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Posted: 2/12/2008 11:48:44 AM EST
[Last Edit: 2/13/2008 4:30:19 AM EST by Mike_G]
Assuming use of a heavier load e.g. Mk262 or Hornady TAP 5.56 75gr and a 1/7 twist rate how do a 10.5" and a 16" barrel compare in:

*effective range
*terminal ballistics / fragmentation
*How does shooting with a suppressor affect performance +/-
*Reliability

I supect the 16" barrel would be better than the 10.5" in each category, but is the difference significant? At what range would you put down the SBR and pick up a carbine or rifle with 16" + barrel?

Are there any websites that explain the differences?

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Link Posted: 2/12/2008 11:50:43 AM EST

Originally Posted By Mike_G:
Assuming use of a heavier load e.g. Mk262 or Hornady TAP 5.56 75gr and a 1/7 twist rate how do a 10.5" and a 16" barrel compare in:

*effective range
*terminal ballistics / fragmentation
*How does shooting with a suppressor affect performance +/-
*Reliability

I supect the 16" barrel would be better than the 10.5" in each category, but is the difference significant? At what range would you put down the SBR and pick up a carbine or rifle with 16" + barrel?

Are there any websites that explain the differences?


At any range where maneuverability of the 10.5 wasn't MANDATORY. I would pick an SBR'ed PS90 for close up before I would a 10.5" AR anyways.

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Link Posted: 2/12/2008 5:39:03 PM EST

Originally Posted By Mike_G:
Assuming use of a heavier load e.g. Mk262 or Hornady TAP 5.56 75gr and a 1/7 twist rate how do a 10.5" and a 16" barrel compare in:



*effective range


The Ammo Oracle


*terminal ballistics / fragmentation


again The Ammo Oracle


*How does shooting with a suppressor affect performance +/-


Check out my recent thread here


*Reliability


A great read on barrel length, ballistics and reliability on ChuckHawks


I supect the 16" barrel would be better than the 10.5" in each category, but is the difference significant? At what range would you put down the SBR and pick up a carbine or rifle with 16" + barrel? Are there any websites that explain the differences?


The Ammo Oracle
I also suspect a longer barrel will offer better performance in almost every measurable catagory. But size isn't everything. My SBR is good out to 120+ yards with my ammo of choice. Outside of that I'd reach for a dedicated distance rifle in at least .308, not a longer barrel 5.56...

If you haven't done so yet the Ammo Oracle is a must read, then read it again and then a third time for good measure. It'll answer 95% of your questions.
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Link Posted: 2/12/2008 8:13:19 PM EST
[Last Edit: 2/13/2008 3:53:30 AM EST by Mike_G]
Thanks to sed6 - Question: Do you think switching to a heavier round would extend the effective range of your SBR?

What I got from the Ammo Oracle (and the B&T Ammo labs site reference by ammo oracle) and Hawks article:

-Muzzle vlocity of the 77gr and 75gr 5.56 rounds is around 2624 fps from a 16" bbl
-You lose about 20 fps for each 1" of barrel length reduction
-Based on the above I am estimating a muzzle velocity of about 2500 fps for 77gr 5.56 from a 10.5" barrel
-The 77gr. 5.56 round will still fragment at velocities less than 2100 fps

So how do I calculate how far the77gr 5.56 will travel before reaching a velocity of 2100fps?

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Link Posted: 2/12/2008 9:39:15 PM EST
[Last Edit: 2/12/2008 9:40:41 PM EST by 12_gauge]

I really wonder, would a Nosler BT come into it's own here? They seem to work VERY well from the 5.7 pistols and rifles, 2100-2500fps is roughly their operating range from said weapon. Nosler claims that the BT will expand down to 1600fs. From what I have seen, 12"+ and fragmentation can be expected near the 1800-2400fps range using the FN 5.7x28 as a case study.

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Link Posted: 2/12/2008 10:03:19 PM EST
[Last Edit: 2/12/2008 10:05:00 PM EST by Combat_Jack]
The velocity will be around 2500 fps. Fragmentation will be partial below 2300, nonexistant below 2100.

The guns are more finicky but certainly capable of 100% percent reliability. Use Magpul followers or PMAGs for best results. And an O-ring in the extractor.

Suppressors will typically make a short gun act more like a long one, but you may need to play with buffer weights to make it work 100% others will be able to comment more.

I wouldn't feel undergunned with an SBR to 300M. Never tried it any farther.

EDIT: Fragmentation range will be less than 50M.
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Link Posted: 2/13/2008 4:55:55 AM EST
I guess this forum should be a giant ammo oracle link.
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Link Posted: 2/13/2008 5:06:08 AM EST

Originally Posted By jhud:
I guess this forum should be a giant ammo oracle link.


Maybe, maybe not. I may be missing it but I'm not seeing seeing info with figures (or how to calculate) effective range of the 75 gr and 77gr, 5.56 rounds from a 10.5" barrel.

I got a lot of good info from the Ammo Oracle and B&T Ammo labs, but I am having trouble finding that one last piece of info i.e. How far out in yards / meters will a 75gr or 77gr. 5.56 round effectively fragment when fired from a 10.5" barrel

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Link Posted: 2/13/2008 11:43:39 AM EST
Referring back to my results here question 3 shows a drop of about 200fps per 100 yards. So if you are getting 2500fps at the muzzle, you'd be down to 2100fps by 200 yards. Your question addresses a heavier bullet than the 62gr M855 I tested, though a heavier bullet will go faster farther than a lighter one.

I was full of what if's before I built my SBR. Some research, like you're doing, helped clear things up a bit. I didn't, and you won't, get any absolutes here. The only way to be sure is to build the rifle you want, then go test fire it like I did. My research let me to suspect I'd get decent velocity at intermediate ranges, it was my range time that confirmed this for me though. But until I actually put some rounds in 10% gelatin at those ranges I cannot be 100% positive on the fragmentation. I can though be sure that if I'm shooting at you at that range you will a) duck for cover b) bleed when shot c) die if you loose enough blood. My AR fits my intended purpose, yours should too.
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Link Posted: 2/13/2008 12:29:57 PM EST
[Last Edit: 5/7/2008 9:19:32 AM EST by Molon]

Originally posted by Mike_G:

-Muzzle vlocity of the 77gr and 75gr 5.56 rounds is around 2624 fps from a 16" bbl


Incorrect. The velocity will be more like 2715 FPS.


Originally posted by Mike_G:

You lose about 20 fps for each 1" of barrel length reduction



Invalid. There is no valid equation to determine the change in muzzle velocity across a spectrum of barrel lengths and a variety of ammunition loads. The change in muzzle velocity will depend on a variety of interactive variables such as the barrel length spectrum involved (e.g. 20” to 16” versus to 16” to 14.5”), the operating velocity spectrum involved (e.g. a 20” barrel firing a load with a MV of 3,000 FPS compared to other barrel lengths versus a 20” barrel firing a load with a MV of 3,250 FPS compared to other barrel lengths) and the bullet weight spectrum involved (e.g. a 40 grain V-MAX versus a 75 grain OTM.) The particular powder used in the loads will even cause variations between the spectrum of barrel lengths used.

Examples

An average difference in muzzle velocity between a 14.5” barrel and a 16” barrel using a 75 grain OTM load is approximately 86 fps. This gives you a difference of 57 FPS per inch of barrel.

An average difference between a 20” barrel and a 16” barrel is 108 FPS for a difference of 27 FPS per inch of barrel.

An average difference between a 20” barrel and a 24” barrel is 79 FPS for a difference of approximately 20 FPS per inch of barrel.


Originally posted by Mike_G:

Based on the above I am estimating a muzzle velocity of about 2500 fps for 77gr 5.56 from a 10.5" barrel



Your estimation is far too high. Actual chronographs of MK262 have shown the muzzle velocity to be approximately 2360 PFS from a 10.5” barrel.


Originally posted by Mike_G:

The 77gr. 5.56 round will still fragment at velocities less than 2100 fps



A much more realistic threshold for reliable fragmentation with the 75-77 grain OTM loads is 2,250 FPS. From your 10.5” barrel, this will give you a fragmentation range of approximately 48 yards.


Originally posted by sed6:

My SBR is good out to 120+ yards with my ammo of choice.



If by “good” you mean effective and reliable fragmentation with adequate penetration, please tell me where I can purchase some of this magical ammunition. The 75 grain 5.56 TAP load has the best terminal ballistics of any commercially available load for the 5.56mm platform and as shown above it only has a 48 yard fragmentation range when fired from a 10.5” barrel.

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Link Posted: 2/13/2008 1:06:27 PM EST

Originally Posted By Molon:

Originally posted by Mike_G:

-Muzzle vlocity of the 77gr and 75gr 5.56 rounds is around 2624 fps from a 16" bbl


Incorrect. The velocity will be more like 2715 FPS.


Originally posted by Mike_G:

You lose about 20 fps for each 1" of barrel length reduction



Invalid. There is no valid equation to determine the change in muzzle velocity across a spectrum of barrel lengths and a variety of ammunition loads. The change in muzzle velocity will depend on a variety of variables such as the barrel length spectrum involved (e.g. 20” to 16” versus to 16” to 14.5”), the operating velocity spectrum involved (e.g. a 20” barrel firing a load with a MV of 3,000 FPS compared to other barrel lengths versus a 20” barrel firing a load with a MV of 3,250 FPS compared to other barrel lengths) and the bullet weight spectrum involved (e.g. a 40 grain V-MAX versus a 75 grain OTM.) The particular powder used in the loads will even cause variations between the spectrum of barrel lengths used.

Examples

An average difference in muzzle velocity between a 14.5” barrel and a 16” barrel using a 75 grain OTM load is approximately 86 fps. This gives you a difference of 57 FPS per inch of barrel.

An average difference between a 20” barrel and a 16” barrel is 108 FPS for a difference of 27 FPS per inch of barrel.

An average difference between a 20” barrel and a 24” barrel is 79 FPS for a difference of approximately 20 FPS per inch of barrel.


Originally posted by Mike_G:

Based on the above I am estimating a muzzle velocity of about 2500 fps for 77gr 5.56 from a 10.5" barrel



Your estimation is far too high. Actual chronographs of MK262 have shown the muzzle velocity to be approximately 2360 PFS from a 10.5” barrel.


Originally posted by Mike_G:

The 77gr. 5.56 round will still fragment at velocities less than 2100 fps



A much more realistic threshold for reliable fragmentation with the 75-77 grain OTM loads is 2,250 FPS. From your 10.5” barrel, this will give you a fragmentation range of approximately 48 yards.


Originally posted by sed6:

My SBR is good out to 120+ yards with my ammo of choice.



