2600fps; Combined Tech. Partition-2600fps; Combined Tech. Partition- 2150fps; Sierra-2150fps.
Figure 3 presents the penetration results. Frankly, I take these with a grain of salt because it is unlikely that the compression of newspapers throughout the stack was perfectly even. I think that the compression was consistent enough in that the overall penetration results make sense: the less the bullet expansion, the greater the penetration. Other than that, it is difficult to say why the lesser velocity, but more expanded Sierra would penetrate more than the lesser velocity, solid-like Partition.
This test has caused me to rethink bullet selection. Based upon this data, for initial velocities under 2800 fps, standard bullets will be the rule. For .308 Winchester, I will use the 150 gr. Sierra Gamekings and for my .300 Savage, I will select the 150 gr. Winchester Power Points. The tests performed here show they work well from 25 yards to 300 yards. For my .300 Weatherby, I will continue to use premium bullets. The 2690 fps impact velocity results were such on the standard bullets that I would worry whether they could withstand a 3000 fps impact at 100 yards. And, since I know the Sirocco has worked well on antelope and the X-bullets have been fine on Rocky Mountain goat, whitetail and muledeer, I see no reason to change. Perhaps if I knew that my shots on game would be at a minimum of 300 yards, then I would consider using a standard bullet in a high velocity magnum round.
As for the Combined Technology bullets, it is my opinion that they are inferior to the old Partitions, at least where light skinned game is concerned. Since the front core is smaller, there’s less expansion when the front lead core is shed. Additionally, while the rear shank is steel reinforced (ostensibly to prevent the rear lead core from squirting out the bottom of the bullet upon impact), it works against any expansion of the rear shank. Perhaps they are best served for beasts on the order of bear or hog.
So, is it possible to have too much bullet? Yeah, it really is.
No comments:
Post a Comment