THE ACCURATERELOADING.COM FORUMS

Accuratereloading.com    The Accurate Reloading Forums    THE ACCURATE RELOADING.COM FORUMS  Hop To Forum Categories  Guns, Politics, Gunsmithing & Reloading  Hop To Forums  Reloading    How much case head expansion is too much expansion?

Moderators: Mark
Go
New
Find
Notify
Tools
Reply
  
How much case head expansion is too much expansion?
 Login/Join
 
One of Us
Picture of Mike_Dettorre
posted
I read somewhere that .0005 is too much..

Heck my micrometers don't even go that fine...and heck that seems with in the marging of measuring error.


This in my 376 steyr and I am a 1.5 grns under the book max...setaed a little long 10/1000 off the lands...just never seen this before...

no flatten primers, neck sized only...


Mike

Legistine actu quod scripsi?

Never under estimate the internet community's ability to reply to your post with their personal rant about their tangentially related, single occurrence issue.




What I have learned on AR, since 2001:
1. The proper answer to: Where is the best place in town to get a steak dinner? is…You should go to Mel's Diner and get the fried chicken.
2. Big game animals can tell the difference between .015 of an inch in diameter, 15 grains of bullet weight, and 150 fps.
3. There is a difference in the performance of two identical projectiles launched at the same velocity if they came from different cartridges.
4. While a double rifle is the perfect DGR, every 375HH bolt gun needs to be modified to carry at least 5 down.
5. While a floor plate and detachable box magazine both use a mechanical latch, only the floor plate latch is reliable. Disregard the fact that every modern military rifle uses a detachable box magazine.
6. The Remington 700 is unreliable regardless of the fact it is the basis of the USMC M40 sniper rifle for 40+ years with no changes to the receiver or extractor and is the choice of more military and law enforcement sniper units than any other rifle.
7. PF actions are not suitable for a DGR and it is irrelevant that the M1, M14, M16, & AK47 which were designed for hunting men that can shoot back are all PF actions.
8. 95 deg F in Africa is different than 95 deg F in TX or CA and that is why you must worry about ammunition temperature in Africa (even though most safaris take place in winter) but not in TX or in CA.
9. The size of a ding in a gun's finish doesn't matter, what matters is whether it’s a safe ding or not.
10. 1 in a row is a trend, 2 in a row is statistically significant, and 3 in a row is an irrefutable fact.
11. Never buy a WSM or RCM cartridge for a safari rifle or your go to rifle in the USA because if they lose your ammo you can't find replacement ammo but don't worry 280 Rem, 338-06, 35 Whelen, and all Weatherby cartridges abound in Africa and back country stores.
12. A well hit animal can run 75 yds. in the open and suddenly drop with no initial blood trail, but the one I shot from 200 yds. away that ran 10 yds. and disappeared into a thicket and was not found was lost because the bullet penciled thru. I am 100% certain of this even though I have no physical evidence.
13. A 300 Win Mag is a 500 yard elk cartridge but a 308 Win is not a 300 yard elk cartridge even though the same bullet is travelling at the same velocity at those respective distances.
 
Posts: 10164 | Location: Loving retirement in Boise, ID | Registered: 16 December 2003Reply With Quote
one of us
posted Hide Post
I remember an article about loads in a 7mm mag and the criteria was .0005" expansion which seemed reasonable to him. He then had the loads pressure tested .They were 75,000 psi IIRC. The point was that the brass is so thick and hard at the head in those cases that any expansion is too much !!
 
Posts: 7636 | Registered: 10 October 2002Reply With Quote
One of Us
posted Hide Post
I've done that case head measuring thing and find that most all loads expand the head some. Now I don't worry much unless the expansion goes over the listed measurement in the manuals. I think more important is when expansion loosens up the primer pocket. Then I'm quite sure I've a problem.
 
Posts: 526 | Location: Antelope, Oregon | Registered: 06 July 2006Reply With Quote
one of us
Picture of jackfish
posted Hide Post
The literature on the subject indicates that there is no agreement as to the amount of casehead or pressure ring expansion that is acceptable.