If by “good” you mean effective and reliable fragmentation with adequate penetration, please tell me where I can purchase some of this magical ammunition. The 75 grain 5.56 TAP load has the best terminal ballistics of any commercially available load for the 5.56mm platform and as shown above it only has a 48 yard fragmentation range when fired from a 10.5” barrel.



Thanks for your input. What source(s) does your data come from? Not that I don't trust you, I'd just like to read for myself. My proposed SBR represents a sizeable investment (for me) and if the effective range is less than 100 yards with the best available ammo, then I'd have to rethink my build.


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Link Posted: 2/13/2008 1:11:27 PM EST

Originally posted by Mike_G:

Thanks for your input. What source(s) does your data come from? Not that I don't trust you, I'd just like to read for myself. My proposed SBR represents a sizeable investment (for me) and if the effective range is less than 100 yards with the best available ammo, then I'd have to rethink my build.



Here's a good place to start: click here
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Link Posted: 2/13/2008 2:04:24 PM EST
I will bet a lower that it will still hurt at 150 yards, maybe more
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Link Posted: 2/13/2008 2:23:26 PM EST
As the barrel gets shorter, 1" becomes a larger percent of the total length. Thus the larger velocity drops at shorter lengths. The post by Molon bears this out.

Personally I can't see going below 14.5" unless the gun is dedicated for CQB.

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Link Posted: 2/13/2008 2:43:18 PM EST
Effective range is dictated mainly by how far you can hit something.

If you want a compromise, get a 12.5.
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Link Posted: 2/13/2008 9:29:42 PM EST
When discussing terminal ballistics, "effective range" (also known as maximum effective range or maximum performance distance) has a specific meaning. From Hornady's Ammunition Test Report and Application Guide;

Maximum Performance Distance: This is based on bullet-retained velocity at distance and the associated expansion, fragmentation and penetration at that velocity. The distance given indicates the point out to which the terminal performance will closely match that as shown in the test results. (performed at close range)

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Link Posted: 2/13/2008 9:32:58 PM EST
That's a crock of shit. That means the effective range of M118LR is 0, since all it does is poke holes in shit.
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Link Posted: 2/14/2008 4:26:11 AM EST

Originally Posted By seahorse:
Personally I can't see going below 14.5" unless the gun is dedicated for CQB.



Whats the average engagement range in yds/meters/feet of a CQB or urban combat scenario....no offense, but I'm looking for empirical data not opinions

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Link Posted: 2/14/2008 5:32:48 AM EST
[Last Edit: 2/14/2008 6:48:35 AM EST by DevL]
I know its not a 10.5" but it gives some insight...

Chronoed my LWRC 5.56 cold hammer forged, chrome lined, 11.75" barrel with 75 grain 5.56 TAP for two ten shot strings suppressed and unsuppressed.

Average muzzle velocity unsuppressed was 2450, suppressed was 2485 fps.

Slowest unsuppressed round was 2419
Fastest suppressed round was 2499

With a fragmentation velocity threshold of 2200 FPS that would be reached at 105 yards unsuppressed and 120 suppressed

Fragmentation threshhold is between 2250 and 2150 for the 5.56 T2 TAP. Worst case scenario would be unsuppressed 2419 and 2250 threshhold and just over 70 yards till fragmentation would not occur. Best case would be suppressed 2499 velocity and a threshhold of 2150 for 150 yards till fragmentation would not occur.

The barrel and ammo combo displayed a rather large velocity variation between rounds in each string. Ambient temp was 60 degrees F. Warmer weather would increase the range of fragmentation and colder weather would reduce it. Rounds were fired in 3-4 second intervals with a propensity for the rounds increasing in velocity as the chamber warmed but there were several slow rounds at the end of the strings and fast rounds in the beginging.

If you care about the range of fragmentation at all I would highly suggest a 11.5" or even a 12.5" barrel for a general purpose rifle. Shorter barrels also cause more bullet yaw as the bullet leaves the barrel. I had to stop testing of the above rifle when I had a 55 grain bullet yaw and bounce off the blast baffle, plow through all my baffles, and self destructed in the end cap. I am still waiting on my suppressor to return from a rebuild. This is a very rare occurance to be sure but it is more likely with shorter barrels (this comes from AAC).

I had my barrel made to give the absoloute shortest upper possible when combining a 9" midlength rail and an AAC SPR/M4 suppressor... thus the odd 11.75" length. It is only about an inch longer than a 10.5" M4-2000 combo unsuppressed or suppressed but I have a lot more railspace, much lower back pressure, and less noise and blast suppressed and unsuppressed with enough added range/velocity that the 1" extra length is totally worth it.

Past the fragmentation range the approx 1" long bullet still yaws and would give about the same performance as an AK74U (5.45x39 Krink) at the same range. The max effective range of the AK74U is listed at 300m... whatever that means.

I hope you realise you will NOT get 2500 fps from a 10.5" 5.56 chambered, chrome lined barrel. Heck it required a warm barrel, comfortable temps, a suppressor, and 11.75" of barrel to get ONE shot to 2499.

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Link Posted: 2/14/2008 9:37:44 AM EST
Thanks for all the info guys. I'd love an SBR for the fun and for a good CQB / SHTF tool. I aleady have a 16" AR. All of this discussion has led me to question whether to build an SBR and whether to stick with the 5.56 platform at all. Though the things that attracted me to the platform to begin with are low recoil, lighter weight, the ability to carry more ammo and the modularity (is that a word?) and availability of accessories. Maybe I should consider switching to the 6.8SPC.

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Link Posted: 2/14/2008 9:44:59 AM EST
Taggage

I wonder if the ballistics for a 10.5" would be about the same for a 10.3" like
the SEALs Mk18 Mod0 rifles?



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Link Posted: 2/14/2008 10:20:31 AM EST

Originally Posted By HermanSnerd:
Taggage

I wonder if the ballistics for a 10.5" would be about the same for a 10.3" like
the SEALs Mk18 Mod0 rifles?





Thats what I was assuming. If the ballistics data I'm getting from this thread are accurate, why do the Navy Seals use the Mk18?

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Link Posted: 2/14/2008 10:56:02 AM EST
Maybe because there's more to killing people than the exact distance a given load is supposed to fragment/not fragment at.....

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Link Posted: 2/14/2008 11:02:36 AM EST

Originally Posted By Gunwritr:
Maybe because there's more to killing people than the exact distance a given load is supposed to fragment/not fragment at.....
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Link Posted: 2/14/2008 11:55:11 AM EST
How about if Combat Jack and Molon wrestled for it. If Molon wins I don't build an SBR is Cactus Jack wins I build it.

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Link Posted: 2/14/2008 12:45:42 PM EST
[Last Edit: 2/14/2008 12:51:32 PM EST by ma96782]

Whats the average engagement range in yds/meters/feet of a CQB or urban combat scenario....no offense, but I'm looking for empirical data not opinions



No offense.......so........

That kind of "Talk"..........gets you a free trip to Iraq on the US Tax Payer's buck. Feel free to Join Up.

Don't forget to, e-mail us......."arm chair folks." Then again, it may not be "scientific enough" for you.

There is always someone screaming for, "REAL WORLD DATA." And, don't bother looking at the LE data cause..........I doubt they have much. Or, at least not enough to make firm statements as to, "effectiveness," with the stated weapon and ammo. Not to mention: bullet placement, environmental conditions, clothing worn and size/health/condition of the person who is shot. Then, you could also throw in the EMS and Hospital's efforts, that skewed the results.

Aloha, Mark

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Link Posted: 2/14/2008 12:45:44 PM EST

Originally Posted By DevL:
I know its not a 10.5" but it gives some insight...

Chronoed my LWRC 5.56 cold hammer forged, chrome lined, 11.75" barrel with 75 grain 5.56 TAP for two ten shot strings suppressed and unsuppressed.

Average muzzle velocity unsuppressed was 2450, suppressed was 2485 fps.

Slowest unsuppressed round was 2419
Fastest suppressed round was 2499

With a fragmentation velocity threshold of 2200 FPS that would be reached at 105 yards unsuppressed and 120 suppressed

Fragmentation threshhold is between 2250 and 2150 for the 5.56 T2 TAP. Worst case scenario would be unsuppressed 2419 and 2250 threshhold and just over 70 yards till fragmentation would not occur. Best case would be suppressed 2499 velocity and a threshhold of 2150 for 150 yards till fragmentation would not occur.

The barrel and ammo combo displayed a rather large velocity variation between rounds in each string. Ambient temp was 60 degrees F. Warmer weather would increase the range of fragmentation and colder weather would reduce it. Rounds were fired in 3-4 second intervals with a propensity for the rounds increasing in velocity as the chamber warmed but there were several slow rounds at the end of the strings and fast rounds in the beginging.

If you care about the range of fragmentation at all I would highly suggest a 11.5" or even a 12.5" barrel for a general purpose rifle. Shorter barrels also cause more bullet yaw as the bullet leaves the barrel. I had to stop testing of the above rifle when I had a 55 grain bullet yaw and bounce off the blast baffle, plow through all my baffles, and self destructed in the end cap. I am still waiting on my suppressor to return from a rebuild. This is a very rare occurance to be sure but it is more likely with shorter barrels (this comes from AAC).

I had my barrel made to give the absoloute shortest upper possible when combining a 9" midlength rail and an AAC SPR/M4 suppressor... thus the odd 11.75" length. It is only about an inch longer than a 10.5" M4-2000 combo unsuppressed or suppressed but I have a lot more railspace, much lower back pressure, and less noise and blast suppressed and unsuppressed with enough added range/velocity that the 1" extra length is totally worth it.

Past the fragmentation range the approx 1" long bullet still yaws and would give about the same performance as an AK74U (5.45x39 Krink) at the same range. The max effective range of the AK74U is listed at 300m... whatever that means.

I hope you realise you will NOT get 2500 fps from a 10.5" 5.56 chambered, chrome lined barrel. Heck it required a warm barrel, comfortable temps, a suppressor, and 11.75" of barrel to get ONE shot to 2499.



That is a bummer about your can. I would have had a heart attack.


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Link Posted: 2/14/2008 1:09:07 PM EST

Originally Posted By ma96782:

Whats the average engagement range in yds/meters/feet of a CQB or urban combat scenario....no offense, but I'm looking for empirical data not opinions



No offense.......so........

That kind of "Talk"..........gets you a free trip to Iraq on the US Tax Payer's buck. Feel free to Join Up.

Don't forget to, e-mail us......."arm chair folks." Then again, it may not be "scientific enough" for you.

There is always someone screaming for, "REAL WORLD DATA." And, don't bother looking at the LE data cause..........I doubt they have much. Or, at least not enough to make firm statements as to, "effectiveness," with the stated weapon and ammo. Not to mention: bullet placement, environmental conditions, clothing worn and size/health/condition of the person who is shot. Then, you could also throw in the EMS and Hospital's efforts, that skewed the results.

Aloha, Mark



What started out as a simple request for some stats has blown waaaay out of proportion and thats my fault so lets all cool off and declare this thread dead.

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Link Posted: 2/14/2008 1:12:44 PM EST

Originally Posted By Mike_G:

Originally Posted By ma96782:

Whats the average engagement range in yds/meters/feet of a CQB or urban combat scenario....no offense, but I'm looking for empirical data not opinions



No offense.......so........

That kind of "Talk"..........gets you a free trip to Iraq on the US Tax Payer's buck. Feel free to Join Up.

Don't forget to, e-mail us......."arm chair folks." Then again, it may not be "scientific enough" for you.

There is always someone screaming for, "REAL WORLD DATA." And, don't bother looking at the LE data cause..........I doubt they have much. Or, at least not enough to make firm statements as to, "effectiveness," with the stated weapon and ammo. Not to mention: bullet placement, environmental conditions, clothing worn and size/health/condition of the person who is shot. Then, you could also throw in the EMS and Hospital's efforts, that skewed the results.

Aloha, Mark



What started out as a simple request for some stats has blown waaaay out of proportion and thats my fault so lets all cool off and declare this thread dead.


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Link Posted: 2/14/2008 1:22:14 PM EST

Originally Posted By Mike_G:

Originally Posted By HermanSnerd:
Taggage

I wonder if the ballistics for a 10.5" would be about the same for a 10.3" like
the SEALs Mk18 Mod0 rifles?





Thats what I was assuming. If the ballistics data I'm getting from this thread are accurate, why do the Navy Seals use the Mk18?


It's compact, easier to manuver through tight passageways and compartments, etc etc etc.

Navy VBSS teams and Coast Guard TACLET, MSST, and MSRT use them as well.
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Link Posted: 2/14/2008 8:45:08 PM EST

Originally Posted By Molon:



Originally posted by sed6:

My SBR is good out to 120+ yards with my ammo of choice.



If by “good” you mean effective and reliable fragmentation with adequate penetration, please tell me where I can purchase some of this magical ammunition. The 75 grain 5.56 TAP load has the best terminal ballistics of any commercially available load for the 5.56mm platform and as shown above it only has a 48 yard fragmentation range when fired from a 10.5” barrel.



Yeah, but I wasn't talking about the TAP round now was I? You need to read more carefully before you sharpshoot someone.
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Link Posted: 2/14/2008 8:55:07 PM EST
a
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Link Posted: 2/15/2008 1:49:53 AM EST
I think the 10.5

Is the BEST Home Protection and Self Protection Carbine

We CIVI wont be shooting BAD GUYS @ 200 YARDS hMight as well go 18inch or 20 hand BHWB 5.56mm 77gr OTM
aka MK262
1 mag of M856 and another ranger 64

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Link Posted: 2/15/2008 1:59:47 AM EST
height=8
Originally Posted By 12_gauge:
height=8
Originally Posted By Mike_G:
Assuming use of a heavier load e.g. Mk262 or Hornady TAP 5.56 75gr and a 1/7 twist rate how do a 10.5" and a 16" barrel compare in:

*effective range
*terminal ballistics / fragmentation
*How does shooting with a suppressor affect performance +/-
*Reliability

I supect the 16" barrel would be better than the 10.5" in each category, but is the difference significant? At what range would you put down the SBR and pick up a carbine or rifle with 16" + barrel?

Are there any websites that explain the differences?


At any range where maneuverability of the 10.5 wasn't MANDATORY. I would pick an SBR'ed PS90 for close up before I would a 10.5" AR anyways.



Not me

I like the 10.5 LMT along with the 75gr OTM


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Link Posted: 2/15/2008 2:01:54 AM EST
[Last Edit: 2/15/2008 2:05:27 AM EST by 6906P229]
height=8
Originally Posted By Mike_G:
Thanks to sed6 - Question: Do you think switching to a heavier round would extend the effective range of your SBR?

What I got from the Ammo Oracle (and the B&T Ammo labs site reference by ammo oracle) and Hawks article:

-Muzzle vlocity of the 77gr and 75gr 5.56 rounds is around 2624 fps from a 16" bbl
-You lose about 20 fps for each 1" of barrel length reduction
-Based on the above I am estimating a muzzle velocity of about 2500 fps for 77gr 5.56 from a 10.5" barrel
-The 77gr. 5.56 round will still fragment at velocities less than 2100 fps

So how do I calculate how far the77gr 5.56 will travel before reaching a velocity of 2100fps?



I would Never put a 16inch+ Bird cage barrel on a carbine

I would worry about Shot Placement over all this frag range info


14.5 inch would be MAX

12.5 would be nice



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Link Posted: 2/15/2008 2:02:27 AM EST
height=8
Originally Posted By Combat_Jack:
The velocity will be around 2500 fps. Fragmentation will be partial below 2300, nonexistant below 2100.

The guns are more finicky but certainly capable of 100% percent reliability. Use Magpul followers or PMAGs for best results. And an O-ring in the extractor.

Suppressors will typically make a short gun act more like a long one, but you may need to play with buffer weights to make it work 100% others will be able to comment more.

I wouldn't feel undergunned with an SBR to 300M. Never tried it any farther.

EDIT: Fragmentation range will be less than 50M.


