HW80 calibre swap, initial findings (.22" to .25")

[averageplinker]

A while back I mentioned on the forum that I wanted to build/try a .25" HW80. There was a reasonable amount of interest in the results if I ever did it. So in the hope others might find my early results interesting...

Recently the pieces of the project came together when I picked up a 1987 .22" model to play with. My immediate job was to reduce the power as it tested hot it when I got it home. A quick swap to a secondhand short stroked set of internals quickly got me legal, in fact it was well down at just 8.6ftlbs using Accupell FT. Pay, who says HW80s are difficult to keep legal!

All I needed was a legal power plant to see the effect on power of simply swapping the barrel so the mid power starting point is not a problem for me.

Last night the 50cm .22" barrel was swapped for a 41cm .25" barrel and this morning I put it over the Chrono. Sadly I could not find my Diana .25" pellets (rebranded H&N I think) so had to use some older oxidising pylarm; yuk! The result? An increase in ftlbs of 0.7

I will now order some H&N .25" pellets and start to optimise the home tuners for a bit more FPS, then I will start some accuracy testing.
Rich.

[Zomboid]

Interesting. You'll probably need a stiffer spring with a short stroke but I would have thought the power was higher.

Look forward to more tests!

[averageplinker]

Interesting. You'll probably need a stiffer spring with a short stroke but I would have thought the power was higher.

Look forward to more tests!

The drop in power wasn't surprising. I had quickly stripped out all the internals it came with (including a square section spring) and put in a complete set of internals I had bought separately. I always thought the spring in that set up looked too short but have a couple of preload washers it came with to try before I use another spring. I don't expect to gain much more than 1ftlb with those (if that). I will wait for some better pellets before proceeding!

[robthedog]

Great thread !, i also picked up an 80 in 22 to do the same thing, mine is currently with a gunsmith for him to do the work.

Picked mine up in a trade with a local dealer, & was told it was doing 11.6, got it home to find it was doing 15.3 with its preferred pellet falcons. Took it straight back & they have posted it . Got a call from him today saying it was doing high 18's with bis mags, but its now in bits & the work begins, he's also going to cerakote it, as its going to be a working gun, & spend time in the van along with other machinery.

Rob

[darren m]

would I be able to put a .25 barrel on a .177 hw80 and would it work ???

[averageplinker]

[QUOTE=darren m;7431870]would I be able to put a .25 barrel on a .177 hw80 and would it work ???[/QUOTE

Yes you could. As always once swapped you would need to check the power and fettle as required to suit the new calibre and keep it below 12ftlbs. You may get very lucky and find it stays under 12ftlbs without tweeking but I suspect it won't.
Rich.

[Shed tuner]

only thing with .25 is it needs a bit of volume due to the pressure drop as the pellet moves along that large bore...

How short is your short stroke nose.. not that short I'm guessing, e.g. 10-15mm max ?

[averageplinker]

only thing with .25 is it needs a bit of volume due to the pressure drop as the pellet moves along that large bore...

How short is your short stroke nose.. not that short I'm guessing, e.g. 10-15mm max ?

It's a 12mm extension so I imagine there is still enough volume to run at 10.5 - 11ftlbs. The increase in power between the .22" and .25" barrels does not suggest it is running out of oomph in the big bore.

My other thought is that I should have popped a new seal on instead of the used one the second hand internals came with. Something to add to the shopping list!

[averageplinker]

By way of an update I now have some .25" H&N FTT so put 5 through the chrono. Interestingly they give the same power as the .22" set up.
I am surprised that they give lower power than the pylarm, but despite this they give a much better shot cycle. No doubt due to being far more consistent in weight and size compared to the pylarm!
Now where did I put those power washers????

[angrybear]

Pylarm are a lighter pellet than the FTT, 18.3gn v 20gn iirc, so should give a touch more velocity.

Hard to find but keep an eye out for Norica Apache .25 pellets they look like the old Mosquito/JSBrs at 18.8gn(ish) not on their web site so maybe discontinued which would be a shame.

[averageplinker]

I think our venerable sponsor used to carry a .25" norica pellet but not anymore.

Marksman .25" were reputed to go well in Hatsan big bore springers. I might track down a tin to try too.