Adjusting Down the Power on the .177 Air Arms Shamal

They don't build them like this any more, or if they do it costs a mint.

Now i have a chronoscope i have been checking all my air rifles for power output, i also found it useful for diagnosing and confirming problems i thought i might of had. When it came to putting the Air Arms Shamal through it's paces i was very pleased with it's shot to shot velocity with very little FPS variation, and filling up to 185 bar started me at the best place in the power curve. The only thing that had me concerned was H&N field trophies would produce 11.9 ft/lb, therefor a heavier pellet could put me over the UK legal limit of 12 ft/lb.

Air Arms Shamal, the most accurate rifle i have come across to date.

When the Shamal was first introduced in 1989 it came with ability to adjust the tension on the hammer spring slightly, allowing your pellet of choice to perform just below the legal limit. However that wouldn't wash nowadays as the police will test your rifle with a variety of pellets, so i thought better play it safe and tune the Shamal down a tad. What follows is what i did to achieve this, if you own a Shamal use this information wisely.

The stock comes away from the gun by removing three screws with different heads, this has to be removed to get access to the adjustment port at the rear of the hammer spring. At the front is a hex head screw that connects to the support band, this also is used to attach slings and bipods. 

Front stud for sling and bipod.

 Further up is a flat head screw, this one connects to in front of the trigger below the action. It's best to use the widest head you can that fills the whole channel, ill fitting screwdrivers can damage the screwhead. You can get proper gunsmith screwdrivers but they cost a bomb, any decent multi head screwdriver set should have one wide enough. They have the advantage of having the blade head the same length as the diameter of the shaft, full contact with the head is a bonus in any situation.

Main bearing center flat head screw.

Next is a hex head screw which is accessed through a hole at the front of the trigger guard, this screw also connects the stock to the gun itself.

Tricky little hex screw through trigger guard and stock

Finally in order to remove the stock the whole trigger guard needs to be removed, there is a smaller star head screw at the rear of the trigger guard that secures it to the stock. 

Final star screw to remove trigger guard.

Unfortunately i did not have a star head of the right size but was able to use a hex head instead, though i wouldn't suggest using this method repeatedly and i don't intend to.

Trigger guard removed.

And gently lift the action out.

Now the gun will simply lift out of the stock giving full access to the plastic dust cover in the adjustment port at the rear of the spring and hammer housing, which i was able to prize out with my thumb nail instead of something thin like feeler gauges.

Not easily noticable but there is the dust cover.

First i had to remove a locking grub screw that has a hex head before i could get to the adjustment screw, which is also adjusted with a hex head but a tad smaller.

 

locking grub screw between action and dust cover.

Looking face on to the rear of the gun, turning the screw anti-clockwise releases tension on the hammer spring and only needs small adjustments to make a difference. 

Best picture i could get of the adjustment screw deep inside.

 I first turned it a 180 degrees and put a H&N over the chronoscope, this was too much as the muzzle velocity was reading 10.9 ft/lb. 

Make sure you turn it anti clockwise to reduce the power.

Turning the screw clockwise 90 degrees gave me the reading i wanted of 11.4 ft/lb which is pretty much the at top of the power curve, i would imagine this would now perform under 12 ft/lb with heavier pellets. 

11.51 ft/lb, nice and legal.

But as i don't use them apart from Crosman Premier heavies in the SMK multi pump i couldn't really test them, besides the Premier Heavies are a hard pellet and give less muzzle energy than the H&N's when used in the Shamal. The SMK multi pump can chew pellets with thin skirts, so likes the more solidly constructed pellet.

Now the Shamal was performing with a more pleasant muzzle velocity i fitted and tightened the locking grub screw then popped in the dust cover, fitting the stock was a matter of reversing the instructions for removal.

The Air Arms Shamal is an incredibly accurate single shot PCP air rifle which i use for excellent results when hunting, it would be really good if used in FT or HFT as i can hit the Knockdown target at 45 yards when using the correct breathing technique. This is i have to admit , my favorite air rifle in my collection and you wouldn't be able to pry it from my cold dead fingers. It's quite heavy at over 10 lbs with scope and lamp fitted, but it's built to an excellent standard and i find it easy to shoot as i can lug it around using the sling the rest of the time. I can sleep easy now , knowing my favorite air rifle is safe and legal.

