Hard starting with roundball

[bioprof]

I tried my new 75 caliber smoothbore out for the first time today, and was using .735 roundballs with pillow ticking patches. The barrel is an octagon to round from Tennessee Valley Manufacturing. I literally had to hammer the ball/patch combination to get it to start. Once it started, it went down the barrel without too much problem. After the second shot, I tried a roundball without a patch and it practically fell down the barrel. Am I using too thick of patches? Could this barrel be choked?

 

[paulvallandigham]

Always measure the bore of a new barrel before ordering any ball or patch. Don't ever trust what the manufacturer, or gun maker says, or marks on the barrel for " caliber ", or gauge. Some are undersized, and others are overbored.

Yes, your barrel may be choked. ONly measuring it with calipers will answer your question.

 

[benvenuto]

suggest you check the patches with a micrometer to see how thick they actually are. I'm in favour of using the thinnest possible patch for the job - i get "handkerchief linen" from the local fabric store which is 0.010 inches thick and very stong.

Is the barrel crowned?

 

[roundball]

I tried my new 75 caliber smoothbore out for the first time today, and was using .735 roundballs with pillow ticking patches.

I literally had to hammer the ball/patch combination to get it to start.

Am I using too thick of patches?

Could this barrel be choked?

It might be helpful if you checked the dore diasmeter, and the diameter of a couple dozen cast balls to check for variance.

When I forst got a .62cal GM smoothbore, I had ordered some .600 cast Warren balls...got to the range and if there had not been a piece of 2" x 4" laying around I never could have started one and the accuracy was poor due to distoring the ball of course.

Got home and my findings with a dial caliper were:

1) GMs .62cal bores are actually .610s...(confirmed by calling GM);

2) The Warren cast balls varied a few thousands all over the place;

Tried a few .595s with .018" pillow ticking and they fit OK...then found .600s from Eddie May in GA were excellent with .015" Oxyoke patches and settled on those.

Personally I don't like thin patches perferring .018" pillow ticking as my goal with all patch/ball combos so there's no worry about burn-through and because they hold more lube than thin patches...but in .62cal GM smoothbore barrels an .018" is simply too tight with a .600 ball.
I have another identical GM barrel with rifling added by Ed Rayl and it use an .018" pillow ticking just fine.

I'd suggest trying to get a dial caliber involved and it'll shed light on where the problem is...

 

[Mike Brooks]

If I were going to shoot RB out of a true .75 bore I'd be using a .730 ball and .018 patch.
In your case you might try a .015 patch, that may help. Lube with murphy's oil soap (liquid type)cut by about 10% rubbing alcohol .

 

[J.D.]

If I were going to shoot RB out of a true .75 bore I'd be using a .730 ball and .018 patch.
In your case you might try a .015 patch, that may help. Lube with murphy's oil soap (liquid type)cut by about 10% rubbing alcohol .

I get excellent accuracy with a .715 ball and .018 patching in a .748 bore. And it thumb starts. No mallet or short starter necessary.

IMHO, smaller balls and thick patching are the way to go in smooth bores.

The patch only holds the ball centered in the bore, so's there is no real need for rifle tight patch/ball combinations.

If your bore is, indeed, .750, you only have .015 clearance, so even with .010 patching, there won't be enough crush to allow easy starting. Keep in mind you don't have grooves in that barrel to take up some of the extra thickness of the patching.

A good rule of thumb to get a starting patch thickness/balldiameter is to subtract the ball diameter from bore diameter,divided by two=patch thickness.

.750-.715=.035/2=.0175 so a .018 thick patch with a .715 ball fills the bore, with a little crush to hold the ball in place.

If ya gotta have a tighter combination, a .020 patch with a .715 ball should start pretty easily and provide good accuracy.

.750-.730=.020/2=.010

IMHO,a .010 patch won't compress enough to allow easy starting of such a tight combination.

 

[bioprof]

The bore measures .753 plus or minus .0015 (my calipers aren't very precise). The balls range from .733 to .738, so I guess I just need to find some thinner patches or go with .715 balls and pillow tick patching.

 

[paulvallandigham]

Bioprof. I would suggest sorting those balls by diameter and by weight, so you get the best accuracy. weight can be up to 2% of the total weight of the ball, which will be substantial, without affecting adversely the accuracy. But, you need to be within plus or minus .002" with the diameter to insure consistent performance and accuracy. That will also affect your choice of patch thickness. Use and OP wad between the powder and PRB, or a filler, to seal the gases behind the PRB. That allows the lube in the patch to grease the barrel only, instead of being consumed keeping the patch from burning from the large powder charge.

 

[Joel/Calgary]

bioprof,

In the mean time, you might try the .735 balls bare (maybe lubed) with your normal shot-load wadding. Many have had good results with this - see Bob Spencers's site[url] http://home.insightbb.com/~bspen/[/url]

Joel

 

[md2020]

Gentlemen- i have a GM 62 and I had some 600 i was determined to shoot-with 80 gn 777, i put a 1/8 hard card down, then a 1/2 vegitable wad just below the muzzle--place a naked ball, sprue down on top of this and shoved it down.. then a little card on top of that.. it shoots as well as a patch, as best i can tell. Anyone tried that??

 

[Rebel]

Car54 where are you? :grin: Sorry, had to do it. Yes i have done exactly what you describe and it works fine.

 

[DrTimboone]

Me too, except I put the sprue up.... :v superstitious :rotf: