smithywess
07-22-2012, 03:48 PM
Having worked up an accurate load in .44-40 in a Marlin Model 1889 I changed it's barrel to .38-40 as I don't have a .38-40 but I do have another .44-40 in a vintage Model '94 which shoots well. Here is the rifle with the swapped barrel.
http://i395.photobucket.com/albums/pp38/smithywess/27-a-Right.jpg
I have found with all these old rifles originally designed to fire blackpowder that they are usually overbore for easily available cast bullets. My .38-40 barrel slugs to .4105" and I was concerned that if I tried to seat a bullet one or two thousandths greater than that diameter that I might split the case and, if not, that I would be unable to chamber a bullet at . 412"/.413". Nonetheless I obtained a custom mould at .412", and with a 180 grain bullet, from Tom at Accurate Moulds ( a very nice mould) and sized bullets to .410" with a push through Lee bullet sizer that I use for loading my .40-65 cases. This seemed to me to be a happy compromise in that I had the sizer and it is but .0005" underbore. I hoped that even with smokeless powder there might be at least some obturation of my wheelweight, and some tin, cast bullets. I was only looking for .0005" to seal the bore ! Moreover I was planning to use a filler in the form of Polyethylene Shot Buffer which acts as a flexible gas check between the bullet and 17.0 grains of I.M.R. 4227. In order to help the seating process in the case I first expanded and belled the case with the R.C.B.S. expander that came with the Cowboy Action dies in .38-40. This took the expansion to .401" which I took further to .406" with the expander die from my .40-65 set. Seating the sized bullet at .410" wasn't difficult and gave good neck tension to disallow any shift of the bullet backwards in the case under recoil. I don't know to what extent my compressed load of filler would achieve the same end. I applied a light roll crimp with the R.C.B.S. seating die in the usual way. Sure enough I was unable to chamber this round until I elected to ream the chamber throat a trifle until the round would chamber. I obtained the reamer from Pacific Tool Co. I then fired a 5 shot group but first without the filler and obtained this target at 50 yards.......
http://i395.photobucket.com/albums/pp38/smithywess/MarlinModel1889Unfillered5shotgroup.jpg
It was interesting to observe that the group was quite tight and I would bet that there was indeed some bumping up of those bullets to at least partially seal the bore. I couldn't recover the bullets but there was no leading. The chronographed speed was 1124 f.p.s.. Clearly I also needed to raise the front sight and drift the rear one to the left. This I did and fired one more 5 shot group at the same distance but this groups was made with cases fillered with a compressible amount ( 6.5 grains) of Polyethylene Shot Buffer........
http://i395.photobucket.com/albums/pp38/smithywess/MarlinModel18895shotgroupFillered-1.jpg
The speeds were chronographed at 1300 f.p.s. indicating some increase in pressure, and I do believe that the group is tighter. Certainly the adjustment in the sights brought the group to centre. At the very least the addition of the filler would eliminate any position sensitivity of the powder in the cases because the 17.0 grains of I.M.R. 4227 only produced a 50% fill within the case. These groups were made from a 6 0'Clock hold on the aiming mark and off sandbags
I think I'll stay with this load,
Thanks.
http://i395.photobucket.com/albums/pp38/smithywess/27-a-Right.jpg
I have found with all these old rifles originally designed to fire blackpowder that they are usually overbore for easily available cast bullets. My .38-40 barrel slugs to .4105" and I was concerned that if I tried to seat a bullet one or two thousandths greater than that diameter that I might split the case and, if not, that I would be unable to chamber a bullet at . 412"/.413". Nonetheless I obtained a custom mould at .412", and with a 180 grain bullet, from Tom at Accurate Moulds ( a very nice mould) and sized bullets to .410" with a push through Lee bullet sizer that I use for loading my .40-65 cases. This seemed to me to be a happy compromise in that I had the sizer and it is but .0005" underbore. I hoped that even with smokeless powder there might be at least some obturation of my wheelweight, and some tin, cast bullets. I was only looking for .0005" to seal the bore ! Moreover I was planning to use a filler in the form of Polyethylene Shot Buffer which acts as a flexible gas check between the bullet and 17.0 grains of I.M.R. 4227. In order to help the seating process in the case I first expanded and belled the case with the R.C.B.S. expander that came with the Cowboy Action dies in .38-40. This took the expansion to .401" which I took further to .406" with the expander die from my .40-65 set. Seating the sized bullet at .410" wasn't difficult and gave good neck tension to disallow any shift of the bullet backwards in the case under recoil. I don't know to what extent my compressed load of filler would achieve the same end. I applied a light roll crimp with the R.C.B.S. seating die in the usual way. Sure enough I was unable to chamber this round until I elected to ream the chamber throat a trifle until the round would chamber. I obtained the reamer from Pacific Tool Co. I then fired a 5 shot group but first without the filler and obtained this target at 50 yards.......
http://i395.photobucket.com/albums/pp38/smithywess/MarlinModel1889Unfillered5shotgroup.jpg
It was interesting to observe that the group was quite tight and I would bet that there was indeed some bumping up of those bullets to at least partially seal the bore. I couldn't recover the bullets but there was no leading. The chronographed speed was 1124 f.p.s.. Clearly I also needed to raise the front sight and drift the rear one to the left. This I did and fired one more 5 shot group at the same distance but this groups was made with cases fillered with a compressible amount ( 6.5 grains) of Polyethylene Shot Buffer........
http://i395.photobucket.com/albums/pp38/smithywess/MarlinModel18895shotgroupFillered-1.jpg
The speeds were chronographed at 1300 f.p.s. indicating some increase in pressure, and I do believe that the group is tighter. Certainly the adjustment in the sights brought the group to centre. At the very least the addition of the filler would eliminate any position sensitivity of the powder in the cases because the 17.0 grains of I.M.R. 4227 only produced a 50% fill within the case. These groups were made from a 6 0'Clock hold on the aiming mark and off sandbags
I think I'll stay with this load,
Thanks.