Brass shows pressure signs with age?

[71firebird400]

Hi,

This is somewhat of a boneheaded question, but I can't wrap my head around what is going on here.

Went out and shot some loads several months ago with once-fired Lapua brass (it had been fired as brand new Lapua ammo through my rifle). Worked my way up to max load and it extracted fine.

Now, with each subsequent firing the brass has become more difficult to extract. It is clearly showing pressure signs that I would normally deem unsafe. I am full length sizing, and after sizing the cases will chamber completely fine with no resistance. Primers still look the same as they always did (slight cratering, but not flattened). I just recently went shot the fifth resizing of this load (sixth firing on the brass) and it has gotten to the point where I'm no longer comfortable with shooting it like this.

Throughout all reloading I've been using the same lot # of powder, along with the same scale, and same cartridge OAL. As far as I can tell, nothing has changed.

Anybody have any ideas on what's going on? This is a hotter load (book max) but like I said it appeared to be working perfectly fine at first; it's just the last couple of firings that have progressively gotten worse.

I purchased some new brass a couple days ago and plan on loading up some with the aforementioned load. I will post if it extracts fine, or if it is problematic. I suppose that will somewhat answer my question as to whether the brass is to blame; but even then I've never seen anything like this in my other calibers.

 

[Kevlars]

Re: Brass shows pressure signs with age?

How many firings has your brass had? Have you anealed it at all?

 

[71firebird400]

Re: Brass shows pressure signs with age?

On the sixth firing, no annealing.

I was hoping for close to 10 reloads for case life; this hasn't been a problem in my other calibers (where I don't anneal).

Thanks

 

[memo43]

Re: Brass shows pressure signs with age?

From what you said I can think of two things.

1. you say its a hot load (book max) what was the temp wen you first fired it, and has the temps gotten hotter. High temps equal higher pressure.

2. You are resizeing them, but are you bumping shoulders back, trimming them.
What powder are you useing and how is your seating depth, if you are jaming them and its getting warmer them yes sticky bolt, stiff bolt are signs of pressures. Not necessarily brass issue, but think bigger picture.

 

[71firebird400]

Re: Brass shows pressure signs with age?

Hey-

Similar temps throughout the entire winter (30-50 degrees) and I'm using Hodgdon Retumbo. I am bumping shoulders several thousandths, but not drastically. Cases are trimmed each reloading.

Seating depth has remained consistent at .020" off the lands.

 

[MitchAlsup]

Re: Brass shows pressure signs with age?

You say you are FL resizing the cases. What are you using to measure the sholder position?

The reason I ask is that one needs to be able to measure the sholder position in order to K.N.O.W that the die is set up correctly. Otherwise it might just be close enough for a few cycles, but not good enough for a long haul.

 

[gcoulsey]

Re: Brass shows pressure signs with age?

Is your chamber clean?
Crap in the chamber can cause the pressure signs, and 'grip' the case on extraction enough to feel resistance.

Try cleaning/polishing the chamber?

Just an alternative thought

 

[71firebird400]

Re: Brass shows pressure signs with age?

Mitch-

I use the Redding Comp Shellholders to set shoulder bump and it is sufficient. I FL size every time, the same amount and they are chambering just fine so I don't think it is a sizing issue unless I'm overlooking something?

UK-

I had kind of thought about this but the difference in extraction that I'm seeing is quite drastic. Regardless, I cleaned the gun just recently to see if it makes a difference. I usually go a while between cleaning my rifles so it is plausable that it had a 'dirty' chamber.


Thanks

 

[Bacarrat]

Re: Brass shows pressure signs with age?

What are you using to measure your bump when you resize the case? Shell holders will only do so much, you can still crank down on the die to give you more space for the case to move around in.

 

[71firebird400]

Re: Brass shows pressure signs with age?

Bacarrat-

I worked my way up from the -.010" shell holder on several resized cases. Chambering the rounds was difficult, so I bumped up to the -.008", and so on until I ended up at the -.004". Cases chamber just as easily as factory ammo, so I assumed the shoulder was bumped far enough back to ensure reliability without overworking the brass.

Zak Smith suggested this as a way to 'minimally' resize the cases and the logic makes sense to me. If you think this is a problem I can run the cases through the die using the conventional shell holder, but I really don't see how that would make a difference. But like I've said, I'm open to any suggestions and if I'm doing soemthing wrong I'd be glad to know what it is!

Thanks again.

 

[damoncali]

Re: Brass shows pressure signs with age?

I'm not sure if this is your problem, but I've found the RCBS precision mic's to be pretty handy for diagnosing this sort of thing. Use them to measure the case before & after sizing and after firing. It really helps you see exactly what's going on. A wilson-style gage will do the same thing for less money, but it's not quite as slick.

 

[71firebird400]

Re: Brass shows pressure signs with age?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: damoncali</div><div class="ubbcode-body">I'm not sure if this is your problem, but I've found the RCBS precision mic's to be pretty handy for diagnosing this sort of thing. Use them to measure the case before & after sizing and after firing. It really helps you see exactly what's going on. A wilson-style gage will do the same thing for less money, but it's not quite as slick.
</div></div>

Thanks for the heads up, I was planning on picking up a set of the LE Wilson gauges but I'll take a look at the RBCS.

I was under the impression that if the rounds chambered fine that the shoulder had been bumped as much as was needed. Will a lack of headspacing clearance cause my issue? Like I've said before, the problem of difficult extraction gets worse with each consecutive firing. With the first through third firing it wasn't a problem; it began to appear on firing number 4 and has continued to worsen.

 

[Bacarrat]

Re: Brass shows pressure signs with age?

How much do you have the die adjusted down on to the shell holder when you have the ram all the way up? The shell holders are not going to stop the ram from going up, you still can oversize the case. You need something like the RCBS precision mic or something that can measure the datum point on the shoulder of the case. That way you truly know how much you are pushing the case back.

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[71firebird400]

Re: Brass shows pressure signs with age?

I have my press set up so that the ram just touches the bottom of the die at the top of the stroke; per Forster's instructions.

If I measure the headspace I'll have a number, but I fail to see how that will solve the problem. If this was happening with every resizing of the cases I'd agree that I'm possibly not bumping the shoulders back far enough, but it only is showing up after multiple firings/resizings so I don't see how it can be related?

Thanks

 

[damoncali]

Re: Brass shows pressure signs with age?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 71firebird400</div><div class="ubbcode-body">
Thanks for the heads up, I was planning on picking up a set of the LE Wilson gauges but I'll take a look at the RBCS.

I was under the impression that if the rounds chambered fine that the shoulder had been bumped as much as was needed. Will a lack of headspacing clearance cause my issue? Like I've said before, the problem of difficult extraction gets worse with each consecutive firing. With the first through third firing it wasn't a problem; it began to appear on firing number 4 and has continued to worsen.

</div></div>

I honestly don't know what's wrong. What your'e doing sounds right - bumping the shoulders until it chambers easily. The precision mic will make that process a little easier and may get you a slightly better tolerance, minimizing the required sizing. You can measure each case before and after sizing, and know exactly how much it's being worked.

My gut says your load is a little too hot. Otherwise, I'd just be speculating.

 

[MitchAlsup]

Re: Brass shows pressure signs with age?

OK, so we have the situation where there is evidence that the shoulder is in the correct position after being full length resized and still have chambering issues (and chamber is clean).

Suggest you take a case that still has chambering problems and color it with a majic marker and then chamber it. The offending spot on the case will show up (by removing the majic marker marks) in the area of mal-sized-ness. Could be sholder, could be down at the web, or could be up at the neck.

 

[71firebird400]

Re: Brass shows pressure signs with age?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MitchAlsup</div><div class="ubbcode-body">OK, so we have the situation where there is evidence that the shoulder is in the correct position after being full length resized and still have chambering issues (and chamber is clean).

Suggest you take a case that still has chambering problems and color it with a majic marker and then chamber it. The offending spot on the case will show up (by removing the majic marker marks) in the area of mal-sized-ness. Could be sholder, could be down at the web, or could be up at the neck. </div></div>

Mitch-

All cases chamber fine (after being resized), it's after they're fired they become difficult to extract. Regardless, I'll go mark one up because it probably would be beneficial to see where it's making contact.

 

[cali_tz]

Re: Brass shows pressure signs with age?

I have the same problems with my 338 LM.

I know my loads are hot, but on brass that I fired from unprimed virgin brass (Lapua and Hornady) the cases did not stick coming out. On the exact same loads, but on 1x fired brass off the web (Lapua), which I full length resized (measured using Hornady and Sinclair tools for shoulder length) and also fit fine on chambering the round, but after firing the bolt took noticeable effort to open.

I will measure the brass to see what's exactly going on with respect to my other brass that came out easy after firing. But it's odd... the primer is not really flattened, just a little on some rounds.

What is the main cause of the bolt being hard to open... which part of the brass is pushing against the chamber... must be the main body right?

Is the brass ruined at this point or can you full size reload and go again?

 

[damoncali]

Re: Brass shows pressure signs with age?

The theory is that brass deforms plastically (permanently) while the chamber is is under pressure. When the chamber snaps back, the now bigger brass is a snug fit and gets stuck in the chamber.

Likewise, if brass lengthens permanently to the point where the bolt and barrel snap back and compress it, you'll have a tough time opening the bolt.

It sounds reasonable to me, but I've not verified this with calculations or testing of any sort.

