myth- 1-32 twist won't shoot RB [Archive]

longbow

05-07-2012, 08:50 PM

Pretty good looking groups George.

I think you are right on with the comment about tight fitting ball and patch. I think the concern with patched round ball and fast twist is skipping the rifling at higher velocities. Since it is not to hard to get up around 2000 FPS it is conceivable that shallow or rounded rifling may allow skipping at high velocities especially if the fit isn't real tight.

If the ball and patch grip well enough they should shoot fine. While the extra spin may lead to more wobble if the sprue is not dead center I am not sure it would be a big detriment.

There are folks shooting bore size RB's from rifled shotguns with similar twist rates getting very good results. In fact I borrowed a rifled Remington 870 with 1:36" twist and got several 2" groups at 50 yards with 0.735" RB's. Considering the recommended twist is about 1:110" for a ball that size, not too shabby.

I don't think there are many absolutes in this game!

Good shooting!

Longbow

HARRYMPOPE

05-07-2012, 09:27 PM

Pretty good looking groups George.

If the ball and patch grip well enough they should shoot fine. While the extra spin may lead to more wobble if the sprue is not dead center I am not sure it would be a big detriment.

Longbow

I tried not orienting the sprue on three groups and saw no difference.it surprised me.

George

longbow

05-08-2012, 12:08 AM

That is a bit surprising at .50 cal size but maybe not so much in larger ball since the sprue is about the same size regardless of ball diameter.

In .32 cal. the sprue weight, nub or tangential, should be a concern as it would be a higher percentage of ball weight.

Is your mould tangential cut of or does it leave a nub? The tangential cutoff style is likely just a few grains off while some that leave a nub leave a significant nub.

I suppose one could file off the nub and weight the lead to see just how much there is. It just may not be enough to worry about. I will have to try that! I have several RB moulds from 0.375" to 0.735" (hmmm... never noticed that coincidence of same numbers, different order before). Some are tangential cutoff and some leave a nub.

I have always tried to keep the sprue up as close to center as I can. It seems logical but maybe not necessary.

A bigger concern is probably not having the sprue oriented to be trapped between patch and rifling. That would probably affect sealing and ball centering in the barrel.

Something else to test. I will check 0.375", 0.440", 0.490", 0.662", 0.690", 0.715" and 0.735" for "nub" weight at least for those that are not tangential cut off. Where is my file?

Longbow

FL-Flinter

05-08-2012, 09:13 AM

"Quality". That's the one word to sum it all up. Junk in, junk out, good in, good out ... it's the way of the world. There's several other things going on but I can assure you, if you used crappy balls and inconsistent powder charges, you'd see larger groups/fliers. Of course, there's a lot of other factors that come into play such as, "What is the value of 'tight' patching?" "Tight" is a relative term because what may be "tight" to me would be "loose" to someone else and such a difference in relative perception can make or break a load/gun.

I'm always amazed at how many times people will the lack of accuracy blame on rifling twist when in reality it's crappy consumables, they aren't loading consistently or ... the list goes on. Longbow seems surprised at 2" groups from the 1:36 12ga, doesn't surprise me at all because whatever the load combination was, it worked and not to be confrontational but the same can be done with the right load combination and quality consumables in a smoothbore too. A while back a client provided me with a 0.458” microgroove 1:32 twist centerfire cartridge gun barrel blank for an underhammer build, he shoots paper-patched round balls quite well with it. I've also built some match rifles in 36, 40 & 45 calibers using twist rates from 1:66 to 1:72 that shoot exceptionally well. The issue of "optimum" concerning twist/caliber is based on the generalities of what the gun "should" be capable of doing with an "assumed" powder charge range so as to provide the "most forgiving" conditions. There's always exceptions to everything but the general rule of thumb is that good quality round balls will typically be more forgiving with slower twist rates. If you get some bubba beating the ball into the muzzle with a three-pound mallet and another just tossing the powder down the bore without concern for consistency in loading and/or measure, chances are good that neither will be taking home the blue ribbon.

HARRYMPOPE

05-09-2012, 01:39 AM

Is your mould tangential cut of or does it leave a nub? The tangential cutoff style is likely just a few grains off while some that leave a nub leave a significant nub.

A bigger concern is probably not having the sprue oriented to be trapped between patch and rifling. That would probably affect sealing and ball centering in the barrel.

Longbow

#1-Lyman mold that leaves a pretty big nub.

