Excessive Shoulder Setback Risk?

[Phil3]

In adjusting a die for proper shoulder setback, I inadvertently set the die too far down. Compared to fired cases, the shoulder on some resized cases is set back as much as .008" - .009", far too much. Given that the case will stretch at the head area because of this, am I risking case/head separation? If so, I will discard. These cases will go in an AR-15 (223 Remington chambered).

Thanks,

Phil

 

[BoydAllen]

I would crush their necks and toss, or recycle them.

 

[Steve Blair]

If it was a bolt gun, you could run some "fire forming" loads with jammed bullets and restore the shoulder position. For an autoloader, Boyd's right.

 

[mr45man]

One could expand the necks to 6mm and re-size properly?
John H.

 

[Phil3]

What is the most shoulder setback that is considered safe? I know I want the minimum for whatever gun I am using (semi-auto vs bolt), but if I screw up, just wanting to know at what point should they be tossed due if the shoulders are pushed back too far.

Phil

 

[bigedp51]

Phil3

How many reloaders don't have a Hornady cartridge case headspace gauge?

How many reloaders set their dies up as per the instructions and make hard contact with the shellholder or cam over?

What is the length of a factory loaded cartridge?

How long is a military field gauge?

What is max headspace on the M249 machine gun?

And how much shorter than a factory cartridge are your cases.

 

[37Lincoln1]

Don't learn the hard way, it is not worth it. .09 is too much. Half that would be OK.

 

[timeout]

Don't learn the hard way, it is not worth it. .09 is too much. Half that would be OK.

I presume that you mean .009"

 

[Kings X]

I agree with mr45man.
Expand and set false shoulder. Good brass is too hard to come by these days.

 

[jsthntn247]

You will be fine on one firing. I wouldn't run them extremely hot though. Make sure you don't do that next time on the brass and you will be fine.

 

[spclark]

They'll chamber OK but very likely that much headspace will lead to misfires. Simply put an AR firing pin doen't have enough reach to strike primers that far away with any reliability.

 

[Phil3]

Phil3

How many reloaders don't have a Hornady cartridge case headspace gauge?

How many reloaders set their dies up as per the instructions and make hard contact with the shellholder or cam over?

What is the length of a factory loaded cartridge?

How long is a military field gauge?

What is max headspace on the M249 machine gun?

And how much shorter than a factory cartridge are your cases.

I don't get or understand the purpose of your message. Frankly, it seems rather condescending, but maybe I am reading it wrong.

Phil

 

[Phil3]

I am the OP, and a few things, one of which is raises some puzzling questions.

The die I used was (and is) properly set up...for the Winchester brass I resized last time. This time I resized PMC brass and the shoulder setback is too much. The different brass may have been responsible for some of that, but setback growing from .004" - .005" to nearly double that seems beyond what a change in brass could be responsible for. Still, I need to check and adjust the die with different brass and periodically during the sizing process.

The next experiment was more revealing. Since I have a Wilson case gauge, I checked these excessively sized cases. They are ever so slightly below the minimum "step" on the gauge, meaning they are slightly shorter in case head-to-shoulder length than the SAAMI spec window. Wanting to know how much shorter, I protected the Wilson gauge with electrician's tape, put it in my lathe, and used a test indicator to measure the distance the case sat down below the Wilson minimum gauge surface. I used a smooth part of the case head without stamping to measure from. The case was sitting .0005 - .0006" below the minimum level on the Wilson gauge. Out of spec, but by very, very little.

So, I have a SAAMI spec chamber, my cases are resized to minimum SAAMI spec (+ .0005") according to the Wilson gauge, and I should be safe to go (if the tiny .0005" is ignored). But wait, the resizing has pushed the shoulder back .008" - .009", which according to some, is too much. So which is it? Does one go by the Wilson gauge or the actual shoulder setback from a fired condition? I had hoped to use the Wilson gauge as a quick check to make sure something is not amiss, but maybe not.

I checked a new Lapua case. It is about .002" longer than the resized PMC cases, but easily passes in the Wilson case gauge, clearly sitting higher than my resized PMC cases. Factory Hornady ammo was much longer than the Lapua, by about .004" and only about .002" shorter than fired cases. It actually sits ABOVE the top level of the Wilson gauge, but not by much.

Little unsure now about what to believe on setting headspace. I got the gauge to ensure I was not making mistakes in my measurements, but even factory ammo does not pass!

