Hollow core lead vs. tin slugs ?

[skorec]

WOW Mathias,

I want to taste all (4)  types of lightest for sure – I will try contact seller.
Next year offer is also very interesting for me. May be I will contact you at springtime.
I also have contacted H&N whit ask to produce lighter ( 5-8gr ) .177 slugs with large and deep hollow point made from lead or from tin.
A lot of people own/prioritizing  low power AGs or want to save environment.

Peter

Mike,
Your experiences are very important fore sure. Unfortunately sometimes I do not understand your explanation probably because I am  very bad at English . 
 
In my knowledge and in my words  the lines creating  at slugs by rifling lands have to be shallow and narrow us much as it is enough for spinning  and grooves diameter have to be  the same or a littleeeee bit smaller as slug or bands  OD. The band at base on .177   Rabit Magnum is about 4,6-4,7 mm and yes they are  also very inaccurate from all of my PCPs.

[Ribbonstone]

LAte to the party....so I have to ask..other than a legal restriction on lead:

What advanatge does tin it offer (besides not-lead)?

Know us shotgunners got use to steel shot where required (plus points for the makers in getting those loads up to a passing grade from a pretty horrid start)....know I've surviced lead free indoor firearms ranges...but likely I will have to soon have to (eventually in my location) have to survice lead free airgun ammo too?

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Know that over the long years,lots of trys at non-lead projectiles have been tried.  Still have some "Gallery" .22 shorts that are stintered iron in a plastic/glue compressed matrix(which is the same as the BB Dustdevils..and not something I'd recommend  for barrel life/accuracy in a rifled bore...but when where carnivals concerned with not giving out enough stuffed anuimals?)=)...have tried the .22LR CCI's that are the same thing with a copper powder...sabat ammo (with whatever metal you want as the sabot is the only thing that touches the bore)....pure copper bullets (in center fire)....steel shot...bismuth shot..cast Kerksite (basically a Zinc alloy)...etc.;

Whatever comes....I'll adapt...but util it is REQUIRED...am sticking to lead...pellets/slugs/or ball.

[rsterne]

Ribbon, the ONLY reason, from a performance point of view, to use tin.... is that because it is only 65% the density of lead, for the same WEIGHT projectile a tin one will have a longer, sleeker shape, and hence a better BC.... This doesn't work for shot, or for replacing the same SHAPE projectile in lead with tin, copper, steel or aluminum, because the BC would decrease in proportion to the (reduced) weight....

The Ballistics Coefficient is comprised of two factors, Sectional Density (weight divided by caliber squared), and the Form Factor (dependent on the Drag Coefficient), related by the formula BC = SD / FF.... Two projectiles of the same caliber and weight will have the same SD, regardless of the material.... However, the lighter material, for the same weight, will have to be formed into a longer projectile, and therefore can have less drag (and a lower FF)…. If the SD is the same and the FF is less, then the BC will be better.... On the other hand, if you have two projectiles of the same shape, they will have the same drag, and hence the same FF.... The lighter one will have a lower SD, and therefore a lower BC....

I'll give you an example.... Lets start with this slug, made from lead.... It weighs 65 gr. and has an SD of 0.140.... The FF is 0.955....



Now let's see what a 65 gr. slug made from tin would look like, with the exact same SD of 0.140.... The FF is 0.676....



That slug would weigh 100 gr. if made from lead, and you couldn't shoot it at anything like the same velocity that you could get with a 65 gr. slug from a given PCP.... However, if you cast it out of tin, it would only weigh 65 gr. and you could drive it at the same velocity as the short, stubby slug above it.... There is NO question which slug has less drag.... The long, sleek tin slug, with about 30% less drag, would win hands down....

Bob

[Ribbonstone]

Just flying partly blind here.

Saying that the density part of the twist rate equation s worth less than the length...or the other way around?

[Doug Wall]

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

I totally agree!!! This particular springer just happens to be a comparison test platform that we use. Wouldn't even consider using it in real life!

[rsterne]

Yes, a faster twist rate will be required for the long tin slug.... However, the FPE loss is very small to produce the extra RPM required to stabilize it....

http://bulletin.accurateshooter.com/2015/02/does-barrel-twist-rate-affect-muzzle-velocity-litz-test/

In actual measurements by Bryan Litz, the velocity change was smaller than the SD....

Bob

[Ribbonstone]

OK...good to check what I assumed about twist/length vsjust weight.
Didn't even consider the energy going into faster rotation....but as you mention, it's not enough to matter (or even notice).

[skorec]

Checking is always necessary.
......................

Made from Tin + hollowed may be longer  and may be probably producing by machine  automat.

Barrel rifling can be shallower because the tin is harder then lead.  For low power shooting we can also  stay at caliber .177. 

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=0.5&nose=.3&meplat=.06&drive_band=.177&base_diameter=.177&angle=0&boat_tail=0&secant_radius=&weight=9.8&density=3

Whit the same TR=6 we can also shoot four time heavier the same profile slugs made  from lead without hollow but rifling  have to be rather whit narrower  lands as shallower groove.
 
It seams that Slugs/bullets  let us more variation then pellets just we need custom barrel whit faster twist rate. 

[Doug Wall]

I don't want to hijack this thread, but when are we going to start to see some injection molded polymer/copper pellets/slugs, like the ARX bullets? Might be interesting.

[Ribbonstone]

When I first read the title of this,though someone was going to try Abe Flatau's "ring airfoil"tubular projectile once again. Not really his (most of thework he did was on the 37mm grenade launchers)...when I did reservh it, found designes as early as the 1890's for a "tubular"bullet (the hole in the middle was suppose to do wonders for the BC)...but the "pusher"wad needed to seal it and then drop away was always a problem.

Don't know when they first stated making stintered/poly bullets....1930's?1940'? for some .22 ammo.  Stintered lead then stintered iron; most mostly used for carnival type shootinggally use, where accuracy or even mostly worn out rifing wasn't a concern (after all,they didn't want to give out any more stuffed animals that they had to).

Did notice CCI had stintered copper ammo announced recently(haven't tried it)....and the "Dust Devils"are the BB incarnation of the old stintered iron idea.

All things considered, not really sure it would make for great airgun ammo....but then again, it's likely not really any harder that tin and there are tin-pellets.

Sabot ammo has been tried in airguns once(SABO), and there are several plastic/metal pellets (although as the plastic doesn't drop away,it's really not a sabot...just a thick plastic jacket).


Does seem that airguns haven't had alot of innovation tried (yet).

[skorec]

We know that lead create good inertia of spin and mass have to be rather at rear of slugs/bullets.

 What about to do 3R  Jacked from lead on reversed spire from aluminum for low power long range  shooting ? 

[Mod90]

Lead jacketed aluminum slugs? Not a bad idea. Would be lighter, and could be made longer or shorter as necessary. The lead jacket will give the rifling something to grab onto.

Even better, a hollow lead slug filled with tin. Might make a wicked hunting round.

[skorec]

Yes but “Variations in the size of the large flat areas (meplat) at the front of many of them coupled with the detail shape at the edges of the meplat. Very small amounts of rounding on the edges can have a large effect on the drag coefficient as well as the aerodynamic stability.

“
see https://www.gatewaytoairguns.org/GTA/index.php?topic=166147.40

Aluminium point can ovoid this problem
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=.142&length=.35&nose=.2&meplat=.02&drive_band=.142&base_diameter=.142&angle=0&boat_tail=0&secant_radius=&weight=4.3&density=5