Science Fair Project Safety Assessment


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manithree
December 3, 2012, 07:43 PM
My 13 year-old son who thinks that "Science Fair Project" comes from the latin root meaning "Excuse to re-load and chronograph" doesn't like to shoot my current loads out of our S&W snubbies. So, for next year's project he wants to make a .38 Special load that's light enough to be fun to shoot, even for him.

We already use Trail Boss to make some really soft .22-250 loads. But based on the massive case capacity of .38 spl, even published TB loads would still be pretty similar to what we're getting with a 158g bullet over 2.7g of Clays.

So, he wants to wildcat. Sort of. Since most reloading books and manuals I've seen warn against going too far below the published minimum loads, he decided to try lowering case capacity of .38 spl by just cutting the case down. Then we'll measure the usable case capacity and apply Hodgon's published 70% rule for Trail Boss using our new .38-based wildcat.

The lowest published Trail Boss load (that I've found) for a 158g lead bullet is 2.7g (661 fps). We're wondering if we can get usable case capacity down to 1.0-1.5 grains since Trail Boss is not very dense.

Does anybody know of a reason why Hodgon's published Trail Boss rules for any pistol cartridge wouldn't be safe for a shortened .38 spl cartridge? We plan to be very careful not to compress the powder, and watch closely for squibs. Those seem like the biggest safety risks for this project, but I've only been re-loading for a few years, so I'll be interested to hear how more experienced re-loaders would assess the risks involved. Especially while we still have plenty of time to choose another science project for next year.

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rcmodel
December 3, 2012, 07:50 PM
for a 158g lead bullet is 2.7g (661 fps).661 FPS is about as low as you can safely go and insure a bullet doesn't get stuck eventually.

No matter how short or small the case is.

Then there is the matter of seating & crimping a much shorter case, cause your standard .38 Spl seating die will no longer do it.

Then there is this:
http://www.midwayusa.com/product/511908/magtech-sport-ammunition-38-special-short-125-grain-lead-round-nose-box-of-50

rc

snakeman
December 3, 2012, 07:52 PM
the only thing I can think of is that the bullet might not ever leave the bore. this would result in the next shot blowing your gun and possibly the shooter to heck. I would play it safe and teach him to handle recoil. I know that may sound mean but if he's not ready to handle 38 special then let him shoot a 22

rcmodel
December 3, 2012, 07:55 PM
BTW: If you want less recoil, use 125 RNFP or 148 WC grain bullets instead of 158 grain bullets.

It will make more difference in recoil then trying to download them to unsafe velocity levels.

ScratchnDent
December 3, 2012, 07:57 PM
I've no experience with Trailboss powder, so I can't offer any advice there.

I am just curious about why you would use 158 gr bullets if the goal is lighter recoil?

Wouldn't a 110 or 120 or so bullet be better suited?

greenlion
December 3, 2012, 10:15 PM
As a science teacher, I would point out that science fairs always, in my experience, prohibit the use of explosives, firearms, weapons, and flamable substances in experiments. He will definitely will not be allowed to conduct that as a school science fair experiment. If he is, you need to question how far behind the times your school system's safety procedures are. The school would be held liable if he injured himself during a science project they have approved.

manithree
December 3, 2012, 11:43 PM
First, my son is a fine shooter. He shoot's 9mm and .40 handguns, .22-250, 7.62x39, 7.62x54r and .30-06 almost as well as I do.

Second, we'll probably start with 158g because I have over a thousand 158g bullets (they were on sale!). I may end up getting some lighter projectiles, but since we can't actually measure recoil, for a science project, it really won't matter much.

Third, last year's (6th) grade science project involved chronographing a whole bunch of reloads and commercial ammo. He got first place in his school, placed at district, and went to the Central Utah Science and Engineering fair. We are well aware of Utah's science fair rules.

