Back in the late eighties or early ninties, Veral Smith, who runs Lead Bullet Technology, came up with using fine lapping compound to polish rifle barrels. Basically, a fine lapping compound was smeared on a steel plate and with another steel plate, the bullet was rolled between the plates embedding the compound into the bullet. The bullets were loaded with a light charge of pistol powder and several were fired down the cleaned rifle barrel. This procedure removed any microscopic burrs left behind from the rifling process, and would smooth the edges of any pitting that was present in the barrel. This paste was finer than any valve grinding compound and is quite expensive. I have used this technique in the past with good success.
More recently, Merrell Martin, reporting in the now defunct Precision Shooting magazine, that he had even better results using diamond paste. I have a well used ZG-47 from 1956, with a 1962 barrel, that has been well used, but with a nice, shiny bore. However, the best I could manage with well prepared ammunition was 3 & 1/8 inches at 100 yards for 10 shots. It was a fairly circular group. The hole under the 3 is a .22 from another shoot.
This morning, I fired some lapping loads of 3 using 10 micron diamond paste, 4 with 7 micron and 4 using 5 micron, cleaning after every two shots. The next ten shots, with the same ammunition as before, were in 2 & 1/2 inches. Seven of them were in 1 & 13/16 inches and the remaining three were in a tight group.
So it is apparent that diamond lapping provides some benefit. The little group could be due to operator error, perhaps shifting my position on the bags. As well, a sporting rifle might not like a ten shot string and the heat it generates, although the load was a mild one. (25 gr H-41 and a 168 gr bullet - .30/'06) Also, the stock screw which screws into the barrel may have an adverse effect. I'll try bedding the recoil lug area next.
More recently, Merrell Martin, reporting in the now defunct Precision Shooting magazine, that he had even better results using diamond paste. I have a well used ZG-47 from 1956, with a 1962 barrel, that has been well used, but with a nice, shiny bore. However, the best I could manage with well prepared ammunition was 3 & 1/8 inches at 100 yards for 10 shots. It was a fairly circular group. The hole under the 3 is a .22 from another shoot.
This morning, I fired some lapping loads of 3 using 10 micron diamond paste, 4 with 7 micron and 4 using 5 micron, cleaning after every two shots. The next ten shots, with the same ammunition as before, were in 2 & 1/2 inches. Seven of them were in 1 & 13/16 inches and the remaining three were in a tight group.
So it is apparent that diamond lapping provides some benefit. The little group could be due to operator error, perhaps shifting my position on the bags. As well, a sporting rifle might not like a ten shot string and the heat it generates, although the load was a mild one. (25 gr H-41 and a 168 gr bullet - .30/'06) Also, the stock screw which screws into the barrel may have an adverse effect. I'll try bedding the recoil lug area next.
Last edited:
