Excessive bump required on max pressure load?

[sacklunch]

Got a few cases from a pretty hot load. Wasn’t ideal to fire form virgin brass with that load, it was showing pressure signs, but nothing dangerous.

That said, would a case that had ejector swipes, in theory allow that shoulder to expand more on the chamber as that case is pushed back into the bolt enough to have swipes?

Reason I ask, bumped those shoulders back my standard .003 and those cases are tough to close the bolt on. Ended up having to bump .006 back to get them to chamber.

Won’t continue with that load and get back to not over working the brass on the next firing, just curious what may explain the need for an excess bump?

TIA

 

[BobinNC]

You don't say what round or brass your using, or what firearm is leaving ejector swipes. But I would expect you should see a head separation from that brass in the near future.

Basically anytime you have trouble chambering once fired brass that was fired in the same rifle, you might have a problem somewhere. Yes, brass does spring, but unless you have an excess something, somewhere, I would look to your chamber, action (rear locking lugs problems, not too common nowadays) or your dies, or your bullet seating for potential chambering problems.

Do you have any Sheridan Slotted Gauges?? They are very helpful at modest cost to diagnosing brass sizing problems.

Sheridan Gauges

As a further note: I don't use traditional FL or Neck Sizing Die sets. I buy a Lee Collet Neck Sizing Die for neck sizing only, a Redding Body Die for body sizing and shoulder bumping as needed, and then any good Micrometer Bullet Seating Die (Forster or RCBS MatchMaster are my favorites). I also often use a modest neck belling die for non-boattail bullets for proper bullet seating without bulging the case that can sometimes happen. And later a Lee Factory Crimp Die to later remove the bell even if I don't use it for a full on crimp.

The Sheridan Slotted Gauge is very useful for all these instances.

 

[sacklunch]

New barrel/chamber, this was the first 50 down it, 6 creed, Lapua virgin brass. Headspace checked before and after, go/no-go used. Dies are SAC bushing, so is the seater die. This isn’t a loaded round. I’m just referencing the sized brass not wanting to chamber. Checked the shoulders on the never fired Lapua, I had to bump back to .003 or the virgin brass to get it to chamber easily. I could close the bolt .005 over virgin brass but it was tough. That fire formed shoulders pushed out almost .010 over their virgin size. Haven’t seen that before and attributed it to the slightly over pressure load…

so back to the original Q…can a hot load pushing a case rearward into the ejector enough to swipe give the shoulder excess space to move forward on firing?

 

[BobinNC]

I'm assuming you mean 6mm Creedmoor. Minimum Brass and Maximum Chamber (both within spec BTW) that won't be detected by a go/no go gauge can cause also problems like you describe. How did you check headspace before and after and come up with a .006 shoulder bump to chamber?? Maybe your die wasn't getting cartridge waist sized correcting resulting in a excess shoulder bump as you set the die down further so your brass could now chamber. (Again assuming your using some sort of a FL Die)

So now I know the brass (I think), what dies are you using, what rifle: as in what action, barrel, and who chambered it, custom or off the shelf??

These questions are academic in diagnosing chambering problems.

 

[sacklunch]

I’ve used these dies on my other 6 creed, same Lapua brass, zero issues. Doubt it’s a SAC die issue, or a case issue. Based on the gauges. It’s not a chamber issue.

Asking again, is there scenario where excess pressure can push that case rearward into the ejector enough to swipe giving the shoulder to push forward more than a firing with a less than max load? I don’t understand all the variables that can go into it, but if headspace checks, then it seems like a potential cause.

Should I have just loaded up a dummy round after originally bumping my usual .003? Was my error in checking empty brass to see if it would change?

I ran a go/no-go down it after I noticed I needed to bump .006 to get that empty brass to easily chamber. Basically needed to be numbed back to .003-.004 over the unfired shoulder measurement. Go/no-go checked fine.

bighorn origin, proof pre fit. SAC dies, mentioned in previous post.

 

[BobinNC]

No you edited your post while I was responding to it. Your original reply told me very little about the action barrel or dies..

In any event is the SAC Die a FL sizing die? Yes or No?

It's pre-fit barrel and again a go/no go gauge will tell you diddly about maybe having a SAMMI max chamber coupled with a SAMMI minimum die.

While your checking headspace, I'm talking about where the pressure ring on the case is located, just above the ejector grove. FL length dies also have to size that area, and that area is well below the shoulder. To reach a bulged case (yes, from high pressure or a max chamber) to resize the pressure ring you have to set your FL dies deeper, which also bumps the shoulder back more.

Hence why I use a neck sizer and a separate body die, to avoid such problems usually caused by oversized chambers (but within spec) or undersized dies (within spec).

