Rifle Scopes Scar 17 SBR Scope thoughts?

[koshkin]

I highly recommend this layman primer (below) on sectional density (SD) and it's effects on overall performance of a projectile i.e. BC and penetration. The article gets very interesting near the end. Though this is "penetrating" the subject matter of terminal ballistics....ok bad joke! this subject is worthy of it's own thread in the ballistics section.

http://abesguncave.com/sectional-density-all-important-and-almost-ignored/

That type of a position is something I am familiar with, but the question that is not clear to me is whether penetrating body armor, be it kevlar or plates is a fundamentally different process than going through typical barriers like walls and car doors (and soft tissue).

A sort of an anecdotal piece of information I have some personal familiarity with is that the slow moving 7.62x39 goes through walls and other natural barriers a fair bit better than much faster moving 5.56x45. Sectional density of the much slower moving 7.62mm 123gr bullet is roughly equivalent to that of a 65gr 5.56 bullet.

However, in that case, with comparatively simple bullet construction, there may be an effect from a faster moving bullet deforming faster which impedes barrier penetration. Alternatively (or additionally) momentum may be a significant factor since 7.62x39, depending on specific ammo, does have abut 40-50% higher momentum.

As I said, it is not my field, so I'll ask some questions and do some digging. I do work largely with the DOD and prime contractors, so there enough people I can ask.

ILya

 

[koshkin]

Are you just trying to be argumentative for the sake of it? There is zero logic in what you are saying.

1300ftlbs / 5.56MM = 233 units of energy per surface area

2500ftlbs/ 7.62mm = 328 units of energy per surface area.

Both bullets have relativity similar construction. FMJ Copper jacked lead core. Now explain to me why the 5.56 , having less energy per surface area still outperforms the 7.62 against armor?

Let me give you a hint since you didn't hear it the first two times. Speed Kills. Why do you think Steel targets have speed/distance recommendations so you don't kill the steel? 7.62 @ 2700 fps will barley make a scratch. 5.56 @ 3200 fps will deform the shit out of it.

I know you think your the smartest dude in here. Being an optics engineer or whatever the fuck you are, and your getting schooled by a dude with an accounting & finance degree and a few tours in hajistan.

I'll leave the juvenile name calling to you, since you seem to revel in it. It is too bad your accounting and finance degree did not cover basic civility.

Your blanket assertion that speed kills is simplistic in a sloganeering sort of way, so I'll ignore that too.

That having been said, let's stick to the same caliber to make the discussion a little more intellectually honest.

With 5.56x45, with the same bullet construction, which will offer better body armor penetration. 55gr bullet going fast or 77gr bullet going a little slower?

To be clear, I have not done this test, so I am very curious. I am sure someone has.

ILya

 

[Primus]

For a 4th time for the hard headed.

Compare m193 with mk262 and show your work.

Which one do you think will punch armor easier?

Civility is you thinking your a master of everything when you are not. Your not the smartest guy in the room and based on This conversation, definitely not the smartest guy in this thread. So feel free to go do some actual research instead of trying to argue with me. It's all open source. You say your not arguing and you don't know, but you want to challenge everything.
If u don't know it's better to learn before speaking. Atleast that is what a humble person would do.

 

[koshkin]

For a 4th time for the hard headed.

Compare m193 with mk262 and show your work.

Which one do you think will punch armor easier?

Civility is you thinking your a master of everything when you are not. Your not the smartest guy in the room and based on This conversation, definitely not the smartest guy in this thread. So feel free to go do some actual research instead of trying to argue with me. It's all open source. You say your not arguing and you don't know, but you want to challenge everything.
If u don't know it's better to learn before speaking. At least that is what a humble person would do.

I specifically said I do not know, so I asked a question. Asking a question is the exact thing people do when they want to learn something.

If you are not aware of a specific comparison I am asking about, I will go and research if someone has done it. I am sure someone has. As far as your whole smart/humble/etc stuff goes, try looking in the mirror first. If you can't handle a very mild argument without resorting to juvenile name calling, you have some soul searching to do.

ILya

 

[koshkin]

Primus,

You were right that there is plenty of data available. There is a lot more to look through, but this quick and dirty test from Ft Benning suggests that Mk262 does a little better than M193:
https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2006/smallarms/gandy.pdf

They do not go into the "why" of it, so I'll need to do more research.

ILya

 

[Primus]

This is where you get to go back and learn about the difference between intermediate Barriers and body armor. Enjoy.....

 

[Sako man]

Ilya, interesting study! In reading the analysis from the military it appears from the preliminary data that M193 is a poor or only partial penetrator of hardened surface. Motion vectors, barrier angles, and materials do make a difference obviously. Vs. the 7.62 which is stated to have caused "more damage." The experiment however does not seem to delve into 7.62 as much as 5.56. I would like to know what "more damage" means. But one could assume it means along with other things greater barrier and armor penetration.

As well if those who want a summation of the article I posed here is a quote form the author which pertains to this lovely thread:

" For tactical shooters: Sectional density means greater ability to shoot through cover and greater likelihood of penetrating body armor."

7.62 generally has a greater SD (sectional density) than 5.56 normally. So, in drawing a quick conclusion from the primer on SD and the study done by the military it would seem that the 7.62 M80 would be a better penetrator than 5.56 M193.

Now that said, I am sure someone saw M193 penetrate more metal plate then M80, and such observations would be "anecdotal."

 

[JWG]

Primus,

You were right that there is plenty of data available. There is a lot more to look through, but this quick and dirty test from Ft Benning suggests that Mk262 does a little better than M193:
https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2006/smallarms/gandy.pdf

They do not go into the "why" of it, so I'll need to do more research.

ILya

It is my experience that, excluding M855/M995/M855A1's core material, the faster bullet will penetrate a homogeneous hard barrier more effectively than a slower bullet. When you add complexity (car doors, etc.) that may not always be the case.