For these 45 cases, I will offer them to someone for a cheap price..., probably less than shipping unless someone can pick up in San Francisco bay area. Will put up on the For Sale forum later. Otherwise, into recycling.

Phil

 

[jo191145]

If I may make a suggestion.

Buy a comparator. With it you'll know exactly what your doing to the headspace of your brass. JMO but all this SAAMI spec stuff is useless once the weapon is in your hands and the chamber has been cut.
Chances are very high, even in an AR you do not want to be sizing your brass down to SAAMI specs.

 

[gilream]

The shoulders on new Winchester brass for my 7 Rem Mag are .017 (17 thousandths) short of the chamber's head space. They can be blown out on the first firing but after that I watch my shoulder bump "like a hawk" as Boyd says.

I could not operate without my caliper mounted Stoney Point (Hornady) head space gauge. It makes the shoulder bump measurement very repeatable and easy to read. Never had the Wilson HS gauge but I do know that they make high quality stuff.

One thing to remember, as I found this out the hard way too...the softness of the brass is a big determining factor as to how it responds to FL sizing. Annealed (softer) cases are always much more consistent in my experience. Your PMC brass was probably much softer than the Winchester brass that you set the die with.

Not sure how many times the cases in question have been fired but if in doubt I would toss them.

 

[Phil3]

If I may make a suggestion.

Buy a comparator. With it you'll know exactly what your doing to the headspace of your brass. JMO but all this SAAMI spec stuff is useless once the weapon is in your hands and the chamber has been cut.
Chances are very high, even in an AR you do not want to be sizing your brass down to SAAMI specs.

I have a comparator. This one. http://www.sinclairintl.com/reloading-equipment/measuring-tools/bullet-comparator-inserts/sinclair-insert-style-bullet-comparator-prod34014.aspx

It is how I measured the shoulder setback in the first place and know that from fired brass, shoulder setback was on the order of .008" - .009". As I mentioned in the original post, the chamber is 223 Remington minimum SAAMI spec. It is not some loose chamber specific to an AR-15.

Phil

 

[Phil3]

The shoulders on new Winchester brass for my 7 Rem Mag are .017 (17 thousandths) short of the chamber's head space. They can be blown out on the first firing but after that I watch my shoulder bump "like a hawk" as Boyd says.

I could not operate without my caliper mounted Stoney Point (Hornady) head space gauge. It makes the shoulder bump measurement very repeatable and easy to read. Never had the Wilson HS gauge but I do know that they make high quality stuff.

One thing to remember, as I found this out the hard way too...the softness of the brass is a big determining factor as to how it responds to FL sizing. Annealed (softer) cases are always much more consistent in my experience. Your PMC brass was probably much softer than the Winchester brass that you set the die with.

Not sure how many times the cases in question have been fired but if in doubt I would toss them.

Wow, .017"! Makes my .008" seem like nothing. I have the Sinclair gauge for measuring shoulder bump. http://www.sinclairintl.com/reloading-equipment/measuring-tools/bullet-comparator-inserts/sinclair-insert-style-bullet-comparator-prod34014.aspx It is how I discovered the .008" setback. Yes, apparently the brass does make a difference. The die sizes Winchester brass to where I want it. But on the PMC. Lesson learned for me. The cases were fired once. They are slightly below the minimum mark on the Wilson gauge. There aren't that many cases, so will just not use these.

Phil

 

[BoydAllen]

Fellows,
Apples and oranges...the 7 mag. is a belted case, so on first firing the shoulder is blown forward, one time. The belt keeps the back of the case from being pushed forward very far. This is different from what happens when you bump a rimless case too much, stretching and thinning the case near its head....two entirely different situations. BTW I have compared new brass and fired in 7 mag, and .300 Wby., and the fired cases' shoulders were blown forward .021., even so, because of the belt, there is no risk of separation near the head. On the other hand, if one does not set the FL die based on measurement from shoulder to head, and simply adjust the die to touch the shell holder, brass life will be short.

 

[243winxb]

Phil3 Load and shoot that brass. Only worry if set back is in the .014" range. Even then it will take a few firings. Separation happen in the body as well as head.

Photo Albums www.photobucket.com/joe1944usa

 

[Shynloco]

Is .223 Brass that difficult to find these days for an AR? Just toss the messed up ones. We've all been there one time or another and Boyd's initial suggestion is the best solution IMHO.

Alex