Air Rifle Modification advice sought

Heres something I know little about so I am hoping my friends on this forum can advise me.
I bought today an SMK XS 78 .22 air rifle that is powered by twin CO" gas bottles. Its a full length fixed v=batrrel air rifle that operates via a bolt action mechanism

www.sportsmk.co.uk...

It has a barrel length of 21.5 inches which for my own use is a tad two long. I prefer Carbines.
So I was wondering if it was feasable to shorten the barrel , there is no legal issues involved, if it is feasable by how much could I sensibly shorten it without losing to much power. and finally what is the best way to shorten it as I am guessing that just taking a hacksaw to it is not very wise.

Can you good people assist me please?
NR

I brought in my house-guest on this one. In no way is he an expert but...

He says shortening the barrel will not affect the power as the gas pressure is behind the projectile.

It will affect the accuracy and the sights etc will have to be re-calibrated.

A hack saw is perfectly acceptable, just ream out any burring with a small file. Better still find an engineering workshop that can cut at low speed. Any use of angle grinder etc may heat and warp the barrel and that is an obvious no-no.

Like I said, I don't know if that's useful, but that's his tuppence.

reply to post by Northern Raider

I have not worked with air rifles a lot but this may be of use. A .22 long rifle rim fire shows little or no gain in velocity from a 18 inch to a 22 inch barrel and more than 22 inches may have a reduction in velocity due to the pressure dropping in the bore to a point that it does not overcome the added friction of the additional inches of barrel. The air rifle will be working with less pressure but more volume so you will have a longer, flatter pressure curve so it may not hold true in the case of an air rifle. Sorry that I am not of more help.

Raider,

I have a chinese made type 34 spring piston rifle that has recieved this treatment. A dremel tool or hacksaw works fine for this. As was mentioned you need to re-"crown" the muzzle end so your projectile does not encounter any burrs left by the operation. I used the hacksaw method,
then sand the tool marks out, followed by lightly countersinking the bore with a drill bit that was substantially larger than the bore. I wrapped the bit in tape to build up a grip, and performed this by hand. At typical air rifle ranges (25 meters) the accuracy was unaffected. You could also put some buffing compound on a cleaning patch and just work it in the end of the muzzle, NOT the entire barrel. That should nearly restore the factory bore at the muzzle, but as always, go slowly so as not to overdo it.

Any thoughts on why you chose this particular weapon? I prefer spring piston rifles, So as not to be stuck having to stock cartridges. If I were to go with a compressed gas setup, I would probably get an AirForce Talon or similar type that uses paintball type bottles, for many multiple high-powered shots.

linky



[edit on 29-3-2009 by hotrodturbo7]

I have shortened two air rifle barrels in the past and it can make a difference if you shorten it to much, to put it another way, if you get a co2 powered pistol and lengthen the barrel you will get a significant boost to the power it produces.

If you shorten a rifle barrel to much the pellet will leave the barrel before all the air has built up the right pressure, the pellet will be gone and air will be wasted.

Check the rifle does not have a slight choke at the very end of the barrel, if it does then it's best to leave well alone.

Hope this helps.


[edit on 29-3-2009 by jon1]

Originally posted by hotrodturbo7
Raider,

I have a chinese made type 34 spring piston rifle that has recieved this treatment. A dremel tool or hacksaw works fine for this. As was mentioned you need to re-"crown" the muzzle end so your projectile does not encounter any burrs left by the operation. I used the hacksaw method,
then sand the tool marks out, followed by lightly countersinking the bore with a drill bit that was substantially larger than the bore. I wrapped the bit in tape to build up a grip, and performed this by hand. At typical air rifle ranges (25 meters) the accuracy was unaffected. You could also put some buffing compound on a cleaning patch and just work it in the end of the muzzle, NOT the entire barrel. That should nearly restore the factory bore at the muzzle, but as always, go slowly so as not to overdo it.

Any thoughts on why you chose this particular weapon? I prefer spring piston rifles, So as not to be stuck having to stock cartridges. If I were to go with a compressed gas setup, I would probably get an AirForce Talon or similar type that uses paintball type bottles, for many multiple high-powered shots.

linky



[edit on 29-3-2009 by hotrodturbo7]

I bought the XS78 as a comprimise, the other day I bought a BSA Lightening carbine for myself, but its just a touch heavy for my son at the moment. I saw the SMK XS 78 on offer at £89 in a magazine and thought it worth looking into in more detail. I found one for sale in Whitley Bay at £99 and went and had a look. Now I normally turn my nose up at most things chinese but this time I struggled to find fault. The only thing I did not like was the cheap tacky rear iron sight which no bugger uses these days anyway. Even if I wanted open sites I would go for a red dot or diaopter . . The Stock is beech, beutifully simple and smoothly finished the vast majority of the gun is blued steel unlike the Crossman Ratcatcher which is half plastic. It uses 2 x CO2 bottles in tandem to give around 10.5 to 11 ft pounds. According to air Rifle forums this can easily be modded up as far as 18 ft pounds. Its light easily pointable, very suiotable for gals and youths as well as adults. Just checked on E bay and found a Multi Shot conversion kit to fit it with a 10 shot mag, A muzzle break silencer adaptor is also available. Apparently is an almost 100% copy of the Crossman 160. I think the barrel could be seeriously shortened to make it a superb carbine or pistol. One mod I am already going to do is to change the standard fitment barrel support for an aftermarket one. the barrel support is about the only bit on the gun made of plastic and asccording to forums its weak and vulnerable. A chap on Ebay does Brass or Aluminium replacements for 16 quid. At 25 Yards straight out of the box it does 3/4 inch groups so its a useful tool. For what it cost its going to be a gun trainer gun for my son and a good back up for me. when he progresses onto something bigger in time I will possibly use it for experimentation.

Could the CO2 fill fitting added to the next model up for the larger tank take a charge from a scuba tank or pump?

It would mean that you weren't dependant on single-use sparkler bulbs...and sods law says that you'll run out of them when you need them most!

Originally posted by citizen smith
Could the CO2 fill fitting added to the next model up for the larger tank take a charge from a scuba tank or pump?

It would mean that you weren't dependant on single-use sparkler bulbs...and sods law says that you'll run out of them when you need them most!

Not sure, looking at some of the forums some folks have modded both the Crossman 160 and the XS 78 into usding dive bi=ottles in some way or form. the XS 79 uses the much larger 88cm CO2 bottles anyway which makes it more useful. I think someone commented about a certain size bottle being suitable for modifying and fitting.

The PCP (pre-charged pneumatic) set uses scuba tanks for fills. If you could mod up some type of reservoir in the stock that would be the cat's ass if it shoots that well. My type 34 only does about 1" average at 25 yards.

The type 79 available here for 90$ (63 gbp). Says that it will use up to 2" dia. (50mm) paintball tanks or the large crosman cylinders. Methinks one will be in the post for me monday!!!
www.archerairguns.com...

[edit on 29-3-2009 by hotrodturbo7]

Originally posted by hotrodturbo7
The PCP (pre-charged pneumatic) set uses scuba tanks for fills. If you could mod up some type of reservoir in the stock that would be the cat's ass if it shoots that well. My type 34 only does about 1" average at 25 yards.

The type 79 available here for 90$ (63 gbp). Says that it will use up to 2" dia. (50mm) paintball tanks or the large crosman cylinders. Methinks one will be in the post for me monday!!!
www.archerairguns.com...

[edit on 29-3-2009 by hotrodturbo7]

You should see the upgrades and customised modifications you can do to both the 78 and 79, just do a google on modifying a SMK XS 79, I have already ordered some bits. From what I found out scanning the web what happemned was the Chinese wanted to make a rifle of their own and decided to start with the discontinued Crossman 160. They bought the rights and asked around to find out what shortcomings crossman owners thought the original gun had. then they fixed them, wider trigger, more shots per refill, scope rails, lighter stock etc. So they now produce this gun without many of its faults, and they are seliing them fairly cheap. The Aftermarket Customisers love them, some folks are getting 18 plus ft pounds out of them.

[edit on 30-3-2009 by Northern Raider]

Err i think posting a warning here would be a good idea. If you do not have a firearms license and are modifying any air rifle to fire at over 12ft/lbs then you are essentially breaking the law and this is against the rules on ATS. If you are going beyond this power i would stop discussing it here, i hate to be a kill joy but it wouldn't be fair discussing such things here.

Also shortening the barrel length won't do much other than effect your accuracy and if you shorten it to much you will again be breaking the law as it may be classed as a pistol and then any power over 6ft/lbs would be illegal.

A 18ft/lb rifle most definitely needs a firearms certificate in the UK, i assume you are in the UK from how you speak. I could be wrong and if so i apologise.

[edit on 30-3-2009 by ImaginaryReality1984]

reply to post by ImaginaryReality1984


Would those same restrictions apply to such things as homemade pneumatic spud cannons too?

NR and other UK shooters,

Given your climate, the QB-79 in .22 with a high pressure air tank aka pcp is the way to go.
If you use a standard 13 or 22 cubic inch paint ball tank with it's 850 psi regulator, it should keep you below the 12FPE FAC limit. I use the 13ci tanks since there lighter. I would not shorten the barrel any shorter than 14 inches for a carbine.

Don't be too alarmed by some of the QB's barrel concenticity issues, I built a Mare's leg style pistol from one of my QB-79's. The barrel was cut to 12" for air pistol silhouette and US pistol field target. It fires 14 grain pellets at about 570 fps. The barrel is visibly off center but as long as the muzzle is properly crowned, the Chinese barrels will shoot as well as just about anyone can shoot. I can shoot sub 3/4" groups at 25 yards with it from the seated field target position with it

For hunting game under 30 yards, it's hard to beat RWS Hobby pellets, Crosman Premiers and JSB Exact Express and Jumbos also shoot extremely well. If you can find a 5.50-5.52 pellet sizer, .22 Eley Wasps will shoot very well in them,too. Chinese barrels are a tad tight and the 5.6mm Wasps are a bear to load.

Molylube does wonder for the trigger.

Originally posted by crgintx
NR and other UK shooters,

Given your climate, the QB-79 in .22 with a high pressure air tank aka pcp is the way to go.
If you use a standard 13 or 22 cubic inch paint ball tank with it's 850 psi regulator, it should keep you below the 12FPE FAC limit. I use the 13ci tanks since there lighter. I would not shorten the barrel any shorter than 14 inches for a carbine.

Don't be too alarmed by some of the QB's barrel concenticity issues, I built a Mare's leg style pistol from one of my QB-79's. The barrel was cut to 12" for air pistol silhouette and US pistol field target. It fires 14 grain pellets at about 570 fps. The barrel is visibly off center but as long as the muzzle is properly crowned, the Chinese barrels will shoot as well as just about anyone can shoot. I can shoot sub 3/4" groups at 25 yards with it from the seated field target position with it

For hunting game under 30 yards, it's hard to beat RWS Hobby pellets, Crosman Premiers and JSB Exact Express and Jumbos also shoot extremely well. If you can find a 5.50-5.52 pellet sizer, .22 Eley Wasps will shoot very well in them,too. Chinese barrels are a tad tight and the 5.6mm Wasps are a bear to load.

Molylube does wonder for the trigger.

Three points spring to mind ( Spring geddit )

(1)I have read about a convertter for the 78 to allow PCP bottles to be fitted, one is called the MaxZbulk CO2 Adaptor, the other is a Stephen Archer Bulk CO2 adaptor which converts the 78 into a more useful gun, trouble is I cant find who sells them.

(2) Ref the pistol with the off centre barrel I wondered if you knew about the replacement barrel band guide available on E bay, It replaces the nasty plastic one with one made from aluminium or Brass, apparently its rather neat at holding the barrel in the right place.

(3) I also saw on the web an after maket upgrade designed to fit a circular 10 round magazine to the 78 that auto feeds the pellet into the breech when the bolt is worked.
Respects
NR



[edit on 31-3-2009 by Northern Raider]

Originally posted by ImaginaryReality1984
Err i think posting a warning here would be a good idea. If you do not have a firearms license and are modifying any air rifle to fire at over 12ft/lbs then you are essentially breaking the law and this is against the rules on ATS. If you are going beyond this power i would stop discussing it here, i hate to be a kill joy but it wouldn't be fair discussing such things here.

Also shortening the barrel length won't do much other than effect your accuracy and if you shorten it to much you will again be breaking the law as it may be classed as a pistol and then any power over 6ft/lbs would be illegal.

A 18ft/lb rifle most definitely needs a firearms certificate in the UK, i assume you are in the UK from how you speak. I could be wrong and if so i apologise.

[edit on 30-3-2009 by ImaginaryReality1984]

Yes those are good wise facts, I certainly wont break any laws intentionally I prefer to work within the rules as it makes life easier.
NR

[edit on 31-3-2009 by Northern Raider]

Originally posted by ImaginaryReality1984
Err i think posting a warning here would be a good idea. If you do not have a firearms license and are modifying any air rifle to fire at over 12ft/lbs then you are essentially breaking the law and this is against the rules on ATS. If you are going beyond this power i would stop discussing it here, i hate to be a kill joy but it wouldn't be fair discussing such things here.

Also shortening the barrel length won't do much other than effect your accuracy and if you shorten it to much you will again be breaking the law as it may be classed as a pistol and then any power over 6ft/lbs would be illegal.