That's why I recommend the Sheridan Slotted dies as you can visually see exactly where you need to size.

You can also send your fired cases off to Redding and other dies makers to build you a die to minimize working the brass for that particular rifle

 

[sacklunch]

No you edited your post while I was responding to it. Your original reply told me very little about the action barrel or dies..

In any event is the SAC Die a FL sizing die? Yes or No?

It's pre-fit barrel and again a go/no go gauge will tell you diddly about maybe having a SAMMI max chamber coupled with a SAMMI minimum die.

While your checking headspace, I'm talking about where the pressure ring on the case is located, just above the ejector grove. FL length dies also have to size that area, and that area is well below the shoulder. To reach a bulged case (yes, from high pressure or a max chamber) to resize the pressure ring you have to set your FL dies deeper, which also bumps the shoulder back more.

Hence why I use a neck sizer and a separate body die, to avoid such problems usually caused by oversized chambers (but within spec) or undersized dies (within spec).

That's why I recommend the Sheridan Slotted dies as you can visually see exactly where you need to size.

You can also send your fired cases off to Redding and other dies makers to build you a die to minimize working the brass for that particular rifle

I’m not going to argue with you about whether or not I replied to your post and told you it was a 6 creed and SAC dies. Let it go. I’ll pass on Redding, it’s not a die issue, as stated, these dies have been used for rounds in my target rifle with great results. No pressure ring anywhere on the case, nothing noted inside by the head with a paper clip either.

I’ve asked the question 3 times now, very specifically if you don’t know the answer, that’s fine. You keep hinting and hoping At issues that aren’t issues. It’s not a die issue. It’s not a headspace issue and it’s not poor quality brass.

The original question was pretty straight forward…I didn’t ask about dies, your process or anything else. I simply asked CAN an over pressure load pushing a case back into the bolt face hard enough to leave ejector swipes then leave room in that chamber for the shoulder to press forward more. Or, can a max pressure load lead to longer shoulder measurements than a lower pressure round.

The over-bumping could have easily been user error, should have probably loaded up a dummy at a .003 bump and see if it chambered, I went with empty brass instead and needed to bump more for the bolt to close easily.

 

[Ex E6]

I’m not going to argue with you about whether or not I replied to your post and told you it was a 6 creed and SAC dies. Let it go. I’ll pass on Redding, it’s not a die issue, as stated, these dies have been used for rounds in my target rifle with great results. No pressure ring anywhere on the case, nothing noted inside by the head with a paper clip either.

I’ve asked the question 3 times now, very specifically if you don’t know the answer, that’s fine. You keep hinting and hoping At issues that aren’t issues. It’s not a die issue. It’s not a headspace issue and it’s not poor quality brass.

The original question was pretty straight forward…I didn’t ask about dies, your process or anything else. I simply asked CAN an over pressure load pushing a case back into the bolt face hard enough to leave ejector swipes then leave room in that chamber for the shoulder to press forward more. Or, can a max pressure load lead to longer shoulder measurements than a lower pressure round.

The over-bumping could have easily been user error, should have probably loaded up a dummy at a .003 bump and see if it chambered, I went with empty brass instead and needed to bump more for the bolt to close easily.

Generally speaking IF a pressure issue is great enough ,the shoulder flows through the neck . That's not to say an over pressured case won't pound back into bolt extractor . Check case OAL length after extracting case from chamber ,before sizing or bumping shoulder If you have another unsized case or not shoulder bumped as yet . Lube it place it in the FL sizing die stroke it home and return it , Now turn case 180 Deg. appx. and send it home again . DID this solve the issue ?.

 

[sacklunch]

Generally speaking IF a pressure issue is great enough ,the shoulder flows through the neck . That's not to say an over pressured case won't pound back into bolt extractor . Check case OAL length after extracting case from chamber ,before sizing or bumping shoulder If you have another unsized case or not shoulder bumped as yet . Lube it place it in the FL sizing die stroke it home and return it , Now turn case 180 Deg. appx. and send it home again . DID this solve the issue ?.

thanks.

I don’t have any once fired left that I didn’t resize (just did 50) already.

I did measure the resized and brass to the virgin brass and case length hasn’t changed…exactly 1.912 on both virgin and resized, checked on multiple pieces.

 

[BobinNC]

Listen I never said it was just a die issue. If it's not a headspace issue why are you setting your shoulder back .006"? I never intimated that your brass was ever an issue.

Headspace is the distance between the face of a firearm's bolt and a specific point in the chamber. For bottlenecked rimless cartridges headspace is measured from the chamber's shoulder to the bolt face.