You learn something new everyday whether you want to or not.
 
Posts: 1080 | Location: Western Wisconsin | Registered: 21 May 2002Reply With Quote
one of us
posted Hide Post
I feel that measuring the case head expansion can be a measurement of pressure. To try to do this on the internet is quite a challange but thats never stopped me before.

Some of the failings of measuring case head expansion is using new brass vrs previously fired brass. New brass works much better but at some point if a primer pocket is blown with a gross over load then of course you can measure the expansion!

Another detail is having a micrometer that has the best anvil. If the anvil fits into the narrow area on the head of say a 30-06 which has a short area then it will measure accuratley. If you just slop the anvil onto the case ahead of that to the expansion web then the data is useless.

It works but needs to be done right.

On new brass I use .001" as a max load.

A micrometer that will not measure in tenths needs to be replaced.


Join the NRA
 
Posts: 5543 | Registered: 09 December 2002Reply With Quote
One of Us
Picture of vapodog
posted Hide Post
I no longer measure it. I use primer pocket expansion as my guide. If the primer pocket expands such that I can't press fit a new primer after a third firing I'm over pressure FOR THE BRASS I'M USING!!!!!

Brass hardness varies and relying on CHE can lead to assumptions that are poor.

Frankly I don't care if my pressures are at 75,000 PSI as long as the brass can handle it and primer pocket expansion tells me that.

Obviously other signs such as sticky extraction or hard opening bolt lift need to take precident. But CHE isn't in my bag of tricks anymore!


///////////////////////////////////////////////////////////////////////////
"Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery."
Winston Churchill
 
Posts: 28849 | Location: western Nebraska | Registered: 27 May 2003Reply With Quote
One of Us
posted Hide Post
I concur with using primer pocket expansion as an indicator. If you decap with a universal decapper prior to resizing, you can feel if they come out too easy. Then you don't waste time and effort on the subsequent steps. Another good reason to use a hand primer, so you can feel how they go in.
 
Posts: 50 | Location: albany, ny | Registered: 09 October 2006Reply With Quote
one of us
Picture of ramrod340
posted Hide Post
I used to use head expansion. I still use it a little. What I found years ago using pressure testing that depending on the case .0005 could happen anywhere from 65-73,000. I found that Norma brass would give me .0005 at around 65,000 or a touch less. Also if I can't get 5+ loading without loose pockets the pressure is too high.

This is an interesting read.
http://shootingsoftware.com/ftp/dbramwell%20july%2019%2004.pdf


As usual just my $.02
Paul K
 
Posts: 12881 | Location: Mexico, MO | Registered: 02 April 2001Reply With Quote
one of us
posted Hide Post
There is a lot of assuming that goes on with measuring case heads that might foul up a beginner. One of the major assumptions is that of using a strong bolt gun with front locking lugs or a strong single shot.

You hope the guy measuring the case heads knows enough to avoid it with:
Lee-Enfields,
99 Savages,
Ballards,Remington Rolling Blocks, trap door Springfields and most other BPCRs,
Krags,
Most lever guns, auto loaders and pumps.
Contenders,
those Mausers with soft receivers
 
Posts: 9207 | Registered: 22 November 2002Reply With Quote
One of Us
posted Hide Post
I measure extractor groove expansion.
If I can measure any, the primer pocket will be loose in a few firings.

SAAMI specifications on primers and primer pockets per "Sinclair International's Precision Reloading & Shooting Handbook" 10th edition 1999

......................Depth min max diameter min max
small rifle primer pocket .117 .123 .1730 .1745
small pistol primer pocket .117 .123 .1730 .1745
Large rifle primer pocket .125 .132 .2085 .2100
Large pistol primer pocket .117 .123 .2085 .2100

.......................Height min max Diameter min max
Small rifle primers .115 .125 .1745 .1765
small pistol primers .115 .125 .1745 .1765
large rifle primers .123 .133 .2105 .2130
large pistol primers .115 .125 .2100 .2120"

As you can infer from the above, large rifle primer pockets and large rifle primers have interference between .0005" and .0020".

