9mm flattened primers

[DRobson]

I've been reading lots of posts of here but this is my first one.

I'm new to reloading but trying to lean everything I can but here's my problem. I'm loading speer 115gr TMJ's over 4.5grs of W231 with a OAL of 1.130. These loads work fine in my M&P's and FNX9. I just tried them in a Sig p226 and a few of the cases have flattened primers. It seemed to happen a little more often with the Winchester primers but it also happened with the wolf primers. Is overpressure the only cause of flat primers or is there something else I can look for?

 

[Walkalong]

That load is perfectly fine. Well under max. Primers are an unreliable gauge for pressure.

Welcome to THR

 

[noylj]

You might have excess head space due to short cases and the chamber in Sig. The firing pin shoves the case forward (cases are almost all too short), sets off primer, primer is blown backwards as the powder ignites. The case slams back into the primer and the primer gets flattened. Not over pressure but excess head space.
For primers, you need to compare at least to factory ammo fired in your gun. You can also track case expansion about 1/4" above the extraction groove.

 

[DRobson]

That makes sense, especially since i'm using mixed cases and it's only random. Also the primers aren't completely flat or "melted" looking. Thanks for the help

 

[Slamfire]

I develop loads in semi autos with lubricated cases.

I found that lubricated 308 cases gave me rounded primers with my loads but dry cases gave me flat primers. Obviously the combustion pressures were the same, so dry cases were giving me false indications of pressures.

I agree with Walkalong, primers are unreliable indicators of pressure.

Now I develop loads in semi autos with lubricated cases. I can clearly see the transition from rounded to flat, and I record when that happens. Might mean something, might not. But it is of interest. I do believe I am approaching a max load when the transition happens, if I already have not already blown or leaking primers.

When it comes down to primers, if they are leaking or blown, that is 100% absolute proof of over pressure loads.

 

[1SOW]

That should be a good load in your pistols. My Sig would shoot that fine.

With my LEE turret press it's possible to seat primers a little too firmly. The result shoots fine, but the primers look 'flattened BEFORE' you fire. The softer the primer case, the easier it is to use too much force when seating them.

noylj:

You might have excess head space due to short cases and the chamber in Sig. The firing pin shoves the case forward (cases are almost all too short),

Maybe I misunderstood what you meant; but a slightly shortened case still seats on the case mouth and can't "be moved forward" by the firing pin. The only change with a shorter case is the bullet seating depth (it's less deep in the case by a few thousandths). The OP at 1.130 should have around a couple of "tenths" extra head space with TMJ RN bullet.

 

[Walkalong]

Unless the bullet stops forward movement by jamming into the lands, the case will move forward until the case mouth contacts the shoulder in the chamber. If the case is too short, or the pistol has excess headspace built in, you have a headspace problem which can do exactly what noylj posted.

 

[gamestalker]

Split cases and even head separation, is not always a clear cut high pressure indication with AL firearms, especially straight walled AL's. Brass that is out of spec. for what ever reason, including too much crimp, or simply longer than the maximum as determined by SAAMI standards, can cause a head space problem. And because all firearms are not exactly identical regarding chamber chacteristics, some rounds may function OK in one firearm, but not in another.
Flattened primers in my opinion are usually caused by pressures being pushed up for various reasons. Either the cases are too long / too short, bullets are seated too deep, powder charge problem, a crimp is too heavy, or a the gun has a head space problem. Obviously these are not all of the possible causes for pressures to become a problem, but I think they cover a good range of causes.

 

[1SOW]

Walkalong/noylj, doesn't 9mm "SEAT" on the case-mouth when it's fed into the chamber???? How can it go into the chamber beyond the case-mouth seat?

Unless the reloaders oal is "too long"/not allowing a little room for press and reloader handle pull errors (.015" or so) , the bullet nose won't make contact with the chamber before the case mouth seats. Once it seats how can it move forward by the FP striking it? .

I'm asking this honestly. I've loaded 9-10 different 9mm bullet nose shapes using 100% range pick-up brass and have never experienced what (I think) I'm reading above. Maybe I've misunderstood the principle of the case mouth "seating" when it's fed into the the chamber. With the case mouth taper-crimped firmly to the bullet, I just don't understand how a FP can force it further in. Or have I been lucky 25K times?

 

[noylj]

The theory says it headspaces on the case mouth.
If you drop a few sized cases into your barrel, you will see many a 1-2mms short of headspacing at the barrel hood. If the barrel was chambered even deeper, your cases will have that much more headspace. A lot of 9x19 rounds (and other semi-auto rounds) are actually headspacing using extractor. This is why those few long cases that can actually headspace on the case mouth and be within 1mm of the breech will produce the best accuracy.
Alternatively, many of us set the COL such that the bullet establishes the headspace such that the case head is actually close to the breech.
Everyone should always get to know their guns and rounds well enough to know what and where headspacing is actually being achieved and if there is a problem that should be fixed.
How many of you have actually tried to move the slide back in small increments to see how "out of battery" your gun can be and still fire?
It's what you think you know that get you in trouble.