For the 6mm Creedmore your shoulder headspace is 1.5438 -0.007 at -0.006 your pretty close to max set back. Because you don't have any problems with your other 6mm Creed chambers with this brass and with these dies point to a chamber problem on that rifle only, and not the brass or the dies per say. It's a rifle chamber issue IMHO.

I have no idea how much you know or don't know about reloading. You first cryptic post yielded questions. I explained my process and why I did so.

And now for my final answer: Could just high pressure cause a .006 need for a shoulder bump?? No I don't think so. Which is what I was saying all along. You just didn't listen.

 

[sacklunch]

Listen I never said it was just a die issue. If it's not a headspace issue why are you setting your shoulder back .006"? I never intimated that your brass was ever an issue.

Headspace is the distance between the face of a firearm's bolt and a specific point in the chamber. For bottlenecked rimless cartridges headspace is measured from the chamber's shoulder to the bolt face.

For the 6mm Creedmore your shoulder headspace is 1.5438 -0.007 at -0.006 your pretty close to max set back. Because you don't have any problems with your other 6mm Creed chambers with this brass and with these dies point to a chamber problem on that rifle only, and not the brass or the dies per say. It's a rifle chamber issue IMHO.

I have no idea how much you know or don't know about reloading. You first cryptic post yielded questions. I explained my process and why I did so.

And now for my final answer: Could just high pressure cause a .006 need for a shoulder bump?? No I don't think so. Which is what I was saying all along. You just didn't listen.

I’m not convinced there the issue either, as mentioned. I think a seated round would have shown ability to chamber or not much better then empty brass. Could have. Been part of my issue. The bolt would close on empty brass, it just wasn’t smooth and felt forced.

could be user error, as I stated. Never had an issue before, but honestly haven’t checked chambering after bumping shoulders u til that round was loaded. Could have easily talked myself into over bumping the shoulder when it wasn’t required. I’ll fire this 50 off and check the brass for any head sep signs and if they look good, will check the next loading with a loaded round after a more normal .003 bump. If net the same results, I’ll dig into chamber issues. Right now, I just wanted to rule out it was my own doing.

Also, wanted to inquire if brass can grow at the shoulder due to an over pressure load pushing back to the bolt face harder…since it doesn’t appear that brass grew at the neck even .001 longer after resizing.

 

[Ex E6]

thanks.

I don’t have any left of those once I feed that I didn’t resize (just did 50).

I did measure the resized and brass to the virgin brass and case length hasn’t changed…exactly 1.912 on both virgin and resized, checked on multiple pieces.

OK ; Understood . Checking OAL after firing is telling with excessive pressure signs ,as is shoulder to base measurement . IF those two measurements are reasonable then it's Case Bulge . Unfortunately can't tell anything after resizing . So Next time check Before resizing .

A clue is automatic gas guns ,such as SAW's M249 or older M60's . Faster rate of fire more heat and case stretch shoulder same lot of cases could vary .007 or more .
I resized #600 7.62X51 and had to run each one #3 times through the FL sizing die ,so as to get case bulge fixed .

Bolt rifles DON'T have those issues ,until excessive pressure shows up . Be careful 30-100 fps isn't gonna make or break accuracy ,as a matter of fact 98% of accurate weapons run 1-2 grains under maximum load . I've been pulling the handle going on 59 years and have seen more than a couple of things . Including a super tight grouping of #15 shots at 200 meters ,with SD in excess of 100 fps .

 

[sacklunch]

OK ; Understood . Checking OAL after firing is telling with excessive pressure signs ,as is shoulder to base measurement . IF those two measurements are reasonable then it's Case Bulge . Unfortunately can't tell anything after resizing . So Next time check Before resizing .

A clue is automatic gas guns ,such as SAW's M249 or older M60's . Faster rate of fire more heat and case stretch shoulder same lot of cases could vary .007 or more .
I resized #600 7.62X51 and had to run each one #3 times through the FL sizing die ,so as to get case bulge fixed .

Bolt rifles DON'T have those issues ,until excessive pressure shows up . Be careful 30-100 fps isn't gonna make or break accuracy ,as a matter of fact 98% of accurate weapons run 1-2 grains under maximum load . I've been pulling the handle going on 59 years and have seen more than a couple of things . Including a super tight grouping of #15 shots at 200 meters ,with SD in excess of 100 fps .

I did check base to shoulder after they were fired, before resizing…virgin brass was .007 to .009 shorter. One shoulder was .010 over the virgin measurements. But, that isn’t taking the variations in virgin brass shoulder measurements into effect, if there is much (any) variation in Lapua brass…mine seem to measure within .002 of eachother in their unfired form.

Is that .007-.009 shoulder expansion excessive? Assuming yes. If so, potentially caused by over pressure or is it more indicative of a chamber issue?

