Hollow core lead vs. tin slugs ?

[skorec]

Description of FX slugs:
"
The FX hybrid slugs benefit from the external dimensions of a high ballistic coefficient slug design, but have a completely hollow core and recessed base. Therefore making it light and easily shot accurately by most PCPs. With these FX hybrid slugs you can achieve velocities and trajectories much greater than any other slug or pellet. The FX hybrid slug will provide a flatter trajectory, less wind drift, retained energy at longer distances, and more accuracy at those distances than any pellet. The hollow core provides massive expansion, incredible for hunting.
„

If the BC is so good  why not produce the slugs from tin ?

Unfortunately If I change bullet density at Colbe from 11,4 to 7,6 the
BC has decrease two times ( from 0,04 to 0,02 at my dreamt-of caliber .14 )

http://www.geoffrey-kolbe.com/cgi-bin/drag_working.cgi?unit_length=inches&weight_unit=grains&bullet_name=Custom+bullet&re_calculate=yes&boundary_layer=L%2FT&diameter=.14&length=.23&nose=.1&meplat=.04&drive_band=.14&base_diameter=.14&angle=0&boat_tail=0&secant_radius=&weight=5.3&density=11%2C4
http://www.geoffrey-kolbe.com/cgi-bin/drag_working.cgi?unit_length=inches&weight_unit=grains&bullet_name=Custom+bullet&re_calculate=yes&boundary_layer=L%2FT&diameter=.14&length=.23&nose=.1&meplat=.04&drive_band=.14&base_diameter=.14&angle=0&boat_tail=0&secant_radius=&weight=5.2&density=7%2C6

[Mod90]

Well it found one answer to your question. Here's a few others.
Lead is cheaper, but more importantly much more malleable than tin, thus lending itself much more easily to being able to alter its shape slightly when being propelled down the bore. With the low pressures used by our air guns,  this is necessary at the breech to form a gas seal,  and at the muzzle to be able to be squeezed down when passing through the choke.
Lead is a lubricating metal,  tin is not.
Another is that tin is much harder than lead. I strongly suspect that shooting pure tin ammo on a regular basis would rapidly wear out our barrels.

[skorec]

Thanks, I am just trying to find out slugs for 11 FPE  AGs  and  YES you have true for sure but :

1.   Tin pellets are using - probably only at  conservation areas


2.   Why hollow core lead FX hybrid slugs  have so good  BC=SD/FF=0,08 ?

[Doug Wall]

I hate to burst your bubble some, but the FX slugs weigh 22 grains. They are also a tight fit in the gun that I'm testing (a springer) them on. The gun normally shoots about 15-16FPE. I'm only seeing about 480 fps, which translates to about 12 FPE. I'll be testing expansion today, but I would suspect that you may need as much as 700-800 fps on target to get proper expansion.
As Mod90 correctly stated, tin is harder than lead. I doubt that I would even be able to chamber a tin equivalent of the FX slug.

[Back_Roads]

 I did cast some .22 NOE slugs in tin, I used the flat nose pin, figured hardly paid to test a HP. They drop at 30 gr. in pure lead, and just under 20 gr. in pure tin. FPS was equal to similar weight lead pellets, from a Benjamin Genesis NP rifle, shots were under a nickel at 20 yards. I'm not sure how well a .177 or smaller slug would do.
 

[rsterne]

Pure tin is about BHN 10, certainly not too hard for airgun use.... but would be a bit harder to swage than lead.... There are two components to BC, the Sectional Density and the Form Factor.... If you have two slugs with identical weight and outside shape, they will have the same BC.... Making one from tin and the other from lead with internal hollows will make NO difference to the BC....

Peter is correct, if you reduce the density, and hence the SD, for the same shape you will lose BC.... Tin is 65% the weight of lead.... There have been several guys who have tried casting in pure tin with good success.... The caveat is that the less dense slugs will require a faster twist rate to stabilize, so if your barrel is marginal for a given bullet with lead, you may need a faster twist rate for that same bullet in tin.... Hybrid (hollow lead) slugs will not see as much effect from their reduced weight, because the lead is concentrated around the outside of the slug, increasing its "moment of inertia" in spin, to be more like a solid lead slug....

One thing about the new hollow "Hybrid" slugs.... If you compare the same weight in solid lead or with internal cavities, the Hybrid will end up longer and sleeker for the same weight, which should result in a bit better FF.... Since BC = SD / FF, then the Hybrid should also have a bit better BC than the same weight solid slug of the same caliber and nose shape.... The same, of course will apply to tin slugs.... For the same weight, they will have a better BC than the same nose shape and caliber in lead, because they would be longer, with a better FF....