With .0005" of extractor groove growth, you may not notice a change in how hard it is to prime the case, but you will in 4 more firings, as it grows .0005" each firing.
 
Posts: 9043 | Location: on the rock | Registered: 16 July 2005Reply With Quote
One of Us
posted Hide Post
Dial caliper, with an analog readout is calibrated in 0.00x "thousandths." And so "between" the calibration lines is going to be 0.0005" -- "five ten-thousandths." But it's going to be an "eyeball" and not a hard data accurate reading.

0.0005" can be affected by not having the caliper square to the case head, having a chamber that is out of round, dirt/powder residue --

Savage 99 notes:

"A micrometer that will not measure in tenths needs to be replaced."

I'm thinking he means "ten-thousandths." But when talking micrometer specs it's good to be all reading from the "same page."

I remember asking a "non-machinist" in a machine shop once, "How many thousandths in an inch?"

And he says, "Jeez! They're really tiny! There must be a million of them!"

-- Just like the high school graduate I asked: "What's 15% of $100.00?"

And the answer was, "Gawd! It's awful early for that sort of stuff!"

A "tenth" is 0.x

A "ten-thousandth" is 0.000x

I'm sure I'm pissing into the choir box here. *S*

Brass gets "work hardened." It tends to "spring back" the first few times it's fired. Then it gets brittle and won't spring back. That's ONE metallurgical reason why the case head measures larger. But it could be sloppy work on a cheap caliper.

Primer pocket condition/fit is an index. Flattened/flowing primers -- Machine marks from the bolt on the face of the head -- Sticky bolt-lift -- Difficult extraction.

Jeez! I'm glad I gave up Wildcat loading!
 
Posts: 825 | Registered: 03 October 2006Reply With Quote
one of us
posted Hide Post
45/70
quote:
"A micrometer that will not measure in tenths needs to be replaced."

I'm thinking he means "ten-thousandths." But when talking micrometer specs it's good to be all reading from the "same page."


To a imagineer a "tenth" is 0.x
To a machenest, machine builder, gunsmith, and other skilled tradesmen, a "tenth" is 0.000x

The heat from your hand, holding the case or Mic frame, is enough to shift the measurments by a tenth.
 
Posts: 2124 | Location: Whittemore, MI, USA | Registered: 07 March 2002Reply With Quote
One of Us
Picture of El Deguello
posted Hide Post
quote:
Originally posted by Don Fischer:
I've done that case head measuring thing and find that most all loads expand the head some. Now I don't worry much unless the expansion goes over the listed measurement in the manuals. I think more important is when expansion loosens up the primer pocket. Then I'm quite sure I've a problem.


I regard any expansion that results in a drop in the amount of force required to seat new primers that I can feel using a hand priming tool to be unacceptable.....


"Bitte, trinks du nicht das Wasser. Dahin haben die Kuhen gesheissen."
 
Posts: 4386 | Location: New Woodstock, Madison County, Central NY | Registered: 04 January 2005Reply With Quote
one of us
posted Hide Post
quote:
Originally posted by ireload2:
...You hope the guy measuring the case heads knows enough to avoid it with:
Lee-Enfields,
99 Savages,
Ballards,Remington Rolling Blocks, trap door Springfields and most other BPCRs,
Krags,
Most lever guns, auto loaders and pumps.
Contenders,
those Mausers with soft receivers
Why?
 
Posts: 9920 | Location: Carolinas, USA | Registered: 22 April 2001Reply With Quote
One of Us
posted Hide Post
quote:
Originally posted by 45/70 Govt.:
Dial caliper, with an analog readout is calibrated in 0.00x "thousandths." And so "between" the calibration lines is going to be 0.0005" -- "five ten-thousandths." But it's going to be an "eyeball" and not a hard data accurate reading.




