Geometric puzzlement

[sarf]

What CF is this?

- 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

[Baldie]

- 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.

[sarf]

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.

Hmm, my information is pretty out of date then.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.

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!)

[Beer Hunter]

"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

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.

[sarf]

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.

Interesting Kev. What ballistics software did you use?

[Beer Hunter]

Interesting Kev. What ballistics software did you use?

The values came from Sierra Infinity.

Kev.

[Baldie]

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.

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.