1884 Trapdoor - BPCR Check

[Patrick Chadwick]

The 480gn bullet will probably be more accurate than the 405gn. The service load was a 405gn bullet, but a 500gn load was introduced for target/competition shooting (it's mentioned in Frasca & Hill, "The 45-70 Springfield".

Re. bullet crunching the powder. Tap a lot (I drum on the table 10 times) and the powder will settle some more, so less "crunch".
Opinions differ, but I reckon that "crunching" should not be more than 1/16" - absolute max. 1/8" - otherwise you may be breaking up the powder grains, which could affect the burning rate. Best is no crunch,as that is yet another variable that affects the ballistic consistency, i.e. grouping.

Check how far the bullet can be seated out to touch the lands. My experience is that seating the bullet about 1mm off the lands give the best results. In my rifles this typically means that the first grease groove is exposed, so one must take care to keep the loaded cartridges clean.

Pure lead bullets slug up quite considerably. Hard lead alloys don't. So there is a strong interaction between bullet size and the appropriate alloy. The harder the mix, the closer the bullet must be to groove diameter. As it says over and over again in the Lyman manuals: Slug your bore and size accordingly.

Use only pure lead or lead/tin for bullets. Something in the range 5-10% tin should be OK. Anything with antimony is likely to be too hard.

Let us know how you get on!

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