S&B 12-50 MkII vs. Kahles 10-50 FT vs. March 10-60 HM for BR/FT
- Thread starter dgeesaman
- Start date
I have the Kahles and Delta
Hector claims the Delta I gave him to play with shifted the wrong direction....
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At the next big event, they may have a big walk-in freezer, that they ask you to sit in with your gun for 5 minutes, when you emerge from the freezer, into 90-degree atmosphere, there will be a bench set up, and you will have 2 minutes to engage 3 targets with 1 shot each. Not a likely scenario.
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Thermal shift is irrelevant to benchrest, except if you're shooting indoors with a cold gun and it throws your POA mid-card. Outdoor benchrest, as I understand it, involves frequent sighters and a shift would be absorbed pretty quickly. In field target a different thermal shift is important - some scopes shift parallax settings significantly at a particular temperature.
Thermal shift of parallax causes inaccurate ranging. Brian van Liew described it well for Philip recently. That’s easy to test since you start with a cold scope and simply check your parallax against a known yardage as the scope warms up and monitor temperature. You can move the rifle and scope all you want as long as the distance is maintained. That confirms how much it shifts and at what temperature.
The other thermal shift, POA, is harder to pin down, but it could be done with a rigid mount on an indoor range. The only challenge with that is fixturing it on a stable base and making sure the scope is tested from cold to above room temperature. Our club's indoor pistol range has a hard mount at 20y that can be used for ammo testing and would work for this too. I suspect a ‘hot’ lamp would be fair and effective to get it above room temperature. Not planning to test at the moment but its not imaginary we've seen it shooting a cold BR gun indoors and seeing the POA shift suddenly and stay there.
Thermal shift of parallax causes inaccurate ranging. Brian van Liew described it well for Philip recently. That’s easy to test since you start with a cold scope and simply check your parallax against a known yardage as the scope warms up and monitor temperature. You can move the rifle and scope all you want as long as the distance is maintained. That confirms how much it shifts and at what temperature.
The other thermal shift, POA, is harder to pin down, but it could be done with a rigid mount on an indoor range. The only challenge with that is fixturing it on a stable base and making sure the scope is tested from cold to above room temperature. Our club's indoor pistol range has a hard mount at 20y that can be used for ammo testing and would work for this too. I suspect a ‘hot’ lamp would be fair and effective to get it above room temperature. Not planning to test at the moment but its not imaginary we've seen it shooting a cold BR gun indoors and seeing the POA shift suddenly and stay there.
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I'd be very interested in knowing how much one moves on your indoor range/fixture @ 20 yards? If you do the test I hope you'll report your observations here.
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Ben...The thermal shift has to do with the ability of a scope used for FT to range find consistently . It's a real thing and can cause big problems for the shooter if it's not accounted for. There is no point in arguing that it doesn't exist...it's settled science that can be observed by anyone that uses a scope as a rangefinding device in field target. The typical March scopes that people use for FT range short when they get hot and most others range long.
Mike
Mike
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Messing around with mid-range scopes we’ve seen 1/8”-1/4” at 20y. Range is 70f and rifles coming from a cold vehicle maybe 20f. Over the course of the first hour the POI moves around a bit. Its not necessary in my mind to dig too deeply, except to ensure you don’t show up for a match with a cold rig and start shooting cards for score.
Field target is more involved, one solution is having two pointers for your parallax wheel and a thermometer on the scope body. This works when a scope has a temp where things shift and are stable above and below this temp. Even though that seems like an answer it can be difficult when the temps are passing through the shift temperature.
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On a gun, on a one-piece rest. Of course we're shooting one shot per dot so aim is changing for each shot. The shift appears as a sudden and permanent POI change. When you're indoor without air movement, you shoot 20 shots that scatter around the bullseye and then the next three shots in a row miss in the same direction, you clean the barrel and they still keep going there, it's pretty clear the scope has shifted and it's time to re-zero. It's not really a test result as much as a repeated observation. My experience with this is a Leupold 6.5-20 EFR. My friend was using either a Weaver or Leupold benchrest scope I think.
To actually test for it I'd put the very cold gun firmly in a one-piece rest, aim it on a small bullseye, and set that on the floor or very solid table, out of the way where nobody can touch it. Then check POA as it warms up to room temp, possibly warming it more than that with a hot air gun or heat lamps. With heat of course you have to be careful that the heat is distributing evenly around the scope and it's shifting from uneven temperature in the scope tube itself.
An ideal result would be the scope has zero POA shift across a suitably large range of temperatures.
David
To actually test for it I'd put the very cold gun firmly in a one-piece rest, aim it on a small bullseye, and set that on the floor or very solid table, out of the way where nobody can touch it. Then check POA as it warms up to room temp, possibly warming it more than that with a hot air gun or heat lamps. With heat of course you have to be careful that the heat is distributing evenly around the scope and it's shifting from uneven temperature in the scope tube itself.
An ideal result would be the scope has zero POA shift across a suitably large range of temperatures.
David
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Never said it didnt exist. Dont come on here with your authoritarian air and get in the way of me learning a thing or two.
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Topics pretty well derailed by my silly questions anyhow, my apologies to the op. Glad ya found a nice scope for your rifle. Ill quit askin questions.
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Do I see you on Accurate Shooter? You might want to look at the new Sightron geared for FT. Look it up, plus a good discount for veterans. This will be my third year for a pair of the SVED 10x50x60. Great tracking and brightest scopes I have looked thru.
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I have, it will be out mid-summer and there is a pre-order list if you're interested. I am on accurateshooter also.
I wanted to get this project moving along a lot faster and I came across a fair and convenient deal on the S&B so that's why I went the way I did. Plus I got to peep the actual scope in difficult conditions before agreeing to buy it, so that helped. Unless I encounter issues with this scope or my other Sightron FT scope lets me down, I'll probably let someone else be the first to try the new Sightron model. But the specs do look ideal.
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I have used all high end scopes for decades, Between those 3 brands I prefer the Schmidt bender how ever , I only ran the PM2 series I dont think the scope you mentioned is in same tier of glass , I know the 5x45 model is very pricy from $5700 to $6950 for a tremor 3 or 5 in FFP . but I have shot ELR many times out beyond 2000 yards and I never shot my 5x45 beyond say 25x , I know hunting long range it is extremely difficult to find a target with higher magnification ,
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Have you considered
IOR Precision XT 10-60x56 40
I’ve compared it to my March and I can not tell the difference…Upvote 0
How does it do for rangefinding in field target situations?
I've heard very good things about the Valdadas but never in a field target setting. Since this scope needs to do both, I leaned toward scopes with some field target background.
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