Many people seem to judge the effectiveness of a springer tune by how smoothly the rifle cocks, the amount of force needed to cock it, and the lack of spring noise that accompanies the shot. In fact, it is incredibly easy to achieve any or all of those qualities, but whether they are achieved at the expense of a reduction in accuracy is often overlooked. The other quality that is sought in a tuned rifle is a ‘nice’ shot cycle, but that’s a rather personal matter, with some preferring a quick action, others something more sedate. To make matters worse, our subjective perception of the nature of the shot cycle, and what the rifle is actually doing, is not necessarily the same thing, and I’m convinced that we tend to be susceptible to forming an opinion based more in line with our expectation than fact.
The recoil takes place in around one hundredth of a second, and most rifles’ recoil displacement is in the region of 6mm to 9mm. A fast action might reduce the time duration of the recoil by a thousandth of a second, and I am far from convinced that I could distinguish between nine and ten milliseconds. Short stroking or piston lightening might reduce the displacement by 1mm or so, and when people think the rifle’s shot cycle is quick, or the recoil reduced, it seems probable that they are sensing, if anything, recoil acceleration, and that their impression could well be reinforced by their expectations.
The only aspect of a springer’s performance that can be measured easily and objectively is the muzzle velocity and from that, the energy is easily calculated. Muzzle velocity and energy are important aspects of a springer’s performance, but must play a secondary role to accuracy, because ‘power’ counts for nothing if the pellet misses the target. Testing the accuracy of a springer is of an order more difficult than testing the power, because the shooter will hugely affect the accuracy, by the batch of pellets, and by the conditions in which the testing is carried out. The first point to recognize is that there are two types of accuracy.
ACCURACY
I accuracy-tested many springers in the 1980s, and discovered that the rifle most accurate when shot with extreme care from a padded bench was not the same rifle that gave the best accuracy out in the field. I realized that the bench result was a measure of the rifle’s inherent accuracy, and what we might call the ‘field’ accuracy was a combination of the inherent accuracy, plus the ease with which accuracy could be achieved away from the bench. The field accuracy of a springer is greatly affected by its movement during the shot cycle, the recoil and surge, which is something that very few people have ever managed, or perhaps even bothered, to measure objectively, but which almost everyone judges subjectively. Having accurately measured hundreds of recoil cycles, I know that my subjective judgment of recoil is practically worthless, and I suspect I’m far from alone in that.
To get a rounded view of a rifle’s accuracy, it is necessary to test both in normal shooting (off hand, kneeling or sitting and prone). To gauge the field accuracy, and from a bench to gauge the inherent accuracy, it is very important. What makes the inherent accuracy so important is that it is the potential accuracy, if it proves possible to tune the rifle to lessen the hold sensitivity and improve the field accuracy.
TESTING
Testing for field accuracy is easy; well, for me it is, because I can find the most accurate pellet shooting from the bench, then hand the rifle to an HFT springer shooter friend, and ask him to try it. Otherwise, you can try shooting at a variety of ranges, off hand, kneeling and prone. Unless the rifle is exceptionally tolerant of hold, it can take quite some time to make certain that it is the rifle causing any inaccuracy and not you having an off day.
You can usually save a lot of time and effort by testing for hold sensitivity from the bench. I do it by resting the rifle’s fore end on a soft pile of cushions, shooting a group, then repeating the exercise with my hand between the rifle and cushions, and again lightly gripping the fore end. This works because a large part of hold sensitivity is caused by the muzzle’s tendency to rise during the recoil, and anything that modifies the extent of the rise, such as gripping the fore end, will result in a large shift in pellet point of impact (POI). The comparative shift in POI between rifles is a good measure of their hold sensitivity.
The normal method of accuracy testing is to shoot groups, and the problem with groups is that the aim point grows with each shot. I combat that by sighting the scope so the pellet strikes high or low, leaving the aim point intact; if your scope has a multiple aim point reticle, you could alternatively use the ‘wrong’ aim point to the same effect. There is another problem with trying to shoot groups, and it’s psychological; the more shots you put into a nice tight group, the greater the pressure not to mess it up with the next shot, and the greater the chance that you will!
An alternative is to make a target with lots of small aim points, and take one shot at each.
LET’S GET MEASURING!
Because hold sensitivity is largely caused by the initial stage of the recoil cycle, it would be priceless to be able to measure recoil, before and after a tune. I have been doing precisely that for a few years and although the equipment I use is neither cheap nor easy to use, there is an alternative. It is not difficult to build yourself a simple apparatus to measure springer recoil, and the chances are that many will have most of the materials needed lying around, so the cost can be zero.
The idea is to build a cradle in which the rifle can slide freely, to sit the rifle upside down in it, and to hang a biro under the rifle to record recoil and surge. I made the cradle from a 27.75” length of 8.5” by 1.25” wood, cut into a base section 18” long, a rear upright 5.75” high, and a front upright of 4” high. The rear upright has a 2” deep recess, the front 0.5”, and I used Evo Stik to glue 1.5” wide strips of short pile carpet for the rifle to rest on and slide over. The two uprights are glued and screwed to the base.
The pen holder comprises a scope mount, a length of plastic rod the diameter of the scope body - I had a suitable length of PTFE lying around, although any plastic will do - with an 8mm hole drilled in, and a cut down old Bic biro pressed into the hole. In addition, you need a piece of thin card to record the trace on, best taped to the base so it cannot slide, and a length of thin wire and a windscreen washer hose to operate the trigger blade without touching the rifle.
In use, the loaded rifle is placed in the cradle with the pen touching the card, the trigger operated, and the pen draws a line showing recoil and surge, which you can measure using a vernier, preferably digital. After taking a shot, you will note that the pen’s final position is not at the end of the trace, and the distance between the two is the surge, which should also be apparent because the rear part of the trace will be wider and better pronounced.
The results that this simple apparatus records might not be quite as accurate as those I get using an accelerometer and velocity meter, but they are more than good enough to reveal whether a modification has increased recoil and/or surge travel, and to differentiate between the recoil and surge of a rifle using different pellets. They are a world more accurate than the verbal descriptions of recoil that most people use, and a few who reckon that a modification reduces recoil might be surprised to discover what the rifle is actually doing!
CONCLUSION
There’s nothing wrong in a tuned springer being smooth to cock, needing a low cocking effort, delivering good shot-to-shot velocity consistency, and having a quiet shot cycle; in fact, they’re all highly desirable traits, but as a measure of the worth of a tune, they must take second place to the real-world accuracy. It is possible, perhaps likely, that the greatest benefit of a springer tune comes when it instills the user with confidence in the rifle; if you think it is more accurate, it will usually be more accurate, and if that proves not to be the case, there is something seriously wrong with the tune.