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Tip on discarding sabot for APFSDS round?

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Tip on discarding sabot for APFSDS round?

Unread postAuthor: SpudFarm » Thu Apr 08, 2010 12:58 pm

Hello, I took up my hybrid project again recently and I like APFSDS rounds and I do have a car to fire onto :) The cannon needs to be made a bit more portable before I can transport it to the range and load it as hard as I want to.

I have always had problems coming up with sabots so I always end up just putting a rag behind the penetrator.
Today I made an effort by cutting a 15cm piece of my barrel and tried to make a sabot by:
Cutting out a 1/2" piece of wood and placed it in the bottom of the pipe section, then dropping my penetrator inside and filled the whole thing with expanding foam. This turned out rather bad since there where large air pockets and it never cured properly and I ended up spending an hour washing it in gasoline.

What I plan on attempting later is cutting out a few disks of dense styrofoam used in construction (the blue stuff). when I have disks to cover the full length of my projectile I will epoxy them together and carve out the core to fit my fin stabilized projectile. Then just cut it into four parts lengthwise and backing it with a wooden disk in the barrel.

Do you think this is a proper way to do it or do you think it will disintegrate and jam my barrel? It is for my hybrid (UPGBH10x) so it is going to be 4.8cm (just under 2") in diameter and about six inches long.
Any tips and constructive critics is welcome.
I know I have a habit of over-explaining but I hope it isn't to bad :)

Thanks!
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Unread postAuthor: thedeathofall » Thu Apr 08, 2010 2:50 pm

Hmm.. could you link to your round. It has been a while since ive seen this thing...

Perhaps this may be of service. This was designed for use with 2 inch vortexes, but being foam, it could work.
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Unread postAuthor: SpudFarm » Thu Apr 08, 2010 4:35 pm

thedeathofall wrote:Hmm.. could you link to your round. It has been a while since ive seen this thing...

Perhaps this may be of service. This was designed for use with 2 inch vortexes, but being foam, it could work.


Yeah, that might work. I will try that if I can't get a good one out of the construction styrofoam.

The cannon is in the hybrid showcase (UPGBH10x)
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Unread postAuthor: thedeathofall » Thu Apr 08, 2010 5:19 pm

The cannon is in the hybrid showcase (UPGBH10x)


Actually I was refering to your ammunition. What are you using as "penetrator" rounds?
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Unread postAuthor: SpudFarm » Fri Apr 09, 2010 5:31 am

Im sorry about that.
Here are some pictures of what I have to work with right now. I know it isn't perfect but I did not make it for looks ^^

Image
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Unread postAuthor: Crna Legija » Fri Apr 09, 2010 6:41 am

that round looks mad :evil: its gonna f@#k that car up
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Unread postAuthor: twizi » Fri Apr 09, 2010 6:47 am

is that silver tube your barrel or a pipe with same id of your barrel
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Unread postAuthor: SpudFarm » Fri Apr 09, 2010 8:27 am

-_- wrote:that round looks mad :evil: its gonna f@#k that car up


I hope so. I also hope that i can get the cannon to the car.

The pipe is a section I cut off my barrel.
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Unread postAuthor: SpudBlaster15 » Fri Apr 09, 2010 11:32 am

That round looks beastly.

What steel alloy did you use to construct it, and have you applied any heat treatment?

As for the sabot, your original idea should work well.

What I plan on attempting later is cutting out a few disks of dense styrofoam used in construction (the blue stuff). when I have disks to cover the full length of my projectile I will epoxy them together and carve out the core to fit my fin stabilized projectile. Then just cut it into four parts lengthwise and backing it with a wooden disk in the barrel.
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Unread postAuthor: Crna Legija » Fri Apr 09, 2010 11:46 am

i used to shoot darts(the type use in the game darts) out of my bv gun and would only use some cloth as wadding cant you just put a wood disc behind why do you need it supported in the middle when it fits so nicely

you should try harden the metal if you haven't and maybe bend the fins like a propeller of a plane to give the round spin in flight
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Unread postAuthor: SpudFarm » Fri Apr 09, 2010 1:24 pm

SpudBlaster15 wrote:That round looks beastly.

What steel alloy did you use to construct it, and have you applied any heat treatment?

As for the sabot, your original idea should work well.

What I plan on attempting later is cutting out a few disks of dense styrofoam used in construction (the blue stuff). when I have disks to cover the full length of my projectile I will epoxy them together and carve out the core to fit my fin stabilized projectile. Then just cut it into four parts lengthwise and backing it with a wooden disk in the barrel.


Thanks!

The alloy is unknown since I just made it on work about a year ago while I was waiting for the bus. I do think it is hardened though.
I did harden it by using the blow torch to heat it and sticking it into used motor oil.

I will try the styrofoam method. I really want a high speed shot of a sabot discarding.

-_-: No rags because it messes up the angle of exit and will stick to the penetrator in flight. And I have to use a sabot because my barrel is horribly expensive and I want to use it after this shot.
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Unread postAuthor: thedeathofall » Fri Apr 09, 2010 4:02 pm

well... I am almost at a loss of words after seeing how crazy big that is...

The pool noodle idea should still hold true though. Just cut it into 4 parts, and maybe take off a little extra material off where the fletches are. Should work just fine. Plus you can find them at target, dollar stores, grocery stores, and of course, online and they are extrememly cheap. A 5 foot noodle could probably make 8-10 of these, so 10-12.5 cents apiece isn't a bad deal. (USD)

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Almost forgot, how heavy are those things? I want to run a quick calculation.
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Unread postAuthor: SpudFarm » Fri Apr 09, 2010 4:57 pm

thedeathofall wrote:well... I am almost at a loss of words after seeing how crazy big that is...

The pool noodle idea should still hold true though. Just cut it into 4 parts, and maybe take off a little extra material off where the fletches are. Should work just fine. Plus you can find them at target, dollar stores, grocery stores, and of course, online and they are extrememly cheap. A 5 foot noodle could probably make 8-10 of these, so 10-12.5 cents apiece isn't a bad deal. (USD)

___

Almost forgot, how heavy are those things? I want to run a quick calculation.

It does have some size to it. Only the results of this one will show me if I should make them smaller or bigger.

The pool noodle is a completely plausible idea, I will try that is the sabot I am going to make fails/to time consuming.

This particular penetrator is about 200g and should be traveling about 240m/s at a 5x mix. At a 10x though it will break the sound barrier.
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Unread postAuthor: IMagius » Thu Apr 15, 2010 1:22 pm

First - impressive ammo!!!

I know you had a bad experience with expanding foam, and so did I once. Then I had an idea that worked out much better then I expected ... you may want to give it some thought.

I used 4 sections of "Poster Wrappers" (about 1.5" diameter "bags" that movie posters etc.. are usually shipped/sold in - ask you local Video Rental store to save you a few...) and carefully taped a small corner of each in place so that each bag fit between each stabalizer fin, then filled each bag with Low Expansion expanding foam. (the Low-E stuff gave me best results - it seems to cure quicker and harder than the regular stuff).

This effectively creates a 4 piece Sabot that is "mess free" and easily removed from the "form". A bit of creative carving after curing at the leading end to create a V cone helped in it's mid air deployment as well.

You're idea of using the plywood "backer" should go a long ways to prevent damage to the Sabot while it's in the barrel as well - all the pressures should e pushing against it - and it, in theory, will be restign against the base of the projectile.

I haven't done a lot of Sabot work, but from what little I did, that was the easiest (and cleanest) method I could think of for the size I needed (2"). I was also working at a fairly short range (<50 feet) so I don't know if this style of discarding Sabot was effecting my accuracy or not.

Good luck!
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Unread postAuthor: iknowmy3tables » Thu Apr 15, 2010 3:47 pm

so from what I understand you intend to make a rod of Styrofoam from cutting multiple disks, stacking them, and then carving a the discarding sabot out of that. You should be able to buy really thick Styrofoam that is often used for crafts

I don't think it would jam even with the heat, you are dealing with a hybrid, you should test how your foam decomposes under heat some foams make more of a mess, while others might primarily just shrink. maybe wraping the sabot in some paper or foil might help.

If I understand IMagius' idea correctly it seams pretty good, casing the foam sealant around the dart

my main concern is with your dart design though although it looks bad ass it's not an efficient dart, the metal fins on the shaft of the dart, to make an effective dart you want more mass at the tip and higher drag at the rear, which is really tricky when your making something with a narrower and sharper tip and spread out base/rear stabilizers. It's actually very tricky to make a saboted dart that penetrates better than it's slug equivalent. You can find various examples in experimental military projects where engineers encounter the difficulty of effectively employing advantages of flechettes in firearms.

I would recommend trying other different designs, including slugs if you can, because with your center of mass so far back from the point of impact, your current dart will be very likely to yaw sideways or deflect when it hits the target.
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