Gun Test: Webley Mastiff

If a rifle seems too long, but a bullpup seems too butt-heavy, Mike Morton offers you a third option with the semi-bullpup Webley Mastiff

you’ll probably want to tinker with fill pressures to find the optimum for your particular rifle

Maker: Webley & Scott (
UK Distributor: Highland Outdoors (
Model: Mastiff 12
Price: £529.99
Type: Pre-charged pneumatic
Calibre: .177 and .22 (on test)
Action: Sidelever
Magazine: Multi-shot; 14 shots in .177 and 12 in .22
Overall Length: 33” (84.2cm)
Weight: 8.7lbs (3.95kg)
Stock: Ambidextrous walnut thumbhole
Sights: Scope only, Picatinny rail
Length of Pull: 39cm (15 1/2”)
Trigger: Two-stage, adjustable
Trigger-pull: 1lb 7oz
Safety: Manual, resettable
Muzzle Energy: 10.9ft-lb

The Mastiff wears an elegant and wonderfully smooth walnut stock, but its totally matt finish will benefit from an application of oil

While bullpups have their fair share of devotees, who appreciate their rifle-length barrels and pug-sized proportions, some shooters aren’t so keen. Then again, not everyone enjoys hauling around a long rifle, meaning there’s a potential gap to be filled by semi-bullpups such as the Webley Mastiff.

Bullpups usually have little or no butt pad, tend to be butt-heavy and can also have a tendency to be top-heavy. While a semi-bullpup shares the same loading and trigger configuration, with the breech located behind the trigger blade, semis do away with most of the other drawbacks of a pedigree pup. In other words rifles such as the Mastiff deliver a rifle-length barrel in a carbine package, potentially offering the best of both worlds.

On the range where there are little or no obstructions, a full-length rifle can be splendid to shoot; but take a rifle into the field, where you’ll have to navigate obstacles such as bushes, branches and hides, and you’ll appreciate just how much easier it can be to walk, stalk and shoot with a shorter airgun.

Webley’s Mastiff 12, to give it its full name, is a sidelever-operated multi-shot. It’s a well-equipped package, being supplied with two magazines, a single-shot tray, fill probe and O-ring kit, as well as being factory-fitted with sling studs and swivels. It’s available in .177 and .22, the latter seen here on test, with each magazine offering 14 shots and 12 shots respectively.

The magazine is loaded right to left, and engages positively by lining up the guide rail with the slot that’s been machined into the action

This gun shares the design features of the company’s Raider 12 model, this time housed in a semi-bullpup stock. It’s that sculpted walnut stock you’ll notice first. While beauty is a subjective thing, the Mastiff has to have one of the prettiest stocks ever seen on a semi-bullpup – or even a thoroughbred pup for that matter. It’s a real Airgun Crufts head-turner.

The butt pad is adjustable, and better yet can be slid up or down without the need for any tools, just by pushing in the release catch. This is a nice feature because not only is it easy to adjust when you’re setting up your rifle/scope combo for the first time, it can also be adjusted in the field, such as when taking prone shots when the butt may need to be lowered. Adjustability is also a feature of the cheekpiece, although this time you’ll need a hex key to loosen it first.

Its sweeping lines help keep the weight down, and the woodwork immediately under the integrated trigger guard lets you easily adopt the target hold, with the palm of your leading hand supporting the rifle and your elbow tucked into your waist. That type of stable hold can be hard to adopt with a typical hunting rifle.

No stippling or chequering has been applied to the pistol grip, which does have a reasonable amount of palm swell on both sides, and there’s only a shallow groove to get hold of each side of the forend – but there’s an elegant strip of stippling immediately underneath the forend that features the Webley logo.

No chequering or stippling has been applied to the pistol grip, but plenty of palmswell ensures a good hold

Sling swivel studs and the swivels themselves come pre-fitted, taking away the headache that can accompany the act of drilling into a virgin stock. The swivels can’t be removed from the stud, but if you want to fit quick-detachable ones you can unscrew the combined Webley unit and fit a new QD stud and swivel.

Moving onto the gun itself, the metalwork, including the shrouded barrel, is workmanlike, and has a satin black finish. The sidelever rattles a bit when it’s open, but functions efficiently and is silent when closed. The safety catch is sensibly placed underneath the lever and well away from the trigger.

Trigger adjustments must be made with the rifle removed from its stock. The gun is held in place with a 5mm hex bolt sunk into the pistol grip, but this can be tricky to access and unscrew, so take care not to strip the head.

Three things strike you immediately when you pick up the Mastiff: its width, weight and balance. The stock is extremely slender, which accentuates its good looks and keeps the weight down, but may feel a little too narrow for larger shooters.

One friend remarked how the stock felt as much like a sword as a rifle! Others who handled the test rifle found the edges of the trigger guard to be quite sharp, although when you’re actually shooting the gun you don’t really notice this. If it really bothers you, you could always take the sharpness out of the edge with the careful use of some wet and dry paper.

