SIG Sauer ASP20 Air Rifle: Part 2

Introduction

I told you all about the development of the SIG Sauer ASP20 air rifle in part one of this article. Now that I have a .22 caliber ASP20 of my own, I can test it more thoroughly. I plan to hold nothing back!

Testing the ASP20 on My Own

In part one you learned that SIG gave a scoped rifle to every writer who went on their factory tour in July of 2018. I asked for the .22 caliber because, at this power level, I felt it would be the smoothest of the two. Ed Schultz of SIG agreed with my decision. SIG sent me the rifle with the Whiskey3 scope already mounted and sighted-in at 10 yards.

Wood Stock or Synthetic?

When I first saw the rifle at the 2018 SHOT Show I thought the stock was synthetic, but it turned out to be wood. My experience has been if an air rifle stock is sleek and slender it’s always synthetic. Wood stocks tend to be too thick at the wrist and through the forearm. Not so for the ASP20 stock. Its wood stock is very slender in all the right places, plus the laser carving on both the pistol grip and forearm is finely detailed and made for a better grip.

When I hoist the rifle to my shoulder, everything feels right. The stock and controls are 100 percent ambidextrous and are placed so that the rifle feels custom-tailored for me. I thought it was just a fluke that they got it that right for me, but one evening soon after it arrived I showed the rifle to Larry, a friend from my church who had been eagerly awaiting its arrival. He’s two inches shorter than me and probably 75 pounds lighter. Larry is not a diehard airgunner, so he represents the public better. He also owns a Gamo breakbarrel, so he has experience with a spring gun. I watched closely when he hefted the ASP20 for the first time.

First Impression

When he cocked the rifle, he told me it felt smooth and well-made. Then, after his first shot, he looked at me with a big smile. Apparently, I had told him the truth about how smooth the rifle feels when it fires. As soon as the rifle with the synthetic stock became available with the Whiskey3 scope bundled, he bought one!

Larry is a cabinetmaker of the first order. So, when I pointed out that this stock was wood and not synthetic, he was surprised. It even fooled someone who really knows wood!

What About Wood?

This wood stock feels dead solid. There is no hollowness to the butt. SIG tells me it only adds about 8 ounces to the weight of the rifle, which for my scoped specimen is 9 lbs. 12 oz. The unscoped rifle weighs 8 lbs. 8 oz. (roughly, as the wood stocks will have slight variations from the density of the wood), so the Whiskey3 scope and mounts must weigh 20 oz.

And Synthetic?

The synthetic stock had its own separate development program. When you look at a picture of the synthetic stock online, it looks like it has an adjustable cheekpiece. Currently that is just a line on the stock. The cheekpiece does not adjust — yet. SIG has every intention of offering a stock with an adjustable cheekpiece in the future, but they first had to get the basic synthetic stock into production. They are rolling now, so we should see the adjustable cheekpiece sometime next year. These people do not shoot from the hip, so they will take all the time they need to make it right.

The butt is capped by a soft solid black rubber pad that sticks tight against your shoulder. It also prevents the rifle from slipping when it’s stood up in the corner.

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Description

The rifle is remarkably easy to cock in spite of the impressive power. That’s a weakness with most gas pistons. The one that I shot at SIG was well broken in and cocked with at 33–34 lbs. of effort. Most gas spring guns with this kind of power will cock at 50 lbs.

The rifle is 45.6-inches long and has a 137⁄8-inch pull. The barrel is 13.8 inches and is capped with a fat 65⁄8-inch silencer that has active technology (i.e. it really works).

There are no open sights, but a Picatinney rail is permanently attached to the top rear of the spring tube as a scope base. Use scope rings that come with either Weaver or Picatinney bases. As I mentioned my test rifle came with a Whiskey3 scope already mounted on what look like either low or medium scope rings, so that’s the scope I tested. This scope is just as novel in its own way as the rifle! I’ll have more to say about it in a bit.

Trigger

We learned in part one that the Matchlite trigger in the ASP20 is fully adjustable. And it has been made idiot-proof. The trigger pull weight adjustment screw bottoms out when turned to the limit in one direction and turns without effect when it reaches the other limit. Between the two limits you have full control to select the pull weight that best suits you.

The other adjustment is the length of the stage one pull. If you don’t want a two-stage trigger, stage one can be adjusted out entirely. If you want a long first stage you can have that. And your adjustments are limited in both directions to a safe operation.

