Post by Bullshop on May 23, 2020 14:10:36 GMT -7
Today 5/23/20 my day off I was able to conduct another test I have been wanting to do with my Springfield Trapdoor 50-70. This cut down rifle to carbine configuration is dated 1869 on the breach block but the lock plate is dated 1863. It does not appear to be an Allen conversion. The barrel has the standard three land and groove configuration in not great but shootable condition. It looked poor when I got it but with a lot of soaking and cleaning looks fair to good now with good rifling but some pitting.
I have never slugged the bore because it seemed to shoot OK with what has always been the standard bullet the Lyman #515141 at .512" diameter. I have never made bullets expressly for this rifle but instead when ever I get orders for 50-70 bullet I would run a few extra and shoot them up. In the process of shooting up the extras the gun seemed to show a preference for larger diameter bullets.
Our Lyman 515141 mold drops at .514" diameter so we offer it at .512" AND .514" diameters. Those always seemed to shoot fair but exactly what level of accuracy does one expect from this type of vintage rifle with a less than excellent bore? 4" to 5" at 50 yards seemed about normal for this rifle and I was not surprised with that considering the condition.
Thinking that I may want to use it to fill a dear tag I began to make bullets and loads with a more deliberate attitude. One thing I noticed was that the gun seemed to prefer very soft alloy even doing good with pure soft lead at BHN-5. That is good because for deer pure lead at black powder velocity works very well.
Today what I wanted to test for was to see if the rifle would show a preference for any specific bullet diameter. What I planned to try was .512", .514", .515", .518" and .521" bullet diameters.
Some time back I used Dan Lynch's program to design a sort of copy of the 515141 that would drop at a larger diameter since we were getting requests for such from customers. Due to the program limits I could not get an exact copy but what I got was close. The big difference is that the Lyman is slightly longer at .969" and has three lube grooves where our custom design has two lube grooves and is .897" in length. Overall lube capacity is about equal because lube grooves on our design are wider and slightly deeper. The slightly shorter length is not a problem and may benefit some vintage rifles with very slow rifling twist rates. Ardith Barker had a good wright up on all the twist rates used for the 50-70 and is a very informative read if your interested. He stated that even with the faster twist guns bullet length could not exceed 1" or accuracy would suffer.
The load I used today is a moderate pressure smokeless powder load using 12 gn of Alliant Unique. After the powder is thrown the case is then filled with Styrofoam packing popcorn then compressed with the bullet. This gives very uniform ignition with a powder charge that is something less than 50% of case volume. The PP holds the powder in a consistent column on the primer without raising chamber pressure. This is something I have been doing for nearly 40 years and have never witnessed any ill effects.
The first two target using .512" and .514" were about normal for what I have come to expect from the rifle, no surprises. Going up to .515" on the third target was a big surprise. Two possible reasons are that the .512" and .514" were fired with the Lyman bullet and since it only drops from our mold at .514" I went to our custom bullet for the .515" test. This bullet drops from the mold at .521" so had to be sized down .006" for this test. Also when loading for the smaller diameters I do not inside size because my inside expander is too large and eliminates all neck tension to where the bullets are loose in the case. To eliminate the looseness I FL size the cases but then use a punch to bell the case mouth. This keeps good neck tension on the smaller diameter bullets. I did this up to the .515" bullet and noticed the unfired loaded rounds showed a bulge at the location of the base of the bullet in the case. Those two things must have had something to do with the results of the third target with .515" bullets.
The next two targets with .518" and .521" diameters were loaded using the inside expander because with the larger diameters there is plenty of case neck tension. Interestingly the cartridges loaded with the .518" diameter bullets looked normal but the cartridges loaded with the .521" diameter bullets looked the same as the ones loaded with the .515" bullets even after inside expanding the brass they showed the bulge at the location of the bullet base in the case.
At this point I was wondering if the cases loaded with the .521" bullets would even chamber but to my surprise there was no felt resistance to their chambering. This might be a good thing because I discovered that with this diameter bullet fired cases do not require sizing so case life should improve.
