JDinFbg
Member
In a previous post (https://www.thehighroad.org/index.php?threads/bedding-my-1917-enfield.853101/) I reported on the process I used to bed my 1917 Enfield, officially named the "United States Rifle, cal .30, Model of 1917". Although the bedding process vastly improved the performance of the rifle, allowing me to achieve groups in the 1" range, I still had concerns about the overall condition of the original barrel. I could see from observation of the rifling at the muzzle that there was some pitting in the grooves, but I also wondered whether the barrel had a consistent bore diameter.
I had discovered that the shank end of a new, unused N drill bit would fit into the muzzle end of the barrel and could be slid in about an inch. An N drill bit supposedly measures 0.3020" in diameter, but mine mic'd at 0.3022" using my Brown & Sharpe micrometer capable of measuring to 1/10,000ths of an inch. Thus I wondered about the bore diameter of the rest of the barrel. To assess this, I machined a brass plug to mount on the end of a cleaning rod. I started with a plug measuring 0.3015", with the plan to make it progressively smaller if it wouldn't slide all the way down the barrel. My initial plug would slide all the way down the barrel, but I observed that there were two tight spots in the barrel, one about a third of the barrel length from the muzzle, and the other about a third of the barrel length from the chamber. This confirmed that the bore diameter was not consistent, and that it was definitely larger than the 0.300" bore diameter specified for the 1917 Enfield. Whether this was due to wear over the years or due to manufacturing tolerances not being held to tight standards I'll never know. In some posts I've read, several have suggested that in the rush to produce service rifles for WW-I, manufacturing quality may have been allowed to deviate from design specifications.
I wondered whether lapping the barrel might be a process that would allow me to relieve the tight spots in the barrel, make the bore more uniform in diameter over its entire length, clean up some of the pitting, and result in shooting smaller groups. Through some online research, I ran across a 2-part YouTube video describing a lapping process which I found very informative:
Part 1:
Part 2:
Having a metal lathe and the ability to machine everything I needed, I thought I'd give this a try.
For my lapping process I used some 800 grit lapping compound. I focused on lapping the barrel in the two areas where the bore was tight. Once those two tight areas were mostly relieved, I continued the lapping process until I felt fairly consistent resistance on the cleaning rod for most of the length of the barrel. The exception was that the bore was still somewhat loser at the muzzle. I spent about 2 hours on the lapping process, and probably made 400-500 lapping strokes, wiping off old and applying new lapping compound multiple times throughout the process. Once satisfied with the lapping job, clean-up followed using spray brake cleaner to flush the bulk of the lapping compound out of the bore, then multiple rounds of barrel cleaning with a bronze bore brush and Hoppe's solvent, and swabbing out with cleaning patches. In addition to the barrel lapping, I also lapped the crown of the barrel using a round-head, slotted brass screw in a drill and two different grits of lapping compound.
Whether the lapping effort made any difference in the shooting capability of the rifle could only be determined at the rifle range. Using the same load that had previously allowed me to shoot a 1" group, I shot three 5-shot targets to assess the performance quality. The test did not show that the lapping had reduced group size, but it did seem to reduce the extreme flyers that I had previously experienced. This was demonstrated by the mean radius of the groups shrinking from well over 1" in my previous shooting results to under 1" for all three test targets I shot after lapping the barrel. For all three test targets, 3 of the shots in the 5-shot group clustered within one inch, with one target having a 3-shot cluster under 0.4".
The conclusions are that my old 1917 Enfield with the original barrel is never going to be a high precision rifle and is going to remain a 1.5" to 2" grouper. The epoxy steel bedding had the most impact on reducing group sizes, but the lapping work only seemed to make the rifle a more consistent shooter and reduce the extreme bullet spreads I previously experienced. All of my work resulted in shooting performance far better than it started off, and I feel it will be plenty good for hunting large varmints like feral hogs.
I had discovered that the shank end of a new, unused N drill bit would fit into the muzzle end of the barrel and could be slid in about an inch. An N drill bit supposedly measures 0.3020" in diameter, but mine mic'd at 0.3022" using my Brown & Sharpe micrometer capable of measuring to 1/10,000ths of an inch. Thus I wondered about the bore diameter of the rest of the barrel. To assess this, I machined a brass plug to mount on the end of a cleaning rod. I started with a plug measuring 0.3015", with the plan to make it progressively smaller if it wouldn't slide all the way down the barrel. My initial plug would slide all the way down the barrel, but I observed that there were two tight spots in the barrel, one about a third of the barrel length from the muzzle, and the other about a third of the barrel length from the chamber. This confirmed that the bore diameter was not consistent, and that it was definitely larger than the 0.300" bore diameter specified for the 1917 Enfield. Whether this was due to wear over the years or due to manufacturing tolerances not being held to tight standards I'll never know. In some posts I've read, several have suggested that in the rush to produce service rifles for WW-I, manufacturing quality may have been allowed to deviate from design specifications.
I wondered whether lapping the barrel might be a process that would allow me to relieve the tight spots in the barrel, make the bore more uniform in diameter over its entire length, clean up some of the pitting, and result in shooting smaller groups. Through some online research, I ran across a 2-part YouTube video describing a lapping process which I found very informative:
Part 1:
Part 2:
Having a metal lathe and the ability to machine everything I needed, I thought I'd give this a try.
For my lapping process I used some 800 grit lapping compound. I focused on lapping the barrel in the two areas where the bore was tight. Once those two tight areas were mostly relieved, I continued the lapping process until I felt fairly consistent resistance on the cleaning rod for most of the length of the barrel. The exception was that the bore was still somewhat loser at the muzzle. I spent about 2 hours on the lapping process, and probably made 400-500 lapping strokes, wiping off old and applying new lapping compound multiple times throughout the process. Once satisfied with the lapping job, clean-up followed using spray brake cleaner to flush the bulk of the lapping compound out of the bore, then multiple rounds of barrel cleaning with a bronze bore brush and Hoppe's solvent, and swabbing out with cleaning patches. In addition to the barrel lapping, I also lapped the crown of the barrel using a round-head, slotted brass screw in a drill and two different grits of lapping compound.
Whether the lapping effort made any difference in the shooting capability of the rifle could only be determined at the rifle range. Using the same load that had previously allowed me to shoot a 1" group, I shot three 5-shot targets to assess the performance quality. The test did not show that the lapping had reduced group size, but it did seem to reduce the extreme flyers that I had previously experienced. This was demonstrated by the mean radius of the groups shrinking from well over 1" in my previous shooting results to under 1" for all three test targets I shot after lapping the barrel. For all three test targets, 3 of the shots in the 5-shot group clustered within one inch, with one target having a 3-shot cluster under 0.4".
The conclusions are that my old 1917 Enfield with the original barrel is never going to be a high precision rifle and is going to remain a 1.5" to 2" grouper. The epoxy steel bedding had the most impact on reducing group sizes, but the lapping work only seemed to make the rifle a more consistent shooter and reduce the extreme bullet spreads I previously experienced. All of my work resulted in shooting performance far better than it started off, and I feel it will be plenty good for hunting large varmints like feral hogs.
