3d Printed Shotgun Wads

[longbow]

In case you missed it, I have posted several times about my experience blowing up a shotgun, Not fun!

A short version of the story is that I loaded short rounds with a Lyman Foster slug with filled cavity. The slugs were cast from pure lead per Lyman instructions, the load was straight out of the Lyman reloading manual with the exception of short hull and filled slug. I only had one powder on hand and that was PB per recipe.

I had shot a few of these in my Browning BPS and recoil was particularly attention getting and extraction sticky but since it was a book load I just figured it was a "stout" load.

Next outing I took my single shot shotgun, bore was clear and easily observable being single shot, dropped a round in, took aim and pulled the trigger... there was a very loud explosion, blast of debris in my face and the gun went "limp"! When I recovered after a few seconds I found myself holding the action and buttstock in my right hand and forearm in my left hand. The barrel was laying on the ground about 10' in front of me with the entire top of the chamber missing!

Later examination showed lead streaks from where the case mouth was up to the forcing cone. My take is that the soft filled slug was obturating as it left (or maybe in) the hull then hit the forcing cone and just couldn't swage back down fast enough so pressure spiked. The BPS survived several shots seemingly unaffected but the single shot only took one round to destroy it.

I don't believe it was a fault in the gun because I should have paid attention to the punishing recoil and sticky extraction but at the time was not smart enough to see the over pressure signs.-- or at least respond appropriately to the over pressure signs.

I was very lucky and just got some minor cuts on my forehead and I lost about 40 decibels of hearing in my right ear... I was in the bush and like when hunting did not have shooting glasses or hearing protection. Stupid! And lucky! I am more careful now and I am very careful when working on slug loads substituting components. I make minimal subs and use low pressure data so there is a margin for error if pressures go up for some reason not evident to me.

Considering that a simple change of primer can affect pressure by up to 3000 PSI and crimp depth can have a similar effect, it is pretty easy to take a top end load over the top into dangerous territory with not much change in load/payload.

Okay not such a short story but worth repeating if it saves someone else's gun and/or body parts!

Play but play safe!

Longbow

[mikehill85]

In case you missed it, I have posted several times about my experience blowing up a shotgun, Not fun!

A short version of the story is that I loaded short rounds with a Lyman Foster slug with filled cavity. The slugs were cast from pure lead per Lyman instructions, the load was straight out of the Lyman reloading manual with the exception of short hull and filled slug. I only had one powder on hand and that was PB per recipe.

I had shot a few of these in my Browning BPS and recoil was particularly attention getting and extraction sticky but since it was a book load I just figured it was a "stout" load.

Next outing I took my single shot shotgun, bore was clear and easily observable being single shot, dropped a round in, took aim and pulled the trigger... there was a very loud explosion, blast of debris in my face and the gun went "limp"! When I recovered after a few seconds I found myself holding the action and buttstock in my right hand and forearm in my left hand. The barrel was laying on the ground about 10' in front of me with the entire top of the chamber missing!

Later examination showed lead streaks from where the case mouth was up to the forcing cone. My take is that the soft filled slug was obturating as it left (or maybe in) the hull then hit the forcing cone and just couldn't swage back down fast enough so pressure spiked. The BPS survived several shots seemingly unaffected but the single shot only took one round to destroy it.

I don't believe it was a fault in the gun because I should have paid attention to the punishing recoil and sticky extraction but at the time was not smart enough to see the over pressure signs.-- or at least respond appropriately to the over pressure signs.

I was very lucky and just got some minor cuts on my forehead and I lost about 40 decibels of hearing in my right ear... I was in the bush and like when hunting did not have shooting glasses or hearing protection. Stupid! And lucky! I am more careful now and I am very careful when working on slug loads substituting components. I make minimal subs and use low pressure data so there is a margin for error if pressures go up for some reason not evident to me.

Considering that a simple change of primer can affect pressure by up to 3000 PSI and crimp depth can have a similar effect, it is pretty easy to take a top end load over the top into dangerous territory with not much change in load/payload.

Okay not such a short story but worth repeating if it saves someone else's gun and/or body parts!

Play but play safe!

Longbow

No, I hadn't heard about this incident. Thanks so much for sharing. I'm glad you were okay. It definitely sounds like your slug may have obturated. I think from now on I may just fill the hollow base with hot glue which probably isn't hard enough to obturate the slug. Come to think of it, I also noticed lead streaks all the way along my barrel (which may be somewhat expected since this slug is nearly bore diameter but they were all the way along the barrel on the top and bottom so it would seem to support the idea the slug probably obturated.

Thinking about your note on crimp length, I also used a roll crimp which was longer than usual. In hindsight, I had a heavier payload, a hard plastic likely to obturate the slug (since the cavity is shaped like a cone it would actually be surprising if it didn't obturate), and a longer crimp. So I made a lot of mistakes (which is usually the way things end up going badly wrong).

In any case, this was the best type of incident that could happen. No one got hurt and it has jolted me out of complacency. Dangerous things are dangerous it turns out...Hopefully people can learn from this and avoid my mistakes.

[longbow]

If you haven't seen this it is an informative read:

http://www.armbrust.acf2.org/primersubs.htm

and this:

https://www.hodgdonreloading.com/eff...pth-shotshells

So, imagine that you picked a recipe that generating 10,500 PSI and you subbed a "hot" primer and you crimped extra deep and the payload was 5% to maybe 10% heavier. Any one of those could raise pressure to SAAMI max and a combination could put you well over SAAMI max.

Having said that, it seems to be the general opinion that modern shotguns are much overbuilt, but still, it deserves attention to details and conforming within reasonable limits or you risk a serious incident. As I said, my Browning BPS seems none the worse for wear after having some quite sticky extraction with those loads mentioned but Browning guns are reputed to be "well built" and likely could be rated to higher pressure, but a gun that just meets SAAMI specs is a different animal altogether!

Having experimented with hot melt glue, I can say that it does expand under pressure. I have used and am still using hot melt glue for attached tailwads and when a wad slug that is barely snug in the shotcup/barrel is fired with the hot melt glue tailwad, it is evident on the shotcup petals that the hot melt glue has expanded to squeeze the petals. Whether that translates into expanding a hollow base slug I can't say for sure and especially if the glue is fully in the cavity and slug skirt sitting on the wad column... in that case.

After my incident I have been careful of using hollow base slugs in short hulls in 3" chambers and filling cavities. I am quite sure the premature obturation in the chamber then resistance to swaging back at the forcing cone is primarily what caused the blow up of my gun. I do not recall details of primer and crimp so considering the above documents that may also have come into play.

Longbow

[mikehill85]

Very interesting stuff. Thanks for sharing. I will definitely be very careful about crimp length, payload weight, and hollow base fillers (and component substitution in general) from now on.

I honestly think the only reason I didn't end up with a really big problem is that modern shotguns are "overbuilt" like you say (not that you should count on that). I've read on some forums that shotgun shells don't show any signs of overpressure. It's very possible this used to be the case but at least in my case I was lucky enough that my shotgun was able to take the pressure and spit only the brass part of the hull out onto my shooting bench at which point I thought "Holy S**t!".

[mikehill85]

FYI,

I double checked my bore and I have lead deposits in my bore leading up to the forcing cone. See below photo (the white circle). It seems the slug almost certainly obturated. Yikes!

[longbow]

Yeah, I am not sure if it matters or not but my blow up I attribute largely to a filled slug obturating to full the chamber if not the hull, then slamming into the forcing cone. That it happened is not in doubt as the lead streaks showed it did happen. Was that the sole cause of the blow up? Was it because the slug was filled?

My understanding of the Lyman Foster slug is that it does obturate to fill the bore and I know for a fact it does get shorter and fatter after firing than it was before firing as I have collected them from soft snow after shooting and they are shorter and fatter matching the bore diameter where they start out at 0.705" diameter. However, unfilled they may obturate then swage back easily so not an issue.

I guess the only way to determine any effect of filler or type of filler would be to load an unfilled slug then then shoot and record pressure then repeat with slugs filled with a variety of "fillers" like hot melt glue, silicone caulk, wax, cornmeal, heavy grease, or whatever people have used, with nothing else changed.

I have made forms to put the slug into then filled hollow cavity and extend into the form with hot melt glue to make a tailwad. I know that glue tailwad does expand under pressure because the shotcup petals show compression where that glue tailwad squeezes them. These have been wad slugs of course and all cast from ACWW or range scrap so harder than pure lead.

I have not seen signs of over pressure with these but wonder if the HB cavity being filled could possibly lead to the same obturation in chamber then pressure spike at forcing cone. Since the slugs have been harder lead than the Lyman Fosters that were showing sticky extraction I am not sure if they were cast softer would that be a problem? Since the filler is elastic, maybe?

My current tack is to use screwed on tailwads so the cavity isn't filled leaving the HB slug to respond as it normally would to a choke of whatever. I don't think an elastic tailwad sitting behind the slug is an issue as it can freely compress. When that same elastic material is acting hydraulically under compression of powder gasses inside a hollow cavity I am not so sure how the filled slug responds to a constriction. Things happen in milliseconds in a gun barrel.

Point here being is that your nylon filled slug may be obturating due to the hydraulic reaction of compressed nylon and not able to squeeze down fast enough to avoid a pressure spike.

It is all a bit of speculation on my part but I want to keep things safe so will err on the side of safety. One blow up was enough!

Longbow

[mikehill85]

I agree. Better the err on the side of caution. Check out the below photos of one of the recovered slugs. All the ridges are completely flattened all the way around the slug (probably from obturating in the barrel) and the layer lines of the print are clearly etched into the interior. The slug completely burst open from the nose down. Accuracy was atrocious. I assume this was caused by the tail wads not holding up.


Flattened Ridges


More Flattened Ridges on the Other Side


3d Print Layer Lines


The Recovered Slug

[longbow]

Having looked more closely at your nylon tailwad I have another couple of comments...

The original style wads don't fill the hollow base, They have a post that slips over a pillar cast in the slug. By filling the cavity the nylon may be hydraulically swaging the slug skirt against the bore creating high bore friction and explaining the swaged to non-existence grooves.

Not sure how much the nylon tailwad collapses under pressure. I notice that you have used a design similar to the Gualandi style cushion leg but... I believe that when a cushion leg is removed from a recipe calling for one that pressure spikes due to less volume at ignition (lack of cushion collapse). This is my opinion based on some results I got and comparing short hull loads (no cushion leg) with regular loads using cushion leg. Also, from what I interpret the effect seems to be less of an issue with slow powders than fast powders which makes sense.

I have no proof of this but some loads I put together where I removed the cushion leg wad and used a solid wad column, with no other changes, and got sticky extraction I decided to do some cross referencing and came to the conclusion that it at least makes sense that by removing the cushion leg there is less volume at ignition so pressure may peak sooner. Just another one of those little variables that can affect pressure.

So, if the nylon tailwad is hydraulically swaging the slug skirt against the bore and the "cushion" on your wad is stiff that could easily explain the results you are getting.

It would be nice to do some pressure testing to check the effect of cushion leg or lack of for comparison.

Not sure how much testing would be required but at least 5 rounds each using cushion leg and again with solid wad column for a fast powder and of a slow powder to check. That would be 20 rounds using just two powders. I wonder if we could talk Blood Trail into doing it? I'd help finance the testing with supplies or cash.

Longbow

[Cap'n Morgan]

In case you missed it, I have posted several times about my experience blowing up a shotgun, Not fun!

Since you mentioned blow-ups I might as well relate an experience of my own. Although it happened with a rifle, it has some similarity to your mishap
(and MegaMag's S.E.E "myth" )

Back in the late seventies i bought a Swedish M96 rifle. Later I also bought several hundreds 156 grains 6.5x55 Danish mill surplus ammo
(M96 was our military rifle for a few years after the war) The rifle appeared brand new, and I doubt it had ever been used, much less fired.

Well, I enjoyed the rifle and shot it from time to time. Then one day while studying my "bible", The Book of Rifles, I came across a warning
in a chapter of Swedish rifles. It mentioned a specific lot of Danish mill surplus ammo in 6.5x55 which had caused several blow-ups on Danish shooting ranges.
The headstamp was clearly described, and (you guessed it) it matched my cartridges!

