Regular vs. MilSpec vs. Magnum Primers

[tcoz]

In response to the post by T. O'Heir, I don't recall anybody stating that slamfires are caused by primers or rifles. You're correct in stating that they're usually caused by improperly loaded ammo, specifically improperly seated primers, BUT milspec primers do have thicker bases thereby making them more resistant to slamfires. If you look at the primer of an ejected, previously chambered unfired round from a semiauto rifle, you'll see the firing pin dent which indicates to me that a slamfire is definitely possible if the primer base is thin.

Milspec and magnum primers are charged the same and I was told by Hodgdon that they recommend the use of either of them with their spherical powders, specifically H335 because these powders are specially coated to slow their combustion and hotter primers are required for the most efficient ignition of them.

[Jimro]

Accuracy testing a 223 Rem at 50 yards is not a good indicator of how a low SD in velocity will actually affect group size.

You need to add some distance to see that affect.

People say that "relative group size doesn't change with distance" a lot, with the assumption that anything that groups tight at short ranges will group tight at longer ranges, but that just isn't the case. Things like barrel whip in an M14 or Lee Enfield can make things "come together" at longer ranges, and fall apart at the mid ranges. Initial instability caused by muzzle blast can record a group size at close ranges that is larger than what would be recorded after the intitial instability has resolved into spin stability.

Heck, weird things like the 22 rimfire experience, where Hyper Velocity rounds that group tighter at 50 yards can't hold a candle to the standard velocity rounds at 100 yards because they become unstable in the transonic region, where the standard velocity ammo starts out below that region.

I would say take the accuracy testing out to 200 yards if you can. That is a much better distance to guage the effect of primers on accuracy in the 223 Rem.

Jimro

[pathdoc]

Things like barrel whip in an M14 or Lee Enfield can make things "come together" at longer ranges, and fall apart at the mid ranges.

IIRC from the various Textbooks of Small Arms, this soldiers' equivalent of an old wives' tale was tested and the figure was 1500-ish yards for MkVI SAA ball and 800 yards or so for MkVII.

[Gary L. Griffiths]

Accuracy testing a 223 Rem at 50 yards is not a good indicator of how a low SD in velocity will actually affect group size.

Agreed. In point of fact, I'm working up loads to have similar POIs at 500 yds.

This thread was intended to be a discussion of the difference (or lack thereof) in velocity of identical loads primed with regular, MilSpec, and magnum primers. I'm not often able to get to a range with more than 100 yds, and, in any event, I believe that I accomplished what I set out to; discovering that there is no significant difference in the three types of primers, and thus no need to spend $44.00 per thousand for CCI-41s when I can get CCI-400s for $27.50 per thousand.

[4runnerman]

Gary- Your last statment is correct under the condition you do not load hot loads.
Your CCI-400's have a thinnner cup and will puncture with a hot load. Costed me a Firing pin just this spring. And while your FPS might not mean much,I have fond Accuracy to be much more consistant with Match grade Primers. I now Have 950 CCI-400's that I will never use sitting around.

[tcoz]

Gary, I agree with your statement about not finding it necessary to spend the extra money for CCI-41's. I use them because my LGS sells them for the same price as the rest of their CCI primers. From what I can remember however, almost everybody sells The CCI-450 Magnum Primers for the same price as CCI-400's and you might consider using them if you're loading for an AR or using one of Hodgdon's spherical powders.

[Unclenick]

Magnum primers make a larger volume of gas than standard primers do. This was originally to bring larger volume cases using slower powders up to adequate start pressure to get consistent powder ignition performance, but it also helps with any case that has extra space due to sub-optimal loading density. It also helps ignition of spherical propellants, especially, because of their high surface concentration of deterrents. Is the flame of a magnum primer stronger, hotter, and possessed of higher brisance? Not necessarily. Making more gas is one of those things that can be done by following different compounding strategies. You can get there with a longer sustained, but lower intensity burn, for example.

