Brenneke slugs - light at the end of the tunnel...

[longbow]

Excellent! Beautiful job on the slug and wad and excellent results. You are the man Cap'n Morgan!

So the full bore Brenneke is a clear winner at this point?

Are you planning to do any more work with the slug in wad design (like in post #71)?

I gotta say that is truly a beautiful job you did with that slug and excellent results.

Good going!

Longbow

[Cap'n Morgan]

Hogtamer.
The scope mount is just a simple aluminum thingie. It fits over the rib and has four socket set screws, two on each side, set in an 45 degree angle below horisontal which pushes against the bottom of the rib. It was never meant as a permanent setup, but just an aide for testing slugs.

Longbow.
I'll still do some further testing with the sleeve-slug, but I doubt it can ever match the performance of the Brenneke. But it's faster to produce in larger numbers and for short range work it's probably just as good or better than the Brenneke clone. I'll also try different loads for the Brenneke to see if a velocity increase will affect the precision. Right now the speed is just below 1100 fps and I would like to rise it to around 1200 fps.

[longbow]

Well Cap'n, now I have to go back to bore size Brenneke's to see if I can come close to your results.

You have not only proven it can be done but that one of the keys is the wad. Good consistent wads are a must. I'm talking attached wads here but the rest of the column matters too.

I have been trying to come up with a simple and inexpensive solution for the home tinkerer who does not have access to injection molding equipment... and one that does not require endless hours of machining plastic rod or the like. Still not there and thinking about going rifled gun.

I do like smoothbores though and I really wanted to have a poor man's "double rifle" using a 12 ga. side by with rifle sights and slugs like your Brennekes. Maybe one day. I have some more experimenting to do.

I am glad you have had such good success as it gives me renewed hope. Great work you have done and thanks for sharing.

Longbow

[Cap'n Morgan]

Did a small test today to see how the Brenneke slugs would shoot from my semiauto Beretta with 3-1/2" chamber and overbore.

I first tried three shots at 25 yards using the largest choke I could find. They made a nice 1-1/2" group - not bad, considering the gun has only a front bead for aiming. But since the idea was to see if the accuracy was affected when the slug was not a tight fit in the barrel, I removed the choke and shot three more rounds from what was now a true cylinder. The group was a spitting image of the first!
Back from the range I dropped a slug into the barrel and sure enough, it stuck in the forcing cone. A slight pressure would push it all the way through, leaving a few bright spots on the slug where it had been in contact with the barrel.

So I'm none the wiser, except I now know that my overbore barrel, which I thought was .732" is actually .729" Also, shooting a slug from a 2-1/2" hull in a 3-1/2" chamber seems to have no negative effect on the precision.

It was a sheer pleasure to shoot slugs from the Beretta Xtrema as it has a recoil-absorbing buttstock. Function was perfect, but I will have to make some sort of a snap-on mount to add a hollowsight as the gun shoots to high for instinctive shooting at a running target. Oh, well. The fun never ends...

[longbow]

Looks like you've got 'er beat Cap'n! Good going!

Now it is my turn... I hope.

Longbow

[Matt_V]

............

While most of the testing so far has been made with paper cases (I picked up a couple of hundred old, primed 2-1/2" cases a few years ago) I'm now using mostly plastic due to the availability. It seems most European brands are tapered (skivered) on the inside of the mouth, probably to help forming a better star crimp. Try as I may, I can't get a decent roll crimp on those shells unless I trim off the skivered part.

Yes, if you look in siarm website many are "shived" a.k.a. skivered for exactly what you state, in the italian original they suggest against using them for roll crimping.
http://www.siarm.com/index.php?cPath=2_25_38_39_137

They do have paper hulls as well (both skivered and not skivered).
http://www.siarm.com/index.php?cPath=2_25_37_46

[Cap'n Morgan]

Unable to leave well enough alone, I'm returning to the sleeve-slug project...!

Although they work fine within the fifty yard range, group size increases dramatically at longer ranges and the slugs starts to tumble. At one point it dawned on me that the problem seemed to get worse after I shifted to an extreme meplat slug instead of the more traditional ogival design I started with. Also, I have read of wadcutter boolits becoming unstable at longer ranges.

