Air Arms S400 MPR FT: Part 4

by B.B. Pelletier

Part 1
Part 2
Part 3

The Air Arms S400 MPR FT rifle still has a surprise for us!

This special report about the Air Arms S400 MPR FT rifle was unplanned, but blog member Coax asked for it. Today will serve as the best lesson I’ve ever written on how to properly use a chronograph, because I made a huge mistake and the chronograph straightened it out for me.

Coax told me about a transfer port limiting screw that could be turned out to increase the velocity of the rifle. I was unable to locate it from his description, and we went back and forth several times before I found it. At least, I thought I’d found it. Therein lies the huge mistake I made, and the save made by the chronograph, all of which should be a good lesson in pneumanology.

The “secret screw”
Below is a photo of where the power-adjustment screw resides. But don’t just loosen the screw in that picture or you will be guilty of the same huge mistake I made. Because I did loosen it 2.5 turns and I got results. They were quite positive and I was already writing today’s report in my mind, after recording each of 99 shots, when I discovered a huge mistake. I will share those results with you now, but please don’t act on them until you’ve read this entire report, because that screw isn’t the one to adjust this rifle!

After much communication, I finally located the “secret screw” that Coax is talking about. But I got a huge surprise, so please read the entire report.

I filled the reservoir to an indicated 190 bar. I read the scale on my AirHog carbon fiber tank, which I know to be reasonably accurate. Then, I began shooting Crosman Premier lites, which were featured in Part 2 of this report.

Shot Vel.
1….. 784
2….. 791
3….. 783 (lowest velocity recorded)
4….. 785
5….. 792
6….. 790
7….. 785
8….. 790
9….. 784

At this point, I’ll reflect on what we’re seeing, even though it’s not the result I was after, nor had I done the right thing yet. If you go back to Part 2, you’ll see that when I filled the rifle initially, I filled it to 190 bar on the tank gauge. The manometer on the rifle read lower than that — about 180. The initial velocity was in the 764 f.p.s. range with the same Premier lites that were used in this test, so turning out the small screw on the right side of the receiver seemed like the right thing to do. Because, as you can clearly see, the rifle started out 20 f.p.s. faster and averaged about 791-792 f.p.s. for the first 30 shots. The maximum velocity spread was 17 f.p.s. for this 30-shot string.

So I continued.

Shot Vel.
35…..804 (about 170 bar)
48…..814 (fastest shot)
54…..802 (150 bar)

Okay, we’re up to 60 shots on this fill and no sign of the power dropping. Also, we’ve dropped below the 150 bar pressure level, according to the onboard pressure gauge (manometer). In this string of 30 shots, that is from shot 31 to shot 60, the average velocity has climbed to just about 800 f.p.s. That’s 16 f.p.s. faster than the average of the first 30 shots, so the gun’s increasing in power. The maximum velocity spread for this 30-shot string is 18 f.p.s.

Let’s continue.

Shot Vel.
87…..792 (125 bar)

The final string shows the end of the power curve and the rapid drop-off back to the lowest velocity recorded in the beginning. Now I’ll analyze the entire string of 99 shots as I would see them if I were using the rifle to compete in field target.

The rifle really came up on the power curve at around 170 bar indicated on the rifle’s manometer. That was at shot 35. I would fill to that level, after making a permanent mark on the gauge, so I could find that level easily when filling again. If I consider shot 84 to be the final good shot in the gun, I would have from shot 35 to shot 84 as a useful string. That’s 49 good shots, which I would round up to 50 shots. I would have 50 good shots in the gun that went as slow as 795 f.p.s. and as fast as 814, for a total shot string variance of 19 f.p.s. That’s pretty good; and if you check back with Part 2, you’ll see that I’ve actually raised the average velocity of the rifle by about 15 f.p.s. over the useful string. So, adjusting the “secret screw” did change the performance of the rifle.

Only that wasn’t the secret screw! After completing this exhausting test and evaluation, I was wondering why Coax said the secret screw was INSIDE a deep threaded hole. Clearly it wasn’t on my rifle. Unless…!

Oh, my, gosh! I ran that whole test and never even touched the real secret screw! That screw, which Coax apparently is missing, is only the cover for the real screw. That was the huge error I made.

