"What Happened to Me" by Josh3rd (long post)

September 26 2017 at 11:02 AM

Hector Medina  (Login HectorMedina)


Sorry for the late reply, but with two little ones and a ton of stuff going on, plus the fact that there was info all over the place, I had to take a little while to mull all things over.

So, let's start with the gun:

Pro Sports are elegant guns that CAN perform very well at their intended power level: 12 ft-lbs.
The architecture of the gun (side rails where the mechanisms are mounted mounting then onto the stock) makes for VERY peculiar stresses and shifts. This is not unique to the ProSport, it also happens to SMLE's (all Mk's). There are ways to bed these guns, but it is not the way factories do it.
So, my first piece of advice (that you have already gotten) is drop down the power to 12 ft-lbs. MAX 13. No more. There are several ways to do it, PERSONALLY I do NOT go for "skinny" (sleeved) pistons simply because they require equally skinny springs, and since internal stresses in the spring steel go with the CUBE of the OD, it makes little sense increasing the internal stresses of the springs when they are already pretty close to their limit.
A short stroke piston with a maxed out (OD) spring in a custom guide would be the way I would prefer to do it.
Make sure the stock is well finished INSIDE AND OUT. And test, under different environmental conditions, how the gun performs.

Now, the scope:
Hawke scopes are not too reliable. You need to work on it to learn its idiosyncrasies. Theoretically, your scope's reticle should be "true" at 10X (or so the website says), but I have found in actual scopes that that is not ALWAYS, EXACTLY the case.
So, set up a mil-confidence target (anything that is marked in inches) at 27 yards 2 feet and 4 inches and make sure you verify that your mils are true miliradians.
IF you are not interested in using the metric system, then check that at 12X you are getting IPHF (Inch per Hundred Feet) between mil-dots.
While you are at it, you should also measure what is your true Click Value (set the scope at a point in the ruler or other marked object you are using) and dial in 40 clicks, then see where the CH's are at. Note it, and now you can divide the whole distance by 40 to know the average value of each click (not too useful for AAFTAHFT, but useful for sighting in with the least number of shots).
IF you can, do these tests at different SCOPE temperatures (you will need two strip thermometers: a beer brewing one and a reptarium one glued to the main tube of the scope, just make sure that you have space to use the rings), you will gain much information.

Now the pellet:
EACH barrel will prefer one specific pellet. WHY? all the industry is working on that and has been for the last 25 years without any real answer. It is just a fact.
It is also a fact that the final SHAPE of the pellet is given by a combination of the powerplant pressure delivery and the rifling (including the choke). Since the shape defines the drag (real, not theoretical) and the drag is SIMULATED in the ballistic software using a scale factor we call Ballistic Coefficient, the BC is dependent on the tune, the barrel and the batch of the pellet (each batch may use a SLIGHTLY different metallurgy and/or dies and therefore the final shape will depend on how much the pellet gets deformed, or not, when shot), your trajectory WILL change as the pressure delivered to the skirt by the powerplant changes (DO NOTE I am saying Powerplant, so this applies to PCP's also).
H&N's are consistent pellets, BUT as much as I like the H&N guys (we've worked closely on a few projects), nobody's "purfect". And even if all the factors in the pellet are the same, changing venues (altitude, temperature, humidity) WILL change the pressure curve delivered by your powerplant to the pellet.
Last, but not least is the fact that precession, nutation and yaw are the most detrimental to a good BC. A lighter pellet that flies true will have a substantially higher BC than a heavy pellet that wobbles.
SOMETIMES, you can establish if your pellets wobble by setting up a powerful/laser flashlight under the gun at sunset and watching how the pellet flies to the target by watching the reflection on the skirt.
A high speed camera affixed to the scope can also help, but not everyone has one.

Now the shooter:
If you changed your attire, most probably, your POI will change. A jacket, even a thin one makes a difference when it is on or when it is off.
Gloves change the POI.
If you use a baseball cap, it might change your POI if the visor touches the scope while the gun is recoiling.
If your level of hydration changes, the eye, that is almost 98% water, will change, and with this the focus and the acuity.
Sitting differently will change your POI, how you rest your gun in the sticks can also change POI.
You need to test AND shoot in EXACTLY the same configuration.
You also need to test elevated (inclined) and downhill (declined) shots. The angle of the barrel will change your POI.

Now, IF EVERYTHING ABOVE is constant/known, now you can deal with the environment.
Wind is the pellet's Nemesis. Pellets are (like all flange-stabilized projectiles), extremely sensitive to air flows.
Wind from the front will make you hit low. Wind from the rear will "float" your pellets along and yield a higher POI.
Wind from the left will not only make your pellet drift to the right, it will also make it climb a little.
HOW MUCH these effects change YOUR POI is something for you to determine.
Ranging from the shadow to the light will change your ranging
Ranging in bright light will give you different results as ranging with an overcast sky.
IMHE, putting all the marks on the scope in one day is impossible to do accurately. You are better off putting in pencil marks and then checking along the week at different times to see how PRECISE (true to true value), your ranging is.
Same goes for the trajectory. Do it and then check it again and again under different conditions.

I'm sure I am forgetting a few things, LOL!

Springers are peculiar beasties.
And yet, they are most satisfying.

Take your time, enjoy the trip.



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On line trajectory calc by Brad Troyer MILDOTS


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