Ok, finally got to testing the .25 slugs that Jerry sent me, what is it, 3-4 mths ago??!!
Previous attempts were thwarted by various things, most serious of all being a bent breech section on the barrel!!
Battery on my expensive camera had once again failed so pictures to follow..

30 yrds. Good groups of about 1.5inch.
40 yrds. Grouping at about 2.0 inch.
75 yards. grouping 3.5 inch (cherry picked this one!) 4.5 inch more normal.
I can shoot 31 grain Kodiaks at 1100fps for 83fpe but the 6 ring slugs won't go any faster than around 700fps for 61fpe ??!!
I've come to the conclusion that my polygonal barrel must be choked slightly more than normal, or more likely I asked for a size too big. IIRC they were sized to .252 whereas .251 would be better.
I shot a few through some thick yellow pages(phone directory) and the channel they produce is unbelievable!! Left a hole I could poke my finger right into and you would think that it was done by a centre punch the hole was that clean!! Expansion is very impressive, as is stabillity given their lengh over width.

Conclusion. Very good slugs, that I would buy again if I was in the US. Some of my shooting buddies at the club were also very impressed, though they now only shoot .177 (its the 'in thing' again here )
Would most definately recommend these Surefire slugs to anyone who hasn't tried them yet, just wish they shot better( faster) from my barrel.

Pab.

Hi Paul,

As I pick myself up I can't but wonder if the gun is the same as it was before. Is it still shooting Kodiaks at 1100? Something sounds off here. I don't know that anyone else with a LW polygonal barrel has tried these but the power numbers you're getting are a first. Even if .252 is .001 too big, the numbers just aren't right.

Hi Jerry. Yup, gun is as before!! Kodiaks doing 1100 fps. And to be quite honest, the slugs feel real good when you put them in. Nice and tight, but not too tight if you get my drift. I've read elsewhere that people are using a thumb protector to get these slugs into the breech because they are that tight. Could be that mine are not big enough, and not utilising the air well?
Seems to me that my rifle is the only anomaly out there, so for sure it would seem the problem is my rifle and not the slugs.

Ho hum, never mind. I've got a fox that still eludes me at the momment, and my hide should put me about 35-45 yards when he does show up. I have the slugs ready for just that occasion

I really don't understand the velocity / energy issue here. I suppose there could be some impact from the size for the Poly barrel but my gut tells me that alone isn't the problem. If your barrel has a deeper choke, a bigger slug would likely not help...

The guy who reported using the coin as a thumb protector was also loading a 9 ring slug which is considerably longer.

Jerry,
I suppose choke can be the only issue here .
I can't see the rifling as being an issue as the poly' rifling should have considerable less grip than a standard, if anything it should be a bonus.
As I say mate, very happy with them for shorter range
Its an issue with my barrel. Sucks though

Pablo,

I think the issue is the fact that your barrel is not "chambered". Meaning there's a place for the slug to be loaded in the breech, that does not require forcing it into the rifling. The air blast then engages the rifling. The fact that it's not engaged before firing, means more pressure can build behind it before it starts to move down the barrel. Think of the O ring seat in spring guns. They hold the pellet and the skirt is NOT already compressed into the barrel. You WANT breech pressure to build before the slug moves. I think your heavy slugs (being engraved already) are starting to move the nanosecond the valve opens. Thus, killing the effect of "popping the cork".

Gary

Solution is to ream out the breech, to the depth of the slug (at the major diameter of the slug). Hand reamer - hand turned.

Gary

A thought just occured to me (please no don't be scared, it happens from time to time)... How long is your barrel? I have had one other instance where a short barrel would not build up the velocity for the heavy slugs yet would still get the light Kodiaks up in the 50 FPE range.

Jerry,
When I first fired a few a couple months ago, the barrel was 24" The slugs were doing around 760fps. This time round, having had the breech section of the barrel redone, I lost just shy of 3" which saw around 700 fps.
Gary,
I seem to be the only one with this problem,though I think out of the guys on TAG forum, I may be the only one with a poly' . I see what your saying about engaging the rifling, but when I look down the barrel, the rifling effect is almost nonexsistant.

Appreciating your input guys

Paul,

I'm still noodling around what might be causing the low velocity issue. When we chrono tested these slugs out of one of Gary's guns which was attached to a regulator for the test, here's what we got:

Diana Magnum, 20gr, 1289 FPS, 73.8 FPE
Kodiak, 30.7gr, 1144 FPS, 89.2 FPE
Crow Magnum, 26.2gr, 1203 FPS, 84.2 FPE
Barnes 6 ring, 57.6gr, 922.1 FPS, 108.8 FPE (22% higher than the Kodiak)
7 ring, 66.9gr, 893.5 FPS, 118.6 FPE
8 ring, 72.9gr, 861.6 FPS, 120.2 FPE
9 ring, 84.6gr, 816.8 FPS, 125.4 FPE Avg. (the highest measured was 822.8 FPS and 127.2 FPE at the standard set-up)

The Kodiak velocity is within spitting distance of what your gun does and that's pretty stout. My calculations indicate you should be shooting the 6 ring slugs at 887 FPS without any change to set-up from the 1100 FPS Kodiak set-up. I'm sure the 21" barrle might reduce that a bit for the slower to accelerate slugs but your initial velocity with the 6 ring slugs was low too. I'm starting to wonder about the choke.

That Poly barrel has to squeeze the slugs "out of round" into the Poly shape - might be alot easier to so so with the flimsy skirt of a pellet, than the solid rings of the slug. I think the culprit is the Poly barrel.

Gary

barnespneumatic Wrote:
-------------------------------------------------------
> That Poly barrel has to squeeze the slugs "out of
> round" into the Poly shape - might be alot easier
> to so so with the flimsy skirt of a pellet, than
> the solid rings of the slug. I think the culprit
> is the Poly barrel.
>
> Gary
Hmmm, now theres a whole new take on the situation!! Could even be a combination of the two. Though I did some more test shots today and the tightest fitting slug seemed to fire the fastest. I've adjusted the tophat,spring and spacers(we don't have a power wheel over here) and am now seeing around 780.

Well, that's a big improvement. And, if the tightest slug is moving the fastest, then you've raised your breech pressure, as described earlier. Sounds like you have a workable combination there.

Gary