How much should head space increase with new brass?

[hoz53]

I have seen new .303 British brass blow the shoulder forward about .060 on the first shot when fired in a Lee-Enfield rifle.

The Lee-Enfield rifle chambers just don't resemble the ammo as close as we are used to.

.060 is quite a bit I wonder how long that brass would last? I realize the various militaries are only concerned about the first firing.

 

[msinc]

I have had three different belted magnum rifles come in the shop with accuracy complaints in the last 4-5 years. I always find that the headspace proper {off the belt} is correct, but that the shoulder is way deeper into the barrel than it should be. Sounds like exactly what you have going on here. Take a look at the SAAMI drawing for the case and see what this measurement is supposed to be. That is, from the case head or belt to the junction of the shoulder and neck {for lack of a better point such as a datum line}. Measure your chamber based on fired brass...they really should be within .004" which is in effect headspacing off the shoulder. You can always pick a datum line and use it, but what is it referenced to so you know the dimension???
Without exception, I always had to get a known good chambering reamer, set the shoulder back and rechamber the rifle. I have never seen an aftermarket or custom reamer that was off...which makes me wonder, since so many factory rifles have this issue does the factory chamber with two different reamers??? One to do the body and shoulder and the other to cut the belt and set the headspace???? I don't know, but it sure seems to be relatively common to have good "belt headspace" but the shoulder way too long. I have seen/corrected the ones I have received, but I have heard many shooters/smiths discuss this issue.
The rifles I set back and re-chambered all shot good afterwards, that is if they had a good bore to start with and good ammo. Can you run it like it is??? Sure, but it really does work your brass and it might not group as well as it should. The last one was a Sendero 7mm Rem Mag. that belonged to my nephew...it had .036" deeper shoulder than what the SAMMI drawing called for. It shot nice consistent 2.5" to 3" groups "all day long", "if he did his part."

 

[ireload2]

.060 is quite a bit I wonder how long that brass would last? I realize the various militaries are only concerned about the first firing.

Lee Enfield brass has wildly varying life. I have seen the first firing with factory ammo give head separations.
If thin US made .303 brass is FL sized in SAAMI dies and is fired in a Lee-Enfield chamber it will usually separate at one to 3 reloads. If you neck size it only, it may last 5 or 6 reloads or it might not.
There are other reasons for this besides shoulder location with a Lee Enfield such as sloppy headspace, under size case heads compared to the chamber and the springy rear locking action. All these issues contribute to the case head separations. But neck sizing is one area where you can help the life of the brass.

 

[hoz53]

Lee Enfield brass has wildly varying life. I have seen the first firing with factory ammo give head separations.
If thin US made .303 brass is FL sized in SAAMI dies and is fired in a Lee-Enfield chamber it will usually separate at one to 3 reloads. If you neck size it only, it may last 5 or 6 reloads or it might not.
There are other reasons for this besides shoulder location with a Lee Enfield such as sloppy headspace, under size case heads compared to the chamber and the springy rear locking action. All these issues contribute to the case head separations. But neck sizing is one area where you can help the life of the brass.

yeah I could see under those conditions why the brass wouldnt last long. I wonder how much trouble the military had with first firing head separations when the enfields were in service. For me now unless it had some sentimental value I dont think I would keep a rifle like that around.

 

[fguffey]

This is with Hornady and Win brass. Really the only reason I checked this was because I was trying to diagnose a FTF issue.

I am sure you have listed the make and model of the rifle, I have more than one 300 Win Mag, they are different. Fail to fire: reloaders assume the extractor jumped the case rim, by design one of my belted magnum rifles pushes the case head up in front of the bolt face and is held there with the extractor. It is possible the shooter does not know the difference between control feed and push feed. Shooters have attempted to chamber a round in a control feed rifle like it was a push feed; it is possible but difficult to close the bolt on a case when the extractor does not jump the rim, then fired, if it will fire the extractor jumps the rim; problem, the extractor pushed the case forward and all of the clearance was between the bolt face and case head. That is bad but as most of you have read on this forum: The firing pin strikes the primer and drives everything (case, powder and bullet) forward before the primer ignites, and I have said that is always bad

3. With a shoulder bump gauge you are measuring from the case head to some non-standard point on the shoulder on a fired case. It doesn’t matter where on the shoulder since you are looking for change only. Mid shoulder is probably where it’s indexed?