#2-I haven't so far had a ball feel tight but the sprue nub shuld make it load harder if it was to the side of the rifling.

I am off tomorrow for an early AM shoot and then a PM shoot to see if it holds up.maybe i was just lucky so far.I took a few (30)and rolled them in a small container for about 5 minutes and the sprue nub is hardly visible.

George

HARRYMPOPE

05-09-2012, 01:48 AM

There's always exceptions to everything but the general rule of thumb is that good quality round balls will typically be more forgiving with slower twist rates.

What do you define as "foregiving" ? And what is it more tolerant to? Bad balls- inconsistent charges ETC ? I had always thought the slower twist just let you keep accuracy at higher velocity with RB.And why is that if its true?

George

missionary5155

05-09-2012, 05:56 AM

Good morning
I totally agree with the Quality statement FL- Flinter wrote. A ball that has a void inside or out of round will wobble no matter what the twist. Add a faster twist and the wobble just gets worse. Years ago I saw the Globe Trotters do the weighted basketball roll. Slow roll it would was funny to watch .. roll it fast and it would bounce. It would be interesting to see a high speed film of out of round and a drilled round ball going down range.
Mike in Peru

FL-Flinter

05-09-2012, 10:52 AM

What do you define as "foregiving" ? And what is it more tolerant to? Bad balls- inconsistent charges ETC ? I had always thought the slower twist just let you keep accuracy at higher velocity with RB.And why is that if its true?

George

Sorry, didn't mean to be so vague. "More forgiving" in the manner that slower twist will "typically" tolerate wide variations in velocity - not inconsistency in loading or crappy consumables but for example...
A given .50 x 1:48 will shoot equally well in a powder charge range of say 65-75 grains. Another .50 but with 1:66 twist may shoot equally well in the 50-100gr charge range. Based on my own experience and feedback from others, it's "typical" that bores of a given diameter will have a much narrower powder charge tolerance range as the twist rate increases (faster) and the maximum velocity at which consistent accuracy can be maintained will be lower. Again, this is "typical" but there's always the "exception".

None of that goes without say that there must be consistency in loading and quality in the consumables too. A slow-twist bore may be more finicky about loads than a faster-twist bore if one is using poor quality consumables. Inconsistency, improper loading techniques and/or crappy consumables are more often than not the cause of most grief.

longbow

05-09-2012, 08:31 PM

My impression of the concern with fast twist and patched RB is that if pushed hard the patched ball may skip the rifling.

Greenhills was/is the basic starting point to estimate twist required for a given length of boolit... subject to some conditions. If you look at the Greenhill formula and apply it to a 0.490" round ball you get a required twist of 73.5" and most round ball specific twists for .50 cal run from about 1:60" to 1:70" in my experience.

For 12 ga. you get 109.5".

This is supposedly the minimum twist rate to provide good accuracy. A faster twist is not necessarily a bad thing as long as the projectile can tolerate the rotational acceleration and not skip rifling. I doubt a .50 cal. muzzleloader with 1:32" twist, "snug" patched RB and reasonably deep rifling would be a problem with skipping rifling or "overstabilizing". I think George has demonstrated that.

Is it possible to "overstabilize" a ball. Well, I can't say but I agree with the comment that if there are any imbalances in the ball then faster twist will most likely lead to more "wobble" and so inaccuracies which would be exaggerated at longer ranges.

It is certainly possible to understabilize and for example my .50 cal. Hawken with 1:66" twist would not shoot a 370 gr. Maxi ball with any accuracy at all. Fit was good but they were sideways before 100 yards. I gave the mould to a friend who has a 1:48" twist gun and it works fine for him.

I was surprised by the 12 ga. 1:36" twist providing rather good accuracy with 0.735" round balls because the rifling was quite shallow, I was pushing the balls pretty hard at around 1500 FPS and the twist is 3X what is required for that size round ball. I would not have been surprised to have balls skip the rifling and go wild but they did not.

Would long range accuracy hold up with a much faster twist than required? Most likely depends on fit and quality of components. If the ball is "perfectly" round and with no imbalances would extra spin hurt? I doubt it. In reality nothing is perfect so I suspect groups would open up some.

If I had to choose, I would go with a faster than required twist and accept that top end velocities might not provide best accuracy for round balls, but conical boolits could also be used.

