Shoulder Bump Question

[biologicole]

I have a question about shoulder bump. I believe I may have bumped the shoulder back too far on my .260 Rem reloads. A little background...I received a batch of brass with too large of primer holes and had primers dropping out of the reloaded cartridges as well as falling out of fired cartridge. I acquired a primer pocket gauge and sorted them all out, I think. Here's the problem, after sorting out the large primer pockets, I reloaded the remaining brass. However, I recently shot a deer and had the spent primer fall out of the case. The headspace on the gun has been checked and is correct. I'm absolutely sure the powder charge is isn't excessive and causing pressure problems. I'm wondering if I bumped back the shoulder too far creating excessive headspace and if that's even possible? Would that cause the primer to fall out? Can I use a headspace gauge to check that on loaded ammo? Thanks

[lugerstew]

Wow that doesn't sound right to me, was the brass you got new or been fired several times?
Do you own a headspace comparator? Do you have some brass that has been fired from that gun and not resized yet? So, you can compare the fireformed brass to your sized brass to see how far the loaded brass is set back compared to your actual chamber size.

[tangolima]

The brass metal could be too soft. It could have been improperly annealed previously. It could be out of spec new out of factory. I had a box of factory ammo doing that.

Retire it to the recycling bin and get another batch.

-TL

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[biologicole]

It was new Remington brass. The current reloads are on their second (maybe third) reloading. I don't have a headspace comparator but I'm looking at acquiring a Sheridan headspace gauge or Lyman ammo checker. I may have some fired brass but I think I resized, trimmed and primed all my brass last Fall and reloaded 100 for deer hunting. I'd like to be able to check the loaded ammo. It should all be the same, but, things happen. If I did bump the shoulder back too far and create too much headspace I don't want to shoot any more of them.

[Unclenick]

Expanding primer pockets is one of the standard high-pressure signs. You said you are absolutely sure the powder charge is OK, but "absolutely" is a very hard standard to meet when differences in bullet designs of the same weight have been shown to cause up to 30% variation in pressure, the high-pressure ones needing lower charge weights than the lower pressure ones. Seating a bullet in or too close to contact with the bore throat can raise pressure 20% and require about 10% less powder, and too deep can cause a pressure problem, too. If you set the shoulder back too far too many times and are using a bullet whose bearing surface (the cylindrical full OD portion) seats down as far as the bottom of the neck, you could have an internal donut formed that is pinching the bullet and preventing it from being freely released, which raises pressure. So if you have a bullet that isn't the one used in your load data or you have one of the other load conditions I mentioned, your powder charge could, indeed, still be too high despite following the book.

Here's a photo of a sectioned case that had been reloaded many times. It has an internal donut, but you can see from the reamer marks inside the rest of the neck that it had previously been reamed internally, probably to remove another donut.

[biologicole]

Thanks, Unclenick. Maybe I’m over thinking this. I didn’t have any problems in load development and followed the Barnes reloading guide to work up my powder charge. I stopped at 1.8 gr below max and weigh powder on two separate scales before pouring into case. Length is 0.06” off lands as measured by Hornady OAL gauge. I set shoulder bump by inserting into chamber and setting back resting die 1/4 turn until there’s minimal or no resistance on bolt closure. I’m wondering if I somehow missed a defective primer pocket or did something to the resizing die and set back my shoulder too far. If I did set back the shoulder too far, would it create excessive headspace and blow a primer?

[lugerstew]

biologicole
Just wondering, did the primers fall out of this new Remington brass on the very first reloads, or did they start falling out after loading them several times?
You did say the primers fell out on the loading bench when they were brand new?, before they were ever fired?

[biologicole]

Fell out when the brass were new. The primers didn't fall out on the bench but did fall out in the ammo box by the time I got to the range. Some came out after the first firing. I was very sure it wasn't due to overpressure and that's when I figured out that the primer pockets were too large. Maybe I just missed this one. It did make me start wondering... if someone were to bump back the shoulder too far if that would create excessive headspace and cause the primer to back out?

[Marco Califo]

Are you using a full length resizing die to "bump" the shoulder? This is called "Sizing" back to correct SAAMI deminions. You need the die, calipers and a case guage to do this. If you did not Size the brass to SAAMI specs, that is a problem.
Primers falling out is NOT NORMAL. Providing the load specifics and measurements would help solve your issue.

[44 AMP]

Assuming your primers are the correct dimensions, primers falling out of new brass means the brass is DEFECTIVE!

