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Head space

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    Posted: February 20 2007 at 10:20am
With all the questions reguards Head Space I found this & thought it might be of use

 Headspace - What's the Scoop?
.
        Most modern rifle cartridges are referred to as rimless, but that's not 100 percent correct.  They all have a rim - it just doesn't extend past the wall of the case.   Rimless cases use the distance measured from the bolt face to the middle of the shoulder to determine headspace.  This length or measurement is standard.  It has been predetermined and accepted by the industry as a given length.
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............
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But what about the 303 British?  It's a rimmed cartridge!
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.......
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        Looking at the picture, you can see a shaded area just forward of the bolt face.  This is a recessed area that houses the rim when a cartridge is chambered.  The size of this area is measured from the bolt face to the end of the recess, when the bolt is closed.  How large this area is, determines headspace.  If this distance increases, your headspace is moving toward excessive.
        There are two "standards" for measuring headspace - military and SAAMI.

          Military    SAAMI
Go          .064        .064
No Go    .070        .067

                                                   Base Maximum/Field    .074         .070
        You'll notice that the military measurement is more generous.  Remembering that it was designed for war use, its dimensions are more in line with the original purpose.  The military gave no thought to reloading cases, so stretching was not an issue.  Military ball is a "one use" item.
        Most gunsmiths use the tighter SAAMI gauges when accessing headspace.  I said most - not all.  If your rifle is assessed as "serviceable" using military gauges, there is a distinct possibility that you will experience more case stretching.   If this is so, you might want to tighten up the headspace.

A Third Standard??  (Information provided by David Moses - Thanks!)

        There is one more standard for the .303 and that is the CIP norm. CIP states that the max ctg rim thickness R is 1.63 mm; min barrel relief R is also 1.63 mm. The max allowable headspace (in the case of the CIP, this is the air space between the max ctg R and the breech face) is 0.15 mm.  In our terminology, "go" would be 1.63 mm = 0.064"; "no go" would be 1.63 + 0.15 mm = 1.78 mm = 0.070". This is obviously based on military specs. Naturally, there is no "field" gage for CIP proof norms.
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Adjusting Headspace for the No 4 Rifle
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        If you've got a No 4 rifle, check the bolt head.  On the top, there is a number stamped into the metal.  The numbers go from "0" to "3".  Each increment of one adds 3 thousandths of an inch to the length of the bolt head.  If the number stamped there is 0, 1 or 2 you will be able to adjust the headspace by simply removing (unscrewing) the bolt head and installing another with the next highest number.  It will be necessary for you to check using the gauges again.
        If you've got a No 1 rifle, the fix isn't as easy.  Leave it with the gunsmith and let him work his magic.  The bolt heads in these rifles are not interchangeable like the No 4s.
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Back to the Chamber or (This Case Will Grow on Ya)
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       So, the cartridge is chambered and locked into place when you fully close the bolt.  When you fire the cartridge, the sides, shoulder and neck all expand outward to fit the chamber wall.  They do spring back slightly, but what you have, in effect, is a tailor made case that is unique within the world of Lee Enfields.  Most people notice that the shoulder moves forward when they hold a fired case up beside an unfired one.  Remember, shoulder position is not important for headspacing rimmed cases!
        This, my friends, is where many people start causing the trouble of cracks and separations.  They take this marvelously formed case, which, like a snowflake, is one of a kind, and run it through their full length die.... crushing it back to its approximate, original size.
        Subsequent firing and full length resizing overworks the brass and its life is reduced.  It's this complete cycle that prematurely ends its usefulness.  The solution is simple - neck resize!
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    Dave
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Post Options Post Options   Thanks (0) Thanks(0)   Quote allan Quote  Post ReplyReply Direct Link To This Post Posted: February 20 2007 at 10:36am
cheers dave..nice info there.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: February 20 2007 at 10:39am
A little more info

 

Lee Action - Trigger, Bolt, Safety, Headspacing, and Barrel Threading

The Lee-Enfield trigger assembly
This graphic shows the 2-stage trigger pull.

 

 

The SMLE bolt

 

 

A - Bolt head,
B - Extractor,
C - Bolt head lug which housed the extractor and extractor spring,
D - Bolt guide rib/locking lug
E - Cocking piece,
F - Left locking lug and
G - Gas vent hole in the bolt head

The Safety
This image shows the positioning of the Lee-Enfield safety/locking bolt in the cocked and uncocked positions.

 

 

Lee Enfield Barrel Threading

 

 

 

Headspace

Headspace adjustments can be easily accomplished with the Lee-Enfield, simply by replacing the bolthead. As the Enfield rifle was a military, combat designed rifle there are actually two sets of specs listed for headspace. These are:

 

 

Remember that the .303 is a rimmed cartridge, so headspace is the distance between the bolt face and the cartridge rim. Unlike the rimless cartridge, which draws it's headspace from bolt face and the cartridge shoulder.

For the SMLE/No1 family of Enfield's adjusting headspace can be accomplished by swapping different boltheads until one is found to produce the desired distance. This is necessary because the SMLE was only manufactured with one size of bolthead and the unit armourer stoned the bolt face to correct for headspace.

In designing the No4/No5 family of Enfield's, this minor headache was cured by producing 4 different bolthead sizes. This allowed the unit armourer and now the private owner to simply select the correct bolthead to quickly adjust headspace to specs.

Each No4/No5 bolthead is numbered 0, 1, 2, or 3. Each number specifies an increase in length, nominally .003 of an inch.

 





       Dave
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Cookie Monster Quote  Post ReplyReply Direct Link To This Post Posted: February 20 2007 at 10:42am
Excellent information dave
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ed Hill Quote  Post ReplyReply Direct Link To This Post Posted: February 20 2007 at 12:14pm
For the new folks, please note that not all bolt heads will fit properly. They should screw on tight, and go just past the vertical. If it won't turn to the vertical position it needs some adjustment, if it goes past the vertical more than 20 degrees, you need to try another bolt-head.
Another fix if the bolt head won't do it, is try a different bolt. If your bolt lugs are set back excessively it will give headspace problems. A less worn bolt may correct it. Again, have it checked by your gunsmith if you're swapping bolts around.
Ed
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lithgow Quote  Post ReplyReply Direct Link To This Post Posted: February 20 2007 at 8:31pm
Not bad info dave. Where did you come across it?
The only bit I think is wrong is where he states that the No1 rifle bolt head is not interchangable. They certainly are although because they are not numbered, one needs access to a few to find the one that is correct.
All No1 bolt heads start out the same length more or less, The armourer then stones the bolt face to get it right.
With regards to the No4 bolt head. Even 2 bolt heads marked with the same number may vary in length due to manufacturing tolerances.
I would not advocate swapping bolts without checking the bearing of the locking lugs. If an Enfield headspace will not come within spec by changing bolt heads then I would take it to someone who knows about Lee Enfields for repair. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: February 21 2007 at 4:47am
It was something a Mate e-mailed me ,after we'd been discussing the head space question. I'm with you on the isue of the mk1  as over the years I've had ocassion to have to change them over. sometimes I had to hone the face down to obtain the correct head space . I do not recomend thougth that this is a practice for the backyard gunsmith !

      Dave  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Raider Quote  Post ReplyReply Direct Link To This Post Posted: February 21 2007 at 5:21am
Thanks! Great info.
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: February 21 2007 at 7:02am
Here is a picture of my bolt head,  my rifle swallowed a field gage, so I have too much headspace.  I have found a bolt head that is .719 I am thinking of buying.  Notice to in the pic the marking  I thought was a number '4'




I wanted you all to notice the offset when the bolt head is tight on the bolt.  Is this normal or something that changes too.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote White Rhino Quote  Post ReplyReply Direct Link To This Post Posted: February 21 2007 at 7:07am
Thanks Dave!  gona get me a few the next time i see some for sale.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ed Hill Quote  Post ReplyReply Direct Link To This Post Posted: February 21 2007 at 10:00am
CJROCK, my Duh! I was thinking the No.4 rifle. As noted above, the bolt heads on the No.1 are not marked. The offset is normal and looks OK.
What size field gauge did you use? If it wasn't a .074, I'd try and find one and try it again.
Ed 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Cookie Monster Quote  Post ReplyReply Direct Link To This Post Posted: February 21 2007 at 11:01am

Headspace Gages

The best way to check your rifle chamber for safety, with exclusive Forster quality.

Forster%20Precision%20Headspace%20Gages

Click%20Here%20for%20Detailed%20Instructions%20for%20Use%20with%20Forster%20Headspace%20Gages

Every gunsmith knows that proper use of a headspace gage is the most reliable way to test the length of a rifle chamber. "Headspace" is the distance between the face of the breech and the base of the cartridge when the action is closed, and excessive headspace can be dangerous as well as impair accuracy. For instance, unsupported brass fired in a rifle action with excessive headspace can rupture, allowing gas to blow rearward like a rocket exhaust.

Because your safety is on the line, Forster Headspace Gages are made with painstaking care and exacting manufacturing standards to ensure accurate testing of your rifle's chamber.

Important Guidelines For Measuring Headspace:

  • If a rifle closes on a GO gage, the rifle chamber will accept any ammunition that is made within S.A.A.M.I. (industry standard) specifications.
  • If a rifle closes on a NO GO gage, the rifle chamber might have excessive headspace. Most gunsmiths chamber a rifle's headspace between the GO and NO GO dimensions.
  • If a rifle closes on a FIELD gage, rifle chamber is dangerously close to or already over the S.A.A.M.I. specified maximum chamber size. If chamber headspace is excessive, the gun should be taken out of service until it has been repaired.
  • When checking headspace, a stripped bolt and removal of the firing pin will make it easier to feel the action closing on the gage. Some shooters are under the misconception that the headspace of a gun is fixed over the life of the firearm. Headspace can increase after repeated use of ammunition that causes too much pressure. Handloaders should routinely check headspace every thousand rounds.

Headspace Gages for Rimmed Calibers

Caliber GO
Length
GO
Order no
.
NO GO
Length
NO GO
Order no
.
FIELD
Length
FIELD
Order no.
219 Wasp & Zipper .063 BG3030G .067 BG3030N .070 BG3030F
22 Sav. H.P., 25-35 .063 BG3030G .067 BG3030N .070 BG3030F
30-30, 32 Win. Sp. .063 BG3030G .067 BG3030N .070 BG3030F
32-40, 38-55 .063 BG3030G .067 BG3030N .070 BG3030F
22 Rimfire .043 HG22RimG .046 HG22RimN .049 HG22RimF
300 Mag. & all belted Mags .220 BG300MG .223 BG300MN .226 BG300MF
7.62 X 54 Russian - - .071 BG762RN .074 BG762RF
303 British .064 BG303G .067 BG303N .070 BG303F
30-40 Krag .064 BG3040G .067 BG3040N .070 BG3040F
30 Carbine 1.290 HG0030G 1.296 HG0030N 1.299 HG0030F

Headspace Gages for Rimless Calibers

Caliber GO
Length
GO
Order no
.
NO GO
Length
NO GO
Order no
.
FIELD
Length
FIELD
Order no.
22-250 Remington 1.574 HG2225G 1.579 HG2225N 1.583 HG2225F
22 PPC 1.145 HGOPPCG 1.149 HGOPPCN 1.154 HGOPPCF
220 Swift 1.806 HG0220G 1.810 HG0220N 1.814 HG0220F
222 Remington 1.294 HG0222G 1.297 HG0222N 1.300 HG0222F
222 Remington Magnum 1.493 HG222MG 1.496 HG222MN 1.499 HG222MF
223 Remington* 1.464 HG0223G 1.467 HG0223N 1.470 HG0223F
243 Winchester 1.630 HG0243G 1.634 HG0243N 1.638 HG0243F
308 Winchester 1.630 HG0243G 1.634 HG0243N 1.638 HG0243F
358 Winchester 1.630 HG0243G 1.634 HG0243N 1.638 HG0243F
7mm-08 Rem. 1.630 HG0243G 1.634 HG0243N 1.638 HG0243F
  1.630 HG0243G 1.634 HG0243N 1.638 HG0243F
244 Remington 1.777 HG0244G 1.781 HG0244N 1.785 HG0244F
250 Savage 1.579 HG0250G 1.583 HG0250N 1.587 HG0250F
6mmPPC 1.145 HGOPPCG 1.149 HG0PPCN 1.154 HGOPPCF
6.5 SKAN 1.831 HGSKANG 1.835 HGSKANN
Not Available
6.5 x 55 Swede 1.779 HG6555G 1.785 HG6555N 1.789 HG6555F
257 Roberts 1.794 HG0257G 1.800 HG0257N 1.804 HG0257F
7mm Mauser 1.794 HG0257G 1.800 HG0257N 1.804 HG0257F
280 Remington 2.100 HG0280G 2.104 HG0280N 2.108 HG0280F
284 Winchester 1.810 HG0284G 1.815 HG0284N 1.817 HG0284F
25-06 2.049 HG3006G 2.055 HG3006N 2.058 HG3006F
270 Winchester 2.049 HG3006G 2.055 HG3006N 2.058 HG3006F
30-06 Springfield 2.049 HG3006G 2.055 HG3006N 2.058 HG3006F
8mm x 57 Mauser**

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: February 21 2007 at 10:25pm
 Ed,  My field gage is a .070 size.  not .074 so I probably need to get another one to test with.

Thats only  4 hundredths of an inch bigger!  the Bolt head I found is .719 and my old one is .630 a difference of  .089.

if my Headspace is just bigger that .070 say its .080  and I lengthen my bolt to .089 my head space would go from .080 to .169.  Thats way too big. 

say for instance if my head space is .080 it needs to be .013 smaller to get me to .067 (.080 - .067 = .013)

My bolt head is .630 + .013 = .643 (new Bolt head size)

This is all true if my actual head space is .080 which there is no way I know to actually measure it accurate with out a set of gages field gages.

I never knew that I would be doing so much math just to shoot a rifle!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lithgow Quote  Post ReplyReply Direct Link To This Post Posted: February 21 2007 at 11:01pm
Your rifle may not close on a .074 field gauge.
When checking headspace, You are looking for the slightest "feel". You can sometimes push the bolt handle closed on a gauge after contact has been made, you should not do this as it does the gauge no good.
A lot of newbies have made the mistake of thinking their enfield has failed when in fact it has passed.
I agree with Ed, find a .074 and try again. The rifle may pass.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: February 21 2007 at 11:08pm
its very hard to feel with the cocking spring pushing against you.  should I remove the spring?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lithgow Quote  Post ReplyReply Direct Link To This Post Posted: February 21 2007 at 11:23pm
If you have the tools for dissasembling the bolt it is always best done with the bolt stripped.
My father maintains that it is the correct procedure to strip the bolt first but with experience it can be done with the bolt assembled. It is certainly easier to feel with the bolt stripped.
A bolt dissasembly tool is easily made if you dont have one. 
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