Longbow

HARRYMPOPE

05-09-2012, 09:53 PM

I went out this AM and shot three 5 shots groups at 50 and one at 100 yards In a bit of light breeze. The 50g of Pyro "P"/.495 Ball load shot 1.1"-1.8"-1.6" at 50 and the 100 yarder had the first go high then the last four go 2.7" total group size was 4.2"
More 100 yard testing to be done.I will try driving them harder to see what happens at 100.

George

FL-Flinter

05-10-2012, 09:58 AM

My impression of the concern with fast twist and patched RB is that if pushed hard the patched ball may skip the rifling.

Something has to mechanically fail to cause "skipping"/"stripping", I can't tell you how many times such was blamed yet the recovered patches were in perfect condition and the patch/ball combo was not of insufficient diameter for the bore. Can it happen, absolutely. Does it happen as much as claimed, nope. More often than not, the problem with too-much spin, instead of correcting for the blemishes in the ball, the blemishes become amplified causing it to go wild.

The Greenhill formula is designed to get one in the ballpark for an elongated blunt-nose conical bullet and at that it's always best to go a wee bit faster on the twist than what's calculated. Then again, there are exceptions where one can push a long heavy .40 conical very accurately from a twist that's at least 8" too slow according to all the calculations and "typical" performance assertions.

I'm not flaming you because it's used a lot ... but the use of the term "overstabilize" really burns my bacon! One cannot make something "too-stable", it's either "stable" or "unstable" and therefor please leave the use of the term "overstabilize" to those who don't have a dictionary.

It is certainly possible to understabilize and for example my .50 cal. Hawken with 1:66" twist would not shoot a 370 gr. Maxi ball with any accuracy at all. Fit was good but they were sideways before 100 yards. I gave the mould to a friend who has a 1:48" twist gun and it works fine for him.

Yep. But, in most cases you'll find that the limitation of velocity combined with the still way too-slow 1:48 twist will create a point at which the bullet looses stability. In many cases that happens somewhere around 60-85yds where, often in a matter of feet, said projo can go from printing decent groups to being totally wild. What I tell clients is that the consistency should be proven before it's considered reliable - if they can keep 30+ shots within a reasonable group size without any "fliers", then it's consistent, if you get fliers, it's not consistent. That's just experience - I put three .50 conicals from a common production mold out of a common production gun within 1.5" @ 100yds, the next 5 or 6 didn't even come close to the paper let alone the bull.

I was surprised by the 12 ga. 1:36" twist providing rather good accuracy with 0.735" round balls because the rifling was quite shallow, I was pushing the balls pretty hard at around 1500 FPS and the twist is 3X what is required for that size round ball. I would not have been surprised to have balls skip the rifling and go wild but they did not.

This raises several questions starting with the load. What is it? How is it constructed? What's the relationship between groove diameter, bore diameter, ball/wad/sabot? All that is questionable in that the ball may not have even come close to picking up the full rotational velocity according to the 1500 fps/1:36 twist. Then again, a proper fitting load combo and a high-quality ball can surely handle the full rotation without any problem. Point being, the example must be systematically dissected so as to figure out the reason for the result. Not only is such interesting, it's also a great excuse to shoot more in the name of "scientific discovery". :bigsmyl2:

In theoretical practice, if one had an absolutely perfect sphere and could maintain such throughout the loading & firing sequence, it would perform no better with spin as without. A conical projo must have spin or tail-drag to maintain stability. Over-rotating an imperfect round ball is as detrimental as under-rotating a conical.

FL-Flinter

05-10-2012, 10:04 AM

longbow

05-10-2012, 09:09 PM

FL-Flinter:

I can tell you that my .303 Lee Enfield with 1:10" twist will swage rifling grooves wider in the boolit than the rifling lands are wide when using ACWW and some loads. With heat treated boolits this does not happen ~ determined from examination of recovered boolits.

In those cases, the rotational acceleration produces more stress in the lead than it can handle. Can't say I have had any strip but they have certainly suffered from swaging by rifling, so "skidding" I'll call it. Accuracy of course was rather poor.

Same load with heat treated boolits shoots fine and no sign of "skidding".

I am not good enough with the math but apparently it is possible to over spin a bullet (if you don't want to call it overstabilizing). Look here:

http://www.nennstiel-ruprecht.de/bullfly/index.htm#Contents

and here:

http://www.nennstiel-ruprecht.de/bullfly/fig15.htm

Does it happen at normal velocities and rifling twist? I really couldn't tell you.