The real transfer port adjustment screw is located deep inside the hole that remains when the cover screw shown at the top of this report is removed. The Allen wrench is a 0.050-inch size.

Saved by the chronograph!
Here’s the real lesson for today. Because I had that beautiful, pressure-related velocity curve indicated in those 99 shots shown above, I didn’t need to waste any time once I adjusted the real screw. I filled the rifle to only 170 bar as indicated on the onboard manometer and started the second test.

Then, I turned the real power adjustment screw out one and one-half turns and shot a 10-shot string.

Shot Vel.
Avg. 886 f.p.s.

Next, the screw was turned out 1 additional turn.

Shot Vel.
Avg. 893 f.p.s.

The screw was turned out one additional turn.

Shot Vel.
Avg. 894 f.p.s.

What I learned
First, I learned that this was indeed the true power adjustment screw. Second, I learned that turning it out about two full turns is all that’s necessary. After that, the velocity increases are not significant. I finished the 30-shot series with about 140 bar left in the reservoir, so there are about 15 more good shots in the gun.

Taking the second string average as a power input number, the rifle now generates exactly 13.99, which is close enough to 14 foot-pounds of muzzle energy with this pellet. Use a heavier pellet and get more power because this is a pneumatic.

By referring to the chrono data chart that also had the pressure indicated, I didn’t need to waste any time running up to power. I knew where the power band was located, even when I was increasing the airflow. The valve still works the same, regardless.

That’s the power limit of this rifle. I imagine I could get up to 16 foot-pounds if I used a very heavy pellet, but the best pellet is always the most accurate one. Whatever that one produces is the practical maximum for this rifle.

The Air Arms Twice PCP Air Rifle: Part 1

by B.B. Pelletier

Air Arms S400 MPR FT alert!
Before I start today’s report, I want to make an update to the Air Arms S400 MPR FT blog. Blog reader “coax” asked me to adjust the air transfer port screw to see if I could increase the power of the rifle. Following his instruction to locate that screw, I removed the action from the stock, but I cannot locate the screw he mentions. He says it is located below the loading trough, which I took to mean underneath the loading trough (the bottom of the action) at the rear of the reservoir. Well, there’s nothing to see on the reservoir itself, but on the action just behind the reservoir there is a threaded hole like he describes. The problem is that there is no screw inside that threaded hole. And that is the only threaded hole that I can see.

So there isn’t going to be any power adjustment report on this rifle. If coax wants to send me photos of exactly what he’s referencing, I will look again, but otherwise, the report is completed.

The Air Arms Twice precharged pneumatic air rifle is a dual-reservoir rifle with the air cylinders arranged side-by-side. The rifle has a rollover raised cheekpiece, so it is reasonably ambidextrous, though the bolt stays on the right side.

What is a Twice?
Now, on to today’s report. The Air Arms Twice PCP air rifle will certainly never win any awards for the name! Why they didn’t call it the Double-Up or something — anything — but Twice is beyond me. However, in the spirit of Shakespeare who said, “A rose, by any other name…” we will proceed. (I haven’t forgotten that Pyramyd Air took a survey about other names. Maybe they’ll christen it something else in the near future.)

This view shows the ends of the twin air reservoirs. There’s only a single fill port on the end of the right reservoir tube (the tube on the left in this photo).

The name Twice refers to the twin reservoir tubes under the barrel. Obviously, they increase the amount of compressed air the rifle can hold, yet by their design, the rifle is not made substantially taller. Wider, yes, but in the same sense that a double-barreled shotgun is wide. It’s width with elegance.

And, I’m testing serial number 098425, for those who are keeping score. The rifle came to me with a Bushnell Banner 6-18x50AO scope mounted on it. While that’s a good, useable scope, it doesn’t do justice to a premium PCP rifle like the Twice. Since I have the Hawke Sport Optics 4.5-14x42AO Tactical Sidewinder rifle scope on hand, I switched it for the Bushnell. Why not? After all, one doesn’t buy a Ferrari and then fill the tank with 87 octane fuel! A premium rifle deserves a premium scope.