How to piss off old machinists:
Bet them I can better measure which are the + and which are the - pin gauges better with my dial calipers than they can with their micrometers.


What does it all mean?
Never make a bet based on projecting your expectations of your results on someone else.
 
Posts: 9043 | Location: on the rock | Registered: 16 July 2005Reply With Quote
One of Us
posted Hide Post
quote:
Originally posted by Tailgunner:

To a imagineer a "tenth" is 0.x
To a machenest, machine builder, gunsmith, and other skilled tradesmen, a "tenth" is 0.000x

The heat from your hand, holding the case or Mic frame, is enough to shift the measurments by a tenth.


-- Never heard that in the machine shops I hang in, which are admittedly not many. But then most of the machinists won't talk to me because I correct their English. *LMAO*

It makes sense. In linquistics that's called "an ellipsis." I'm betting it's a "contraction" of "ten-thou" ---> "ten'th"

I always forget about expansion from heat when handling measuring instruments. Five 'tenths' easy.
 
Posts: 825 | Registered: 03 October 2006Reply With Quote
one of us
posted Hide Post
quote:
Originally posted by Hot Core:
quote:
Originally posted by ireload2:
...You hope the guy measuring the case heads knows enough to avoid it with:
Lee-Enfields,
99 Savages,
Ballards,Remington Rolling Blocks, trap door Springfields and most other BPCRs,
Krags,
Most lever guns, auto loaders and pumps.
Contenders,
those Mausers with soft receivers
Why?


The actions listed are limited by their materials and/or design characteristics not by the yield strength of the case head and primer pocket.
 
Posts: 9207 | Registered: 22 November 2002Reply With Quote
One of Us
posted Hide Post
The machinists I know use call a 10th, 100 thousandths! and a ten-thousandth is just that. We do it that way in aviation too.
 
Posts: 187 | Location: SE Nebraska, USA. | Registered: 21 April 2006Reply With Quote
one of us
posted Hide Post
I have worked in and around machine shops since Jan 2, 1968, humm except for the 3 years that I went to school full time.

Everything is expressed in whole inches or thousandths or millionths or a gnats ass.

.1000 is a 100 thousandths.
A tenth is always 1/10 of a thousandth =.0001
A half tenth always means .000050 or 50 millionths.

A tenths indicator always has a resolution of .0001. A standard tenths "mike" always has the .0001 vernier scale on the barrel unless you have a digital. Then there were the big Pratt and Whitney bench "mikes" that direct read in .0001.
 
Posts: 9207 | Registered: 22 November 2002Reply With Quote
one of us
posted Hide Post
quote:
Originally posted by ireload2:
...The actions listed are limited by their materials and/or design characteristics not by the yield strength of the case head and primer pocket.
Hey ireload2, I'm a bit familiar with "some" of those Actions and cartridges they are chambered for. Have never seen a problem measuring Case Head Expansion in them.

Here are just a few examples:
M99s in 22-250, 300Sav, 308Win, 284Win, 358Win.
Browning BARs & BLRs in various high intensity cartridges from 270Wins through Belted Mags.
Various Semi-Auto M1s, M14s, M16s and clones in various hign intensity cartridges.
All kinds of Remington semi-auto and pump rifles in various high intensity cartridges.
All kinds of Winchester M100s & M88s in various high intensity cartridges.

Are you actually meaning to say some of the older low pressure "cartridges" will not work properly with Case Head Expansion(CHE)?

What am I missing?
---

By the way, Pressure Ring Expansion(PRE) will work in every centerfire rifle.
 
Posts: 9920 | Location: Carolinas, USA | Registered: 22 April 2001Reply With Quote
One of Us
posted Hide Post
Hot Core,
There are differences in learning styles.

Remember Denton?

There may be lots of ways to navigate through reality, but many are intolerant of other's systems.

To make matters worse, those who are stuck may also be egotistical and abrasive.

Just ignore the dumb stuff.
 
Posts: 9043 | Location: on the rock | Registered: 16 July 2005Reply With Quote
one of us
posted Hide Post
quote:
Originally posted by tnekkcc:
Hot Core,
There are differences in learning styles.

Remember Denton?
Hey tnekkcc, denton who? Big Grin
quote:
There may be lots of ways to navigate through reality, but many are intolerant of other's systems.
I've heard rumors of such stuff.
quote:
To make matters worse, those who are stuck may also be egotistical and abrasive.
Thank goodness " I'm " never like that.
quote:
Just ignore the dumb stuff.
Is this back to denton?!?!?!? rotflmo
-----

I really thought "ireload2" might just be aware of something I'm missing. I pick up some good tips here at AR from time to time. Not trying to argue with him, just trying to see if he knows something significant about CHE that I don't know.

By the way, I really do like your Extractor Groove Expansion(EGE) method. If it is growing there, no doubt Loose Primers are sure to follow.
 
Posts: 9920 | Location: Carolinas, USA | Registered: 22 April 2001Reply With Quote
One of Us
posted Hide Post
The great AR Denton - Hot Core debates reminded me of the 80's movie "Back to School" where Rodney Dangerfield as "Thornton Melon" challanges Paxton Whitehead as "Dr. Phillip Barbay" on a lecture on the real costs of running a buisiness. It is a clash between an over educated snooty proceedures person against a fun loving, obnoxious guy with real world experience.
 
Posts: 9043 | Location: on the rock | Registered: 16 July 2005Reply With Quote
one of us
posted Hide Post
So tnekkcc are you under educated or uneducated?
 
Posts: 9207 | Registered: 22 November 2002Reply With Quote
One of Us
Picture of El Deguello
posted Hide Post
quote:
Browning BARs & BLRs in various high intensity cartridges from 270Wins through Belted Mags.
Various Semi-Auto M1s, M14s, M16s and clones in various hign intensity cartridges.
All kinds of Remington semi-auto and pump rifles in various high intensity cartridges.
All kinds of Winchester M100s & M88s in various high intensity cartridges.


All these have a front end lockup, just like any Mauser-derived bolt action, and are not springy like rear-locking Winchesters, SMLE's, Savage M99's, etc.

Nevertheless, IMO the brass case is still the weakest line in any breechloading system, regardless of how it is locked for firing......


"Bitte, trinks du nicht das Wasser. Dahin haben die Kuhen gesheissen."
 
Posts: 4386 | Location: New Woodstock, Madison County, Central NY | Registered: 04 January 2005Reply With Quote
one of us
posted Hide Post
quote:
Nevertheless, IMO the brass case is still the weakest line in any breechloading system, regardless of how it is locked for firing......


That is correct and unless the case is properly supported it can let go at normal pressures.
Some of the springy actions will give you case head seperations with just few reloads at factory pressures.
 
Posts: 9207 | Registered: 22 November 2002Reply With Quote
one of us
posted Hide Post
/
 
Posts: 7857 | Registered: 16 August 2000Reply With Quote
One of Us
Picture of vapodog
posted Hide Post
Alf
The expansion of the case head is caused by forces perpendicular to the direction of the measurement where the balance of the case is forced to the chamber walls by direct pressure as the case walls are thin and allow for this direct pressure.

The only direct pressure on the case to cause case head expansion is that inside the flash hole and this is very small. CHE therefore is a result of the forces causing the solid brass to actually yield.


///////////////////////////////////////////////////////////////////////////
"Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery."
Winston Churchill
 
Posts: 28849 | Location: western Nebraska | Registered: 27 May 2003Reply With Quote
one of us
posted Hide Post
/
 
Posts: 7857 | Registered: 16 August 2000Reply With Quote
one of us
posted Hide Post
The rear approx .100 inch of the case head is solid except for the primer pocket and flash hole.
This solid section is a has clearance in the chamber and is not supported diametrally at normal pressures. This section is not sized by a sizing die either. This section of the case head will expand at very high pressure. If the pressure is so high that the solid head expands to the yield point of the brass, the primer pocket starts to loosen.
Continued firing with loads that slightly loosen it will ruin the case. A higher pressure over load will ruin the case with the first shot.
 