Trigger Pull

Measuring the trigger as it came from the box, the first stage took one pound and nine ounces and stage two broke at exactly two pounds every time. At that level it is a half-pound lighter than what SIG says is the minimum pull weight. It is so light and crisp that I didn’t want to adjust it, but this is a test, so I adjusted it heavier

At first I turned the screw counter-clockwise to see if what SIG says about the trigger not going below the minimum. Or, at least that’s my story. I won’t tell you that I turned it backwards by mistake. But the pull stayed at two pounds. So the design really does work.

Then I adjusted it clockwise and raised the pull effort to two pounds and seven ounces. Yes, the pull weight can be adjusted successfully.

First Stage?

The first stage was adjusted the way I like it, but for the sake of this test I tried to adjust it out. Some shooters want a single-stage trigger, which was worth going for. I succeeded! The single-stage pull was long and I could feel movement in the trigger blade, though there was no real creep as the blade advanced. I define creep as a rough starting and stopping of the trigger blade through the arc of the pull.

After testing that function, I adjusted the trigger back to exactly where I want it — a long first stage followed by a short crisp second stage. The Matchlite trigger is a marvel. You’re going to enjoy it!

Safety

Here’s the last thing about the trigger. The anti-beartrap device in the trigger mechanism prevents the breech closing on your fingers while loading. Even though it works as advertised, I still advise everyone to hold onto the muzzle when the barrel is open, so if the gun were to fire you could prevent the barrel from closing. It’s just extra insurance.

The safety switch is manual and there’s a switch on both sides of the stock, above the trigger blade. You decide when to put it on and take it off. This is a radical departure from the lawyer-driven norm that assumes shooters are incapable of independent thought.

My Gun!

Now that I am by myself and things are quiet, let’s examine the silencer. I mentioned that it’s a real one with technology inside. Instead of baffles SIG uses three “hair curlers,” in series and each is wrapped with felt. I can tell you that they definitely work. Also the gas piston in this rifle is very quiet, which makes the ASP20 the quietest spring-piston airgun at this power level.

The silencer is not made to disassemble, so for countries that don’t allow them SIG will have to build rifles without the silencer’s guts. They are considering it, because they don’t miss a beat when it comes to marketing.

Tools

SIG packs some tools with the rifle. There is a screwdriver and an Allen wrench to adjust the trigger, and in my case, since the rifle came with a scope, I got the Torx wrench for the screws on the rings. And, I got something more with the scope that I will now discuss.

Whiskey3 ASP 4-12X44 Scope

The Whiskey3 ASP 4-12X44 scope is made specifically for the ASP20, and does something airgunners have waited a long time to see. It is matched to the ballistics of certain pellets, allowing the shooter to dial the range to the target on the scope’s elevation knob and the pellet will always strike at the intersection of the crosshairs, once you are sighted-in. At least that’s the theory. I did test that on the SIG tour and it worked, but now I can play with the scope as much as I want and really pin down its operation.

Field target competitors have modified their scopes this way for many years, but this is the first time a commercial scope has been set up this way.

The vertical crosshair adjustment knob is calibrated in yards to the target rather than just having simple index marks. Once you have sighted in with the ballistically-matched pellet, just dial the turret to index the distance to your target and put the crosshairs on what you want to hit.

Can the Scope Be Used Without a Rangefinder?

What if you don’t want to use the ranging system of the Whiskey3? What if it doesn’t match the trajectory of the pellet you want to shoot? SIG sends you a standard MOI adjustment knob (see the picture with the tools) with the scope that replaces the yardage knob. The scope is calibrated in 1/4 MOA clicks, so making the switch is not difficult.

The scope adjusts for parallax down to seven yards and out to infinity. The index marks on the objective bell from 10 yards to 50 yards occupy half the arc of the bell, so there is some range-finding capability, though 12-power doesn’t give a lot of resolution. The distance at which this can be done with high precision is limited to perhaps 25 yards.

While the Whiskey3 is new to airgunners, firearms scopes have similar ballistic adjustment features and must be calibrated for a specific round of ammunition. As long as they use a quality rangefinder to determine the exact distance to the target, such scopes are incredible. But don’t guesstimate distances and expect the system to work. I’ve had shooters tell me that a target I knew to be at 75-yards was 200 yards away! Without a rangefinder many people can’t estimate range accurately enough to use a ballistic scope.

Field target shooters only shoot between 10 and 50 meters (11 and 55 yards), so they don’t have nearly the problems that firearms shooters have with this concept. They cannot use rangefinders in a match, but they have learned how to use the parallax adjustments of their scopes as a makeshift rangefinder. When the image comes into focus, the range that’s indicated on the parallax knob or objective bell is the range to the target. To make this work you need to focus on very small things like blades of grass and twigs near the target, which is why field target shooters prefer scopes of 40 power and more.

