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Old November 18, 2012, 10:31 AM   #1
My Toy
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Loading data for 5.56 NATO

There is tons of loading data for 223 Rem but if you wanted to reproduce the ballistics of XM193 or M855 within safe margins is there any reputable source of data?
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Old November 18, 2012, 10:56 AM   #2
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All these should do it:
NOTE 1: Anything over 106% case fill begins to be impractical. 107% is starting to compress
NOTE 2: Recommended combos are in green

DON'T START AT THESE LOADS
Approach with caution !!!!



Last edited by mehavey; November 18, 2012 at 11:42 AM.
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Old November 18, 2012, 10:58 AM   #3
steve4102
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62,000 psi 5.56 data can be found at Ramshot and Accurate.

http://www.ramshot.com/wp-content/up...dgun_rifle.pdf

http://www.accuratepowder.com/wp-con...d_data_3.5.pdf
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Old November 18, 2012, 11:17 AM   #4
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Steve4102 and mehavey thanks for the info; the great thing about FL forum is ask and ye shall find out. Thanks again.
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Old November 18, 2012, 11:22 AM   #5
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The 62k NATO pressure is widely misunderstood, and highly dependent upon chamber design. See below:

http://www.m4carbine.net/showthread.php?t=55149

All things being equal, I'd recommend 55K max for no other reason than pressures above
that (from my experience) begin to stress primer pockets after a few (5-6) firings.
Besides (as noted in the previous post) it isn't needed to reach military-matching ballistics.)

Last edited by mehavey; November 18, 2012 at 11:41 AM.
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Old November 18, 2012, 12:42 PM   #6
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The Real Deal

Here is the US Military Tech Manual on small arms ammunition specs. You will also need CCI#41 mil-spec primers, and WC844 (AKA H335) military surplus powder (available at Wideners.com (sometimes) and GIBrass.com (AKA Bartelett Reloaders).

See page 154:
"Propellant:
Type ...............................WC 844 or
CMR 170
Weight .............................28.5 or 26.5 gr
Projectile:
Weight .............................56 gr
Performance:
Chamber pressure...............52,000 psi
Velocity ..............................3250 fps, 15 ft from"
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File Type: pdf TM43-0001-27new.pdf (1.53 MB, 30 views)
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Old November 18, 2012, 01:23 PM   #7
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Note the chamber pressure stated in post 6 for this thread, "52,000 psi" is the military's (and many commercial companies still do that today) way of stating the pressure measured by the old copper units of pressure system. It is the same as SAAMI specs using the same system for the .223 Rem. which is 52,000 CUP; cheers for SAAMI using the correct pressure unit term. All the different 5.56 NATO live ammo with bullets spec for pressure runs from 50,250 cup to 55,000 cup, but the MIL SPEC documents state it in "psi" terms. Shame, shame, shame on all of them not using correct terms for confusing so many folks!!!!!!

SAAMI also lists peak pressure for the .223 Rem. using an electronic transducer measuring actual physical pressure force on the chamber wall which is 55,000 pounds per square inch; "psi."

Could someone please cite me a MIL SPEC document's web page that states peak pressure for any 5.56 NATO round at 62,000 psi based on peizo, strain gauge or transducer measuring system! I cannot find one anywhere.

===========================================

My Toy, it's a waste of time to try everything to duplicate the ballistics of a given cartridge in any rifle you own. Close is good enough. Unless your barrel and firing mechanics have the same dimensional and force specs and your ammo's loaded with the same lot of cases, primers, powder and bullet, then gets assembled to the same dimensions with the same neck tension producing the same release force needed to get the bullet moving. you'll spend a fortune trying.

No match winning and record setting competitor ever tries to duplicate someone elses load ballistics. Their stuff is different. And who knows; your load that's 22 fps slower than your dream load may well be twice as accurate.

Different lots of commercial centerfire match ammo for both rifle and pistol may well shoot equally accurate across them, but no two will have the same muzzle velocity. Even military M118 and M152 7.62 NATO match ammo has a 60 fps spread in acceptable muzzle velocity around 2550 fps measured at 26 yards from the muzzle.

Go figure all this out. Then go do well with whatever you chose.