It is a big air rifle!
Let me get this out of the way; because when these rifles start selling, you’re going to read about it on the forums. The Twice is a very large air rifle. Those twin reservoir tubes make it a real handful and that’s that. Also the barrel’s shrouded, which adds to the look of massiveness. The rifle isn’t heavy, at 7.50 lbs., but it is muzzle-heavy. I know there are those who think a muzzle-heavy rifle is a bad thing, but it isn’t if you want to hit things! The extra weight out toward the muzzle slows down the tendency all rifles have to wobble. The Twice hangs right in your hands if you put your off hand just forward of the trigger. My Ballard is very muzzle-heavy, and it doesn’t seem to suffer any.

Of course, this is also a repeater. It features a 10-round magazine that loads the next pellet every time the sidelever pulls the bolt to the rear and shoves it forward again. Having used Air Arms repeaters in the past, I believe this one will be butter-smooth to cock and shoot. I’ll let you know when I test it.

Adjustable power
There’s a power-adjustment control on the right side of the receiver, with an index scale on the left side. I will test that function and report my findings during the velocity test.

Here you see the sidelever that operates the bolt. Just in front of the lever handle is the silver power adjustment knob. A scale on the other side of the rifle tells you where the power has been set.

It’s hard to see in this photo, but the symbol at the right of the scale is a plus, meaning greater power. The symbol at the left is a minus.

The specs say the Twice is a 20 foot-pound rifle in .177 caliber. Because it’s a pneumatic, it’ll develop the most power with the heaviest pellets…and I’ll be testing it that way. That’s the only way it’ll be the most accurate at long range.

The Twice also will be available in .22 caliber, which I think would be the caliber of choice for a gun in this power range. They rate it at 30 foot-pounds in .22 caliber, and that’s about what I would have guessed. There are so many wonderful new heavyweight pellets in .22 caliber that I would think an owner would want to test them all.

The specs also say you get 180 shots on low power and 60 on high. Unfortunately, a .22 caliber pneumatic will always be more efficient with air than a .177. That number was probably gotten with the larger caliber, but I’ll purposely test this .177 gun at both ends of the power spectrum for you.

General impression
The woodwork is nice, but it’s different than the classic look of the TX 200. Only the grip is checkered and the diamonds are sharp, laser-cut and very crisp. The Air Arms logo is also cut into the grip. The butt is scalloped below the cheekpiece on both sides for weight reduction, I presume. That lightens the rifle but increases the muzzle-heaviness.

The stock is finished evenly in a medium brown stain. The reservoir tubes are finished matte, and the shroud is a matching matte finish. The overall look screams “Hunter,” so that’s what I believe the rifle was made to do. With all that air on board, we should see a good shot string at all power levels.

The rifle is an FAC type. FAC stands for Firearm Certificate, which owners will need to own this airgun in the United Kingdom. Once a rifle has been designated FAC, it can never be downgraded to a legal air rifle again, so this will always be an FAC rifle. Because getting an FAC can be quite difficult in the UK, that means the Twice was created for the U.S. market, primarily, because we don’t have the same power restrictions the UK has, except for a couple of states. The United States is also starting to embrace airgun hunting, so I think Air Arms is testing the waters to see if the market is there for them. Certainly, they’ve seen the success of all the AirForce, Beeman, Benjamin, Daystate, Evanix and Weihrauch precharged rifles over here and want to get in on the market. It’ll be interesting to see if the U.S. hunting market can sustain a $1,360 PCP in the face of all the other guns that currently exist. If the Twice can deliver on the promise of power, accuracy, power adjustment and a long shot string, it just might be the best new gun in town. We shall see.

Air Arms S400 MPR FT: Part 3

by B.B. Pelletier

Part 1
Part 2

The Air Arms S400 MPR FT is a beautiful international-class field target rifle.

Today, we’ll test the accuracy of the Air Arms S400 MPR FT precharged pneumatic air rifle, and it’s a challenging test because I shot this 12 foot-pound rifle at 50 yards on a day with 20 mph winds. The wind was from my 6 o’clock, and the trees created some swirls. I had to wait out the gusts and shoot in relatively calm periods.

However, before I begin today’s report I’ll rant a little. I was testing several things last week and someone asked me to test his Talon SS. He claimed he could not shoot groups smaller than 2 inches at 30 yards and most of his groups at that range were four inches. Well, I’ve never seen a Talon SS that shot that bad; even the one with the only Lothar Walther barrel I ever condemned in my three years at AirForce.