So here's the new plan:



From left to right. The original design. The flat nose "Hammerhead" design and finally a new slug I named "propeller head" due to its helical nose profile. (The name does NOT refer to the designer )

I will load a number of slugs with the different designs, and test them against each other at 30, 60 and 90 yards. If things work out as I hope, the helical design should show better precision at the longer ranges due to rotation imparted by the fins on the nose. If not, the test should at least show if a ogive design are better than a flat nose, but time will tell. First I have to make a mold for the propeller head. Stay tuned...


I

[longbow]

Good to see you are back at it. I am sure we will get lots of good reports and photos.

As for the tumbling bit, I think it was turbo1889 that posted info on the Lyman sabot slug being unstable through the transonic and subsonic velocity range when shot from smoothbore due (I believe) to the large wadcutter meplat.

Now having brought that up, I have to wonder about the Hammerhead slugs. So far reports are good but I think all the posts I have read are results from rifled guns and the Slug R Us site said the Hammerheads were not suitable in smoothbore. I wondered why as they are an attached wad style slug but maybe that's it ~ they become unstable at some velocity.

Has anyone tested that out?

Anyway, I like your original design and I really doubt the propeller head version will develop a spin and even if it does it would be so slow as to not make any difference in my opinion.

Just looking at it ~ if velocity is 1400 FPS a typical rifled shotgun is rifled with a 1:38" twist so that is a turn every 1.06' so that is 1321 rev's/second or 79,260 rev's/minute. Even a round ball twist for 12 ga. at 1:110" which works out to 42640 RPM. I don't think vanes/fins of any size on a slug can impart anything like that sort of spin in the fraction of a second a slug takes to get to 100 yards.

Just my opinion of course. A super slow mo video of helical finned slugs would be nice to get to see if they do develop any significant spin but of course you would have to shoot through the field of view at about 100 yards to to check spin.

While I wouldn't bother with the vanes or fins I do admire your ingenuity and skill... and persistence! You have done fantastic work so far and your mould (and slugs) are things of beauty! And best of all they work well.

I do think the ogive design is better than the large flat point design but again, just my opinion. It will be very interesting to see your test results.

So, whatever you decide to do I will be looking forward to your reports which are always terrific and I am sure you will be successful and we will all learn some more. I am sure everyone here appreciates the time and effort you put into these designs, tests and reports. I know I do.

Longbow

[Cap'n Morgan]

Longbow, thanks for the nice words. I know I should just be contend and stick to my Brenneke clones, but once an idea takes hold, I just can't leave it alone...

You're right about the slow spin not being enough to stabilize the slug, but it is only meant to balance out any attempts by the slug to steer off course due to any imperfections in the shape and profile. A perfectly straight arrow will fly true with straight fletching, but if the shaft is slightly bend it will take a curved path. A helical fletching will correct this problem considerably by rotating the arrow in flight - even if the rotation does nothing for the inherent stability of the arrow.

It is, to some extend, the same with a round ball from a muzzle loader; The rotation can be as slow as 1:70" and probably even slower. The rotation doesn't have to stabilize the round ball as such - only to keep it from taking on the "wrong" rotation once the critical fifty yards point is reached and the Magnus effect sets in.

Now, if an almost perfect sphere, like a round lead ball from a smoothbore can achieve enough rotation after fifty yards to miss a 3x3' sized target at a hundred yards, the pressure on the front of the ball must be considerable. I'm pretty sure even my tiny fins will add some correctional stability to the slugs - at least enough to keep them from tumbling. I found a few 3x3' cardboards for targets. Hopefully they're big enough

[longbow]

Yup! Round balls can veer wildly off course if they start out with any spin at all and even when "perfectly" launched they still pick up a spin from imperfections, sprue drag or whatever but that takes somewhere between about 70 and 100 yards to have a significant effect.

