Some thoughts about snail bullet traps

[Prospector]

I'm interested in making a snail bullet trap to recover some of the lead I'm sending downrange. I've looked at several designs and often wondered whether a round will find its way back out of the horn and back to the shooter. To that end I've made a few full-size and scaled drawings with the bullet entering the horn at the extreme left or right side of the opening. This will ensure the maximum ricochets inside the horn.
So far I've determined that a bullet will not make it to the narrow end without returning back out of the trap. Obviously there are snail bullet traps that work so I'm trying to find out what happens inside the horn. I made a fair assumption that the angle of incidence equals the angle of reflection, and plotted the angles using a compass, protractor, and even a laser light aimed at a mirror parallel to the horn wall. Generally, at a point about 4-6 inches from the small end the bullet angles of incidence and reflection are equal and begin to reflect back out of the horn. My theory is that this procedure is correct for a hard ball, like a ball bearing, that does not distort or disintegrate, but may not hold true for a soft lead bullet.
My last drawing was a horn 15" wide by 32" long (along the centerline) with an 1 1/2" opening. As stated the bullet began to return at about 5" from the small end. At a point before the bullet would begin to return I modified the cone shaped horn into a square tube about 4" square. This allowed the bullet to travel bit further and change the angle of reflection so that it did end up in a snail cylinder. Increasing the small opening from 1 1/2" in the cone configuration, to 4" in the square tube configuration opened up a new problem in that a direct shot down the middle would strike the snail cylinder with full impact. I thought about hanging a heavy plate behind the opening so that the sidewall of the snail would not have to take the full impact.
I have two pieces of 3/8" x 12" x 24" plate steel that will weld up to make the top and bottom plates. I'd like to use at least 1/4" plate for the parallel sides, but I only have some 11 gauge. I'd actually prefer to make the horn tapered on all four sides to minimize the small end opening. Feedback and suggestions are welcome. Thank you.

[2wheelDuke]

Some guys fabricated one at my club. As you said, the funnel intersects the drum on the edge, tangential to the drum on the top edge you could say. I don't see how a round could get out.

I could provide some pictures and measurements if you remind me. The only real downside I see is that the "horn" might be to steep and the drum too small. I've heard commercial snail traps leave the bullets basically intact. My club's smashes them flat.

[Prospector]

I don't believe a bullet will come out once it's in the snail trap, but from my drawings, once the bullet gets down to the narrow end it begins to bounce around and come back out. I'm treating the bullet like a billiard ball that banks off the side cushion at the same angle it strikes it (angle of reflection = angle of incidence). If the bullet, on the other hand, strikes the angled side of the bullet trap and then slides into the snail opening instead of ricocheting back and forth we're dealing with an abberation of the law of physics. This may well be what is actually happening.

[Mica_Hiebert]

Billiard balls bounce off a flat surface, if a pool tables sides where curved your deflection angles would change... but then I'm talking out my **** cuz I suck at pool! Nor am I an engineer or good with physics... I'm very familiar with newton's law...

[IllinoisCoyoteHunter]

https://www.youtube.com/watch?v=PLyi...&feature=g-upl

[jmorris]

I always liked this one.

[WilliamDahl]

I brought this up in a topic back in 2012.

http://castboolits.gunloads.com/show...=1#post1850706

Mythbusters did this and it showed the change in angle:
https://www.youtube.com/watch?v=6ujDksc1ZOc

Unfortunately, they cut it off after the first test, but you can see that the angle changes.

[country gent]

I made a snail trap for in the garage years ago for 22 offhand practice. I have shot into it with bigger firearms also. Its a simple funnel into a piece of sch 80 10" pipe. Cut the opening and welded on the bottom plate of the funnel set the opening at just over 1/2" and welded the top plate in. side plates. Bullets tend to enter the pipe ( Snail drum) smoothly and spin until energy is expended. When fired into you dont hear dings or bouncing but a zing as the bullet spins around. Once energy is expended any bigger chunks tend to roll back out the front. No real energy top them just gravity. Another thing to consider is to copver outside with carpet or other noise deading material.

[nagantguy]

I always liked this one.

I have one almost exactly like this, only no longer mounted on a axel. It says on the side FT. Knox training battalion. Rated for up to browning automatic rifle, .30 cal.

[Prospector]

Thanks for that info William, it looks like we're barking up the same tree. I'm leaning toward the bullet sliding towards the narrow end of the trap and not following the equal angle law of physics. I'm relatively new to posting on this site and tried a search for other snail trap threads, but this site doesn't seem to have a search engine for CastBoolits threads. I entered my search data into the Google search bar and found some very old articles from the CastBoolits forum dating back to 2007. I thought it was a bit late to respond to those so I opened a new thread. Is there a better way to search?

[jmorris]

It is not uncommon in some shooting sports to use plastic barrels as vision barriers and hide targets behind them.

I will never forget the day, about 10 years ago, when my friend Lou hit the barrel in front of a target. The bullet went into the barrel but didn't exit, took everyone around 5 seconds after he finished the stage to figure out where the odd sound was coming from as the bullet was still spinning around in the barrel but slowing and changing the pitch of the sound.