 

[sacklunch]

OK ; Understood . Checking OAL after firing is telling with excessive pressure signs ,as is shoulder to base measurement . IF those two measurements are reasonable then it's Case Bulge . Unfortunately can't tell anything after resizing . So Next time check Before resizing .

A clue is automatic gas guns ,such as SAW's M249 or older M60's . Faster rate of fire more heat and case stretch shoulder same lot of cases could vary .007 or more .
I resized #600 7.62X51 and had to run each one #3 times through the FL sizing die ,so as to get case bulge fixed .

Bolt rifles DON'T have those issues ,until excessive pressure shows up . Be careful 30-100 fps isn't gonna make or break accuracy ,as a matter of fact 98% of accurate weapons run 1-2 grains under maximum load . I've been pulling the handle going on 59 years and have seen more than a couple of things . Including a super tight grouping of #15 shots at 200 meters ,with SD in excess of 100 fps .

I was in a hurry and took a middle node from someone off QL…turned out to be a bit hot. Pressure wasn’t excessive but hotter than I’d normally shoot. Finished the 50 pieces and dropping charge weight down a a full grain and finishing break in.

Got a bit tired of blowing through 200 pieces off brass to work up a load, wanted to just push this close to max as it’s intended to be a hunting rifle only and needed to push it as close to 3k as I can.

 

[Ex E6]

I did check base to shoulder after they were fired, before resizing…virgin brass was .007 to .009 shorter. One shoulder was .010 over the virgin measurements. But, that isn’t taking the variations in virgin brass shoulder measurements into effect, if there is much (any) variation in Lapua brass…mine seem to measure within .002 of eachother in their unfired form.

Is that .007-.009 shoulder expansion excessive? Assuming yes. If so, potentially caused by over pressure or is it more indicative of a chamber issue?

The ONLY way to know for absolute certainty is to Slug Your chamber ,that way You have an absolute BASE LINE measurement .

Speaking from Gas gun perspective ,I run .004+ shoulder set back . On Bolt guns unless hunting I'm .002 ,hunting is Minimum .004" when it counts no sense fooling with close tolerances . Had a BAD experience ONCE .

I'm NOT certain of the term virgin brass ,as it's meaning is too vague . I have factory ammo which is far under dimensions of which I can recreate reloading . Around .050" from the base up the case diameter is smaller than I can squeeze it back too . Ammo is a general fit all chamber ,so their smaller than reloading Die spec. So hopefully You see where I'm going with Virgin brass .

ALL virgin brass NO primers should be run through the reloaders dies and set appropriate to one's chamber ,IMO .

I reloaded some 7RM for a hunting trip several decades ago and built some super accurate rounds ,I also gave some to My hunting partner . I used a Commercial Mauser 3KL and he had a BAR Browning semi auto . Bottom line MY reloads wouldn't fit his chamber .
Taught ME a valuable lesson MEASURE AND VERIFY .

Those reloads were so precise ,I actually cut the targets wire hangers at 300 yd. on purpose with #3 shots missed second time .

Lapua is some of the Top line brass ,as I said measuring all aspects Before and After tells the story but knowing chamber dimensions is PARAMOUNT for comparison purposes .

 

[Ex E6]

I was in a hurry and took a middle node from someone off QL…turned out to be a bit hot. Pressure wasn’t excessive but hotter than I’d normally shoot. Finished the 50 pieces and dropping charge weight down a a full grain and finishing break in.

Got a bit tired of blowing through 200 pieces off brass to work up a load, wanted to just push this close to max as it’s intended to be a hunting rifle only and needed to push it as close to 3k as I can.

Save Yourself TIME and AMMO . Load #5 rounds of an upper end charge ,#5 of a charge 1.0 gr. less and another #5 in between those charges . Same day same target with multiple aim points then group them . YOU will then KNOW where your accuracy lies and can fine tune OAL along with 1/10 gr. increments . I personally prefer Min. on Gas guns 20 K Bolt guns NO less than 10 K . I'm NOT BR shooting either so .

IF You get better accuracy at lower end charge drop it by another 1/2 gr. and experiment in that vicinity . Some guns just don't like Max velocity .

 

[Ex E6]

Don't know how or why I missed making one final point concerning pressure signs , so here it is time tested in memorial from the

Ballistician's . Using a 1" micrometer preferably with balls , measure any case just ahead of the extractor groove ,rebated rim or belted cartridge . Best done BEFORE firing ,then again AFTER firing . IF you see anything in excess of 1/2 K expansion YOU have EXCESSIVE PRESSURE . Known as Radial expansion ,it precedes case head separation . Carry On .