What I'm really looking for is technical advice on safety issues that I haven't already thought of. I did mention in my initial post that we're aware that ultra-light loads have the potential for squibs. Some failure and re-configuring parameters isn't a bad thing in a science project, and occasionally leads to whole new avenues of exploration.

One thing I did neglect to mention is that we will probably never put more than one round in the cylinder at a time since we won't be able to crimp them. And we plan to check after every shot for squib/barrel obstruction.

661 FPS is about as low as you can safely go and insure a bullet doesn't get stuck eventually.

Are there any equations or rules for determining the minimum velocity required to exit the barrel?

I've never pushed a squib out, and I don't really want to, so we'll probably start high and work down.

My son has seen the Magtech Spcl Shorts. That's one of the things that influenced him to do this. That and we couldn't really decide if putting a gas check on a wax bullet was feasible or not. We have shot a few hundred wax bullets, but the primers always backing out is quite irritating.

Measuring powder density, calculating how much of the case to remove to get the desired usable volume, and measuring velocities are all good math and science for a project. I don't expect us to make something commercially viable, or even anything we'll ever use again. I just want him to have fun and learn. Safely, of course.

greenlion
December 4, 2012, 06:10 AM
I still cannot imagine a school teacher/school/system signing off on a science project that encourages a very young student to go try out experimental handloads, that his father is also not too sure about, in a firearm. (Even if it is in Utah, which might as well be Mars if this is true)

In today's litigious world, you cannot even have then put their hands behind their heads when they do sit-ups in PE class for fear that they would crick their necks...

56hawk
December 4, 2012, 10:32 AM
661 FPS is about as low as you can safely go and insure a bullet doesn't get stuck eventually.

Lyman 49th lists a 38 S&W load at 451 fps. I shot a few rounds at this velocity in other calibers and they worked just fine. For an experiment you are only going to be shooting one round at a time, so getting a squib won't be any big deal anyway. Just have a brass punch and a hammer on hand.

rcmodel
December 4, 2012, 12:15 PM
We have shot a few hundred wax bullets, but the primers always backing out is quite irritating.You have to drill out the primer flash holes with a 1/8" drill to prevent that.

rc

jmorris
December 4, 2012, 01:35 PM
You might try SASS forums for very light load data. Cowboy action loads are super soft, a spit ball fired by a 4th grader have higher power factors.

I'll never forget a friends story about a derringer side match where the shooter fired 2 shots at a 3/8" plywood target (105 grain bullet under 600 fps), finished and waited on the RO for commands, then looked around to find him on the ground because the bullet bounced back off the wood and hit him in the jewels.


Come to think of it the old SSR loads in IDPA (before ESR existed) was a 230 grain going under 550 fps making 125pf, shot thousands and thousands of them, never stuck a single one.

manithree
December 4, 2012, 03:02 PM
You might try SASS forums for very light load data.

Very nice. Thank you.

manithree
December 4, 2012, 03:03 PM
Lyman 49th lists a 38 S&W load at 451 fps.

Heh. I own that manual, too. I go to hodgdon.com first for my re-loading data and just never got around to finishing my dead-tree searching.

One of the original ideas was to cut to nearly .38 S&W, then use a Lee .38 S&W trimmer to clean up. Then we should be able to safely use any published .38 S&W load. Right?

56hawk
December 4, 2012, 03:39 PM
One of the original ideas was to cut to nearly .38 S&W, then use a Lee .38 S&W trimmer to clean up. Then we should be able to safely use any published .38 S&W load. Right?

Should work, especially since the 38 S&W runs at lower pressure. By the way, since this is just for a science fair project you could use full length 38 special cases and just seat the bullet deeper. The 38 Special case is about the same length as a 38 S&W loaded with a 158 grain bullet.

kingmt
December 4, 2012, 03:50 PM
The more you shorten the case the faster the pressure will climb. So even tho recoil goes down the pressure is still going up. Instead of cutting the brass off just push the bullet deeper. I'd also look at 9mm data. If there it's 9mm TB data it would give you some good data to reference. The heavier bullet will gone you less recoil unless it is to light to allow any pressure to build.

rsrocket1
December 4, 2012, 07:41 PM
A shorter case would do the same as what kingmt recommends, but watch out. I did a sample run of what would happen if you pushed a .63" bullet flush with the .38 case and loaded it with 1.5g Clays in a 4"bbl:
seat depth Max press MV
.53 8,7665 542fps
.63 12,062 578fps
.73 19,812 625fps

+/- 0.1" seat depth get you from too little pressure with unburned powder and sooty case to going over the SAAMI limit for the 38 special gun. Much more than that and you get a Kaboom.

I would instead do an experiment of "how low can you go" before you get a stuck bullet. You are only shooting one at a time and hopefully you know how to drive a stuck bullet out of a barrel w/o damaging the gun. If you use a standard bullet seating and start with 2.5g Clays, I'll bet you can get down to 1.5g Clays and still get a chrony reading.

With a hardcast lead bullet, I once had an accidental squib load with just the primer and I chrony'ed the bullet at 231fps.

Andrew Leigh
December 4, 2012, 11:49 PM
Manithree,

just a thought, with all of the negative issues being experienced in schools with firearm related incidents do you think such a project will be welcomed? Your son could be marked down as a result or the project may well not be accepted. Also how does he demonstrate the results of the project?

Good luck with the project.

manithree
December 5, 2012, 12:59 AM
I'll bet you can get down to 1.5g Clays and still get a chrony reading.

Well, maybe I'm not remembering this correctly (I don't have my manuals handy), but Richard Lee says don't go below 10% less than the published starting load. I thought that was because of the un-reproduced but widely believed to be possible kaboom on super light loads. That's why I'm nervous about just reducing the charge with a powder like Clay's. Am I remembering wrong or misunderstanding that?

That's why Trail Boss has so much appeal. According to Hodgdon documentation (http://hodgdon.com/PDF/Trail%20Boss%20Reduced%20Loads%20R&P.pdf), even if there's not published load data, for any rifle or pistol round you can safely make your own Trail Boss recipe by measuring the usable case capacity. My thinking was, reducing case capacity should reduce, if not eliminate the ultra-light kb possibility, and if Hodgdon is correct, our new "eargensaven mauseflatulenz" should be safe with 70-100% of the case capacity filled with Trail Boss. If that's really true for a shortened case, the only other danger is loads so light they dont't push the bullet all the way out of the barrel. And as I and others have pointed out, that's an easily manageable risk.

That's the logic I was hoping to get some feedback on. My son and I have discussed the "how low can you go" and still exit the barrel project, but I didn't think it was safe to just reduce the powder charge very far below published minimum loads without reducing the case capacity.

manithree
December 5, 2012, 01:10 AM
do you think such a project will be welcomed?

I don't know how to say this any more clearly. I have open carried to my kids schools. In Utah, public schools are legally prohibited from regulating carry by employees or others. This is a free state. We've done one shooting and one re-loading/shooting projects already, and the second one was especially well-received.

Even if we did live in a more hopolophobic area, I still wouldn't care. As long as he does some math and science, learns something, and has fun (safely), we would do it anyway.

Andrew Leigh
December 5, 2012, 06:39 AM
I don't know how to say this any more clearly. I have open carried to my kids schools. In Utah, public schools are legally prohibited from regulating carry by employees or others. This is a free state. We've done one shooting and one re-loading/shooting projects already, and the second one was especially well-received.

Even if we did live in a more hopolophobic area, I still wouldn't care. As long as he does some math and science, learns something, and has fun (safely), we would do it anyway.
Hey Manithree, I was not being critical of your project choice I was simply concerned.

bear in mind I am from a different continent and the press we get here is probably a little unbalanced. Also I am not aware of the differening laws in different states.

jmorris
December 5, 2012, 09:35 AM
just a thought, with all of the negative issues being experienced in schools with firearm related incidents do you think such a project will be welcomed? Your son could be marked down as a result or the project may well not be accepted. Also how does he demonstrate the results of the project?

Guess its been 10 years or so ago I helped my brother in law with a science project. He really just wanted to build a gun. I understand that feeling and realized I could, without him being aware of it, have him gain more knowledge about many things.

Started out by having him watch me machine all the parts required out of plastic, then he reproduced them in 4140 and 4130. Once we had a little fun playing with it, we chronographed results with different pressures up to 2800 psi.

With that data he was able to calculate energy and trajectory tables and make his display and had the plastic mockup to take to school. Paint ball was big with the boys in his school and he was quite proud to have built one that had more energy at 100 yards than his buddy's made at the muzzle and he learned more than I had ever expected. After it was all said and done, I could have cared less what the teacher thought.

kingmt
December 5, 2012, 10:15 AM
Less powder willl not cause a kaboom by itself. Two bullets in the barrel could but you already said you was going to check that.

Your test results would really be easier seen with a heavier gun & longer barrel.

manithree
December 5, 2012, 12:09 PM
Less powder willl not cause a kaboom by itself.

There are those who disagree with that statement:
http://guns.connect.fi/gow/QA1.html
http://www.reloadammo.com/liteload.htm
http://www.thehighroad.org/archive/index.php/t-399439.html
http://africanxmag.com/secondary_explosion_effect.htm

But since there is no consensus on the cause, asking how to avoid it (which is only one of my questions), isn't very useful. But excess case capacity seems to be the common denominator, so that's why our plan would likely involve reducing case capacity.

rsrocket1
December 5, 2012, 12:34 PM
I think you are in much greater danger of cutting down the volume of a .38 case and trying reduced loads than you are of experiencing a S.E.E with a low charge of ultra fast powder.

When you reduce the volume, the pressures go up much faster as the seating depth increases to the point of a tenth inch difference could mean the difference between a squib and a kaboom.

I regularly shoot 10-11 grains of Unique/Bullseye in .308 cases with 110g plated RN bullets and that charge is below 50% volume (about 32% after seating the bullet). "The Load" is a long used charge of 11g Red Dot in anything from 30-30 to 30-06. S.E.E.'s tend to happen with reduced loads of slow burning rifle powders and my personal guess is that the primer launches the bullet into the rifling, the powder ignites much later, then it is an overpressure burn and not a detonation.

But again, it's your gun, your son and you are responsible for his safety in this science fair experiment. I would not so much endorse the alternative as to discourage cutting down a .38 case to reduce the volume.

For a really safe(er) experiment, "cast" up some .357 bullets out of glue sticks and shoot them with primers only. You can determine muzzle velocity based on seating depth (hint: seating the bullet against the bottom of the case is the best).

http://i270.photobucket.com/albums/jj96/rsrocket1/100_5942.jpg

manithree
December 5, 2012, 01:31 PM
Since that's two votes for the reduced case capacity actually increasing the danger, we probably won't do that.

kingmt
December 5, 2012, 06:07 PM
That is the point of reducing the case capacity is to get the pressure to spike faster. That is how you get by with less powder. Your reduced recoil will come from two things. First is easy to see. Less powder less gasses. Second is the lower volume gives you a quicker spike in pressure so the pressure is tapering of by the time the bullet leaves the barrel. That is why I suggested a longer barrel.

I don't know much about TB but see that it acts like Black. Black would be safe to do this so I figured TB would be also.

I wouldn't cut the case tho just shove it in deeper.

manithree
December 5, 2012, 07:08 PM
Second is the lower volume gives you a quicker spike in pressure so the pressure is tapering of by the time the bullet leaves the barrel.
Which is great for actually reducing perceived recoil. But I can't measure that, so it really doesn't help for a science project.
That is why I suggested a longer barrel.
As much as I would like to use this as an excuse to buy a GP100, that's not likely to pass the finance committee, especially since the gun is a control, so it doesn't help the science project, either.

splattergun
December 5, 2012, 07:42 PM
Go for it manithree. We still had a shooting range in the basement of my high school a long time ago. Then they downgraded to a 'safer' archery range. Now it's just used for ROTC drill and broken desks.
Let me suggest that your son doesn't have to measure recoil with a lighter projectile, it can be calculated. Very scientific.

manithree
December 5, 2012, 08:47 PM
Let me suggest that your son doesn't have to measure recoil with a lighter projectile, it can be calculated. Very scientific.

That's what we're doing (this year, too, actually). Just calculating F.R.E.

I wish I had a track on bearings so that I could securely attach a pistol to, then remotely pull the trigger (without moving the pistol) and measure the backward velocity over time with high resolution. Alas, I don't have the electronics or mechanical chops for that. We wanted another rig to measure muzzle flip, but that's even harder.

Centaur 1
December 5, 2012, 10:35 PM
Revolvers are tricky when you reduce the load too far. You can't reduce the load as far down as you can with a non-revolver. When the bullet sticks in the barrel you can hear the gas escape through thee cylinder gap. I also started worrying about lodging a bullet that's partly in the barrel and partly in the cylinder, locking up the gun. Lighter bullets are the way to go when reducing recoil. I use the Lee 105 grain swc loaded with Trail Boss and the recoil is way down.

kingmt
December 6, 2012, 06:38 AM
It isn't perceived it is real. It would be easy to build a rig to measure actual recoil & I'm one of the few trying to keep you with this but it doesn't sound like you want my help so good luck with the project.

manithree
December 6, 2012, 08:38 AM
I'm one of the few trying to keep you with this but it doesn't sound like you want my help

Sorry, I guess I wasn't clear enough in post #25. The consensus seems to be that reducing cartridge capacity to achieve lower velocity increases the risk of unsafe pressure. I'm not going to do that. So this particular project is on ice.

If you have ideas for a rig that will measure recoil, I would love to hear that. My son and I have batted that around for months and the only thing we have come up with is measuring velocity to calculate FRE.

jmorris
December 6, 2012, 09:23 AM
As much as I would like to use this as an excuse to buy a GP100, that's not likely to pass the finance committee, especially since the gun is a control, so it doesn't help the science project, either.

I get it now and have a solution for you. What you need is a 357 ruger blackhawk, with the 9mm conversion cylinder. That will give you 38spl and "reduced capacity" pre shortened cases in the form of 9mm brass. The last one I picked up cost $325 and the fellow had never even used the 9mm cylinder.

You need not worry about unsafe pressure spikes either as there is tons of load data for 9mm. If you can't find one or just don't want to spen the money, weigh the water volume of a 9mm case and trim down 357 brass to achieve the same volume. This will require to seat bullets at depth without a primer in place, and fill with a syringe and weigh inverted. I would pick 357 brass and only use a 357 for tests as unlike 38spl it runs higher pressures than 9mm.

kingmt
December 6, 2012, 10:58 AM
I agree a 357 would give you more insurance.

A powder like bulleye a 10th of the volume would be big difference while TB would be had to tell a difference. I wouldn't let the nay say people on here scare me but research it harder & find out the truth. Other ways could be used to reduce case volume then cutting the case. you could use filler like corn mill. That way you may be able to look at a different gun even bottle neck. Then take what you learn & related it to the smaller gun to see if you can repeat it.

To measure recoil I'd put the handgun in a vise build your rig so that you can place a heavy spring 90^ from the back of the grip. Make sure the finish is protected. I'd use cheap caliper with the depth gauge inside the spring to measure how much the spring gets compressed. You could just get a $2 depth gauge then measure it with the caliper because the is a good chance that the recoil would destroy the caliper.

rsrocket1
December 6, 2012, 11:34 AM
The problem with measuring actual recoil means making something like a ballistic pendulum with a means to remotely pull the trigger without influencing the motion of the gun. Putting human hands in the test will throw and unknown variable into the mix.

