Shoulder Bump questions

[SaintPanzer]

I'm starting to realize I don't understand shoulder bump.

Here's the issue: I'm trying to come up with a safe load for my Mannlichers, starting with my 1903. A thing that is making this difficult is there are no published loads using Vihta Vouri powders, and the only published loads for Oryx bullets are with Norma powders, which are not always easy to find.

Yes, there are loads for other powders, and yes, Hornady 160 grain RNSP are back on the shelf, but that's not my point. Bear with me.

In the past, I had pressure signs with a 37 grain load of VV160 and Woodleigh Protected Point 160 grain bullets. Starting over, I checked everything, to include headspace on the rifles. Headspace checked, and New Old Stock RWS rounds had no problems. So it's not the rifle.

My second thought, because of the long nature of the Woodleigh bullets was I might be too close to the lands. As I went through that measurement process, what I learned is it is a long jump to the lands on these rifles. For the Woodleighs (both the PP and RNSP) to touch the lands, not only would the round be too long to fit in the magazine, but it would be falling out of the case. So I have that going for me. "reasonable length" is fitting in the neck, not much into the shoulder, and these are definitely NOT compressed loads.


I purchased a gauge to help measure shoulder bump. What I noticed was I was not bumping the shoulders enough, which led to headspace issues with the rounds themselves, not the rifle. OK, so start over with measuring the amount of shoulder bump to add from a pre-fired case. As I was trying to dial this in, I went a little too far.

Of course, dialing the die back out doesn't work, because there's nothing to "force" the shoulder back up. Is fire forming the only answer? If so, will the increased headspace (only about 0.004" - 0.006") be an issue, or should I use the "tissue/crisco/wax/cornmeal approach?

I want to get this right on the M1903s, because the M1910 does not have much of a shoulder to play with anyway. I can have another gauge made for the 1910, but the machinist has already warned me on the accuracy with such a small shoulder.

Am I overly worried about the bump? The dies are from CH4D, and instructions to set them say "screw to touch the shell holder when the ram is up". It does talk about how that's a good fit for a "strong" press, but a weaker press may have some spring. It mentions screwing a bit past "touch" for these spring presses. Right now, I'm using a Dillon 550, so yes, some spring, which has led to the "too much bump" and have plans to pick up a good single stage. But is the brass I sized so far useless, or is there a way to recover?

To give some idea the numbers we're talking about here, the gauge is a "comparator" type gauge. It's slipped over the shell and stops on the shoulder. You then measure from the base of the case to the top of the gauge. Measurements I have:

NOS (loaded) RWS cases: 2.087"
Fired RWS cases: 2.092-2.094"
Never fired NOS RWS "Hulsen": 2.087
Never fired Norma brass: 2.088
Where I landed after trying to set headspace: 2.083 - 2.085.

For what it's worth, the instructions on the gauge said to bump the shoulder back between 0.004 and 0.006, so my goal was 2.088, which is reasonably close to the NOS brass I have.

Any advice is very much appreciated. Yes, I could just go to IMR 4085 like everyone else, which solves the amount of powder to use... but I'd still need to get that shoulder bump part right, wouldn't I?

 

[JimP]

Try this.

Run the shell into the sizer die and pretty much just size the neck.

Then try it in your rifle and see how it chambers. If it doesn't chamber screw the sizing die down 1/4 of a turn and try it all over again.

When you get to the point that you can close the bolt with the slightest amount of resistance you have just bumped the shoulder back enough to chamber the round.

I do this with most of my bolt action rifles. Then before taking the loaded ammo hunting I'll run every one of them through the rifle making sure that each and every one will chamber.

 

[ftrovato]

Try this.

Run the shell into the sizer die and pretty much just size the neck.

Then try it in your rifle and see how it chambers. If it doesn't chamber screw the sizing die down 1/4 of a turn and try it all over again.

When you get to the point that you can close the bolt with the slightest amount of resistance you have just bumped the shoulder back enough to chamber the round.

I do this with most of my bolt action rifles. Then before taking the loaded ammo hunting I'll run every one of them through the rifle making sure that each and every one will chamber.

Question:
- I'm neck sizing 6.5 PRC Lapua Brass. (Never full length sized and only fired in this rifle).
- Cases are fired around 5 times.
- OAL is trimmed to minimum.
- The diie is set just off of the shell holder (I can see daylight when ram is at top of resizing stroke)
- The loads that have been fired through cartridge have been at max (maybe even a little hot)

Observation:
- The bolt is closing (and opening) tightly.
- I never used a neck sizer die before
- Do I need to get a full length sizer die?
- OR should I have the die touch the case holder when cartridge is being sized
- Will this push the shoulder back?

