Pressure issue (HeadSpace? )

[Zero333]

Here is how to determine if you resized the brass too much or how much working headspace you have when chambering a factory round....

Tape masking tape on the base (head) of the cartridge brass. 1 layer of masking tape extends the case by 0.002".

If the bolt doesn't close on 1 or 2 layers masking tape then headpace is good.

If bolt closes on 2 layers of tape (0.004" working headspace), but doesn't close on 3, then headspace is long but still safe.

If the bolt closes on 3 layers of masking tape (0.006" HS) but not on 4 pieces, then the headspace is still safe but do not reload the brass more than 3 times because it might rapture from walls thinning.

If the bolt closes on 4 pieces of masking tape (0.008" headspace), then the headspace is EXESSIVE, but brass will not rupture on the first fireing.

If bolt closes on 5 pieces of tape, I would not shoot the gun !

For refference... A no-go headspace gauge is 0.004" longer than the go-gauge.

A field gauge is 0.007" longer than a go-gauge. If the rifle chamber a "Field" gauge, then the headspace must be redone.

Remove the ejector when testing the headspace with the masking tape method.

I use this method on every rifle I buy and on every barrel I install. I just use a go-gauge and add the tape onto it.

Hope you understand what I'm trying to say


Some dies when set up to overcam, actually size the brass more than 0.004" smaller than a go-gauge

A headspace comparator or a headspace micrometer are the ideal tools for measuring the amount of shoulder bump.
I like 0.002" to 0.003" bump.

ohh yeah... forgot to mention to trim the tape around the head with scissors so its no bigger than the head itself. I use a sharp knife and scuff it downwards around the edge of the head's rim. This cuts it perfectly. I don't know the actual word so I said "scuff"

 

[johnfred1965]

The top two cases in your picture show an ejector mark, which may only be marking due to a sharp machined edge on the ejector hole. A little touch-up with some fine eemory paper could make that disappear. The bottom case seems to show some ejector wipe, was that case a different load?

 

[7Saum]

The top two cases in your picture show an ejector mark, which may only be marking due to a sharp machined edge on the ejector hole. A little touch-up with some fine eemory paper could make that disappear. The bottom case seems to show some ejector wipe, was that case a different load?

Thanx,here is what I did pics to follow (hopefully )
52.5 gr rl17 -Norma Brass 145LRX OAL 2.96
55 gr -H4350-Rem Brass 145LRX OAL 2.96
Factory Nosler Custom 160 accubond 2.75
COAL I am touching lands at 2. 98 I put black marks on case to show(ejector mark in between ) I use Redding type S bushing style dies..
Thanx..

 

[7Saum]

...or an ejector which doesn't retract at least flush with the bolt face for whatever reason.

Bill

I checked that out and it seems to go just under the bolt face..
Thanx Terry

 

[7Saum]

Here is how to determine if you resized the brass too much or how much working headspace you have when chambering a factory round....

Tape masking tape on the base (head) of the cartridge brass. 1 layer of masking tape extends the case by 0.002".

If the bolt doesn't close on 1 or 2 layers masking tape then headpace is good.

If bolt closes on 2 layers of tape (0.004" working headspace), but doesn't close on 3, then headspace is long but still safe.

If the bolt closes on 3 layers of masking tape (0.006" HS) but not on 4 pieces, then the headspace is still safe but do not reload the brass more than 3 times because it might rapture from walls thinning.

If the bolt closes on 4 pieces of masking tape (0.008" headspace), then the headspace is EXESSIVE, but brass will not rupture on the first fireing.

If bolt closes on 5 pieces of tape, I would not shoot the gun !

For refference... A no-go headspace gauge is 0.004" longer than the go-gauge.

A field gauge is 0.007" longer than a go-gauge. If the rifle chamber a "Field" gauge, then the headspace must be redone.

Remove the ejector when testing the headspace with the masking tape method.

I use this method on every rifle I buy and on every barrel I install. I just use a go-gauge and add the tape onto it.

Hope you understand what I'm trying to say


Some dies when set up to overcam, actually size the brass more than 0.004" smaller than a go-gauge

A headspace comparator or a headspace micrometer are the ideal tools for measuring the amount of shoulder bump.
I like 0.002" to 0.003" bump.

ohh yeah... forgot to mention to trim the tape around the head with scissors so its no bigger than the head itself. I use a sharp knife and scuff it downwards around the edge of the head's rim. This cuts it perfectly. I don't know the actual word so I said "scuff"

I have scotch tape,electical,and packing tape,I tried with 1 piece of electrical tape closed with a little resistance,but with 2 it wouldn't...
Thanx Terry

 

[mr45man]

I have scotch tape,electical,and packing tape,I tried with 1 piece of electrical tape closed with a little resistance,but with 2 it wouldn't...
Thanx Terry

Take a piece of scotch tape, fold it over on itself and measure it so you know how thick the layers are.

 

[savagedasher]

I have scotch tape,electical,and packing tape,I tried with 1 piece of electrical tape closed with a little resistance,but with 2 it wouldn't...
Thanx Terry

That my way . Larry

 

[johnfred1965]

I was originally directed to this site while reading a thread on case head separation. It is a great explanation of pressure and its indications. There are some high rez photos of ejector printing along with explanations for many conditions

https://www.primalrights.com/articles/understanding-pressure

 

[7Saum]

Take a piece of scotch tape, fold it over on itself and measure it so you know how thick the layers are.

Will do....
Terry

I was originally directed to this site while reading a thread on case head separation. It is a great explanation of pressure and its indications. There are some high rez photos of ejector printing along with explanations for many conditions

https://www.primalrights.com/articles/understanding-pressure

I actually have seen that article and all the pics,I don't think mine is extreme as what is shown,my primers seem to be fine,but then again that's why I have asked this question because I'm not sure,and I want to be 100%..
Thanx Terry

 

[dkhunt14]

The best way to measure pressure is measure expansion of case heads. I didn't see pressure signs on your cases. Matt

 

[7Saum]

The best way to measure pressure is measure expansion of case heads. I didn't see pressure signs on your cases. Matt

So,when I put a fired case in my rifle, a little resistance happens but nothing extreme..do I measure the case head itself, or up from it..
Thanx Terry

 

[dkhunt14]

So,when I put a fired case in my rifle, a little resistance happens but nothing extreme..do I measure the case head itself, or up from it..
Thanx Terry

Do a search. I measure the extraction groove and also right in front. Matt

 

[fguffey]

I have been from 15th -50thou off the lands, and all mild-med loads and always pressure,can I be doing something wrong in the reloading process to cause this?Or could this be a HeadSpace issue?,

There are many that paint with wide brushes, to them everything has head space and all gages are head space gages. For me it is not that complicated, my chamber has head space my head space is measured from the datum/shoulder to the bolt face; and that is it, my cases do not have head space. My cases have a length, I use the length of the case from the shoulder of the case head to off set the length of the chamber. The difference in length between the chamber and case is clearance. I can have a lot of clearance, I can have 'zero' clearance and I can have a crush fit. And then there is relating head space to pressure.

The length of the case from the shoulder to the case head can have an effect on pressure, it should not be a problem for those that can keep up but to do so the reloader must know the clearance. Seating the bullet to or into the lands can have an effect on pressure. When seating into the lands the reloader must understand when seating to or into the lands not start with maximum loads.

And then there are soft case heads that imprint on the bolt face.

I would suggest measuring the diameter of the case head before and again after firing, it is a god ideal to start with new cases. I have fired cases once and then had to take the rifle apart to remove/find the primer. I have fired cases once and expanded the case heads .100". The case heads crushed, the case heads expanded and shortened, the primer pockets opened and the flash holes took on the appearance of having been drilled out. When testing rifles that are suspect I choose to use cases with thick case heads. I have older Remington (R-P) cases with case heads that measure .260" thick from the cup above the web to the case head. When crushing case heads a thick case head is safer than a thin case head. I have thousands of 30/06 military cases like LC with case heads that measure .200". I know, that is confusing but I believe the R-P cases had an additional .060" safety built into them when testing suspect rifles.

F. Guffey

 

[M-61]

Quote from fguffey:
"And then there is relating head space to pressure."

This is done how?
-------------------------------------------------------------------------------------------------------------------
Quote from fguffey:
"When seating into the lands the reloader must understand when seating to or into the lands not start with maximum loads."

"not start with maximum loads".

I would not recommend starting with a MAXIMUM load is advisable in any situation.