None of this above probably means much since most of us know how to reload quality ammo.

A reloader that reloads quality ammo understand there is no such thing as a non standard point on the shoulder. The circle/round hole used to measure the length of the case from the case head to the standard point on the shoulder is .420" for the 300 Winchester Mag. Other standard points? include .410" for the 308 W family of cases and .375" is used for the 30/06 family of cases. And yes, there are exceptions like the 300 H&H, the 300 H&H is a belted case but uses a .375" round hole when determining the distance from the standard point to the case head.

I am the only one that does not use standard diameters listed by SAAMI, I am the one that understands when using a comparator and measuring before and again after it is not necessary to use SAAMI specifications.

If someone does a search of SAAMI drawings they will find SAAMI uses 'Basic' instead of non standard/standard.

F. Guffey

 

[Richard Jones]

I am sure you have listed the make and model of the rifle, I have more than one 300 Win Mag, they are different. Fail to fire: reloaders assume the extractor jumped the case rim, by design one of my belted magnum rifles pushes the case head up in front of the bolt face and is held there with the extractor. It is possible the shooter does not know the difference between control feed and push feed. Shooters have attempted to chamber a round in a control feed rifle like it was a push feed; it is possible but difficult to close the bolt on a case when the extractor does not jump the rim, then fired, if it will fire the extractor jumps the rim; problem, the extractor pushed the case forward and all of the clearance was between the bolt face and case head. That is bad but as most of you have read on this forum: The firing pin strikes the primer and drives everything (case, powder and bullet) forward before the primer ignites, and I have said that is always bad




A reloader that reloads quality ammo understand there is no such thing as a non standard point on the shoulder. The circle/round hole used to measure the length of the case from the case head to the standard point on the shoulder is .420" for the 300 Winchester Mag. Other standard points? include .410" for the 308 W family of cases and .375" is used for the 30/06 family of cases. And yes, there are exceptions like the 300 H&H, the 300 H&H is a belted case but uses a .375" round hole when determining the distance from the standard point to the case head.

I am the only one that does not use standard diameters listed by SAAMI, I am the one that understands when using a comparator and measuring before and again after it is not necessary to use SAAMI specifications.

If someone does a search of SAAMI drawings they will find SAAMI uses 'Basic' instead of non standard/standard.

F. Guffey

Must........resist.............must.........resist...........but, this is priceless. Scary, but priceless. We are not worthy.

 

[Webster]

Must........resist.............must.........resist...........but, this is priceless. Scary, but priceless. We are not worthy.

Is there such a thing as measuring OCD.

 

[ireload2]

It appears you do not understand what the term "Basic" means on a drawing. You might want to refer to ASME Y14.5M Geometric Dimensioning and Tolerancing. This is the standard that SAAMI drawings have to comply with.

If someone does a search of SAAMI drawings they will find SAAMI uses 'Basic' instead of non standard/standard.

F. Guffey

 

[Webster]

This is poorly done, but............... View attachment 1003757

Looking at old post. In regard to your correction of the location of head space on the WIKI photos. Your 100% correct. FGUFFEY tipped me off to double checking and looking at a go gauge. The SAAMI drawing does index off what looks like the diameter at mid length of the shoulder. The SAAMI drawing does give a diameter at a specific distance from the case head. Each cartridge type does have a specific diameter to locate off of for head space. None of this is important to me since my 6BR does fine without spending hours in my basement measuring things. SAAMI doesn't have a very complete drawing list. No common comp cartridges (6BR, 6 Dasher).

 

[Brians356]

Consider SAAMI specs for 300 Win Mag:

Cartridge Max shoulder datum length is "2.2700 - .0070" meaning the calculated Min datum = 2.2630".

Chamber Min shoulder datum length = "2.2701 + .0100" meaning calculated Max datum = 2.2801".

Chamber Max datum minus Cartridge Min datum = 2.2801 - 2.2630 = .0171.

That .0171" is only .0009" less than your observed .018" growth. However, since 300 Win Mag headspaces on the belt, any such minor discrepancy is irrelevant.
-

 

[Demi-human]

Is there such a thing as measuring OCD.

Yes. It is measured in cycles divided by time. Lower numbers are better.