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How to use a mortar gun

Updated: October 2026

The usual failure is a tube that will not extrude. Water comes out behind the plunger, the nozzle spits, or a dry slug sits halfway down the barrel. On a hand pointing gun that almost always means the sand, the plasticiser or the seal, and sometimes all three. This sequence is for a ratchet gun you already own or are about to fill, on modern cement joints and patio gaps. The mix sheet for the gun in your hand wins if it disagrees with a video. Which gun to buy is on the [mortar syringe comparison](/hub/painting-supplies/mortar-syringe) and the [mortar pointing gun buying guide](/hub/painting-supplies/mortar-syringe/sub/mortar-syringe-buying-guide). Products Compared used maker sheets and review themes, and did not film a test wall.

The usual failure is a tube that will not extrude. Water comes out behind the plunger, the nozzle spits, or a dry slug sits halfway down the barrel.

Our top picks

Roughneck Roughneck ROU32150 Ultimate mortar gun

Best overall

Roughneck Roughneck ROU32150 Ultimate mortar gun
8.8/10about £28.57
View offer
Faithfull Faithfull FAIPOINTING pointing gun kit

Alternative

Faithfull Faithfull FAIPOINTING pointing gun kit
6.4/10about £23.25
View offer
Hilka Hilka 66855006 mortar and grouting gun

Preis-Tipp

Hilka Hilka 66855006 mortar and grouting gun
6.2/10about £14.99
View offer
On this page
  1. 1.Before any mortar goes in the tube
  2. 2.The mix the gun can move
  3. 3.Fill, place and finish
  4. 4.When it blocks
  5. 5.Stop and get a bricklayer

Before any mortar goes in the tube

Rake only the joint that has failed. HSE says uncontrolled chasing and raking can peak around 5 mg/m³ of respirable crystalline silica, against a workplace exposure limit of 0.1 mg/m³ over eight hours. For people at work, HSE names class M or H extraction and a respirator. Dampen the open joint. Fit a nozzle that enters the gap. Faithfull’s sheet marks the grout nozzle at 4, 6 and 8 mm and says mortar belongs in it only when it is cut to the largest mark. If light shows around the plunger, mix will pass it. Wet cement is about pH 12–13 and can burn skin trapped in a glove or boot.

The mix the gun can move

Use soft or silver sand, sieved, with a mortar plasticiser, mixed smooth. Faithfull’s instructions say no gravel and no coarse sand, and a 4–5 minute paddle. Refina describes a pumpable mix as about the consistency of yoghurt. Sharp sand is the common reason a plunger squeezes water backwards. Follow the sheet for the tool you are holding. Faithfull puts plasticiser in the water. Point Master, a different gun, puts plasticiser into the mix. Copying both, or using washing-up liquid, is how a batch turns slick and weak. If a test squeeze separates, stop. Another jug of water makes it worse.
Roughneck Roughneck ROU32150 Ultimate mortar gun

Testsieger

Roughneck Roughneck ROU32150 Ultimate mortar gun
8.8/10about £28.57
View offer

Fill, place and finish

Fill the tube part way. A full barrel is heavy, and the first blockage wastes the whole charge. LABC’s warning applies: overfilling stains the face, so take the excess off as you go. Keep the nozzle moving on a patio. The gun delivers mortar. It does not strike the profile. Tool the joint with an iron or a stick once the bead is firm enough to shape and still soft enough to compact. Wash the barrel, the plunger and the nozzles as soon as filling stops, including a pause for lunch. Faithfull says clean immediately. If you are still deciding whether to buy a gun, mortar gun or pointing trowel is that argument.

When it blocks

Water at the back of the plunger, with a dry mass in the tube, is separation. Refina and the Faithfull sheet trace that to coarse or sharp sand. A lump in the nozzle is the other fault: take the tip off and clear it. Forcing the trigger drives water backwards and packs the slug tighter. A seal you cannot tighten is different from coarse sand. Hilka reviews describe a plastic plunger that snaps, arrives broken, or never meets the tube. Fit the spare. Wash through while the residue is soft. A gun left blocked overnight is often scrap, or a ruined downpipe on the Faithfull.

Stop and get a bricklayer

Stop when the wall is cracked or bulging over a window or door, when the work is off a ladder you are unhappy on, or when you cannot tell lime mortar from cement. A cement sheet such as Faithfull’s 5:1 example is the wrong recipe to copy onto soft brick. Ty Mawr’s lime mixes are aimed at auger machines. If you buy a gun through the main comparison, a qualifying purchase can earn us a commission at no extra cost to you.

Common questions

What mix should I put in a mortar gun?
Soft or silver sand, sieved, with a mortar plasticiser, mixed to a smooth yoghurt-like ribbon. Faithfull’s sheet says no gravel or coarse sand, a 4–5 minute paddle, and gives 5 sand to 1 cement with an optional half part of hydrated lime as its example. Refina says a mix you have to trowel from the bucket is too stiff for a pump. Sharp sand is what squeezes water out at the plunger.
Where does the plasticiser go?
Follow the sheet for the gun in your hand. Faithfull says plasticiser goes in the water. Point Master, a different tool, says plasticiser goes into the mix. Using both methods at once, or using washing-up liquid, is a guess. Roughneck reviews call a proper plasticiser essential. If the test bead separates, change the sand or the dose on that sheet, and leave the water jug alone.
Why does water come out of the back?
The plunger is pushing on a mix that cannot pass the nozzle, so water takes the path behind the seal. Coarse sand, a full tube of stiff mortar, or a washer that is loose will do it. Tighten a washer that has an adjuster, as Faithfull reviewers describe, and sieve the next batch. If the plunger is smaller than the tube, as Hilka reviews report, water will pass until you fit a seal that meets the wall of the barrel.
How do I clear a blocked nozzle?
Take the nozzle off and pick or flush the lump out while the mortar is soft. Check the tube for a dry slug, because a clear tip on a separated mix will block again on the next squeeze. Then wash the gun. Forcing the ratchet is how the water is driven backwards. A nozzle left packed overnight often means a new tip, or a new barrel on a gun that uses downpipe.
When should I stop and call a bricklayer?
Call one for cracks or bulging over openings, for height you cannot work safely, for bead or tuck joints, and when you cannot tell lime from cement. A listed building, or any pre-1919 wall where the mortar might be lime, needs the mix specified before a cement gun recipe is copied across. A modern patio you can reach, with a mix that extrudes cleanly, is the job these steps are for.

Related pages

Lime mortar and a pointing gun

Mortar syringe

Best mortar gun on amazon.co.uk in this six-gun set

Mortar pointing gun: what to check before you buy one

Mortar gun vs trowel: deep gaps or a short brick run

Sources

Public UK sources on silica, cement, maker instructions and listed-building consent. Shelf prices, stars and review counts are the amazon.co.uk lines in the six listings dated 15 October 2026. Prices move.

  1. HSE, Chasing concrete and raking mortar (retrieved 16 October 2026)
  2. HSE, Cement (retrieved 16 October 2026)
  3. Faithfull, FAIPOINTING instructions (retrieved 16 October 2026)
  4. Faithfull, Pointing gun kit (retrieved 16 October 2026)
  5. Roughneck, Ultimate mortar gun (retrieved 16 October 2026)
  6. Refina, Mortar pointing mixes (retrieved 16 October 2026)
  7. Ty Mawr Lime, Can I use a mortar gun? (retrieved 16 October 2026)
  8. Historic England, Listed building consent, HEAG304 (retrieved 16 October 2026)