LE No.5 chamber slugged, advice pls?

[Canuck Bob]

My initial slug work on my No.5 is done. The throat measure .3153 close to the chamber face and seems to taper a bit to .314 amd maybe .3138 at the rifling start. The slug shows no evidence of any erosion but I'm not sure what to look for. The 5 groove is baffling me so no groove diameter yet. From the appearance of the slug it should come in at .313 or a shade smaller. I'm planning a more controlled slugging tonight to confirm my findings. Also the throat seems quite long, at least .400. This No.5 is a 9/45 manufacture BSA Shirley rifle.

I must admit that I'm happy with the sizing after reading of early Mauser sized chambers and bores! Does this indicate my cast and paper patch efforts might be less prone to grief?

[longbow]

Not sure if this will help or not as I haven't done a chamber cast, I used a lead slug to get throat diameter.

Mine came out at 0.315"+ a hair like yours. I was getting poor accuracy with Lyman 314299 that cast at 0.312" to 0.313". Best as I could tell my groove diameter is 0.314". I decided to size to suit the throat and that has worked well. Of course it took a new mould that cast to correct size ~ an NOE 316299 which is working well.

I have not done very well paper patching for this gun yet. I had made a mould that cast at 0.301" per Lyman and that works well in my .308 but so far has produced mediocre accuracy in my .303's. I tried knurling to bring diameter up some and that helped so the next step is to try larger boolits:

- I have a Lyman 31141 mould that actually casts at 0.310"/0.311" (its an old one) so have patched some with 0.002" tracing paper then sized to 0.315"
- I plan to ream out my mould or make a new one to cast at about 0.305" so a couple thou over bore diameter and try that. If the 31141's work well then I may go to 0.307"/0.308".

The suggestion I'll make is to use a boolit at or larger than bore diameter then patch to suit the throat at about 0.315" in your case.

Paper patches may expand a little so possibly sizing slightly smaller would be good. I have not tried mine sized to 0.315" yet so can't comment for sure but as long as they chamber I want them as close to throat diameter as possible.

Longbow

[WineMan]

My limited experience with a 1903A3, which has a NOS two groove barrel, showed that if I can get it to chamber with enough room to let the boolit go, then bigger (fatter) was better. For me that meant that 0.314" was perfect. That would be my tack for your rifle: go for as big a slug as will fit in the throat and not worry too much about the groove/land diameter.

Wineman

[303Guy]

go for as big a slug as will fit in the throat and not worry too much about the groove/land diameter.Exactly. I'd suggest trying weaker paper. Cheapo printer/copier paper works great for me and so does cheap lined note-pad paper, the latter being thinner which compensates for the slightly oversize casting but seems to work just fine.

Unless the bore is absolutely mint, the rifling won't easily cut 100% cotton tracing paper. My mileage may differ because I'm using smooth sided boolits.

I've found that heavy boolits are easier to load for as they will burn slower powders better. I also use wheat bran as a filler to get the slow powder to burn and hold it against the primer.