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Theoben Evolution Vs. Theoben SLR98

Mark Camoccio tests the Theoben Evolution vs Theoben SLR98

Cambridgeshire based airgun wizards, Theoben, have seemingly gone from strength to strength in the last few years. They’ve come a long way since their humble beginnings, and their current product line-up rather reflects this; with several hi-tech and innovative pre-charged pneumatic designs sitting alongside the classics that made them famous in the first place. Those gas-ram models put them on the map, and my two rivals this month both originate from the Theoben stable.

Break barrel or lever

The SLR98 is a classic example of what Theoben are generally about; being a solidly made, beautifully finished rifle, aimed fairly and squarely at the hunting fraternity. Pitched against this is the Evolution – the very latest version of the gas-ram break barrel that started it all for them, back in the early ‘80’s. The SLR98, by contrast, is a fixed barrel design, but both rifles utilize the latest version of Theoben’s own H.E. gas-ram system. For the uninitiated, this means that when the rifle is cocked, the piston compresses a sealed chamber of air (Theoben previously used Nitrogen), effectively replacing a normal mainspring. ‘H.E’ stands for High Efficiency, and the clever design incorporates a small dummy inertia piston that moves back against the main piston direction in a whiplash effect that, in theory, helps to counteract the effect of recoil.

In the case of the SLR98, ‘SLR’ in the name is derived from ‘Self Loading Rifle’, due to the magazine facility, and ‘98’ from the year of the rifles introduction, although production eventually came to a halt; apparently the result of high manufacturing costs. With Theoben’s subsequent utilization of computerized CNC machinery, production costs took a tumble, and the SLR found its way back to the marketplace.

My test rifle came fitted with a rather snazzy thumbhole walnut stock, and even the ‘standard’ model (if you can call it that) comes with a smart and highly functional sporter configuration. Made by Custom Stock of Sheffield, the thumbhole woodwork is a masterpiece, with tasteful, yet entirely practical panels of chequering. Laser cut they may be, but the immaculate execution and crisp finish is faultless. From the sweeping curves on the flared forend, to the stylish panels neatly recessed into the finger groove/thumb shelf, the end result is a visual treat. But if you thought this stock was just about fancy looks, then think again. Theoben expect their clientele to take their products out into the field and muddy them up somewhat – so function is the key here.

The hand-filling grip of the extended forend affords a comfortable aim, whilst the ‘thumb up’ or thumb through’ options around the pistol grip illustrate further the well thought out design.

A prominent, crisply defined cheek-piece gives perfect eye/scope alignment, whilst an adjustable Wegu style butt pad is the icing on the cake.

The break-barrel Evolution comes equally well equipped in the timber department, with a stunning walnut sporter configuration, in keeping with the original Sirocco blueprint. A well defined, high cheek-piece, thumb shelf and chunky pistol-grip come together for great handling, whilst the most obvious difference from the ancestral line comes courtesy of those side flares shaped from the wood. Comparable laser-cut chequering covers the Evolution, and the end result is another stylish and supremely functional product.

Both rifles feature short carbine length barrels, and in the case of the SLR the 9.25inch barrel is finished off with a sleek little silencer ending in a blanking cap. This cap can be removed to allow for a larger silencer to be attached, which may improve the balance, yet hardly the looks, since it will interrupt what is a very sleek profile.

The under-lever is held in place via a sprung détente at the muzzle, and Theoben did toy with the concept of venting some of the spent air back down the hollow lever via a link, yet the idea seems to have been dropped; certainly on my test rifle.

Incidentally, according to Theoben, the length of barrel to be used on subsequent SLR’s will be increased by a few inches, to improve handling and performance in general; and I have to agree with them here, since I found the test model just a little light at the front. A longer barrel will reduce the cocking effort too, don’t forget.

The fluted design around the breech adds refinement and sets off some beautifully finished metalwork; as does the high quality, lustrous chemical blueing that covers the entire action- on both rifles I hasten to add. Theoben have had a reputation for top class finish for some while now, and these rifles illustrate just why.

Being a break-barrel, the Evolution’s profile is somewhat more uncluttered, and with an Evolution silencer in place, the test rifle certainly had a purposeful look about it. The jaws of the breech and the overall lock-up are reassuringly sound, whilst the actual cocking stroke is surprisingly manageable.

Cocking the gas-ram action is simple enough, but a deliberate technique pays dividends. A quick sweeping stroke gets the job done and is ultra smooth in the process. As previously mentioned, the longer barrel and under-lever of future SLR98 models will reduce the cocking effort still further, and aid stability on the target.

The characteristics of the gas-ram system gives the Evo and the SLR actions an amazingly fast lock-time; yet don’t be fooled. A fair old kick remains, all be it smooth and slick- feeling more of a snap (in the absence of any spring twang). Like any recoiling rifle, the movement can shake a telescopic sight to the point where it moves along the scope rails. So with this in mind, Theoben were including integral ring mounts with their gas-ram models, to be bolted onto their own dedicated raiser block. All very neat and precisely engineered. They still do with the SLR, but the Evolution now sports conventional dovetail rails.

With the SLR set-up, do bear in mind that because these mount positions are fixed, scopes of a particular dimension may foul the magazine as it rises from the action.

Action wise, the SLR98 comes fitted with a 7shot magazine – the ‘self loading’ part of the package, and, assuming a loaded magazine is in place, the firing cycle would be as follows: the under-lever is unclipped from the muzzle, then gripped firmly and pulled down and back until the trigger sear engages and the lever is effectively locked. At this stage, the magazine is automatically indexed, and the next pellet is chambered via a probe into the barrel, as the lever is returned to its closed position.

Seven shots are available as quickly as the lever can be pulled down and snapped back up again. The automatic safety catch is disengaged by pushing a tab forward (this sits just forward of the trigger blade). 

The magazine itself is well machined from plastic compounds, but follows Theoben’s slightly awkward design trait in this area, requiring a specific method of loading… as follows: the magazine (removable when the rifle is cocked and the lever held down), is held with the facing plate towards you; the facing plate is then rotated anti-clockwise until it stops; a pellet is then dropped into each chamber in turn, whilst making sure that the first doesn’t fall all the way through. Once the drum is fully loaded, the mag can then be pushed into place within the slot in the rifle’s action.

On test, with the magazine positioned, the action cycled without a hiccup, making this particular rifle a slick hunting tool out in the field.

On the range

Theoben's track record on triggers was for a while, one of their weak points, yet the MK4 unit on their latest PCP’s is simply superb, and a general improvement has crept through the range.

The sheer poundage being held back on any recoiling gun, however, forces the trigger involved, to work much harder; yet considering both my test rifles are sporting guns, the 2-stage unit fitted is fairly respectable, with a broad blade and a good, crisp, clean break. One criticism concerns the first pull weight, which still feels a little over-sprung. Reducing this could only help the overall release, and improve those groups still further.

Chronograph readings were near identical for both rifles here, with JSB pellets returning an average of 11ft/lbs in the SLR, against 10.8ft/lbs from the Evolution. Consistency was identical with both guns showing a variation of just 11fps over a 10-shot string. Accuracy was par for the course too, with regular 5/8 inch groups over 30yds from the underlever ( the average hunting range with an airgun), against the Evolution’s half inch clusters.

At around £700, the SLR98 on show here doesn’t exactly come cheap. Yet just recap that spec for a moment; a superb thumbhole stock adding sumptuous comfort and support, allied with a hi-tech, original multi-shot action. If pride of ownership is allowed into the equation, then the finish alone earns a tick in that box.

The choice here really comes down to multi-shot or break barrel. In the SLR98, Theoben have a quality hunting gun, oozing with character, that offers that little something different. But the sheer simplicity and smooth handling of the break barrel Evo in a somewhat lower cost package at less than £450, means there will be a ready market for both.

Technical Specifications
Model	Evolution / SLR98
Manufacturer	Theoben Ltd
Country of Origin	UK
Type	Break-barrel gas-ram / Underlever, multishot gas-ram
Calibre	.22 on test (.20 and .177 avail) / .22 on test (.177 avail)
Weight	7.5lbs / 7.7lbs
Overall Length	40.5inch / 39inch
Barrel Length	10.5inch / 9.25inch
Stock	Walnut sporter / Walnut Thumbhole
Power-Source	Gas-ram / gas-ram
Velocity	(JSB .22 pellets) -over 10 shot string: High: 557fps / High: 561 Low: 546 / Low: 550 Ave: 552 / Ave: 557 Vari: 11fps / Vari: 11fps
Energy:	10.8ft/lbs / 11ft/lbs
Trigger	2-stage adjustable / 2-stage adjustable
Price	£439 / £713
Options	Various silencer options / £748 with Evolution silencer (add £30 approx for all left hand versions)

All Prices Are Guides Due to the Changes in US & European Exchange Rates

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