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Posted: 8/5/2008 4:58:35 PM EDT
I'm curious if anyone knows... I have a 7.5" barrel AR-15 pistol, and after shooting found a perfect bullet in an inch or two of dirt where I was shooting... looked like you just pulled it off the case, not deformed in any way (could see rifling marks around the back though)

I'm guessing that was a fluke (I was using Wolf after all), but it does stand to reason that a shorter barrel = lower speed by the time it leaves the barrel = less (bullet) force.

So anyone know how much force a bullet out of a 7.5" barrel has compared to one out of a 16" or 20" barrel?

Link Posted: 8/6/2008 5:46:11 AM EDT
Most things I've read have the 5.56/223 losing about 50 fps per inch of barrel length. So if you are getting about 3000 fps from a 16" barrel - and you go to a 10" barrel, you should see it drop to around 2700 fps or so. But every barrel is different, so it could be a bit higher or lower.

There are a bunch of old post about this - use the search function and have fun.

Take care,
Bob S.
Link Posted: 8/6/2008 6:16:45 AM EDT
[Last Edit: 8/6/2008 12:38:50 PM EDT by FIGJAM]
Here's some actual data from my 7.5" White Oak Armament Barrel.

For instance,  55gr M193 is rated at 3,200 fps from a 20" barrel and 62gr M855 is rated at 3,100 fps from a 20" barrel.  Velocity from my barrel for M193 was 2,450 and M855 was 2,300 fps.  I also had some Hornady NATO pressure 75gr rated at 2,665 from a 14.5" barrel.  My actual velocity was 2,100 fps.

The velocity loss for M193 was 60 fps/in.  The M855 lost 64 fps/in and the Hornady 75gr lost 80fps/in.

The energy equation for foot pounds is (grain weight x velocity fps x velocity fps) divided by 450282.  

Link to pistol velocity page

M193 20"  1,251 fpe   7.5"  733 fpe  41% loss
M855 20"  1,323 fpe   7.5"  728 fpe  45% loss
Hornady 75g TAP 14.5" 1,183 fpe  7.5" 734 fpe   38% loss

If my math is correct.
Link Posted: 8/6/2008 11:19:34 AM EDT

Originally Posted By FIGJAM:
Here's some actual data from my 7.5" White Oak Armament Barrel.

For instance,  55gr M193 is rated at 3,200 fps from a 20" barrel and 62gr M855 is rated at 3,100 fps from a 20" barrel.  Velocity from my barrel for M193 was 2,450 and M855 was 2,300 fps.  I also had some Hornady NATO pressure 75gr rated at 2,665 from a 14.5" barrel.  My actual velocity was 2,100 fps.

The velocity loss for M193 was 60 fps/in.  The M855 lost 64 fps/in and the Hornady 75gr lost 80fps/in.

The energy equation for foot pounds is (grain weight x velocity fps x velocity fps) divided by 450282.  

Link to pistol velocity page

M193 20"  1,251 fpe   7.5"  733 fpe  41% loss
M855 20"  1,323 fpe   7.5"  728 fpe  45% loss
Hornady 75g TAP 14.5" 1,183 fpe  734 fpe   38% loss

If my math is correct.


If your numbers are correct, thats still a hefty ammount of energy to deposit in a person via self defence.
Link Posted: 8/6/2008 12:54:36 PM EDT
[Last Edit: 8/6/2008 12:56:08 PM EDT by FIGJAM]

Originally Posted By Getnlwr:

If your numbers are correct, thats still a hefty ammount of energy to deposit in a person via self defence.


I'm pretty  confident they are correct because they match numbers that have been discussed before.  The problem with FMJ though is that unless you can get it to stop and release that energy, you'll just be punching 22lr holes.  The question would be how stabilized are the bullets coming from a 1/9 or 1/8 twist pistol barrel at those velocities.  If they are highly stabilized it's unlikely they will yaw and cause problems.  If they are just on the verge of stable, they will be quite unpleasant.   Of course, one can overcome these shortcomings by using soft or hollow points or  just volume.  20 or 30 guaranteed M855 holes would be quite unpleasant.  
Link Posted: 8/8/2008 6:36:02 AM EDT

Originally Posted By Getnlwr:

Originally Posted By FIGJAM:
Here's some actual data from my 7.5" White Oak Armament Barrel.

For instance,  55gr M193 is rated at 3,200 fps from a 20" barrel and 62gr M855 is rated at 3,100 fps from a 20" barrel.  Velocity from my barrel for M193 was 2,450 and M855 was 2,300 fps.  I also had some Hornady NATO pressure 75gr rated at 2,665 from a 14.5" barrel.  My actual velocity was 2,100 fps.

The velocity loss for M193 was 60 fps/in.  The M855 lost 64 fps/in and the Hornady 75gr lost 80fps/in.

The energy equation for foot pounds is (grain weight x velocity fps x velocity fps) divided by 450282.  

Link to pistol velocity page

M193 20"  1,251 fpe   7.5"  733 fpe  41% loss
M855 20"  1,323 fpe   7.5"  728 fpe  45% loss
Hornady 75g TAP 14.5" 1,183 fpe  734 fpe   38% loss

If my math is correct.


If your numbers are correct, thats still a hefty ammount of energy to deposit in a person via self defence.
But you're only making a .223 caliber hole
Link Posted: 8/8/2008 8:23:03 AM EDT
[Last Edit: 8/8/2008 8:45:53 AM EDT by FIGJAM]
Not me.  I'm making 45 caliber holes.  



Link Posted: 8/8/2008 9:24:40 PM EDT
Figjam, you think those rounds will expand out of a 7.5? Do you know he expansion threshold, hornady still hasnt gotten back to me, lost my business.
Link Posted: 8/9/2008 7:01:45 AM EDT
55 grain Winchester fired from a 16" AR rifle and 7.5" AR pistol I get the same performance they both go throught the 2 rear doors of a old junk 58 chevy at 20 feet away. I think that's enough power for anybody.
Link Posted: 8/9/2008 8:50:03 AM EDT
[Last Edit: 8/9/2008 8:54:07 AM EDT by FIGJAM]

Originally Posted By deuc224:
Figjam, you think those rounds will expand out of a 7.5? Do you know he expansion threshold, hornady still hasnt gotten back to me, lost my business.


If loaded to 2,300 fps (NATO pressures), they will fully petal to probably 30 to 50 yards.  After that, it's varying degrees.  I'm saving up some newspapers and 5 gallon buckets to be absolutely sure though.  
Link Posted: 8/10/2008 11:35:28 AM EDT
cool figjam, seems me and you are on the never ending journey to find the perfect 7.5 round. So at 2300fps the round will expand, correct? If/when you load it up and if it is sucessful, will you share the recipe of your load?  please
Link Posted: 8/10/2008 12:00:38 PM EDT
[Last Edit: 8/10/2008 12:13:06 PM EDT by FIGJAM]
No problem.  It should be around 19.5 to 20 grains of Reloader 7 to drive that 62 grain bullet.  If I can't get it to 2,300 without significant pressure issues, I'll try the 53 grain TSX which I'm pretty sure I can get there.

What's interesting is to run Barnes published loads through Quick-load which is a load predicting program.  Barnes says max load with the 63gr TSX is 25.5 grains of Varget.  Quickload predicts that a way no go.  So, either Barnes got a weak load of Varget or Quickload's bearing/compression data for the TSX is off (or what Barnes published is wrong).  

