The crappy Chappy saga continues...

[Three Foot Johnson]

I've had a Chaparral 1876 .45-75 since '07, and it's definitely earned the nickname "Crappy Chappy". Unbelievably poor QC and ridiculous accuracy problems led me to send it back to Nick Ecker TWICE. The third one was within my capabilities to make it work, but the accuracy problems persisted. I tried bullet weights from 265 - 405 grains, .458", .459", and a few "as cast" at .460"+. I've tried a dozen different smokeless powders, APP, Triple 7, Pinnacle, Black MZ, Goex, Elephant, KIK, and Swiss in different granulations. I've tried gas checked and jacketed bullets. The bore looks good, the crown looks good, there are no tight or loose spots - it just will not shoot well.

 

But, it's better than the first one. The first one shot 2' groups at 25 yards with the bullets hitting completely sideways. Fifty yard patterns were in the vicinity of SIX FEET.

 

I got it out again today and decided to run through a bunch of powders, bullets, and loads again, in the hope that something might work. The worst 5 shot groups were around 16" at 100 yards, and the best around 7". Unfortunately, the "small" seven inch groups weren't repeatable, and opened up to 10-12" the second time around. I got thinking, "I've gone ridiculous on the light end with 265 grainers... what the hell..."

I found a handful of cast 500 grain RN gas check bullets in a box, sized them and loaded them over Black MZ with the bullet seated deeply enough to feed through the action and crimped considerably forward of the upper band. The first five printed a group of 4 1/4". Yeah, here we go again - just got lucky. I loaded up 5 more, stepped outside, and they went into 4 3/8". Hmmm... back to the bench and prepared 5 more, stepped out to the bench, and put them into 4 1/4"... all 15 are under 4 1/2".  Acceptable, barely, and definitely not a paper punchin' Saturday afternoon range plinker, but rather a deer killin', elk slayin', buffalo slaughterin', bear flattenin', lion tamin' elephant killin', dinosaur exterminators.

 

Can't wait for hunting season.

[Pat Riot]

Elementary question but have you ever slugged the barrel? Sounds like the bore is large, perhaps.

[Hardpan Curmudgeon SASS #8967]

Pat, ya beat me to the question...

 

That and what's the twist.  For that matter, how deep is the rifling?

 

 

[Three Foot Johnson]

Bore slugs .4580" - .4583", depending on which opposing set is measured. Lands are ~.4525", so the rifling is just shy of .003". A little shallow, perhaps, but it should be sufficient. IIRC, the twist rate should be 1:20.
Headspace is effectively -0-, as the cases are all fire-formed to the chamber and neck sized only.
I've tried several known alloys from dead soft lead to some that my LBT tester puts at around 25 BHN... might as well be shooting copper solids!
No discernible pattern to the grouping.
No discernible vertical or horizontal stringing.
Magazine tube is not binding in its mount or in the fore end cap. But that brought to mind another odd thing about "fit & finish". After having this one for awhile, I noticed one day something looked a bit odd about the magazine tube cap. There's a slot in the bottom of the barrel where a tab on the cap rotates into and then the retaining screw inserted, but someone assembled this one with the tab just resting on the end of the barrel, so the mag tube was actually about 1/4" from being fully inserted into the action.

[Sedalia Dave]

If you remove the forearm and mag tube is there any play between the barrel and receiver?

[Three Foot Johnson]

Nope, the barrel is tight.

All three of 'em had accuracy problems. It must have just been an inherent thing with Chaparral.

[Hardpan Curmudgeon SASS #8967]

Hm.  No doubt, that is pretty shallow rifling.  Marlin's "Micro-Groove" rifling is only about .002", but they make it work by having a BUNCH of grooves - 12 in the .45-70.

 

You might want to try paper patching.  There is a differing of opinions on this (of course - think Ginger/Mary Ann!), but there is a school of thought that shallow rifling works very well for paper patched bullets.  A friend of mine had similar accuracy issues with an old rifle with a worn barrel - don't recall if it was his Trapdoor or his Peabody - but he did the math and paper-patched a bunch of soft lead bullets and his groups tightened right up.

 

A lot of work for sure... but it's a fun process that can bring good results.

[Three Foot Johnson]

Microgroove rifling is usually quoted as being 12 - 16 grooves .0014" to .0015" deep (14 to 15 ten thousandths, not thousandths). I slugged two of my Rossi .44-40's, and they come in at about .0025" - .0026".

 

From what I can find online, "standard" rifling is essentially everything that isn't Microgroove rifling, although Microgroove doesn't define rifling depth, but rather the process of button rifling rather than cut (Ballard) rifling.

 

From what I could find, .0025 - .003" is more or less standard rifling, and .004" is considered excessively deep. Well, other than muzzle loaders, of course.

 

[Sedalia Dave]

Have you done a chamber casting and measured it against SAAMI specs? Also check to see of the chamber is actually round and lined up with the bore.

 

I have a Uberti pistol with cylinder throats that are oval vice round.  For SASS distances it doesn't matter but for bullseye the group size is not very good.