+1

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Link Posted: 2/15/2008 2:04:16 AM EST
height=8
Originally Posted By Gunwritr:
Maybe because there's more to killing people than the exact distance a given load is supposed to fragment/not fragment at.....


Very good point

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Link Posted: 2/15/2008 7:05:28 AM EST

Originally Posted By sed6:

Originally Posted By Molon:



Originally posted by sed6:

My SBR is good out to 120+ yards with my ammo of choice.



If by “good” you mean effective and reliable fragmentation with adequate penetration, please tell me where I can purchase some of this magical ammunition. The 75 grain 5.56 TAP load has the best terminal ballistics of any commercially available load for the 5.56mm platform and as shown above it only has a 48 yard fragmentation range when fired from a 10.5” barrel.



Yeah, but I wasn't talking about the TAP round now was I? You need to read more carefully before you sharpshoot someone.



I wouldn't know what ammunition you were talking about, because you still haven't told us what this magical ammuition of yours that has better terminal ballistics than Hornady's 75 grain TAP is.
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Link Posted: 2/15/2008 7:35:24 AM EST

Originally Posted By Gunwritr:
Maybe because there's more to killing people than the exact distance a given load is supposed to fragment/not fragment at.....



People love dissecting minutia on the internet...
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Link Posted: 2/15/2008 7:59:53 PM EST

Originally Posted By Molon:

Originally Posted By sed6:

Originally Posted By Molon:



Originally posted by sed6:

My SBR is good out to 120+ yards with my ammo of choice.



If by “good” you mean effective and reliable fragmentation with adequate penetration, please tell me where I can purchase some of this magical ammunition. The 75 grain 5.56 TAP load has the best terminal ballistics of any commercially available load for the 5.56mm platform and as shown above it only has a 48 yard fragmentation range when fired from a 10.5” barrel.



Yeah, but I wasn't talking about the TAP round now was I? You need to read more carefully before you sharpshoot someone.



I wouldn't know what ammunition you were talking about, because you still haven't told us what this magical ammuition of yours that has better terminal ballistics than Hornady's 75 grain TAP is.


Again, more reading and less supposition on your part would lead you to my results with the XM193 and M855 rounds here.
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Link Posted: 2/16/2008 7:37:49 AM EST
[Last Edit: 2/16/2008 7:38:10 AM EST by 6906P229]
SHTF = 5.56 75gr TAP/ 223rem 75gr TAP/ BH 75gr OTM

Better than M855 and M193 in 10.5 barrel



AKA FMJ

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Link Posted: 2/16/2008 10:06:17 AM EST
[Last Edit: 2/16/2008 10:21:35 AM EST by DevL]

Originally Posted By sed6:

Originally Posted By Molon:

Originally Posted By sed6:

Originally Posted By Molon:



Originally posted by sed6:

My SBR is good out to 120+ yards with my ammo of choice.



If by “good” you mean effective and reliable fragmentation with adequate penetration, please tell me where I can purchase some of this magical ammunition. The 75 grain 5.56 TAP load has the best terminal ballistics of any commercially available load for the 5.56mm platform and as shown above it only has a 48 yard fragmentation range when fired from a 10.5” barrel.



Yeah, but I wasn't talking about the TAP round now was I? You need to read more carefully before you sharpshoot someone.



I wouldn't know what ammunition you were talking about, because you still haven't told us what this magical ammuition of yours that has better terminal ballistics than Hornady's 75 grain TAP is.


Again, more reading and less supposition on your part would lead you to my results with the XM193 and M855 rounds here.


I noticed you quoted 2600 fps as the minimum velocity when it is actually 2700 fps. You should revise your posting accordingly. This throws a wrench in your whole argument. I could have just as easily quoted the minimum where fragmentation SOMETIMES occurs as 2100 fps for 5.56 TAP but often just breaks in half and it would add a bunch of range. M855 and M193 will not reliably and violently fragment at 2600 FPS.

Here is a nice ammo oracle quote...

Testing by combat surgeon Col. Martin L. Fackler, MD (USA Medical Corps, retired), determined that M193 and M855 bullets need to strike flesh at 2,700 feet per second in order to reliably fragment. Between 2,500 fps and 2,700 fps, the bullet may or may not fragment.

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Link Posted: 2/16/2008 4:12:28 PM EST
[Last Edit: 2/16/2008 4:15:09 PM EST by sed6]

Originally Posted By DevL:

Originally Posted By sed6:

Originally Posted By Molon:

Originally Posted By sed6:

Originally Posted By Molon:



Originally posted by sed6:

My SBR is good out to 120+ yards with my ammo of choice.



If by “good” you mean effective and reliable fragmentation with adequate penetration, please tell me where I can purchase some of this magical ammunition. The 75 grain 5.56 TAP load has the best terminal ballistics of any commercially available load for the 5.56mm platform and as shown above it only has a 48 yard fragmentation range when fired from a 10.5” barrel.



Yeah, but I wasn't talking about the TAP round now was I? You need to read more carefully before you sharpshoot someone.



I wouldn't know what ammunition you were talking about, because you still haven't told us what this magical ammuition of yours that has better terminal ballistics than Hornady's 75 grain TAP is.


Again, more reading and less supposition on your part would lead you to my results with the XM193 and M855 rounds here.


I noticed you quoted 2600 fps as the minimum velocity when it is actually 2700 fps. You should revise your posting accordingly. This throws a wrench in your whole argument. I could have just as easily quoted the minimum where fragmentation SOMETIMES occurs as 2100 fps for 5.56 TAP but often just breaks in half and it would add a bunch of range. M855 and M193 will not reliably and violently fragment at 2600 FPS.

