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Primers backing out...

O

oneshot onekill

Gunny Sergeant
Full Member
Minuteman
Jul 29, 2008
1,952
9
60
DeBary, Florida
OK... I'm relatively new to reloading although I've been around it for many years. Just never actually did my own from start to finish until recently. Anyway, I'm having issues with primers. They're either getting pretty flattened (sign of over-pressure) or backing out slightly (also a sign of over-pressure). My loads are relatively light and I don't crimp so I'm wondering what I'm doing wrong. The round is .308. The brass is either LC Match or Hornady and they are batched together. Here's some information about my process...

Tumble
Full-length resize
Trimming and de-burring down to 2.010"
Tumble
Clean primer pocket
Prime, using a single stage Lee press w/ Primer attachment. (Primers are CCI200 Large Rifle Primers)
Load with 40gr. of Varget
Seat 150gr Hornady BTSP to 2.790" OAL

When I prime I'm pushing the primers until they bottom out. I thought I wasn't pushing them in deep enough but can't see how that could be since I'm actually flattening them slightly when I press them in. They feel like they are very slightly past flush with the bottom of the shell.

No other apparent signs of over-pressure. The bolt opens easily. The brass looks good. Sometimes the extractor doesn't catch the lip of the round. Could I have pushed the shoulders down. I've been told "No" because of the way I'm full-length re-sizing.

Sorry to be so lengthy. Any help is Much appreciated!

John
 
Re: Primers backing out...

Whats the diameter of the primer pocket before you prime?? have the pockets been uniformed??
 
Re: Primers backing out...

It sounds to me like you are pushing the shoulders back too much. How do you size?. The extractor not grabbing the rim is a bad sign. Be careful...with that much headspace, you could be looking at a bad case head separation.

Who made the gun?

edited: Did someone tell you that you weren't oversizing? It is possible for a die to simply not work with a certain chamber. The dies vary just like chambers do. That is part of the reason small base dies are made. Even if you went through a careful setup of the die using fired brass, you coud still end up with excessive shoulder bump. My advice is to get a tool for measuring headspace, a micrometer if you don't already have one, and start comparing some of your sized vs. fired brass.
 
Re: Primers backing out...

2 things jump out at me here. 1- your are mixing the head stamps (brands) of 2 very different brands of brass. The LC brass is very thick and reduces your internal case volume. The Hornady has a fairly normal case volume. You will get different pressures from the 2 cases. I would pick 1 case and run with it. 2- why 40 grains? That is a very low charge. It is below book minimum by 4 grains. And 308 Win data is very conservative on the low side. So, you could be getting pressure because you are loading them too light. I would bump up my charge to at least 40 grains. But first, I would get online or get several reloading manuals and read the intro at least twice. The first time for an over view, the second time to study it.
 
Re: Primers backing out...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bonzy</div><div class="ubbcode-body">Whats the diameter of the primer pocket before you prime?? have the pockets been uniformed?? </div></div>
I haven't measured the pockets but they are "once-fired" and the primers are pretty tight to seat. The LC brass does not have crimped primers.
 
Re: Primers backing out...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cpl Snafu</div><div class="ubbcode-body">It sounds to me like you are pushing the shoulders back too much. How do you size?. The extractor not grabbing the rim is a bad sign. Be careful...with that much headspace, you could be looking at a bad case head separation.

Who made the gun?

edited: Did someone tell you that you weren't oversizing? It is possible for a die to simply not work with a certain chamber. The dies vary just like chambers do. That is part of the reason small base dies are made. Even if you went through a careful setup of the die using fired brass, you coud still end up with excessive shoulder bump. My advice is to get a tool for measuring headspace, a micrometer if you don't already have one, and start comparing some of your sized vs. fired brass. </div></div>
The rifle is a 40X in 7.62 Nato.

I think my Dies are Lyman but I'll check after work. I size by pushing the shell into the die until the shell-holder hits the die. That's how I was told to do it by the person that owned the dies before me. The brass I'm sizing is all "once-fired" brass but was fired in different rifles over the years. I've been collecting brass from various rifles I've owned. I figured I was just sizing it all back to normal "fit anything" size by doing that. Then I would size to my chamber once I fired the rounds. It's an "FL" marked die. I asked about pushing the shoulders back but was told it couldn't happen if I was sizing the way I am. I'll do some measurements ASAP.
 
Re: Primers backing out...

My immediate opinion would be to confirm (as has been observed) that your starting charge is too low. Too low of a charge can create an overpressure situation as well as too great a charge. Your starting charge should be around 44 grns., I'm NOT ADVISING you to start at 44 grns. just looking at the variables you have mentioned it's the first one I would consider since you are full length sizing.
 
