Why fit one
Hearing first: a centrefire rifle without a moderator is loud enough to damage hearing with a single shot, and ear defenders aren't always practical in the field. A good moderator takes the crack down to something your ears, your dog and your neighbours can live with, tames muzzle flip and recoil so you see your shot land, and is increasingly expected on stalking ground and at clubs.
One line on the law: you no longer need anything on your certificate to buy one, but you do still need a valid FAC to possess a moderator for a section 1 rifle (in Scotland, an Air Weapon Certificate for an air rifle moderator). The detail is in our guide to the law change.
Over-barrel or front mount
Every moderator adds length and weight at the muzzle. The two designs manage that differently:
- Over-barrel (reflex) moderators sleeve back over the barrel, so most of the body sits behind the muzzle. You get a big internal volume, and therefore strong sound reduction, while adding only a few inches to the rifle. The trade-off is a larger diameter around the barrel. This is the default choice for a stalking rifle.
- Front mount (muzzle forward) moderators hang entirely in front of the muzzle. Simpler, slimmer and easier to swap between rifles, and the right answer where an over-barrel won't fit: tapered or heavy barrels, barrel-mounted gas systems, or rifles with little free barrel to sleeve over.
Neither is "better". Over-barrel keeps the rifle compact for its performance; front mount fits everything and travels between rifles more easily.
Calibre, bore and threads
- Calibre rating. Buy a moderator rated for your cartridge, not just your bullet diameter: a .223 and a .22-250 share a bore but not a pressure level. The rating is printed in the maker's specification.
- One moderator, several rifles? Often yes: a moderator bored for 6.5 mm or .30 will serve smaller calibres too, at a small cost in performance. If the threads match, swapping takes seconds. The reverse is never true: don't put a bigger calibre through a smaller bore.
- Threads. Most UK rimfires are cut 1/2"x20 UNF; centrefires are commonly M14x1, M15x1 or M18x1. Check what your barrel is cut to before ordering, and if it isn't threaded at all, ask us about getting it done.
The Aimsport range
Aimsport moderators come to the UK through us, so stock, spares and straight answers come from the source. The Triton range covers every job:
- Rimfire II (£99). Compact front-mount for .17 and .22 rimfires. The one to put on every rimfire you own.
- Triton No.3i (£279.99). Compact front-mount for smaller centrefire calibres: light, slim and unobtrusive.
- Triton No.4i (£376.99). Lightweight over-barrel for the active hunter: excellent suppression without the muzzle weight.
- Triton No.5i (£403.99). The all-rounder: over-barrel balance of sound reduction, weight and length for stalking and sporting rifles. Also available as a front mount (£345.99) where an over-barrel won't fit.
- Triton No.6i (£431.99). The highest performance in the range, for shooters who want maximum suppression.
Shop Aimsport › All moderators ›
Not sure which fits your rifle and your shooting? Book a visit or send us the rifle details and we'll match one to it.
Care, and your zero
- Re-zero after fitting. A moderator almost always shifts your point of impact a little, and can change your muzzle velocity too. Zero with it fitted and leave it fitted, or expect two zeroes. Our muzzle velocity guide covers checking the numbers.
- Take it off after shooting. Firing fills a moderator with moisture. Left fitted in a slip, that moisture sits in the threads and the bore and corrodes both. Remove it, stand it muzzle-down to drain, and store it off the rifle.
- Rimfires run filthy. .22 ammunition is waxy and dirty; strip and clean a rimfire moderator regularly. Centrefire moderators need far less: keep the threads clean and lightly greased.
Common questions
Do I need anything on my certificate to buy a moderator?
No. Since 29 June 2026 moderators are no longer listed on certificates and need no slot or variation. You must still hold a valid FAC to possess one for a section 1 rifle. Our law guide has the full picture.
Can one moderator serve two rifles?
If the threads match and the moderator is rated and bored for the larger cartridge, yes. You give up a little performance on the smaller calibre and you'll want to confirm zero on each rifle.
Will a moderator change my zero?
Almost always a small shift, occasionally a useful improvement in group size. Re-zero with it fitted and be consistent about shooting with it on.
Over-barrel or front mount: which should I buy?
If your barrel profile allows it and the rifle lives with one moderator, over-barrel gives the best performance for the length. If you want one unit across several rifles, or your barrel won't take a sleeve, go front mount.
How long does a moderator last?
Looked after (drained, stored dry, threads greased), a quality moderator lasts many years of normal sporting use. Neglect and moisture are what kill them, not round count.
Last reviewed 7 November 2026. Spotted something out of date? Tell us and we'll fix it.