223 shoulder bump

[gpurp]

I'm starting to reload 223 need some clarification on shoulder bump. I'm using a Redding full length sizing die run all the way down to the shell holder. I see that custom height shell holders are available that will increase shoulder bump +2, +4, +6 thousandths.

The question is whether additional shoulder bumping is really necessary. I've seen several threads recommending bumping at least .002 for semiautomatics. Well ok but won't the FL sizer shape the brass back down to factory new ammo sizes? I must be missing something.

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[FLIGHT762]

The "custom" shell holders (Redding Competition shell holders) do NOT increase shoulder bump. They DECREASE it by .002", .004",.006" etc. You can look up on how they are used.

The question is how do you measure your shoulder bump? Just setting the die to hit the shell holder doesn't necessarily mean you're bumping the shoulders too much or too little or if you're setting the shoulders back to Factory specs (SAAMI minimum). You have to have a way of measuring the amount of shoulder that particular die is set at. You will then either have to turn the die further into your press or back it out.

There's a number of gauges on the market to do the shoulder bump measuring.

For my gas guns, I bump the shoulders .003"-.005". For my bolt guns, I bump back .001"-.002". I happen to prefer the Hornady gauge kit to do my measuring. There will be others here that will recommend other gauges.

There are tons of videos on the net that explain how to use a gauge to determine shoulder bump.

 

[gpurp]

Perhaps that explains some of my confusion. The plus sign in the description +.002, +.004, +.006 looked like increasing to me.

I also have the Hornady headspace comparator gauge. I've measured once fired cases before and after FL sizing and am only seeing -.001 and some with no change at all.

When I say the die is screwed down touching the shell holder I mean it barely touches with the ram all the way up. It's not camming over. Not sure if that's making much of a difference.


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[Walkalong]

The plus sign in the description +.002, +.004, +.006 looked like increasing to me.

+ height on the shell holder, which moves the sizer up .002, .004, etc., therefor leaving the shoulder up by that amount compared to a standard shell holder.

Best bet is to get a way to measure where your shoulder is after firing and go from there.

I also have the Hornady headspace comparator gauge. I've measured once fired cases before and after FL sizing and am only seeing -.001 and some with no change at all.

That doesn't sound right.

 

[Metal God]

When I say the die is screwed down touching the shell holder I mean it barely touches with the ram all the way up. It's not camming over. Not sure if that's making much of a difference.

Depending on the press it can and likely will make a big difference .

All presses have flex/deflection in the linkage and even the the steel itself . See below at these pictures . The first pic shows the die set up as you described yours are set up , just barely touching the shell holder .



This second pic shows how much press deflection you can get when sizing a 308 case



As you can see that is quite a bit . You are likely experiencing the same thing and is why you are not bumping your shoulders back much .

The die and shell holder should make hard contact with cam over in order to remove all flex/deflection in the press . If you size a case using a standard shell holder and make hard contact between the shell holder and die . It should size the case down to SAAMI minimum . This is the key principle in the Redding competition shell holders . They allow you to make hard contact with out sizing your case down more then needed . I love my comp shell holders .

 

[gpurp]

I have a new T-7 press and never thought about deflection. That very well could be why I'm not seeing any bump. I have to run home and try that tonite.

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[FLIGHT762]

Turning the die 1/8th of a turn moves the die .009". That can make a difference of too much or too little bump. It usually take a little bit of fiddling to get the correct amount of shoulder bump.

A very important thing in F/L sizing, to get consistent shoulder bump you must use a proper amount of case lube. Cases not lubed properly will show erratic bump. Another thing is not to run the press ram too fast in and out of the die. A 1-2 second pause at the end of the top stroke can also help.

 

[Metal God]

I should add that you don't have to have hard contact in order to size cases . Many people have that gap when sizing cases to a specific rifle . The thing about allowing the flex/deflection is not all cases in a lot will have the same hardness ( work hardened) . Some will size easier then others while a few will resist sizing quite a bit . This results in a inconsistent shoulder bump . Making hard contact with cam over with either standard or competition shell holders will result in a much more consistently sized case lot . Meaning all cases sized will be much closer to the same size as one another . I'm getting +/- .001 , with many being with in .0005 when using my competition shell holders and making hard contact with cam over .

Now when I say hard contact it really just means hard enough that the die and shell holder are making contact when sizing a case . You can over do it and put unnecessary stress on the press linkage . Keep that in mind when you test this out .

 

[flashhole]

Not all shell holders are cut to the same dimensions. If you are barely able to get the shoulder moved back, try a different shell holder ... or ... use a shim material under the case when it is in the shell holder. A piece cut from a beer can can make a significant difference. My presses don't allow me to make a shim from a soda can. It gives them an inferiority complex.

 

[Bart B.]

With reduced loads, new cases oft times have less case headspace after firing. Bottleneck cases tend to have their shoulders set back 1 to several thousandths inch upon firing pin impact. How much depends on:

* Pin spring strength.
* Pin weight.
* Pin protrusion from bolt face.
* Lubricity of the case shoulder against the chamber shoulder.
* Case/chamber shoulder area.
* Case/chamber shoulder angle.
* Primer cup hardness.

I've shot loads in .30-06 and .308 Win cases incrementally reduced by half and full grain increments. When reduced load's are about 10% below max, case headspace is often shorter than before firing. And the primer has backed out past the case head because there wasn't enough pressure to expand the back half of the case until its head stopped against the bolt face.

 

[Slamfire]

The question is whether additional shoulder bumping is really necessary. I've seen several threads recommending bumping at least .002 for semiautomatics. Well ok but won't the FL sizer shape the brass back down to factory new ammo sizes? I must be missing something.

Without gages to measure what is going on after full length resizing, how do you know? Before I purchased cartridge headspace gages I followed the die instructions of sizing to the shell holder plus a quarter turn. After I acquired cartridge headspace gages, none of the ammunition I had sized was correctly dimensioned.

I also have the Hornady headspace comparator gauge. I've measured once fired cases before and after FL sizing and am only seeing -.001 and some with no change at all.

Your Hornady headspace comparator will only provide repeatable results with a bolt gun. It won't work with a semi auto. By the time your hand touches the bolt in a manually operated rifle, barrel pressures are zero. The case has fully expanded and it will be very close to a true chamber size. Whatever the chamber headspace, the cartridge headspace will be the same (within our measuring capabilities) If however you are firing rounds in a gas gun, that Horandy Headspace comparator is useless for setting up your dies. All gas guns open up when there is residual pressure in the barrel, and during extraction the slight residual pressure, which is 650 psia or less, will stretch the case. This little amount of pressure causes the case mouth and shoulder to stick to the chamber during unlock and thus, the base to shoulder dimensions of the extracted case are going to be different from the chamber dimensions.

To accurately size semi auto cases, you need a true gage. I have dropped in my chamber headspace gages in my Wilson cartridge case headspace gages, and they correspond exactly for base to shoulder length. Therefore, it is my opinion that a gas gun owner ought to be using these instead of the comparator, as the comparator is a relative measuring device.

Size the cartridge case so the sized cartridge is between Go and No Go.




If you are sizing for a gas gun, something you have not positively stated one way or another, I recommend pushing the shoulder of the case back about 0.003" from chamber headspace, or if you don't know chamber headspace, just size to the low step. Which corresponds to chamber headspace "Go".

 

[Metal God]

Slamfire , I do believe what you're saying about semi auto cases is generally accurate . I do disagree that the Hornady comparator is useless in that application . I have found as long as I have full pressure loads I get a consistent case head space measurement using a comparator. Where I've seen the most inconsistencies is when shooting under powdered 223 rounds in my AR's . 223 rounds like AE red box and some PMC rounds tend to give inconsistent measurements but 5.56 NATO stuff like the stuff marked LC give me pretty consistent measurements . I'll concede I may not be getting a perfect measurement out of my auto loaders . How ever after measuring/comparing 20 fire formed cases and 15 of them having virtually the same case head space tells me that's the number to bump .003 from . It's worked quite well for me so far .

 

[gpurp]

I'm making progress now. After adjusting the sizing die for a mild cam over I'm seeing a fairly consistent -.010 shoulder bump. I'm used to years of reloading straight wall pistol cases so shoulder bump was never a concern.

I have a couple 223 gas guns that I'm loading for and also a bolt action varmint rifle. Now that the comparator is registering the bump value I'll start thinking about actual head space. Thanks Slamfire for pointing out the difference for measuring gas vs bolt guns. I also now can see the value of the competition shell holders.

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[FLIGHT762]

The Hornady gauge is a comparator and will not read out a SAAMI number. What I did to get SAAMI minimum bump base line measurement with the gauge is to take a Go gauge in that cartridge and note that measurement.

That will be a measurement you can use as a baseline similar to the bottom step in the Wilson style drop in gauge. I've done this with the proper Hornady gauge inserts for 223 Rem., .308 Win., 30/06, 270 Win. and 260 Rem.

 

[Walkalong]

I'm making progress now. After adjusting the sizing die for a mild cam over I'm seeing a fairly consistent -.0010 shoulder bump. I'm used to years of reloading straight wall pistol cases so shoulder bump was never a concern.

A .001 bump is too little. Considering differences in brass hardness some will be more, but some will be less. .001 is cutting it way too close for a semi auto. Or did you mean .010 (Ten thousandths), which is too much. Now a gauge would be handy to see if you have the shoulder within SAMMI spec.

 

[gpurp]

Good catch. I meant .010 ten thousandths. And this should be the minimum size according to spec, right? I'll measure with a Wilson gauge to confirm.

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[Blue68f100]

0.010" is too much like Walkalong said. You need to back it off some so you only get 0.002"-0.003" (0.005" Max) is the preferred range for a simi-auto gas gun. You will also find that after each firing it gets harder to move the shoulder back and may require a readjustment. This is one reason I anneal after every firing, keeps every thing consistent. Another option is use shims under the die. You start with a 0.010" and as things need to be tweeked you remove shims. This is where the competition shell holder come in. Allows you to adj in 0.002" steps.

All measurements is in reference to min spec. So it's possible that you may need to move the shoulder back 0.010" after firing.