www.barnesbullets.com/images/223RemingtonWeb.pdf

I would use Varget but it's only 80% consumed in a 7.5" barrel according to Quickload.  Reloader 7 will be 99% consumed and that should take care of some of the muzzle blast, hopefully.
Link Posted: 8/10/2008 12:41:55 PM EDT
i hope the reloader 7 load works out with the 62gr round. That would be a potent round to pack. it says the 53gr round wont be stable out of our type of twist rates. Wonder if thats true
Link Posted: 8/10/2008 1:40:56 PM EDT
[Last Edit: 8/10/2008 1:45:32 PM EDT by FIGJAM]
Over stabilization (two much twist) won't be an issue.  Sure it affects accuracy but I'm not shooting past 200 yards and these guns are not designed to be tack drivers.   The reason that over stabilization causes accuracy problems is do to varying densities within bullets.  Greater spin causes greater wobble, wobble affects trajectory.  Also, spinning bullets too fast can cause the jacket to separate from the core, but that's obviously not going to happen with a Barnes bullet.
Link Posted: 8/15/2008 6:13:15 PM EDT
btt
Link Posted: 8/31/2008 3:24:13 PM EDT
Link Posted: 8/31/2008 4:14:23 PM EDT
[Last Edit: 8/31/2008 4:19:11 PM EDT by FIGJAM]
The six at the top are 62 grain Barnes Triple Shocks behind 19.6 grains of Reloader 7 at whopping  1970fps at the muzzle from my 7.5" pistol.  They entered a 5 gallon plastic bucket with highly compressed wet newspaper at 30 yards and penetrated approximately 10.5" and fully petaled to ~45 caliber.  I'm not happy with Reloader 7, though, with these bullets so I'm going with something else to get the velocity up; but believe me, you wouldn't want to get hit with one.  

The other two bullets are 62 grain SS109 traveling the same distance but with a muzzle velocity of 2,300fps.  They penetrated through the first plastic bucket and made it about 2" into the second bucket but keyholed approximately 3/4 through the first and entered the second bucket sideways.  

Link Posted: 9/1/2008 10:28:13 AM EDT
Nice figjam. I just got my reloading press and will be doing some load development also from my 7.5 pistol. when i get my cutter in, ill start, ill probably get a lil reloader7 and try the 53 grain barnes, the varget looks interesting, but it seems like quickload is right, it would be way too much for a 223.
Link Posted: 9/1/2008 10:57:17 AM EDT
FIGGAM,

Very interesting. Since I do not reload, can you recommend a factory made 'personal defense' ammo?

When I Googled a bit I came up with ‘Hornady TAP Personal Defense’.
Link Posted: 9/1/2008 11:13:47 AM EDT
Absolutely.  It's pricey but you won't find any better for a pistol.  They sell the 53 grain stuff, too.  Both would be devastating.

www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=467277
Link Posted: 9/1/2008 11:33:25 AM EDT

Originally Posted By deuc224:
Nice figjam. I just got my reloading press and will be doing some load development also from my 7.5 pistol. when i get my cutter in, ill start, ill probably get a lil reloader7 and try the 53 grain barnes, the varget looks interesting, but it seems like quickload is right, it would be way too much for a 223.


I'm gonna give Varget a try, probably this afternoon.  
Link Posted: 9/1/2008 5:12:47 PM EDT
[Last Edit: 9/3/2008 9:40:47 AM EDT by FIGJAM]
Well, Varget is a not a good powder.  I went ahead and got it up to 25.5gr but still only 2,090fps; seemed like a pretty hot load, too.  Shot some M855 as a control and got 2,350fps.  Varget just burns too slow for such a short barrel.  I'll get it figured out eventually.
Link Posted: 9/2/2008 5:18:04 PM EDT
[Last Edit: 9/2/2008 5:22:43 PM EDT by popnfresh]
Are you taking requests FIGJAM? How about AA1680, ever tried it?  I'm thinking of switching to 1680 when I run out of 2230.

ETA: I'm after bang for buck with flawless function.
Link Posted: 9/2/2008 5:51:39 PM EDT
How about IMR 4198?  Fast burning and made for .223.


Hodgdon data:
53 GR. SIE HP   IMR 4198  .224"  2.200"  19.0  2972  43,800 PSI  21.4  3268  48,200 PSI  
Link Posted: 9/2/2008 6:07:25 PM EDT
I posted some info on short barrel velocity here.
Link Posted: 9/3/2008 9:40:29 AM EDT
[Last Edit: 9/3/2008 9:43:59 AM EDT by FIGJAM]
Thanks for the encouragement all.  Next up is Winchester 748.  I've been doing some reading and from all accounts Winchester 748 or Hodgdon BLC-2 are the closest to Lake City powder.  I plan on pulling a few M855's to see what the powder looks like in them and what weight.  I'm also tempted to just replace some of the SS109 with some TSX  to see how they react (reducing the military load, of course, and working up).
Link Posted: 9/4/2008 6:58:13 PM EDT
height=8
Originally Posted By FIGJAM:
Next up is Winchester 748.  