That gave me something to think about, I wasn't rolling in money at that time and didn't fell like scrapping the lot.
The book said the problem was caused by fouling due to too the jackets being too soft, and I decided to try to reduce the load a little and maybe avoid fouling.
I pulled the bullets from four cartridges, weighed the powder and loaded the cartridges again with a 10% reduced load (weighing each load on my Ohaus 1010)
and, together with a couple of friends, went to test the load.

The first two rounds fired as expected, and I remember telling my pals that the load seemed quite mild for a 10% reduction. Then I fired the third round...

I can't remember hearing any boom, but I remember distinctly the feeling of warm blood running down my nose.

To make a long story short, here's what had happened: The bullet never left the barrel. It was lodged firmly in the throat of the chamber with the rear of
the bullet deformed and expanded (I later tapped the bullet out from the front without using much force) Since the pressure had nowhere to go, it went
out the rear of the case, into the firing pin hole and blew the firing pin rearwards with such a force that the 1/4" pin snapped and the rear part flew back
hitting the knuckle on my thumb (four stitches) then hitting right between my eyebrows (two stitches) before taking off for places unknown.

After a visit to the emergency room, and a cock-and-bull story about a bench drill job gone wrong, I was non the worse for wear, but a little shaken...

When I later examined the rifle, it was obvious that the reason the blow-back had such a disastrous result was the vent holes in the M96 bolt were too small,
compared to the two large slots in a M98 bolt it's obvious that Mauser learned something between model 96 and 98.
I replaced the parts in the bolt, including the mainspring that was reduced to half length, "sporterized" the rifle, and continued to use it for hunting for the next
twenty years (and I enlarged those vent holes!)

I'm not quite sure what happened that day back then. But I'm sure it was the same thing that had happened on the other Danish shooting ranges, and by reducing
the loads I had actually increased the likelihood for the blow-back to happen.

[Blood Trail]

As reloaders, we tend to forget about how slug columns affect pressure: hard verses soft launch.

When I sent Uncle D’s 580 gr Fury slugs to be tested before I purchased my Pressure Trace 2, I sent five loads off. Two of those were with 38 grs of Blue Dot with a hard finer wad stack up and the other was with 40 grams of steel sitting on a brush wad.

Surprisingly enough, the steel load came in around 7.5-8k psi while the Blue Dot load was around 11k psi. I know that you get more velocity on a lower pressure curve with steel than Blue Dot but I didn’t think it would be that drastic. The crush section really helped tame pressure.

From my testing with my pressure trace 2, looks like your loads were 20k psi or higher.

Good thing is, most modern shotguns are overbuilt. Tom Roster was hired by Remington to test their 870 barrels to failure. They didn’t blow until 55k psi.


Sent from my iPhone using Tapatalk

[mikehill85]

Having looked more closely at your nylon tailwad I have another couple of comments...

The original style wads don't fill the hollow base, They have a post that slips over a pillar cast in the slug. By filling the cavity the nylon may be hydraulically swaging the slug skirt against the bore creating high bore friction and explaining the swaged to non-existence grooves.

Not sure how much the nylon tailwad collapses under pressure. I notice that you have used a design similar to the Gualandi style cushion leg but... I believe that when a cushion leg is removed from a recipe calling for one that pressure spikes due to less volume at ignition (lack of cushion collapse). This is my opinion based on some results I got and comparing short hull loads (no cushion leg) with regular loads using cushion leg. Also, from what I interpret the effect seems to be less of an issue with slow powders than fast powders which makes sense.

I have no proof of this but some loads I put together where I removed the cushion leg wad and used a solid wad column, with no other changes, and got sticky extraction I decided to do some cross referencing and came to the conclusion that it at least makes sense that by removing the cushion leg there is less volume at ignition so pressure may peak sooner. Just another one of those little variables that can affect pressure.

So, if the nylon tailwad is hydraulically swaging the slug skirt against the bore and the "cushion" on your wad is stiff that could easily explain the results you are getting.

It would be nice to do some pressure testing to check the effect of cushion leg or lack of for comparison.

Not sure how much testing would be required but at least 5 rounds each using cushion leg and again with solid wad column for a fast powder and of a slow powder to check. That would be 20 rounds using just two powders. I wonder if we could talk Blood Trail into doing it? I'd help finance the testing with supplies or cash.