Last edited by Bart B.; November 18, 2012 at 02:04 PM.
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Old November 18, 2012, 06:39 PM   #8
Marco Califo
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Not military, but Accurate's Reloading guide includes a section titled: "<62350Psi Appliocation: Bolt Action Rifles and Semi Auto Weapons rated for the latest NATO/MIL ammunition."

As to the TM being wrong, I am not convinced.

While PSI and CUP move in the same direction, the relationship is not linear, nor "equivalent-able". Otherwise we would have a nice table to show just that. I looked at the http://data.hodgdon.com/cartridge_load.asp and noticed that in the case of 223 and 55 grn bullets, all of the loads they listed for 335, 4895 and Varget (which covered 3 different bullets for each powder) included at least one in CUP and at least one in PSI. My point is that the difference between PSI and CUP at this data point is less than 5%. On the other hand, the difference you are talking about, I think, is the difference between Hodgdon's 50K PSI and CUP loads, and, Accurate's 62.35K PSI, in Accurate's last loading data bracket. I believe a large part of that disparity is due to the longer & heavier 62 gr 855/SS109 and other heavy long bullets they list there, are in fact, loaded to the higher pressures. This is supported by that same TM listing this for M855:
Chamber pressure ..............55,000 psi
Velocity ..............................3025 fps, 78 ft from
muzzle
Conclusion: IMO the TM correctly states pressures in PSI as it printed. Coincidentally, there does not seem to be a significant difference (>5%) between PSI and CUP in 223 with 55 grn bullets using the same powder. However, in other calibers and/or bullet weights that difference may be significant.
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Old November 18, 2012, 07:00 PM   #9
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Quote:
Conclusion: IMO the TM correctly states pressures in PSI as it printed. Coincidentally,
there does not seem to be a significant difference (>5%) between PSI and CUP in 223 with 55 grn
bullets using the same powder. However, in other calibers and/or bullet weights that difference may
be significant.
FWIW:

SAAMI standards are
52,000 CUP for all four bullet weights (53, 55, 60, and 65gr)
corresponding to their same 55,000 psi standard for the same four bullets.

(See SAAMI Stds page 14 & 19)

NOTE ALSO that SAAMI and C.I.P./NATO (not CUP) give you different pressure numbers for the same cartridge tested side-by-side:

Under C.I.P. proof test standards a drilled case is used and the piezo measuring device (transducer) will be positioned at a distance of 25 millimetres (0.98 in) from the breech face when the length of the cartridge case permits that, including limits. When the length of the cartridge case is too short, pressure measurement will take place at a cartridge specific defined shorter distance from the breech face depending on the dimensions of the case.

Under SAAMI proof test procedures, for bottlenecked cases the centre of the transducer is located 0.175 inches (4.4 mm) behind the shoulder of the case for large diameter (0.250 inches (6.4 mm)) transducers and 0.150 inches (3.8 mm) for small diameter (0.194 inches (4.9 mm)) transducers. For straight cases the centre of the transducer is located one-half of the transducer diameter plus 0.005 inches (0.13 mm) behind the base of the seated bullet. Small transducers are used when the case diameter at the point of measurement is less than 0.35 inches (8.9 mm).

The difference in the location of the pressure measurement gives different results than the SAAMI standard.


See Proof Test Differences

BOTTOM LINE: Don't sweat attaining "NATO" pressures and ballistics. You're already there.

Last edited by mehavey; November 18, 2012 at 07:16 PM.
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Old November 18, 2012, 09:58 PM   #10
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Marco, wanna see some interesting stuff?

Check out the .308 Win. max average pressure numbers in the following SAAMI document.

http://www.saami.org/specifications_...wnload/206.pdf

Then check out the 7.62mm NATO max average pressure numbers in this military document:

http://www.everyspec.com/ARMY/TM-Tec...27_CHG-2_4432/

Compare the numbers and terms for pressure.

Then do the same thing with the .223 Rem. in the SAAMI one and the 5.56 NATO one in the military one.
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Old November 19, 2012, 08:12 AM   #11
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Thanks for pointing that out Bart.
Yes, the military 5.56 and the 7.62 are in CUP not psi. Some dumb ass in the military erroneously listed psi on official TM and has caused mass confusion ever since.