Both the powders mentioned are slower powder than Varget.  Wouldn't you want to go to a faster burning powder for the short barrel?

Here is the chart I have been referring to:
http://www.hodgdon.com/burn-rate.html
Link Posted: 9/5/2008 2:57:50 AM EDT
[Last Edit: 9/5/2008 9:20:51 AM EDT by FIGJAM]
Here ya go.

Burn Rate Chart

Reloader 7 is about as quick a powder as one can go with 223.  Actually there are a couple quicker but neither are obtainable without difficulty.  Unfortunately, once you reach a powder burn threshold in combination with certain bullet construction, you run into a phenomenon of pressure spikes.  You reach points where tiny increments of powder produce very little velocity change but these pressure spikes reach dangerous points.  The trick is finding a powder which burns quick enough without producing pressure spikes.  One can see this occur by slowly monitoring velocity changes as incremental charge weight increases.  At some point, there becomes a diminishing return and case web expansion becomes noticeable (over factory expansion).  We are talking about only .0003-.0004" here and ideally you want no web expansion.  I reached .0003" in my Reloader 7 loads and wasn't getting much return at that point so not much point in pushing it further.  

There seems to be a discrepancy between our two charts.  The reason I chose 748 is that it's very easy to obtain locally and it's what's supposed to be in M855 (or something that's close to 748 or BLC-2).
Link Posted: 9/5/2008 11:33:16 AM EDT
Pressure spikes would be shown in the CUP pressure-correct?

Most of my reloading has been simple .308 stuff (mimicing M118LR) and .40 bunny fart loads.

On the Hodgdon site they don't list the winchester powder for .223 as a minimum.  What can I look for to see what is useable in .223 besides the chart below?

data.hodgdon.com/cartridge_load.asp

I am doing a pistol build right now, just waiting on parts.  I will try some additional combinations when mine is up and running.
Link Posted: 9/5/2008 1:12:00 PM EDT
[Last Edit: 9/6/2008 9:13:20 AM EDT by FIGJAM]
I use loading software which is a program from Germany.  It utilizes several different methods of establishing pressure, but generally it's in PSI.  The pressure measurements are CIP, SAAMI, and EPVAT Casemouth (NATO measurement point).  In any case, I do not have the equipment to measure actual pressure.  I can only see it's effects on the cases.  Here's some max. loads from the software.  You can see which powders burn quickest by how much they are consumed at the end of the barrel which is 7.5".  

Loads for 5.56x45, 62gr TSX

Software load's maximums are based on 55,000 psi for 223 and 58,740 psi for the 5.56x45 chamber.

Regarding pressures of .223 vs 5.56 from Wikipedia:

"5.56 mm NATO versus .223 Remington

While the 5.56 mm and .223 cartridges are very similar, they are not identical. Military cases are generally made from thicker brass than commercial cases; this reduces the powder capacity (an important consideration for handloaders[1]), and the NATO specification allows a higher chamber pressure. Test barrels made for 5.56 mm NATO measure chamber pressure at a the case mouth, as opposed to the SAAMI location. This difference accounts for upwards of 20,000 psi (140 MPa) difference in pressure measurements. That means that advertised pressure of 58,000 psi (400 MPa) for 5.56 mm NATO, is around 78,000 psi (540 MPa) tested in .223 Rem test barrels. The 5.56 mm chambering, known as a NATO or mil-spec chambers, have a longer leade, which is the distance between the mouth of the cartridge and the point at which the rifling engages the bullet. The .223 chambering, known as SAAMI chamber, is allowed to have a shorter leade, and is only required to be proof tested to the lower SAAMI chamber pressure. To address these issues, various proprietary chambers exist, such as the Wylde chamber (Rock River Arms)[2] or the Armalite chamber, which are designed to handle both 5.56 mm and .223 equally well.

