PH-5A is in error by 17% for its range settings? |
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britrifles
Senior Member Joined: February 03 2018 Location: Atlanta, GA Status: Offline Points: 6539 |
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Posted: March 27 2018 at 9:24am |
This OP six months old, but got me thinking. I'll dig up my copy of the PH Service Rifle score book, it discusses the PH 5 sights fitted to the No. 1 and No. 4 rifles. The PH 5c sight with the 1/4 MOA knobs fitted does not give 1/4 MOA clicks on a No. 4 rifle, it's off by about 1/5 if I remember right (4 clicks = approx. 1.25 inches at 100 Yds). I'm going by memory here, but I'll confirm. It becomes evident if you use the MOA elevation settings for the various ranges published in the PH scorebook for the PH 5 sight, these settings are lower in MOA than actual. I figured this out when I plugged the data for my loads into Strelok ballistic program and compared them to the MOA range table in the PH SR Scorebook. The range scale on the PH 5c sight seemed pretty close, even with my hand loads (174 gr SMK at MV of 2400 fps) going from 200 to 300 to 600 yds. One of these days I'll try it with MK VIIz ammunition. Is the sight radius different on a No. 1 vs No. 4 rifle with a PH 5 sight installed? I think the Elevation vs Range tables were different for these rifles with the PH 5 sight. I also checked the Mk I machined Singer rear sight on the No. 4; 1 MOA clicks; approx. 0.0075 in/click. |
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Shamu
Admin Group Logo Designer / Donating Member Joined: April 25 2007 Location: MD, USA. Status: Offline Points: 17603 |
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Yes, I usually run 150 Gr at about 2550 FPS, so its more a curiosity than anything.
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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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Zed
Special Member Donating Member Joined: May 01 2012 Location: France Status: Offline Points: 5585 |
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It would also be for original ammo so probably irrelevant for your reloads anyway!
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It's nice to be important, but it's more important to be nice!
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Shamu
Admin Group Logo Designer / Donating Member Joined: April 25 2007 Location: MD, USA. Status: Offline Points: 17603 |
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Suddenly, out of the blue there's this Revelation that no-one ever heard of before!
Hmmmm? |
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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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Canuck
Special Member Donating Member Joined: January 17 2012 Location: Agassiz BC Status: Offline Points: 3535 |
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I read the exact same article a couple days ago.
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Castles made of sand slip into the sea.....eventually
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evanguy
Senior Member Joined: May 08 2015 Location: N.S. Canada Status: Offline Points: 355 |
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Ohh ok so it is one of the 1/2 moa units not the PH minutes sight, so that ideas out.
I have the exact same sight as you, now i want to check if its the same with mine. |
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Shamu
Admin Group Logo Designer / Donating Member Joined: April 25 2007 Location: MD, USA. Status: Offline Points: 17603 |
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News to me but I just read that any PH-5 fitted to an SMLE is 1/6ths off for distance. Supposedly the reason is they were calibrated for a Long Lee so there's a velocity difference & a sight radius difference that combined mean you need to use 6 clicks to get the effect of 5 on the range scale.
Any observations or thoughts? Its an early 5A with the 1/2 MOA clicks BTW. |
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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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