How do you determine an accurate shot count for your gun?

:hoot:

Obtaining a correct shot count, per fill, is a complex, difficult, and hard to repeat event. There are many variables…more than you might think.

Let’s take a look:

1) Air pressure in the gun’s air cylinder must be exactly the same when starting a shot count session. This can be difficult to determine with any degree of exactness using only the pcp air gauge.

2) A pcp air gauge is NOT a precision instrument! It is mechanically driven, the numbers and bar markings are tiny, the needle is quite thick by comparison, and it is extremely difficult to judge when to stop your count if going by visual inspection of the needle’s position.

3) Start time from a full air cylinder fill must be exactly the same when starting a comparison shot count session. Why? Because air gets hot when compressed into a pcp air cylinder, and that raises the psi. The higher the psi the higher the shot count. That same psi will slowly drop over the next 30 minutes to two hours, dependent on the ambient air temperature surrounding the gun. As little as 30 minutes in an air conditioned room, or one to two hours outside, can impact shot count totals.

4) End time for each shot count session is equally as important. If you take 30 seconds between shots in one shot count session, and one to two minutes between shots in the next shot count session, your final shot count total may if when shooting from a fresh fill. (see “3” above)

5) If one shot count session is taken indoors and compared against a second shot count session outdoors, your shot count total will likely vary. Again, air cylinder temperature is important.

6) You can sometimes fire one or more shots before the needle makes any noticeable movement.

The only way to obtain repeatable shot count results, from my experience and reading, is to duplicate the conditions as exactly as possible for each session. Even then you are best advised to undertake several shot count sessions, under identical conditions, and average the totals.

A hammer spring adjustment is really for fine tuning velocity, not for major changes.

A major change in pellet velocity usually requires a regulator adjustment. To be accurately undertaken, a regulator adjustment tool is required. (They can be purchased here on the forum. I believe Ernest has them.) Regulator adjustment without a gauge to show the precise drop off point is going to be an inaccurate and labor intensive undertaking. Not for the faint of heart, or for those who lack patience. Better to send the regulator off to an expert, or purchase the correct tool, then you can control your adjustment much more precisely. When it has been properly set, then the HST can be used to fine tune velocity for the pellet you choose to shoot.

Fortunately, most of us don’t require such exact measurements. However, if you want to adjust your HST, or regulator, setting, you might like to know if the adjustment was worth the effort in shot count, considering the gain, or loss, of pellet velocity. (Accuracy, per gun, per caliber, per fps, is another matter, best addressed in another topic)

Not everyone may agree with me, but there’s plenty of room to post your thoughts on this. It’s something everyone should have a working knowledge of in this sport.

Regards,

Uncle Hoot: