SpudFiles

Lockednloaded did you make the circuit yourself, or if not what's it from?

sharpshooter11000 wrote:Lockednloaded did you make the circuit yourself, or if not what's it from?

I pulled it out of a butane lighter and just hooked up a battery pack to it. Simple stuff if you can find a suitable ignitor

So a battery powered butane lighter?

It was a long nose lighter with continuous spark and a single AA battery

Crowley, why didn't you just toss some steel plate at the back of this backstop? Even 12mm plate will reliably stop a 10mm bearing at any speed you're going to achieve with a low pressure hybrid.

ITWOST: The range of machining capabilities at my disposal are in the process of improving DRAMATICALLY

DYI wrote:Crowley, why didn't you just toss some steel plate at the back of this backstop? Even 12mm plate will reliably stop a 10mm bearing at any speed you're going to achieve with a low pressure hybrid.

I don't have any steel plate, let alone any metal material at all that could be a backstop.

Wouldn't there be a risk steel plate would ricochet the ball bearing anyway?

I don't have any steel plate, let alone any metal material at all that could be a backstop.

Wouldn't there be a risk steel plate would ricochet the ball bearing anyway?

Ricochets become an issue when the projectile's path is not orthogonal to the plate, and/or when using very hard targets. Most steel plate one would find hanging around as scrap is not nearly hard enough for ricochets to be an issue with steel rounds.

Every time I've fired a steel ball bearing at a steel plate, the ball has landed within a few metres of the target. This extends to all other steel projectiles I've used, although most of them have been softer. In fact, the only incidence I've heard of a member here achieving a ricochet was Spudfarm's case a few years ago, and he was firing a hardened and tempered steel dart at an extremely hard high carbon steel or tool steel target (which was much harder than the projectile).

Also, how the hell do you have no steel plate after building launchers for something like five years?

DYI wrote:Also, how the hell do you have no steel plate after building launchers for something like five years?

Dunno... never come across any and never really needed any. I almost 'borrowed' a piece of cast iron plate that I found on the side of the road a few years ago but that was before I could drive and I didn't want to carry it home

ITWOST:

Went to my shooting location the last two days. First day I got good results. Today I didn't get a single result, all false readings on the chrony. After the last shot I think I found the problem, I may have been shooting wide or high.

What happened on the last shot? Well I shot a 10mm saboted ball bearing and it hit one of the 4mm metal guide rods (made from No.8 wire). I had a small adjustable woodworking bench to rest the gun on and stop it from moving side to side much but I guess upon ignition it still manages to jump around enough and throw off the aim even though i'm only 3m away from the chrony.

This cannon continues to be pretty freakin' loud even when out in the open and shooting a projectile. A lady driving a car from the Navy came past after the first shot and considering the road next to where I shoot doesn't lead anywhere, it just loops around, I assume they could possibly hear me from 400m down the road. Video up in a few hours perhaps, pity the audio doesn't do it justice.

Oh and I noticed after the last shot there was a small bulge in the copper barrel, opinions people?

I'm no expert, but I think that barrel may tear open on you at some point soon. Maybe part of the sabot broke loose and smashed the side of the barrel.

The sabot was a dense, hard foam so it's not that. Could be the projectile itself if the sabot was being torn apart inside the barrel.

I got two readings of 1400fps with this particular sabot, HGDT reckons I should be getting 2100fps. Say HGDT is off by 10% and then minus another 10% for the chrony being 10' away and then minus a little more for a imperfect sabot and 1400fps sounds about right for a 4.1g projectile from a 0.78" x 40" barrel at a 10x mix.

DYI wrote:Crowley, why didn't you just toss some steel plate at the back of this backstop?

... or a garage

The range of machining capabilities at my disposal are in the process of improving DRAMATICALLY

Oh, do tell...

The sabot was a dense, hard foam so it's not that. Could be the projectile itself if the sabot was being torn apart inside the barrel.

We've had this conversation before, the sabot is most likely breaking up inside the barrel. What of those compressed foil sabots I had recommended

jackssmirkingrevenge wrote:We've had this conversation before, the sabot is most likely breaking up inside the barrel. What of those compressed foil sabots I had recommended

This is a different material, got better results too

The tin foil never worked well, could only get the 1200fps readings like the cotton ball sabots. Can't remember why the tin foil ones didn't work out well, either they didn't allow me to get close enough to the chrony, they were too heavy (they pushed the weight to about 7 or 8g instead of 4g) or they were difficult to make so they fit the barrel well.

I don't think this foam is that bad, it's quite tough stuff and I cut it to about 1" lengths so I think it holds up reasonably well in the barrel. I am still looking for a light and tough sabot but the foam works for now.

MrCrowley wrote:I am still looking for a light and tough sabot but the foam works for now.

UHMWPE + friend with a lathe

Foam makes poor sabots by themselves. They change size when under pressure. I have shot swim noodle sabots past a golf ball in a 2 inch barrel. At 7 bar, they tend to shrink to about 1/4th the original size.

A plastic cup or 1/2 a plastic bottle works much better.

DDT can cause this.