2260 and 2560 HPAs Get LW Barrels

Back in the summer I got a couple of Lothar Walther barrels for my regulated HPAs.... They are 12mm OD, choked, 23.8" long, with conventional rifling.... I turned them down to 7/16" OD at the breech end, machined in chambers, leades and ports, and threaded the muzzles 1/2-20 NF to accept Hatsan air strippers which tension the barrel and also mount a 3/4" OD shroud.... These replaced a Crosman .22 cal barrel which was OK but not stellar, and a .25 ACP liner from TJ's which is going to be used for another project where I don't want a choke.... These two rifles are my varmint guns, and share a lot of features.... Here is a photo of what they now look like....

http://i378.photobucket.com/albums/o...ps371be138.jpg

Both rifles are regulated, using my own design of reversed tank block which mounts the tank under the 2260 air tube where it doubles as the forestock.... The tank blocks have a 3-slot Picatinny rail on the bottom and a barrel band, which I made larger to mount the shroud, on top.... They attach to the threads on the front of the 2260 tube.... The breeches are prototypes for a repeater breech I designed which never made it to production, and I have three of them, these two plus the one on my Grouse Gun.... They use MRod self-indexing magazines.... One of the features of this breech is a front mounting band which fits around the main tube and makes the assembly very rigid.... The guns have custom hammers with integral spring guides which double as a cocking indicator by protruding through the RVAs which I also made.... The stocks are walnut, made by Dennis Quackenbush, and intended for a QB but easily modified to fit the 2260.... I shortened and sanded them, and finished them with 7 coats of Watco Danish Oil, wet sanded with progressively finer grit, ending at 600 and then a coat of Dark Winwax.... Both rifles have Hawke 3-12 x 44 SF Varmint Side Focus Scopes with 1/2 MilDot reticles and extended sunshades....

After the new barrels were installed I checked the tune of both guns and set them up on the "knee" of the power curve, just below the plateau.... On both guns the plateau (ie maximum) velocity was 995-1000 fps, with the .22 cal using 18.1 gr. JSB Heavies and the .25 cal 25.4 gr. JSB Kings.... The tank on the .22 cal is a 13 CI, regulated at 1600 psi, and on the .25 cal I'm using a 17 CI tank regulated at 1900.... After tuning to the knee of the curve, the velocities were virtually identical, which is important because I want the two rifles to have the same trajectory so I can switch back and forth without having to relearn the holdover.... Both guns ended up with the ability to shoot 4 clips without the velocity dropping.... For the .22 cal that was 40 shots at 957 fps (36.8 FPE) and for the .25 cal it works out to 32 shots at 961 fps (52.1 FPE).... The .25 cal had only an 8 fps spread and the .22 cal had a 12 fps ES.... While running the strings through the Chrony I used only one target for each rifle, and here is the target for 40 shots with the .22 cal....

http://i378.photobucket.com/albums/o...pscfc0502e.jpg

The small squares at 0.1", and the .25 cal shot virtually the same, just a slightly larger hole from the bigger pellets for a 32 shot string.... The efficiencies are also nearly identical, 1.05 FPE/CI for the .22 cal and 1.02 FPE/CI for the .25 cal.... If I dial the velocity down to ~900 fps, that increases to about 1.20 FPE/CI, but these are my varmint hunters, and I really don't need more than 4 magazines on a tank as I take a tank with me for topping up if I'm going out for a whole day anyway....

This is one of those projects that got postponed over the summer but had to be done before varmint season rolls around next spring.... All that remains is to sight them in and go hunting in May.... The ground squirrels, crows, magpies and marmots better look out next year !!!

Bob