Here is a nice ammo oracle quote...

Testing by combat surgeon Col. Martin L. Fackler, MD (USA Medical Corps, retired), determined that M193 and M855 bullets need to strike flesh at 2,700 feet per second in order to reliably fragment. Between 2,500 fps and 2,700 fps, the bullet may or may not fragment.


A good quote, by a good source. I have however done lots of additional reading beyond that and 2600fps IS the lowest accepted threshold for reliable fragmentation based upon numerous sources. 2700 WAS the number. I could find the links to help promote a more thorough understanding, but this really isn't my arguement and no one seems to want to expand their understanding. I'm outta here

ETA: I'd say that TAP would by my preferable round for shooting zombies, however at more than twice the cost per round, XM193 or M855 will have to do for SHTF stores.
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Link Posted: 2/18/2008 5:24:44 AM EST
so at 2300 FPS 75gr TAP wont frag at all?

QUESTION
I never heard about the 75gr AMAX BULLET?
If loaded to 5.56mm pressure will this bullet frag
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Link Posted: 2/18/2008 7:12:55 AM EST
I think it would be interesting to edit the the frag chart (a little face lift) and include short BR as the new generation of ammo.

www.ar15.com/content/page.html?id=173


Making only one chart that should include all 5.56/223 that passed the FBI test and are available.
I don't mind to do it but will need chrono data, etc...

This should answer a lot of questions and avoid..well, you know

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Link Posted: 2/19/2008 8:11:57 AM EST
[Last Edit: 2/19/2008 8:18:43 AM EST by DevL]

Originally Posted By FMJ:
so at 2300 FPS 75gr TAP wont frag at all?

QUESTION
I never heard about the 75gr AMAX BULLET?
If loaded to 5.56mm pressure will this bullet frag


I dont think you can load that bullet to 5.56 pressures and mag length. I dont like single loading my defensive ammo.

Yes, 75 grain TAP will reliably fragment at 2300 FPS. It can fragment down to 2150 but not reliably or fail to fragment at 2250. This is also very grey. Its not like you get a 100% failure to fragment. The faster the bullet is going the more violent the fragmentation and then it becomes less and less with reduced velocity till it just breaks in half and then stops framgenting altogether. There is not a WALL where it goes straight from a violnet hailstorm of lead every time to a solid slug.

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Link Posted: 2/19/2008 9:35:38 AM EST

Originally Posted By DevL:

Originally Posted By FMJ:
so at 2300 FPS 75gr TAP wont frag at all?

QUESTION
I never heard about the 75gr AMAX BULLET?
If loaded to 5.56mm pressure will this bullet frag


I dont think you can load that bullet to 5.56 pressures and mag length. I dont like single loading my defensive ammo.

Yes, 75 grain TAP will reliably fragment at 2300 FPS. It can fragment down to 2150 but not reliably or fail to fragment at 2250. This is also very grey. Its not like you get a 100% failure to fragment. The faster the bullet is going the more violent the fragmentation and then it becomes less and less with reduced velocity till it just breaks in half and then stops framgenting altogether. There is not a WALL where it goes straight from a violnet hailstorm of lead every time to a solid slug.



Thanks AGAIN for the good info
I was thinking 2300fps

bummer on Amax single shot
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Link Posted: 2/19/2008 12:56:34 PM EST
[Last Edit: 2/19/2008 1:00:30 PM EST by vmpglenn]
If you really want a reach-out-and-touch-them SBR, just do yourself a favor and get a 12.5" 1:11 twist, SAAMI-II chambered 6.8SPC barrel from Tim at Cardinal Armory (formerly Ko-tonics). He'll be offering these ready to go starting in March/April. SSA combat loads with the enhanced frag 115gr SMKs will fragment out to 150 yards out of a 12.5" barrel. In general, the pressure curve generated by 6.8SPC is much better matched to short barrels than that of 5.56, so you don't see as much velocity drop going from, say, 16" to 12.5" in 6.8SPC.

As for ammo cost, if you're shooting 75gr TAP or 77gr Mk 262, you're into the $1 per round category anyway for 5.56, which is actually a bit more than you'd pay for the SSA 6.8 ammo.

If you handload, ammo costs are more than reasonable and you can tailor loads for your Cardinal Armory 12.5" barrel that will fragment out to 170 yards. I've got 115gr bullets coming out of my 12.5" Cardinal Armory barrel at 2500fps, BC of .340. Fragmentation threshold of 6.8SPC (according to Doc Roberts) is 2100fps. Any ballistics program will allow you to do the math...

6.8SPC and SBRs: a match made in heaven.

ETA: SSA is on the verge of releasing inexpensive (relatively speaking) plinking ammo in 6.8SPC, which should allow for range use and practice shooting at a cost at or near 5.56. Again, if you handload, ammo cost is more than reasonable.

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Link Posted: 2/19/2008 1:48:00 PM EST

Originally Posted By 6906P229:


I would Never put a 16inch+ Bird cage barrel on a carbine

I would worry about Shot Placement over all this frag range info


14.5 inch would be MAX

12.5 would be nice




How about a midlength

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Link Posted: 3/1/2008 3:43:35 PM EST
[Last Edit: 3/5/2008 3:54:55 PM EST by Molon]

Originally Posted By sed6:

Originally Posted By Molon:

Originally Posted By sed6:

Originally Posted By Molon:



Originally posted by sed6:

My SBR is good out to 120+ yards with my ammo of choice.