 

[gotcha]

So,when I put a fired case in my rifle, a little resistance happens but nothing extreme..do I measure the case head itself, or up from it..
Thanx Terry

Set your re-sizing die to bump the shoulder back .002" ................. You'll need a comparator (hornady lnl guage) to do this accurately................ This is a "must have" tool for any serious re-loader concerned about cartridge H/S. ....... In the mean time set up your resizing die and adjust it in VERY small increments like 1/32 of a turn until your bolt closes on the fired case with no resistance. ...... Since you have a variety of brass, some softer than others, do this for each type of brass. this will allow you to put the possible H/S issue to bed and allow you to concentrate on other possibilities.

 

[Brians356]

I have seen factory brass up to .010 short on headspace. Matt

It's common for factory ammo the be .008 to .010 short of SAAMI chamber. However, this is a custom, so it could be a lot worse than that.
-

 

[Riesel]

Have you checked neck clearance? Does a bullet drop freely into the neck of a fired case? Measurement of the neck OD of a fired case vs a loaded case?

Is it suppose to? If not,, then what is happening/

 

[Sheldon N]

Is it suppose to? If not,, then what is happening/

I've lost track of whether the OP has solved his issue, but to answer your question...

The rifle chamber needs have sufficient clearance around the outside of the neck of a loaded round. This allows the case and case neck to expand slightly on firing, releasing the bullet from the case. If the rifle chamber constricts the neck of the case then this can prevent the bullet from releasing easily from the case, causing buildup of pressure within the case. If the case neck were seriously constricted then pressure could rise to dangerous levels.

After firing the case will have expanded to the chamber dimensions (with a little bit of springback), so this gives you a sense of what size your chamber is relative to a loaded round. For example on my 308 (not a benchrest gun, chambered with a standard reamer for a no-turn neck) cases after firing are around .341 in diameter at the neck, which is about .003 larger than the diameter of a loaded round at .338. This 0.003 of extra clearance allows a bullet to fall freely into a fired case and also lets me know that I have plenty of room in my chamber to safely shoot that particular neck diameter.

Now if you can't fit a bullet into a fired case, that's an indication that there's not much expansion taking place and not much room in the chamber. If you had that issue you'd want to investigate further whether you had enough neck clearance in your chamber to safely fire those rounds, or if you needed to neck turn your brass to give you enough clearance.

 

[Riesel]

I've lost track of whether the OP has solved his issue, but to answer your question...

The rifle chamber needs have sufficient clearance around the outside of the neck of a loaded round. This allows the case and case neck to expand slightly on firing, releasing the bullet from the case. If the rifle chamber constricts the neck of the case then this can prevent the bullet from releasing easily from the case, causing buildup of pressure within the case. If the case neck were seriously constricted then pressure could rise to dangerous levels.

After firing the case will have expanded to the chamber dimensions (with a little bit of springback), so this gives you a sense of what size your chamber is relative to a loaded round. For example on my 308 (not a benchrest gun, chambered with a standard reamer for a no-turn neck) cases after firing are around .341 in diameter at the neck, which is about .003 larger than the diameter of a loaded round at .338. This 0.003 of extra clearance allows a bullet to fall freely into a fired case and also lets me know that I have plenty of room in my chamber to safely shoot that particular neck diameter.

Now if you can't fit a bullet into a fired case, that's an indication that there's not much expansion taking place and not much room in the chamber. If you had that issue you'd want to investigate further whether you had enough neck clearance in your chamber to safely fire those rounds, or if you needed to neck turn your brass to give you enough clearance.

Thank you for your reply. I was firing test loads in a new 6.5 CM and later I noticed that the cases would not let a bullet slip in. I was shooting near max with both H4350 and IMR4350 and both powders shot best at just under max and at 2950 fps using a 123 Amax. No pressure signs at all.
When resizing I did notice the neck sizing down and then the expander ball with some resistance, but not much. Resized cases fit easily and loaded ammo fit with no problem so I think I'm good. Noticed not much overall case expansion and the cases were a breeze to resize. Also, nearly zero "soot" on fired case necks. Fifth barrel on this reamer, think the reamers getting smaller?

 

[Sheldon N]

Sounds like you're good. Maybe this lot of brass is a tiny bit thicker than last one (if you're using new brass)? Probably only a couple thou' difference between fine and too tight, but seems like you're on the right side of that.