When I asked for pellets to shoot in his gun he handed me Crosman Premier hollowpoints in a tin can. The first pellet fell through the barrel and the second one wouldn’t enter the breech, so I asked for some other pellets. He gave me some Daisy pointed pellets.

There’s your problem!
Folks, just as an airplane cannot fly on 87 octane gasoline, a precision air rifle cannot be accurate with discount store pellets. Yes, I know how “cheap” they are; but really, guys, when the rubber meets the road, you need better ammo than this.

I don’t want to start a long argument about bang for the buck, or anything like that, so I thought I’d show you just how important the right bullet/pellet is. Last week, I also happened to get out to the range with my Ballard target rifle. This time, I was testing a new load, and it just so happened that there was a new bullet in this load, as well.

The first target I ever shot with the Ballard was shot with lead bullets just as they dropped from the bullet mold. They were sized 0.381 inches nominally and lubricated by my finger pressing grease into the grooves. The new bullets I was trying were the exact same bullet, but sized to 0.379″ and with the grease grooves filled by a machine. Let me show you what happened.

This is the first 100-yard group I shot with the Ballard rifle. I was just burning up the old 16-grain loads with the as-cast, finger-lubed bullets. I made two sight adjustments while this group was being shot! As casual as this group is, it’s clearly better than the second group made with the new ammo.

This was supposed to be the perfect 10-shot group. Here, I used the new bullets sized 0.379 inches and 18 grains of powder. The reason the bullet holes are smaller is because the bullets were moving faster — I guess! This is not a good group.

Obviously, I moved away from a good load and toward a bad one. The unsized bullets are better in this rifle than the sized bullets. The powder change may not have helped as I thought it would.

Back to pellet guns
This is what I mean when I say that your ammunition matters. Want to know what I shot with that “inaccurate” pellet gun? At 30 yards, I shot groups measuring .75 inches in a stiff wind. One four-shot group inside the five was .25 inches. I was using Crosman Premiers in the cardboard box. It made all the difference in the world. The message? Stop using discount-store pellets in precision airguns!

Today’s report
Back to the Air Arms S400 MPR FT. I’m also testing a Hawke 4.5-14×42 Sidewinder Tactical scope with illuminated reticle, on which I’ll give a separate report, and it was mounted on the S400 MPR. I tried light and heavy pellets. Because of the wind, the light pellets didn’t fare as well as the heavies. Just like picking the right pellet for the gun, picking the right pellet for wind conditions is very important for accuracy, as you’ll see.

Air Arms Falcon pellets
The first pellet I tried was the Air Arms Falcon. At 7.33 grains, this domed pellet is extremely light, and while it is often one of the most accurate pellets in a given rifle, the day was too breezy for it to hold up at distance. Remember, I’m shooting 10 shots at 50 yards, which is not easy with any pellet rifle!

The spread of these 10 Air Arms Falcon pellets is 2.191 inches at 50 yards. Clearly, the wind is too much for this pellet at long range.

JSB Match Diabolo Exact pellets
The next pellet I tried was the JSB Exact 8.4-grain domed pellet. It proved to handle the wind quite a lot better, posting three 10-shot groups of 1.221 inches, 1.374 inches and 1.699 inches.

The best of three targets shot with JSB 8.4-grain Exact domed pellets. It measures 1.221 inches.

Crosman Premier pellets
Next, it was time to try the 7.9-grain Crosman Premier domed pellet in the cardboard box. Remember my rant in the beginning of this report? Premiers that are not in the cardboard box are made on the same dies as those in the box, but they’re not sorted by die. Which means they will have a larger variation than the boxed pellets. Look at the results that two thousandths of an inch made in the Ballard rifle and understand that it does make a big difference what you load into your air rifle. Maybe for plinking at 25 yards you can get away with discount store pellets. For the ultimate in potential, you have to use the best pellets you can buy.

With the 7.9-grain Premiers, I shot two groups. They were 1.697 inches and 1.736 inches, which is pretty close. Not as good as the JSBs and not the pellet to choose for this rifle on a windy day.

You can see the lateral dispersion from the wind. Ten Crosman Premier 7.9-grain pellets at 50 yards. This was the better of two groups of lite Premiers.

