Air Arms FX liners in an AA S4/5xx

[BSJ]

I got the final parts for my FX liner in an Air Arms experimental project.

I had a breech end adapter made from brass for use on a FX liner.

In the middle is the adapter on a FX liner. It duplicates the dimensions on a current model OEM barrel and transfer port as seen in the bottom image.

My machinist didn't have a grooving tool small enough for the breech seal o-ring. So I had him use AA's 1990's version of the transfer port that they used back then. The 'cup' creates an o-ring groove by leaving a space for it when the two parts are assembled. Held together with loc-tite...

Here is what things will look like fully assembled.

AA uses an aluminum spacer inside the shroud at the muzzle end. As seen in the bottom image.

In the middle is a 600mm liner with custom spacers sized for the liner. I may just use one at the muzzle, or all of them.

On the top is a 700mm FX carbon fiber sleeve on a 600mm liner with a sleeve sized spacer at the muzzle end.

Will any of this bear fruit? Who knows. I've got four liners of various types to try. If I'm lucky they will at least match the potential of the LW OEM barrel. Fingers crossed that I can get some more velocity with the liner and improved accuracy.

With winter coming it may be awhile before I can know anything...

 

[HIll70]

I'm planning on getting one or two LW barrel blanks machined for my S510 over the winter. The barrel blanks have a bigger diameter (.63" as compared to .47") and are longer (around 24" as compared to "19) than the original, so I won't use the shroud. I'll be curious to compare notes. If your breach end adapter works as planned you should sell them. I'd be interested in one. Good luck with your testing!

BTW - I've done some extensive testing of the precision of my S510 XS over the past couple of months. Cleaning and polishing the barrel did not measurably improve precision.. Removing the shroud on the other hand had a big impact. The rifle looks out of proportion with the shroud removed and it is significantly louder, but precision improved by around 35% (as measured by average of the SDs from multiple 30 shot groups). When I removed the shrould the POA of the rifle shifted by roughly 4 MOA in both the horizontal and vertical, so the shroud was pulling the barrel out of true.