Flattened primers, really that big of a deal?

[paramil]

So I have read that flattened primers are a sign of over pressure. I went back and looked at some of my previously fired factory brass and found that more often than not they also had flattened primers. So if factory loads are doing this in my rifle, should I still be trying to work down my personal loads?

How big a deal is the flattened primer anyways? I don't have a chronograph so I have no idea what my velocities are. Thanks in advance.

Rifle: Rem. 700 custom, .308, 25" barrel
Bullet weight: 175gr, 178gr
Brass: LC LR, Black Hills, Federal
Primers: Fed 210
Powder: IMR 4895, IMR 4064

Don't know if any of this data helps but figured why not put it out there. All loads are checked in manuals and not exceeded. Goal is 2600 FPS which is what the Black hills loads and federal loads advertise (yes, these are the factory loads that showed flattened primers after firing).

 

[ArmyJerry]

If your throat is cut short on the chamber the rounds could be jamming causing a spike in pressure whick will cause flattened primers sometimes, check your jam on the projectiles.

 

[BCP]

Google around for images of 'flat primers' and 'primer leakage'. Those are the things to watch out for. 41.5 of IMR4895 or 42 of IMR4064 in LC or FC cases should get you 2600fps with a full-length resized case and a length of 2.81" and not be anywhere near overpressure.

FWIW, what I do is chrono my loads (which you can't do) and compare the size of my fired cases to fired factory ammo (which you can do). Once I get a load where the cases are growing about like a factory match load I figure that it's a similar pressure, especially if velocity is comparable.

 

[wxl]

So I have read that flattened primers are a sign of over pressure. I went back and looked at some of my previously fired factory brass and found that more often than not they also had flattened primers. So if factory loads are doing this in my rifle, should I still be trying to work down my personal loads?

How big a deal is the flattened primer anyways? I don't have a chronograph so I have no idea what my velocities are. Thanks in advance.

Rifle: Rem. 700 custom, .308, 25" barrel
Bullet weight: 175gr, 178gr
Brass: LC LR, Black Hills, Federal
Primers: Fed 210
Powder: IMR 4895, IMR 4064

Don't know if any of this data helps but figured why not put it out there. All loads are checked in manuals and not exceeded. Goal is 2600 FPS which is what the Black hills loads and federal loads advertise (yes, these are the factory loads that showed flattened primers after firing).

Powder charge?

 

[paramil]

If your throat is cut short on the chamber the rounds could be jamming causing a spike in pressure whick will cause flattened primers sometimes, check your jam on the projectiles.

I am not sure what your referring to as "check your jam".

This (flattened primers) happened when the rifle was a stock Remington PSS, and now again once the gun has been barreled and trued by a professional smith. I only now noticed because since reloading I have become more/better informed.

 

[BCP]

I am not sure what your referring to as "check your jam".

This (flattened primers) happened when the rifle was a stock Remington PSS, and now again once the gun has been barreled and trued by a professional smith. I only now noticed because since reloading I have become more/better informed.

Primers always look 'flat' when people say 'flat' primers they mean how the primer will no longer have that rounded edge on it. Instead of a little 'valley' around the edge of the fired primer it will be exactly the same height as the case head. That doesn't necessarily mean your rifle is running at X amount of pressure or that the load is dangerous it's just one of many subjective things handloaders look at.

 

[paramil]

Google around for images of 'flat primers' and 'primer leakage'. Those are the things to watch out for. 41.5 of IMR4895 or 42 of IMR4064 in LC or FC cases should get you 2600fps with a full-length resized case and a length of 2.81" and not be anywhere near overpressure.

FWIW, what I do is chrono my loads (which you can't do) and compare the size of my fired cases to fired factory ammo (which you can do). Once I get a load where the cases are growing about like a factory match load I figure that it's a similar pressure, especially if velocity is comparable.

So I am loading the Hornady 178gr bullets behind 41.1gr of 4895 loaded at an OAL of 2.7955", Black Hills once fired brass
and
am loading the Sierra 175gr bullets behind 42.6gr of 4064 loaded at an OAL of 2.7955", LC once fired brass

Accuracy is outstanding, grouping 5 shots inside .53 MOA at 300yds.

I am holding .5 Mil at 100yds, zeroed at 200yds and .8Mil hold over at 300yds. Again not sure if this helps.

 

[Tempest 455]

You did not elaborate on the load for each. However, for example you are going to have a significant pressure difference bewteen LC and Win brass w/ a 178 and 4064 powder.

Chrono is your friend.

 

[paramil]

You did not elaborate on the load for each. However, for example you are going to have a significant pressure difference bewteen LC and Win brass w/ a 178 and 4064 powder.

Chrono is your friend.

