Completely theoretical question on FAC air rifles....

[Dave]

If you were to drop an FAC rated spring into a standard sub 12ft/lbs PCP air rifle, would it work firstly, and what kind of power increase would you see?

Would it decrease the life expectancy of certain parts like the transfer port seal? Would you need to change any parts?

I ask as Im sure that FAC air rifle's must be built rather differently to non FAC air rifles?

All theoretical of course.

 

[sunndog]

Varies from rifle to rifle but certainly just putting stiffer hammer springs or packing out with washers and such does work
How much of an increase is totally rifle dependant but just a stiffer spring will probably gain you a couple of ft/lbs or so......theoretically

Most run of the mill fac rifles are simply modified 12ft/lb'ers.....if not de-tuned to sub 12 in the first place

 

[rorymax]

So many variables, sorry, but you need to be specific at least about the gun you might 'modify'.

I've played about with many airgun 'improvements', results can vary from very disappointing to very good, in the most part I have found it trial and error.

Easiest way is to seek out what other people have done with a particular gun (assuming you can rely on the claims made).

In short, yes, substantial gains can be made, you do need to enjoy the journey though .

rorymax

 

[mick91]

As adam said it is indeed possible (albeit illegal) to mod sub 12s into FAC. The old school theobens like the first gen rapids where easy to knock well over the top and where, as you can imagine, modified by theoben in later models to make them (while not impossible) very difficult and impractical to turn up. It was also possible to turn up gas ram airguns, notably again theoben, HW80s and an incarnation of the BSA lightning to be well over the limit. As gas rams did specify .177 and .22. All people did was chuck a .177 in a .22, the added power needed to give you the velocity for 11+ ftlb in the .177 variants didn't spit out the heavier .22 with much less velocity so knocked the power over the top. Putting some of the old ox mainspring kits into rifles they where not strictly speaking designed for reputedly did it too, HW97 kit in an HW77 I believe supposedly did it. In thruth though there's little point, if you want a meaningful power increase you're missing 1 ingredient, nitro!

Before anyone pulls it up I'm aware of the Benjamin rogue on power that's not the point!

 

[sunndog]

the old ox mainspring kits

My best mate's dads brother had a rifle with an ox spring in it....it would go all the way through a garage door, the car parked inside the garage, and a phone book lent against the back wall




There are air rifles with powder burner power levels though, they shoot water buffalo and all sorts with em

 

[mick91]

My best mate's dads brother had a rifle with an ox spring in it....it would go all the way through a garage door, the car parked inside the garage, and a phone book lent against the back wall




There are air rifles with powder burner power levels though, they shoot water buffalo and all sorts with em

Haha. He should have put a squirt of WD40 down inside the piston too, I hear that have artillery levels of power and in no way knackered your piston head! Ah the tall claims of springers!
Aye I've seen some of them when they take .357 and .308 boat tails. Seem a tad overkill for knocking the odd feral pigeon over though eh!

 

[sunndog]

Quackenbush.....just remembered it, insane and rather pointless levels of power for an air rifle

Rimfire power levels are getting pretty common nowadays though. Even 30 cal don't raise too many eyebrows these days

 

[nuggets]

irate:

 

[nuggets]

.irate:

 

[Dave]

So many variables, sorry, but you need to be specific at least about the gun

Air arms s400 carbine

 

[techworm]

Air arms s400 carbine

you would need to open up the transfer port to see the real benefit of stronger hammer spring

 

[adestu]

The pre anti tamper aa s410 had an adjustment screw which when wound right in gave just under the legal limit. With it wound out i could get a hypothetical 18ftlbs.
With more tweeking of firing pot sleeve it could go more.all that on the standard hammer and firing pot spring.

 

[stonepark]

For cheapness, most manufacturers use the same parts whether fac or sub 12, usually just one or two small differences, i.e. hammer spring in pcp, main spring in springer, occasionally transfer port etc. Most modern guns are designed for all markets (i.e. FAC) and are de-tuned where required to meet local restrictions.

 

[adestu]

One difference is that some fac versions do have side lever cocking including the fac air arms s410 and 510.its to make compressing the heavier hammer spring easier.
Weirach would regularly send rifles over that were fac out of the box and hull cartridge would hack off the mainspring on many a hw80

 

[Keithlard]

I don't see the point. If it's over 12 ft lb it's FAC anyway, so you may as well just buy an FAC air rifle.