All loads used Starline brass and all bullets were lubed with our NASA lube which is our black powder lube but also works good with smokeless powder at normal black powder pressures. Bullets were cast in an very soft alloy at BHN 7.5
So without further ado the pictures. If you click on them they will enlarge.
I have never slugged the bore because it seemed to shoot OK with what has always been the standard bullet the Lyman #515141 at .512" diameter. I have never made bullets expressly for this rifle but instead when ever I get orders for 50-70 bullet I would run a few extra and shoot them up. In the process of shooting up the extras the gun seemed to show a preference for larger diameter bullets.
Our Lyman 515141 mold drops at .514" diameter so we offer it at .512" AND .514" diameters. Those always seemed to shoot fair but exactly what level of accuracy does one expect from this type of vintage rifle with a less than excellent bore? 4" to 5" at 50 yards seemed about normal for this rifle and I was not surprised with that considering the condition.
Thinking that I may want to use it to fill a dear tag I began to make bullets and loads with a more deliberate attitude. One thing I noticed was that the gun seemed to prefer very soft alloy even doing good with pure soft lead at BHN-5. That is good because for deer pure lead at black powder velocity works very well.
Today what I wanted to test for was to see if the rifle would show a preference for any specific bullet diameter. What I planned to try was .512", .514", .515", .518" and .521" bullet diameters.
Some time back I used Dan Lynch's program to design a sort of copy of the 515141 that would drop at a larger diameter since we were getting requests for such from customers. Due to the program limits I could not get an exact copy but what I got was close. The big difference is that the Lyman is slightly longer at .969" and has three lube grooves where our custom design has two lube grooves and is .897" in length. Overall lube capacity is about equal because lube grooves on our design are wider and slightly deeper. The slightly shorter length is not a problem and may benefit some vintage rifles with very slow rifling twist rates. Ardith Barker had a good wright up on all the twist rates used for the 50-70 and is a very informative read if your interested. He stated that even with the faster twist guns bullet length could not exceed 1" or accuracy would suffer.
The load I used today is a moderate pressure smokeless powder load using 12 gn of Alliant Unique. After the powder is thrown the case is then filled with Styrofoam packing popcorn then compressed with the bullet. This gives very uniform ignition with a powder charge that is something less than 50% of case volume. The PP holds the powder in a consistent column on the primer without raising chamber pressure. This is something I have been doing for nearly 40 years and have never witnessed any ill effects.
The first two target using .512" and .514" were about normal for what I have come to expect from the rifle, no surprises. Going up to .515" on the third target was a big surprise. Two possible reasons are that the .512" and .514" were fired with the Lyman bullet and since it only drops from our mold at .514" I went to our custom bullet for the .515" test. This bullet drops from the mold at .521" so had to be sized down .006" for this test. Also when loading for the smaller diameters I do not inside size because my inside expander is too large and eliminates all neck tension to where the bullets are loose in the case. To eliminate the looseness I FL size the cases but then use a punch to bell the case mouth. This keeps good neck tension on the smaller diameter bullets. I did this up to the .515" bullet and noticed the unfired loaded rounds showed a bulge at the location of the base of the bullet in the case. Those two things must have had something to do with the results of the third target with .515" bullets.
The next two targets with .518" and .521" diameters were loaded using the inside expander because with the larger diameters there is plenty of case neck tension. Interestingly the cartridges loaded with the .518" diameter bullets looked normal but the cartridges loaded with the .521" diameter bullets looked the same as the ones loaded with the .515" bullets even after inside expanding the brass they showed the bulge at the location of the bullet base in the case.
At this point I was wondering if the cases loaded with the .521" bullets would even chamber but to my surprise there was no felt resistance to their chambering. This might be a good thing because I discovered that with this diameter bullet fired cases do not require sizing so case life should improve.
All loads used Starline brass and all bullets were lubed with our NASA lube which is our black powder lube but also works good with smokeless powder at normal black powder pressures. Bullets were cast in an very soft alloy at BHN 7.5
So without further ado the pictures. If you click on them they will enlarge.