True; however money is not. And for an accurate chrono you need $. LOL

 

[paramil]

Primers always look 'flat' when people say 'flat' primers they mean how the primer will no longer have that rounded edge on it.

Yup, that's my situation all right. No little valley.

 

[Tempest 455]

True; however money is not. And for an accurate chrono you need $. LOL

Just trying to help. I guess I would add, there is really no point in reloading if you don't know your velocity and can produce rounds in a safe manner.

A Magnetospeed can be had for $360. Factor what you paid for your rifle and glass. Knowing accurate velocity is the most important variable.

 

[paramil]

Just trying to help. I guess I would add, there is really no point in reloading if you don't know your velocity and can produce rounds in a safe manner.

A Magnetospeed can be had for $360. Factor what you paid for your rifle and glass. Knowing accurate velocity is the most important variable.

Your right, I may actually be selling my other precision rigg here shortly so I can get some other items I need to include that very chrono., plus precision rifle dies, some other precision 10/22 parts, an angle cosine indicator; oh and I almost forgot BABY CLOTHES. LOL

 

[BCP]

Lots of people use those loads my 4064 load is identical BTW. Unless you notice primer leakage (darky sooty stuff around the edges of the primer or leaking out to the edge of the case) or your primer pockets get soft after just 1-2 firings (when you reprime the case the primers go in really easily) I think you are fine.

I have a cheap chrony and it reads very close to what a friend's magnetospeed reads although it is not as reliable in different lighting. They are not gospel but will give you a good idea of what your load is running.

 

[vh20]

It occurs to me that pictures of these flattened primers would be very helpful in determining if they are anything to worry about or not.

 

[pawprint2]

Just trying to help. I guess I would add, there is really no point in reloading if you don't know your velocity and can produce rounds in a safe manner.

A Magnetospeed can be had for $360. Factor what you paid for your rifle and glass. Knowing accurate velocity is the most important variable.

I must take exception to your statement, " there is really no point in reloading if you don't know your velocity...."!!! LONG before chrono's were common, and/or not expensive as hell-there were a few accurate and safe rounds loaded. In fact, I'll go out on a limb here and say before almost anyone had a chrono of any kind, or access to one, some of the "fathers of bench rest" were able to shoot some fairly respectable groups, and a couple of decent scores were recorded up at Perry. Just saying...

 

[HodgdonExtreme]

As far as I'm concerned, you might as well look at tea leaves for pressure signs, then to gage primer "flatness".

The gold standard is an ejector mark on the case head. No brass flow into the ejector hole, no over pressure. If the brass is flowing, your primer pockets are also moving (loosening). I have lots of the infamous "soft" Federal brass with many many reloads on it, that still takes a primer nice and tight, having used the gold standard ejector mark as a pressure gage.

I've found 222 and 308 primer flattening to "kinda" correlate to ejector marks, particularly when loaded with Varget and heavy bullets, but in most other chambering, flatness is meaningless.

260 for example. You'll ruin a piece of brass in one shot (primer falls out), but the primer ain't flat.

As you gain more experience, you'll learn YOUR specific rifles traits and see the onset of pressure before you get the ejector mark - sometimes by a bit of primer flattening, sometimes by some cratering, other times other nuances. But at the end of the day, brass flow into the ejector hole (or the beginnings thereof) will NEVER lie.

...except!! So-called "weak" actions, like the M96 Swedish Mauser, might break before you've reached high enough pressure to leave the mark. In those special cases, adhere STRICTLY to max published loads for those rifles.

 

[witchhunter]

Federal primers are softer than some, try switching primers and see if you get the same look. CCI for one.

 

[paramil]

Thanks for all the info guys, kind of confirms what I thought. Thanks

 

[shoot4fun]

I must take exception to your statement, " there is really no point in reloading if you don't know your velocity...."!!! LONG before chrono's were common, and/or not expensive as hell-there were a few accurate and safe rounds loaded. In fact, I'll go out on a limb here and say before almost anyone had a chrono of any kind, or access to one, some of the "fathers of bench rest" were able to shoot some fairly respectable groups, and a couple of decent scores were recorded up at Perry. Just saying...

Agreed!
If the lack of a chrono made reloading a waste of time then I wasted about twenty years. Only reason I bought my first chrono was shooting a lot of USPSA and needed to "make major".

 

[dauntedfuture]

Federal brass is thick and soft. LC brass is thick and hard. I think BH brass is WIN but i'm not sure. Check the neck on a piece of fired brass to make sure you have enough clearance if factory ammo is "hot", to do this attempt to place a new bullet into a fired case, it should go in without much trouble, if its tight that's an indicator. Best way is to measure the OD of the neck of several fired cases and compare that to the OD of a loaded round with the SAME BRASS. Your fired cases SHOULD be at least .002 bigger then the loaded round, and unless your neck turning its better to have .003-.004 to account for variations in brass. If you don't have enough clearance, you will get high pressure on thick-neck brass and inconsistent pressures. It will shoot well but you will get high ES and SD and high pressure.