I would contact the maker and request replacement, at a minimum, and if the don't want the defective brass back, it should go in the scrap brass can, immediately.

If you are using standard reloading dies, you can bump the shoulder back more than you want, but you cannot bump it back enough to create excessive headspace, if your rifle chamber and die are both in spec.

If either is out of spec, that is a different situation.

You got a bad batch of brass, if it was new, I would be bitching to the maker. IF not new, I would have a talk with who ever sold it to you....

[GeauxTide]

Fell out when the brass were new.

I have used Remington brass, rifle and pistol for 50 years. I have never had this issue without overpressure. You should contact Remington.

[PA-Joe]

Are you sure that you are using the correct primers? Primers should not fall out of a new case. Were the primers seated all of the way down or did they project out of the case? It sounds like they were not seated all of the way down.

[biologicole]

Thanks for the replies. I’m pretty sure it was a batch of bad brass. It’s unnerving to have a primer fall out after firing and I was just trying to cover all the bases. The first loading I thought it was too much powder so I re-measured the COAL and then disassembled and re-weighed powder. No problems with lengths or weights but it was during that process I discovered loose primers in the new brass and then acquired a primer pocket gauge. I thought I had sorted out all of them but apparently I didn’t. This is the first time its happened since the sorting but I’ve only shot about fifty since then. My normal process when acquiring new, or used, brass is to resize, trim and prime them all at the same time for consistency. Then I load the prepared brass with whatever powder/bullet combo I need. Glad to hear I didn’t somehow bump the shoulder back too far and create an issue.

[cdoc42]

biologicole said: "I acquired a primer pocket gauge and sorted them all out, I think. Here's the problem, after sorting out the large primer pockets, I reloaded the remaining brass. "

I agree with 44AMP that the brass is defective. If you found any NEW cases with enlarged primer pockets, I would contact Remington and ship them back for replacement. Some that were seemingly acceptable may well have still been too large and dropped the primers after firing that you described. When I first started reloading I had 20 new Remington cases in a box of 20 that looked like the necks were shorter than others than I had. Having no clue about the significance, I contacted Remington and they replaced them. 30+ years later I ran into a bunch of Winchester cases that seemed to have exceptionally large primer pockets. I contacted Winchester, but they called me back during office hours and I couldn't break away to talk to them. I just called it a day and trashed them.

[Unclenick]

Originally Posted by biologicole

I set shoulder bump by inserting into the chamber and setting back {resizing} die 1/4 turn until there’s minimal or no resistance on bolt closure.

Yeah, the standard die threads are 14 TPI, so each turn is 1/14 inch or 71.4 thousandths, so a quarter of a turn is almost 18 thousandths. That's bigger than the maximum headspace. You want to turn much less than that. Maybe a 20th of a turn. Indeed, it's best to be able to control thousandths at a time. This Forster lock ring has graduations for that. You just put a pencil or Sharpie mark on the press to register the ring location, then another on the die threads over one of the ring graduations, loosen the ring's cross-bolt and rotate the die so that mark moves the number of thousandths you want it to, check that the ring is in the same place and tighten the cross-bolt again. You can also print your own graduated paper disks and use them to control the depth setting. I have a template in pdf format here.

Since you said you have the Hornady gauge, get the 0.400" case bushing for the 260R. It will fit in the bullet comparator's caliper adapter. With that, you can measure the head-to-shoulder dimension of an as-fired case and tweak your sizing die to set it just a couple of thousandth's below that.

[tangolima]

I do similar things. I use electric pencil to engrave graduation marks on lock ring. 6x4=24, each corresponds to about 0.003”. The registration mark is also engraved on the die body with the same tool. Sharpie marks don't last, tattooing does.

However the graduation marks don't always work linearly, especially the final 10 thous or so. The press flexes under pressure, so does the brass spring back. The force the press exerts is no joke, easily over 1000 lbf. I wouldn't surprise if the whole thing flexes by as much as 10 thous. I just keep advancing till the job is done.

The job is done when the resistance in chambering is gone. But be careful about that. The resistance could come from places other than the shoulder. If the chamber is cut too tight, the brass head will have difficulty getting in and hence the resistance. A tight chamber usually comes with difficulty extracting though.

-TL

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[44 AMP]

Oddly enough, I don't have issues with resistance to chambering when I set my sizer die in firm contact with the shellholder at full ram extension.

