Shoulder Setback & Die Bottoming Out

[Phil3]

I am new to reloading, shoot an AR15 in 223 Remington, and have a question regarding shoulder setback and the Redding full length sizing die bottoming out on my Forster C-Ax press shellholder jaws.

Using some Sinclair tools, the average length of fired cases is 1.277". The actual measurement is not relevant...it is odd because of the attachments on the measuring calipers. I carefully adjusted the die downwards a bit at a time, measuring the case until it measured 1.274", so as to give about .003" clearance between the shoulder and the chamber.

I found that to achieve the 1.274" dimension the die was bottomed out on the press shell holder jaws. It would not be possible to push the shoulder back any more since you can not screw the die down any further. This seems very odd to me. What if the rifle had fired shells that were 1.273". Trying to set the shoulder back to 1.270" (.003" clearance), would be impossible.

All this seems to indicate a very tight chamber, and perhaps it is. It is a Krieger barrel chambered in 223 Remington, not 5.56.

Please educate me on what I may be missing here.

- Phil

[Low-Pressure]

I'm not sure if I read you post correctly.
Are you trimming the cases? The max length for 223 is 1.760" if it is longer than that it should be trimmed down to 1.750".

[22popnsplat]

a small base die will set the shoulder back farther .
from the rcbs site

The Small Base Die set is intended for use for ammunition to be used in auto, semi-auto, and lever action rifles so that the loaded round chambers and extracts easily. The Small Base Sizer Die sizes the case from the shoulder to the head of the case a couple of thousandths smaller than a Full Length Sizer Die.

[Phil3]

I'm not sure if I read you post correctly.
Are you trimming the cases? The max length for 223 is 1.760" if it is longer than that it should be trimmed down to 1.750".

The cases will be trimmed after resizing. The measurement of 1.277" is not the length of the case. It is the length of the case measured from the datum line on the shoulder to the end of the case, using calipers with Sinclair attachments for supporting the shoulder and holding the case end. The actual measurement does not matter as the only thing I want to do here is to set the shoulder back .003" further back than where the shoulder is after firing. The measurement then is strictly for comparative purposes, not an absolute, such as the case length of 1.75".

- Phil

[FLIGHT762]

I would suggest you make up a few dummy rounds (no powder, no primer) using the bullet you will be shooting. Check the dummies in your rifle to see if they chamber smoothly.

If they don't, you may need a small base die.

If they do, go with it. .003" should be enough shoulder setback.

I use the Hornady headspace gauge set. I bought the Sinclair headspace set that fits in the hornady holder. I get very different measurements with the Sinclair gauges. They seem to index on a different part of the case shoulder.

If you find the die doesn't size far enough, you may be able to contact the die maker and find out if they can shave a couple thousandths off of the base of the die for you.

Glenn Zediker explains this in book "Handloading for competition". It's a good resource.

I think you should first try try dummies. I think the .003" bump should work for you.

[Low-Pressure]

The cases will be trimmed after resizing. The measurement of 1.277" is not the length of the case. It is the length of the case measured from the datum line on the shoulder to the end of the case, using calipers with Sinclair attachments for supporting the shoulder and holding the case end. The actual measurement does not matter as the only thing I want to do here is to set the shoulder back .003" further back than where the shoulder is after firing. The measurement then is strictly for comparative purposes, not an absolute, such as the case length of 1.75".

- Phil

Gotcha! I would assume this helps for a more accurate round, correct?

[swerv512]

^^^
+1. i've heard of guys putting the die in a lathe and taking a couple thousandths off... some companies make extended shellholders that should do the trick for you.

[Nessal]

Gotcha! I would assume this helps for a more accurate round, correct?

I wouldn't say more accurate, but helps with feeding.

I've been bumping my shoulders back by 0.003" but dont have problems with feeding so i stopped and it saved me an extra step.

[Nessal]

I would suggest you make up a few dummy rounds (no powder, no primer) using the bullet you will be shooting. Check the dummies in your rifle to see if they chamber smoothly.

If they don't, you may need a small base die.

If they do, go with it. .003" should be enough shoulder setback.

I use the Hornady headspace gauge set. I bought the Sinclair headspace set that fits in the hornady holder. I get very different measurements with the Sinclair gauges. They seem to index on a different part of the case shoulder.

If you find the die doesn't size far enough, you may be able to contact the die maker and find out if they can shave a couple thousandths off of the base of the die for you.

Glenn Zediker explains this in book "Handloading for competition". It's a good resource.

I think you should first try try dummies. I think the .003" bump should work for you.

I believe that the sinclair measures from the
datum of the should but the
Hornady measures at the base of the shoulder. Correct me if im wrong.

[swerv512]

^^^
i use rcbs precision mics and they work great and all measurements are very repeatable. the only bad part is that you need to have a separate one for each caliber.