Using commercial .223 cartridges in a 5.56-chambered rifle should work reliably, but generally will not be as accurate as when fired from a .223-chambered gun due to the longer leade.[3] Using 5.56 mil-spec cartridges (such as the M855) in a .223-chambered rifle can lead to excessive wear and stress on the rifle and even be unsafe, and the SAAMI recommends against the practice.[4] Some commercial rifles marked as ".223 Remington" are in fact suited for 5.56 mm, such as many commercial AR-15 variants and the Ruger Mini-14, but the manufacturer should always be consulted to verify that this is acceptable before attempting it, and signs of excessive pressure (such as flattening or gas staining of the primers) should be looked for in the initial testing with 5.56 mm ammunition.[5]"
Link Posted: 10/17/2008 6:14:00 PM EDT
[Last Edit: 10/17/2008 6:18:14 PM EDT by popnfresh]
Just to add some data..... I just ran a hundred test loads across my chrony mainly to test for function in my pistol(7.5" DPMS kittyKat Barrel). I am using 55gr Hornady FMJBT, S&B, Remington, and LC brass trimmed to 1.750", 23.4 grains of AA2230, 2.230" COL, with an average velocity of 2137fps and 558fpe.  

According to AA it should be 2604 out of a 14 inch barrel, which I would assume is out of a single shot. I"lll have to run them through my 16" another day and update.
Link Posted: 10/18/2008 5:46:14 AM EDT

Originally Posted By popnfresh:
Just to add some data..... I just ran a hundred test loads across my chrony mainly to test for function in my pistol(7.5" DPMS kittyKat Barrel). I am using 55gr Hornady FMJBT, S&B, Remington, and LC brass trimmed to 1.750", 23.4 grains of AA2230, 2.230" COL, with an average velocity of 2137fps and 558fpe.  

According to AA it should be 2604 out of a 14 inch barrel, which I would assume is out of a single shot. I"lll have to run them through my 16" another day and update.


2137 fps and nearly 560 ft lbs...not bad...  It's actually higher than I would've thought
Link Posted: 11/21/2008 3:40:41 PM EDT
I thought I would add some info, this is a copy and paste from another thread.



Went to the range today to check the difference in muzzle velocities between my 7.5" pistol and my 16" rifle. Both barrels are DPMS 1-9 twist.

For reloaders the temp was 75 degrees, no wind, 30% humidity, 30.36 bar press., approx. 20' above sea level.

The loads were all with AA#2230, the bullets were Hornady 55gr fmjbt and very rough, machine pulled 62 gr fmjscbt. Mixed brass trimmed to 1.750", COAL of 2.230",WSR primers.

The guns:  PISTOL 7.5" DPMS Kittykat bbl, lower, and LPK, RRA upper, stag BCG
RIFLE 16" DPMS HBAR all DPMS parts built in '96.



All shots fired at 25 yards, 20 shots per target.


First load, 22.8 grains of AA2230 with 62grain fmjscbt.

Pistol ave. of the two 10 shot strings was 2068fps



Rifle ave. of the two 10 shot strings was 2633fps



A 565fps difference between the two bbl lengths.











The second load was with Hornady 55gr fmjbt with 23.5gr. of 2230.

The pistol ave. of the two 10 shot strings was 2120fps


The rifle ave. of the two 10 shot strings was 2778fps



A 658fps difference between the two bbl lengths.




On a side note, the 2230 for the 55gr. bullet loads is from 1999, the 2230 for the 62gr loads is from 2008 that may explain the the large extreme spreads of the 55gr. loads or maybe the guns like the 62gr bullets more.???









Link Posted: 11/21/2008 10:17:43 PM EDT
[Last Edit: 11/21/2008 10:25:14 PM EDT by adam731432]
Allot of people that reload cast lead bullets in rifles that you can only push too 1700-2200 before you get bad leading have good results with faster burning pistol and shotgun powders. You might have to step up to a heavier bullet to get enough umpfh to cycle the bolt. Im under the impression that the heavier 63-69-70-75-77g bullets perform better out of shorter barrels because they tumble and fragment at lower speeds than the 55g fodder. At least in a 10.5-14" SBR. At least the longer bullets will yaw creating a 1/2" wide wound cavity. I would ask about powders on thehighroad reloading forum and possibly castboolits.

Would shooting 69-77g out of a 1/9twist shorter barrel make the bullet less stable and cause more damage when it yaws on impact?
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