Question about .223 and overpressure

[RNG]

Greetings once again.

I have a new AR .223 with a Bushmaster 16" upper. Been reloading pistol for a while and decided to start reloading for the AR. While working up a load I'm finding that even at the minimum powder charge I'm getting what looks like flattened primers. Any "opinions" would be appreciated.

Cheers,
Richard

My Specs:
.223
AA2460
16”
Bushmaster AR-15 HBar
Winchester 55 grain FMJBT
CCI 450 Magnum Small Rifle Primers
Mixed Brass

From the AA Ballistician ;
****************************************
Richard,
We suggest between 23.4grains and 26.0 grains

Regards
Johan Loubser
Ballistician
Ramshot/Accurate Powders
Tel: (406) 234 04 22 email: [email protected]
Western Powders Inc -- Miles City – Montana

****************************************

I've tried 23.7, 24.0, & 25.0 all with the same basic result.

 

[Galil5.56]

I'm not seeing any problems, and have used the exact same combo you are with a higher charge weight with no problems out of a Galil ARM. I did chrono some loads about 14 years ago, and could get M193 performance with no problems concerning pressure.


Been touting AA2460 for .223 for a very long time and really like it in other calibers too, especially .308 and 303 British.

 

[NCsmitty]

I see no obvious "cratering" around the firing pin indent. Things look normal. Measure the case above the extractor groove before and after firing with a vernier, if you have one. A measurement of .001-.002 increase is completely normal. Anything over .003 is indicating a max or overmax pressure situation. The AA site lists 25.4 as the max load for a 55 gr. bullet. Anything under the 25 gr load that gives you the best accuracy would be my choice. I would separate my brass as to manufacturer to achieve more consistency.

NCsmitty

 

[stubbicatt]

Don't know why you are using magnum primers, but OK. The area of flattening you are looking for is at the radius of the primer. In essence look at the edge of the primer. If it is rounded over at all and you are using a recipe from a reputable source, you are likely ok.

Another method of verifying pressure that I like is to gage the growth at the web on factory loads like Federal or Winchester, or whatever brand of brass you reload, and compare that to your loads fired in virgin brass. If the web area hasn't grown any more than that of the factory ammo, and your primers look ok, you are in safe territory.

YMMV.

 

[steve4102]

They look fine to me. Now this is what a flat primer looks like.

 

[moooose102]

i agree, you should not be using magnum primes with this combination. i have been told that what sometimes happens with magnum primers and standard powder is it can cause instant ignition of all the powder at once instead of a controled burn. that alone could cause your over pressure situation. now, the case on the right looks fine, the one in the center looks like it is getting there, and the one on the left looks a bit hot. get rid of the magnum primers (you dont have a 223 magnum do you?!) and try that. also, +1 on measuring the o.d. of the bottom of the case. it is about as accurate as you can get for pressure indication as a handloader. steve4102, that is not a flattened primer, that was what was left from a SERIOUSLY OVERPRESSURE EXPLOSION! good luck!

 

[RNG]

I can't thank everyone enough for the quick replies and great info. I was worried that I was screwing up.

As for the magnum primers, we don't have any places that sell reloading supplies locally or even within more than 100 miles. I had a friend pick a few things up for me while he was at Sportsmans Warehouse and they gave him the CCI 450's instead of the 400's so I decided to use them.

Thanks again for a great site.

Kindest Regards,
Richard

 

[RNG]

agree, you should not be using magnum primes with this combination.

Moose...
I considered not using them for the AR but saw that my friends Lymans 47th had load data using the 450's. My Lymans 48th only shows data using Rem 7.5's, that's why I emailed the folks at AA for their recommendations.

Thanks again.
Cheers,
Richard

 

[steve4102]

steve4102, that is not a flattened primer, that was what was left from a SERIOUSLY OVERPRESSURE EXPLOSION! good luck!

I know, I was just messin with you guys. I think I copied this from Steve's site.

 

[1911user]

Magnum primers are NOT a problem and often recommended for ball powder rifle loads. One does not require a 223 MAGNUM to use magnum rifle primers. The CCI mil-spec #41 primers are MAGNUM primers (AKA CCI450) with the anvil slightly farther away from the cup to be less sensitive. In colder conditions, MAGNUM primers are more consistent in igniting the commonly-used ball type powders which, coincidentally, is what the military uses for 223 ammo. Just don't develop a maximum load then start changing components without working up the load again.

RNG, you're doing just fine. Those primers are not showing overpressure. Keep using the 450 primers, they're a good choice.

 

[RNG]

The CCI mil-spec #41 primers are MAGNUM primers (AKA CCI450)

Great information. Jeeze, I love this site.

1911.. Thanks for the input.

And thanks again to all who contributed.

Hope ya'll have a safe and Happy 4th of July.

