Stripping my s/h 0.22 Remington Express Compact

[steveiep]

This afternoons fettling has now produced an air gun that cocks and shoots !

I made another top hat, this time with a 16mm long spigot instead of 5mm. The head thickness remained the same as the previous one and I cut 20mm off the rear spring guide

I decided to size the piston washer by putting the piston in the lathe and using 400 wet&dry with some light gun oil on it, not sure if that’s the right thing to do but it seems to have worked and although the piston still isn’t a ‘sliding down under gravity’ fit, it is easier to get in and out.

I also removed two of the spring washers from the trigger mech as suggested and it’s now a much lighter crisper let off

The cocking effort is still considerable, and I’m guessing the slightly tight piston and 5mm of preload isn’t helping, but I feel I’m progressing in the right direction

I put a couple of shots through using the Falcon AP pellets and then recorded 12 results on the chrono, early days I know but you need a starting point !

It was originally shooting around 10.8 - 11ftlbs ‘Dry’ with a few FAP’s I put through and I’m guessing the new tighter piston is reducing the power a little bit.
Am I right in thinking the power will go up a bit when the new piston seal wears in ? If so I might remove a coil from the spring to make cocking easier now, even after a dozen shots my elbows feeling it

Norm

594 - 10.5
601 - 10.7
592 - 10.5
595 - 10.5
601 - 10.7
592 - 10.5
583 - 10.1
580 - 10.1
592 - 10.4
583 - 10.1
587 - 10.2
591 - 10.4
588 - 10.3

The numbers look normal for a compact.
The full fat Express easily makes higher numbers.
It all depends what you want out of your springer
Pays yer money and takes yer choice

[Mr.Fixit-Norm]

The numbers look normal for a compact.
The full fat Express easily makes higher numbers.
It all depends what you want out of your springer
Pays yer money and takes yer choice

Hi, yes I did read the full length version was more than capable of 12ftlbs and the compact somewhat less. Amazingly it was nearer 11ftlbs before I stripped it and I think once the seal has worn in will probably be back around that. As you’ve probably deduced, I’m much more interested in getting it smoother and lighter to cock and hopefully as consistent/accurate as I can, rather than power.

It won’t be used for hunting as I have a couple of precharged guns that I find more suitable Having said that, both the Remy and the recently tweaked HW35k are more than capable of vermin control out to 35yrds

I’ll more than likely just use both guns ( along with my much fettled BAM DB4 ) for club and back garden shooting.

[Shed tuner]

heyup, don't be tempted to size the seal smaller. As mentioned, sized seals with initially wear in quickly, so if you size to perfection, it will quickly become too loose and harsh. Also, tighter seals generally shoot softer, looser the opposite. But as we know too tight robs power.

So just shoot 50-100 through it, let everything settle down, and rechrono it. Also try it with some 16 grain JSBs for comparison to the FAPs if you have any.

Finally, if it's too tough to cock, just reduce the spring a bit. Does it really matter (within reason) what power level it's at ?

HTH - JB

[Mr.Fixit-Norm]

heyup, don't be tempted to size the seal smaller. As mentioned, sized seals with initially wear in quickly, so if you size to perfection, it will quickly become too loose and harsh. Also, tighter seals generally shoot softer, looser the opposite. But as we know too tight robs power.

So just shoot 50-100 through it, let everything settle down, and rechrono it. Also try it with some 16 grain JSBs for comparison to the FAPs if you have any.

Finally, if it's too tough to cock, just reduce the spring a bit. Does it really matter (within reason) what power level it's at ?

HTH - JB

Thanks for that, my mantra exactly, the old Power is nothing without accuracy saying is very true. I’d be quite happy for it to settle around 10.5ftlbs
I’m definitely not resizing the seal anymore, but I may well remove one coil off the spring to ease the effort a bit.

Norm

[Mr.Fixit-Norm]

Quick update.

After putting around 100pellets through it since sizing the seal the power is only up a few ft/sec and the cocking effort doesn’t seem to have changed at all.
I decided this afternoon to remove one coil from the spring to see if that improved things. It did make the cocking effort noticeably easier but with the FAP pellets has reduced the power to an average of 9.7ftlbs

I should also say when I dismantled it the piston was still quite tight.

I only had time to put a dozen pellets through but was impressed with the consistency - 568-572ft/sec !!

I think once the seal has worn in it may well go up a bit but I was surprised at how much it dropped the power ? If it settles around 10.0 that’ll do or if cocking has improved even further I can always add some preload.

I did put a few Hobby’s and JSBs through but both gave an average of 9.2ftlbs so the FAP’s are obviously the optimum pellet

Norm

[CapitalBee]

This isn't plagiarism as I have taken this from Venoman's post on UKCAF from back in 2014 (so quoted my source). It concerns the Express Compact:

"Dont think this is a express with a carbine barrel, its based on the express but the cylinder is shorter. The stock is also shorter and the length of pull to the trigger. When you cock it the barrel stops at about 90deg, on the box it claims the power is 7ft lbs. I test fired three .22cal rifles , firing 12 shots to clear the oil the tested it on the chrono, all three rifles fired 10/10.25 ft lbs with Superdome and AirArms pellets. If this will drop time will tell, the gun looks like it aimed at the junior shooter , but i find you need more effort to cock it than the express."