 

[Walkalong]

He probably has too much head clearance now (Artificial headspace)(Yea, I know, a couple of folks hate that term ) if he moved the shoulder back .010 from where it was after firing. Anyway, it creates the same unsafe condition one would have with good ammo and an improperly headspaced chamber.

http://www.thehighroad.org/showthread.php?t=734058

 

[fguffey]

Another option is use shims under the die. You start with a 0.010" and as things need to be tweeked you remove shims. This is where the competition shell holder come in. Allows you to adj in 0.002" steps.

Not really; placing a shim beneath the case head and deck of the shell holder increases the presses ability to overcome the cases ability to resist sizing and the method/technique allows a reloader to size cases for short chambers.
There was a time when the reloader could not close the bolt on a size case they would grind the top of the shell holder and or bottom of the die. It was never necessary to grind the shell holder or die but reloaders persisted.

Same with going the added expense of purchasing Redding Competition shell holders, the shell holders are nice; I have one set. I paid $5.00 for the set at a gun show. The set is a #6 set for belted magnums. I do not use the set but I have it just in case.

I have always used a feeler gage to adjust the die off the shell holder. I have one chamber that requires a gap of .014" between the bottom of the die and top of the shell holder.

And then there is that thing about bumping the shoulder back; when I move the shoulder back I upset the case body, I have turned cases into accordion looking bellows; in fact the only way I can move the shoulder back is to crush the case.

F. Guffey

 

[Metal God]

Nice catch Walkalong . That explains why the OP added the 0 at the end .0010

Yep .010 is way to much and can result in head separation in two or three reloads

These 308 cases were reloaded 3 times and all had about that same .010 head clearance in the chamber when fired . gpurp , as you can see they have head separation or about to .


Sizing your cases down to much will reduce case life and can be dangerous . Think a bought that case splitting/cracking in an auto loader and the bolt is unlocking while pressure is still in the chamber like slamfire talked about . Not going to be a good time when that happens .

 

[fguffey]

With reduced loads, new cases oft times have less case headspace after firing.

That would make sense if the case had head space. If you are talking about the case getting shorter when fired you should try to determine where the case got shorter.

F. Guffey

 

[Chuck R.]

I the shim method......

I set my dies to FL size and use Hornady bump gauges for measurement. I then use a set of "Skips Die Shims" from Sinclair International, between my die and press to back my die of the required amount to achieve my desired .003-.005" for a bolt gun.

This way I can use the same set of dies for multiple guns, then just record the correct set of shims to achieve the stand-off I'm looking for. It keeps me from having to readjust my dies.

Chuck

 

[gpurp]

Thanks for all the replies and sharing your knowledge. I achieved the .010 bump as an intermediate step in understanding this process but I'm not finished. The few cases I already sized can get fed through my bolt gun for plinking and then crushed.

I originally wasn't getting any bump due to my sizing die just barely making contact with the shell holder but not actually camming over with the ram all the way up. Now that the sizing die is screwed in a tad more I'm getting a light cam over and now see the .010 bump. The cam over seems like a good thing because it prevents inconsistent sizing due to press deflection and variations in brass. The bad part is too much bump from what everyone is saying. So the next step is that competition shell holders are on the way and I plan to use the +.006 holder to net a .004 bump for my gas guns.

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[gpurp]

There is one thing that bugs me though. If sizing cases back to minimum SAAMI dimensions creates an unsafe condition (too much bump) then there should be a big neon warning message on the die box about that. Had I not have asked I could have gone on my merry way smashing every case back to minimum size. Regardless, I'll still do the paper clip check and watch for shiny rings at the base!

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[FLIGHT762]

How have you determined SAAMI (1.464") minimum with your Hornady comparator? Unless you calibrate you Hornady gauge with a "GO" 1.464" gauge, you are just guessing.

I haver dies that will bump the shoulders -.005" shorter than SAAMI spec. You normally take measurements off of the shoulders of your fired cases, but in some gas guns, the shoulders can be blown a bit farther forward than the actual chamber. The M14 / M-1A is notorious for this.

In my 5.56 / 223 rifles, my various Colt 5.56 chambers fired cases are about +.007. In my Wilde chambered White Oak barrel, it's +.003"-.005". My Remington 700V fired cases are +.001".

This is why you set your dies to bump the shoulders according to the Rifle's chamber you are loading for.

I have to 308 gas guns. My SR-25 fired cases measure +.001"-.002". My GAP10 fired cases measure +.004".

One thing I did to be sure my reloaded ammo would fit my Colt 5.56 chambers, I made dummy rounds (no primer or powder with a seated bullet) with various shoulder set back lengths and I would chamber the dummies and see at what shoulder bump length would and would not chamber. That will give you a good way to set you die. It really doesn't take that much time to do this.

I have about 3 - 5.56 chambered Colt Ar-15's and one Wylde chambered AR-15. If I want ammo to fit all of the rifles, I set my die @ SAAMI minimum (from my calibrated measurements) shoulder bump. Even at SAAMI minimum bump, I can get 5+ reloadings out of my cases in my Colt 5.56 chambers.