Longbow

Yes, it would be very interesting to see how wad cushioning affects pressure. Based on my qualitative examination of Nylon vs the materials that factory wads are made of I would say Nylon is much harder and definitely wouldn't provide as much cushioning.

I was trying to choose a material I thought could survive being fired in one piece and although it seems it more or less accomplished that I do think the lack of cushioning is one of the major contributors to the pressure spike (probably along with swaging the slug in the chamber). If you look at a lot of more modern mechanical devices with injection molded plastic parts you'll find a lot of times gears are made of Nylon (because it is tough and self-lubricating). I was thinking of using something like TPU/TPE but I think that might be too flexible. That has more or less the properties of rubber.

In any case, I have decided to try shooting this slug again using hot glue as a filler, two nitro cards under the slug, and an FS12 gas seal on the bottom. I believe that this will not result in pressure spikes. The FS12 gas seal should provide cushioning and the payload isn't any heavier than the Lyman 525 payload which had no pressure signs (and I've fire 100s of such slugs without incident...In some cases completely replacing the original wad with nitro cards...). This time I will definitely be checking the shells for pressure signs every step of the way.

[mikehill85]

Since you mentioned blow-ups I might as well relate an experience of my own. Although it happened with a rifle, it has some similarity to your mishap
(and MegaMag's S.E.E "myth" )

Back in the late seventies i bought a Swedish M96 rifle. Later I also bought several hundreds 156 grains 6.5x55 Danish mill surplus ammo
(M96 was our military rifle for a few years after the war) The rifle appeared brand new, and I doubt it had ever been used, much less fired.

Well, I enjoyed the rifle and shot it from time to time. Then one day while studying my "bible", The Book of Rifles, I came across a warning
in a chapter of Swedish rifles. It mentioned a specific lot of Danish mill surplus ammo in 6.5x55 which had caused several blow-ups on Danish shooting ranges.
The headstamp was clearly described, and (you guessed it) it matched my cartridges!

That gave me something to think about, I wasn't rolling in money at that time and didn't fell like scrapping the lot.
The book said the problem was caused by fouling due to too the jackets being too soft, and I decided to try to reduce the load a little and maybe avoid fouling.
I pulled the bullets from four cartridges, weighed the powder and loaded the cartridges again with a 10% reduced load (weighing each load on my Ohaus 1010)
and, together with a couple of friends, went to test the load.

The first two rounds fired as expected, and I remember telling my pals that the load seemed quite mild for a 10% reduction. Then I fired the third round...

I can't remember hearing any boom, but I remember distinctly the feeling of warm blood running down my nose.

To make a long story short, here's what had happened: The bullet never left the barrel. It was lodged firmly in the throat of the chamber with the rear of
the bullet deformed and expanded (I later tapped the bullet out from the front without using much force) Since the pressure had nowhere to go, it went
out the rear of the case, into the firing pin hole and blew the firing pin rearwards with such a force that the 1/4" pin snapped and the rear part flew back
hitting the knuckle on my thumb (four stitches) then hitting right between my eyebrows (two stitches) before taking off for places unknown.

After a visit to the emergency room, and a cock-and-bull story about a bench drill job gone wrong, I was non the worse for wear, but a little shaken...

When I later examined the rifle, it was obvious that the reason the blow-back had such a disastrous result was the vent holes in the M96 bolt were too small,
compared to the two large slots in a M98 bolt it's obvious that Mauser learned something between model 96 and 98.
I replaced the parts in the bolt, including the mainspring that was reduced to half length, "sporterized" the rifle, and continued to use it for hunting for the next
twenty years (and I enlarged those vent holes!)

I'm not quite sure what happened that day back then. But I'm sure it was the same thing that had happened on the other Danish shooting ranges, and by reducing
the loads I had actually increased the likelihood for the blow-back to happen.

Thanks for sharing. Glad you were okay. It is funny that sometimes the very measures we take to prevent something from happening actually cause that thing to happen/make it worse.

[mikehill85]

As reloaders, we tend to forget about how slug colons affect pressure: hard verses soft launch.

When I sent Uncle D’s 580 gr Fury slugs to be tested before I purchased my Pressure Trace 2, I sent five loads off. Two of those were with 38 grs of Blue Dot with a hard finer wad stack up and the other was with 40 grams of steel sitting on a brush wad.