Looks like spring compression / strength has been played with to overcome lack of swept volume (15mm shorter). This may be why the reduced spring is having a marked effect on power?

[Mr.Fixit-Norm]

This isn't plagiarism as I have taken this from Venoman's post on UKCAF from back in 2014 (so quoted my source). It concerns the Express Compact:

"Dont think this is a express with a carbine barrel, its based on the express but the cylinder is shorter. The stock is also shorter and the length of pull to the trigger. When you cock it the barrel stops at about 90deg, on the box it claims the power is 7ft lbs. I test fired three .22cal rifles , firing 12 shots to clear the oil the tested it on the chrono, all three rifles fired 10/10.25 ft lbs with Superdome and AirArms pellets. If this will drop time will tell, the gun looks like it aimed at the junior shooter , but i find you need more effort to cock it than the express."

Looks like spring compression / strength has been played with to overcome lack of swept volume (15mm shorter). This may be why the reduced spring is having a marked effect on power?

You could well be right. I was a bit surprised at an average drop of 20ft/sec but this could easily be rectified if I wanted. I think I’ll put maybe a tin of pellets through it and then see what it’s like. The piston is still quite stiff in the cylinder and as has been said earlier in the thread, a tight piston will reduce the power.
The cocking effort is more acceptable ( to me ) now so I won’t do anymore tweaking till it’s been run in further. Interesting to read that info though, thanks.

Norm

[evert]

I'd get a good seal fit before you start cutting the spring... That often means a lot of seal sizing and shooting, as someone mentioned earlier, its easy to go too far.
I like my seals to be a "medium" fit, so not so loose that pistons fall under their own weight. Never measured seal resistance, but a guesstimate would be about 0.5kg to push the piston.

[evert]

Looks like spring compression / strength has been played with to overcome lack of swept volume (15mm shorter). This may be why the reduced spring is having a marked effect on power?

What is the stroke length? This rifle is beginning to sound interesting...

[Shed tuner]

add a steel top hat around 15g. should give you back most of the power you lost with minimal cocking effort increase

[Mr.Fixit-Norm]

add a steel top hat around 15g. should give you back most of the power you lost with minimal cocking effort increase

Thanks, I’ll give that a try, a good excuse for more workshop time, although it’s going take me more time to make than the delrin one !

[Mr.Fixit-Norm]

What is the stroke length? This rifle is beginning to sound interesting...

That’s the one thing I didn’t think to measure, once I’ve made the steel top hat that Shedtuner suggested I’ll measure it

[Mr.Fixit-Norm]

I'd get a good seal fit before you start cutting the spring... That often means a lot of seal sizing and shooting, as someone mentioned earlier, its easy to go too far.
I like my seals to be a "medium" fit, so not so loose that pistons fall under their own weight. Never measured seal resistance, but a guesstimate would be about 0.5kg to push the piston.

That’s interesting evert, I wonder if there’s an optimum seal resistance ? If when I’ve got it apart I could push the piston back to its ‘at rest’ position, remove the spring, find a steel tube that fits over the piston rod then fit a plate to the top on which I could place weights. Weighing the tube and plate I can then mount the cylinder vertically in a clamp and start adding weights til the piston moves.

Might be an interesting experiment

[TonyL]

What is the stroke length? This rifle is beginning to sound interesting...

Wonder if anyone has the stroke length for the standard Express? I've never worked on one but, just from shooting them briefly, they would seem to be quite a sizeable beast with the ability to make plenty of power easily? Guessing more than generous stroke length? Therefore I'd have to have a guess that this smaller version, with its 15mm shorter stroke, shouldn't present too many problems?

I think it's the tightness of the seal (which, if not silly tight, I'd just allow to bed in) and I think that Jon's idea with the increased piston weight has much merit, increasing preload, momentum and sectional density.

Or, as power isn't high on the list of priorities, and if Norm's happy with the way it shoots / cocking effort etc., just shoot it, let it run in and enjoy?

[TonyL]

Quick update.

After putting around 100pellets through it since sizing the seal the power is only up a few ft/sec and the cocking effort doesn’t seem to have changed at all.
I decided this afternoon to remove one coil from the spring to see if that improved things. It did make the cocking effort noticeably easier but with the FAP pellets has reduced the power to an average of 9.7ftlbs

I should also say when I dismantled it the piston was still quite tight.

I only had time to put a dozen pellets through but was impressed with the consistency - 568-572ft/sec !!

I think once the seal has worn in it may well go up a bit but I was surprised at how much it dropped the power ? If it settles around 10.0 that’ll do or if cocking has improved even further I can always add some preload.

I did put a few Hobby’s and JSBs through but both gave an average of 9.2ftlbs so the FAP’s are obviously the optimum pellet

Norm

Er, just reading this again, Norm. The difference in velocity to achieve 10.0 from 9.7 will be almost negligible. And from a piston seal that may well be tight. I think I'd just leave alone.