That means something like a pair of plates or blocks to hold the gun which can screw together and allow the gun to move about so the recoil axis will be tangential to the arc of the swing. It can also be done with pressure transducers between the gun and blocks and a computer to log the data.

As a college experiment, it looks like something fun, but for a 6th grader, it reeks of too much parent involvement. :barf:

jmorris
December 6, 2012, 12:19 PM
Lots of ways to pull a trigger remotely. The syringe style "master/slave" cylinder style are really cheap and super simple.

helotaxi
December 7, 2012, 10:02 AM
There are those who disagree with that statement:
http://guns.connect.fi/gow/QA1.html
http://www.reloadammo.com/liteload.htm
http://www.thehighroad.org/archive/index.php/t-399439.html
http://africanxmag.com/secondary_explosion_effect.htm

But since there is no consensus on the cause, asking how to avoid it (which is only one of my questions), isn't very useful. But excess case capacity seems to be the common denominator, so that's why our plan would likely involve reducing case capacity.
If you look at all those, SEE (if it exists) relies on a very slow powder and a low charge density. Bullseye, Clays, Trailboss and powders like them burn so quickly that reducing the charge significantly only runs the risk of sticking a bullet. CAS shooters use extremely light loads of these powders with soft cast bullets to produce pop-gun loads in the 400fps range safely using .38spl or .357 brass. If you work down to ensure that the bullet leaves the bore, you are perfectly safe. Same concept as creating subsonic loads for rifles. Use the right powder that can be safely downloaded and work down to the results you're looking for.

Edarnold
December 7, 2012, 04:09 PM
Hmmm... Your aim is to reduce case capacity so as to ensure consistent combustion of a very light powder charge. The Old School answer to that was to to keep the case capacity the same, but fill the empty space with something that would hold the powder in place against the primer. The traditional filler was kapok fiber (used to be popular for cushion stuffing), an appropriate pinch of fiber pushed down on top of the powder to hold it in place. For your purpose the best powder should be Bullseye, ignites and burns better at low pressures than about anything else.

IMHO

SSN Vet
December 8, 2012, 09:50 AM
fill the empty space with something that would hold the powder in place against the primer. The traditional filler was kapok fiber

Over on the Cast Boolits forum, there's been discussion from time to time about using case fillers as a replacement for gas checks.

IIRC (which is a big if) oatmeal is a preferred filler mat'l.

Not sure if it's instant or old fashioned Quaker Oats though :)

manithree
December 8, 2012, 10:18 AM
but for a 6th grader, it reeks of too much parent involvement.

Even for a 7th grader, I agree. And some of them get expensive in a hurry. Add to that the fact that the building of the rig doesn't interest my son nearly as much as the re-loading and shooting, plus we're worried the FRE we were hoping to generate wouldn't even move a rig we could build, and I've got a really hard sell on my hands. We've discussed this before, and I brought it up again after these suggestions. I can see him glazing over with disinterest. Too bad these are so expensive (http://www.shootingsoftware.com/recoil.htm)and not available any more.

I hadn't thought of the transducers. That one was the one that he seemed most interested in. Anybody know where to get decent, fairly inexpensive transducers that would do this and work with Linux?

jmorris
December 8, 2012, 10:47 AM
I can see him glazing over with disinterest.

If the kid isn't fired up about it, it's going to be your project.

For light loads out of a revolver it would be pretty simple to make a simple sled that you could measure rearward travel. You would obviously have to come up with your own units of measure but could see relative differences.

manithree
December 8, 2012, 11:38 AM
If the kid isn't fired up about it, it's going to be your project.

He's intensely interested in the wildcatting/reloading/shooting part. It's the construction that loses his interest.

jmorris
December 8, 2012, 04:59 PM
Too bad, that is the fun part.

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