If you plan to use this ranging feature you can’t skimp on ammunition. Whatever pellet the rifle and scope are set up to shoot is what has to be shot. Otherwise you are wasting ammunition.

Let’s check velocity first. Velocity is just another way of stating muzzle energy, and in the .22 caliber I’m testing SIG tells us the energy should be as much as 23 foot-pounds. Not all pellets will be equally powerful, so they have stated the maximum.

Velocity with the Lead Crux Pb

I started with the pellet SIG set up the Whiskey3 scope to use — the .22-caliber SIG Crux Pb (lead). The lead Crux is domed and weighs 14.66 grains, according to SIG. I weighed several on an electronic powder scale and found them between 14.7 and 14.9 grains. Most weighed 14.7 grains, so I will calculate their energy from that weight.

Ten Crux lead pellets averaged 856 fps from my rifle. The spread went from 850 to 868 fps, so a difference of 18 fps. From a brand-new spring rifle, that’s very good! At the average velocity, this pellet produces 23.92 foot-pounds of energy at the muzzle. So, with the recommended pellet the ASP20 has already exceeded its expected energy of 23 foot-pounds.

I have to mention that the Crux pellets are not easy to load into the breech. I remember that from my time at SIG, and it appears they are still that way. They have heads that are quite large and that is where their accuracy comes from, but it also makes them harder to load.

Velocity with the JSB Exact Jumbo

The second pellet I tested was the 15.89-grain JSB Exact Jumbo. When I tested a .22 rifle at SIG, this was the most accurate pellet, and it also matched the trajectory set in the Whiskey3 scope. In the rifle I’m now testing, this pellet averaged 830 fps. The spread went from 824 to 835 fps — that’s a spread of 11 fps. At the average velocity, this pellet produced 24.31 foot-pounds of energy at the muzzle—slightly more than the SIG pellet and well above the rifle’s advertised power.

Velocity with the JSB Exact Jumbo Heavy

Next up were some 18.13-grain JSB Exact Jumbo Heavy pellets. They averaged 776 fps in the test rifle and the spread went from a low of 771 to a high of 780 fps That’s a difference of just 9 fps. At the average velocity, this pellet produces 24.25 foot pounds of energy. So this brand-new ASP20 I’m testing is performing beyond the SIG claim of 23 foot-pounds. New spring rifles usually don’t make more energy; they make less. That goes for gas piston rifles, as well. Only as they break in do they speed up. This is potentially one hot breakbarrel!

How Fast?

The last pellet I tested in the rifle was the SIG Crux Ballistic Alloy dome. These pure tin pellets weigh only 10.03-grains which makes them fast! In the test rifle they averaged 1,064 fps, with a spread from 1,056 to 1,070 — a span of just 14 fps. At the average velocity, this pellet produced 25.22 foot-pounds of energy — the highest in the test! There are gimmick pellets that are even lighter than this one that will exceed this velocity, but this is a pellet you can expect to actually hit where you aim.

I must note that these alloy Crux pellets loaded hard, just like the lead ones. In fact, I seated them deep in the barrel with a pen because my fingers got sore pushing them in directly. The JSB pellets went in snug but easy.

Easy Cocking!

Throughout this test I was amazed by how easy it is to cock the ASP20. The brand new rifle I’m testing cocks with just 33 lbs. of effort! That’s an easy 15 pounds less than similar air rifles with gas pistons that produce the same power. I could shoot this one for hours. And there is virtually no noise while cocking. The gas piston is virtually without sound.

Barrel Loose When Cocked

Once the barrel is cocked but before it closes, I noticed that the barrel swings freely. It doesn’t stay put in any position like we try to make other breakbarrels do when we tune them. That’s because of the keystone breech. This breech locks up solid when it’s closed, yet the barrel pivot doesn’t add one ounce of resistance when the barrel is free. The action fork doesn’t have to squeeze this barrel’s base block to make the breech tight because the keystone breech takes care of the alignment and breech lockup.

Setting Up the Scope and Rifle

Whenever I read about a writer testing something at the plant where it’s made, all sorts of doubts creep into my mind. I think “they” are smart enough to hand-select the gun being tested, then they tuned and adjusted it to give the best possible results in anyone’s hands. In fact, if they didn’t do that, they are fools. But now a brand new rifle is in my hands — away from the influences of the engineers. It’s time to see what this ASP20 can do in the real world!

