• The AGN App is ready! Search "Airgun Nation" in your App store. To compliment this new tech we've assigned the "Threads" Feed & "Dark" Mode. To revert back click HERE.

Lets discuss Extreme Spread (ES)

So, I had plans to tear one of my .25's apart and make some changes for the sake of experimentation. Prior to teardown, I shot a number of pellets at 30, 50, 75, and 100 yards. This started as a simple plinking session and ended as a bit of an experiment in hunting accuracy.

We all shoot for uber small extreme spreads(ES) for our airguns both regulated and unregulated. I have always lived by nothing more than 4% for an unregged gun and 2% for regged. When I shoot groups at any range, I fill to a pressure and fire only a number of shots that fall into 1% max and less ES. I have always done it this way and for the sake of BR accuracy I will continue this practice. However, I am looking at hunting accuracy in this instance. Make no mistake we want the best possible accuracy for game, but what wins BR matches is much smaller groups than what is a minimum requirement for hunting game.

For no reason, I shot well past what I have always considered a useable ES. Not sure why, but I did. These last shots were in the 6-10% range. Oddly enough, as I repeated this exercise many times, the end results were basically the same. Yes, the 75 and 100 yard targets were much harder to hit as the ES climbed past 4%, but at 50 yards and under(my typical small game range I prefer to shoot)even an ES as high as 10% would have been kill shots on game as small as a squirrel. I was able to replicate these results out to 50 yards time and time again shooting to an ES of 10%. 10% was surely pushing the limits and I would not go that far, but found that 6-8% was more than acceptable and 10% will easily do the job at 25 yards and less. After finishing up the modifications to this particular .25, I once again returned to the thoughts of ES and what is really usable for hunting.

I haven't done any .22LR shooting in a very long time. Actually, I have shot my centerfires a few times over the past few years, but my rimfires have not been touched in atleast 3 years if not longer. So, my recollection of .22LR ES is not very good. Upon doing some research as a bit of a refresher, most .22LR including some of the known precision match ammo has extreme spreads much higher than what we feel is acceptable for our airguns. Most having ES's of 3-10%. This helped to make my results shooting to an ES as high as 10% make more sense as the 0-50 yard distances that I feel is my standard squirrel range is the same regardless of air or powder being used. I feel the much lower BC's of our pellets is a factor in what we deem to be acceptable for an extreme spread?

Thought this was rather interesting from a hunting perspective and am curious what others think?
 
Here are a few factors to think about.

One example I'm familiar with is the .22 caliber, 55 grain, Nosler Ballistic Tip varmint bullet—since I've shot well over 50,000 of them. The average weight spread from bullet to bullet is less than .1 grain! That is, one tenth of a grain! That is less than two hundredth of a percent! Compare that to any pellet, no matter the cost, size, or weight! As for the diameter, and assuming you have a really good caliper, the differential almost can't be measured!

With a decent scale, you can measure the powder charge to less than .1 grain. Assuming your using a 22-250, you know how to reload, size properly, and a few other variables, the FPS spread will be under 10 FPS out of about 3,600+ FPS. That's about three tenths of a percent. Compare that to the very best regulated PCP!

 
I've often wondered about the es in powderburners, but that's another story for another day. As far as airguns go, I've never had acces to a chronograph before the past year. Because of this I've always used however many shots are available before the pellet drops more than an inch at whatever range I'm shooting. Now that I have a chrony I'm pretty surprised to see what actually happens when you start messing with air pressure in the tube. I began filling my 2400 custom to 1800psi because I get very low velocities above that range. As the psi in the chamber drops the velocity increases until 1500psi, then it drops and I refill at 1300psi. I get about 25-30 useable shots now whereas I got 15-20 before. ES is greatly dependent on you knowing your guns well.
 
Great info AZ!! My .22LR data was collected from various tests using field grade rifles and the averages were between 3-10% with a very small amount including Eley, RWS, and Federal having an ES of 1-1.5% in some tests, and as high as 3% in others. The comparison was to illustrate that many of us who have or continue to use a .22LR for hunting with standard grade ammo are shooting to ES's that probably average around 5%. That is higher than what we deem to be a good ES for our unregulated PCP guns, However, almost any over the counter .22LR ammo and field grade gun is highly capable of "Minute of Squirrel" accuracy out to 50 yards with ease. Finding that a modern PCP rifle is also capable of "MOS" accuracy with an ES as high as 10% at short range really took me by suprise!!

I find no need to shoot to ES's as high as 10%, but found all this rather interesting non the less. Also keep in mind that the gun I used to "test" is a 70fpe .25cal shooting sized 43gr eunjin pellets. I will assume that the power level and high BC of this combination contributed to my results and a lower powered lower BC might not perform as well in a similar test?



 
This has been a great discussion. With the shortage of reliable source of efficient regular and target 22 LR I had not considered getting into Air Guns as a really accurate media to satisfy my needs. I had been a long range large caliber shooter most of my life building ammunition or having superior ammunition supplied to me by Uncle Sam. With the discussion here today, some of the best discussion I have read of late by the way, I realized that digging into our repeatable data and logging that data builds a shooter that knows his rifle (pistol) and it's capabilities or weakness to an ultra high level.
Kudos to each of you on this discussion of extreme spread and ballistic coefficients. It makes me realize that I am not alone in this Psychosis.