myth- 1-32 twist won't shoot RB

[longbow]

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/bul...x.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]

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]

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]

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]

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]

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/...W/PICT1965.jpg


http://i1105.photobucket.com/albums/...W/PICT1964.jpg


http://i1105.photobucket.com/albums/...W/PICT1966.jpg

[longbow]

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]

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]

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]

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]

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]

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]

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

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]

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]

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]

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

[MaxJon]

I shot a mates GPH at 50yds with the Lee .495 PRB and 50gns of FFFG and it grouped 2" or better all day! A light load i know but great fun shooting. Anyone thought of putting the Lyman peep sights on for better sighting of the bullseye target. I will be putting a deposit on a GPH very soon. (cant wait to get one) The Lyman peeps will be a must for it too, as it will be a range/comp. gun for me! Anyone tried the Lyman #504617 Maxi ball in a GPH? Interesting read, keep the info coming Harry!

[HARRYMPOPE]

I have shot only one conical( the 395g Lyman 50 GP) and it groups well.

George

two targets are with irons. it now shoots bit better(or at least more consistent) now that i have peeps on it.