Re: Primers backing out...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChadTRG42</div><div class="ubbcode-body">2 things jump out at me here. 1- your are mixing the head stamps (brands) of 2 very different brands of brass. The LC brass is very thick and reduces your internal case volume. The Hornady has a fairly normal case volume. You will get different pressures from the 2 cases. I would pick 1 case and run with it. 2- why 40 grains? That is a very low charge. It is below book minimum by 4 grains. And 308 Win data is very conservative on the low side. So, you could be getting pressure because you are loading them too light. I would bump up my charge to at least 40 grains. But first, I would get online or get several reloading manuals and read the intro at least twice. The first time for an over view, the second time to study it. </div></div>

I'm actually not "mixing" the headstamps but both are doing the same thing. But I am loading them to the same specs. I know the LC stuff is much thicker. I have about 5 or more different brands of brass. All seperated by headstamp and year purchased. The reloading manual I'm using shows loads for Varget down to less than 39gr for my 150gr bullets. I was trying to be somewhere in the middle. It also shows 44.something grains to be the MAX. Your post said to use at least 40 and that's what I am using.

What is it with manuals being so different!
 
Re: Primers backing out...

This is all GREAT information and I'm thinking I need to load hotter. I currently have some LC brass ready for powder. Any thoughts on how much Varget for that particular brass? When I put 40gr. in it the powder comes up to just below the neck. I've heard on various posts that 43gr. is a good benchmark to work from. I definitely don't want to get into that "secondary pressure" issue... Sounds like I may already have!!!
 
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Re: Primers backing out...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: EXTREMEPREJUDICE</div><div class="ubbcode-body">http://data.hodgdon.com/cartridge_load.asp

</div></div>
OK... So the site says to start with 44gr. Would you even load LC brass to this spec? I've been told to subtract at least 10% for the thicker brass which puts me back at around 40gr.!!! (Actually 39.6)

I hate to think this but maybe I'm over-pressure with the LC brass at 40gr and experiencing "secondary pressure" at 40gr. with the Hornady Brass?!?!... AAAAHHHHH!!!
 
Re: Primers backing out...

The primers back out to the limits of clearance between the case jammed into the chamber and the boltface early in the firing sequence, then the cases back up against the boltface IF the pressure is high enough to stretch them.

Then, because the primer cup was able to "mushroom" outward into the radius of the primer pocket and outward in diameter, it *will* get flattened rather impressively because there's no way to smash that primer cup back into the pocket.

No other "pressure signs" will be present.

Check sizing, do it less aggressively. Otherwise, expect those cases to separate after three reloadings, regardless of pressure levels.
 
Re: Primers backing out...

I'm visualizing what you are saying... So, ALL primers will back out? And then, if the pressure is high enough to stretch the brass, ALL primers will flatten "rather impressively"?

Is THAT amount of pressure too much?... Or just an observation.
I'm confused because I thought the brass always stretched.

In this scenario ALL primers will either be pushed out or flattened "rather impressively". I'm not trying to ba an ass, just to understand.
 
Re: Primers backing out...

Ok, several things. First, I'm not saying you definately are undercharged, just to look at it. Second, yes you are correct, milspec brass is generally thicker walled than commercial brass and may then have less case volume. You can only determine it absolutely by volume testing (usually with water.) Third, you could be incorrectly resizing the cases as has been mentioned creating excessive headspace. I did not initally believe that to be your problem as you were correctly full length sizing but NOW I realize it should be considered. If that IS the case you do not want to increase your charge! I'm hoping that you do know that your rifle is in spec. and the problem is related directly to your handloads (factory ammo is just fine.)
 
Re: Primers backing out...

I bet a little oversizing and a little under pressure are both happeining.

In order to determine if the cases are being oversized, you need a case micrometer or a case gauge. Honestly, I don't see why people even try to reload without one of these; but I digress.

An underpressure load has some interesting physics in the interrior ballistics. The charge accelerates the bullet down the barrel. However somewhere after about 1/2 way down the barrel the bullet starts to decelerate because of insufficient pressure. The blast wave from the burning powder does not decellerate, and when it reaches the back of the bullet, it sets up a shock wave that travels down the barrel towards the case, and as this shock wave passes through the burning mixture, the pressures get high enough that the burn changes into a detonation. Pressures go way up, bad things can happen.

