Air Rifle Scope Shooting Low? Barrel Droop, Shims and Adjustable Mounts Explained

Before you spend a penny, rule out the other usual suspects. First, check the scope is optically centred: with the rifle secured, wind the elevation turret fully down, count the clicks to fully up, and return it to the middle — this is the scope's optical centre, and it is where the glass performs best and the reticle is most accurate. Diagnosing droop from a scope that was never centred to begin with will send you down the wrong path. Second, check parallax. Some scopes not designed for airgun use have a parallax fixed around 100 metres; at a typical 20–35 yard air rifle zero, that mismatch causes the point of impact to shift with head position in a way that can look exactly like elevation trouble. Third, confirm the front and rear rings were not swapped during fitting, and that both are torqued evenly — an over-tight or crooked ring can itself introduce a few MOA of apparent droop. Finally, chronograph the rifle. A rifle producing noticeably less than its rated power will drop faster than expected and can be mistaken for a mounting fault when the real issue is power.

If you have ruled all of that out and the scope is still maxed on elevation, shimming is the cheapest fix. A thin shim — classically cut from an aluminium drinks can — packed under the rear ring tilts the scope's optical axis down slightly to meet the barrel's actual line, using up far less of the scope's internal elevation travel to reach zero. It works, it costs nothing, and it is fully reversible, but it is fiddly to get even and it does nothing for windage if that is also off.

The tidier fix is a dedicated adjustable or tapered mount, several of which are made specifically for this job by UK manufacturers. Sportsmatch UK, for example, makes a compact one-piece mount (the OP15C) built with roughly 20 MOA of droop compensation aimed squarely at air rifles, priced at around £31, and also makes two-piece dovetail mounts with about 0.75 mm (0.03 in) of vertical taper for the same purpose from around £30 (prices correct as of September 2026). MTC and Venom offer comparable adjustable mounts in the UK market. A taper or adjustable mount corrects droop at the point of contact rather than deep inside the scope's own mechanism, which is the more robust long-term fix if you are not planning to sell the rifle on.

There is a real reason to prefer fixing this at the mount rather than simply living with the scope wound near its limit. A scope's erector assembly — the internal tube that actually moves the reticle — tracks most accurately and repeatably near its own optical centre. Running it close to the edge of its elevation travel for the life of the rifle increases the risk of tracking errors between shots and, on a hard-recoiling spring-piston rifle in particular, raises the risk of the reticle mechanism shifting or even striking the housing under the reverse-recoil impulse springers are known for. A correctly droop-compensated mount lets the scope sit near its optical centre at your actual zero distance, which is where it was designed to perform best.

One thing a droop fix will not do is extend your rifle's effective range. Whatever mount or shim gets you back to a proper zero, a sub-12 ft-lb air rifle remains a 35–45 yard humane-kill tool on rabbit, grey squirrel and similar quarry; an FAC-rated rifle extends that envelope but is still not a substitute for a centrefire at genuine long range. Buy the mount that solves the droop, not the magnification or turret range you do not need at those distances.