I started with a quick chrony test of some 456 grain Lee mold slugs for the .50 cal, cast up by a friend here in Christchurch. That's them, in the middle, flanked by some 250 grainers cooked up by Jerry and his boys, and on the right 15.9 grain JSB Exacts:

They shot at around 560 fps, or 318 fpe, which I think is about the maximum useful weight/energy for this gun....
On Sunday afternoon I had a brief moment to shoot a few at 50 yards, just as the weather deteriorated and the air began to run out. I sprayed a few around, then settled a little and shot these 3, not impressive by any means but a work in progress:

One thing I noticed with such a heavy slug was the increase in recoil, which I will have to adapt to if I want to shoot straight!
I had hoped to test the BC of this slug and some others, but as Murphy's Law would have it, the battery on one of my chronys had gone flat, along with my air tank
The weekend wasn't completely wasted results-wise, although nearly so. Sunday morning, just after the frost melted, I set up the new bench and 100 yard target for some quiet small-bore shooting. I shot 5 very indifferent groups with unsorted unweighed pellets, in near calm but vexing conditions, and finally it came together for an only just sub MOA group on my last attempt:

This Falcon spoils me, as I expect to shoot sub MOA on every outing with it. My goal is a good solid sub 1/2 inch group, which will come one day I'm sure...
Getting anywhere near MOA with my big bores is my biggest challenge. Much work to do.

Regards from downunder

Neil

Great report Neil - thanks!

Recoil indeed. That big slug pushes you back.

You'll have to do the 9 shot test again for your 50 cal. Looks like you have vertical stringing ... which is correct if those were shoot from one fill. Good job. That can be overcome with your aim points per shot in the string.

Gary

Sadly, Gary, the gun was tethered for this "group". But I know where the problem lies, and it is me! I was shooting off an old, uncomfortable bench and was less than consistent with my procedure. I just have to become more clinical with my approach (and use my new bench), all the more so with this gun and these slugs, given the extra recoil. I hope to be able to post some progress towards better groups after next weekend...
Regards
Neil

Good shooting Neil! That's a nice group at 100'yards. As regarding the bigbore, a 2 inch group accuracy at 50 yards is sufficient for biggame hunting at that distance.

Thanks Peter
My goal at this point is to get 1'' at 50 yards, as a matter of pride and to lessen the margin of error when hunting
Cheers
Neil

I'm sure you'll get there. The neat thing about airguns is that the effort to find the best or most accurate slug/gun/fill/technique combination is an interesting pursuit in its own right. Buy a powder burner and you lose a lot of that unless you hand load. My guess is that you may find a great combination for 50 yards and another that works for 100. In any case, getting there will be a great time with lots of little victories to enjoy.

Thanks Jerry, I hope so! But my journey has now been lengthened by the entry of the dreaded hand-crafted Boyenga HP225. I am concious that it must not fail
And if it does, it'll be down to me not you

NOT the DREADED HP225!!!!! Say it ain't so!!!!! Oh MY!!!!

Ah ... What is it? Hollow Point 225 grain? You been Moonlighting Jerry? Casting OTHER molds? Dragging thru the gutter ....

Gary

Yes, dragging through the gutter and then laboring in the un-ventilated cavern to try to make the perfect slug out of a sow's ear...

I'm hoping that after the basic slugs are sighted in that the 225HP can be calibrated to a known hold-under/over and be useful on a hunting trip. Assuming that the slug is worth a hoot...experiments often are not but a lesson will be learned in any event.