Theoben Sirocco gas-ram rifles

With break barrels undoubtedly still the most popular type of air-rifle available, an abundance of models exist to cater for the demand. But whilst manufacturers jostle for position, and a slice of the cake where sales are concerned, many offerings are fairly crude, aimed purely at the entry level shooter.Representing something of a top end product where break-barrels are concerned, Theoben’s position in the market place has never been in question; and with their highly innovative gas-ram concept, they offer a serious alternative to those who favour this style of rifle.

What we have here is the latest spec of their own break-barrel design, that sees that much vaunted replacement power plant pushed to it’s limit. If you‘ve never encountered these rifles, then let me bring you up to speed, for it was Theoben that originated the design, having now been copied or adopted by various other manufacturers with varying degrees of success. Inspiration for the gas-ram design apparently came from the pneumatically dampened forks on a motorbike, which led to this Cambridgeshire based company patenting their ground breaking work back in 1982.

Internal Workings

By replacing the steel mainspring in the compression cylinder, with a sealed chamber full of air (originally gas), the characteristics of the rifle could be altered, and a more maintenance free rifle developed. Basically, as the barrel is broken and the rifle is cocked in the conventional manner, the air (permanently contained) behind the piston, is compressed. Once the rifle is fired, this contained air expands - powering the piston, which in turn, compresses the free air in front of it, thus propelling the pellet in the normal way.This literally all happens in milliseconds, and the result is a super-fast lock time - the time taken from pulling the trigger, to the pellet exiting the barrel - in theory aiding accuracy. As one of the first customers to snap up a custom stocked version of the Sirocco (the original version of this rifle) way back in the early eighties – sporting a mouth watering piece of English Walnut, I still understandably harbour something of a soft spot for the brand. This latest spec model takes the concept to new levels though, and whilst my original timber, with its quite exceptional figuring, is rarely equalled, there’s no doubting the subtle improvements in configuration, handling and overall performance, now on offer.

Thumb Up or Thumb Through

Picking up the Evolution is an instant reminder as to just how far Theoben have come with these rifles, with the level of sophistication and standard of finish, aimed fairly and squarely at the discerning shooter.

The walnut thumbhole sporter stock includes a well defined and pronounced cheek piece, bringing the eye perfectly in line for scope use, and includes the roll-over style with a right hand bias. An ambidextrous beech stock may still be available, however, which would bring added versatility and flexibility if necessary.The thumbhole allows for a ‘thumb through’ grip, but you can also go the ‘thumb up’ route as the Evolution stock has a thumb shelf.  In my book a thumb shelf makes such a difference, and this stock is perfectly shaped in this regard, with a generous central groove scalloped out on the reverse of the pistol grip. This allows for the classic ‘thumb up’ hand position, which can really make a difference where trigger control is concerned. Laser-cut chequering covers both the grip and that tastefully angular and stylish fore-end, improving both handling and aesthetic appeal.

With all the woodwork (manufactured by Custom Stock in Sheffield incidentally), treated to a pleasant matt oil finish, nicely enhancing the grain in the process, the overall appearance and finish is excellent.

Bigger Barrel and a Choice of Moderator

With Theoben rightly renowned for their high quality chemical bluing, in addition to their engineering prowess, it comes as no surprise that the overall impression of my test rifle is highly favourable. ‘Top class’ best describes the externals then, but of course these gas-ram models keep their technical advantage discreetly hidden on the inside. For the record, the test rifle came fitted with a 16inch barrel in place of the usual 10.5inch tube, and the factory will be supplying these as a standard fitting from now on. My rifle also came fitted with an Evolution silencer, although the Vortex model is available on request.

Theoben have really developed their range of rifles over the past few years, and several options exist where the Evolution is concerned; such as an ultra carbine model with an extremely short barrel. Whilst I appreciate there’s a market for this stuff, I wouldn’t personally recommend it, since for sheer handling, this full length barrelled Thumbhole spec. is clearly the way to go.Original Theobens were fitted with integral scope mounts, which could prove somewhat inflexible, being set in their position on the rifle’s receiver. Trying to fit an unusually long scope for example, could highlight the problem, so Theoben have abandoned this approach, and now offer conventional, machined dovetails. With over eight inches of rail available, these rifles should now accommodate most scopes comfortably.

