General discussion > Black Powder Shooting

Sealing round grooves

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hortonstn:
i've tried about everything what do you think? i"ve got a rice 50 cal , a getz 54 ive tried small ball thick patch and large ball thin patch i just can't get the accuracy i can get in a
Green Mountain straight groove 45 and 50 cal these barrels are all 38-42 inches long
i test these benchrest style bagged in the ft.
i'm thinking a round groove barrel can't be used for bench or over the log is this correct?
shooting 60 yds open sights at a 3 inch target with a nickle sized bull
thanks for your thoughts
paul

smylee grouch:
You might want to give the crown a real good polish job and try a 5 to 10 thousands underbore size ball with at least a 20/1000 denim patch. I'm thinking the bore will seal up better and load easier once you get the ball started and down the bore about 5-6 in with a short starter. Also try some different sight styles if your current ones are hard to see consistently.

Scota4570:
I had a round bottom 45 caliber barrel.  The grooves were 0.016 deep and about 50/50 width ratio with the lands.  It shoot poorly.  No patch and ball comb helped.  That includes loads that required a heavy steel ramrod.  I tried thick cushion was under the patched ball too.  Nothing worked.  I scrapped the barrel, that was an effective solution to the problem. 

I do not think it is an issue with the shape of the grooves.  I think the grooves are too deep and too narrow.  A loadable combination that gets enough compression in the center of the grooves is not possible.   If they were made wider and not so deep I bet they would shoot.

To go to another extreme I have used 45 cal cartridge gun blanks to make MLs.  The grooves are only 0.004" deep (only 1/4 the depth of the round bottom barrels).  They have all shot very accurately. 

Others have other, equally valid opinions and experiences. 
 

D. Taylor Sapergia:
I get superb accuracy with round groove rifling using a ball .005" under bore size and a .021" - .025" patch lubed with anything, as long as there's lots of it.  I use a short starter and the hickory rod from the rifle.  I also use charges that some may consider excessively heavy, ie:  65 gr. 3Fg in .40 cal, 85 gr. 2Fg in .50 cal, 127 gr. 2Fg in .62 cal.

Daryl:
hortonstn - We have all heard how easy it is to clean deep, rounded grooves. That is an advantage, especially if you are bench, plank or chunk shooting where there is a lot of time
between shots and bores are wiped between shots. Makes sense that a bore that cleans easily would be an advantage to having identical bore condition for each shot.  This in itself
should be enough to promote deep, rounded rifling for those "accuracy" regimes, if they were also as accurate as shallower square (or slightly rounded) rifling.
I would think ALL BR, plank and chunk shooters would be shooting those deep, rounded grooves.
They aren't, thus there is a reason they all use shallower, square or slightly rounded (we call them square) rifling with sharp corners. They work.
Years ago, I received a barrel from a barrel maker, that was a prototype .50 cal., with .025" rifling depth.  I tried every combination I could think of, yet could not get that barrel to shoot to
my satisfaction.  Prior to that, I had a .45 cal. Bauska barrel that had .028" depth of rifling, that shot very well indeed. I was discouraged by the .50 not shooting well and did not know why,
except perhaps the lands were too wide in comparison to the grooves as I just could not load a combination that filled them well enough.
In the .45 that shot well, I was using a .457" ball and .022" denim patch.  As the bore was .448" plus the groove depth, I had .504" depth to fill. The .457" ball + the .022" denim went only .501"
which technically did not fill the grooves, but it shot well.
Here's a 5 shot, 25 yard group with that barrel, produced back in the mid 70's. lol - I could see well and didn't shake as much as I do today.



Now, here are the groups shot with a Hugh Tonges barrel with .025" rifling, with the load combinations listed on them.
Now, they aren't worthy of being BR quality, or even chunk, but these were not worked up, just selected and shot with a rifle I have never shot before.
The sights were typical V and front blade. Single bag on a 50yard target.
So- rounded grooves can shoot decently, especially for a hunting rifle.

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