Airgun Slug Expansion for Hunting - Contributing Factors and How to Achieve It

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Ezana4CE

Ezana4CE

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I have begun to read about expansion of airgun slugs and there is a lot of differing information on the forums. The slugs I'm most interested in exploring are various hollow point airgun slugs. My focus is upon the practical application of hunting with hollow point airgun slugs. With that said, I'd like to explore attempting to answer some questions:

1) What is the largest contributing factor to airgun slug expansion?
a) velocity (at the muzzle or upon impact)
b) slug design
c) slug weight
d) lead hardness
e) type of material shot (i.e. bone vs soft tissue)
f) something else (please specify with as much detail as possible)

2) Is there a way to consistently achieve this considering the likelihood that no two hunting scenarios will be exactly the same?

3) Is shooting into ballistic gel the most reasonable method of testing a projectile's expansion?
a) Do these results of shooting into ballistic gel realistically reflect what one can expect afield (bone must be accounted for some type of way)?

I've wondered a few things. I have used hollow point NSA slugs for hunting and I have noticed a thing or two about them. Foremost, I have noticed that I haven't had the opportunity to recover many of these slugs to examine how they expand. In fact, I've only seen how they deform after striking wood or other lead projectiles. I have no idea how they expand or if they are even expanding upon entry and exit of animals. The velocity range that I've shot them has been within the high 700s to the low 1000s fps and not more than 65 yards from muzzle to quarry. The other thing that I have noticed about these slugs is the thickness of the walls of the cavity. The cavity walls on NSA hollow point slugs appear to be thicker than most. The cavity appears to be shallow although I have not been measuring the depth. I have begun to wonder if these are made to expand or simply designed with balance and center of gravity in mind for better BC. Also, I've seen testing in ballistic gel, but most often when shooting animals my projectiles hit bone (e.g. skull, scapulae, ribs, vertebrae, etc). I cant see how shooting into ballistic gel accounts for shooting through bone. Anyhow there is plenty that I haven't read so posting links within this thread is welcomed and I will continue to look into this topic. Thanks in advance to all that make useful contributions here.

I realize that wadcutter/flat meplat projectiles tend to make larger holes upon contact, but that's not what I'm focused upon right now. Nor am I interested in discussing Predator Polymags or Hades pellets in this thread.
 
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Dave, 😊

I love how you worded your title:
•Descriptive
•Clear
•Practical
👍🏼


Just to mention before I answer any specific questions: I'm pretty sure you've read these threads from a couple of years ago, links below.
Particularly, Part (4b) has a collection of hollow point slug expansion tests, in different ballistic media, with photos and the ballistic specs noted.


➧ I'm going to enjoy this thread you started, Dave! 😊

Cheers,

Matthias




🔴 4-Part Series: Ballistics, Expansion Tests, Lethality Mechanics, Hollow Points

🔸 PART (1) Quarry: What kills’em dead – the Mechanics of Killing

💀 Quarry: What kills’em dead – the Mechanics of Killing

💀 Quarry: What kills’em dead – the Mechanics of Killing This thread is PART (1) of a four-part series (cf. below for links to the other threads). 🔴 What kills is a Permanent HOLE in the quarry – nothing else We use projectiles (pellets and slugs) to kill quarry. But what exactly kills...
www.airgunnation.com www.airgunnation.com



🔸 PART (2) How Much Hollow Point Expansion Does How Much More Damage?

🔴 How Much Hollow Point Expansion Does How Much More Damage?

How Much Hollow Point Expansion Does How Much More Damage? The point of a hollow point projectile is to expand and make a bigger HOLE – therefore crushing more tissue in its path. So, how much bigger is the HOLE if I go from .177 cal to .25 cal? Or from .22 cal to .30 cal? See the answers...
www.airgunnation.com www.airgunnation.com



🔸 PART (3) Hollow Point Pellets – Comparison of Specs & Performance

🔴 Hollow Point Pellets – Comparison of Specs & Performance

Hollow Point Pellets – Specs & Performance Chart Hollow point pellets – let’s shorten that to HP (and hope they still will expand on impact 😊). Some.... • Some swear by them. • Some swear at them. • For some they are a great way to sell more pellets. • For some they are a great way to...
www.airgunnation.com www.airgunnation.com



🔸 PART (4) Hollow Points – Testing How Much They Expand and How Far They Penetrate
● (4a) HP Pellet Projectile Expansion and Penetration Tests

🔴Hollow Point Pellets — Testing How Much They Expand and How Far They Penetrate

Hollow Point Pellets — Testing How Much They Expand and How Far They Penetrate This thread is PART (4a) of a four-part series. The other threads explain the mechanics of killing, which projectiles kill better, and which HP pellets are available (detailed specs of .22cal @ US). Links to the...
www.airgunnation.com www.airgunnation.com

● (4b) HP Slug Projectile Expansion and Penetration Tests

🔴 Slugs --- Testing How Much They Expand and How Far They Penetrate

Slugs --- Testing How Much They Expand and How Far They Penetrate Slugs for airguns won’t ever replace pellets. But they aren’t just a fashion, either. Slugs easily cut wind drift by more than half. And at longer ranges they hit quarry with twice the energy. Those are reasons enough that I...
www.airgunnation.com www.airgunnation.com



.
 
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@JungleShooter I do recall reading some of the information in that series. Just about all information concerning hollow-point slug expansion shot from air rifles is welcomed, but I am particularly interested exploring big-bore hollow point expansion. I'm looking at slugs over 100 grains. More so in the mid 100s (130 - 160 grain range), but I'm also curious about the 110 grain slugs that I like in .357 caliber. I'll review information in your links again. I've read much of it before, but I think I will have a better understanding of some of it this time around.
 
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I have been casually reading and learning things here and there on the topic and a couple of things I've read and discussed with others made me think more on the topic. In addition to the point or tip of a soft lead airgun slug being hollowed, I think it's worthwhile to consider the advantages of a hollow ogive as well when considering expansion. With airguns, we are not shooting jacketed projectiles that have a harder material (like copper) encasing the projectile below its point or the angle of the ogive to guide the deformation or expansion of the lead above the jacket. As a result, lead hardness and projectile design appear to be important contributing factors when discussing expansion. I'm still not quite sure where velocity fits into the equation considering all of my airguns shoot slugs at subsonic speeds (with the exception of my Huben. I know it can break the sound barrier with pellets, not sure about airgun slugs). My focus in this area are big bore slugs used for hunting (.30 or better).

I recently discussed various slug designs with a machinist and realized I have a lot to learn. This ought to get interesting since it's captured my attention and I have a little experience to reference. By no means am I attempting to fashion myself an expert on the topic. I created this thread to learn more so if you have the knowledge to correct me where I'm mistaken by all means please do.
 
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the best writeup i ever read on ammo effectiveness was done by the Alphabet org after a botched attempt to stop armored truck theives armed with rifles in south florida and multiple agents were gunned down with their various pistols and ammo being largely ineffective ... one of the blaring findings of the Alphabet org study was that hollow point ammo had next to no reliable effect on that ammos effectiveness at handgun velocities .. effectiveness was narrowed down to 2 factors - penetration and diameter of projectile .. the 10mm was developed in the wake of this study .. later it was watered down to .40 because many complained of 10mm recoil .. .. anyway, i think it carries over to airguns and the velocities we use .. expansion is the least important factor .. most of the 'expando' importance we see with handgun or airgun ammo is pure marketing hype ... according to the Alphabet org study and development team anyway😁
 
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dizzums said:
the best writeup i ever read on ammo effectiveness was done by the Alphabet org after a botched attempt to stop armored truck theives armed with rifles in south florida and multiple agents were gunned down with their various pistols and ammo being largely ineffective ... one of the blaring findings of the Alphabet org study was that hollow point ammo had next to no reliable effect on that ammos effectiveness at handgun velocities .. effectiveness was narrowed down to 2 factors - penetration and diameter of projectile .. the 10mm was developed in the wake of this study .. later it was watered down to .40 because many complained of 10mm recoil .. .. anyway, i think it carries over to airguns and the velocities we use .. expansion is the least important factor .. most of the 'expando' importance we see with handgun or airgun ammo is pure marketing hype ... according to the Alphabet org study and development team anyway😁
Click to expand...


I tend to agree that there is a lot of hype about ammo in airgun land.

However, even if the ABC emphasized the importance of penetration and caliber — there might be a difference between firearms and airguns:


Because these factors in fact DO show up again and again in the the firearms ammo literature. There is much mentioning of stopping power, knock down factor, car door penetration rate, and (I want to call it) kill coefficient: Clearly, for LE and self-defense firearms users and for big game hunters (body shots on deer, pigs, and larger) penetration is really important: Their bullets need to travel far inside big bodies, protected by big bones, before they find vital organs.

➠
However, for small game hunting with modern PCP airguns at typical power levels — penetration is by far not that important.
Most of the time, though, we get our point across — hollow point or dome (frontal shots on trash panda heads being a rare exception).



Great topic. Keep it coming. 😊

Matthias
 
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@dizzums I’ll look for that study. A lot of what I’ve been reading refers to PBs. Lead hardness, bullet design (e.g. full metal jacket, ¾ jacket, soft lead tip, wadcutter, etc), and load type were also discussed in terms of penetration. I’m more interested in these concepts in regards to hunting. More specifically, I’m trying to see if there is a methodical way to avoid pass throughs and to achieve a better blood trail. Conventional airgun wisdom tends to immediately defer to upping the caliber to create a larger hole and using projectiles with flat meplats (wadcutters). That can understand. My focus right now is upon the calibers that I use most and have proven effective. I’m just exploring avenues to better performance or varying performance leading to the same outcome.
 
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dizzums said:
the best writeup i ever read on ammo effectiveness was done by the Alphabet org after a botched attempt to stop armored truck theives armed with rifles in south florida and multiple agents were gunned down with their various pistols and ammo being largely ineffective ... one of the blaring findings of the Alphabet org study was that hollow point ammo had next to no reliable effect on that ammos effectiveness at handgun velocities .. effectiveness was narrowed down to 2 factors - penetration and diameter of projectile .. the 10mm was developed in the wake of this study .. later it was watered down to .40 because many complained of 10mm recoil .. .. anyway, i think it carries over to airguns and the velocities we use .. expansion is the least important factor .. most of the 'expando' importance we see with handgun or airgun ammo is pure marketing hype ... according to the Alphabet org study and development team anyway😁
Click to expand...
Being retired LE and a former Rapid Deployment trainer(think room clearing in a school). I always load my off duty, now retired carry as fmj/hollow point/fmg/the rest hollow points.
 
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We just can’t produce the velocities at distance to ensure expansion with a structurally sound projectile on soft tissue. No matter how big we make the hollow point. Now a Hybrid because it’s a little more flimsy, can get you some expansion at distance if you get them humming. But because of their light weight per caliber, they probably hemorrhage energy compared to a conventional slug. If you are a big bore guy then you are forced to follow an even more anemic set of laws that pistol and muzzleloader guys follow. You must kill with a large wound channel. Created by a large caliber bullet boring a hole and not magically turning into a 50 cent piece. We can kill with devastating cavitation but only if we pick on tiny animals at relatively close distances. No matter how wicked we think our airgun is.
 
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Black powder and handgun velocity is basically the same principle as airgun velocity in my opinion and as stated above. Up to smokeless powder most all bullets were soft lead, large caliber and mostly solid. I find most often heavy for caliber works best for me! Not quite what was specifically asked but I believe the principal is the same. I run a 50 grn. Slug in a .25 Hatsan flash, I cast them from a NoE mold with two sets of hollow point pins. They expand well in things like wood but I only really use the hollow points for squirrels as the cavity in the nose slows them down and helps keep them from carrying to far after exit. For most everything I use solids, I don't have a Chrono but estimate 700/750 fps! It punches though cow rib bones, coconuts and pine boards really well. I cast them from soft lead and cannot tell the difference from recovered slugs after hitting hard objects.
 
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Vetmx said:
We just can’t produce the velocities at distance to ensure expansion with a structurally sound projectile on soft tissue. No matter how big we make the hollow point. Now a Hybrid because it’s a little more flimsy, can get you some expansion at distance if you get them humming. But because of their light weight per caliber, they probably hemorrhage energy compared to a conventional slug. If you are a big bore guy then you are forced to follow an even more anemic set of laws that pistol and muzzleloader guys follow. You must kill with a large wound channel. Created by a large caliber bullet boring a hole and not magically turning into a 50 cent piece. We can kill with devastating cavitation but only if we pick on tiny animals at relatively close distances. No matter how wicked we think our airgun is.
Click to expand...
I agree 100 percent.... I have large 100 percent pure lead .510 470 grain. Large diameter Hollow points at 800 fps they expand perfectly...... But not enough speed and energy for a pass through..... So we really need more fps and foot pounds of energy... I really like to be at 1000 fps and 1000 foot pounds of energy for medium to large game...One day maybe😉
 
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RM.510bigbore said:
I agree 100 percent.... I have large 100 percent pure lead .510 470 grain. Large diameter Hollow points at 800 fps they expand perfectly...... But not enough speed and energy for a pass through..... So we really need more fps and foot pounds of energy... I really like to be at 1000 fps and 1000 foot pounds of energy for medium to large game...One day maybe😉
Click to expand...
.510 and 470 grains? You guys are unique. I don’t want one but would love to witness a big bore PCP being shot. Mucho respect to you guys.
 
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Vetmx said:
.510 and 470 grains? You guys are unique. I don’t want one but would love to witness a big bore PCP being shot. Mucho respect to you guys.
Click to expand...
Just like a big slow pistol or muzzle bomb...it's either zero or hero for hunting..... If you hit vertebrae its lights out.....My first pcp ever is my .510 😉My second will a 22 Condor going in reverse.. I love being able to make my own slugs...Different molds...different.diameter s....also..$0.50 a slug is outta my budget.. Here is some big 474 grain hollow points recovered from game...$1.00 a pound cost....purple powder coat....they perform perfectly..... That said I'd much rather use solids and get a pass through. That being said blood trails are not what you think....sometimes no blood trails at all. Subsonic hunting is different and is a whole new learning curve.

17076262698577302616390404749675.jpg
 
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Yes, this past season my buddy said he would like to see me shoot a deer with a .30 slug out of my P2. I said only if we have snow. I told him I will need to follow tracks all the way to the carcass. To him the words 30 caliber bullet sounded impressive. I informed him the energy even if it was going 1,000fps is a complete joke. I wouldn’t be comfortable unless I moved to true big bore. Then I would focus on penetration, not expansion. Entry and exit wounds are a must when my weapon doesn’t have the oomph to shock something to the ground.
 
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Vetmx said:
Yes, this past season my buddy said he would like to see me shoot a deer with a .30 slug out of my P2. I said only if we have snow. I told him I will need to follow tracks all the way to the carcass. To him the words 30 caliber bullet sounded impressive. I informed him the energy even if it was going 1,000fps is a complete joke. I wouldn’t be comfortable unless I moved to true big bore. Then I would focus on penetration, not expansion. Entry and exit wounds are a must when my weapon doesn’t have the oomph to shock something to the ground.
Click to expand...
@Vetmx You may want to read some of @gendoc’s posts on deer hunting with and Uragan .30. I believe that he shoots them in the neck (vertebrae) and drops them on the spot. That is if a .30 is legal where you wish to hunt.

See post #3 in the thread below.

Has any one take a White Tailed Deer with a. 30 Cal and 44 grain slugs?

I am temped to try it on this hunting season.
www.airgunnation.com www.airgunnation.com

Here’s another thread (post #9) where he discusses it and a laundry list of airguns he used to successfully hunt deer.

Best air gun for hunting?

Sorry I'm really bad at responding. Very busy but what y'all think the best air gun for hunting is?
www.airgunnation.com www.airgunnation.com

My concerns surround the dynamics of what’s occurring with hollow point slugs shot from big-bore air rifles into the animals. We know placement is critical, but I’d like to know exactly what the slugs are doing.
 
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I don’t like having my hands tied with having to take one particular kind of shot while hunting. Especially when I have other options. Much easier to just head to the woods with a .270 or 45/70 and not worry about wounding an animal because it moved slightly as I squeezed the trigger. Needing to hit small kill zones on big game to kill them with inadequate weapons is definitely a challenging way to hunt and I assure you it’s filled with horror stories that you will never hear about. Only the successful hunts make headlines.
 
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If someone can help me better understand what’s written here I would appreciated it. It is obvious that the reference here to bullet hardness correlated to the desire or necessity to increase the bullet’s melting point due to the temperature within the barrel relative to the charge of the cartridge. Aside from that, the premise communicates that pure lead is denser, will vary more energy, and this penatrate deeper if expansion is controlled. This is my understanding.
IMG_4477.jpeg


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Now if I understand this correctly, I have questions on expansion of soft-lead hollow-point slugs. In my limited experience with soft-lead airgun slugs, the penetration is there. It’s the expansion that I’m questioning and curious about because I have not been able to recover a slug that passed through an animal.
 
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