The rifle came to me with the scope mounted, but there are other things to do before testing for accuracy. The first is to check the stock screws and the scope mount screws for tightness. The Beeman company used to say to tighten the stock screws as tight as they would go, then turn a quarter turn more. Don’t do that with the ASP20! This rifle is so smooth that it’s not going to loosen those stock screws the way the harsh spring guns of the 1980s did. Just ensure the stock screws are tight and leave them be.

When I checked them I found the scope mounts were already secure. Nothing more had to be done to them. Now I could set up the Whiskey3 scope to work as it was designed.

Ed Schultz of SIG told me the scope on my rifle had been zeroed at 10 yards, so that’s where I started. I first used the SIG Crux Pb (lead) domed pellets that SIG recommends. I will also use JSB Exact Jumbo domes and Air Arms domed pellets, to see how they compare. Although the rifle was supposed to have been zeroed at 10 yards, the scope scale on the elevation knob had been turned to indicate 20–35 yards, as you have already seen.

Crux-Seated-Deep

I started with five Crux pellets seated deep. These pellets do not go into the breech easily, so I used the tip of a pen to seat them about 1/8-inch deep in the breech. That prevents damage to the pellet skirt when the breech is closed. At 10 meters five pellets went into a 0.259-inch group that was high and to the right of the aim point.

Crux Seated Flush

Next I tried five Crux seated flush with the breech — thinking that was what the person at SIG had probably done. I used the flat handle of a pocketknife to press the pellet flush to the breech, because it was too hard to do with my fingers. The first shot with the pellets seated flush was dead on target. I thought I was home free, but the group then spread out to 0.58-inches, which is not so good for only 10 meters.

Clearly we want to seat the Crux pellets deep in this rifle. I could have tried to zero the rifle for the deep-seated Crux pellet, but before doing that I wanted to see what the next pellet could do.

JSB Exact Jumbo

The JSB Exact Jumbo pellet had performed well on the SIG tour, so I wanted to try them in this test. Up to this point the scope remained where it was from the factory. In contrast to the Crux pellets, these JSB pellets seated flush in the breech snugly but easily. The first five made a very small 0.175-inch group at 10 meters, which was nice but unfortunately, was too high. I won’t put you through each and every scope adjustment that was made, but after a total of 13 clicks down and three to the left I got the JSB pellet hitting close to where I aimed. Five JSB pellets landed in 0.308-inches at 10 meters. That’s close enough for me.

Set the Elevation Knob for the Distance at which the Rifle is Sighted

I added three more clicks of left adjustment after this target for good measure. Before moving back to 25 yards, though, this is when the scale on the scope gets adjusted. I removed the 2mm Allen screw on top of the elevation adjustment knob and lifted the scale off the knob, taking care not to turn the knob as I did. Then I placed it back on the knob with the number 11 (11 yards is 10 meters) on the scale aligned with the index mark. Since I had just sighted-in at 10 meters, the scope elevation knob was now set at that distance. Tighten the Allen screw and you’re done. Now I can move back to 25 yards.

25 Yards

Back at 25 yards, I adjusted the scope’s elevation knob for this new distance. If this Whiskey3 scope works as advertised, the pellets should pass through pretty close to the center of the bull, when I shoot from 25 yards — as long as I dial the elevation knob to that distance. I now adjusted the parallax on the scope until the image was clear and then adjusted the vertical adjustment to 20–35 yards.

Then I shot five JSBs. But they didn’t land in the center of the bull. They all landed high and to the right. The group is nice, at 0.472, but it isn’t where I expected it to be. It’s very close, but not exact. What was wrong?

DUH!

And then it hit me. SIG set this scope up for the ballistics of the Crux lead pellet — not the JSB. I hadn’t shot that pellet at 25 yards yet. This is what happens to firearms shooters with ballistic scopes when they substitute ammo! What would happen with the Crux?

The first Crux pellet hit the center of the bullseye! Second pellet was next to it on the right. Then one went high and left, followed by two more to the right. In the end I got a horizontal group that measures 0.614-inches between centers. It does demonstrate that the Crux will go to the point of aim when the Whiskey3 scope is used. But I wanted a tighter 25-yard group. I could try to match the ballistics using a different pellet. How much does a Crux lead pellet weigh?

What lead pellets weigh close to the 14.7 grains of the lead Crux? Ed told me the scope was set to work best with pellets in the 14.5 to 16-grain range. Air Arms makes a domed pellet that weighs 16 grains on the nose.

Air Arms Domes

I next shot a five-shot group with the Air Arms dome and it is DEAD-ON for elevation with the same scope setting! All it needs is a little bit of left adjustment. Five pellets went into a group that measures 0.412-inches at 25 yards. It’s the smallest 25-yard five-shot group of this test.