[biologicole]

Uncle Nick, that’s good information to have. I didn’t realize 1/4 turn was 74.1 thousandths. That’s a lot. I did 1/4 turn because that’s what my mentor did. I now have a set of Sheridan gauges headed my way, including a slotted ammo checker. I want to check out the shoulders on my loaded ammo. Many thanks for the great discussion.

[Unclenick]

Well, 74.1 thousandths is a full turn, so a quarter turn is about 18 thousandths.

44AMP makes the practical point that with a normal die, the shell holder won't allow you to resize smaller than the factory size, but still, moving in larger steps will keep you from hitting a precise value.

When you get the comparator insert, check one of your fired cases against a new case. They shouldn't be different by much over ten thousandths normally. If there's a much bigger difference, you have a chamber issue. If you set up to make the shoulder 0.002" shorter, you won't need to size it all the way, and your brass will last through more reloadings.

[tangolima]

Different rifles. Loosy Goosy chamber needs less sizing. The shortest I have seen is swiss k31 with Lee die. I kept going till I realized the die bottomed out on the shell holder top even with the brass inside. Couldn't go any further and the chambering still had some resistance. I stuck the die to a sander to take away 10 thous from the mouth. Advancing the die a tiny bit more and it was all good.

Is it bad to take metal away from the die mouth? There is a radius machined in the die mouth. As long as the radius is still there, you are not hurting anything.

The tightest chamber is converting 6.5mm carcano to 7.62x45 Czech. The head diameter is a tad big. I thought the sizing die would squeeze the head down. Not enough. Had to chuck the brass to a drill to remove some metal with file.

-TL

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[Marco Califo]

Sheridan Slotted case guages are great for knowing what is going on.

[biologicole]

Here’s some feedback on my question about shoulder bump, overpressure and primers falling out. I checked the headspace on my rifle, gauged hundreds of loaded cartridges and I’ve disassembled, re-weighed, re-measured and checked approx. 25% of all different shells in batches of different types and weights of bullets. Being satisfied that all is well with my gun and reloads I went back to the range today. Shot a couple with no problems and then another primer fell out. I switched to a different reload and no problems for three shots. Then shot yet another load and the primer fell out on the first round. I switched guns and continued shooting and while switching the suppressor I began wondering if the suppressor could be the cause. All of my loads were developed before I got a suppressor and are 0.8-1.3 gr below max and were developed by starting at the minimum and working up. So, I shot the rifle again without the suppressor and didn’t have any more primers fall out. I didn’t risk putting the suppressor on and blowing primers again. In the end, the only variable is the suppressor and the primers didn’t fall out until I started using it and I don’t have this problem with other guns which host the suppressor. I don’t have any explanations but these are my observations.

[HiBC]

I have no suppressor experience so I will leave that alone.

I have seen the results of excessive head clearance, Some semi-automatic rifles MAY present residual pressure after unlocking.A suppressor might aggravate the situation by being a pressure reservoir.

If its a bolt gun,with excessive head clearance,the primer will get pushed out by the amount of head clearance. This happens while the case head is off the bolt face in response to the firing pin strike. Initially, pressure will obturate the case and it will grab the chamber walls as the primer is. forced to the bolt face.
As the case is still gripping the chamber forward,at the chamber mouth there is nothing to grip. As pressure blows the case head back to the bolt face,two things happen.The primer will get re-seated.It may look very flattened by the process.
And the case will stretch. This stretch will be localized near the chamber mouth.
It will cause the brass to thin. If things are as you suspect,your brass will have a good start on a stretch ring,. It will look like an internal O-ring groove just ahead of the case head. Its easy to see if you section a case. It can be felt if you make a probe hook with a paper clip. Look up "Stretch ring"

That scraps your brass.

You may notice another problem. Its remarkable how fast hot gas leakage past a primer can cut an erosion ring on the bolt face.

I would not fire any more of that brass.IMO,its dangerous. See if Remington will give you a return authorization. If they can find the brass defective I'd think they'd replace it.

If its a semi-automatic other folks know more.You may need an adj gas block or a heavier buffer,but I;m not a suppressor guy.

[Recycled bullet]

That's like saying changing the muffler caused spark plug failures on a pickup truck.

I think hibc is right.

I also think your primer pockets are loose and the cartridge cases should be retired, and that it's possible your brass and go- no go gauges may be headspaced on the extractor.

[44 AMP]

and that it's possible your brass and go- no go gauges may be headspaced on the extractor.

If that is the case, you're either doing something wrong, or you've got the wrong kind of gauge. Some designs require removal of the extractor (and perhaps the ejector, others have relief cuts in the gauge so neither of those touches the gauge.