Scaling factor, .22 vs airgun (.177)


Book Reviewer
Please can anybody out there come up with a scaling factor that will relate to, say, a 1/2" group with a .22 (sub-calibre Lee Enfield) on an indoor range to what could be expected at half the distance in still air with a .177 airgun?

Qn because when neighbours & wife are out I set up a target at 35' in the garden to pot away with my brother's airgun which he has left with me. Not having fired anything since about 1968 I would like be able to compare what I'm achieving now with what I used to be capable of.
Half the distance, half the group size.

The rifle matters of course, but that is on a rifle-by-rifle basis, not calibre. Some .177 airguns will group so closely from a rest at that range that the shots will overlap. Others will not.
Exactly - at that range, unless the weapon is truly crap then group sizes should be in direct proportion.

Assuming your indoor range was 25m, then a 1" group is roughly 1mm per 1m, so 1/2" is 0.5 mm/m.

If your range is 33' then that's 10m, so you should be looking for a 10mm (2/5", roughly 6/16") group to be as good as you used to be.
1/4" groups are more than possible with an airgun even outdoors.

Did a lot of airgun hunting and target shooting over the years including HFT

The thing with airguns is getting the right pellets as every barrel (including barrels of the same model) like a different diet and even different batches of the same pellet can cause major deviations.

The other thing is setting the scope up correctly for the range your shooting at. At airgun ranges, parallax is absolutely critical. even the slightest touch out of position with your sighting can send a shot well out of the group.

I used to run the BSA owners group and have a lot of experience with airgunning. If you need any pointers, dont hesitate to drop me a PM


Book Reviewer
Thank you chaps, I had supposed an airgun would have a lower muzzle velocity than a .22 firearm, and that's why I asked about scaling, not just re the geometry. On the ground, the anwswer is that I need a lot more practice!
The air rifle will have a significantly lower velocity (thus the pellet will drop much more in flight than a .22 bullet) but should always drop by the same amount, so shouldn't affect the group size.

Clearly at longer ranges, a smaller, slower bullet will be far more affected by environmental factors (primarily wind) than a bigger faster one - but at 10m the effect should be negligible.
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