Boolit "Dwell Time"

[Bad Ass Wallace]

An often misunderstood fact from boolit casters of cast boolits is "dwell time". Dwell time is that fraction of time that a boolit has to transfer 'Kinetic Energy' to the intended target, whether it is shooting steel or game.

Many never think about it but if you have a hard or soft alloy it becomes very important. Shooting steels for example, a hard cast boolit will hit partially deform and then bounce off. The act of deforming is the boolit dwell time and energy is transferred to the plate. A very hard alloy will bounce off and carry a lot of it's energy with it. A softer alloy will deform more and in doing so transfer more energy to the target.

It is the same with game targets, too hard an alloy will punch through with little energy transfer to effect a 'one shot' kill. A softer alloy will deform more and in fact transfer more energy in doing so, making for bigger wound channels. Dwell time is also affected by the velocity of the boolit.

So what ever the intended purpose, boolit alloy hardness is the most critical factor in achieving success. The boolit should be of sufficent hardness to not strip in the rifling BUT also soft enough to impart energy to the target through creating sufficent "dwell time".

https://i.imgur.com/cArT9w1l.jpg

[HWooldridge]

Most of my early 45-70 experience with lead bullets was using a 455 gr FN slug cast from straight linotype. I shot a few deer and a hog - every shot went through, in one side and out the other. All were ultimately fatal, but none were knockdowns. The last deer I shot was a smallish doe - first shot went through her throat but didn’t hit bone or a major blood vessel. She took a few steps and I put the next one through the shoulder - she started hopping but still went several steps before falling. My son and dressed her - there were two clean .45 cal holes.

I went to a much softer alloy in a 300 gr design after that hunt and the next hog I shot dropped with one hit in the shoulder. The bullet stopped under the hide on the far side - perfect mushroom.

[Three44s]

J words would have dwell time as well, some longer and some shorter.

The dwell time I think of is the bullets travel time within a firearm.

I can take two different loads with the same boolit and very similar muzzle velocities but the recoil impulse has a discernable difference. My Smith 629 Mountain Gun responds quite differently as that dwell time changes with the other factors remaining constant.

Three44s

[charlie b]

I thought the title was barrel dwell time.

Terminal ballistics usually refer to penetration and bullet expansion, permanent and temporary wound channels.

And, yes, you need to match your bullet to what you are shooting. I'd not use the same bullet for rabbit or prairie dog that I use for deer or hogs.

[Shopdog]

First thought in my pea brain was the dwell at launch.... and how that is effected by bullet design,fitment,etc.

[Nobade]

Back when I first started shooting silhouette matches it didn't take long to figure this out. The super hard bullets would shatter to dust and leave the targets standing, but softer bullets would hold together just long enough and sort of stick to the target face so they would knock them down. I grew up on the magazines telling me that harder is better and everything needed to be made from linotype. After seeing this for myself I don't think I have made any super hard bullets since.

[country gent]

With the 20-1 what was seen on steel animals was a cloud of dust (paint and lead) and the animal starts to move. As it gains momentum a small disk is seek dropping. this disk is .015 to .020 thick,and is found almost directly under the target. A 550 grn bullet is reduced to this disk.

[huntinlever]

I don't expect expansion with the 405 grain, wide meplat bullet, but I do sometimes wonder if I've gone for too high a BHN. 94-3-3, oven treated and water quenched. Don't have a BHN tester but estimate about 18-20 BHN.

[308w]

Mr. Wallace,
I see what you are saying, but comparing a bullet on steel vs flesh is a apples to oranges type comparison.
This is just my humble opinion, On a steel target, it has been proven that a hard alloy that shatters to dust
has less "push" in it to knock the steel critter down, push may not be a good term here.
That is to say less push than alloy that flattens out against the steel and stays mostly in one piece, this has been proven.
But in shooting flesh and blood, velocity creates expansion.
Harder alloys need more, softer alloys will do it with less but if alloy composition is the same,
expansion increases with velocity. ( my thoughts only)
Hope to hear from some smart folks on this and hear what is their input.
Great post Mr. Wallace.

[TD1886]

there's a video on youtube where these guys attempt to build a fixture to shoot two bullets and impact them together perfectly, and they did it. They had high speed camera's to record this. Many bullets smashed together and just completely exploded, especially the lead bullets and good number of jacketed. One set of jacketed was really surprising. When them met and started expanding one another, they hung their together in mid air and paused, yes this was recorded on the camera. It was as though they stopped and hovered in midair, then the veered off or fell to the ground. The crew was shocked. I was too. That pause or stop was Dwell Time. I'll see if I can find the video.

[gwpercle]

With what and how do you measure "Dwell Time" ?

How long or short does my dwell time need to be for optimum results ?

I don't do you-tube .

Gary

[popper]

A softer alloy will deform more and in doing so transfer more energy to the target.
True but the 'dwell' time at the target is virtually independant of alloy. The same 'energy' is used to expand or shatter the bullet. Depends on the energy in the bullet at impactand toughness of the bullet. Yes, a pass-through doesn't expend all the bullet energy.

[TD1886]

I thought I had posted that video of bullet impacting one another, but I don't see it. Try it again.


https://www.youtube.com/watch?v=tcQVrD7RnNI

[stubshaft]

Dwell time is also predicated on velocity. Back in the 80's when I was hot and heavy into Sillywett competition there were a number of articles by Elgin Gates and IHMSA that experimented with the concept of dwell time. If you drive a too soft bullet, too fast it would "splash" the target and NOT impart enough energy to tip it over. The sweet spot for most cast bullets for me was around 2200 FPS. Slower would be okay but drive it too fast and targets would show damage. I campaigned a 7mm Internationall Rimmed gun with 145 gr RCBS Silhouette bullets that would punch through 3/8" soft steel targets at 150 yards using pure Linotype alloy. Of course in those days I was getting Linotype for ten cents a pound...

[Good Cheer]

Pushing steel is pushing steel and it's completely different from killing animals.

[murf205]

I had the exact experience as Nobade when I shot silhouette matches. I had a bunch of 240 gr Speers and was hitting the plates pretty good but they would wiggle and remain on the stand. After I shot up all the Speers, I cast a load of Lyman 429421's with straight ww and the plates started to peel off the stand with regularity. Dwell time, maybe, or at least that's what I thought. Either way, I started hunting with them as well and they did the trick on every critter I shot since then and that was 50 yrs ago.

[Lloyd Smale]

Pushing steel is pushing steel and it's completely different from killing animals.

very correct . i dont like relying on a bullet to expand without a jacket to control it. to many times penetration testing and actually killing big game with cast has proven that soft cast rifle bullets are more apt to bend or peen, for lack of better words then expand. it can cause erratic performance. ive seen even deer shot with them give poor penetration and even vere off 45 degrees from strait and exit out of the bottom or go into the guts. what works best is a hard cast bullet with a decent size metplat that holds its shape and penetrates straight. you will always get an exit and good blood trail and a long wound channel that gives as much damage as the shorter wider damage a soft bullet does. it also gives you the confidence on that one in a hundred buck that doest give you a perfect shot that you can drive a bullet through at any angle to the vitals and 99 percent of the time even bone wont alter its path. i fooled for a few years with two alloy bullets with soft noses and hp and was never impressed. if dwell time in an animal mattered my 3030 at 2200 would outkill my 7stw 300 ultra and 6.5x300wby and im sorry but that aint happening. the 3030 doest kill as well as a 308 at 200 yards and thats because of velocity. now where dwell time does effect at least a hand gun is in recoil. a 4 5/8s 500 linebaugh is more comfortable to shoot then a 7.5 with the added advantage of different weight bullets and velocity will shoot closer to each other because recoil has less time to act on the bullet because its out of the barrel faster

[Harter66]

The OP has used a common denomination word choice to describe an event . It's like using ftlb of energy as a performance target of a cartridge, it's universal and useful as a goal assignment.

I used to have lots of wood scrap at my disposal so I made some very disposable rocker targets . At the time I was shooting plated SWC , and WQWW 358-158 RF . A guy gave me a box of 75,80,85&90 gr XTP and GD presumably intended for 380 ACP . There's a story that goes with the gun but it's involved. The short version is that the 110 gr max load as a start for them resulted in the best groups that pistol ever shot . All 10-15 of each bullet .
The 158s at 1000 fps will hog right through 3/4 plywood and a 4×4 of Douglas fir with about a dime sized chip attached to a 358 tunnel . The Extreme plated SWC and WQWW Lee RF had equal results.
The XTP and GD however were ripping the blocks off the rockers and failed to exit . Yes it was an HP designed for 650-900 fps and it was probably going upwards of 1250 but there was a huge difference in dwell time and the resulting energy transfer.

In the OPs example the effort is to demonstrate that a softer bullet will stay in/on the target longer and place more of the energy transfer in/on the target. It also reflects how that transfer happens.

From here it's pretty easy to wander off into into shapes and alloy properties.
What we too often lose sight of is that probably billions of game animals have fallen in No America from grey squirrel to the mighty bison and predators including the Yellow Stone grizzly to a soft lead bullet from 50-600 gr from 32-84 cal in common use long before fast and flat shooting 30-30 came along and even Paul Mauser's elephant slayer 7×57 came to be . It certainly wasn't hydrostatic shock that dropped all those bison .

[TD1886]

very correct . i dont like relying on a bullet to expand without a jacket to control it. to many times penetration testing and actually killing big game with cast has proven that soft cast rifle bullets are more apt to bend or peen, for lack of better words then expand. it can cause erratic performance. ive seen even deer shot with them give poor penetration and even vere off 45 degrees from strait and exit out of the bottom or go into the guts. what works best is a hard cast bullet with a decent size metplat that holds its shape and penetrates straight. you will always get an exit and good blood trail and a long wound channel that gives as much damage as the shorter wider damage a soft bullet does. it also gives you the confidence on that one in a hundred buck that doest give you a perfect shot that you can drive a bullet through at any angle to the vitals and 99 percent of the time even bone wont alter its path. i fooled for a few years with two alloy bullets with soft noses and hp and was never impressed. if dwell time in an animal mattered my 3030 at 2200 would outkill my 7stw 300 ultra and 6.5x300wby and im sorry but that aint happening. the 3030 doest kill as well as a 308 at 200 yards and thats because of velocity. now where dwell time does effect at least a hand gun is in recoil. a 4 5/8s 500 linebaugh is more comfortable to shoot then a 7.5 with the added advantage of different weight bullets and velocity will shoot closer to each other because recoil has less time to act on the bullet because its out of the barrel faster

You'll have to admit the 30-30 does pretty well for what it is and in my opinion it's because the jacketed bullet designed for it have thinner jackets becasue of it's lower velocity. It's brought home a hell of a lot of game. So has the 35 Remington.

[HWooldridge]

You'll have to admit the 30-30 does pretty well for what it is and in my opinion it's because the jacketed bullet designed for it have thinner jackets becasue of it's lower velocity. It's brought home a hell of a lot of game. So has the 35 Remington.

Slightly OT, but I wish the old 30-30 Silvertip bullets were still available. They were quite effective on deer sized game.

[Lloyd Smale]

Slightly OT, but I wish the old 30-30 Silvertip bullets were still available. They were quite effective on deer sized game.

my old man swore by them. its the only ammo he ever bought a supply of. he got 10 boxes when he heard it was being discontinued and still had 189 when he died. he was to tight to actually use it for anything other then killing things. honestly i never saw what it did that corelocks didnt do just as well

[HWooldridge]

my old man swore by them. its the only ammo he ever bought a supply of. he got 10 boxes when he heard it was being discontinued and still had 189 when he died. he was to tight to actually use it for anything other then killing things. honestly i never saw what it did that corelocks didnt do just as well

This is not based on scientific testing but I always thought the silvertips expanded more reliably at lower velocities (partly because they would disintegrate at shorter distances). My father also used them - he didn't have ten boxes but that was the only thing he bought. I shot them up years ago after he passed away.