The trigger blade can be adjusted for height and angle, to better position it to the pad of your finger, by slackening off the 2mm Allen screw

Talking of care and maintenance, this walnut stock features a beautiful matt finish. It has been oiled – you can definitely smell it – but not nearly enough has been applied, and it would be easy to mark the stock with mud, blood, sweat or water if it’s been raining cats and dogs.

A few coats of gun stock oil would really help protect this woodwork before its first foray outdoors. Alternatively, Napier Stock Shield would be a good choice as this product is much easier to apply and quicker to dry than conventional stock oils.

It’s a fairly solid rifle, living up to its doggy namesake by coming in at a hefty 3.95kg (8.7lbs), but luckily this Mastiff scores points for its neutral point of balance. I fitted a fairly large scope to the gun and the balance point was immediately underneath the trigger guard.

This makes the Mastiff feel far lighter than it really is, and although I didn’t take advantage of fitting a sling to the swivels, the rifle still wasn’t too tiring to carry around in the field.

A Picatinny rail that runs a full 20cm is used to mount your scope of choice, and that choice is made easier by the fact that the magazine, like many other rifles of this type, sits behind and below the rail, where it doesn’t interfere with scope placement. I did run out of elevation adjustment with my scope, however, eventually finding a solution with a set of Sportsmatch adjustable Picatinny mounts (ATP72).

The fill probe port is protected by a rotating dust cover that’s very smooth to operate

The manometer is located under the muzzle just forward of a rotating collar that reveals the filling port when twisted. It’s smooth to operate, and using the included probe, the gun can then be filled to a maximum pressure of 200 bar, delivering around 100 shots per fill on the test rifle.

It’s unregulated, and you’ll probably want to tinker with fill pressures to find the optimum for your particular rifle. I chronographed the Mastiff with 180 bar in the air cylinder, and it delivered some impressive results using Air Arms Diabolo Field pellets: a steady 10.9ft-lb with a variation of seven feet per second over a 10-shot string.

The two supplied magazines are made of a black polymer shell, an internal indexing wheel – with each chamber numbered for the particular shot – and a clear faceplate. The faceplate features a cut-out immediately identifying the chamber you’re currently on, so you know how many shots you have remaining.

To load the mag you need to turn the faceplate clockwise against a spring as far as it will go; a direction arrow is moulded on the faceplate in case you forget. Pushing in the first pellet takes up the spring tension, after which you can insert the remaining pellets by turning the faceplate anti-clockwise.

The magazine looks like it should be loaded into the action from the left, but actually can only be inserted from the right. It features a moulded ridge that slots home positively into a corresponding groove that’s been machined into the breech block. The single-shot tray, which is also made of a polymer, uses the same ridge and groove system to handily ensure positive alignment.

magazine design
The Mastiff’s clear-faced magazine needs to be rotated under spring tension and held open before the first pellet can be inserted

One thing I really like is the fact that the sidelever can’t be fully closed on an empty magazine, and this feature really comes into play when you’ve fired your last shot. It’s a physical indicator that you’re out of ammo – so there’ll be no dead man’s click and no wasted air.

The trigger blade can be adjusted for height, and can also be angled up and down, although there’s no provision to angle the blade to the side. Nevertheless, on a rifle costing just under £530, any adjustment at all is welcome.

The blade itself is made of a polymer, and the blade on the test rifle had a prominent seam running down the middle, which was a little uncomfortable for my trigger finger. If the test gun was mine, I’d break out more of that wet and dry paper and spend a couple of minutes sanding the surface perfectly smooth.

Trigger-pull out of the box was just right at 1lb 7oz. The trigger is a two-stage unit, but the test rifle arrived with the trigger adjusted such that all the first-stage travel had been taken up.

I decided not to tweak the trigger, just shooting the rifle as it came. The trigger can be the Achilles’ heel of mechanical bullpups and semis, usually being activated by a linkage, but the trigger here was pleasingly crisp, especially for a gun of this price.

The barrel is shrouded, and was reasonably effective at quietening the rifle. My test rifle was brand new, and actually got quieter the more I shot it, a welcome phenomenon usually associated with rimfire moderators.

The length of the Picatinny rail is a generous 20cm, giving you plenty of room to fit pretty much any scope of your choosing

While the Mastiff functioned well, the sidelever being located in a very convenient place for my shooting hand, I never quite managed to find the perfect pellet.

Despite extensive shooting with six different types of both JSB and H&N-manufactured pellets, I struggled to group shots inside a circle the size of a 2p piece at 30 yards. But because the rifle was so consistent over the chrono, I’m sure accuracy could be vastly improved upon once the right pellet is found.

Verdict? 76/100

Look & Feel: 7
Stock: 8
Build Quality: 7
Sights: 7
Cocking: 7
Loading: 8
Trigger: 8
Handling: 9
Accuracy: 7
Value: 8

“The Mastiff is a solid semi that’s full of features. Pick the perfect pellet and you could well end up with a sweet-shooting little rifle”

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