View Full Version : 1873 trapdoor

Mike in TX
November 17, 2004, 08:19 AM
My grandfather, in 1963, gave me his Springfield trapdoor. It was a rifle and he had the barrel shortened. My problem is that now I am shooting the rifle and have a problem with the sights. It is on at about 4 feet high at 100 yards but the rear sight is set on the lowest setting. Any ideas on how to measure for a new front sight? I am looking at an original front sight set up but do not know if the barrel taper will hinder a sucessful procedure. As you can see I know virtually nothing about this weapon. Thanks for any and all information. :)

November 26, 2004, 07:29 PM
grouping 4 feet high at 100 yds sounds like a pretty dramatic problem. Are you sure the barrel isn't bent or something? It will also depend on what loads you use, but even with that variable..... If it is really that far off at 100 yds, you might have to make some kind of tall blade front sight for it. Probably will not look like the original sight which was probably not very tall. You can calculate how much the front sight has to be raised, but with a given load. Calculate the number of inches in 100 yards. Measure the distance between the front and rear sights in inches. Divide that figure into 100 yds(in inches).
Measure how many inches the bullets strike above the exact aim point. Divide that number by the results of dividing the sight spaceing into 100 yds, prevouisly figured. Basically you are gonna get probably a fraction of an inch which is how much your front sight is short. Add height of front sight as it is now to get total height needed. Basically you can diagram that by imagining a straight line from your rear sight to the front sight, and on to the aim point. Then imagine a line from your rear sight to the actual impact point. This forms an angle and the concept is just basic geometry. Works for windage too.

Harry Bonar
January 18, 2005, 03:01 PM
Either the bbl is bent (doubt it) or the front sight isn't high enough, or, when he shortened the bbl. the "crowning is off. (I've see 4 foot deviations from an improperly crownd bbl.)

January 18, 2005, 03:20 PM
You might also want to try a lighter bullet. They generally strike lower than the heavier bullets.