UncleNick had a great explanation of this awhile back.
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Old November 19, 2012, 07:40 PM   #12
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Steve, commercial ammo makers used psi instead of cup decade ago; long before any military specs were made public.
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Old November 19, 2012, 09:16 PM   #13
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Here is part of UncleNicks explanation, sorry no link just saved text.

If you look through military ammo specs from before the mid-90's, you find military copper crusher numbers reported as "psi" at the same time a commercial maker would have reported them as "CUP" (I don't know why "CUP" gets caps while "psi" gets lower case, but that's how SAAMI publishes them). The SAAMI conformal piezo spec is 62,000 psi MAP (Maximum Average Pressure). I'll have to check, but I recall SAAMI MAP allows up to 4% deviation from average, so 64,480 psi would be the allowed extreme spread in SAAMI compliant ammo.

The NATO allies use 415 MPa, which the CIP uses for both 7.62 NATO and .308 Winchester. That converts to 60,191 psi, but the CIP measuring system sets the sample point further forward in the case, so it sees a bit of the pressure drop at the bullet base that occurs when the bullet starts moving. That makes them tend to read about 2,000 psi lower than the SAAMI setup does in this pressure range. So the same ammo would measure closer to 62,000 psi in SAAMI equipment.
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Old November 19, 2012, 10:03 PM   #14
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Quote:
SAAMI conformal piezo spec is 62,000 psi MAP (Maximum Ave pressure) etc etc...
I'm confused.

I'm sitting here looking at the actual SAAMI manual and it clearly lists MAP/223Rem as:

52,000 CUP (page 14)
55,000 psi (page 19)

nowhere is 62,000 anything listed.

American Rifleman notes just recently:

> Manufacturers load .223 Rem. to 55,000 psi, as established by SAAMI
> (Sporting Arms & Ammunition Institute). The maximum average pressure for the
> 5.56 NATO is about 61,600 psi, as established by the U.S. Military.
> This is 11 percent more than .223 Rem. pressures. Because the 5.56
> NATO is a military cartridge, SAAMI hasn’t set pressure limits for it.
> This is why all handloading data published conforms to SAAMI .223 Rem
> pressure limits.
http://www.americanrifleman.org/arti...ton-specifics/

Am I misreading (or missing) something?

Last edited by mehavey; November 19, 2012 at 10:09 PM.
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Old November 19, 2012, 11:05 PM   #15
Marco Califo
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Where is this proven?

Quote:
Yes, the military 5.56 and the 7.62 are in CUP not psi. Some dumb ass in the military erroneously listed psi on official TM and has caused mass confusion ever since.
I would really like to read the source evidence that the mil-spec manuals are wrong: that they published 52,000 and 55,000 psi but meant 52,000 and 55,000 CUP, and someone please quantify the amount and direction of the error as psi or CUP.
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Old November 20, 2012, 12:02 AM   #16
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Marco, you can get the information straight from the horse's mouth. Call Lake City Army Ammo Plant in Lake City, Missouri then ask them when the switched from copper crusher gage systems to peizo or transducer ones. Then ask them why the specs state one way and they did the other.

Mehavey, 55,000 cup is about the same as 62,000 psi in 22 caliber bores the way military systems spec'd the way it's measured.

And yes, the entire world of printed pages on this is typically contaminated with misinformation. It ain't all the fault of the writer. It's the lackadaisical way the language and terms were used between the ballistic engineer who did the pressure testing and all those between that person and the likes of you guys and me.

After a discussion of CUP and PSI with a ballistics engineer at the Lake City Army Ammo Plant in the early 1970 I pretty well understood all of this, but I sometimes misuse/mix-up the terms myself. It wasn't really a problem until the 7.62 NATO round hit the military streets and the .308 Win. round hit the civilian ones. Prior to that everyone pretty much talked PSI and the pressure tests were all made with CUP systems. About the time the .308 Win. came out, piezo and transducer pressure systems were starting to be used. Their PSI numbers with the same load specs and test barrel specs were higher than the CUP numbers. And the rest is history, a confusing history at that.

