Engraving / obturation needed for PRB accuracy ?

[roundball]

"...remember to put in that 120 grs first because it would be pretty difficult to pull the brass ball...

Amen...that was the single biggest point of planning & analysis to ensure the ball specs were well undersize and consistently precise before ever loading one.
Tested all that in the shop, and including the use of a CO2 discharger before ever going to the range...

 

[necchi]

Their manual also states to plug the vent with powder to "lay a fuse" to the main charge...LOL.

The linked manual actually say's this on page 17

"Before priming a flint lock, always push your flashhole pick (nipple pick)
through the flashhole into the main powder charge. This ensures a clear passage
for the flash."
Funny how things change when read by different folks,,LOL

 

[Larry Pletcher]

Roundball,
My complements on your work and the time spent working and reporting. I can appreciate your dedication.

Just to add a related issue, we have have long heard that a loosely patched ball may strip the rifling fly off anywhere. In Your work I assume the brass balls are patched pretty tight. They seem to behave as the belted steel balled we tested. Since these have proven to be accurate, they must not be stripping.

So, now here is the question: how does one know if a fired ball strips the rifling? What kind of evidence is present? Maybe this also is something we are told happens with no evidence supporting it.

Regards,
Pletch

 

[roundball]

Roundball,
My complements on your work and the time spent working and reporting. I can appreciate your dedication.

You set the bar awfully high...just struggling to catch up.

Just to add a related issue, we have have long heard that a loosely patched ball may strip the rifling fly off anywhere.
In Your work I assume the brass balls are patched pretty tight. They seem to behave as the belted steel balled we tested.
Since these have proven to be accurate, they must not be stripping.

Correct...I was shocked at how accurate they were...and not some of them, not most of them, but each and every last one of them were like lasers...and I pushed them pretty hard with 100 & 120grns Goex.
The .562" ball and .028" (.056") patch combo I decided on gave a really very tight/snug combo .

So, now here is the question:
how does one know if a fired ball strips the rifling?
What kind of evidence is present?
Maybe this also is something we are told happens with no evidence supporting it.
Regards, Pletch

Old wives tale as far as I'm concerned...never had any strange unexplained inaccuracy problems in the 20 years I've been at it.
One of the classics was "you can't use powerful powder charges in T/C's standard barrels because the PRBs will skip the rifling".
And I personally ran the range tests in T/C .45/.50/.54cal standard barrels to prove that was an old wives tale.
It's why I just began running my own tests rather than just accepting stuff posted in a lot of threads.

 

[Vaino]

Posting an "off topic" reply on one's own topic surely shouldn't happen. Evidently "thinking out loud" is frowned upon?

My premise of "slippage" using the brass balls is open to question, but so is the premise of no slippage. The plain fact is that neither situation can be proved...but that should be why an "unclutterted" discussion is warranted.

The brass ball loads yielded good accuracy, but that's not a reason to assume
"slippage" isn't present... some smoothbore guns do display good accuracy.

I was enjoying this discussion and was very appreciative of your "experiment", so if we could continue w/ a rational, open minded discussion, that would be in everyone's interest. Again, thanks for your efforts.....Fred

 

[Rifleman1776]

"...I'll betcha you just haven't see the patch/rifling engraving..."

Yeah...that's it...I've just over looked it on almost 21,000 shots in the past 20 years ???


It really doesn't matter...the point of the thread is that patch weave engraving, obturation, rifling engraving are obviously not necessary for excellent accuracy...because the solid glass and solid brass balls don't allow any of those things.

Only 21,000 shots? Not a bad start. With some experience things should improve for you. :wink: :rotf:
Really, we often do not notice things we are closest to. I prefer a snug fit that will engrave rifling and patch weave on my (pure, soft) lead balls.
My hunting loads not so much and I don't fret any tiny loss of accuracy.
I happen to have a recovered .440 ball from a deer on my desk in front of me. Completely flat and no patch or rifling marks.
What you are doing with glass, steel and brass balls is interesting. I understand why you are doing this experimenting and hope it proves of value to those who may be forced to give up lead.

 

[cynthialee]

Pick up a ball of steel (or brass) with a piece of cloth in your hand with no more presure than the barrel would hold the ball....the ball doesnt slip does it?

 

[Robby]

Fred, If I understand you correctly, you are saying that as the ball moves forward the patch engaged deeply in the rifling will start to rotate with that rifling, but the ball moving forward, yet stationary in rotation will resist 'that' force of movement and slip inside the patch. You may be correct, there is no way of telling, but with a good tight patch I would think its only a momentary lag before it goes with the program and turns in sync with the patch.