The last straw — Beeman Kodiaks
Had I realized the wind would be such an issue, I would have brought more heavy pellets to test. I almost didn’t bring the tin of Beeman Kodiaks, but I threw them into the range bag because this is a PCP rifle that performs best with heavier pellets. Even at only 12 foot-pounds, the Kodiaks should have done fairly well.

Beeman Kodiak pellets shot the best group of the test. Ten pellets went into this group that measures 1.183 inches.

The bottom line
You’re used to seeing .75-inch groups at 50 yards, so these results may not impress you. Bear in mind that this is a 12 foot-pound rifle. So, the pellet stays out in the wind much longer than if it were going faster. A 20 mph wind is not a day for setting records at 50 yards with any air rifle. That much wind is hard on even a .22 long rifle bullet at 50 yards! So, these groups are actually pretty good for the conditions.

I’ll be reporting on the Hawke scope. But, I’ll tell you right now it’s a wonderful optical sight. A lot of what I was able to do on this challenging day was because I could easily bisect the center of the small bullseye at 50 yards.

There will be a complete report on the Hawke 4.5-14x42AO Sidewinder Tactical scope in the future, but from this test I can tell you it’s a winner!

I’ll also do another report on adjusting the power higher. Stay tuned for that.

Air Arms S400 MPR FT: Part 2

by B.B. Pelletier

Part 1

The Air Arms S400 MPR FT is a beautiful international-class field target rifle.

Today, we’ll look at the velocity of the Air Arms S400 MPR FT rifle. I’m testing the gun just as it was sent from the factory, which is how I would use it for field target. By looking at the large reservoir tube and knowing that this is a 12 foot-pound rifle, I knew it would get a lot of shots per fill, so today I concentrated on what the gun could do in factory trim.

Blog reader Coax has asked me to try to increase the power, to see what the potential of the rifle is. I’ll do that in a separate report because I don’t want to shortchange today’s lesson. And, a lesson it will be, because the unregulated MPR FT has the classic inverted bathtub curve of power as the air charge bleeds down. I want to talk about that, because it illustrates a couple of important points that new PCP owners need to understand.

Fill the rifle
So, the first thing I did was charge the rifle up to its 190 bar fill point. I used the gauge on my carbon fiber tank, because I’ve learned that it’s usually very accurate. Once the rifle was filled, however, the onboard manometer read less than 180 bar, so be aware that gauges seldom agree.

The Air Arms fill coupling, which I showed back in part 1, requires the rifle to be held in a certain position for the keyed coupler to stay attached. This almost always places the rifle at a most awkward angle during filling and this time was no exception. I wish Air Arms would change to the Foster quick-disconnect that Crosman, Daystate and Quackenbush now use, because that type of coupling allows for maximum positioning flexibility. However, I have to say that once it’s connected there’s no problem filling the rifle.

Velocity test
I want to accomplish several thing when performing the velocity test, and our newer PCP owners would do well to copy what I’m about to do. There are several things we want to learn from this test. First, we want to know the average velocity of several representative pellets. At this point, we don’t know what the most accurate pellet will be in the rifle, but that doesn’t matter. The way I’m doing the test, we’ll still learn everything we need to know; and all that can be transferred to the best pellet, once it’s discovered.

The first step is to fill the rifle to the recommended maximum fill. We’ll soon know whether that pressure, as indicated on our gauges, is correct, or if there are adjustments to be made.

The next thing we want to learn is how many shots there are on a fill. The way I run the test, we’ll be able to select a number of shots from a larger body of data after the test is complete. In other words, we don’t need to know anything going into the test. No preconceptions.

We’ll also note the ending pressure when the rifle falls off the performance curve. If this were a regulated rifle, we’d determine the reservoir pressure at the point when the rifle falls off the reg. That way you can grab the gun and look at the manometer to determine at any time if there are any good shots left in it. That’s handy when you just want to grab the gun for a few quick shots, like a squirrel in the bird feeder.

Crosman Premier 7.9-grain domes
I’ll use the 7.9-grain Crosman Premier domed pellet in the cardboard box as my test pellet for most of this test. I use the lite 7.9-grain pellet instead of the heavy 10.5-grain Crosman Premier because this is a 12 foot-pound rifle. I know that, legally, it has to shoot slower than 825 f.p.s. with this pellet. In fact, it has to shoot a lot slower than that, because the law in the UK says the rifle cannot produce over 12 foot-pounds with any pellet. And, PCPs are always more efficient with heavier pellets. Since the 7.9 is a light pellet, I know the velocity with this pellet has to stay well away from the maximum or risk going over the limit when a heavier pellet is loaded.

Crosman Premier lites averaged 764 f.p.s. in the rifle. Shot one was at 755 f.p.s., but the other nine were at or above 761 f.p.s., which demonstrates the need to “wake up” the valve in a PCP. Whenever I competed in field target, I always shot a couple valve wakeup rounds before starting the match. And, that was a regulated gun! This gun is unregulated, which makes the wake-up call even more important.

The range of the shots was from 755 to 771. That’s pretty broad and perhaps points to the gun being overfilled, but I’m getting ahead of myself. The average velocity produces 10.24 foot-pounds.

JSB Exact heavy domes
The next pellet I tried were JSB Exact domes that weigh 10.2 grains. They averaged 740 f.p.s. and had a much tighter range — 736 to 742 f.p.s. That tells me the rifle is becoming more stable as far as velocity is concerned. That fact will be important in a moment. At the average velocity, the muzzle energy is 12.41 foot-pounds. In the UK, that would be over the legal limit. You see what happens when a heavier pellet is used? That’s why PCPs shoot so slow with light pellets. Of course, they shoot even slower with heavy pellets, so pellet selection is a tricky thing. Of course, you want accuracy over everything else.

Air Arms Falcon
The Air Arms Falcon pellet weighs 7.33 grains, making it the lightest pellet in this test. It averaged 834 f.p.s., with a tight spread from 831 to 836. That’s just 5 f.p.s. — a solid indication that we’re on the power curve. At the average velocity, the muzzle energy is 11.32 foot-pounds, making this a very efficient lightweight pellet that’s certainly in contention as a best pellet for this rifle at this power level.

The next test
After testing these three pellets, I wanted to establish the maximum number of shots I can expect from a single fill. To learn that, I started shooting Premier lites at shot 31. Let me show you the remainder of the shots in this fill

36……..790 (manometer reads 150 bar)

At this point, I’m obviously at the top of the power curve and also at a very flat spot. I wanted to see how the other two pellets would do at this point in the fill/curve. Next, I shot two JSB Exact 10.2-grain domes.


Okay, they’re going even faster than the average we saw before. The string I shot with them was not on the optimum power curve. So, 190 bar indicated on my carbon fiber tank gauge is too high a fill for this rifle. I’ll try 185 bar next fill. Now, I’ll try some Air Arms falcon pellets.


Okay, the Falcons are exactly where they were when I shot the first string of them. For the total useful number of shots per fill, I’ll begin counting with the first string of falcon pellets. I’ll disregard the first two strings, because I now know the rifle was overfilled when I shot them. But the string of Falcons was right on the power curve. Do you see that? Let’s return to the Premier lites to establish the end of the power curve.

76……..771 (manometer reads 125 bar)

I stopped the test here. As a field target competitor, I feel good about the shots from 21 (the first of the Air Arms Falcon string) and shot 75. That gives me a useful string of 54 shots. If I use Crosman Premier lites, I’ll get 54 shots that range between 784 and 794 f.p.s. That’s a 10 foot-second velocity spread for 54 shots. What I would do is mark the place in the match when 50 shots had been fired and fill after that point when it’s convenient. If I were to use Air Arms Falcon pellets, my average velocity would be about 834 f.p.s. for the same 54 shots. My total spread might be well below 10 f.p.s.

Do you see where I’m getting this? All this I’ve learned from just one string of shots. And, that, my friends is why owning a chronograph is so important for a PCP shooter. Not to see how fast you can go, but to learn useful things about your airgun.

Next, I’ll attempt to adjust the power and give you the results of that.

Air Arms S400 MPR FT: Part 1

by B.B. Pelletier

Before we begin, there are a couple of items to be addressed. First, Edith and I noticed that several of our readers are fans of the Three Stooges, and we thought we would share this photo we had taken in Las Vegas, when Edith, Mac and I attended the 2008 SHOT Show.

