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PH-5A is in error by 17% for its range settings?

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britrifles View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote britrifles Quote  Post ReplyReply Direct Link To This Post Topic: PH-5A is in error by 17% for its range settings?
    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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: September 29 2017 at 2:21pm
Yes, I usually run 150 Gr at about 2550 FPS, so its more a curiosity than anything.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Zed Quote  Post ReplyReply Direct Link To This Post Posted: September 29 2017 at 11:12am
It would also be for original ammo so probably irrelevant for your reloads anyway!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: September 29 2017 at 6:16am
Suddenly, out of the blue there's this Revelation that no-one ever heard of before!
Hmmmm?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Canuck Quote  Post ReplyReply Direct Link To This Post Posted: September 28 2017 at 3:11pm
I read the exact same article a couple days ago.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote evanguy Quote  Post ReplyReply Direct Link To This Post Posted: September 28 2017 at 3:05pm
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: September 28 2017 at 1:44pm
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?
Confused
Its an early 5A with the 1/2 MOA clicks BTW.
Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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