Last edited by Bart B.; November 20, 2012 at 12:23 AM.
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Old November 20, 2012, 09:20 AM   #17
mehavey
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OK, now I am confused:

I know what the SAAMI actual test specs are for

The 5.56:
52,000 CUP (page 14)
55,000 psi (page 19)

The 308Win:
52,000 CUP (page 16)
62,000 psi (page 21)

Has ANYone done SAAMI-geometry* pressure (psi) tests on NATO-spec ammunition?
Until then, we're comparing apples and oranges when we quote presure specs.


*(Not C.I.P. geometry. See Post#9 above)

Last edited by mehavey; November 20, 2012 at 09:36 AM.
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Old November 20, 2012, 10:08 AM   #18
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mehavey, some years ago a friend ran tests on a rifle chambered for the .308 Win. Its barrel had a SAAMI spec chamber and bore/groove dimensions were very close to SAAMI specs. He used an Oehler System 43 strain gauge pressure and screened velocity measuring system. His strain gauge epoxied across the barrel about mid point on the chamber showed different factory .308 ammo and 7.62 NATO ammo had average pressure all within a 4,000 psi spread around 61,000 psi or thereabouts. The NATO ammo was a bit higher than the commercial stuff probably 'cause it had fatter bullets; as I remember what he told me.

But there is a little bit of apples vs. oranges stuff when different measuring locatiions are used relative to the cartridge case in the chamber across different test barrels. Not enough to matter much.
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Old November 20, 2012, 10:11 AM   #19
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That works for me.
Many thanks.
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Old November 20, 2012, 12:11 PM   #20
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I should note that when I wrote what Steve quoted, I was speaking of 7.62/.308, not 5.56 mm. I also note I made an error in what he quoted. I said the CIP was measuring further forward in the case, but it is NATO that does that. The CIP uses 25 mm forward of the breech, as described earlier.

The most comprehensive explanation of the unit discrepancy was written by board member FALPhil. It seems the military labs were using CUP but the manual editors changed it to psi for reasons unknown. Possibly they didn't know what a CUP was and thought they were making an appropriate correction.

The CIP puts the .223 Remington peak pressure limit at 3700 Bar (53,664 CUP) by copper crusher method, and 4300 Bar (62,366 psi) by Piezo transducer method (see page 68, here). Hartmut Broemel's data in QuickLOAD for the 5.56×45 NATO has the same number. For an interesting discussion of pressure measuring read this thread at the 24 hr. Campfirefor all the discourse between Denton Bramwell, Ken Oehler, and Hartmut Broemel as they discuss the matter and on some points disagree. One thing you'll learn is that Broemel writes the CIP's software and has access to more comparative pressure data than anybody else, so I expect the number he gives for the 5.56 NATO round is accurate by their measurement method for 5.56 NATO reference ammo.

So, this all begs the question, why would SAAMI and U.S. Military pressure numbers for CUP and psi differ so little, where the CIP has numbers differing so much more? Well, SAAMI seems simply to have copied the military numbers. No mystery there. As to the CIP and NATO having higher numbers than the U.S. Military, I don't have a good answer for that, but can speculate on a possible cause. The original reference loads would all have been developed on a copper crusher. The reference loads used by the U.S. and those used by NATO to determine Piezo numbers could have been different lots and therefore had different absolute pressure values because the copper crusher is so variable.

Below are the two samples of pressure measurement test data provided by SAAMI in their rifle and pistol documents. The upper numbers are for nine labs measuring the same lot of .30 Carbine reference ammo in copper crushers. The lower numbers are for seven labs measuring the same lot of .357 Magnum reference ammo using Piezo transducers. What jumps out is just how much more variance copper crusher pressure numbers have—over twice that of the Piezo transducers as a percentage of the average reading. Note also the two percentages with no column label on the right edge of the image. These are the percent the average standard deviation in pressure is of the average pressure. These numbers are about the same, indicating the consistency of the two different lots of reference loads were likely about the same. That means reference load inconsistency isn't accounting for how much worse the copper crusher consistency is. Clearly, one reference lot could be loaded 20% higher in pressure than another if different copper crusher units and different technicians did the charge determination.

Attached Images
File Type: gif CUP variance v psi variance.gif (27.9 KB, 58 views)
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