If by “good” you mean effective and reliable fragmentation with adequate penetration, please tell me where I can purchase some of this magical ammunition. The 75 grain 5.56 TAP load has the best terminal ballistics of any commercially available load for the 5.56mm platform and as shown above it only has a 48 yard fragmentation range when fired from a 10.5” barrel.



Yeah, but I wasn't talking about the TAP round now was I? You need to read more carefully before you sharpshoot someone.



I wouldn't know what ammunition you were talking about, because you still haven't told us what this magical ammuition of yours that has better terminal ballistics than Hornady's 75 grain TAP is.


Again, more reading and less supposition on your part would lead you to my results with the XM193 and M855 rounds here.




Your post that you reference "here" is Full of Fail. Here are just a few examples of your fundamentally flawed data and conclusions.

In your post you state that M855 fired from your 11.25” barrel has an average velocity of 2776 fps at a distance of 20 feet. You then claim that same M855 fired from your same barrel has an average retained velocity of 2723 fps at a distance of 50 yards.

It is physically impossible for a 62 grain bullet with a ballistic coefficient of .304 and a velocity of 2776 fps at 20 feet to have a retained velocity of 2723 fps at 50 yards. The simple use Oehler’s Ballistic Explorer shows the retained velocity at 50 yards would be 2646 fps. You’re off by 77 fps. You fail.







Next, you make the ridiculous claim that velocity loss for M855 is only “an average of 200 fps per 100 yards.” Again, the simple use of Oehler’s Ballistic Explorer shows that your barrel firing M855 will loose 295 fps in the first 100 yards of flight. You’re off by 95 fps this time. You fail again.




You then make the absolutely absurd claim that M855 fired from your 11.25” barrel will (your words from your post) “fragment effectively” out to 139 yards. Even if M855 fragmented effectively down to 2600 fps according to your dubious claim in your post, M855 fired from your barrel will drop below 2600 fps at a distance of only 66 yards. You’re off by 73 yards! You just keep on failing.




Using the accepted fragmentation threshold for M855 of 2700 fps, M855 fired from your 11.25” barrel will have a reliable fragmentation range of only 31 yards.




The additional problem with M855 is that even when it does impact the target at a velocity of 2700 fps, a large percentage of the time it will have a very long distance until yaw and even longer distance until maximum fragmentation.




The thorax of the average adult male in America has an anterior-posterior diameter of approximately 9.5”. The center of the heart lies approximately 3.5” below the anterior chest wall, the great vessels roughly 5.5” and the spinal chord about 7”. (For an undernourished hadji, the anterior-posterior diameter of the thorax is closer to 7.5” with the distance to the internal organs correspondingly shortened.)




As you can see in the gel-shot of M855 posted above, even when the bullet impacts the target at 2700 fps, there are times when the bullet doesn’t even begin to yaw until almost 7” of travel. At this point, it will have already sailed past most of the vital organs in the thoracic cavity. (In a hadji, the bullet will be on its way out of his back.) At the point of maximum fragmentation, 9.5”, the bullet would be exiting the back of an average adult American male and long since exited the body of a hadji.





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Link Posted: 3/4/2008 8:49:46 AM EST
[Last Edit: 3/4/2008 8:57:18 AM EST by 2stage]

Originally Posted By Combat_Jack:


Originally posted By 2stage:

When discussing terminal ballistics, "effective range" (also known as maximum effective range or maximum performance distance) has a specific meaning. From Hornady's Ammunition Test Report and Application Guide;

Maximum Performance Distance: This is based on bullet-retained velocity at distance and the associated expansion, fragmentation and penetration at that velocity. The distance given indicates the point out to which the terminal performance will closely match that as shown in the test results. (performed at close range)


That's a crock of shit. That means the effective range of M118LR is 0, since all it does is poke holes in shit.



Well Mr. Jack, since you seem to think you know so much more about terminal ballistics than the good people at Hornady, you should give them a call and inform them that their information is “a crock of shit.” Let us know how that conversation goes.

Hornady’s Ammunition Test Report and Application Guide is a reference on the terminal ballistics of their TAP line of ammunition. Accordingly, their definition of “Maximum Performance Distance” is tailored to the bullets used in their TAP line of ammunition. Not surprisingly, the 175 grain Sierra MatchKing that is loaded in M118LR is nowhere to be found in Hornady’s TAP line of ammunition.

Contrary to your crude assessment of the terminal ballistics of M118LR, the 175 grain Sierra MatchKing is capable of more than just being able to “poke holes in shit” depending on the diameter of the open-tip meplat and the striking distance/impact velocity. While the 175 grain Sierra MatchKing loaded in M118LR does often perform like a non-fragmenting, non-expanding FMJ bullet, no one in this thread has been discussing that type of bullet (except for you of course.)

Since you were compelled to throw your red herring into the discussion, we can easily amend Hornady’s definition of “Maximum Performance Distance” to accommodate your diversion. When discussing bullets that behave as non-fragmenting, non-expanding FMJ bullets, simply delete the reference to expansion and fragmentation for the following definition:

Maximum Performance Distance: This is based on bullet-retained velocity at distance and the associated penetration performance at that velocity. The distance given indicates the point out to which the terminal performance will closely match that as shown in the test results. (performed at close range)



courtesy of Dr. G.K. Roberts and Dr. M Fackler


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