Asking for a friend... Rusty bore issue?

[WonkyEye]

Hey WonkyEye, thanks for the fast response. A few more details, he’s a very seasoned hunter, a very good shot, and we used a Leadsled. Our frustration was the very acceptable 2-3 shot group, then the random one in 4 or 5 shot crazy flier… I checked the crown, no dings… we spent 4 hours at the range in 22deg cold testing, fun, but… a bit chilly! The powder charge will IMHO help to tune the barrel harmonics, slowly shrinking the group, but the nice 2-3” 3-4 shot group, then a wild shot… why? Your testing is classic, slowly fine tuning… ladder loads. We used my chronograph, and using 80gr 2Fg had a stable 1250-1275fps… the target shows no keyholing, I’m a retried engineer, so quite used to changing just one variable at a time… we tried changing lubes, then cold clean bore, dirty bore, we used borebutter to lube the bore before a load… these were all shot as 5 shot test groups… same with all of the above, these gave the same unpredictable results… This gun has a hooked breech, so no bedding, wedge barrel lock, all tight… sights are on the barrel, and very secure. This issue has sadly destroyed his confidence in the gun. Timing permitting, we may try PRBs with bigger charges, looking for fliers… less bore contact, SHOULD make PRBs more sensitive to a bad bore. I’ll recast the REALs, pure lead, and maybe try a grease cookie… the bore is pitted, but I cannot rationalize the good, good, good, good shots, then a bad flier out of the minute of Bambi safe shot zone. The fliers are our as, yet, unexplained issue.

The bore of this TC NE was rusty and pitted… now clean, no rust, heavily burnished… but still pitted… That IMHO would create an increasing accuracy issue, groups 2-3”, or 4-5”, not this whacky sporadic flier basis… and yet, here we are… as I said, fun, but… I appreciate the input, and advice.. just looking for miracles… I’m most curious as to how anyone’s similar bad bore behaves.. always mediocre, getting worse… yes. This 2-3 good shots within a few inches, then a 9-15” sporadic flier… I find that hard to rationalize.

More when we know!

Cheers!

S1 MT.

Thanks for explaining. My bore is/was not great, but most of my issues were more related to difficult cleaning and ripped patches, and generally large groups. Lapping helped in all respects. The random flier does not compute for me either. I wish I had something more to add.

 

[Steve 1]

Thanks for explaining. My bore is/was not great, but most of my issues were more related to difficult cleaning and ripped patches, and generally large groups. Lapping helped in all respects. The random flier does not compute for me either. I wish I had something more to add.

Thanks, that in of itself implies I’m not crazy… well, not that crazy! All geeks, MLs etc hate the unexplained.
This has now become a crusade… I enjoy a challenge… so we’ll see!

G’night all.

S1

MT

 

[Steve 1]

Thanks, that in of itself implies I’m not crazy… well, not that crazy! All geeks, MLs etc hate the unexplained.
This has now become a crusade… I enjoy a challenge… so we’ll see!

G’night all.

S1

MT

Eureka!

I hope this note resolves this thread to a close. I may have discovered the cause of the errant flier REAL projectiles in my friend’s rifle.
I was casting various alloys to determine shrinkage etc, and it became apparent that my week old Lee REAL mold, 54 cal 300gr dual cavity, measured a woeful 0.013” undersize, the topmost driving band, should measure 0.557” that gets heavily engraved by the rifling… it measured only 0.543… That’s 0.014” less than spec. It is suspected to have allowed gas blow by, possibly gas cutting, and be the cause of the 1 in 3 horrible fliers! I added a 10 thou shim, and cast some test drops at 0.554”… not 100% round, but hopefully enough to engage the rifling and eliminate the fliers… I’ll be calling Lee tomorrow, 14 thou under is very poor. With luck, my buddy will confirm the needed accuracy, and go and find a decent whitetail!

I appreciate the helpful hints, suggestions and advice from the many who replied on this thread… there many lifetimes of hard earned knowledge out there, thanks for sharing!


My thanks!

Steve 1
Florence MT.

 

[Grenadier1758]

What does the Lee REAL mold cast when pure lead is used? As @Steve 1 mentions, different alloys will shrink to a different dimension. The Lee mold is designed to cast true with pure lead.

 

[Steve 1]

What does the Lee REAL mold cast when pure lead is used? As @Steve 1 mentions, different alloys will shrink to a different dimension. The Lee mold is designed to cast true with pure lead.

Sadly that was pure lead, I even tried various lead and mold temps… I was still 14 thou under the specified widest / driving band.
Rather frustrating, we went through 3/4lb of Goex 2Fg with testing, some elation, then a flier so despair… an emotional roller coaster!
As I mentioned today, I shimmed the mold by 10 thou, should get field test results tomorrow. This may help, but it’s now oval. 0.554 by 0.543, the mold is still undersized. I may do a Cerosafe impression, that’s super accurate… as in chamber castings.

Cheers!

S1 MT