Bob

[skorec]

Bob
Thanks for eeeexcellent explanation. I was thinking also about better moment of inertia in spin but I was not sure because at pellets it is contrariwise for better long range  accuracy.

The question only is which way will be easier/less expensive ( barrels + slugs )   for very accurate  .142/11FPE/800-950FPS   shooting at 100 yd.

1.   5,4- 7,5 gr - longer tin slugs 
2.   5,4- 7,5 gr - longer hollow core  lead slugs  - FX design
3.   5,4- 7,5 gr -  shorter not hollow core lead   slugs - Corbin design
4.   5,4- 7,5 gr - longer hollow core  lead slugs  - not FX/Corbin  design – hollowed from tail side

Just now I am thinking about theoretical/future mass production not private project.

[rsterne]

IMO, for "very accurate", with the difficulty of casting such a small pill, you need to swage.... I think tin MAY be a bit too hard to swage, and #1 is certainly more expensive.... Generally, slugs (aka bullets) want to have the CG aft, so the #4 hollow base design MAY not be the best choice.... That leaves choices #2 or #3.... I think the FX style slugs can be made with Corbin dies (and I am pretty sure the prototypes were)…. but they require multiple strokes of the press to make the large HP cavity, shape the nose, and make the HB.... and also more expensive die sets.... The least expensive would be #3.... but IF you found the magic combination then #2 might provide a slightly higher BC....

Bob

[E30_S50]

Thinking outside the box...if the purpose is hunting, could you just use smoothbore barrel and shoot 3 tin roundballs per shot? Then you'd get a little bit of spread and won't have to worry about twist rate.

[rsterne]

Very limited range, accuracy, and impact, however....

Bob

[skorec]

IMO, for "very accurate", with the difficulty of casting such a small pill, you need to swage.... I think tin MAY be a bit too hard to swage, and #1 is certainly more expensive.... Generally, slugs (aka bullets) want to have the CG aft, so the #4 hollow base design MAY not be the best choice.... That leaves choices #2 or #3.... I think the FX style slugs can be made with Corbin dies (and I am pretty sure the prototypes were)…. but they require multiple strokes of the press to make the large HP cavity, shape the nose, and make the HB.... and also more expensive die sets.... The least expensive would be #3.... but IF you found the magic combination then #2 might provide a slightly higher BC....

Bob

I  add interesting link about JSB Lead free pellets .177/6.8gr



Machining instead swaging lead free/tin? pellets/slugs would   be probably too expensive. 

[skorec]

Drilling  3mm*4,5mm  hole in to the .177 H&N Rabit magnum decrease the weight  from 15,7gr to 5,4gr and pellet/slug will be also a little bit shorter too. BC should be still two times better then tin BC for tin pellets.

Or should be better to wait when H&N start  swage the holes ?

https://www.merkuria.net/diabolky-kal-4-5-mm/1223-diabolky-h-n-rabbit-magnum-pre-extra-silne-vzduchovky.html

http://www.geoffrey-kolbe.com/cgi-bin/drag_working.cgi?unit_length=inches&weight_unit=grains&bullet_name=Custom+bullet&re_calculate=yes&boundary_layer=L%2FT&diameter=.177&length=.24&nose=.06&meplat=.12&drive_band=.177&base_diameter=0.177&angle=0&boat_tail=0&secant_radius=30&weight=16.5&density=11.4

[skorec]

Hollowed .177 H&N Rabit magnum BC=0,02

http://www.geoffrey-kolbe.com/cgi-bin/drag_working.cgi?unit_length=inches&weight_unit=grains&bullet_name=Custom+bullet&re_calculate=yes&boundary_layer=L%2FT&diameter=.177&length=.23&nose=.12&meplat=.12&drive_band=.177&base_diameter=.177&angle=0&boat_tail=0&secant_radius=&weight=6.4&density=4

[subscriber]

Why hollow core lead FX hybrid slugs  have so good  BC=SD/FF=0,08 ?

Because they are as long as much heavier slugs.  A projectile needs length to reduce the shock to air flowing into, around and over it.  The slugs are long for their weight because of the large hollow space inside.

EDIT:  Oops.  I am late to the party.  Question has been answered already.

[rsterne]

Drilling out a pellet to lighten it will DECREASE the BC in proportion to the reduction in weight.... If it is half as heavy, it will lose half the BC.... assuming you don't change the outside shape....