A 18ft/lb rifle most definitely needs a firearms certificate in the UK, i assume you are in the UK from how you speak. I could be wrong and if so i apologise.

[edit on 30-3-2009 by ImaginaryReality1984]

Good points, but we are just generalising, its often very confusing when people from different countries debate guns as the different rules can cause problems.

Originally posted by Northern Raider
Three points spring to mind ( Spring geddit )

(1)I have read about a convertter for the 78 to allow PCP bottles to be fitted, one is called the MaxZbulk CO2 Adaptor, the other is a Stephen Archer Bulk CO2 adaptor which converts the 78 into a more useful gun, trouble is I cant find who sells them.

Be careful with these kits, they are usually used by people who know what they're doing. You can hook one up with the cylinder empty for safety however when using it i have heard they are prone to failure, which isn't really something you want. If you were to get it modified, and had a FAC then i'd suggest sending it to a proper air gun dealer to do it.

Originally posted by Northern Raider

(3) I also saw on the web an after maket upgrade designed to fit a circular 10 round magazine to the 78 that auto feeds the pellet into the breech when the bolt is worked.
Respects
NR

Yeah those devices do work, however they can jaw, sometimes don't feed, can be cumbersome to load etc. The only good one i've found is the one air arms made for their rifles.

reply to post by Northern Raider


Mate just to reiterate ImagineReality's point:

Be very, very careful that you stay within the legal limits. The law is an ass when it comes to accidental infringement- they wont accept a lack of knowledge as defence, and may well slap you with a mandatory 5 year prison sentence (because catching you with a slightly overpowered air rifle is a damn sight easier than catching the armed yardie in brixton).

As for the modifications, I'm not sure I would bother. Is there any particular reason you want to reduce the length? The chinese rifles usually come apart quite easily (I mean in a good way) when you remove the screws, so if you intend on a compact package for carrying around with you when camping etc... then disassembly might be the way to go.

If not, then perhaps find someone to swap rifles with? Im sure the longer barrel version must be costlier than the carbine- you might find someone who doesn't mind a switch. I envy the fact that you have a 22inch barrel (man that sounds wrong...), mine is a beastly 26inches- nightmare to keep steady when shooting in anything other than prone.

I'd set your rifle as close to 12ft/lbs as you can get it. Make sure to test it with multiple kids of pellets. The reason for this is that some pellets are faster than others and the police will test them all looking for one that goes over the legal limit. As 44soulslayer said, that's 5 years in prison, lovely. A 12ft/lb rifle is plenty of power for hunting birds of all kinds, rabbits, squirrels and plenty of rodents. If hunting rabbits i suggest the head shot as a body shot with a 12ft/lb rifle isn't always perfect and i've had rabbits run a full 20 feet before falling down even though i've hit the heart and lungs.

However if you're building this for a sort of SitX scenario i would say this. Buy a more powerful spring but don't install it. If SitX hits you can install the spring and bingo you have a very powerful rifle. Afterall laws would be obsolete in such a scenario. I would stay away from compressed air because you will find it hard getting a hold of compressed air if anything bad happens and the pumps you can get are a large thing to lug around.

So there you go, that's my suggestion, it's legal to have the spring as long as it's not installed. Be careful though, installing them can be an absolute pig sometimes. I like the gas ram types.

IMHO The UK's 12FPE energy limit is just plain daft. It should have been set at 850-900 fps for all calibers below .25. The British airgun industry shot themselves in the foot with that one.

This is me making a rare political statement: arms control doesn't work. It didn't during Robin Hood's time , fuedal Japan or during occupied Europe during WW2. It certainly isn't working too well in the UK from all reports I've heard since leaving in '96. GB's violent crime rate has had a dramatic rise and from what I understand it's easier and cheaper now to get an illegal handgun than it was to get a legal handgun before the ban. Same with ammo. When I lived there from 94-96, the policemen I met all told me that they feared knives far more than guns because 90% of their violent confrontations were in very close quarters with drunken pub patrons where trying draw a gun was an exercise in stupidity. Until folks in the UK and Europe realize that the police and gov't can't defend the rights of every individual citizen 24/7 will they throw off the yolk of civil oppression that they currently live under. All the surveillance cameras in the world haven't prevented one assault yet. In the states with strict gun control laws( NY, California and Illinois), their violent crime rates are higher than states like Texas, Arizona and Florida where law abiding citizens can carry concealed weapons to defend life, limb and property.

Along time ago, one of your more notable social commentators said it best: An armed society is a polite society.