Since bullets tend to start moving out of the case at about the same pressure, regardless of what portion of that pressure was provided by the primer and what portion by burning powder, a magnum primer can actually help a light bullet move out too soon for the powder. The powder then never quite makes gas fast enough to reach its intended peak before the bullet progress down the tube has expanded the space behind it too much for that to work out. In that case, the peak pressure can actually be lower with a magnum primer. Harmut Broemel commented on that fact (though not the specific mechanism) in QuickLOAD's manual. Bottom line: it’s a complex system with a lot of interacting parts, and actual testing is needed to see what actually happens in your case.

It seems that, for the cartridges reported on in this thread, CCI has figured out how to make more primer gas pressure with a less violent priming mix, such that you don’t have to adjust your load when you switch among their standard and magnum small rifle primers. It’s nice to know it holds true for several chamberings. If it holds up for all chamberings (yet to be seen; I’d like to know how they compare in actual magnum cartridges and loads) then it’s a dandy bit of ingenuity for safety as well as ease of use.


Military primers vs. military sensitivity spec civilian primers.

Actual mil-spec primers undergo a fairly complex set of lot qualification testing involving hundreds of primers. These include visual inspection, wide temperature range performance, sensitivity testing and other reliability testing. They are detailed in MIL-P-46640E (attached, along with its supplement).

{edit: The file turns out to be too big to upload to the server here. If someone wants a copy, this link to a file sharing service should be good for the next month or so, anyway, and you can download it from there. I've put the spec page up here.}

The sensitivity spec is on page 4. It is determined by the H-test (height test), in which a weight is dropped onto the back of a firing pin resting on a primer seated in a case. The height of the drop needed to fire primers is the measure of their sensitivity, and there is a minimum OK-to-fire height (maximum sensitivity) and a maximum must-fire-by height (minimum sensitivity). There are standard deviations for this performance given in the spec.



FROM THE HORSE’S MOUTH: Over the phone, CCI told me their #34 and #41 primers are identical to their #250 and #450 magnum primers except for having a wider leg angle on the anvil to reduce sensitivity to military spec.

By email, Federal told me the GMM205MAR primer is the same as their 205M match primer except the sensitivity is brought within the military H-test limits by making the cup thicker. This is not a magnum primer, but a relatively mild primer, and will be best used with stick powders.

I do not know how Tula’s primer sensitivity is controlled. Their KVB762 primer is a standard large rifle primer meeting NATO sensitivity specs and their KVB556M is a magnum small rifle primer meeting NATO military sensitivity specs. In tests I’ve run and that Slamfire has run, these primers are remarkably consistent. You just have to pay extra attention to seating them correctly.

Alan Jones wrote that in 1989, CCI revised their magnum primer formulation specifically to optimize it for ignition of spherical propellants. At that time the Western Canon series (WC 296, WC 748, WC 844, WC 846, WC852, WC 760) were the lion’s share of spherical propellants used by handloaders. These are sold today in canister grade for handloaders as 296, 748, H335, BL-C(2), H380, and H414/760. This makes CCI magnum primers a good choice for these powders.


Slamfires:

In 1989 I was a volunteer line coach at the Ohio Rifle and Pistol Association’s Spring DCM Clinic on the Viale Range at Camp Perry, with about 450 people learning to shoot Garands. The ammo was LC 72 M2 ball, issued by the DCM for the clinic. There was a slamfire on the range immediately following the first “LOAD” command. Board member Hummer90, a former Aberdeen Proving Grounds test director, was involved in an investigation of an out of battery fire in a machine gun that killed a soldier to the side of the ejection port. These two events prove two things:

Slamfires are not all caused by improperly loaded ammunition, even though most civilian slamfires are a high primer problem.

Military primer hardness cannot prevent all slamfires. It just reduces the probability of having one by some factor.

You need gas-operated weapons with floating firing pins properly timed and within spec, regardless of the ammunition you choose.

As to the "need" for military sensitivity primers, again, they reduce slamfire likelihood, but not 100%. The military found it necessary to cut primer sensitivity, as the H-test requirements and the document Slamfire put up show, so referring to the concept as a "sales gimmick" strikes me as a gratuitous assertion. The military isn't interested in selling primers, and also, if the military hadn't done that work, it's possible the idea would never have occurred to the civilian ammo industry on its own.

