Stephen Archer gets a privileged insight into the design and technology of the new SIG Air ASP20 rifle
Stephen Archer is at SIG SAUER in New Hampshire, with their new ASP20 rifle
So, there we were at the corporate headquarters of SIG SAUER in Newington, New Hampshire, USA. That’s your illustrious editor, Terry, me, and a number of invited airgun scribblers. The date was 25 July 2018 and we were attending the official unveiling of the new SIG ASP20. It was the world premiere of the company’s new break-barrel, gas-ram air rifle!
We’ve seen prototypes of this new gun before, at the SHOT Show and IWA, but this was the formal launch of the final production gun. SIG is locked and loaded for the ASP20 and we saw some of the first production guns coming off the line.
These first production guns are to US specification, as you would expect. They give a muzzle energy of 20 ft.lbs. in .177 calibre, and 23 ft.lbs. in .22 calibre. That’s reasonably standard for magnum gas-ram break-barrels on this side of the Pond.
The SIG ASP20 is the first new break-barrel air rifle to be completely designed and manufactured in the USA for many years. Certainly, it’s the first this century, and possibly the first ever. As Joe Huston, the General Manager of SIG’s airgun business said, ‘This is definitely the first to be designed and built in the USA by a firearms company’.
It has multiple new, innovative features that show a completely fresh approach to air rifles design. The SIG ASP20 is the first model in the SIG Air precision line. Yes, SIG Air is the new name for SIG SAUER’s airgun division.
At this press launch, the company was amazingly open about the new technology they’ve developed for the product. There’s been a great deal of R&D undertaken for the ASP20, and SIG wanted to ensure that we understood all of it. The company was not holding back about the new SIG ASP20, and for good reason – it’s obviously an outstanding new introduction.
BETTER BY DESIGN
SIG explained that they had decided early on, the core design goals for the ASP20. They didn’t want to produce ‘just another breakbarrel. Their aims were for the ASP20 to be superior to any other magnum power, break-barrel air rifle on the market, in three key areas; it was to be easier to shoot, consistently more accurate, and more pleasurable to shoot than the competition.
From a technology perspective, this meant a great amount of time and effort devoted to the design and engineering of several key features, including barrel lock-up, cocking effort, trigger pull and rifling.
BANISHING BARREL DROOP
SIG explained that they were intent on
eliminating the barrel droop endemic in break-barrel air rifles. They also wanted to achieve consistent lock-up, so SIG engineers developed a proprietary ‘keystone’ breech lock design, the geometry of which eliminates barrel droop, they told us, with matched angles between the breech block and fork.
Another key technology used in the ASP20 is ‘match drilling’ of the pivot holes through the barrel and receiver. This means that the pivot point for the barrel/breech interface was drilled just once through both parts using a jig.
This makes the SIG Air ASP20 air rifle different from other break-barrels, which have the parts drilled separately then matched together during assembly. That approach can require additional parts in expensive guns, or lead to a poor fit in cheap ones, says SIG. Either way, it’s clear that the match drilling process is likely to produce superior fit and operation for the all-important pivot point of the ASP20.
CURTAILING COCKING EFFORT
First, SIG benchmarked the cocking effort required for other break-barrel air rifles, both springers and gas-ram guns. As you would expect, they found that the cocking force increased with the muzzle energy, but they also found that the claims of some other manufacturers for cocking effort were not matched by the sample guns they tested. It appears that some manufacturers’ claims for cocking effort are lower than they actually are; just like fps claims are usually higher than those actually achieved.
JUST FANCY THAT!
From the data SIG presented to us, you can see immediately that the cocking force for the 20 ft.lbs. muzzle energy, SIG Air ASP20 air rifle is close to that of mid-power guns – we’re talking US expectations here – 12 to 16 ft.lbs. It’s significantly less than other magnum models of 20 ft.lbs. and above.
This reduced cocking force is largely due to the new SIG SAUER Glidelite cocking mechanism built into the SIG Air ASP20 air rifle. SIG explained that his includes a low-friction bearing surface for smooth rotation of the cocking arm and decreased contact pressure. In addition, there’s a wedge-shaped detent. This incorporates a double-spring design that makes it easier to break the barrel before cocking.
SIG is making their barrels for the SIG Air ASP20 air rifle. As the company already manufactures excellent barrels for firearms, this was a very logical step for the new airgun, so barrels for the ASP20 are being manufactured by SIG in New Hampshire. They’re made on the same machines used for firearm barrels, and they have rifling of SIG’s own design.