TTFN

Wing Commander Sir Nigel Tetlington- Smythe. 

Testing the SMK B45-3 for Improvement.

Now the .177 SMK multi pump is up and running i find myself getting to really like it, and as it's a pretty light rifle i usually take it as a 2nd rifle when i go down the woods for practice. I know it's not the nicest looking rifle by a long shot, but once you get to know it;s many little faults you can compensate.

SMK multi pump as i like it.

It can come apart and be put back together in 20 minutes, so replacing things like inlet valve seals is no problem. Also the magazine works if you load and feed twisting it down and away from the loading port, though it still doesn't like some pellets all the same.

Start loading with red marker in this position so it lets me know when to stop when it reaches the barrel.

2nd pellet loads turning the magazine down and around, avoiding the ball bearing between the barrel and loading port.

Solid harder pellets like Crosmans work well, and the Premier heavies at 10.9 gr and only just fitting never fail. Air Arms diabolo's with their soft skirts deform easily, and H&N Field Trophies are a happy compramise.

When i tested the rifle with the chronoscope i discovered that after 8 pumps the power didn't go any higher, and that it stayed nicely within the UK legal limit of 12 ft/lb.

 

.177 pellets currently in favour.

At 8 pumps.

Crosman Premier Heavies   10.9gr         11.8 ft/lb

Air Arms Diabolo's               8.4gr         10.4 ft/lb

H&N Field Target Trophies  8.65gr         10.5 ft/lb

H&N Barracuda Power       10.19gr         10.8 ft/lb

It doesn't like wadcutters because the flat nose prevents them from loading well, so i didn't bother testing them at all. But on a string of 10 shots each there was no more than 12 FPS variation, and only 8 FPS variation with the Crosman Heavies. This was one of the reasons for being forgiving with this air rifle.

Pellet on the left has the tip worn, this is caused by the tight fit in the magazine.

But the main reason i like this rifle is that it is pretty accurate for what it is, and i can easily hit the hole in my field target rat at 35 to 40 yards. With it having an exhaust valve the trigger is fairly heavy on 8 pumps, but if i squeeze it at the tip it's a lot lighter. The trigger is also the sear and is pivoted at the corner of a rough L shape, remembering how levers work this could easily be redesigned to be lighter. The trigger blade even drops down through a fair bit of stock so there is room to design a trigger with a couple of sears in it, there are plenty of proven designs i could base this on.

Direct trigger and sear, fairly heavy pull at 8 pumps.

The elevation screw on the rear open sights had snapped off, but the two windage grub screws either side of the sight blade will still hold any adjustments made. 

Adjusting grub screws for windage, elevation is achieved by loading thin washers then tighten the grub screws.

 With open the sight's square notch and post it is accurate, however there is a small dove tail on the action for a scope. First i tried the generic 4x32 scope and was very pleased with the results, this only just fitted on as the rear open sight stops any further forward positioning. 

The 4x32 scope fits nicely and is easy to shoot with.

When i tried the AGS 3-9x40 i had to set it back a bit on the dovetails, but it still fitted and accuracy improved no end. 

The 3-9x40 AGS scope can't be moved forward because of the rear sight.

To make this better i would either need higher mounts, move or remove the rear open sights, or extend the shoulder stock by two inches.

This is the butt  being too short if i relax my neck when sighting with the AGS scope.

With a scope mounted on the multi pump i am limited in places to hold the rifle when operating the pump, i can do 8 pumps holding the stock at the rear of the action. Less tiring is supporting the rifle with the side of my palm on the rear sights, though this digs into my hand if i'm taking a lot of shots. If i could extend the pump arm in some way, pumping would be easier and i could support the rifle at the back of the action.

'Ee by gum', it's still a fun little air rifle though.

One way of sorting out most of these problems would be to make a new stock for it, this is something i have often thought about doing. It wouldn't have to be anything fancy, and this air rifle would make the perfect donor for a first attempt. The stock as it is at the moment is pretty naff so i'm sure i could improve upon it, after all i have plenty of bits and bobs in my shed for this project.

Looks like it's time for taking a shufty through the internet for some insperation, there's nothing like a good bit of pluagerism to achieve ones goals.

TTFN

Best wishes, Wing Commander Sir Nigel Tetlington -Smythe