The problem is airgun related, we pretty much use the rifle as a mortar bomb compared to a C/F. To achieve this excessive elevation it's better to "pack" the rear mounts than over extend the scope
Packing can be simply a couple of pieces of film or an adjustable mount. The latter is better but I do the former as I have a lot of rifles and BSq are exy
Registered User
My Chairgun and I reckon pellet drop at 55yds is going to be around 12" with a full power .177"Originally Posted by Gary C
Like centrefire at 200 yards?
About 1/2 a degree of downslope required on the scope?
B.S.A. Airsporter Mark 4 .22" , Webley Osprey .22", Feinwerkbau 300 S .177", Webley Senior .177"
Sign here: http://petitions.pm.gov.uk/TargetPistols/
Registered User
Yep about that.
Working in metric 'cos numbers are rounder that's 300mm give or take.
High mounted scope 50mm above bore, so vertical displacement sight line to target = 350mm
50m range so horizontal displacement = 50,000 mm
Let angle be x
tan(x)=350/50000
x = atan(0.007) = 0.4 deg (24 MOA)
“We are too much accustomed to attribute to a single cause that which is the product of several, and the majority of our controversies come from that.” - Marcus Aurelius
Captain Mainwaring
Continuing what is becoming an extremely fascinating thread.....
What CF is this?
I have this at - 43.6 inches at 200 yards if -12" at 55yds?
That's quite a lot. CF rails are available for -20MOA for long range shooting, in the expectation you can't dial in enough adjustment on your scope.
No wonder we had as many problems as we did with the higher mag scopes.
Well, problems with scopes not being able to do the (seemingly) impossible?
...
To be good, one must do good.
Registered User
- what I meant to ask was:
"Is the amount of elevation adjustment on a 12 ft/lb .177" air rifle at 55 yards about the same as a centre-fire rifle at 200 yards?"
Chairgun tells me that pellet drop (relative to bore) at 55 yards is about 12" (lots of variables).
If I remember right (which is doubtful), the old .303" bullets used to drop about 12 - 13" by 200yards, and I presumed .308" was roughly the same. As I haven't fired a centre-fire rifle for two decades, I could be talking complete prematurely senile b*ll*cks, though
B.S.A. Airsporter Mark 4 .22" , Webley Osprey .22", Feinwerkbau 300 S .177", Webley Senior .177"
Sign here: http://petitions.pm.gov.uk/TargetPistols/
Captain Mainwaring
- what I meant to ask was:
"Is the amount of elevation adjustment on a 12 ft/lb .177" air rifle at 55 yards about the same as a centre-fire rifle at 200 yards?"
Chairgun tells me that pellet drop (relative to bore) at 55 yards is about 12" (lots of variables).
If I remember right (which is doubtful), the old .303" bullets used to drop about 12 - 13" by 200yards, and I presumed .308" was roughly the same. As I haven't fired a centre-fire rifle for two decades, I could be talking complete prematurely senile b*ll*cks, though
You is definitely a Londoner, or doing a good impression of one.
.303 and (less so) .308 use quite heavy bullets, both travel fairly slowly in the great scheme of things. If you are really interested I'll go dig out some figures, but a .224 bullet out of moderm CF rifle or 6mm/.243 out of one, will be travelling a bit quicker than the stuff you are used to, and the drop would be measured in 'one hand of fingers' type measurements.
The -20 MOA Picatinny rails I mentioned earlier, might be found on .308 rifles shooting 1000 yards.
...
To be good, one must do good.
Registered User
Hmm, my information is pretty out of date then. I was just trying to get a rough comparison. What you say about modern high velocity CF re-inforces Gary C's point that airguns are mortars by comparison.a .224 bullet out of moderm CF rifle or 6mm/.243 out of one, will be travelling a bit quicker than the stuff you are used to, and the drop would be measured in 'one hand of fingers' type measurements.
I have to remind myself that Pellet/bullet drop is only half the story . .
Seems to me that whether the scope rails need to be inclined depends not only on the pellet/bullet drop at the zero point, but also how far away that zero point is.
The nearer the zero point, the more sharply downward the scope needs to be angled.
Extreme case: 12" drop zeroed at 50 yards is like 20 *FEET* drop at 1000 yards!
Comparing to the old .308", the airgun would have to be dropping only 2" at 50 yards to have the same scope angle as the .308" zeroed at 300 yards. In practice a legal airgun will be dropping 2" by 25 yards, I reckon.
So, if you zero your FT airgun at 55 yards, a fairer comparison is a .308" at 600+ yards or probably somewhat more (the ballistics of the supersonic bullet will be far better than an airgun pellet), or perhaps a more modern CF at 1000+ yards, as you say?
(corrections welcome!)
B.S.A. Airsporter Mark 4 .22" , Webley Osprey .22", Feinwerkbau 300 S .177", Webley Senior .177"
Sign here: http://petitions.pm.gov.uk/TargetPistols/
Is this what you were looking for?
If so, then a .177 air rifle, zeroed at 35 yards is going to need about 18 clicks for 50 yards and a .303 on a 100 yard zero will need 10 clicks at 200 yards.
Any modern centerfire is obviously going to need far less.
Kev.
Registered User
Interesting Kev. What ballistics software did you use?
B.S.A. Airsporter Mark 4 .22" , Webley Osprey .22", Feinwerkbau 300 S .177", Webley Senior .177"
Sign here: http://petitions.pm.gov.uk/TargetPistols/
Captain Mainwaring
Ah, The Cavalry has arrived!!
Nice one Kevin. Demonstrates Gary's remark "we pretty much use the rifle as a mortar bomb compared to a C/F" rather well.
...
To be good, one must do good.
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