Your arrow analogy is certainly correct and I always use an offset straight fletch to impart spin because I shoot wood arrows and even the best straightened wood arrow will still tend to warp somewhat. So looking at the slugs that way I have to admit that if they pick up any spin it may help a bit.

Something else that I wonder about and again my reference is to turbo 1889 who posted something about slug length versus diameter and IIRC the slug should be about 1 1/2 times as long as it is in diameter. Too long can cause issues. I am not quite sure why as I would figure the longer the better but you just can't make a slug as long as an arrow so maybe it is a turbulence/drag/shock wave issue where a shorter stubbier slug is less affected. This also fits in with the Lee 7/8 oz. slug being more accurate for many than the 1 oz. slug though weight distribution may come into that as well. Could be the 7/8 oz. slug is just better balanced.

As you mentioned, something your fins may do is create consistent turbulence which may reduce uneven drag along the surface of the slug. Kind of like air "lubrication". If so that may eliminate or at least reduce and buffeting induced wobble.

And that made me think of the longer slug again. I wonder if a longer slug is more prone to turbulence/buffeting induced wobble as it goes transonic due to longer time for the shock wave to move along the body of the slug.

It will sure be interesting to see your results though as if one design performs consistently better than the other we will have learned something.

Have at 'er Cap'n and good luck!

Longbow

[victorfox]

Suppose, as supposition only, Cap'n'Morgan made .410 wads and slugs too....

[Cap'n Morgan]

Suppose, as supposition only, Cap'n'Morgan made .410 wads and slugs too....

Not likely, as I gave away the only .410 I have ever owned, a couple of years ago (Boito single shot)

[victorfox]

Cap'n The least i can say is that your stuff is top notch. Period. Thanks for sharing.

[Cap'n Morgan]

I got sidetracked by a slingshot project during my latest slug project, but now things are coming together.

The plan is to do a comparison of different nose profiles on three otherwise similar sleeved slugs. The comparison is not quite identical as the weight varies:
Round nose slug =450 grains
Flat nose = 520
The latest design, the "Propeller-head"= 565 grains
All weights including wad.

In spite of the weight difference, the test should still provide a clue to the influence on accuracy (if any) the front of the slug has.

The test will follow later when I can find the time. This is what the Propeller-head - or spin-slug - looks like:

[Hogtamer]

More amazing work! I do believe there's more competent creativity and experience on this forum just now than I would have ever imagined! Like Popular Science magazine with Cliff notes for us pedestrians. Thanks all!

[Ballistics in Scotland]

Longbow, thanks for the nice words. I know I should just be contend and stick to my Brenneke clones, but once an idea takes hold, I just can't leave it alone...

You're right about the slow spin not being enough to stabilize the slug, but it is only meant to balance out any attempts by the slug to steer off course due to any imperfections in the shape and profile. A perfectly straight arrow will fly true with straight fletching, but if the shaft is slightly bend it will take a curved path. A helical fletching will correct this problem considerably by rotating the arrow in flight - even if the rotation does nothing for the inherent stability of the arrow.

It is, to some extend, the same with a round ball from a muzzle loader; The rotation can be as slow as 1:70" and probably even slower. The rotation doesn't have to stabilize the round ball as such - only to keep it from taking on the "wrong" rotation once the critical fifty yards point is reached and the Magnus effect sets in.

Now, if an almost perfect sphere, like a round lead ball from a smoothbore can achieve enough rotation after fifty yards to miss a 3x3' sized target at a hundred yards, the pressure on the front of the ball must be considerable. I'm pretty sure even my tiny fins will add some correctional stability to the slugs - at least enough to keep them from tumbling. I found a few 3x3' cardboards for targets. Hopefully they're big enough

Although you got such good results with the Brenneke type, completely sabot-encased slugs do have a couple of advantages. One is that they eliminate the possibility of leading, which is more likely and more of a nuisance than plasticking. More importantly if you have any idea of a manufacturer immortalizing the ''Cap'n Morgan'' slug like they did Monsieur Minié or Elmer Keith's bullets (and you can dream can't you?), plastic is better at adapting to bores of different diameters.