 

[MitchAlsup]

Re: Brass shows pressure signs with age?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: damoncali</div><div class="ubbcode-body">The theory is that brass deforms plastically (permanently) while the chamber is is under pressure. When the chamber snaps back, the now bigger brass is a snug fit and gets stuck in the chamber.</div></div>

Given 71Firebird400's response above, I tend to believe the above paragraph is explanatory. Once pressure is above the palstic point of the brass, the brass flows. IF the pressure is above ~58K PSI for long enough, the brass ends up with no memory and thus has no springback and will be difficult to extract.

Which gets back to a different question:: What is the load recipie that is doing this to that brass?

 

[71firebird400]

Re: Brass shows pressure signs with age?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MitchAlsup</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: damoncali</div><div class="ubbcode-body">The theory is that brass deforms plastically (permanently) while the chamber is is under pressure. When the chamber snaps back, the now bigger brass is a snug fit and gets stuck in the chamber.</div></div>

Given 71Firebird400's response above, I tend to believe the above paragraph is explanatory. Once pressure is above the palstic point of the brass, the brass flows. IF the pressure is above ~58K PSI for long enough, the brass ends up with no memory and thus has no springback and will be difficult to extract.

Which gets back to a different question:: What is the load recipie that is doing this to that brass? </div></div>

Mitch-

This is a factory max load (94gr of Retumbo behind a 300 grain Sierra Match King); but it is not out of the question that I am over powering the brass causing it 'permanent' damage. In fact, that would explain the scenario quite well and was something I was unaware of. I assumed that I'd be safe by sticking to factory loads, but then again I suppose there's a difference between operating at a safe pressure for the action and a friendly pressure for the brass and the fact is that 338LM is a rather high pressure cartridge.

I'd still like some reassurance that this is a plausible scenario, but it sounds believable to me.

Thoughts?

Thanks again everyone.

 

[cali_tz]

Re: Brass shows pressure signs with age?

Interesting... I am also using 94.0gns of Retumbo, Lapua brass, and with 300gn Scenar. I will take detailed measurements of the brass and see what is going on here... like I said I have used this load before and it did not cause the bolt to stick on brass that only my rifle has fired.

 

[71firebird400]

Re: Brass shows pressure signs with age?

I talked to someone who has forgotten more about reloading than I'll ever know and he is fairly confident that I am not sizing the cases enough around the base. I marked a fired case with a sharpie, chambered and extracted it, and sure enough the marker is nearly rubbed off about .25" above the extractor groove.

With that said, I'm going to try a couple of things using my existing die but if that doesn't work then I will be having either Redding or Forster build me a custom FL die.

Thanks for everyones help, I'll report back once I have a chance to give this theory a test (but I'm convinced this is it).

 

[YAOG]

Re: Brass shows pressure signs with age?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 71firebird400</div><div class="ubbcode-body">I talked to someone who has forgotten more about reloading than I'll ever know and he is fairly confident that I am not sizing the cases enough around the base. I marked a fired case with a sharpie, chambered and extracted it, and sure enough the marker is nearly rubbed off about .25" above the extractor groove.

With that said, I'm going to try a couple of things using my existing die but if that doesn't work then I will be having either Redding or Forster build me a custom FL die.

Thanks for everyones help, I'll report back once I have a chance to give this theory a test (but I'm convinced this is it). </div></div>


Ah, I see you got to where I was going. You need to get a Hornady LNL headspace and their bullet comparator gauge kit (or something like it but AFAIK this is the only one that works using common 0.001" 6" calipers) to use on a good set of calipers. This is the cheapest way to confirm your fired and resized cases are dimensionally where you think they are and a will confirm your shoulder DL dimensions. Unless you have a way to measure your case shoulder DL and ogive you really have no idea where you are only that you think you bumped the shoulder back and that the bullets are some length overall. Without measuring tools you don't know with any certainty and are just guessing. As your friend suggested I suggest that you also measure some factory loaded rounds at the base of the web using the SAAMI prints to find the minimum dimension and how high up from the base to take that measurement. Compare the factory loaded round to some of your "full length sized" cases and your loaded and fired cases to see what you have going on.

This problem sounds like a sizing issue due to bumping around in the dark without getting any measurements to me.

 

[71firebird400]

Re: Brass shows pressure signs with age?

YAOG-

Yes, definitely a lot of bumping around since Midway has had the LE Wilson headspace gauge backordered for months now!

I actually took the time to measure my Redding competition shellholders tonight; I don't know how familiar you are with them but anyways I determined that the +.002" shellholder is actually holding the case .007" further out of the die than a standard shellholder. I should have known better, but I made the incorrect assumption that Redding could accurately machine shellholders.....

With that said, I took 3 sized brass and ran it through my die again using the normal Redding No. 35 shellholder. Just by the feel of the press you could tell quite a bit more of resizing was taking place. I loaded up these three cartridges with the troublesome load and will hopefully shoot them tomorrow. If my theory is correct I'm hoping that they will extract fine with no signs of pressure. I'll let you know.

But yeah, you're right....I really need to get a headspace gauge to truly determine what's going on here. Maybe I'll order the Hornady you speak of.