Normally, the firing cycle causes the cartrige to move forward until the case impacts its headspace (shoulder for the 308) and at this point the primer ignites. Then the powder starts to burn, the case neck starts to grab onto the chamber as pressure rises. The primer is pushed back to the bolt, and THEN the case expands at the web and the base is rammed back to the bolt. This flattens the edges of the primer cap if there is too much headspace even if the pressure is just fine.

All of this indicates that reloaders should be careful with light loads {not to say anything about bullets that do not end up leaving the barrel}, and careful not to oversize the cases. This is where the case micrometers and case gauges come into play. So you can measure the sizing processes at least as well as you measure the charge weights.
 
Re: Primers backing out...

First, thanks for the information. The volume is definitely different because with the Hornady brass 40gr fills it to the bottom of the shoulder. With the Lake City Brass it fills it closer to the top of the shoulder. I'm wondering how it is that I could be pushing the shoulders back when the die is a finite length and I'm supposed to push it to touch the shell-holder. Not doubting that could be the problem, just looking for the physics behind it and the solution. I could see if I was not touching and the shoulders being too high since the round was fired out of who knows what. I don't size aggressively.

Now... I have about 45 unfired Hornady's and another 40 Lake City ready for powder. Can I shoot them?
 
Re: Primers backing out...

Do this:Unscrew the sizing die one turn. Take a few fired cases from that rifle. Lube them. Size one case. Try it in the rifle. It may chamber ok, but you aren't touching the shoulder with the die. Screw in 1/16 turn. Resize and retry case in rifle. As you get close to FL sizing, the brass will lengthen and become hard to chamber. Don't force it in. Continue to turn the die in and resize and retry in the chamber. As you continue, you'll find a point where the bolt closes with a slight resistance. You are at the tightest fit for maximum case life. If you are using it for rapid fire, screw in 1/16th more and lock the set ring. That should allow the bolt to drop freely. Resize a few more cases and try them in the chamber. If all works smoothly, load a few up and try them. I'll bet the problem disappears. JMHO
 
Re: Primers backing out...

Here's a question... Is there even the remotest (is that a word?) possibility that the fact that the rifle is chambered for 7.62 NATO (and not .308) makes a difference in case dimensions. My first thought is "no". But I have to mention it... just in case.

Thanks again,
John
 
Re: Primers backing out...

Not as remote as you might think. A milspec 7.62 chamber length (headspace) can be as much as .013 greater than a .308 Win. 1.645 vs. 1.632. In most cases we just think them as interchangeable but not so. Considering all the other factors in play, that might be on target. If your rifle chamber is on the long side, your FL die is on the short side.......? Have you ever fired .308 Win. factory ammo in your rifle, effects?
 
Re: Primers backing out...

The ammo is almost always the same dimensions, .308 vs. 7.62x51. The military chambers *can* be longer and still be "in spec", because they are after reliability on one firing, NOT long case life on multiple reloadings.

That's the problem with the "standard" instructions to resize the cases by cramming the shellholder up against the die. Mine left something like .015 clearance, and the feed cycle with the extractor snapping over the rim is KNOWN in M1s and M14-types to shorten the case a bit when chambering.

Below 50 F, the primers stayed rather impressively backed out. Above that, they looked pretty darned flat and I feared that I was pushing MAX pressures.

Cases started breaking on the SECOND reload.

Years later, QuickLOAD says my loads were just fine, based on case capacity and velocities recorded from 40 to 100F.

I started using the Wilson gage and now resize to the middle or top of the zone, which with three separate dies (one wore out, I replaced it, then I got an X-die) has ALWAYS required me to back the die out from LIGHT contact with the shellholder/shellplate by about 1/8-turn.

Calibration is your friend. Your cases are talking to you. Listen to them.
 
Re: Primers backing out...

Well, once again thank you all! I'm learning tons! I went to my brother who has been reloading for about 25 years. He prefers to see me learn from my mistakes rather than help me avoid them which I actually appreciate because the lessons learned tend to stick. Anyway, he broke down and loaned me a .308 case length gauge because even he didn't know what to make of my problem given the fact I got the re-sizing die from him and he told me how to use it... What do you know... My primed cases have shoulders that are .015 too short! The overall length is right but the shells stick out the top and are set-in on the bottom. Both ends by .015"!!! Hopefully problem solved. Many thanks to all who have been so helpful!

I have about 80 rounds that are this way. Will it damage my rifle to just shoot them and discard the brass? They actually group very well... Figures!
 
