Primers backing out of fired cases, anyone seen this??

[joedwhit]

I recently loaded a batch of .270 Win ammo, using the max load of H4831sc listed in the Nosler manual, using virgin cases (RP). I fired off 30 rounds last month in my new TC Encore barrel, then decided to reload the fired cases. As I began to resize the cases, I noticed that the primers had backed out of the primer pockets a bit. It was noticeable once you looked, and if I stood them up on my desk, they would wobble. The unfired cases did not do this, so the primers were well seated to begin with. The micrometer showed normal expansion, and the spent cases ejected easily, as I recall. The primers were not excessively flattened. The fired cases did not show the telltale bright ring that indicates stretch due to excessive headspace, and they were virgin cases. Chronograph showed 3130fps from a 26" barrel, under published velocity in the Nosler manual.

If I had to guess, I would say that the chamber was cut a bit too deep, but shouldn't I get case stretch; that would be excessive headspace after all. I wound up neck sizing the cases, and we'll set what happens. Has anyone else seen this happen? Help!

 

[Blaine]

The primers backed out because the load was too hot. The head space allowed the primers to back out, but that doesn't mean the head space is excessive. I would try backing off on the powder charge 5% or so and see if that doesn't solve the problem. Although the load was "published" max, it doesn't mean it is safe in all rifles. Did you build up to the max load or start there? Hint: ALWAYS start loads 10% below published max and build up slowly checking for pressure signs.

 

[chet]

YUP, blaine is right! Mic the primer pocket and compare it to one of your virgin cases, I'll bet you'll find it enlarged too..... I've actually had primers fall out. All before they started to flatten..... sometimes pressures show up in different ways.... back off and be careful!!!

 

[R Flowers]

I guess I will muddy the waters here a little bit.

Primers backing out is supposed to be a sign of excess headspace. I have never heard of them backing out because of high pressure. High pressure usually causes primers to flatten or even pierce, but I have not heard of it causing them to back out.

Primers backing out is not necessarily an ominous thing. I have an XP-100 chambered in 6X47 that backs primers out all the time. The loads are not excessive, some of those caes have been loaded more than a dozen times. It does it on every firing, with no apparent problems. The gun shoots great and the case life seems to be close to forever.

No one I have shown the cases to seems to have an answer.

R F

 

[Accubond Believer]

Did you size your "virgin" brass before your test firing? If you did size the brass before firing - is the sizing die set correctly?

Just a couple of things to check.

Steve D. the HP

 

[clearwater]

a rough new chamber or a dirty old one will cause primers to back
out. I would clean the chamber well with some JB or flitz.

 

[chet]

greeat point Beleiver!
easy to overlook simple things
size too tight = excesive headspace

 

[joedwhit]

Thanks for the comments so far. No, I did not size the virgin cases. That would have caused the prblem had I done it wrong. I am almost certain it's not a pressure thing for the reasons I cited. This "recipe" is pretty modest. Back in the 80's I had a Ruger #1 in .270 that I fed the old classic recipe (Pet Loads, etc.) of 62 grains of H4831, got 3225 fps from that load, got primers flat as the Salt Flats (a pancake is the Badlands by comparason). That load was excessive. I can't possibly buy a tighter chamber or barrel than the proof barrels that Nosler and the others buy. My barrel is new, the bore is smooth and the chamber is clean. Given this, and the fact that I am getting slightly less than the published speed from 2' more barrel (pressure equals velocity, as one of the Handloader guys says), and I just can't buy the pressure theory. I am going to JB the whole thing though, that's a good idea. I like Mr. Flowers' theory, "sh.t happens. It will be interesting to see what happens with the neck-sized loads. The brass should have expanded at the shoulder to fill the chamber. Primers should not back out. I'll let you know next week when I get my next crack at the range.

 

[squirrelsniper]

The only time I've seen loads with primers backed out and no other symptoms were present was when the pressure was under normal operating pressures.

High pressure does not leave primers backed out. It can either flatten primers or loosen the pockets to the point that the primer will just fall out, but it won't just back out the primer, leave it sticking out and not do anything else.

Excessive headspace will back primers out upon firing, but if the pressures are within normal specs, the primers will get slammed back into the pocket and flattened when the case expands, so you still won't end up with primers sticking out of the case.

 

[joedwhit]

I think you are right on the money when you say that the cause is not high pressure. I've been reloading since 1980, read a fair bit about it, and what you say makes sense. But my goodness, if a max load of 4831 is underpressure!? It can't be, I'm getting 3140 fps or so. The barrel is 1-inch accurate, hardly a benchrest gun but good enough for deer at long range. I think I will fireform a few cases and see if they come out longer at the shoulder. I may also stop by TC and ask them if they have ever had any complaints. Thanks for your thoughts.

 

[steve4102]

I have the same problem in my New M70 6.5x55. I am using Lapua Brass. I was told that my brass could be too soft. Never heard that about Remington Brass though.

 

[Johnny Guttry]

I think you have a high pressure problem.Have been reloading since 1963.
The only time that I have ever had a problem with pressure has been with Barnes bulletts.The orignal barnes bullets have always had problems with pressure that is the reason that they developed the new triple shock!
As far as the load you used is conserned I have used it in several different rifles ,my son uses this load in a pre 64 win 70, no problems.What bullet are you using.The different shapes build different pressures do to the different bearig surfaces.

