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Old October 13, 2012, 03:40 PM   #1
iraiam
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Duplicated crimped in primer

I developed a way to easily duplicate the military crimped primer on a Rock Chucker.

The problem is I have a bunch of books and very little load data that would duplicate the bullet velocities in 5.56X45. I don't have the equipment to develop my own recipies.

I have seen some data on surplus powder from disassembled military ammunition, but not officially published, so I am hesitant to even try it. Other than that, virtually all my load data is for .223 rem, a few 5.56X45 but velocities are not what they could be.

Anyone have any ideas on where to get some real data for 5.56 loads
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Old October 13, 2012, 04:21 PM   #2
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You always want to work up loads in your gun to a velocity that gives you best precision and no pressure signs. Since, in real world hunting and, obviously in target shooting, precision of the load (the ability to hit the same place each time) is what allows you to set the sights for accurate shot placement, precision is more important to successful shooting than even a hundred fps one way or the other.

Out of curiosity, why did you want to reproduce the primer crimp? The military added those to prevent machine gun jambs due to a loose primer falling down into the gun mechanism during extraction and causing a jam. Unless you are you shooting a full auto weapon in a combat situation where you don't have time to disassemble it to clear it, crimping just makes the next reload more difficult to do, as you have to remove the crimp to get the next primer in, then form the crimp again. Doing that every time will also shorten brass reloading life considerably.

Regarding warmer load information, you can look at load data from most European sources (Vihtavuori, Norma) as, unlike the U.S., they don't distinguish between the two as far as pressure and velocity goes. Just realize their data will only be for their powders. For U.S. powders, you really need to do the workups in your guns while watching for pressure signs. Beyond that, we'd need to see the details of what you are loading with (bullet, case, primer) and what kind of gun it's for.
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Old October 13, 2012, 04:28 PM   #3
mikld
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Jes a question, why do you want to crimp in your primers? I would think 5.56 load data is redily available, check powder mfgs on line. I would think .223 data would work...

http://data.hodgdon.com/cartridge_load.asp
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Old October 13, 2012, 04:29 PM   #4
Marco Califo
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Why this title for thread?

Why this title for thread? You don't explain the crimp, and then go off in a different unrelated direction.

Back to what you indicated the topic was: "Why would you want to add a military primer crimp?" There is no need for one.
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Old October 13, 2012, 04:48 PM   #5
iraiam
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Quote:
Why this title for thread? You don't explain the crimp, and then go off in a different unrelated direction.
The crimp is not explained because I built a relatively simple device in my basement machine shop that threads into a reloading press, allowing a primer to be crimped in, that's about all I have to say about that.

A need for a crimped in primer or not, I have the ability to do it, if an explanation is needed, then you can think one up I guess.

I have several accurate long standing .223 recipies that have been worked up to or very near published maximum, that's what I'm using now. The last batch of XM855 I bought is accurate and faster.
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Old October 13, 2012, 06:20 PM   #6
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Most of us do what we can to avoid or get rid of crimps to make loading easier and make brass life longer. That's why you are getting that question from us. You may have made the tool on the assumption it was a good idea because the military does it, and for full auto class III weapons, it can be a good idea. The military adopted the practice of crimping in the 1920's because of the trouble they'd had with primers falling out and getting into machine guns and jamming them. But they don't crimp primers on their match ammunition. They still apply primer sealant for harsh conditions, but no crimp in the match cases. So, for the rest of loading and shooting, a crimp is a nuisance rather than a help.

CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.

Since we still don't know what bullet, primer, or powder or what kind of gun you are using, the only generalization I can offer is that when using the exact same case, bullet, and primer, it typically takes about a 4% increase in powder charge to go from SAAMI maximum pressure to NATO and CIP maximum pressures in this cartridge. A 4% increase in a maximum powder charge will raise the peak pressure about 12%, which is what the difference in those two specifications amounts to.

So if you take American load data for .223 Remington and multiply it by 1.04, you will be in the ballpark of the 5.56 NATO equivalent. Use caution, though, especially if the loads are compressed, as that may make pressure rise more than you expect from a 4% charge increase expected. Also use extra caution if you aren't using the exact same primer that was used in the load data. Going from a Federal 105 primer to a Remington 7½ can raise velocity 150 fps, as Charles Petty demonstrated in a 2006 article in Handloader, but it raises pressure around 30% at the same time. So you have to work up with your components while watching for pressure signs, and not trust the data blindly.

In most .223 loads that 4% charge increase will represent around 1 grain of extra powder, but I would divide that roughly into thirds, working the load up in three steps, checking at each increase both for pressure signs and for accuracy. If you get too much pressure and velocity, accuracy will go back down again, anyway.

Two more things to keep in mind:

Shooting at over about 58,000 psi will increase throat wear and shorten barrel life. That's half way between a SAAMI and NATO maximum. It is why military barrels are chrome lined. If your's are not, try to limit yourself to a 2% charge increase if you shoot the gun much unless you want to replace the barrel more often.

Finally, if your original handloads had poor accuracy, be aware that velocity and pressure aren't the only factors. Some bullets are easier to load for accuracy than others. You want the right type and lentgh and weight of bullet married to the right barrel twist rate.

Good luck and be careful out there.
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Last edited by Unclenick; October 13, 2012 at 06:26 PM.
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Old October 13, 2012, 06:44 PM   #7
JT-AR-MG42
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'Cartridges of the World' is a DBI? publication.

Updated every few years I think.

They have a chapter that shows current - as well as past - specs and weight tolerances of components used in addition to powder type and charge weight for all military cartridges 9mm thru 30mm.
Chronographed velocities are also shown.

That chapter, of course, includes the crimped primer 855s.

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Old October 13, 2012, 07:45 PM   #8
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"A need for a crimped in primer or not, I have the ability to do it, if an explanation is needed, then you can think one up I guess."

I accept that but I can't "think one up" because I don't care.

Think up your own 5.56 "recipies".
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Old October 14, 2012, 07:34 AM   #9
iraiam
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Thanks

Quote:
'Cartridges of the World' is a DBI? publication.

Updated every few years I think.
Thanks, got a copy coming. I could swear I know the authors name from somewhere (Frank C. Barnes)
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