Posts: 9207 | Registered: 22 November 2002Reply With Quote
one of us
posted Hide Post
/
 
Posts: 7857 | Registered: 16 August 2000Reply With Quote
one of us
posted Hide Post
Hello ALF,
Your case heads are inside the barrel but they have some clearance between them and the chamber walls. The thinner case wall(body)ahead of the "solid" case head expands when the shot is fired until it is restrained by the chamber. Once the pressure falls off the case body springs back some due to the elasticity of brass permitting extraction.
The solid head does not expand against the chamber (diametrally) with normal loads. The juncture of the case wall and the solid head acts as a flexible seal or gasket.
The case wall is tapered therefore it takes more pressure to expand it further back toward the case head.




The chamber is tapered on most rifle chambers so the higher the pressure goes the further back the brass expands and the larger the expanded diameter gets. This increased diameter is easy to see with a chamber having a lot of clearance such as a Lee-Enfield. A Lee-Enfield also encloses its brass right up to the rim. However a LE has about .010" (.25mm) diametral clearance between the chamber and the solid case head. It produces a very prominent pressure bulge (pressure ring) that is easy to see with the naked eye. The diameter over the bulge is measured by some shooters to compare pressures in a given rifle. Some shooters also measure the diameter of the solid head to monitor pressure.
The solid head will actually yield if the pressure is high enough.... even if it is enclosed inside a chamber... even inside a 1885 High Wall Winchester design which is about as solid as you get. The yield occurs because the solid head still has the room to expand .003" to .006" inside the chamber. That does not look like much but it is enough for the primer to leak.
I have had two primers expand badly in a M91 Mauser, a design that encloses the case head pretty well. Neither was an over load. Neither put much of an expansion ring on the case. Neither leaked into my face. I only noticed because of a small curl of smoke at the head of the bolt before I opened it. I still have the two expanded cases. They are part of the reason that I do not depend on a micrometer much to keep me out of trouble. I used to make a living with micrometers and I know how to use them well.
 
Posts: 9207 | Registered: 22 November 2002Reply With Quote
One of Us
posted Hide Post
quote:
Originally posted by vapodog:
I no longer measure it. I use primer pocket expansion as my guide. If the primer pocket expands such that I can't press fit a new primer after a third firing I'm over pressure FOR THE BRASS I'M USING!!!!!

Brass hardness varies and relying on CHE can lead to assumptions that are poor.

Frankly I don't care if my pressures are at 75,000 PSI as long as the brass can handle it and primer pocket expansion tells me that.

Obviously other signs such as sticky extraction or hard opening bolt lift need to take precident. But CHE isn't in my bag of tricks anymore!


I AGREE COMPLETELY with Vapodog! His approach is my approach. The brass case is clearly the limiting factor in determining the PSI maximum, not a first-rate, well-built bolt action rifle, which will take over 150,000 PSI. One can reload at 65,000 PSI, but the primer pockets will loosen fairly quickly, and I don't care, because brass is relatively cheap and expendable. When the pockets start getting loose at 3 to 4 reloading, I throw the case away and start with a new one.
 
Posts: 3720 | Registered: 03 March 2005Reply With Quote
one of us
posted Hide Post
quote:
Originally posted by Ackley Improved User:
quote:
Originally posted by vapodog:
I no longer measure it. I use primer pocket expansion as my guide. If the primer pocket expands such that I can't press fit a new primer after a third firing I'm over pressure FOR THE BRASS I'M USING!!!!!

Brass hardness varies and relying on CHE can lead to assumptions that are poor.

Frankly I don't care if my pressures are at 75,000 PSI as long as the brass can handle it and primer pocket expansion tells me that.

Obviously other signs such as sticky extraction or hard opening bolt lift need to take precident. But CHE isn't in my bag of tricks anymore!