Never liked seeing them used in that manner after that and I always took note of where they had been hit before and where those holes were facing.

[Plate plinker]

MORRIS, I have witnessed that phenomenon too. However the times I have seen a bullet in the barrel it was moving slowly when we noticed it was in the barrel. Maybe our stage was longer? Maybe those barrel barricades should have some cardboard in them to slow the slugs down.

[Mytmousemalibu]

I saw & heard one enter a plastic 55gal drum this weekend at my USPSA shoot! Pretty crazy, i wouldn't have believed it had i not been there!

[jmorris]

Still makes me shiver thinking of the bullet just making a U turn in one and coming out of a previous hole... Might be a few million to one chance but the only time I have "luck" is when it's bad.

[IllinoisCoyoteHunter]

When the bullets hit the sides of the trap they do fragment and they do find their way to the back of the trap. Does 100% make it to the back of the trap.....no. I have noticed with mine that there are some small fragments normally setting on the base of the trap. The trap I made has stopped 3006, 308, and 223 plus all pistol up to 500 SW. It is all about having a good angle. If it is too steep of an angle you will get more splatter that doesn't make it to the back of the trap.

The pipe on the back of the trap works too. You can clearly see where the lead fragments swirl around inside it.

[MarkP]

When the bullets hit the sides of the trap they do fragment and they do find their way to the back of the trap. Does 100% make it to the back of the trap.....no. I have noticed with mine that there are some small fragments normally setting on the base of the trap. The trap I made has stopped 3006, 308, and 223 plus all pistol up to 500 SW. It is all about having a good angle. If it is too steep of an angle you will get more splatter that doesn't make it to the back of the trap.

The pipe on the back of the trap works too. You can clearly see where the lead fragments swirl around inside it.

Do you happen to know the approximate diameter of the trap tube and wall thickness? I am planning to make a trap at 16" dia from 3/4" thick A-572 plate. That is about the minimum diameter I can make on the particular brake I will use to form the part.

[Ballistics in Scotland]

Lead, especially when unjacketed, has low elasticity. Some of the bounce comes from the elasticity of the steel. It can be reduced by using thicker steel (which can be costly and inconvenient) or by covering it with sand, gravel or concrete. Similarly if it is of the right shape to make the bullet strike bullet debris at the bottom (or sand to get it started), there should be little tendency to ricochet.

The angle of reflection equaling the angle of incidence is about right. But it is the angle from a line at right angles to the surface that applies, and a soft bullet won't bounce from a single point, like a ray light. It will deform, slide and bounce from a point slightly further along the curve or incline. The ideal, though it would be quite large, is a snail curve so calculated the bullet would simple slide around the bend until it comes to the debris bed. It takes an energy input to make a body keep changing direction, and that is an energy output from the bullet.

[Ballistics in Scotland]

It is not uncommon in some shooting sports to use plastic barrels as vision barriers and hide targets behind them.

I will never forget the day, about 10 years ago, when my friend Lou hit the barrel in front of a target. The bullet went into the barrel but didn't exit, took everyone around 5 seconds after he finished the stage to figure out where the odd sound was coming from as the bullet was still spinning around in the barrel but slowing and changing the pitch of the sound.

Never liked seeing them used in that manner after that and I always took note of where they had been hit before and where those holes were facing.

The more a bullet's direction is changed by a ricochet, and especially by multiple ricochets, the more energy it loses. It is the ricochet fired in a close to dangerous direction that kills people. Some of these rather intimidating effects may involve no more than slingshot velocity. TF Fremantle in 1901 wrote of a bullet fired into a tank of water closed by a thin membrane. It somehow contrived to bounce out, and came to rest nose down on the table and spinning like a child's top. Jeff Cooper described bullets coming to rest in sand, which could be heard spinning with a rather irritated tone after they had come to rest.

I've seen sand striations on a long range recovered bullet which were considerably steeper than the rifling grooves, indicating that they retained their spin better than they retained linear motion, so the rotation per inch travelled became greater. I have also experimented with .22 bullets fired into water. The light and extremely hollow CCI Stinger bullet broke into small pieces which apparently hit nothing solid at six inches. Eley HV hollow points widened and stayed nose on, hitting rock quite lightly at 9in. But Eley solids invariably turned sideways before hitting rock with much the same impact, just a shade more than I got by firing the same bullet from slingshot at 16in.

The point is that the rock marks on the non-slingshotted Eleys indicated that they were still spinning when linear velocity was almost gone. This is mainly of academic interest, but in designing a bullet trap we should remember that bullets might roll themselves sideways as well.

[IllinoisCoyoteHunter]

Wall thickness on my trap and tube were 1/4" IIRC. It doesn't take much, especially when the plate is angles. I will double check on those dimensions.

[MarkP]

Wall thickness on my trap and tube were 1/4" IIRC. It doesn't take much, especially when the plate is angles. I will double check on those dimensions.

Thanks