[IDShooter]

Hello everyone,
     I just returned from the range, where I firelapped two guns. The first was a great success, the other we'll call a draw.
     The first one alluded to is my Ruger 77MKII .257 Roberts. After a coyote hunting trip this winter I ran a patch through the bore only to see orange - a little rust from the fog and humidity. There was no visible pitting but all of a sudden the rifle started fouling terribly, just after I got it shooting well, too. So I rolled some 115gr BT's in lapping compound, 5 in 220 grit and 10 in 320 grit. After lapping I fired six rounds of regular ammo, and they left very little copper in the bore - EUREKA! I'm going to chronograph some loads soon to see if there was an effect on velocity, since I've read that lapping can decrease velocity in some rifles. We'll see! Accuracy was unchanged BTW.
      As for the other gun, I fired fifty lapping rounds through my GP-100 while I was at it. It didn't make any impact at all on my cast bullet loads (still mediocre), I believe I'm going to have to open up the chamber throats a bit to get the proper lapping action. But it still shoots gangbusters with that Speer 158gr JSP. I shot at a prairie dog target at 50 yds and made 4 vital hits out of six. Total group size was about 3.5 inches. That's about the best I've done at 50 yds so far. Now, as soon as I get it shooting that well with cast....                 IDShooter

 

[cast-n-blast]

ID,
  3.5" at 50 yds., with open sights, is very commendable ! As far as cast bullets are concerned, can they be pushed thru the cylinder mouth with finger pressure ? If not, you know what your next project is. Again, nice shootin' ! <!--emo&--><img src="http://beartoothbullets.com/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=''><!--endemo-->

                               Jeff

  P.S. Did the Ruger foul less after lapping ? If so, that's another feather in your cap.

 

[IDShooter]

Hi Jeff,
     The cast bullets I'm trying are sized .358 and they won't push thru the cylinder with finger pressure. In fact I had to take a dowel and a hammer to get one through! I have slugged the bore, and that slug will just barely push thru the cylinder using the dowel with hand pressure. So the cylinders are just slightly bigger than the barrel grooves, but they are definitely pretty tight.
       I'm planning on honing them using emory paper and a split steel rod, but so far I have not found a suitable rod. I'm a little nervous about this project, especially given the super accuracy the jacketed bullets have exibited. But I really do want it to be accurate with cast bullets, too.
       As far as fouling, the .257 Roberts improved greatly after lapping. The GP-100 hasn't fouled badly since it was rebarreled, so it was hard to detect much difference there. There was no lead and only a little copper left in the bore after my session.
     Thanks for your comments!        IDShooter

 

[cast-n-blast]

ID,
  Jacketed, spacketed ! You know it's more fun and self satisfying shootin' cast over jacketed <!--emo&--><img src="http://beartoothbullets.com/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=''><!--endemo-->. Not to mention easier on your barrel and wallet.

  As far as polishing out those cylinders the split rod, hand drill, emory paper route, do not fret ! I have done about a dozen of my guns this way with super results. All holes are polished evenly, with nice round, concentric holes. The existing holes make perfect guides for your home made arbor using 320 grit emory paper. Once the bullet can be pushed thru with finger pressure, move on to the next one. I was more nervous fire lapping my barrels, than doing the cylinder job. Jump in there, you won't be disappointed !

                             Jeff

 

[IDShooter]

Well, I took the great leap and honed out the chamber throats on the GP-100 today! I believe I got them pretty close to the same all the way round. It takes similar pressure to push a cast bullet through each one now. And the bullet I used to slug the bore now slips through the throats easily, so they are definitely just a bit larger than the groove diameter now. I think another round of lapping will have the desired affect on the frame constriction and hopefully I will have the cast bullet accuracy I desire. On my SBH the throats were already larger than bore diameter and a bit of lapping turned it into a heck of a cast bullet shooter.
       MikeG, while I had the gun apart I took your suggestion on polishing the hammer strut. It smoothed up the DA pull nicely, though it is still very heavy. I still haven't ordered the spring kit from Brownell's yet.
        Hopefully I can shoot Thursday and give everyone an update!            IDShooter