Shoulder bump problem

[PD Gohil]

308 1x FC brass from my rifle.
Redding full length sizing die.
Using my Hornady comparator, the unsized brass was 1.6205. I work my die down to where it was 1.619 for a .0015 bump back. Check the next few cartridges and all was good. Did 120 cartridges all on my co-ax press. Decided to double check them randomly and got results from not sized at all, all the way down to 2.616 ... I can't figure out why there was such a large discrepancy.
I ended up throwing out everything that was under 1.6175. And then try to resize those that were over 1.619. many of the ones I tried to resize I ended up getting a bad dimple on the shoulder and had to throw them away.
Can anyone tell me what I've done wrong? And also why would I get such a large variation in the shoulder measurements after sizing?

Thanks.
PGohil
WV

 

[Drop Port]

308 1x FC brass from my rifle.
Redding full length sizing die.
Using my Hornady comparator, the unsized brass was 1.6205. I work my die down to where it was 1.619 for a .0015 bump back. Check the next few cartridges and all was good. Did 120 cartridges all on my co-ax press. Decided to double check them randomly and got results from not sized at all, all the way down to 2.616 ... I can't figure out why there was such a large discrepancy.
I ended up throwing out everything that was under 1.6175. And then try to resize those that were over 1.619. many of the ones I tried to resize I ended up getting a bad dimple on the shoulder and had to throw them away.
Can anyone tell me what I've done wrong? And also why would I get such a large variation in the shoulder measurements after sizing?

Thanks.
PGohil
WV

sounds like over lubed

 

[STRSRLVR]

Did you take your initial measurements with the cases de primed and were the cases consistent before sizing? Starting off with a squeaky clean die & too much lube or inconsistent amounts of lube can all cause issues

 

[PD Gohil]

Did you take your initial measurements with the cases de primed and were the cases consistent before sizing? Starting off with a squeaky clean die & too much lube or inconsistent amounts of lube can all cause issues

Yes I took the initial measurements with the cases deep round and seemed extremely consistent over the 15 or so that I randomly measured out of the lot.
It was a very clean die for sure. This is the first time I had used it and wanted to make sure and get all the gunk and such out of it. So yes it was squeaky clean. I use landline and 90% alcohol and I don't feel like I was over lubed but I have thought about that as a possibility.

 

[Drop Port]

You mentioned the dimple on the shoulder and that is a common symptom of over lube

 

[NZ_Fclass]

Best results when annealed.

 

[BigWyoming]

If it is under 1.620 - shoot it.

Do you do the full measurement every time or use the comparator as a comparator?

 

[Straightshooter1]

308 1x FC brass from my rifle.
Redding full length sizing die.
Using my Hornady comparator, the unsized brass was 1.6205. I work my die down to where it was 1.619 for a .0015 bump back. Check the next few cartridges and all was good. Did 120 cartridges all on my co-ax press. Decided to double check them randomly and got results from not sized at all, all the way down to 2.616 ... I can't figure out why there was such a large discrepancy.
I ended up throwing out everything that was under 1.6175. And then try to resize those that were over 1.619. many of the ones I tried to resize I ended up getting a bad dimple on the shoulder and had to throw them away.
Can anyone tell me what I've done wrong? And also why would I get such a large variation in the shoulder measurements after sizing?

Thanks.
PGohil
WV

Those dimples suggest there's too much lube being use, as Drop Port mentioned. As for the variances you're experiencing, it could be a combination of things, to include too much lube.

I take it that the brass has not been annealed, so springback could be a big part of the problem where you're initial measurement of 1.619 may not have represented what you can expect from you sizing technique along with variance in spring back of the following brass. There can be variations in spring back with brass of the same lot, having to do with the thickness variations. Brass will have an initial spring back out of the die and when left sitting for a while, there can be more spring back occurring. To help mitigate this issue, having a dwell time of a few seconds (like 4-6 seconds or so) will help reduce the amount of spring back.

The other issue that can be at play is the use of the comparator. If you've got a hi quality comparator, then it'll be less of an issue. But if you happen to use a somewhat cheap comparator (like I often use ), the readings can be hard to get consistent.

Put all these together with a comparator insert that isn't clean (dirt with a little lube) and you can certainly get the results you've experienced.

Without annealing, I'd expect .002 variation at best.

I've fired a couple FC brass with a dimple on the neck and it was flattened right out and good to go.

 

[DaveTooley]

How do they fit in the rifle? If they chamber without undo resistance just shoot them.

 

[STRSRLVR]

Yes I took the initial measurements with the cases deep round and seemed extremely consistent over the 15 or so that I randomly measured out of the lot.
It was a very clean die for sure. This is the first time I had used it and wanted to make sure and get all the gunk and such out of it. So yes it was squeaky clean. I use landline and 90% alcohol and I don't feel like I was over lubed but I have thought about that as a possibility.

Over lubed could cause dimples. The hornady comparator has a very small contact portion on the shoulder and good chance it’s not even cut to the same angle as your die yet alone the angle of the fired cases. All lead to stacking tolerances and Make it hard to get real consistent measurements. I highly recommend setting up your bump by removing the ejector and firing pin assembly then slowing adjusting die until the bolt handle drops almost the whole way down by itself. At that point check with a few cases and then take some measurements and would consider that 0 if not maybe .0005 bump. Give the die a little turn down and get yourself the bump desired and should be good.

not sure of your die setup but if your using the expander on your die that could be pulling the shoulder back out a bit if the neck is sized too small. I would pick up a comparator for your caliper from whidden or Short Action Customs that is for your shoulder angle. That way you will be reading a larger surface are of the shoulder. Lots of different things could be happening but those are a few simple things you could do which should narrow it down a bit.

 

[old_heli_logger]

A dollar bill is 0.004" thick

 

[Beiruty]

It happens more often with 300WM cases.

 

[358WCF]

I've noticed when sizing that if I leave the case full up into the die for a few seconds rather than a quick in & out headspace dimension differs by a thou or two. How's your technique?

Digital caliper? Recheck your zero?

Shoulder dents are either too much lube &/or your die needs cleaned. Brass is fine. Just shoot it & dent will disappear.

 

[dgeesaman]

If you happen to be using Hornady lock and load quick change bushings, carefully inspect the bushings. The cast iron one that threads into my press wore down and my shoulder bumps got wonky until I replaced it. (No idea why those are soft cast iron - alloy steel would be ideal)

 

[Dave M.]

308 1x FC brass from my rifle.
Redding full length sizing die.
Using my Hornady comparator, the unsized brass was 1.6205. I work my die down to where it was 1.619 for a .0015 bump back. Check the next few cartridges and all was good. Did 120 cartridges all on my co-ax press. Decided to double check them randomly and got results from not sized at all, all the way down to 2.616 ... I can't figure out why there was such a large discrepancy.
I ended up throwing out everything that was under 1.6175. And then try to resize those that were over 1.619. many of the ones I tried to resize I ended up getting a bad dimple on the shoulder and had to throw them away.
Can anyone tell me what I've done wrong? And also why would I get such a large variation in the shoulder measurements after sizing?

Thanks.
PGohil
WV

Too much lube
Non annealed brass
Dwell time in the press
Cam over or hard stop press?

dave

 

[divingin]

The hornady comparator has a very small contact portion on the shoulder and good chance it’s not even cut to the same angle as your die yet alone the angle of the fired cases.

Most comparators don't rely on angles, just the hole of whatever size. Many chamfer the hole, though, which leads to weird measurements (looking at you, Hornady), and makes comparing readings from 2 tools impossible. Despite that, I think it would take a very large discrepancy in shoulder angle to get a significant change in measurement between cases.

I'm thinking that OP is seeing variations in press stretch leading to his bump changes. Try sizing several cases, and see how much of a gap you get between the bottom of the die and the top of the shellplate. A set of feeler gauges will tell you if that gap is consistent from case to case. If it varies, that's where your problem is.

 

[Rset]

I'm thinking that OP is seeing variations in press stretch leading to his bump changes. Try sizing several cases, and see how much of a gap you get between the bottom of the die and the top of the shellplate. A set of feeler gauges will tell you if that gap is consistent from case to case. If it varies, that's where your problem is.

With a standard co-ax this is not going to be reasonable an option due to the design. I vote for too much lube. Possible cause of both the inconsistent sizing as well as the shoulder dent. Easy to do even with lanolin if the mixture is too heavy.

 

[msilbernagel]

Is it possible, with un-lubed neck (inside) and a squeaky clean FL resizing die, that the expander ball is creating too much friction and pulling the neck back up too much?

I've seen some mention putting a little die wax on a q-tip and lightly putting some on the inside of the neck.

 

[Rset]

I've seen some mention putting a little die wax on a q-tip and lightly putting some on the inside of the neck.

If you do, I would suggest a very good cleaning of your cases afterwards or your powder will likely catch in the neck when charging the case. It's not a pleasant experience. I have been there and done that.

 

[DirtySteve]

Pgohil, Don't throw those cases out they dents cause no harm. They will iron out when they are shot..
1) Clean your die.
2) Anneal your brass.
3) When sizing, pause for a three count at the bottom of the stroke to allow for any spring back to settle.

All this has been said but it is important enough to say again... Well Cleaning the die was not said but it should be done more often than most folks do. Plus it will get rid of any lingering case lube build up.

Steve