Left to right — Tom, Edith, Mac. This was the most fun picture we ever took. It hangs in Edith’s office.

Now, there is a survey to re-name the Air Arms Twice air rifle, and with a name like that I can see why. Go here to select suggested names or submit one of your own.

Next, the blog discussion about muzzlebrakes and the lack of open sights on many Beeman guns has resulted in two reader surveys. Go here to comment on the R7 air rifle. Go here to comment on the R1, R9, HW97, RX-2 and R11 air rifles.

Now, let’s get started with today’s report. The Air Arms S400 MPR FT is a bolt-sction, single-shot .177 caliber rifle made for the sport of field target. It’s based on the S400 multi-purpose rifle (MPR) and comes with a walnut-stained poplar stock. The metal parts are highly polished and finished with a deep, dark black.

The Air Arms S400 MPR FT is an attractive field target rifle made for international power field target regulations of 12 ft-lbs.

Adjusting the stock to fit
The MPR platform is a 10-meter target rifle platform, so the stock configuration is set up accordingly. Fortunately, that same shape works well for field target, so it supports the intended purpose quite well. The only drawback is a rather short pull of 12-1/8 inches with the one butt spacer that comes installed by the factory. I installed the other three spacers, which extended the pull to 13-1/8 inches. While that’s still short for me, I found a workaround. I dropped the adjustable buttpad to its lowest position and lifted the cheekrest to its highest position. That gave me a comfortable fit in the offhand position.

The buttstock with all four spacers installed and the cheekrest up as high as it will go. The buttpad has been dropped as low as it will go. This combination fits me well.

The forearm has an accessory rail, which is perfect for fitting the knee rest that many field target competitors want. Next to the rail and deeply inset into the stock is a manometer or air pressure gauge, so you’ll always know the state of the charge in the air reservoir. That said, the S400 MPR FT operates on a maximum fill of 200 bar, or 2,900 psi.

Pistol grip
The pistol grip is shaped with a rounded knob at the top where I want to put my thumb. I do not like wrapping my thumb around a pistol grip and normally I would expect to find a dished-out spot for the thumb in the upright position, but there is none. There is no comfortable way to position the thumb on this rifle except to wrap it around. If it were my personal rifle, I would modify that with a Dremel tool. The grip is roughly stippled to grip your three fingers when you hold the rifle.

With the top of the pistol grip rounded like this, there’s no comfortable place to put my thumb. The grip is too thick for me to wrap around.

The trigger is adjustable for the location of the blade, for the length of the first stage, location of the second-stage break and for the overall pull weight. I was able to adjust it down to 14 oz., with just a tiny bit of creep in stage two. Then, I adjusted the creep out with the second-stage location adjustment. The only thing lacking is an overtravel adjustment.

Fill requirements
Air Arms has a proprietary filling adapter. Nothing else on the market will fit the rifle. Their adapter connects to a 1/8-inch BSPP female coupling, so that’s what you must have at the end of whatever filling setup you use — hand pump, scuba or carbon fiber tank. It’s a fairly standard connector these days and comes with a lot of pumps and scuba connectors.

The Air Arms fill port is unique. Nothing but an Air Arms adapter fits it.

Air Arms adapter to fill all their precharged airguns. The threads are 1/8 inch BSPP, which is pretty standard.

The S400 MPR FT is a 12 foot-pound rifle, which is perfect for competing in field target in the international class. Pyramyd Air lists the muzzle velocity at 800 f.p.s., but I’ll test a number of different pellets to determine the actual velocity of the test rifle.

No sights come with the rifle, because the assumption is that you’ll be scoping it. As a field target rifle, there really isn’t any other way to go. The aluminum receiver has an 11mm dovetail on both sides of the bolt trough. Because this is a PCP, there’s no recoil to worry about, so no scope stop is needed.

I plan to use this rifle as the test platform for a Hawke scope I’ve been wanting to test. The S400 should be accurate enough to give us a good idea of how well the scope works, so I’ll probably add another part to the report.

Overall observation
The S400 MPR FT rifle seems to be a nice lightweight field target rifle. Of course, a big scope will add some weight, but this will still be one of the lightest rifles on the line. I can’t wait to see how accurate it is.