4 Factors that Affect Ammunition Performance

Gun Collecting Tips: Factors that Affect Ammunition Performance

The quality of the ammunition, moisture, altitude and temperature can affect performance.

A round that doesn’t go bang like it is supposed to can define heartbreak and disappointment for any operator, but it’s especially true for gun collectors. Operable firearms are the crux of many collections. And that starts with good ammunition performance.

Here are four factors that affect ammunition performance. (Tip: You’ll want to test these factors when you win Gun Digest‘s sweepstakes for a shooting range package.)

1) The quality of the ammunition in the first place. Whatever we start with, it must be in the best possible condition.

2) Moisture. It’s the big fish in the list of ammunition enemies. Any hunter could fill gun collectors in on this critical concept. Duck hunters can tell you of hunts gone to heck because he left his shells in a bucket stool overnight or allowed them to be splashed or sat on by a dripping retriever.

Rifle ammunition can be ruined just as quickly. Left in a hunting coat pocket after a foul-weather hunt, and then taken from a warm house into the frigid woods and then back again, these mistreated rounds can slurp up enough moisture in the form of condensation – even a tiny drop –to render them inert.

3) Altitude. This is something many gun collectors disregard when it comes to ammo performance. We all know that changes in atmospheric pressure can change external ballistics, but to what degree is the question. When I lived in Gloucester, Virginia, elevation 12 feet above sea level, and used ammunition for hunting, then took that ammunition to Buck Mountain, nearly 5,000 feet higher, the bullets did some amazing things on the target range.

Suddenly my groups were significantly higher above zero with some calibers and loads. At the higher elevation, the decreased pressure and thinner atmosphere acted to reduce drag and change the trajectory. I attempted to determine if there were any velocity changes by taking chronograph readings at sea level and at the higher elevation using 10-shot strings of four different calibers both at the muzzle and at 200 yards.

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What I found was that initial velocities were virtually the same but the 200-yard readings were statistically different, with the higher elevation numbers coming in faster than those shot at sea level. The larger caliber, heavier bullets seemed to suffer more than the lighter bullets of smaller diameter, but both (.35 Whelen, 250-grain Hornady and 6mm Remington 87-grain Hornady) showed percent velocity changes that could be measured. All tested ammunition retained more velocity at higher elevation than that which was measured at low elevation.

So, gun collectors at sea level or thereabouts who plan to shoot above 10,000 feet need to check their zeros when they get to their destinations.

4) Temperature. It’s common sense that ammunition is temperature-sensitive. Ammunition left to bake on the dashboard can reach temperatures approaching 120 degrees in a closed car or truck. Ammunition left in the car on a frigid night can assume air temperature. If that temperature is low enough it can surely cause changes to ignition and pressure.

Going back and forth between high and low temperature extremes will, as mentioned, cause condensation to occur within the cartridge case. Here you have to use your best judgment. If you store your ammo over long periods of time do your best to keep the temperature of storage constant.

And remember, gun collectors, if one round is bad, chances are others in that bunch are likewise affected. Be smart, care for your ammo and it will consistently get the job done.


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