 

[Vaino]

Your analogy of a "hand held" patch and ball is nowhere akin to the explosive force exerted by the hot gases of BP. The inertia of the projectile has to be overcome by the "grip" of the patch....the projectile wants to go "straight" and not follow the twist of the rifling... inertia. The "grip" on a brass ball is only tangental whereas w/ a softer lead ball, the grip is enhanced by a slight tangental flattening and the weave imprint on the soft lead ball. I suspect that the brass ball does encounter some slippage...possibly more but definitely some. Of course this is conjecture until proven whether the brass ball "slips" or not.....Fred

 

[cynthialee]

if the patch is spining then the law conservation of energy says the ball in the patch will start spining eventualy also, maybe it does take an inch or so in the barrel before the ball starts spining, but I highly doubt it

we can only know for sure when some one sets up a 100-150 yard target and shoots it with a brass ball;
if it can hit the target at that distance, there can be little doubt the ball is spining

(or a high speed camera filming the ball exit the muzzle)

 

[Vaino]

Hi Robby...A brass ball inside a lubed patch would depend on only tangental friction to start it's rotation forced by the rifling...is this "grip" sufficient to overcome the inertia of the brass ball or is there "slippage"? I think that the brass ball "sees" a smoothbore and the tangental friction of the lubed patch doesn't supply enough "grip" to force the brass ball to follow the rifling and therefore to rotate. Just thinking "out loud"....Fred

 

[necchi]

Cindy, this is one of those topics that will always have two different sides.
Here's some pictures I took of a ball that was dry loaded and blown out with CO2.
The marks from the fabric and lands that roundball has NEVER seen are clearly seen, :idunno:
How can ya explain to a man that refuses to see??

 

[roundball]

In summary, I found the undertaking to be an extremely interesting project, not only learning and proving/disproving some things for myself, but identifying a readily available alternative to lead PRBs if that ever becomes an issue such as a "lead free hunting zone", a "lead ban", etc.

For me, the ragged hole accuracy of 9/16" solid marbles for practice, and .5625" brass balls for deer hunting...both out of my .58cal TVM Early Virginia...make the .58cal a complete performer to hang on to for a few more years.

And as with any/all tests I conduct, I share the information results as clearly as possible, at no charge to anyone.
The tests are what "I" did, with "my" equipment, "my" components, "my" supplies, my methods, "my" abilities.
There is 'no recommendation' that anyone do this...it is simply information for anyone to draw from or ignore as they fit.

:thumbsup:

 

[cynthialee]

Well I am pretty sure the ball is spining, otherwise I don't think it would have been as acurate as it was, however I will suspend judgement until we get a range report at a distance that we all know a musket can not hit acuratly.

If the brass balls can hit acuratly beyond standard musket range we can be pretty sure it is spining if not we can probably safely assume there is no spin.

As for the lead balls, likely they are being engraved to some degree in Roundballs rifle, but it is just hard to spot. I have looked at pictures of supossedly engraved balls and not been able to see it where others say it is plain as day, but I wear glasses and the eyes are not what they ussed to be.

 

[Robby]

Fred, Okay, I do understand what you are saying. My thinking is that the grip of the patch is sufficient and if any slippage does occur would be a microsecond. No way to prove who is right or wrong in our musing. That is one of the reasons I was interested in what might be going on at one hundred yards. The knuckle ball effect doesn't really come into play till the ball looses quite a bit of speed, at least that was my finding when I experimented with smooth bores some years ago.
I'm a patient man, and when Roundball gets around to it, I sure he will test it out.

 

[necchi]

FWIW, here is the example of "ragged hole" accuracy as defined by some folks.
It's of course at 25yrds and with marbles and the photo is only ment as example of what accuracy is, I'm pretty sure that's a 9" paper plate.

Where as this is what I call ragged hole accuracy, this is 5 shots at 50yrds.

The point is "accuracy" by definition is different things to different people too.

 

[Vaino]

Hi Robby...I do think that the slow twists of RB bbls {1:66} wouldn't be as much of an obstacle for the friction of the lubed patch and smooth brass ball to overcome the inertia....but just tangental friction might not overcome the inertia to start the rotation of the brass ball. Also...the patches shown are not the usual rifling pattern....sonething else is going on. Again, interesting topic and RoundBall is to be complimented on his endeavor and the posting of the results. Yes...100 yds would clarify somewhat, but the question of how much slippage would still exist.....Fred

 

[hanshi]

I think some of us are either forgetting or "over thinking" the fundamental principle under which a longrifle and prb operate. The PATCH gives spin to the ball. No more, no less. If rifling happens to engrave the ball so be it. But it is not in the least necessary for fine accuracy or function. The patch gives spin to the ball. :2

 

[Robby]

Well actually Hanshi, the rifling gives spin, the patch is an enabler, hey, just sayin! :grin:
Robby

 

[gizamo]

What is the brinell hardness of a glass marble or brass ball?

Surely much harder then soft lead. So, maybe we could test titanium to see how much it deforms under low pressure and somehow draw absolute conclusions on how that relates to soft lead in a slow or fast twist barrel, or smoothbore.