The company says that this rifling has two design goals; one is to minimise unnecessary distortion of pellets and the second is to create a highly effective seal on the pellet skirt.
ASP20 air rifle barrels are button-rifled. They have 12 lands and a twist rate of 1 in 450mm. The barrels are air gauged and there’s a bore scope inspection on every single ASP20 barrel.
In addition, the silencer housing is laser welded onto the barrel. In total, there are no less than 18 different laser welds on each ASP20.
Laser welding equipment is expensive – very expensive – but SIG has chosen it for the ASP20 to remove the chance for distortion present with conventional welding, particularly where the Picatinny rail is welded to the compression tube and other key areas, like silencer attachment.
There’s no doubt about it; a huge amount of time and effort has been put into developing the trigger for the SIG Air ASP20 air rifle. It’s called the ‘SIG ASP Matchlite’ trigger and it has some unique features. SIG is applying for two patents in the trigger assembly alone – that’s how unique it is.
The trigger blade itself is based on that of the SIG SSG3000 centrefire rifle. It’s manufactured from an advanced nylon polymer, over-moulded onto a zinc bearing sleeve. SIG says that this reduces weight and friction, as well as providing improved balance.
JUST DON’T CALL THIS A ‘PLASTIC’ TRIGGER BLADE
Design goals for the Matchlite trigger were for it to be safe and provide a clean break. It would also allow the owner to customise the feel over a wide range of adjustment. The result is a trigger with a manual safety operable from each side of the gun. It also has an adjustment mechanism which, to my knowledge, is unique on spring-piston and gas-ram airguns.
The trigger of the SIG Air ASP20 air rifle is adjustable in two-ounce increments, between 2.5 and 3.5lbs. There are eight distinct settings selectable using a screwdriver. There’s an unusually long spring around the trigger adjustment strut to provide this range of adjustment capability, and adjustment is made using a ratchet system with individual clicks.
Controlled by a single setscrew, these adjustments change not only the trigger pull weight, but the pull characteristics, too. The ASP20 trigger can be adjusted to
give single or two-stage operation, or a point between. Importantly, trigger adjustments can be made to the ASP20 without the need to remove the stock, or peer up under the trigger guard.
Another key feature – unlike most other triggers, the SIG Air ASP20 air rifle trigger cannot be adjusted out of its safe tolerance range. A bracket assures the minimum sear engagement required for safe trigger function.
SIG SAUER is serious about quality, and that means they’re serious about testing; one reason their products find such favour with the military around the world. Ron Cohen, the company’s President and CEO, himself a former active-duty soldier, explained that the ASP20 was subjected to the same testing regimen as SIG’s military firearms. He knows what it means to depend on your rifle, and he demands that SIG users can depend on his products – including the ASP20.
Now, I don’t suggest you try this at home, but here are some of the tests SIG undertook on their new air rifle:
For example, it has to pass a 72-hour saltwater spray test and still operate correctly. They also subjected cocked and loaded ASP20s to the SIG test of two minutes totally immersed underwater. They had to fire after this test, and they did. We saw the video to prove it!
SIG told us that they had tested the ASP20’s breech/cocking design for up to 20,000 – yes, TWENTY THOUSAND – actuations to ensure reliability.
That’s just some of what it takes to be approved as a SIG product ,and I know the editor can’t wait to test the sub-12 ft.lbs. version of the ASP20 as soon as it reaches the UK.
An overview of part of one of the SIG SAUER factories. The big white boxes are CNC machines. The ASP20 is assembled under the ‘Assembly’ sign, top left.
Ed Schultz, SIG’s Airgun Engineering Manager, explains the Matchlite trigger.
John Bright - boss of SIG Air’s UK distributor, Highland Outdoors, puts in the range time.
The cocking lever assembly is attached to the barrel before moving down the line.
After the the barrel has been fitted, it’s time to attach the trigger pack, then the gas-ram unit.
Here’s a CAD rendition of the complete ASP20 trigger pack. Part 1 is the trigger weight adjustment assembly. Part 2 is the trigger stage bracket again, it’s green this time.
Cocking Force. This chart shows different cocking efforts and muzzle energies for a number of air rifles. You can see how the ASP20 (the star) is superior to the others tested. Data supplied by SIG SAUER.
The ASP20’s detent mechanism includes two springs, one inside the other, to make breaking the barrel easier.
Components of the Matchlite trigger. That arm on the grey-coloured part (the trigger stage bracket) forward and down from the blue safety pin, prevents unsafe adjustment of the trigger.
The final completed air rifle, as it comes off of the line.
The green parts of this CAD rendition show SIG’s ‘keystone’ breech lock design.