Lock-Up

Not having shot one of these gas-ram Theobens for a while, I was itching to get started on the test range, and experience once again, the unique firing characteristics of these technical masterpieces. Solid engineering, is as stated, a feature of the brand, and the breech design is a classic example. The barrel lock-up on the Evolution is simply superb, with a chunky adjustable twin bolt arrangement and sprung détente.

Cocking the rifle just requires a firm jolt to release the barrel, and this in itself requires much less effort than many rivals. The actual cocking stroke is fairly easy, once a continuous sweeping motion is adopted. The stroke is incredibly smooth, being completely devoid of any internal noise. With no spring to spoil the experience, all twang and ‘graunchiness‘ normally associated with manually cocked rifles is removed. ‘HE’ on the spec sheet, stands for High Efficiency, and that nicely sums up these latest gas-ram models. The cleverly designed system incorporates a modified dummy inertia piston (which helps to counteract piston bounce at the end of the stroke), and Zephyr grooves which are now cut into the cylinder wall, as opposed to the piston head. These grooves supposedly help channel air through the transfer port at the end of the stroke, to again, minimize bounce. All this is in a bid to eliminate felt recoil at the end of the day.

Whilst the manufacturer claims ‘almost no recoil‘, I couldn’t go that far, yet the firing cycle is fairly unique. An extremely quick snap, sums up the experience, which feels both slick and efficient, although movement is still felt at the shoulder, requiring all-important follow-through and technique.

Range Time

In the aim, the stock feels spot-on, and as a sporter design, is extremely supportive. Just having the choice of ‘thumb up’ or ‘thumb through’ grip, gives real versatility, and this Evolution gives a good account of itself as a result. The two stage trigger is pretty good, although that first stage is still a tad over sprung and just a little heavy overall.  Reducing this could only help the overall release, and improve performance still further. That said, it breaks cleanly and is wholly predictable. An automatic safety catch is situated just in front of the blade, and can be easily nudged off with the front of the trigger finger, prior to taking the shot. It should also be noted that these rifles can be de-cocked, whereby the action is opened and the barrel is gripped firmly with one hand whilst the trigger is pulled and – under control of the hand - the barrel is slowly allowed to return to its un-cocked position.

Over 30yds, using Air Arms Diabolo Field pellets, this .22 calibre Evolution tore superb 1/4inch clusters on a regular basis, and half inch groups at 40yds were easy to come by. I shot the rifle from the over-arm, sitting FT stance, and in short, when care is taken, it’s an extremely accurate piece of kit.Chronograph testing revealed good consistency too, with the same pellets producing a highly impressive 14fps variation over a 10-shot string. For the record, this kind of gas-ram rifle is classed as ‘recoiling’ for the purposes of competition use - namely Hunter Field Target, but as stated, the firing cycle is wholly different and indeed superior to that of most comparable conventional spring powered models.

At around the £530-£550 mark, including silencer, these rifles now represent fair value for money, occupying as they do, a fairly unique position in the market place. Admittedly there are several rifles out there which are easily as accurate as this model from Theoben, yet what they don’t all share is the sheer class that oozes from this level of build quality and finish. Add to that the laser fast snap of the action, and maintenance free design, and the immense appeal of these intriguing rifles begins to make sense.

Technical Specification:

•Model: Evolution Thumbhole
•Manufacturer: Theoben Engineering Ltd
•Country of Origin:UK
•Type:Gas-ram break barrel
•Calibre: .22 on test/.177 also available
•Weight: 7.6lbs unscoped
•Overall length:44inches
•Barrel Length: 16inches
•Stock: ThumbholeWalnut sporter
•Trigger:2-stage adjustable
•Average Velocity: 552fps using Air Arms Diabolo Field pellets
•Average Spread:14fps
•Average Energy:10.8ft/lbs
•RRP:Thumbhole stock with Evolution silencer £534; Thumbhole stock with Vortex silencer £550.25
•Contact:Theoben Engineering Tel 01353 777861