Bob

[JungleShooter]

Peter,
you're looking for .177 slugs for guns with low power. This means, light slugs.

The lightest in .177 I have found are the GRIFFIN SLUGS.
Ebay seller name = cheesehead1990


With a hollow base:  From as light as 10gr(!).  14c a shot
https://www.ebay.com/itm/GRIFFIN-Lead-Air-Gun-Slugs-Pellets-177-Cal-Hollow-Base-10-19-gr-100-Ct/183961827831?hash=item2ad4fab9f7:m:m-eVy0M7fhGej4HclptTjww


With a dish base:  From as light as 13gr.  14c a shot
https://www.ebay.com/itm/GRIFFIN-Lead-Air-Gun-Slugs-Pellets-177-Cal-Dish-Base-13-20-gr-100-Ct/174035336280?hash=item2885507c58:m:m-eVy0M7fhGej4HclptTjww


With a flat base:  From as light as 13gr.  14c a shot
https://www.ebay.com/itm/GRIFFIN-Lead-Air-Gun-Slugs-Pellets-177-Cal-Flat-Base-13-22-gr-100-Ct/183961814228?hash=item2ad4fa84d4:m:m-eVy0M7fhGej4HclptTjww


With a boat tail:  From as light as 16gr.  15c a shot.
https://www.ebay.com/itm/GRIFFIN-Lead-Air-Gun-Slugs-Pellets-177-Cal-Boat-Tail-16-24-gr-100-Ct/183961838401?hash=item2ad4fae341:m:m-eVy0M7fhGej4HclptTjww



The seller's explanation of the different bases of the slugs:
Hollow base is for moderate power guns.
Cup base is for moderate to high power guns, it is a little more forgiving.
Dish base is for high power, mostly pcp guns. (FX Crown loves them)
Boat tail and flat base are for the highest power guns.


Shipping to Slovakia
I only see shipping to the US on Ebay. But if you contact the seller you might be able to work something out.
If not, let me know, I can ask a friend to ship it from the US to you, or from Germany like we did the last time (but we'll need several months of time to make this happen, I won't be in Germany till the middle of next year.

Matthias

[Doug Wall]

Drilling  3mm*4,5mm  hole in to the .177 H&N Rabit magnum decrease the weight  from 15,7gr to 5,4gr and pellet/slug will be also a little bit shorter too. BC should be still two times better then tin BC for tin pellets.

Or should be better to wait when H&N start  swage the holes ?

https://www.merkuria.net/diabolky-kal-4-5-mm/1223-diabolky-h-n-rabbit-magnum-pre-extra-silne-vzduchovky.html

http://www.geoffrey-kolbe.com/cgi-bin/drag_working.cgi?unit_length=inches&weight_unit=grains&bullet_name=Custom+bullet&re_calculate=yes&boundary_layer=L%2FT&diameter=.177&length=.24&nose=.06&meplat=.12&drive_band=.177&base_diameter=0.177&angle=0&boat_tail=0&secant_radius=30&weight=16.5&density=11.4

The Rabbit Magnums are perhaps the worst projectile that I have ever shot out of airguns. Bad to the point of not being able to keep them in a 12" x 15" target box at 45 yards.

[KnifeMaker]

As always, many try to shoot slugs thru a barrel without slugging the bore, and selecting a projectile that properly fits it. If accuracy is that bad, the bullet is under sized for the bore.


always slug the bore, and select or size to bore or choke if present. No more  that .0003 to .0006-7 over groove dia.


Never depend on manufacturers published figures. They are almost alway incorrect. Often by a large margin. 


Knife

[Doug Wall]

I hate to burst your bubble some, but the FX slugs weigh 22 grains. They are also a tight fit in the gun that I'm testing (a springer) them on. The gun normally shoots about 15-16FPE. I'm only seeing about 480 fps, which translates to about 12 FPE. I'll be testing expansion today, but I would suspect that you may need as much as 700-800 fps on target to get proper expansion.
As Mod90 correctly stated, tin is harder than lead. I doubt that I would even be able to chamber a tin equivalent of the FX slug.

Update: I'm finishing up the testing on the FX slugs, and they don't expand at all at a velocity on target of 480 fps. They do expand at 860 fps(velocity on target) (36FPE). Don't expect them to expand well out of lower power PCPs.

[KnifeMaker]

Sorry Mr Wall, but that simply is NOT a slug gun. Not even close. The platform is the foundation needed before anything else.


Simply a non starter. 


Knife