Re: Primers backing out...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: oneshot onekill</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cpl Snafu</div><div class="ubbcode-body">It sounds to me like you are pushing the shoulders back too much. How do you size?. The extractor not grabbing the rim is a bad sign. Be careful...with that much headspace, you could be looking at a bad case head separation.

Who made the gun?

edited: Did someone tell you that you weren't oversizing? It is possible for a die to simply not work with a certain chamber. The dies vary just like chambers do. That is part of the reason small base dies are made. Even if you went through a careful setup of the die using fired brass, you coud still end up with excessive shoulder bump. My advice is to get a tool for measuring headspace, a micrometer if you don't already have one, and start comparing some of your sized vs. fired brass. </div></div>
The rifle is a 40X in 7.62 Nato.

I think my Dies are Lyman but I'll check after work. I size by pushing the shell into the die until the shell-holder hits the die. That's how I was told to do it by the person that owned the dies before me. The brass I'm sizing is all "once-fired" brass but was fired in different rifles over the years. I've been collecting brass from various rifles I've owned. I figured I was just sizing it all back to normal "fit anything" size by doing that. Then I would size to my chamber once I fired the rounds. It's an "FL" marked die. I asked about pushing the shoulders back but was told it couldn't happen if I was sizing the way I am. I'll do some measurements ASAP. </div></div>

GET A CASE GAUGE!
 
Re: Primers backing out...

Yes... Got a case gauge. Yes... The shoulders were pushed back by .015". That's already been covered.

What I would like to know now is:

Can I fire the 80+ rounds I already sized wrong without damaging the rifle? I plan to chuck the brass afterward.

Thanks again,
John
 
Re: Primers backing out...

I know what you are thinking and MIGHT be right, but you already know the best answer! Of course the problem is that unless you fire them you have no chance of expanding and then reusing the brass and probably the primers. You can't "bump" the cases back by any other method I know of. The question is that if you do take a chance what will you gain? How many more firings will you be able to utilize from the stressed cases anyway? IMHO just pull the bullets, save the powder, and then fire the empty cases to deactivate the primers and scrap the brass.
 
Re: Primers backing out...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: EXTREMEPREJUDICE</div><div class="ubbcode-body">I know what you are thinking and MIGHT be right, but you already know the best answer! Of course the problem is that unless you fire them you have no chance of expanding and then reusing the brass and probably the primers. You can't "bump" the cases back by any other method I know of. The question is that if you do take a chance what will you gain? How many more firings will you be able to utilize from the stressed cases anyway? IMHO just pull the bullets, save the powder, and then fire the empty cases to deactivate the primers and scrap the brass. </div></div>
Wait just a minute here.

I have fired cases more than once that short, and they didn't break the first time, not a one.

You *could* probably blow out the shoulders using a charge of WW 231 and a tissue wadding.

Scrapping brass means SELLING for scrap. These you could also turn into .45 ACP shotshells. This stuff is always worth more fabricated than melted down.

If it was me, I'd just shoot them and then check for thinning in the case body. The .308s I've seen always do it about 1/2-inch up from the base. If none, fire away. If thin, scrap.

If really, REALLY cautious, pull two bullets and check the existing cases. If thin, scrap. If no reverse ridge, go ahead and shoot 'em.

YMMV, but the LC cases I destroyed that way all stayed sealed at the back end when they broke on firing. It all depends on where they get thin and break.
 
Re: Primers backing out...

Should they shoot fine this time because this is the first time they were sized wrong? I'd rather send them downrange if it will have no ill effects on my rifle. The only issue is extraction. I have to push some of them out with a cleaning rod. It doesn't take any effort. They just don't get grabbed by the extractor because they're in there a little too far... and I guess there isn't sufficient pressure to push them back enough to be grabbed once the primer pushes out that .015".
 
Re: Primers backing out...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: former naval person</div><div class="ubbcode-body">Do this:Unscrew the sizing die one turn. Take a few fired cases from that rifle. Lube them. Size one case. Try it in the rifle. It may chamber ok, but you aren't touching the shoulder with the die. Screw in 1/16 turn. Resize and retry case in rifle. As you get close to FL sizing, the brass will lengthen and become hard to chamber. Don't force it in. Continue to turn the die in and resize and retry in the chamber. As you continue, you'll find a point where the bolt closes with a slight resistance. You are at the tightest fit for maximum case life. If you are using it for rapid fire, screw in 1/16th more and lock the set ring. That should allow the bolt to drop freely. Resize a few more cases and try them in the chamber. If all works smoothly, load a few up and try them. I'll bet the problem disappears. JMHO </div></div>

This is right oneshot, but i wanted to mention some other details. Take the firing pin assembly out of the bolt for the above operation. You won't be able to feel how the bolt is closing on the case with the firing pin cocking at the same time. It is extremely easy to take the bolt apart this way using a penny. If you don't know what I'm talking about, ask, I'll send you a pic and some instructions.