 

[Downwindtracker2]

I had a P-17 with headspace questions,eleven thousand of them .I could by underloading ,shorten my cases and have the primers back out;more powder would leave the cases the same length with backed out primers,still more powder would stretch the case and leave a "normal"looking primer.Even that was a lite load.I never went beyond that.

 

[Asa Yam]

Conditions that can cause backed out primers:

• Excessive headspace.
• High pressure loads.
• Low pressure loads.

What's going on here? Let's take a look at the firing sequence:

1. Firing pin strikes primer, and drives the case forward. Forward motion continues until something stops the case - these include:
   • The shoulder on a bottleneck case;
   • The belt on a belted case;
   • The rim on a rimmed or semi-rimmed case;
   • The mouth of the case against the chamber;
   • The extractor against the case rim.
2. Priming compound ignites;
3. Pressure inside the primer pocket soars - pressure exceeds 5000 PSI there. Primer backs out under pressure;
4. The main charge in the cartridge case ignites;
5. Pressure inside the case increases as more powder burns. As pressure increases, the case stretches as needed to fill the chamber;
6. When the case head is pushed backwards into the bolt face, the primer is once again seated flush.
7. If pressure is excessive, the case continues to deform. The primer pocket swells, and the primer deforms in an effort to try and fill the gap.

 

[tat2rtist]

Sounds like a head space problem. You could try 3 of the cases you already fired in the gun, and neck size them, this way the case is fire formed to the chamber, if it is a head space problem the prime should not come out, unless the primer pocket is enlarged. So check the primer pocket first and try a neck sizing die on the already fired brass, if it works the loads should be a little faster, seeing how all of the pressure will be going to the bullet not stretching the case to fill the chamber.

 

[EdK]

In addition to the excellent comments concerning neck-sizing the once fired brass, you may also want to try to measure headspace with the virgin brass.

In the Encore it's the distance from the case head when fully seated into the chamber to the breech face. If the case head is below-flush with respect to the barrel (typical) measure it with some sort of depth mic' then you add that number to the barrel/breech face gap (as measurecd by a feeler gage).

I heard you when you said you saw no ring about the case heads of the fired brass but it wouldn't hurt to measure to be doubly sure.

Ed

 

[Eagleye]

Primers backing out is almost invariably a case of LOW pressure, not high pressure!! The firing pin drives the case forward as far as the chamber will allow it, then the expanding gases cause the case body to adhere to the chamber walls. However, if the pressure is insufficient to force the brass case head to move back into full contact with the bolt/breechblock, the primer backs out a few thousandths of an inch,. causing the problem you describe. You may have a max dimension chamber, but it is unlikely that it has excessive headspace. In any case, if pressure was where it should be, even with a chamber that had a little too much headspace, that primer would not be backed out, but would be flattened more than usual. I have been reloading for more than 45 years, and have seen this scenario many times. Getting the pressures up where they belong will eliminate the problem. Quite often, the reloading manual max charge is not the max charge in a given rifle. A generous chamber/throat will lower pressures considerably, as will a slightly oversized bore, allowing more powder to be used safely. Regards, Eagleye.

 

[big rifle man]

Apparently a lot of shooters have experienced this problem for a lot of different reasons. I own a Rem. 700 with a match barrel in 7STW and I had the same primer problem. I tried everything and eventually found out that my batch of Remington brass was extremely soft. I switched to Winchester brass and the problem disappeared. In addition to the loose primer pockets I had severely stretched brass and ejector marks on the case head. Again, switching to Winchester corrected the problem and I was actually able to increase the load (within safe limits)

 

[clearwater]

Winchester 30-06 brass is known to be a couple of grains larger
capacity than Rem. Don't know about other calibers.

If you think you got a bad batch, you
can return them to Remington and they will replace them if defective.
Might be good to send them a couple of fired ones and see what they
say.

"Apparently a lot of shooters have experienced this problem for a lot of different reasons. I own a Rem. 700 with a match barrel in 7STW and I had the same primer problem. I tried everything and eventually found out that my batch of Remington brass was extremely soft. I switched to Winchester brass and the problem disappeared. In addition to the loose primer pockets I had severely stretched brass and ejector marks on the case head. Again, switching to Winchester corrected the problem and I was actually able to increase the load (within safe limits)"

 

[Greg Nolan]

I've had this happen on rifles with excessive headspace due to the bolt being set back(the lugs aren't exactly even on most factory rifles and too hot a load too many times overloads the tightest lug untill it matches the loosest lug) the case slams back as the pressure builds and actually re-bounds forward. By this time the case has expanded enough under pressure to grip the chamber wall leaving enough space for the primer to back out a bit. In the case of the TC it amounts to the chamber/headspace to be a little loose. T/Cs have a pretty tight lock up so I wouldn't expect that but something is allowing too much movement of the case in the chamber. A go/no-go headspace gauge set might help determine that. You cant tell much by micing the case because it is forward in the chamber when it grabs so everything will be about right except the primer has backed out a little. Extraction is sometimes a little more difficult but not always if the chamber is smooth and clean. Good Luck and let us know what you find.