I AGREE COMPLETELY with Vapodog! His approach is my approach. The brass case is clearly the limiting factor in determining the PSI maximum, not a first-rate, well-built bolt action rifle, which will take over 150,000 PSI. One can reload at 65,000 PSI, but the primer pockets will loosen fairly quickly, and I don't care, because brass is relatively cheap and expendable. When the pockets start getting loose at 3 to 4 reloading, I throw the case away and start with a new one.


I back down the loads so the installation of primers wears out the primer pockets in most cases. Bad pun intended.
 
Posts: 9207 | Registered: 22 November 2002Reply With Quote
One of Us
posted Hide Post
quote:
Originally posted by vapodog:
I no longer measure it. I use primer pocket expansion as my guide. If the primer pocket expands such that I can't press fit a new primer after a third firing I'm over pressure FOR THE BRASS I'M USING!!!!!

Brass hardness varies and relying on CHE can lead to assumptions that are poor.

Frankly I don't care if my pressures are at 75,000 PSI as long as the brass can handle it and primer pocket expansion tells me that.

Obviously other signs such as sticky extraction or hard opening bolt lift need to take precident. But CHE isn't in my bag of tricks anymore!


I am close to that opinion, but I think, for rimless rifle cases, that it is less time, money, and effort to measure / track extractor groove expansion, than it is to feel primer insertion force.

That is because if some rounds are loaded with the same threshold load, some will not feel loose and all, and some will. They will all have the same extractor groove expansion.

And because is easier to measure extractor groove expansion than to feel primer insertion force when at the range or doing a range report write up.
 
Posts: 9043 | Location: on the rock | Registered: 16 July 2005Reply With Quote
one of us
posted Hide Post
quote:
I am close to that opinion, but I think, for rimless rifle cases, that it is less time, money, and effort to measure / track extractor groove expansion, than it is to feel primer insertion force.

That is because if some rounds are loaded with the same threshold load, some will not feel loose and all, and some will. They will all have the same extractor groove expansion.

And because is easier to measure extractor groove expansion than to feel primer insertion force when at the range or doing a range report write up.


I agree with your statement to an extent.
However if you eventually feel looser primer insertion force for what ever reason (including variations in primer size) you should reduce your loads regardless of what the mike says.
It is even less expensive to be conservative with pressures and not worry about miking the extractor groove.
 
Posts: 9207 | Registered: 22 November 2002Reply With Quote
one of us
posted Hide Post
quote:
Originally posted by tnekkcc:
I measure extractor groove expansion.
If I can measure any, the primer pocket will be loose in a few firings.

SAAMI specifications on primers and primer pockets per "Sinclair International's Precision Reloading & Shooting Handbook" 10th edition 1999

......................Depth min max diameter min max
small rifle primer pocket .117 .123 .1730 .1745
small pistol primer pocket .117 .123 .1730 .1745
Large rifle primer pocket .125 .132 .2085 .2100
Large pistol primer pocket .117 .123 .2085 .2100

.......................Height min max Diameter min max
Small rifle primers .115 .125 .1745 .1765
small pistol primers .115 .125 .1745 .1765
large rifle primers .123 .133 .2105 .2130
large pistol primers .115 .125 .2100 .2120"

As you can infer from the above, large rifle primer pockets and large rifle primers have interference between .0005" and .0020".

With .0005" of extractor groove growth, you may not notice a change in how hard it is to prime the case, but you will in 4 more firings, as it grows .0005" each firing.


Note at worst case conditions for small primers (another bad pun) the primer pocket and the primer are only a line to line fit. Any chance this is a typo?
 
Posts: 9207 | Registered: 22 November 2002Reply With Quote
  Powered by Social Strata  
 

Accuratereloading.com    The Accurate Reloading Forums    THE ACCURATE RELOADING.COM FORUMS  Hop To Forum Categories  Guns, Politics, Gunsmithing & Reloading  Hop To Forums  Reloading    How much case head expansion is too much expansion?

Copyright December 1997-2023 Accuratereloading.com


Visit our on-line store for AR Memorabilia