How do you measure the bore?

[jeep08ham]

I read about some of the Handi bores being tapered.   What is the best method to use to get very accurate measurements? 

I have a 25-06 Heavy barrel and have trouble getting it to shoot well.   Groups have been from 3-5 inches at 100 yards off of bench rest.  Placing the rest behind the hinge pin and have followed all other suggestions I can find.  Changed scopes. Used factory loads of different brands and weights.  Tried a number of different reloads and the only thing consistent is the big groups.  There is a lot of free bore in the barrel but have tried setting bullets out close and every .005" away from the lands until I have backed off .040" but did not seem to make any difference.  Have had others shoot it and had same results.  Get my old Mark X 25-06 for comparison out and it will shoot with the worst loads into 1.75 inch groups.   

Thanks in advance for the help.

[quickdtoo]

See bore slugging in the FAQs and Help sticky.

Have you checked the latch and latch shelf for oil? That's the number one cause of inaccuracy and the easiest to fix. If it won't shoot 3" or under groups, contact H&R and ask that it be repaired, mine shoots two shots touching or close to it and the third opens the group to about 1", that's with two different factory rounds, nothing done except a trigger job, never needed to handload for it, 25-06 H&Rs are typically very accurate.

Dunno what ya mean by 25-06 "heavy barrel" as H&R only offers a standard contour 26" barrel, if it's shorter than 26", it's been cut off which may give it the appearance of being heavy. Their standard contour barrels are typically heavier than other makes though, but not as heavy as H&R bull barrels which are ~.800" at the muzzle.

Tim

[STUMPJMPR]

I would also inspect the crown on the barrel...That can cause severe accuracy problems as well....

[jwv]

I bought a 25-06 barrel from fanner50 back in March of this year. It was a new barrel and I knew it would take a while before it would start shooting good groups.
  I started out  just shooting factory 100 grain Remington core-locks and my groups were around  2 inches or more. After 3 boxes of those I started reloading with the Sierra 100 grain SP and the best I could get my groups down to were 1 1/2". Up to that time I had put a little over 100 rounds thru the barrel and it had been polished several times, so I decided to try the Hornady factory 117 grain BTSP  and those shot a 3/4" group  my son took the gun and he  shot a 5/8" group.Those were 3 shot groups.
       One thing I found that made a big difference for me was the amount of copper the barrel would get even after several polishing jobs. Be sure and use a good copper cleaner  like wipeout or the outers foam and use 2 or 3 applications. Carbon buildup can also be a problem with the 25-06 so watch out there. That bore can look real clean but can still have copper and carbon  buildup. I don't know how many rounds you have put thru yours but I beleive it will shoot a good group for you in time. As for possible bore taper only a trip to  H & R would give you the answer there.   Good luck,  Jack
   

[jeep08ham]

Thanks for the thoughts on this issue.  I have polished the bore several times and have put about 300 rounds through this barrel.  I will triple check all of the things everyone has mentioned to this time.

I do welcome more input if it helps solve this issue.

Thanks in advance for the help!

[MTGlass]

To you original question, here's how I did it.

I used caliber specific LBT push through slugs made specifically for measuring and feeling relative smoothness &/or diameter variations rifled bores.  They have a tip for inserting into the end of a cleaning rod and a short bearing band which allows pushing through a bore by hand rather than pounding.

LBT is sponsored on this board and can be found over in the Cast Bullet forum.

After cleaning and polishing with J-B, I pushed a slug breech to muzzle.  The bore felt snug just ahead of the throat then loosened up noticeably.  I was distressed so I pushed another through muzzle to breach.  Again, the bore felt tighter toward the throat.  Then I pushed a slug into the muzzle about 3/16" and pulled it back out and measured.  Then I pushed another from the breech up into the tight area and tapped it back out for measuring. Calipers didn't tell me anything I already didn't know.  The bore was tapered backwards. The calipers just gave me numbers.

I wasted about 200 rounds on that barrel before sending it back to H&R.  The backwards taper in the replacement barrel is less but still there and the barrel shoots reasonably well.

Pure lead egg shaped sinkers with a hole through the center are an alternative to LBT slugs.  I've normally had to pound them through.

Another method is to impact a slug in the bore to really fill in the lands which may provide a more precise mold or cast of the bore at a given point.  Repeat at various points then measure each slug & determine the differences in diameter and where they occur.

[OBXPilgrim]

never needed to handload for it,

Tim

Hummm, never really thought of "needing to handload" for a gun before - interesting thought.  Guess I just always preferred to shoot my own loads.  Not trying to start anything by it, just a different way to think about it.

Unless you're planning on shooting cast lead, I think you're wasting your time slugging the bore.  I bet you could find the problem in the lock-up like Tim eluded to.  My 22 hornet gave me fits until I checked the lock-up by marking the barrel face & latch shelf of the barrel with a black marker & cycled the action several times.  I had a large bearing mark on one side of the shelf only.  I took some stock off the face of the latch & barrel face (very slowly), checking in between passes with the stone.  The next time out, the little bugger went from 5-8" groups to 1.5-2" groups.

The groups I had were well dispersed triangular groups - not vertical stringing.

Hope that helps.