GOD BLESS AMERICA and our Troops.

"Semper Fi"

Richard

 

[snuffy]

Those cases are NOT showing pressure signs. But then, reading pressure from primer appearance is iffy at best downright misleading at worst.

As said, case head expansion is better, BUT you need a micrometer capable of reading .0001. That's one ten thousandths. A common caliper/micrometer is only capable of reading to .001, one thousandths. Then, you have to know where to take that ultra precise measurement, and develope a "feel" for when you're putting too much torque on the barrel of the mic.

 

[rcmodel]

Generally speaking, in an AR, you will start seeing loose primers and a round mark on the case head where it flowed into the ejector hole in the bolt enough to make a shiny spot when the bolt unlocked.

When you see those two signs, you for sure have reached maximum pressure.

Keep going, and bad things will happen shortly.

rcmodel

 

[Clark]

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

This is a .223 case that was fired in one of my AR15s.
Over pressure can be seen in 4 places:
1) The case head has started to separate from the web.
2) The shape of the extractor can be seen on the rim and case head.
3) The shape of the ejector relief in the bolt face can be seen on the case head.
4) The primer has cratered back up into the firing pin hole.
The load was 18 gr Blue Dot, and 35 gr Vmax moly that really weigh 33 gr.
Sometimes this load is tame, and does 4025 fps from 26", but some rounds will do 4125 fps and have horrible pressure sign. Blue Dot is not a good powder for brass near the edge of real pressure limit. There is also the problems of being sticky in the Uniflow powder measure, and extra case capacity to take an over charge. Those problems are real, but a low loads, the accuracy, clean bore, and cool barrel make this powder very attractive for varmints.

Anyway, the .223 case head was designed for the .222 in 1950, and SAAMI registered at 50,000 psi. When the .223 was registered, it only went up to 55,000 psi registration with SAAMI.

My attitude is the if they could register the 270 at the 65,000 psi absolute limit of the brass, then they should have registered the .223 at ~ 80,000 psi

 

[NCsmitty]

Clark, I was wondering if the rifle suffered any damage? That is an extreme example of excessive pressure.

NCsmitty

 

[Clark]

I have never been able to damage an AR15 in a work up.
Nor a Ruger #1 223 or a Mauser in .223, nor a Sav99, nor a ....

I have Lux in .222 that is nothing but a .22 rimfire acton converted to centerfire by the Germans. The only lock is the bolt handle. If it did not have such a large firing pin hole, I think I could damage it in a work up. But it does handle the 50kpsi of the .222 loads.

I have been overloading guns to see what happens for allot of years, and one trend I see is that thin metal is a problem. There are two types of guns [that I have overloaded] that really are weaker than the brass and should not get overloads worked up:
1) Revolvers with thin chamber walls
2) CZ52 pistols with thin chamber walls.

I have lots of guns in storage that I bought for tests, but I have not got anything done with them yet, but the 3 AR15s I have can take the pressure I give them.

 

[kelbro]

I noticed in your pic that you are using different headstamps. I hope those are in different batches. Working up loads with mixed batches of brass can lead to problems due to different capacities.

Using Federal (FC) brass, you will see odd primer signs due to the fact that the primer pockets tend to loosen up quicker than with other brands.

 

[Slamfire]

"Reading" primers is tricky, in fact mostly guess work. You can blow primers with loads that leave rounded primers, but 99% of the time primers flatten well before you hit a max.

The basic problem is that primers back out of the pocket during combustion. They back out early in the pressure curve, before the case starts to stretch. Then as the front of the case adheres to the front of the chamber, and the back stretches back to the bolt face, the primer gets stuffed back in the pocket. This will often flatten out the primer, even with mild loads.

Very often in AR's the first indication that you really have high pressures is when the primer is blown. In a bolt gun you get positive indications of excessive pressure when the bolt is hard to lift. Since a gas gun lifts the bolt by itself, you don't get that warning signal.

When I am developing loads in my gas guns, which includes AR's, I lubricate the outside of the cases with case lube, paste wax, something. This keeps the case from sticking to the chamber walls and as the case slides to the bolt face the primer does not have the time to back out. As the load increases, and as I am watching velocities over my chronograph, at some point the primers flatten out. That does not mean I have hit a maximum load, but I believe I am getting close. Especially if the velocities over my chronograph are close to the velocities of published maximum loads.

If at any time during load development you blow primers or pierce primers, your load is too hot.

Then if I really like the load, I go shoot the thing. A number of times in matches I have had leaky primers in 100 F that did not look bad when I developed the load on the bench.

When that happens in a AR, I cut the load by a half grain. And I keep on cutting by a half grain if I ever get a pierced or leaky primer, until that stops.

I wish there was a better way, but I have not found it.