GTA
Target Shooting Matches, Discussion & Events => Field Target Gates => Topic started by: TwiceHorn on November 13, 2017, 10:25:00 PM
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So, Saturday I shot a match, did alright.
But, at the sighting range, before the match, I noted that every range was shooting about a "half dot" low. This was consternating because I had shot the day before and the short ranges were about 0.2 dot low from my range card.
So, I sucked it up and just added 0.5 dot to my card, mentally, and shot well over 50%, which is pretty good for me.
I talked to some buddies before the match started and they thought I should have cranked a half a mil into my scope. But, I am cautious about making actual scope changes based on a relatively small set of data.
Anyway, thoughts on what I should have done?
Also, the range card was done in July, when it was hot as fire here (well over 80, more like 100). It was about low or mid 50s at the sight-in range.
Also, I do most of my shooting indoors and during the hot months, the indoor temperature is 77 plus, whereas the week before the match, it was cool and the indoor temp was mid to high 60s.
Also, as temps crawled into the 60s and the gun/scope heated itself up, I started missing close in targets.
Those temperature differences probably account for the drop and I think it is probably my scope rather than my rifle.
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Not that unusual. It can be the scope, the gun, or both. More common for a piston gun.
It's possible to chart it and deal with it during the match. For the 2012 Nationals, I had a temperature strip on my rifle and a chart to adjust my holdoff/holdover. It's a little unnerving to trust a temperature gauge to determine where to hold but it can work. I still have the compensation data that I had at the time. though have since changed the tune and mounts:
50deg -.7x, -.7y
60deg -.4x, -.4y
70deg -.2x, -.2y
80deg 0 0 - my zero
90-110deg goes real wonky
I prefer not to put up with that anymore. I have since learned how to minimize the issues via tuning of my piston guns, proper mount setup, and thermal management.
That said, I have a PCP pistol that I can let bake in the sun till it's almost too hot to pick up. And it still maintains it's zero. My piston guns normally take a couple clicks depending on the weather and venue. Elevation changes of >2000ft are also a problem.
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Mark,
It sounds like your shooting a spring gun ...
Well as many realize they change by the day with Elevation, Temperature, Humidity and just there mechanical nature.
* If you have a well established "DOPE" for said gun and upon shooting at a new location find it OFF .. tho consistent in a tangible value across differing ranges .... REZERO to your baseline POI at your zero range & then go short, intermediate short, PBR then modest far and then far TAKING NOTES on what POI is doing based upon your known dope data.
Generally this can be done inside 30 or so shots during practice. TRUST YOUR DOPE !!! making minor corrections at specific ranges based upon whast learned during practice.
As an FYI ... this past week shot the AAFTA nationals with an altered scope setting from where it had been the last 6+ months unchanged !!!
Spent 2 days on the practice range ( Likely tho less than 2 hours in total ) chasing WHY FOR my PBR was 8 clicks too high !!
In the end after much mental distress RESET my scope zero at my PBR ( * Point blank range ) and then went threw the above procedure coming to the resolve my Dope data was good with the zero adjustment made and just shot my numbers confidently.
As one who ONLY breaks out my springer ( TX-200 ) for practice and shooting of a single match ( West Coast Piston Championship ) I FEEL FOR YOU and the frustration associated with shooting a piston gun full time :(
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Thanks, gents. Appreciate your input.
And yes, it is a springer, HW97K.
What is the general theory to setting up a scope and rifle to avoid temperature variation? With the scope, I assume it is avoiding any residual stresses in the mounting.
I had this theory that as temperatures creeped back to the 60s, as they did toward the end of the match, I would probably return to what my (modified the day before) card said. But the targets were so chewed up by then, I couldn't tell where I was hitting and unfortunately didn't have time to return to the sighting range to check my theory.
Also, somewhat fascinating that my little observations seem to gibe almost exactly with your temperature compensation chart, Scott H.
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Thanks, gents. Appreciate your input.
And yes, it is a springer, HW97K.
What is the general theory to setting up a scope and rifle to avoid temperature variation? With the scope, I assume it is avoiding any residual stresses in the mounting.
I had this theory that as temperatures creeped back to the 60s, as they did toward the end of the match, I would probably return to what my (modified the day before) card said. But the targets were so chewed up by then, I couldn't tell where I was hitting and unfortunately didn't have time to return to the sighting range to check my theory.
Also, somewhat fascinating that my little observations seem to gibe almost exactly with your temperature compensation chart, Scott H.
Post a good picture of your gun/scope/mount, and we can critique that aspect.
In general - for a piston gun, use a one piece aluminum mount if possible, or for multi-piece mounts, decouple the front or rear from the scope. Preferably, the rear. On a PCP, always the rear.
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All good suggestions. Here's my take. If you are shooting low or high consistency then it's likely the gun. If you are missing high or low consistently it's likely the scope(ranging errors). Unfortunately with a spring gun it takes time learning both systems to be able to adjust accordingly and time is what it takes to get these things worked out.
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I'll try to get a picture up in a bit. The reason I said I suspected my scope is that my rifle has been "gone over," degreased, krytoxed, ends polished by an experienced and good 97 shooter. So it would seem that a lot of the variables there have been eliminated. It is shooting a stock seal, for better or worse, but it seems to fit quite well. It has about 2500 rounds through it.
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Revisiting this. Had a match last weekend started in the mid/low 40s and crept up to the 50s. I observed what I believed to be 0.8 to 1 dot low at the range and had previously observed 0.5 dot low at 50s. I commenced shooting at about 1 dot over usual and did within expectations. My intention was to raise that to 0.5 after ambient temp reached 50 (half hour or so after). Things kind of went to the dogs at that point so I dunno.
Pix coming.
(https://i.imgur.com/vk2adnN.jpg)
(https://i.imgur.com/D6N1zCv.jpg)
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Well, for better or worse, I have ordered the Tac Vector 10-40. I can't complain too much about the UTG 8-32 as it ranges pretty well right out to 40. I am putting a larger wheel on the Tac Vector than the 100mm UTG.
I have the opportunity to change mounts as well. What single-piece mounts do you fellows recommend?
On decoupling, I have seen reference to orings on the ring screws and a thin layer of rtv silicone in the ring. The change in poi during a match has caused me some problems lately.