What am I missing here....?

 

[roklok]

I use Whiddon shoulder bump gauges and look for about .003 bump. I also use a Forster CoAx press with little to no "spring" to make consistent bump easier to achieve. To answer your question, I would load your brass with "practice loads" and shoot it to start over to get less bump. .004 to .006 should not cause any issues to fire loaded rounds.

 

[Tex .416]

This issue is critical for reliable ignition as well as feeding.

Use these headspace gauges to measure base to the middle of the shoulder on fired brass. Adjust the sizing die to set the shoulder back 0.0015” - 0.003”. Do not set it back more than 0.005” as that creates excessive headspace, which causes unreliable ignition.

fwiw - On most dies, one full rotation on the sizing die equals 0.030” of shoulder set back. So a 1/4 turn moves the shoulder back 0.0075”, which potentially is very excessive headspace and can cause a fail to fire.

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The Hornady Lock-N-Load Headspace Gauge is a great tool for increasing the accuracy of your loaded ammunition. The Headspace gauge measures from the...

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[SaintPanzer]

Thanks. The gauge I have is similar, but not made by Hornady. It does the same thing, it measures to the center of the shoulder.

The Forster CoAx is my planned purchase.

I have two M1903s, so full length, not neck sizing.

Sounds like once I know a "low-safe" load, I can fire form these and start over. I agree the excessive space could cause unreliable ignition, which is why I want to get it close.

I did try the "tape test". Three pieces of tape and the bolt closes on the "undersized" cases. Four pieces it is very stiff to close, and five is no close. I have to go back to my notes, but I think that was close with .003, no close at .005. It may have been a little less than that.

As far as feeding goes, the Mannlicher Schoenauers have two important points: Overall length must fit in the magazine, but where the neck and bullets sit is as important to the functioning of the rotary magazine as COAL. Secondly, a longer load for the bullet is needed to hit the feed ramp correctly, or it will jam instead of feed. You have to load "long enough" to feed, but not too long. The only good news to that issue is there is enough free bore that you'll run out of magazine (sometimes you run out of case!) before you run out of free bore.

 

[shootist~]

Measure the cartridge headspace on a few of your NOS unfired rounds. (Being sure the primer is not protruding). Now you have another reference point that may be helpful.

 

[SaintPanzer]

Measure the cartridge headspace on a few of your NOS unfired rounds. (Being sure the primer is not protruding). Now you have another reference point that may be helpful.

Yes, exactly. As I said: "NOS (loaded) RWS cases: 2.087""

 

[FlyGuy]

- Load and shoot as they are.
- Screw FL die all the way down to shell holder.
- Screw the die 1/2 turn back.
- Size case and measure.
- Move die down in small increments until you achieve your 0.002-0.003” bump.
- Take note of where the die is and make a note, so you can get back to that setting without going through all the fuss again.

 

[Ontario Hunter]

Shoulder bump cartridge? 458 Quasimodo Express

I learned the hard way how particular 404J can be about shoulder bump. I picked up a couple boxes of RWS brass that was just a bit short. Set my dies up for that length and couldn't get rounds to snap over when dropped in the chamber. No belt on those cases so head space is finicky.

 

[shootist~]

is the brass I sized so far useless, or is there a way to recover?

To give some idea the numbers we're talking about here, the gauge is a "comparator" type gauge. It's slipped over the shell and stops on the shoulder. You then measure from the base of the case to the top of the gauge. Measurements I have:

NOS (loaded) RWS cases: 2.087"
Fired RWS cases: 2.092-2.094"
Never fired NOS RWS "Hulsen": 2.087
Never fired Norma brass: 2.088
Where I landed after trying to set headspace: 2.083 - 2.085.

So your "cartridge" headspace is as much as .0011" on the initial sizer setup (2.094 - 2.083).

~.007" is pretty normal for the difference in factory new brass and fired brass, assuming modern commercial (not military spec) chambers. And non-belted magnum brass.

A few 338 WM (belted magnum) rifles I've checked have run .0014 to .0017" cartridge HS (at the shoulder). This is from using the Hornady Cartridge Headspace tool with the recommended bushing. Obviously the reason belted magnum cases have a shorter life span.

I cannot advise you if your cases are damaged or not, but if you had never measured you would be probably be loading away (and wondering why your case life was so short). Or worst case, why you had a broken or ruptured case.

Common sense would preclude using them in anything close to a maximum pressure load, IMO.

I shoot for ~.002" ctg hs for the bolt guns and keep brass sorted between rifles - and the number of times reloaded and annealed. I also anneal before the brass gets brittle.

Even .000" cartridge hs on occasion is OK and will chamber just fine IF the brass was only ever fired in that rifle. (Same as neck sized.) Due to springback, a reading of .000" is probably not as tight as you might think.

 

[shootist~]

Shims make sizer die adjustments much easier, btw.

https://bulletin.**NOT**PERMITTED**...loader-die-shims-for-full-length-sizing-dies/

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[Grumpy gumpy]

I was taught to resize to the chamber, not some arbitrary size in a book. It does make it a bit more difficult for multiple rifles of the same cartridge with different ammunition requirements, but not insurmountable as a texta mark on the bottom shows which rifle it belongs to.
Gumpy

 

[SaintPanzer]

- Load and shoot as they are.
- Screw FL die all the way down to shell holder.
- Screw the die 1/2 turn back.
- Size case and measure.
- Move die down in small increments until you achieve your 0.002-0.003” bump.
- Take note of where the die is and make a note, so you can get back to that setting without going through all the fuss again.

Will try shooting with a light load.

It's that "moving down in small increments" piece that I took too far. Had it from .094 to .089. Tried to get .002 more, and ended up with .004 more...

 

[SaintPanzer]

I was taught to resize to the chamber, not some arbitrary size in a book. It does make it a bit more difficult for multiple rifles of the same cartridge with different ammunition requirements, but not insurmountable as a texta mark on the bottom shows which rifle it belongs to.
Gumpy

Yes, with two rifles, which chamber?

 

[SaintPanzer]

So your "cartridge" headspace is as much as .0011" on the initial sizer setup (2.094 - 2.083).

~.007" is pretty normal for the difference in factory new brass and fired brass, assuming modern commercial (not military spec) chambers. And non-belted magnum brass.

A few 338 WM (belted magnum) rifles I've checked have run .0014 to .0017" cartridge HS (at the shoulder). This is from using the Hornady Cartridge Headspace tool with the recommended bushing. Obviously the reason belted magnum cases have a shorter life span.

I cannot advise you if your cases are damaged or not, but if you had never measured you would be probably be loading away (and wondering why your case life was so short). Or worst case, why you had a broken or ruptured case.

Common sense would preclude using them in anything close to a maximum pressure load, IMO.

I shoot for ~.002" ctg hs for the bolt guns and keep brass sorted between rifles - and the number of times reloaded and annealed. I also anneal before the brass gets brittle.

Even .000" cartridge hs on occasion is OK and will chamber just fine IF the brass was only ever fired in that rifle. (Same as neck sized.) Due to springback, a reading of .000" is probably not as tight as you might think.

I think I understand, but...

Was trying to get to .087 to .088. So difference of .007 or so. Not what I would call a "modern commercial", unless by modern you mean 1921.

I made the mistake of over-bumping to .083. No one to blame but myself. Tiny turns weren't changing much, so ham-handed me went a touch further, and went too far.

The reason I was measuring was a previous incident of "not bumping enough, and having a huge over-pressure problem (which I will get into on another thread). So I was trying to be more careful to get it right. Short story there (longer story on a thread I haven't started yet) is I have a "good enough" load for 156 grain Oryx and 160 grain RNSP 160 grain Hornady, but still over-pressure on Woodleighs.

I wouldn't mind the idea of matching brass to rifles, but wanted to get "generic right" before getting more specific. I learned the hard way yesterday that even changes in bullets can make a huge difference, and not in a good way.

 

[shootist~]

Based on my experience loading for several Swedish Mausers - and one broken 6.5x55 Lapua case - I would say keeping brass separated by rifle is significantly more important for the older rifles.

 

[SaintPanzer]

Based on my experience loading for several Swedish Mausers - and one broken 6.5x55 Lapua case - I would say keeping brass separated by rifle is significantly more important for the older rifles.

Yeah... but I can still get 6.5X55 in the store. Not as easy with 6.5X54.

 

[375 Ruger Fan]

 

[shootist~]

Good video. Ultimate Reloader is a good source for lots of things, even some supressor information that I was curious about recently.

I really like the ease of making small adjustments on his press. (I still use lock rings and a universal decapping die). My press is a Redding Turret press with 7 stations so at least I don't have to constantly swap out dies.