[huckberry668]

it doesn't matter if the tool measures from the datum line or the base of shoulder. You'd use the same tool to measure both fired (deprimed) cases and sized cases for comparison.

I assume your measurement of 1.277" is on a deprimed case. The spent primer always protrudes a few thousandths. Use a 1/16" pin punch to remove the primer before measuring fire formed cases.

It doesn't matter if your die can only size it down to 1.274" as long as you can resize the cases to less than 1.277". Remember, the die doesn't just reduce the length of case it also reduces the girth. Running the brass thru the die 1 or 2 more times further reduces the length by a couple of thousandths. Try it.

Some chambers are tighter or looser but 1.273" fired case on your headspace gage is probably from a out of spec (short) chamber and that's no good. If you really want to know for sure, buy a 223Rem 'Go' gauge and take its measurement and compare. You have a problem if your fired case is less than Go gauge. Some AR barrel alone maybe cut with short chambers if you don't supply your bolt for headspacing. In fact I know that for a fact from years back dealing with Krieger AR barrels w/o bolts.

The 'Go' gauge is the minimum size chamber you should have. Ammo company makes the cartridges a few thousandths less than that to make sure they load properly. This is why match grade rifle is headspaced to within .001" of the standard 'Go' gage. this way you'd have the least amount of wiggle room for any brand of ammo. This is also why bolt gun shooters neck size their cases so there is no play when the round is chambered.

Less play means less unwanted/uncontrolled vibration down the barrel when the round is fired which contributes to better accuracy... mostly.

[killshot44]

Phil,
I have Redding dies as well. PM me which style you have and I think I can help.

The sizing die does NOT make the case shorter, it makes it longer. Thus the need to trim after sizing. Sorry Huckles...

Don't confuse caselength with the shoulder datum points. Lose the Sinclair and just measure caselength with a caliper.
Like Swerve says, get a RCBS Prescision Mic for measuring headspace and post-sizing case/shoulder dimension to set up your die.
What you're looking for in resizing is the proper setback of the shoulder and neck tension to hold the bullet, but overall caselength (1.750 to 1.760) must also be measured.

[Phil3]

I assume your measurement of 1.277" is on a deprimed case. The spent primer always protrudes a few thousandths. Use a 1/16" pin punch to remove the primer before measuring fire formed cases.

Well, I didn't measure with spent primer removed, so will need to redo the operation. Thanks for that tip.

Some chambers are tighter or looser but 1.273" fired case on your headspace gage is probably from a out of spec (short) chamber and that's no good.

The measurement of 1.277" is just an arbitrary measurement that results from a case head holder and case shoulder holder clamped to the caliper. The measurement would be something else if I used other tools. The actual number corresponds to nothing on a 223 Remington case measurement.

If you really want to know for sure, buy a 223Rem 'Go' gauge and take its measurement and compare. You have a problem if your fired case is less than Go gauge. Some AR barrel alone maybe cut with short chambers if you don't supply your bolt for headspacing. In fact I know that for a fact from years back dealing with Krieger AR barrels w/o bolts.

The 'Go' gauge is the minimum size chamber you should have. Ammo company makes the cartridges a few thousandths less than that to make sure they load properly. This is why match grade rifle is headspaced to within .001" of the standard 'Go' gage. this way you'd have the least amount of wiggle room for any brand of ammo. This is also why bolt gun shooters neck size their cases so there is no play when the round is chambered.

I had previously measured the headspace on the barrel/bolt assembly using headspace gauges. A "Go" gauge fits, a "No-GO' does not. Given that, I am quite sure the measured case will not measure less than the "Go" gauge, unless the chamber is very close to the "Go" gauge, and brass springback causes the case shoulder to be set back a tad further than the "Go" gauge.

- Phil

[Phil3]

I have Redding dies as well. PM me which style you have and I think I can help.

Sent you a PM.

Don't confuse caselength with the shoulder datum points. Lose the Sinclair and just measure caselength with a caliper.
Like Swerve says, get a RCBS Prescision Mic for measuring headspace and post-sizing case/shoulder dimension to set up your die.
What you're looking for in resizing is the proper setback of the shoulder and neck tension to hold the bullet, but overall caselength (1.750 to 1.760) must also be measured.

I understand the difference between case length and lengths measured from shoulder datum points. I address both. The case length (after all resizing is done) to ensure no jamming in chamber and resulting increased grip on bullet and perhaps dangerousl;y high pressures. Shoulder datum to case head to ensure shoulder is a close fit to chamber, also preventing case head stretching and potential separation (if case shoulder pushed too far back).

I can set both with the tools I have, but rather like the Redding Instant Indicator, even if more costly.

- Phil

[killshot44]

Phil, got it. Didn't mean to imply you didn't know the difference....mostly to clarify for other readers.

PM replied.