One of the things that determines Quality ammunition from questionable ammunition is its ability to propel a bullet to a specific velocity time and time again. This consistency becomes more and more important the further the target is, as even seemingly small differences in velocity can have impacts on shot placement at distance. Another consideration is how accurate is the box information compared to actual results. Some companies are better at this then others.
Recently we sighted in our Pawn Shop 30-06 using Discontinued Remington Hog Hammer ammunition loaded with 168gr TSX bullets. While this is factory nickel plated ammunition, I believe Remington would consider this more of a mid tier ammunition rather then their top quality ammunition. During the site in we gathered the velocity data for all of the shots fired using my Lab Radar. This is my personal favorite Chronograph.
Before we dig into the Chronograph data let’s take a look at the published ballistics for the round.
Velocity Results
When using the SD Card Lab Radar will store the results of each shot onto an SD card. This includes velocity data from your 5 specified ranges out to about 100 yards. I typically use 10, 25, 50, 75, 100 yards, and the Lab Radar automatically saves the muzzle velocity.
During our site in we fired a total of 25 shots. Which is a sufficient amount to apply some basic statistics to the data.
Already we have a bit of a red flag, the published data says we should be getting 2790fps out of a 24in barrel. However we are getting 2861fps out of a 22in barrel. I checked the brass, and there were no obvious signs of an overpressured load, so either Remington isn’t concerned with loading their ammunition to a consistent velocity (Loading to a target pressure rather than a target velocity can causes lot to lot variation in velocity without loading above SAAMI MAP) or maybe the bore on my rifle is tighter/looser then the SAAMI Test barrel they used and it’s producing a higher velocity.
Remington will likely blame it on my rifle, and I’ll likely blame it on Remington so we’re not going to gain anything here other than to say this is why it’s important not to trust the information printed on the back of the box when setting up your own ballistic tables.
In a previous write up we discussed the potential impact of a 20fps Extreme Spread. The extreme spread here is 107fps. Using Ballistic Explorer we can see the potential impact of this difference.
Is 1.7in at 300 yards difference caused by a high or low velocity going to determine a miss or a hit on a deer? It could but it is unlikely. Will it determine who takes home silver or gold? Yep, it will. Again it all comes down to how you will be using the ammunition as to how consistent the velocity needs to be. What we can be certain of is that the differences in velocity likely did not add to the group size during our accuracy testing of the Pawn Shop 30-06.
If I was to take this analysis one step further, I would label my shots on target to correspond to the shots on the chronograph. That way I could conclusively determine if the velocity was playing a role in the overall group size.
Other Considerations
There are other considerations here that can adversely affect group size beyond just velocity. Velocity doesn’t come for free, it is directly dependent on the pressure the cartridge generates. Higher velocity is the product of higher pressure, and visa versa. So if the velocity is 107fps different, then what does that tell be about the pressure? Well it’s likely not very consistent either. Inconsistent pressure can impact accuracy. So even if velocity is not adding to or taking away from our group size a 100 yards, the inconsistencies caused by pressure variation, can.
All barrels act like a tuning fork when a cartridge is fired. They vibrate at a set frequency, and if we could hear that frequency we would observe that higher and lower pressures cause the amplitude of these vibrations to increase. While the frequency remains the same, we would perceive it as being louder or quieter. These vibrations causes the tip of the barrel to swing side to side and up to down. The bullet exits from the barrel in the middle of this vibration, if the barrel vibrates at a lower amplitude one shot, and then at a higher amplitude on a subsequent shot the bullet release will be affected and this will show up on the target.
Thin barrels, such as those used in rifles where weight is a concern, will vibrate more than thicker barrels used in target rifles. Longer barrels will also vibrate more, then shorter barrels. This is why short barrel rifles and pistols can often be more accurate then their longer thinner profile counterparts. Seeing large variation in velocity is symptomatic of large variations in pressure. Which means the barrel is not vibrating at the same amplitude every shot (Remember the frequency is unchanged, it is the amplitude that changes).
While we look at the velocity component and how it affects group size, we do not have an easy way to look at the pressure component and how it affects barrel harmonics. We can only say that it is highly likely that the load is not developing a consistent pressure as evident by the swings in velocity, and that this likely increasing group size.
The Wrap Up
I’ve just written about 1,000 words complete with charts showing how other parts of the load can affect the accuracy and by looking at the velocity we can have some idea of the overall quality of the ammunition. However I have previously stated that when doing a baseline accuracy test I am only concerned about choosing ammunition loaded with a quality bullet. So if all these other things matter why am I not using handloads, or top tier ammunition, why only focus on the bullet for the initial evaluation?
in short, you have to start somewhere. Poorly constructed bullets can cause accuracy issues that are readily distinguishable at 100 yards. So by eliminating one known variable, bullet quality, we can begin to hone in on some of the other issues. As we see with the chart, the differences in bullet velocity at 100 yards would have made a 1/8in difference on bullet impact. I am not a good enough shot, even with a rest, to be concerned with that difference. Harmonic vibrations are an unknown quantity, most of my shooting has been done in 1.25in test barrels which are not as susceptible to vibrations. How much this impacts over all group size is unknown. I would rather spend my money on controlling the variables I know make an impact, rather then variables that make little to no impact, or an unknown impact.
With that said, I would not give this ammunition high marks for the velocity variation alone. Coupled with the discrepancy in the box velocity versus actual measured velocity also bugs me quite a bit. It is using a premium bullet that I trust, so that’s it’s only plus right now.
Does it serve its purpose as a “Hog Killing Ammunition?”. Yes, though I would expect that the ammunition would limit the range that I could reliably hit a 5in vital zone shot to no more than 300 yards. (1.5MOA rifle is capable of a 4.5in group at 300 yards. The velocity extremes could add 1.7in to the group size at 300 yards. Bringing the best expected group size to 6.2in which is 1.2in over the 5in vital zone, but will probably still produce a clean kill)