When setting up the dies, I try to get a handful of cases that close tighter than the others. When you size a case, the die begins contacting the walls of the case long before the shoulder gets bumped. This will cause the headspace of the case to grow very slightly. So if you size the same case over and over as your stepping the die down, you will notice that at some point the bolt will be harder to close than when you started. This is when i grab another case from the batch, step the die down the next increment, and size it. For me, the thrid case usually goes into the die once and is correct. Then I take several more cases and size them, to confirm that they all chamber with the resistance I like.


Edited: I wouldn't shoot the undersized ammo. You can say what you like about head separations, but simply hoping that the separated webb section continues to seal the chamber is just crazy. Just because some of you have gotten away with it, doesn't make it right. If it doesn't seal, very bad things can happen. Oneshot, I think when your brother says he wants you to learn the hard way he means trashing a few pieces of brass, not losing an eye. Go buy yourself some new brass, as a new-ish reloader, you have other things to worry about than trying to make your setup work on other peoples throw away brass.
 
Re: Primers backing out...

Thank you for the added information but doesn't the firing pin cock as you "open" the bolt???

I'm not really using other people's throw away brass. It's all my brass from other rifles... Collected for about 15 years. I got tons of it!. Anyway, I used my Brother's Case Length Gauge as well as closing the bolt on sized brass to get what I think is now a good fit. I'll load 10 and try them before continuing.

I'll be pulling the bullets from the loaded brass I have and chucking it. I don't need a case-head seperation. Thanks again for the information!

John
 
Re: Primers backing out...

Yes it does, but all of the spring pressure from the firing pin is trying to press the bolt to the rear. This is the resistance you feel while closing a bolt on an empty chamber. with the firing pin, spring, and shroud removed, the bolt will fall closed on an empty chamber.

Some people take it a step further and remove the ejector as well since it presses the bolt backwards when a case is in the chamber adding to some of the closing force. I think I have sufficient feel leaving it in so i don't go that far.
 
Re: Primers backing out...


And...if you REALLY want to save the brass...pull the bullets, save the powder. Use a .338 or above Hornady (or other tapered) expander ball and expand the necks to .333 or above. Be sure to wire brush the insides of the necks and lube them with resizing lube before expanding. Size them down properly in your .308 die. You will have created a "false" shoulder. Charge and shoot them. You'll be okay. JMHO
 
Re: Primers backing out...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: former naval person</div><div class="ubbcode-body">
And...if you REALLY want to save the brass...pull the bullets, save the powder. Use a .338 or above Hornady (or other tapered) expander ball and expand the necks to .333 or above. Be sure to wire brush the insides of the necks and lube them with resizing lube before expanding. Size them down properly in your .308 die. You will have created a "false" shoulder. Charge and shoot them. You'll be okay. JMHO </div></div>

+1
 
Re: Primers backing out...

You have figgered it out, your cases are indeed over-resized for your chamber AND the load is a bit too light.

No primer can back out unless there is too much "headspace", chamber slop. To a reloader, that doesn't really matter, we just custom resize to match the chamber. To us, all head space means is the room in the chamber for the cartridge; if we can't close the action the case is too large (not enough chamber headspace), if the cartridge is a rattle fit, as your's clearly is, the cartridge is too small (too much chamber headspace).

Most highly flattened primers are due to what you're doing plus a normal pressure load. The primer blast backs it out, normal chamber pressure then pushes the case head toward the bolt face and reseats the primer, but it may have to squish the primer cup flat as a pancake to do so.

When checking flattened primers as signs of high pressure one has to first consider if the cases were properly resized, they will "lie to you" if not. Your case's are overly resized.

There is no reason to discard your ammo, shoot it. The (excellant) rifle is safe and the fired cases haven't really been harmed.
 
Re: Primers backing out...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: former naval person</div><div class="ubbcode-body">
And...if you REALLY want to save the brass...pull the bullets, save the powder. Use a .338 or above Hornady (or other tapered) expander ball and expand the necks to .333 or above. Be sure to wire brush the insides of the necks and lube them with resizing lube before expanding. Size them down properly in your .308 die. You will have created a "false" shoulder. Charge and shoot them. You'll be okay. JMHO </div></div>

Thats not for me but it's very clever, I like it!
 
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