I’ve been doing intermediate barrier penetration “testing” off and on for over 25 years now. Started in the Corps and LE, then continued it with my students in courses such as Guerrilla Sniper. The great thing about getting my students involved is that it lets me greatly increase the calibers and types of ammunition tested.
An intermediate barrier (IB) is something that you shoot through to hit something on the other side.
I’ve shot a wide selection of automotive windshields, single and double pane residential and commercial glass, doors from commercial earth moving equipment, various thicknesses and ratings of “bulletproof” Lexan, and wire impregnated safety glass (often seen in classroom doors).
The two main issues we are looking at are:
1. The amount of deviation from POA to POI
2. What shape is the bullet in when it impacts the target
Several solid takeaways. Some of these should be fairly obvious, even to the layman, but I’ll include them so that I’m not called to task for NOT including them.
1. The closer to the IB that the target is, the better. This will lessen the amount of deviation. The flip side of that is, depending upon the construction of the IB, the closer the target is, the more issues you will have with spalling. Spalling is secondary fragments broken off the IB by the impact and penetration of the bullet. These fragments will tend to travel perpendicular to the surface of the IB, and not necessarily follow the path of the bullet.
If you are an LE Sniper making a hostage rescue shot, or there is an innocent/non-target in close proximity to the target, you will need to account for spalling. If you make a successful hit on the target, but permanently blind the hostage, that’s a strike against you. Spalling can cause permanent debilitating injuries, or even death.
2. Weight trumps speed. .308’s show less deviation from POA than 6.5 Creedmoor. 6.5 Creedmoor shows less deviation than 6.5 Grendel. 6.5 Grendel shows less deviation than 5.56, etc.
Even amongst a specific caliber, weight will make a difference, even with the loss of velocity. For instance, amongst the Federal Gold Medal Match .308 family, the 168grn SMK @ approximately 2650fps will show more deviation than the 175grn SMK @ approximately 2600fps, and the new 185grn Berger Juggernaut @ approximately 2600fps is markedly better than the 175grn load.
It’s my opinion that 6.5 Creedmoor is not the optimal choice for LE Sniping, due to the increased amount of deviation from POA to POI when encountering IB’s, which is common in that environment. It’s not the worst option an agency could choose, but .308 is a better performer in IB scenarios.
Through an automotive windshield to the headrest, even the 168grn .308 loads will stay within the cranial vault. The 140-147grn 6.5 Creedmoor loads will not reliably do so.
Keeping the bullet the same weight, and increasing velocity, will also lessen the amount of deviation. I plan on doing a test with .308 185grn Berger Juggernaut handloads, running them out of a .300Blk, .308, .30-06, and .300WinMag. I’m very curious how much the difference in MV’s will effect the POI shift.
3. Bullet weight is only important if it’s got enough velocity to back it up. The worst round that I’ve tested so far was a .300Blk 220grn SMK at approximately 980fps. The heaviest bullet in my .30 caliber loads, but the slowest by far. Even 55grn 5.56 outperforms it when it comes to deviation.
4. In windshield testing, when fired straight on, bullets will tend to try and follow a path that is more perpendicular to the surface of the windshield, i.e., they will strike low. This is not always true, and it’s not repeatable enough to be trustworthy. What I mean is that it can’t be reliably accounted for like one can account for the POI shift when shooting with and without a good suppressor.
5. Within reason, bullet design is not as important as the weight of the bullet. Most of my Guerrilla Sniper students run carbines and rifles in 5.56, with bullet weights ranging from 55grns to 77grns. In regards to the amount of deviation after penetrating the IB, a 55grn M193 and a 55grn Hornady TAP Barrier Penetrator show approximately the same amount of deviation. So, what’s the difference in the two bullets? The Barrier Penetrator round is of a more rugged design and will stay together better, which aids greatly in terminal ballistics.
I’m trying to find out at what point does weight trump velocity, or vice versa. I will be running some very heavy, but slow, rounds like 240grn and 300grn Gold Dots out of a .444 Marlin.
An intermediate barrier (IB) is something that you shoot through to hit something on the other side.
I’ve shot a wide selection of automotive windshields, single and double pane residential and commercial glass, doors from commercial earth moving equipment, various thicknesses and ratings of “bulletproof” Lexan, and wire impregnated safety glass (often seen in classroom doors).
The two main issues we are looking at are:
1. The amount of deviation from POA to POI
2. What shape is the bullet in when it impacts the target
Several solid takeaways. Some of these should be fairly obvious, even to the layman, but I’ll include them so that I’m not called to task for NOT including them.
1. The closer to the IB that the target is, the better. This will lessen the amount of deviation. The flip side of that is, depending upon the construction of the IB, the closer the target is, the more issues you will have with spalling. Spalling is secondary fragments broken off the IB by the impact and penetration of the bullet. These fragments will tend to travel perpendicular to the surface of the IB, and not necessarily follow the path of the bullet.
If you are an LE Sniper making a hostage rescue shot, or there is an innocent/non-target in close proximity to the target, you will need to account for spalling. If you make a successful hit on the target, but permanently blind the hostage, that’s a strike against you. Spalling can cause permanent debilitating injuries, or even death.
2. Weight trumps speed. .308’s show less deviation from POA than 6.5 Creedmoor. 6.5 Creedmoor shows less deviation than 6.5 Grendel. 6.5 Grendel shows less deviation than 5.56, etc.
Even amongst a specific caliber, weight will make a difference, even with the loss of velocity. For instance, amongst the Federal Gold Medal Match .308 family, the 168grn SMK @ approximately 2650fps will show more deviation than the 175grn SMK @ approximately 2600fps, and the new 185grn Berger Juggernaut @ approximately 2600fps is markedly better than the 175grn load.
It’s my opinion that 6.5 Creedmoor is not the optimal choice for LE Sniping, due to the increased amount of deviation from POA to POI when encountering IB’s, which is common in that environment. It’s not the worst option an agency could choose, but .308 is a better performer in IB scenarios.
Through an automotive windshield to the headrest, even the 168grn .308 loads will stay within the cranial vault. The 140-147grn 6.5 Creedmoor loads will not reliably do so.
Keeping the bullet the same weight, and increasing velocity, will also lessen the amount of deviation. I plan on doing a test with .308 185grn Berger Juggernaut handloads, running them out of a .300Blk, .308, .30-06, and .300WinMag. I’m very curious how much the difference in MV’s will effect the POI shift.
3. Bullet weight is only important if it’s got enough velocity to back it up. The worst round that I’ve tested so far was a .300Blk 220grn SMK at approximately 980fps. The heaviest bullet in my .30 caliber loads, but the slowest by far. Even 55grn 5.56 outperforms it when it comes to deviation.
4. In windshield testing, when fired straight on, bullets will tend to try and follow a path that is more perpendicular to the surface of the windshield, i.e., they will strike low. This is not always true, and it’s not repeatable enough to be trustworthy. What I mean is that it can’t be reliably accounted for like one can account for the POI shift when shooting with and without a good suppressor.
5. Within reason, bullet design is not as important as the weight of the bullet. Most of my Guerrilla Sniper students run carbines and rifles in 5.56, with bullet weights ranging from 55grns to 77grns. In regards to the amount of deviation after penetrating the IB, a 55grn M193 and a 55grn Hornady TAP Barrier Penetrator show approximately the same amount of deviation. So, what’s the difference in the two bullets? The Barrier Penetrator round is of a more rugged design and will stay together better, which aids greatly in terminal ballistics.
I’m trying to find out at what point does weight trump velocity, or vice versa. I will be running some very heavy, but slow, rounds like 240grn and 300grn Gold Dots out of a .444 Marlin.