 

[243winxb]

Short Chamber

There was a thread on here a while back with primer pressure signs in 45acp. A short chamber was said to be the problem. Here is the photo the person posted. The primers shows pressure signs caused by a short chamber in 45 acp, 1911 type firearm. As the action opens the high primer gets primer wipe. A gun smith corrected the chamber problem with a reamer. Not sure i buy this as the cartridge headspaces on the case mouth. Not sure how it could build pressure this way as the bullet is not trapped/ crimped into the chamber like a bottle neck round in a bold action rifle. The 45acp short chamber would hold the action open a tiny amount but still fire if the disconnector was not activated. A bulge might appear near the head if pressure was high. Very Strange.

 

[Walkalong]

Maybe I've misunderstood the principle of the case mouth "seating" when it's fed into the the chamber.

The case just floats back and forth (front to back) in the chamber. The breech stops its rearward motion and the chamber shoulder stops its forward motion. Assuming the bullet is not able to touch the lands when fully forward the firing pin will push the case forward until the case mouth contacts the chamber shoulder.

With the case mouth taper-crimped firmly to the bullet, I just don't understand how a FP can force it further in.

It doesn't, that is not what we are talking about.

Or have I been lucky 25K times?

Not lucky because you have been following good load procedures, have been careful, and you gun is mechanically sound.

Alternatively, many of us set the COL such that the bullet establishes the headspace such that the case head is actually close to the breech.

Yep, you can control the amount the round can move in the chamber using the bullet engaging the rifling, keeping the base of the case near the breech of the firearm, much like you can control headspace in a bolt gun with how much, but mostly how little, you push the shoulder back.

 

[psyshack]

Adjusting head space off the bullet IMHO is a bad thing on 9mm and other such style of ammo.

 

[Walkalong]

Why?

Besides, the target shooters are really just trying to get each bullet started just alike. The headspace in their guns is just fine, unless of course a grossly short case slips through.

 

[1SOW]

Walkalong/Noylj,

I just measured a few 9mm range pick-ups. The shortest of ten was .7440 and the longest was .7450. I sized both and one was then .7465 and the other was .7480. I fed the cases into a 9mm CZ Shadow bbl, and they seated on the chamber's machined seat. The head of the shorter case was slightly under the bbl hood and not quite under the hood with the longer case.

I can now understand there would be "play" when the slide is fully forward and the case-mouth may not be touching the seat especially with shorter cases.

So when the pistol feeds the bullet, it may not be "seated" but somewhere between seated and back against the breach face?
I can see the FP being able to move the cartridge forward in that case.
Have I got it right?

I thank you both for your patience and willingness to "try" and make an old guy better informed.

 

[rfwobbly]

Here's one of Walkalong's photos I just love....



...............Wuss.................Normal.......................Whoa Mama!

 

[psyshack]

Walkalong

I want my 9mm brass trimmed to where I have a very slight amount of slop or travel for and aft when a round is chambered. IE just under the barrel/chamber hood. Then I set my bullet depth just off the lands with the round inserted into the chamber. All done by hand fitting round to chamber/breech.

Yeah I to like to keep the slop to min. And I do end up working my loads up to major loads more times than not. I just don't want any psi spikes.

In my mind setting up head space off the bullet/lands is a disaster in the making.

Just my humble opinion.

 

[918v]

Most 9mm chambers are cut to a .762" depth, so there is no need to trim even the longest of 9mm cases.

 

[Walkalong]

In my mind setting up head space off the bullet/lands is a disaster in the making.

They are not "setting up headspace". The headspace is fine, they are just seating to the lands.

 

[918v]

Seating to the lands would work better if bullets were consistent. As it is, the ogjive position varies so much from one bullet to the next that seating to the lands is impractical, especially in magazine fed pistols.

 

[243winxb]

Seating into the Lands

Seating to the lands in 45acp is more accurate using lead bullets. There is a fine line between go & no go. Best used for slow fire at the 50 yard line. I measure to the bullets shoulder for a more accurate COL. On cast bullets, the nose to shoulder distance will change with the alloy used.

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[918v]

I'd like to point out that primer appearance should be analyzed keeping the primer brand in mind. Because primer cup hardness varies from brand to brand, what appears normal may be excessive and what appears excessive may be normal.



For example, if the first case in the picture contains a CCI-550 primer, then one can infer the pressures are normal, near max. On the other hand, if this case contains a FC-100 primer, then one can assune the pressures are low. Why? CCI-550 primers have the hardest primer cups of all small pistol primers. FC-100 have the softest primer cups. Pressure that barely flows a CCI-550 will nearly melt a FC-100 primer.

Looking at the last case, if it has a WSP primer than it may be max, but not necessarily. WSP primers are only slightly harder than FC-100. On the other hand, if that is a WSPM primer, than the load is certainly excessive. Why? WSPM primers have harder primer cups than WSP an they should not look like that at normal 357 pressures.

So don't automatically freak out if your primer looks like it is flattened, or even melted into the casehead. It all depends on the primer brand and type.

 

[Walkalong]

From post #2:

Primers are an unreliable gauge for pressure

There was a thread not long ago with some Winny .357 ammo with primers that were just absolutely hammered looking. I forget the answer that Winchester gave, but the look was normal and not over pressure.

 

[DRobson]

Just to add to this thread. I made up more 9mm rounds but used 4.9grs of w231 this time. All 10 of the rounds looked perfect with zero sign of primer flattening.