Surprisingly enough, the steel load came in around 7.5-8k psi while the Blue Dot load was around 11k psi. I know that you get more velocity on a lower pressure curve with steel than Blue Dot but I didn’t think it would be that drastic. The crush section really helped tame pressure.

From my testing with my pressure trace 2, looks like your loads were 20k psi or higher.

Good thing is, most modern shotguns are overbuilt. Tom Roster was hired by Remington to test their 870 barrels to failure. They didn’t blow until 55k psi.


Sent from my iPhone using Tapatalk

Interesting. It makes sense it would have to be considerably over SAAMI spec pressure. Like you said, it's definitely a good thing that modern shotguns are overbuilt. Otherwise I'm pretty sure I'd at least be looking at replacing the shotgun (if not some fingers). I checked the barrel and everything is totally fine. There's not so much as a nick on the bolt lock either so it survived it shockingly well.

One thing I was wondering about was how the entire plastic portion of the shell was ripped off of the brass (which is the first thing I noticed that threw up huge alarm bells for me). I guess the pressure must have built before the roll crimp was able to unravel and just created a crazy slug cut shell. Lol. It's also interesting how some of them are torn. Maybe that's because the slug expanded in the chamber and literally just ripped parts of the shell out and took them with it.

[Frosty Boolit]

Mike, I thought of something cool when I saw your original printing capability. What if you printed an aerodynamic slug that just had a hole along its axis that stopped short about 1/4" from the bottom and maybe it's .456" diameter so a 45/70 405gr boolits fits snug in it. Then you'd have a "sabot" that's actually the bullet too, with the lead boolit providing the weight that the plastic doesn't.

[mikehill85]

Mike, I thought of something cool when I saw your original printing capability. What if you printed an aerodynamic slug that just had a hole along its axis that stopped short about 1/4" from the bottom and maybe it's .456" diameter so a 45/70 405gr boolits fits snug in it. Then you'd have a "sabot" that's actually the bullet too, with the lead boolit providing the weight that the plastic doesn't.

That's an interesting idea. It should theoretically work. The center of mass will be up towards the nose. I'd just have to design a tail to move the center of pressure to the back. Wasp-waisted designs (like a giant airgun pellet) tend to seem to work well.

[mikehill85]

I tested out the Svarog slugs again using two nitro cards on a FS12 gas seal. I saw pressure signs again. These weren't as bad as last time where I got torn shells but I could still see primer cratering and extractor marks.

I tried the same thing with the Lyman 525 slug (two nitro cards on an FS12 gas seal) and got the same pressure signs. It seems that replacing the original wad system gets pressure spikes, as LongBow and others pointed out.

Aside from this, I reloaded some Lyman 525 slugs with original wads and my 3d printed sabots and got some pretty good results today...Including a 1.3" 5 shot group (my best group was on the last 5-shots of the day no less!) at 50 yards...Probably my best outing to date.

Anyway, I just wanted to thank everyone for the support. The current performance of the reloads (from cheap Walmart birdshot at about $0.24/each) is exceeding my expectations and I definitely couldn't have gotten there with out your help/suggestions/advice.

[Cap'n Morgan]

Fine looking groups!

But I must repeat, and I can't stress this enough: NEVER substitute a compressible wad with a non-compressible one!

(Stop me if I'm getting long winded here, but...)

With fast burning powder maximum pressure is reached in about half a millisecond, and it peaks before the payload has begun to move.
A compressible wad is actually a form of "filler" - it takes up space and keep the powder up against the primer, but as the pressure rise
the wad compresses and increase the volume behind the payload. The pressure is directly related to volume, doubling the volume will
reduce the pressure by half, but it works both ways! When you add a non-compressible wad, you're reducing the volume = increasing pressure.
If you want to use a solid wad and a x12x seal it's perfectly alright, just reduce the amount of powder to make up for the reduced volume.

[mikehill85]

Fine looking groups!

But I must repeat, and I can't stress this enough: NEVER substitute a compressible wad with a non-compressible one!

(Stop me if I'm getting long winded here, but...)