Slamfires are not a high probability event in the first place, so the anecdotal evidence from people who've never had one dismissing people who have, doesn't prove anything. Most especially, it doesn't prove it can or can't happen to you, personally. So, anecdotal evidence has no way to tell you whether you, personally, need to use these primers or not.

My own decision to use the military sensitivity primers in my floating firing pin gas guns isn't based on me. I shot Federal 210M primers in my match Garand for years without issues. My concern is not that I am unwilling to take the risk for myself, but rather that the damage, in the event of an out of battery firing, as Hummer90's investigation showed, can accrue to the fellow on an adjacent firing point rather than to myself, in particular. That person hasn't had any say in how I reload, so I don't feel I have the right to subject him to any risk I know I can reduce. Since the military study shows their sensitivity specs do make a measurable risk reduction, I feel morally obliged to take advantage of that reduction for the other shooter's sake.

[tangolima]

I agree with unclenick, and I only use NATO primers in my m1s. I'd rather shoot some other guns if I can't find any.

Slam fire happened to me once and definitely I didn't have high primers.

-TL

[tcoz]

Very well said Unclenick. Case closed.

[Jimro]

Old wives tale? Good thing there are people who test things like barrel whip. http://www.varmintal.com/aeste.htm

May not have anything to do with primers directly, but it explains one aspect of why harmonics are so important to accuracy.

Jimro

[Unclenick]

Note to those who already saw my post. The system didn't allow the full primer spec file to go up, but I've gone back to my previous post and put the H test page in (declassified government document; public domain) and a link to a file host site you can download a copy from. The supplement is here.

[Bart B.]

The link jimro referenced that's about Varmint Al's barrel whipping page is a modern version of the 113 year old document on barrel whipping in the following link:

https://archive.org/details/philtrans05900167

Click on "PDF" for a printible document or "Read Online" in the "View the Book" window to read it directly.

All of which help one understand why primers have to start the energy system such that it'll push the bullet out of the barrel some ideal place on its upswing if best accuracy down range is the objective. Kind of dispells the other popular theories claiming some other place is best.

[Slamfire]

Slamfires are not all caused by improperly loaded ammunition, even though most civilian slamfires are a high primer problem.

There is no doubt that a high primer can cause a slamfire, but as this article states, a high primer is the most common cause of a misfire.:
Mysteries And Misconceptions Of The All-Important Primer
http://www.shootingtimes.com/ammo/am...motaip_200909/
Basically a number of conditions have to be met for a primer to go off. The anvil has to be firmly seated and the primer cake properly spaced between anvil and cup. If there is a gap below the anvil, and it is dangling in the air, the primer will misfire. If the primer cake is not firmly seated under the cup and on top of the anvil, the primer will misfire. Therefore, given a primer pocket of normal depth, it is unlikely that a high primer will ignite if struck. This is the problem Wayne Faatz describes in his article “The Mysterious Slamfire”. http://www.scribd.com/doc/2649554/Th...rious-Slamfire This article was written before shooters had a concept of “hard” versus “soft” primers, that is, at the time, it was widely believed that primer sensitivity was always the same regardless of primer and manufacturer. Wayne had an inbattery slamfire with Federal Match primers and was investigating the claims of “high primers”. Wayne was unable to get his high primers to ignite until he stuck a spacer under the primers, thus fulfilling the requirement of a firmly seated anvil and the primer cake pushed on the anvil.

A shallow primer pocket would create the conditions for a properly seated high primer. There may be other aggravating circumstances, maybe a tight pocket, maybe that would create the conditions necessary for a high primer to go off, I don’t know. One shooter removed the crimp from his military cases but left the brass donuts in the pocket. He reported in battery slamfires with his AR10. While it is easy to blame "high primers", over sensitive primers, I am of the opinion that the vast majority of slamfires are due to sensitive primers.