I certainly agree with you that spinning faster than necessary to produce required stability/accuracy can magnify any imbalances due to imperfect boolits/balls but I think you would have to test boolits with known imbalances and shoot many groups with different twists to be able to determine just how much imbalance at a given twist rate becomes noticeably detrimental to accuracy.

As for the 12 ga. RB load, it was assembled using a plastic gas seal, hard card wad column and ACWW 0.735" RB naked all over 36 gr. Blue Dot for the most part. I did go to 38 grs, but found the recoil punishing in a light gun. I probably shouldn't have included a velocity as it was a guesstimate not chronographed.

The gun was a Remington 870 with 0.727" groove diameter and 1:36" twist. If memory serves rifling was about 0.003" deep but I would have to look it up.

The basic point was that the twist was much faster than typical round ball twist and the rifling was rather shallow yet accuracy was quite good and a couple of recovered balls showed a nice rifled "belt" around their equator. No stripping or "skidding".

Since this discussion is about muzzleloaded patched round balls in relatively fast twist rifling I will leave the boolit and shotgun discussions alone.

I will be looking forward to George's 100 yard tests at higher velocity. He should be able to reach around 2000 FPS with 100 gr. BP loads. It will be interesting to see how accuracy holds up with the 1:32" twist.

Longbow

HARRYMPOPE

05-10-2012, 11:08 PM

Harry,

Slight breeze and even the thermal currents caused by the heating of the ground surface by the rising sun can move projo's around in flight, especially round balls. Best time to shoot is in zero wind and with no or at least minimal ground heating/cooling. I try to do the proving work first thing in the morning before the sun clears the tree canopy and conditions are as stable as possible. Keep us posted.

My load test shooting with RB is about 6AM.I shoot and run Cast bullet antique military rifle matches and wind is something i am all to familiar with.You are correct and wind often gets overlooked.You have to have flags(if legal in you matches) to be serious and learn to shoot in wind as it is seldom calm during range time.

With Mothers Day weekend i probably wont shoot my 100yard stuff until Monday AM.I ran out of balls and need to cast up more.I shot 200 .495 RB's this last week.So far with the 100g charge its been 2" at 50 yards and the groups are "hollow" with no inclination of wanting to cluster.

george

HARRYMPOPE

05-13-2012, 10:43 AM

worked up to 80g of Pyrodex "P" this AM and accuracy remained the same at 50.Groups ran 1.25-1.75" for 5 shots.

George

longbow

05-13-2012, 12:00 PM

George:

Have you slugged your barrel?

I am curious as to land and groove diameters. I was just reading up on The Great Plains Hunter and the write up says it has "1-in-32" shallow-groove twist ". I am wondering how shallow is shallow.

My CVA Hawken runs 0.495" bore and 0.510" groove (if memory serves) so only about 0.007" to 0.008" rifling depth. I figured that was fairly shallow for patched round ball but it also seems common for replica guns.

I may be wrong here but my understanding is that rifling was cut more like 0.010" to 0.012" deep for PRB in the old days and I see some higher quality barrels with PRB twist running up to 0.016" deep.

Point being that you are getting good results using "shallow" rifling and fast twist. Kinda makes one wonder.

It will be interesting to see how your 100 yard tests go.

What maximum charge do you plan?

Longbow

HARRYMPOPE

05-13-2012, 03:31 PM

i haven't slugged it yet but the combo is much tighter in my GP than my 1-66 TC Pennsylvania Hunter.
100 yards shooting was about 4" but it was windy so didn't waste too much powder and hope for a better day.
I will try to go to 100 with Goex FF next time out.I prefer black over "subs" but i had some Pyrodex in the back of the shop i was trying to get rid of and it seems to be working.

George

HARRYMPOPE

05-15-2012, 10:24 PM

George:

It will be interesting to see how your 100 yard tests go.

What maximum charge do you plan?

Longbow

100g Pyro RS at 100 yards and 50 yards.Notes on targets.

http://i1105.photobucket.com/albums/h352/LINOWW/PICT1965.jpg

http://i1105.photobucket.com/albums/h352/LINOWW/PICT1964.jpg

http://i1105.photobucket.com/albums/h352/LINOWW/PICT1966.jpg

longbow

05-16-2012, 12:15 AM

Looks pretty good to me. Who says 1:32" twist is too fast for balls then eh?

That ball must be scooting along pretty good with 100 grs, of Pyrodex behind it.

Live and learn.

That was an interesting test (maybe not yet over), thanks for sharing and posting results.

Longbow

FL-Flinter

05-18-2012, 11:59 AM

Longbow - again, please accept my reply as informational, not a flame or otherwise. It's just a discussion.

sta·ble [stay-buhl]
adjective, sta·bler, sta·blest.
1. not likely to fall or give way, as a structure, support, foundation, etc.; firm; steady.
2. able or likely to continue or last; firmly established; enduring or permanent: a stable government.
3. resistant to sudden change or deterioration: A stable economy is the aim of every government.
4. steadfast; not wavering or changeable, as in character or purpose; dependable.
5. not subject to emotional instability or illness; sane; mentally sound.

Thus, something is either "stable" or "unstable" - there's no other choices, either it is or it ain't and if it ain't, it's "unstable", not "overstable".

The parameters of stable flight for an elongated conical projectile are a whole world apart from the parameters of stable flight for a sphere (round ball). As stated earlier, a "perfect sphere" does NOT require any rotational velocity creating gyroscopic stabilization in order to maintain stable flight. The issue is that we're not shooting "perfect spheres" but somewhat "less-than-perfect" RB’s (Round Balls).

In reference to shooting RB's, we must assume the RB's themselves are of reasonable quality meaning they don't have excessive gas voids, slag inclusions, wrinkles, lopsided sprue's and haven't had the bejeebers beat out of them during loading. Therefore, such RB's require a minimum rotational inertia about their axis in order to stabilize them in spite of their minor imperfections.

Now we'll make it real simple rather than me digging out all the theoretical statements and calculations. Go swipe a toy top or gyroscope from your kid, or in my case grandkid. Spin it as fast as you can and let it go on a hard smooth surface. As long as the rotational inertia is sufficient to overcome the flaws, it'll remain in a stable position - however, as the rotational inertia degrades, you'll see it start to oscillate in a gradually increasing circular motion until looses all control and goes wild. If you were to temp a visit to the local ER or morgue, you could hook that same toy up to something like a high-speed router and see the opposite end of the spectrum where the rotational velocity will increase to the point where it goes flying or blows apart in pieces from a structural failure.

The same thing happens with RB's. Spinning too-slow and the rotational inertia is insufficient to counter the flaws. Spinning too-fast and the flaws are amplified causing instability and the ball goes wild. The better the quality of the ball, the more spin it can take without going wild but on the other side, the same high-quality RB does not need to spin very fast to maintain stable flight.

Elongated conical bullets are not capable of stable flight without the correct amount of rotational gyroscopic stabilization being applied to it. Once the rotational inertia exceeds the amount required for the projectile to maintain stable flight, the flight becomes "unstable" not “overstable”.

KCSO

05-18-2012, 12:21 PM

ANY twist will shoot round balls if you get the patch and powder charge right. The question is what use is a 50 caliber round ball shot with 40 grains of powder for hunting big game, and that is where the twist thing started. Go back to John Baird and the whole slow twist heavy charges business of the late 60''s. We all recognised that a 1-48 twist would shoot well but we had the idea that you needed to use 120 grains of powder to kill anything and it took years for some folks to grow up. I have shot round balls sucessfully fron 1-20 twist in 45-70 for years and this is a real squireel getter fro me. Accuracy seems to fall off after about 20 grains of powder or so. In a 1-32 twist flint Jaeger I was still getting good accuracy with 65 grains of FFg and it worked just fine for short range deer hunting.

HARRYMPOPE

05-18-2012, 10:55 PM

I shot my 100g Pyro RS today at 100 yards.Wind wasnt very friendly but i shot my 2 cavity .495 mold against Hornady .495 Swaged balls.My bullets grouped about 3.5" (both groups were only about 2" tall and horz. from the wind)and the Hornady never went under 5".Both miked .495 and tested teh same BHN on my Cabine Tree tester.It needs another test in calm conditions.

George

FL-Flinter

05-19-2012, 07:04 AM

Longbow -
I can tell you that my .303 Lee Enfield with 1:10" twist will swage rifling grooves wider in the boolit than the rifling lands are wide when using ACWW and some loads. With heat treated boolits this does not happen ~ determined from examination of recovered boolits.

Likely it's the free-bore and/or forcing cone length combined with the velocity of the bullet. The amount of pressure required to break the bullet free from the case mouth determines the velocity at which it's engaging the rifling, if it's moving fast enough and the bullet is not hard enough to withstand the forces associated with going from straight forward to being forced to rotate, the result will be as you describe. Likely the bullets have a relatively small amount of bearing surface as well which doesn't help either because the smaller the bearing surface, the higher the forces on what does engage.