With fast burning powder maximum pressure is reached in about half a millisecond, and it peaks before the payload has begun to move.
A compressible wad is actually a form of "filler" - it takes up space and keep the powder up against the primer, but as the pressure rise
the wad compresses and increase the volume behind the payload. The pressure is directly related to volume, doubling the volume will
reduce the pressure by half, but it works both ways! When you add a non-compressible wad, you're reducing the volume = increasing pressure.
If you want to use a solid wad and a x12x seal it's perfectly alright, just reduce the amount of powder to make up for the reduced volume.

I agree and thanks for the stern warning it is well taken. I've learned my lesson. The trouble with the cheap bird shot is the propellant is quite clearly very fast burning (there's only about 17.9 grains of the propellant and it managed to cause the pressure signs seen on this page and page 6 of this thread).

These types of loads have collapsing wads and you can't substitute them for anything else (not without playing Russian Roulette anyway). I thought the FS12 gas seal would give me a enough cushion because it is a cushioned gas seal but this clearly wasn't enough and I won't be trying that (or any type of wad substitution/weight payload increase (although I did that by accident), etc.,) ever again. I enjoy having all my fingers, eyes, etc., too much for that.

At the end of the day, I think the results of the 3d printed sabots speak for themselves and this experiment has been a success. I went from about 3"-4" groups with the stock shot cups to groups under 1.5" with sabots that cost pennies printed on a 3d printer that costs $200-$250 (and can be used for any number of other things). I can live with that and not touch the wad or any other part of the system.

I will definitely be experimenting more with the Svarog slug but not until I can get all the components for a known safe load.

[longbow]

Yes, I am on board with Cap'n Morgan and his explanation.

For the most part my slug loads have been loaded over Blue Dot. Two main reasons: 1) I started loading heavier than 1 oz. slugs (0.735" RB's actually) using Precision Rifle's loading specs for their PileDriver slug of 610 grs. and using Blue Dot; 2) I checked heavy birdshot loads and found recipes using Blue Dot and wads with little or no cushion leg.

Subsequently I looked at short hull loads with no cushion leg and compared to regular length hull loads with cushion legs. It appeared that they seemed to use less powder for same pressure and payload or ran higher pressure for same powder and payload as regular length hulls with cushion legs. This seemed to me to be more obvious with faster powders but my "research" was pretty crude and just cross referencing load data. Pressure testing would be the way to go.

So, I am cautious about removing cushion legs.

What would also be nice is to get hold of some old loading data before plastic wads and gas seals when only nitro cards, hard card wads and/or fiber wads were used. From my limited experience there is a lot of blow by/leakage so I am betting powder charges were larger for same pressure if a plastic gas seal is used. What percent increase in powder? Is it predictable? I have a bit of old timey reloading info but not a lot. I have looked but it seems not much is readily available. There are some sites where people post recipes for old shotguns and using card wad columns but I have as yet to turn up an old loading manual listing a variety of powders and payloads.

Also, on a slightly different topic, you mention types of plastics for 3D printing your wads. Not sure if you have seen them but Cap'n Morgan has a thread or two on his development of full bore and sabot style slugs here:

https://castboolits.gunloads.com/sho...light=brenneke
https://castboolits.gunloads.com/sho...light=brenneke

and BigMrTong here:

https://castboolits.gunloads.com/sho...highlight=slug
https://castboolits.gunloads.com/sho...highlight=slug
https://castboolits.gunloads.com/sho...highlight=slug

Cap'n Morgan isn't 3D printing and he has skills and access to equipment most of us don't but very good info and likely some info on the plastics he used so you could compare properties.

BigMrTong 3D printed his rocket fins and sabots so again there is likely some useful info there.

Both have been very helpful when I asked questions and I am still waiting on a friend to 3D print me some hybrid rocket fin designs where I have used info from both Cap'n Morgan and BigMrTong.

If you have seen those threads just ignore me, I am rambling again!

Longbow

[mikehill85]

Yes, I am on board with Cap'n Morgan and his explanation.

For the most part my slug loads have been loaded over Blue Dot. Two main reasons: 1) I started loading heavier than 1 oz. slugs (0.735" RB's actually) using Precision Rifle's loading specs for their PileDriver slug of 610 grs. and using Blue Dot; 2) I checked heavy birdshot loads and found recipes using Blue Dot and wads with little or no cushion leg.

