Set-back

 How much shot can a woodchuck chuck?  Or, in less poetic terms, how far over the top of a wad can steel shot sit without causing problems?

When I first started reloading, all the books made a point of emphasizing the importance of making sure the steel shot was inside the wad of the loaded shell.  Steel being so much harder than lead, we have to be extra sure to keep it away from the barrel--otherwise, we'll end up with scoring or gouging.  Then I was given some pressure tested load data by some dude on the interwebs which used LBC43 and CSD118 for 1.25 oz of steel shot.  I was skeptical at first since, as is implied by "118", both wads are described as being designed for 1.125 oz.  My skepticism was soothed by finding that Kent used a CSD118 in one of their 1.25 oz Fasteel loads, and by reading RSI's blurb about how shot was forced back into the wad upon firing.  They said something like 1.5 rows of shot above the top of the wad was fine.  

And so, I've used "1.125 oz" wads for heavier loads without concern.  But every time I give details of a 3" load without a 3" wad, I get the same questions: "how do you get 1.25 oz of shot to fit into a 1.125 oz wad?"

So here's a little show and tell.    

I marked an LBC43 wad with red sharpie to make it easier to see through a clear hull.

LBC43 with lipstick applied

Here's how #1 steel sits in the wad:

494 g

523 g

545 g

603 g

I then loaded up each of the weights.  I normally list the loads I use, but these are untested, and since all I'm trying to see is how much shot the wad will contain, the other particulars don't really matter.  The setback should be happening as the wad is leaving the hull, and I can't imagine a variation of 100 or so FPS will make much difference at that moment.

LOAD A:

LBC43

494 g #1 Fe

LOAD B:

LBC43

523 g #1 Fe + plastic beads

LOAD C:

LBC43

545 g #1 Fe + plastic beads

LOAD D:

LBC43

603 g #1 Fe

I loaded up Ol' Bessy Lou, and let her rip.  I chose to use the end of the drive thinking (I don't know why), that finding the wads would be a cinch.  Because, obviously, finding a four little pieces of greyish plastic would be easy on snowy gravel.  

But eventually, they were located.  

As you would expect, the 1.125 oz (494 g) load, for which the wad is rated, appears to have been contained with plenty of room to spare:

LOAD A: 494 g

LOAD A: 494 g

As does the 523 g load:

LOAD B: 523 g

LOAD B: 523 g

And the 545 g load:

LOAD C: 545 g

LOAD C: 545 g

...which is why I've always been comfortable using "1.125 oz" wads in 1.25 oz loads.  

So how much more room is there in this wad?  I should have tried 575 g... but I didn't.  Instead, I went with 603 g (I don't know why).  Well, there certainly is not enough for 1.375 oz:

LOAD D: 603 g

LOAD D: 603 g

You can clearly see indents of the bottom half of pellets along the top edge of the wad, especially in the photo of the outsides.  

But check out this weirdness:

weirdness

I'm not really sure what this little black pimple is.  It's not caused by shot, since it's pressing in, and I can guarantee no stray shot got between the wad and the hull.  It's almost like a burn-through mark--I've seen those on the wad skirt, but never up the side like this.  

 

But what about the barrel?  After all, the whole raison d'être for the wad in a steel load is to protect the barrel from the shot.  At some point, and again I don't know why, I purchased an 18.5" barrel threaded for choke tubes for my 870.  I don't believe I have fired it EVER, but if I have, it would have been a handful of target loads.  I decided to use it for this test with a cylinder choke to see if there would be any meaningful scoring of the barrel. 

Here's the barrel before any shots:

Breech

Muzzle.  Note that the CYL choke has been used a decent amount. 

And here it is after the 603 g load and a single pass with a boresnake:

Breech

Muzzle

Maybe not the best photos.   

I was expecting more--which is to say, at least some--scratches.  The few lines in the photos are actually streaks of light.

Now, that's only after one shell.  And it's only the top layer or so of pellets, which were exerting the least amount of sideways force.  We can assume that by looking at the indents on the wads: they get deeper toward the base of the wad, implying the shot is pressing into the plastic with more force.  So how deep  would the scoring be if the lower layers made complete contact with the bore? 

So what do the above photos tell us about wads other than the LBC's?  Only that the rating on the bag isn't a hard and fast rule.  But I suspect that other wads will have different stretchieness characteristics, and therefore different overload limits.