In a muzzleloader application, the rifling is being engaged upon loading (or at least should be) so there's no free-bore or forcing cone issue to deal with. When talking PRB's, if the patch/ball combination is sufficient to properly engage the rifling, "stripping" cannot happen unless there is a major structural failure of the patch and/or ball and there's no way the patch will survive intact.

As for the 12 ga. RB load, it was assembled using a plastic gas seal, hard card wad column and ACWW 0.735" RB naked all over 36 gr. Blue Dot for the most part. I did go to 38 grs, but found the recoil punishing in a light gun. I probably shouldn't have included a velocity as it was a guesstimate not chronographed.

The RB being around 576gr, depending on the exact parameters of the load, gun/load interaction and barrel length, most likely the velocity is closer to 1300 fps. The 0.735" balls are likely oversized by 0.006"-0.008" depending on the exact parameters of the barrel you have so I hope you've carefully checked for excessive pressure signs? Have you run a 20 round string at a 100yds to see what kind of group it'll produce?
Mark

longbow

05-22-2012, 10:41 PM

You are absolutely right FL-Flinter, I overestimated the velocity for the 0.735" RB load. I should have checked before typing.

The load I based my load on was a published and pressure tested load developed by Precision Rifle for their 610 gr. "Piledriver" full bore slug. They list from 36 to 44 grs. Blue Dot at pressures from 11,299 PSI (for 38 grs.) to 12,359 PSI for 44 grs. They list 1374 FPS for the 610 gr. slug over 38 grs. of Blue Dot.

Precision Rifle did not provide details on hull or primer.

No, there were no pressure signs at all but I did not load beyond 38 grs. of Blue Dot because recoil was a little distracting with a light gun and no extra padding. I loaded up several lighter powder charges working up to the 38 grs. and found that was as much fun as I wanted so did not go beyond.

Before loading I took a 0.735" RB (ACWW) and tapped it into the barrel from the forcing cone to get a feel for starting force required. It was much less than I had thought. In fact it started with very little force ~ there is not much meat around the equator of a ball so not much lead to displace even though it is oversize. Also, my reasoning was that not only is the RB lighter by about 35 grs., it has much less bearing surface than a full bore cylindrical slug and I was using considerably less than the max listed load. I also compared the load to other published loads using similar weight shot and slugs to make sure they were "reasonable".

The rifled gun was borrowed and I only shot at 50 yards. I had shot several groups from my smoothbores before shooting the rifled gun so was low on ammunition and I was getting a bit sore from recoil so likely wouldn't have done well at longer range even if I had enough ammunition to carry on.

Longbow

FL-Flinter

05-30-2012, 03:06 PM

You are absolutely right FL-Flinter, I overestimated the velocity for the 0.735" RB load. I should have checked before typing.
...
Before loading I took a 0.735" RB (ACWW) and tapped it into the barrel from the forcing cone to get a feel for starting force required. It was much less than I had thought. In fact it started with very little force ~ there is not much meat around the equator of a ball so not much lead to displace even though it is oversize. Also, my reasoning was that not only is the RB lighter by about 35 grs., it has much less bearing surface than a full bore cylindrical slug and I was using considerably less than the max listed load. I also compared the load to other published loads using similar weight shot and slugs to make sure they were "reasonable".

The rifled gun was borrowed and I only shot at 50 yards. I had shot several groups from my smoothbores before shooting the rifled gun so was low on ammunition and I was getting a bit sore from recoil so likely wouldn't have done well at longer range even if I had enough ammunition to carry on.

Longbow

I wasn't busting on you about the velocity, just wondering if you came up with some kind of secret mojo :wink:

Reason I asked about pressure signs is because for some reason I was thinking shoving that oversize ball into a smoothbore ... you're right, even if the rifling is shallow the grooves are still going to reduce the friction. If you can barrow it again, I'd appreciate knowing how they print at 100yds.