Subsequently I looked at short hull loads with no cushion leg and compared to regular length hull loads with cushion legs. It appeared that they seemed to use less powder for same pressure and payload or ran higher pressure for same powder and payload as regular length hulls with cushion legs. This seemed to me to be more obvious with faster powders but my "research" was pretty crude and just cross referencing load data. Pressure testing would be the way to go.

So, I am cautious about removing cushion legs.

What would also be nice is to get hold of some old loading data before plastic wads and gas seals when only nitro cards, hard card wads and/or fiber wads were used. From my limited experience there is a lot of blow by/leakage so I am betting powder charges were larger for same pressure if a plastic gas seal is used. What percent increase in powder? Is it predictable? I have a bit of old timey reloading info but not a lot. I have looked but it seems not much is readily available. There are some sites where people post recipes for old shotguns and using card wad columns but I have as yet to turn up an old loading manual listing a variety of powders and payloads.

Also, on a slightly different topic, you mention types of plastics for 3D printing your wads. Not sure if you have seen them but Cap'n Morgan has a thread or two on his development of full bore and sabot style slugs here:

https://castboolits.gunloads.com/sho...light=brenneke
https://castboolits.gunloads.com/sho...light=brenneke

and BigMrTong here:

https://castboolits.gunloads.com/sho...highlight=slug
https://castboolits.gunloads.com/sho...highlight=slug
https://castboolits.gunloads.com/sho...highlight=slug

Cap'n Morgan isn't 3D printing and he has skills and access to equipment most of us don't but very good info and likely some info on the plastics he used so you could compare properties.

BigMrTong 3D printed his rocket fins and sabots so again there is likely some useful info there.

Both have been very helpful when I asked questions and I am still waiting on a friend to 3D print me some hybrid rocket fin designs where I have used info from both Cap'n Morgan and BigMrTong.

If you have seen those threads just ignore me, I am rambling again!

Longbow

No, not at all. Those are some great insights. I agree, it would be very interesting to find old load data on what people used before plastic sabots.

One thing I'd really like to figure out is what kind of powder I am dealing with. I haven't found good data on what it is that Federal uses in their Field and Target Loads. Maybe it varies or they keep it under wraps but if I knew what powder it was I could perhaps find a safe known load for non-collapsing tail wads.

Yeah, I was trying to get a line on some Blue Dot but everything is sold out atm. I have e-mail alerts out for when it does come available again though. I definitely think a slower burning powder is in order for slugs like the Lyman 525 (at least to get it up to velocities that would allow you to stretch out past 50 yards).

Those threads are great! Thanks for sharing! Really cool stuff from Cap'n Morgan and BigMrTong. By complete coincidence I actually ordered the Lee Drive Key 7/8 oz slug mold today, since I had been watching it and the price dropped. I like the fact the drive key slug has the section in the middle which you can attach something to so that I would definitely transfer the spin from my rifled choke tube. Also the fact the 7/8 oz slug is a lighter payload than the loads I'm repurposing should help keep pressures down. Once I get it, I'll play around with some designs to get it up to bore diameter (while reusing the collapsing wad). If I do that, the pressures should be lower than with the lead birdshot load because that payload is heavier.

I have had this mold in the past but it galled. I think I was probably not lubricating it properly and running it too hot. I recently built my own PID controller which monitors and controls the pot temperature to within 5 F or so, so I'm hoping this time the mold will last longer.

Looking at Cap'n Morgan's thread reminded me of another interesting thing about 3d printing. With fairly sparse equipment you can create negatives for aluminum castings. You basically take a plastic 3d printed negative, put that negative in a mix of plaster of Paris and play sand (and let it harden), burn out the plastic negative, and fill the now empty cavity with molten aluminum. I have done this successfully in the past with things like statues. I'm not set up to do it right now but down the road I might look at doing this to make a slug mold. I'd probably need to clean up the casting afterwards but I think it's a plausible method to make your own custom aluminum slug mold.

Below is an example of a statue I cast in Aluminum (I built an Aluminum smelting furnace out of an old galvanized steel bucket, refractory cement, and a propane torch for burning weeds). It's not perfect but you get the idea. You can cast just about any shape you can imagine and it definitely holds detail...You can even see the layer lines from the 3d print.