The Whiskey3 scope does indeed work as advertised. It hits the point of aim at any distance that’s dialed into its elevation knob, so long as the right pellet is used. I’m jumping from pellet to pellet in my testing, but in reality you pick just one pellet and stick to it. Then things settle down.

We are also starting to see the accuracy potential of the rifle. Five-shot groups are not the best for demonstrating true accuracy, but until I have the rifle dialed in they allowed me more time to test things. There are still a few more things to do to set up the rifle.

Clean the Barrel

Ed Schultz told me that some of the rifles seem to need a light barrel cleaning when they are new while others do not. I wanted to clean it and then try those Crux pellets once more.

But, could I really clean this barrel in the recommended way, which is a solid cleaning rod running a cloth patch from the breech through to the muzzle? Won’t I risk loosing the patch in the silencer baffles? Not at all!

Because, like many other airgun silencers today, the ASP20 silencer has no baffles. NO BAFFLES! There is nothing inside to grab your cleaning patch.

I already showed you the guts of the ASP20 silencer. Three “hair curlers” are lined up in tandem inside the can. They aren’t really hair curlers, but they look a lot like them, and several airguns are using them. They are essentially hollow tubes with holes on their sides where the turbulent air escapes. And they have no baffles. A wrap of felt then deadens the sound of that air.

Inside-Spool

Ed did say that where the spools connect there is a “step” that’s 2.3mm high. That’s 0.0906-inches tall. So, if you want some baffles, there you go. When Ed cleans he uses a common jag to push patches through the bore. Jags are just pointed pieces of metal that have no good way of really holding the patch, other than they are sticking through it and pushing it in the same direction.

Barrel Clean

It took me about 10 minutes to clean the barrel, using cloth patches, only. I did wet some of the early patches with Safari Charlie High Tech Gun Cleaning Lubricant, which I have found works well on spring gun barrels.

I used 20 patches in all. The early ones were hard to push through the bore, but after about 12 patches they started going through easier. The last few met with very little resistance. Twenty patches were used and none were lost. I even switched to a cleaning loop on the rod and pulled a couple patches back through the barrel — just to challenge the silencer thing.

How Accurate After Cleaning?

I was still experimenting with different pellets at 25 yards, but the Air Arms dome seemed so good I just had to try it again, after cleaning the barrel. This time I shot a five-shot group that is the smallest group I have ever shot with a spring-piston air rifle at 25 yards. Five Air Arms pellets went into a group that measures 0.072-inches between centers. This group is so small that I not only put a dime next to it for scale, I also put an obsolete American silver three-cent piece — an extremely small coin. The dime measures 17.9mm in diameter, but the three-cent piece is only 14mm!

I continued shooting groups to learn all I could from the rifle. Now it was time to switch to more serious 10-shot groups that really tell the story about potential accuracy. Anybody can get lucky five times in a row, but ten times straight isn’t luck. Ten shots tell the accuracy story as well as a hundred.

More from Ed Schultz

Ed told me to try some Wrath Ballistic Alloy pellets. They are lighter than the scope was designed for, so they won’t work the way I have been describing, but you can still sight the scope in for them at any distance. They seem to do very well in the ASP20 barrel. He also said the barrel is tight and any pellet with a head larger than 5.52mm will be tight.

Wraith Ballistic Alloy pellets are made from pure tin, so they are expensive. However I have found that the pure tin SIG Match Ballistic Alloy pellets are often the most accurate pellets of all in world-class target rifles.

Once I adjusted the scope for the lighter pellet, and returned to the artillery hold, 10 Wraith Ballistic Alloy pellets made a beautiful 0.324-inch group at 25 yards. The group is very round, which indicates the rifle likes the pellet very much!

Summary

I’m not done testing the ASP20, but I am finished with this report. SIG Sauer has designed a spring-piston air rifle from a clean sheet of paper that performs like a custom rifle out of the box. It’s 100 percent American-designed and-made, which is a story in itself. 

Read part one here.

SIG SAUER ASP20 AIR RIFLE SPECIFICATIONS

Manufacturer: SIG Sauer
Model: ASP20
Calibers: .177 and .22
Length: 45.6-inches
Weight: 8.5 lbs unscoped, 9.75 lbs scoped
Pull: 13.8 inches
Sights: None, but a Picatinny rail for scope
Stock: Wood or synthetic
Price: $430 wood, $350 synthetic
Scope: Whiskey3 $350 (bundled for less)
Contact: (603) 610-3000, SigSauer.com/products/airguns/