You are right about the way skewed fletchings don't actually stabilize it, but minimize the effect of its curved path by converting that path into a helical curve. One of the main reasons why rifling twist was so badly understood in the early days was that they thought rifling worked on a bullet in the same way. Then once they had wised up to gyrostabilization, they went back and assumed that was what happened to the arrow. Well it can't be. Forgetting for a moment the projectile density, Greenwood's Formula is good enough for this. Ideally projectile length in calibres, multiplied by rifling twist in calibres should be 150 or more, though in practice 200 will often work. An arrow will often be about 100 calibres in length, so it would require a spin of 1½ or 2 calibres, the latter being about 5/8in. or 16mm., or about a quarter million rpm. You couldn't apply that to an arrow by fletchings at one end, and it would fly to pieces if you could.

I agree, the spin of the propeller-head slug couldn't gyrostabilize a smoothbore slug. Greener illustrates an early slug in which air entered through four helically disposed holes in the front. As the holes were tapered, the air rushed out of the rear faster than it entered the front, exerting a jet effect. But to work, it had to impose enough air resistance to drastically impair impact velocity.

That isn't to say the propeller-head design is useless, though. General Hatcher claimed that a musket ball would eventually slip out from behind the cushion of air in front of it, creating the sudden deterioration of accuracy we have observed between fifty yards and a hundred. A rifle bullet, besides being gyrostabilized, spins off that air like the propeller inside an old-fashioned washing-machine, and your slug may do the same.

Round balls require very little spin indeed, but I think they work in much the same way as an ordinary bullet. A .5in. bullet with a 70in. twist scores 140 by the Greenwood formula, and I forget in what caliber a 10ft. twist was found to work. Probably one that exceeded that 200 figure, but any round ball is a fairly short range missile, and bullets (as witness sand scratches making more sloping striations than the rifling did) retail rotational velocity more than they do the linear kind.

[cpileri]

those look super cool. looking forward to how they perform
C-

[elvas]

Cap'n Morgan,
Beware of loading the slug as seen in the second photo, in a tubular magazine with more than one shotshells. A hunter here lost two fingers with a factory loaded Gualandi slug with the nose slightly protruding from the crimp.

[longbow]

Cap'n Morgan those are nothing short of spectacular slugs! Certainly spectacular looking and beautiful work once again.

I am hoping they shoot as good as they look.

One question, though I am pretty sure these are the same sabot design as before:

Have you found any issues with the sleeve portion of the sabot failing ~ becoming loose or leading edge opening up or whatever? Just curious as it looks quite thin.

I must say that you are an inspiration! I have to get back to my own experiments though you are in a league well beyond my abilities. I was off work for a while (bad economy in Canada) so no money. I am back to work now for at least a few months but no time! Funny how that works. I may get more done after the mill shutdown in April.

Okay then another question: Is your mould nose pour or base pour? The flat on the nose appears to be slightly recessed (ejector pin?). Curious once again.

Again, excellent work and thanks for keeping us all informed. Looking forward to range tests of those propeller heads!

Longbow

[Cap'n Morgan]

Longbow.

Too bad with your work situation! At least you're back at it again. I'm flooded with work most of the time and probably shouldn't complain, but sometime it's almost too much...

Yes, it's the same sabots as before, only now they're made from tougher plastic material, HDPE. The glass-clear ones in the picture are made from an even tougher material which name escapes me at the (senior) moment. The first wads I tested was made from ABS and later LDPE, but would either crack (ABS) or show clear signs of collapse/gas blow-by (LDPE). Since the wads and slugs are supposed to stay together to the bitter end, any permanent deformation is detrimental to accuracy.

...and yes, it's a base-pour mold with an ejector pin. The nose design will not work in a normal two-part mold.


Elvas.

I'm aware of the problem with tubular magazines and pointed bullets. In fact, I've been contemplating a slug design with a hard-rubber point - like Hornady uses in their lever action bullets. This would allow for a much improved ballistic coefficient (which is an inherent problem with slugs due to length/weight restrictions) and at the same time eliminate the risk of a magazine explosion.