 

[KYpatriot]

Check out Montana Marine's excellent post, with picture, in this thread. He has the answers you seek

http://www.snipershide.com/shooting...-calling-all-brass-pressure-sign-experts.html

 

[bax]

I agree with this. I shoot exclusively Federal match primers. After firing, the primer is wider against the bolt face than at the case end. That is, the primer metal was deformed against the face of the case and partly/mostly filled the "valley" that existed around the primer before firing. I have limited cratering and I get about one blown primer per thousand rounds. I do not have ejector hole marks on my cases. If I have bolt-lift issues it is because the case is tight in (that is, expanded to tightly fill) the chamber. According to the reloading manuals, I am loading to moderate velocity/pressure. Federal primers are known to be soft so I figure that they are fine.

About 1993 I loaded some H1000 in my 300 Win Mag. I made a mistake. Instead of 72 grains, I had 82 grains. They made quite a bang and I had to hammer the bolt up after the second shot. I had serious ejector hole extrusion and shearing from opening the bolt. The gun was okay and it still shoots fine. I have not repeated that error. That is my definition of high pressure.

As far as I'm concerned, you might as well look at tea leaves for pressure signs, then to gage primer "flatness".

The gold standard is an ejector mark on the case head. No brass flow into the ejector hole, no over pressure. If the brass is flowing, your primer pockets are also moving (loosening). I have lots of the infamous "soft" Federal brass with many many reloads on it, that still takes a primer nice and tight, having used the gold standard ejector mark as a pressure gage.

I've found 222 and 308 primer flattening to "kinda" correlate to ejector marks, particularly when loaded with Varget and heavy bullets, but in most other chambering, flatness is meaningless.

260 for example. You'll ruin a piece of brass in one shot (primer falls out), but the primer ain't flat.

As you gain more experience, you'll learn YOUR specific rifles traits and see the onset of pressure before you get the ejector mark - sometimes by a bit of primer flattening, sometimes by some cratering, other times other nuances. But at the end of the day, brass flow into the ejector hole (or the beginnings thereof) will NEVER lie.

...except!! So-called "weak" actions, like the M96 Swedish Mauser, might break before you've reached high enough pressure to leave the mark. In those special cases, adhere STRICTLY to max published loads for those rifles.

 

[Greg Langelius *]

Taken by itself, primer flattening is not always a definitive indicator of excess pressure; but it is one of several that I pay close attention to.

Mention of ejector marks has been made and is, along with stiff bolt resistance on opening, a very significant condition. In my personal opinion, those are definite indicators that pressures are well above normal.

As for primer flattening, I look for a moderate degree of it to indicate that the pressure is in a 'working range'. As long as the primer edges do not become sharply extruded to a squared off appearance, I would not count on them alone to reduce my charge.

I believe the reference to 'jam' in this context relates to whether the bullets are seated long enough to engage the rifling when chambered, as opposed to not doing so and jumping into the rifling only after the cartridge is ignited. The former can result in a pressure spike as the pressure builds up enough to allow the bullet to actually begin its progress down the bore. For my part, I nearly always prefer my bullets to jump instead of engaging on chambering.

A pressure inducing condition that can sneak up on you and may be more prevalent with custom chambers is cases that have necks with excessive length growth. This is dangerous, and should be monitored closely. If the pressure seems to occur with a custom chamber and factory loaded ammo, it may be that the chamber neck is short. Even if it isn't short, a case that has grown beyond max length can still cause the same problem. Try trimming cases to the 'trim to' length, and if that doesn't reduce pressure signs, try trimming them shorter, your custom chamber may be shorter than that length.

Another issue could be headspace. If it requires significant effort to close the bolt on a factory loaded cartridge, your headspace could be shorter than SAAMI Spec; or the rifling may be engaging the bullet too deeply.

Is excess pressure a big deal? I think so.

First, it shortens barrel/throat life.

Also, MTBF (Mean Time Before Failure) estimates are predicated on remaining within SAAMI pressure limits. Every time a pressure spike exceeds such pressures, metal fatigue is induced at a higher rate than anticipated, so the action's MTBF shortens and becomes atypical. When an action fails catastrophically, it's usually not the specific firing which ensured the failure. It's the sequence of marginally overpressure firings that populate the action's history that's mainly at fault.

MTBF means that all actions will eventually fail, even if firings are within SAAMI pressure specs. They are simply engineered so that the MTBF is so long that essentially no action will ever be used that much. But exceeding expectations can change that.

Pressure is always important, and exceeding max pressures is always a big deal, especially when the consequences creep up on you over time.

Greg

 

[bruddah]

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