Until 1968, when the Army punted the NRA out of the tent, the NRA thought of itself as a quasi Governmental organization. American Rifleman staff and writers were typically retired Army Officers or Civilians. They thought they were carrying on God’s work, of encouraging marksmanship, and training civilians to be crack shots for that day when they were drafted into the Armed Services. As such, they were very “patriotic” towards the Army, as they sought, and received inside information and other tangible benefits by being “Greener than Green”.

I am of the opinion that the “high primer” cause of slamfires is a creation of these guys, or they were supporting an official position of the Army. I find it impossible that the American Rifleman author who claimed in print that only “high primers” and your worn out receiver bridge did not know about the problems that sensitive primers created. This gentleman was lead on the M16 primer slamfire issue, created reports and sent letters, to ammunition manufacturers, about the kinetic energy of the M16 firing pins. I have no doubt he was lead on drafting up the CC#41 primer requirements.

Going back into the American Rifleman magazines from the middle 50’s up to the turn of the century, whenever there is an article or letter about slamfires, American Rifleman writers always make claims that only high primers, or, your worn out receiver bridge, are the causes of slamfires. Garands had only been recently been sold to civilians, though they were very hard to get, if you wanted a NM Garand you had to travel to the National Matches to get one. Companies had standard grade to sell, from period ads in the American Rifleman, but they were around $700.00 - $1,000 in today’s money. At the same time these Garands are being used in competition, and competitors are having out of battery slamfires, Springfield Armory, the M14, are in the fight of their lives with Colt and the M16. I can’t prove it, but given the conflict of the times, it was easier for the Army to blame civilians and “high primers” than to admit that their babies, the Garand and the M14, could slamfire out of battery. It would have been an embarrassement to admit to a design fault, and it would have helped the M16 cause.


M14's did slamfire out of battery with military ammunition, but this report is exceeding hard to find. Lucky I have a paper copy: estate sales are wonderful things.

USATECOM Project No 8F-3002-04, Comparison Test of rifles, 7.62 MM, M14 Manufactured by Springfield Armory and Harrington and Richardson Arms Company. Author G. E. Hendricks, July 1963.

The Army was testing production models of H&R’s and SA’s for dimensional part compliance, (part interchangeability), such things as the thickness of the chrome coatings were measures, rifles were reassembled after gaging and underwent endurance testing.

At round 5271 a Springfield Armory M14 went off out of battery, with military ammunition. The report states:

“One rifle fired when the bolt was in the unlocked position causing breakage for the firing pin, extractor, bolt roller, ejector, and stock. The magazine split, causing the magazine floor-plate spring and 12 rounds of ammunition to be ejected against the bench rest from which the rifle was being fired. The case ruptured and several pieces of brass were found in the area. A broken part of piece of brass perforated a cardboard box with was position between the gunner and the proof director. The cardboard box was used as a brass catcher. Not all the broken pieces were found. Although no one was physically injured this is a seriously unsafe condition.”

So, six rifles were tested, five completed the test firing 6000 rounds each, one slamfired out of battery at round 5271, for a total round count of 35, 271. Therefore the probability of an out of battery slamfire with mil spec primers is 1:35,000.

But, everything I have written, T. OHeir has read before, in response to his knowingly fallacious statements. He is a CCI primer hater, is actively discouraging people from CCI primers, is not going to change what he says, and probably enjoys all the fuss he creates. Even though, if you believe him, and follow his advice, it will cause harm. I think that very unethical.

[mdmtj]

I shoot a lot of .223/5.56 from ARs. I use CCI #41 primers for all that I shoot. I look at them the same way I look at using seatbelts in my vehicles. I've never had a wreck so seat belt usage has never been a factor in my safety. However, every time I get in a vehicle I fasten the belt and any passengers with me will also fasten their belts. Wrecks can and do happen. Should I increase the chances of injuries seat belts can minimize by not using them just because I've never had a wreck?

It's the same with slamfires. They can and do happen. Most people firing weapons subject to slamfires will never experience one. Should I use a more sensitive primer in my AR ammunition just because I've never personnaly experienced one? Not using the less sensitive primer would save me about a penny per round. Thanks, I'll waste that extra penny just like I spend that few seconds fastening my seat belt.