IIRC, I was burning 42gr of Blue Dot under my PRB loads ... know what you mean about recoil, they weren't so bad in the single-shot I built just for them but they were absolutely brutal in the OEM composite stocked Moss 500, even the factory loads I sell with an undersize RB in a plastic wad kick bad in that gun but they shoot good. I forgot just how nasty that gun was until I had client who wanted a replacement stock and I didn't have on on the shelf so I took the one off my own gun and put that nasty plastic thing back on ... Glad you reminded me, I'm fixing to cut some underhammer blanks this afternoon and as long as I got everything out... ;-)

longbow

05-30-2012, 08:49 PM

Nope, no secret mojo here! I wish I had some to use occasionally.

I shudder to think of shooting that light gun with any more Blue Dot than the 38 gr. charge I peaked at. As mentioned, no pressure signs but lots of shoulder bruising (and maybe brain) from recoil.

A heavier gun and/or more recoil protection is definitely in order at least for me!

I have thought about asking if I can borrow it again to try longer range but I have not had time to do much of any shooting for a while now so I just have not got to it.

The recovered balls looked very good with crisp sharp rifling so I am betting they will do okay at longer range but without actually shooting them that is just a guess.

My original goal was to try to get a "modern Paradox" gun or at least similar performance and accuracy with a smoothbore. While the Lyman manual claims their Foster slug can produce 4" groups at 100 yards I have as yet to get under about 8" groups at 50 yards with it. In fact it is my standard for poor accuracy. I have loaded to exactly the Lyman manual recipes with no success, filled the hollow base, cast out of wheelweights, different loads and wad columns and the only way I got reasonable accuracy from it was to paper patch it to bore size. That worked not too bad. However, that is a whole other discussion.

I tried the round balls and even out of my smoothbores they did as well or better than most "slugs" of any style with few exceptions. A few slugs like Brenneke and Gualandi with attached wads have done well along with my home made clones but most hollow base slugs gave mediocre to poor accuracy, for me anyway.

Most of my shooting has been to 50 yards while I worked on trying to get decent groups. Unfortunately I have not had much time to get back out and do more testing. When I do I will ask if I can borrow the Remington again and I will take extra padding so it isn't as painful this time. I will also try chronographing to see what actual velocity I am getting.

I still have not filed the sprue off balls yet to see how much imbalance they might cause. I will weight before and after to see how much weight is removed. I am betting not significant for large caliber over .50 but maybe for my 0.375's and smaller. I will see if I can get that done shortly even though it is probably of little interest now. I am curious though ~ sprue position, does it matter?

Longbow

longbow

05-30-2012, 10:53 PM

Okay then I finally got to it and filed off a sprue.

It turns out that most of my round ball moulds have tangential cut of so no protruding stub of lead. The only moulds I have with a significant sprue protrusion are my Lyman moulds and the 0.690" appeared to have the most obvious protruding sprue so I used that.

Weight before filing = 476.6 gr.
Weight after filing = 474.0 gr.

So the sprue lead weighed about 2.6 grs.

This is a bit subjective in that I filed by eye and it appears that the circumference of the ball about meets the bottom of the sprue plate so the actual "extra" lead is quite small.

I have to guess that 2.6 grs. is not going to have a huge effect on anything but but very small caliber balls (and maybe very fast twist) assuming the sprue is the same size so larger percentage of weight. I have to think that the interference of the sprue if loaded to be against the bore would have a larger effect than 2.6 grs. of imbalance a little off center.

Having said that, it also makes the most sense to me to load with sprue up or down as close to center as possible... just because it seems like the right thing to do if nothing else.

FWIW

Longbow

eaglesnester

11-16-2012, 11:05 AM

I will chime in here with my 2cents worth. I also own a Great Plains Hunter with 1 in 32 twist. This rifle has shallow rifling .008. It shoots RB just fine. My BP shooting buddy and I were out to the range one day and we got on this very subject about why would or why not would a PRB shoot in a fast twist barrel? Neither one of us knew. I came across one answer a few days later on the internet. Generaly speaking some rifles with fast twist have deep rifling? The speed of the ball and patch going down the barrel and the fast rotation causes the patch to tear. When this happens U lose your windage and the ball starts to bounce in the bore thereby destroying accuracy. This may not happen with shallow rifling, .008 which the Lymen GPR has. Now when U add factors such as ball imperfections and gyroscropic effect on a fast spinning ball U have the potential for decreased accuracy. I should think as other posters have said that 65 grains of Black Powder should just about do it and not impart too fast a muzzle vol in a 50. Next time I am on the range I will try a load of 75 grains in my 54cal Lymen Great Plains Hunter with PRB.
What say all of U?

Cheers & Tighter Groups: Eaglesnester