303 British Head space

[Highpower]

From the British War Office (30th September, 1931)

INSTRUCTIONS FOR ARMOURERS
PART II
SMALL ARMS
CHAPTER I
RIFLES
Drawing Nos. S.A.I.D. 2058; 2059; 2267; 2268; 2269.

7. To fit new bolt-head to Rifles No. l.—(Spare part bolt- heads, marked “S” on the top, are longer at the front.) Assemble the bolt-head to the bolt, insert it in the body, and test with .064-inch No. 1 gauge; should the bolt not close over the gauge, remove the bolt-head from the bolt, and having placed a piece of emery cloth (No. F) on a flat surface, rub the face of the bolt-head on the emery cloth, maintaining a circular motion in order to preserve a flat surface, until sufficient metal has been removed to enable the assembled bolt to close over the gauge. The bolt should not close over the .074-inch No. 1 gauge. Care should be taken to keep the-face of the bolt-head flat and square. After fitting and adjusting, the top front edge of the face of the bolt-head is to be rounded to a radius not exceeding .02-inch.

Note.—When it is found that the bolts of several rifles turn over the 074-inch No. 1 gauge, the bolt-heads should be ex- changed among such rifles, as, owing to the varying lengths of bodies and bolts, bolt-heads which are too short in one rifle may be serviceable in another. Bolt-heads that have been replaced in rifles by longer ones, should be kept by the armourer and used whenever possible in rifles requiring the bolt-head replaced, so as to avoid unnecessary use of new spare part bolt-heads. Part-worn bolt-heads held as required by armourers in accordance with the foregoing need not be accounted for as part of the annual allowance of new spare parts.

Section 6.—Description and Use of Armourers’ Gauges
and certain Tools

Gauges

Gauges, armourers’, .064-inch No 1 and .074-inch No. 1 for rifles No.1.-These gauges are used also for .303-inch machine- guns, with the exception of the .074, which is not used for Vickers guns.
The gauges are for testing the distance of the face of the breech bolt from the end of the chamber, or, in other words, the cartridge head space. The diameter of the rim conforms approximately to that of a maximum cartridge. The portion which enters the chamber is merely a guide—not a gauging feature.
When closing the bolt on the gauge, the trigger should be held back to prevent cocking and snapping, which is liable to cause the rim of the gauge to be broken off. Care should also be taken to avoid drawing the gauge back on to, and so damaging, the ejector. In no circumstances must these gauges be used for No. 3 rifles, as the rim is slightly too large in diameter for the recess in the face of the bolt of those rifles, and, consequently, in addition to giving a false gauging result, will cause damage to the wall of the recess or the projecting horns on the left recoil lug of the bolt.

Gauges, armourers’, .064-inch No.2 and .074-inch No.2 for rifles No 3.—These gauges are special to No. 3 rifles and must be used only for those rifles. They differ from the No. 1 gauges in that the diameter of the rim is smaller and the portion which enters the chamber is longer, the front end being tapered off.

The instructions given for the use of the No. 1 gauges are applicable also to the No. 2 gauges.
The No. 2 gauges are obtainable on loan from store when required.

[CLARKMAG]

The longer heads are not available in US or Canada as of ~ 7 years ago.
At one time there were some left.

I have built a fixture for Silver soldering a shim on the bolt face.

The SAAMI registered cartridge and Chamber dimensions are .054 to .064 cartridges and .064 to .071" chamber.
That makes .017" of stretch for the case wall possible.

This would be considered intolerable in any other cartridge.

Combine that with the bolt lug at the rear of a hollow bolt body that compresses under pressure, and we might get short brass life.

If I measure actual brass I get a spread that looks like:
HXP 75 surplus unfired cartridges around the rim
59 61
58 61
59 60
GB 1943 VII surplus unfired cartridge
60 62
Remington Kleanbore [circa 60's] unfired cartridges
58 62
56 60
59 60
56 62
WW Superspeed [circa 60's] unfired cartridges
59 62
59 63
59 62
60 63
Norma [circa 60's] unfired cartridges
58 61
57 60
58 61
60 61
RP [circa 80's] unfired cartridges
58 60
56 58
59 61
58 61


HXP 75 surplus once fired brass
56 59
57 62
58 62
56 56
56 60
58 62
60 62
60 62
54 57
WRA 69 surplus once fired brass
59 60
DI Z 1943 surplus once fired brass
60 62
60 62
60 62
60 61
62 63
62 63
63 63
61 62
RP commercial once fired brass
60 61
60 62
60 62
60 63
60 60
58 60
SuperSpeed commercial once fired brass
59 62
60 61
59 62
WW Super commercial once fired brass
60 63
60 62
61 62
60 64 [nicks on rim]
RP Nickel plated commercial new brass
60 61
59 59
59 60
59 60
60 61
59 60
RP commercial new brass
58 61
58 61
59 60
59 61
58 61
57 58
58 59
59 60

If I were chambering a rifle, I would aim for .062"

[Theiskell]

Let me start by saying THANK YOU! To all who have helped. I have been on a number of forums but none with the willingness to help that you have all shown. This is a very sentimental gun to me and you have helped bring it back to life.
I checked the head space using a .064 “go gauge” . The bolt close with no resistance. Then I added a .003 shim to the face of the go gauge the bolt went just past the ½ way point. With my limited knowledge to me the head space looks good. Does this sound correct? If it is, I guess my problem all along has been bad cases. WOW!

[38_Cal]

With your GO gage and a .003" shim and getting resistance to closing...you're good to go! Check/adjust/replace your dies and start with some new brass and you should get many more years of fun from this rifle.

David

[TRX]

If you're reloading, the simplest solution is to back off on the sizing die so the shoulder doesn't get pushed back any further than it takes to fit the chamber. Then draw a line down the side of each case with a felt tip pen, and make sure you load the magazine with all the cartridges clocked the same every time.

Due to problems with ammunition being out of spec during WWI, most Enfields had their chambers opened up for extra clearance. Some of them were hogged out with what looks like reamers for other cartridges; "two-step" shoulders aren't uncommon. Also, it's common for the chambers to be noticeably out-of-round. Even so, they performed acceptably with new military spec ammunition.

As for headspace in particular... #4 bolt heads are rare and expensive, and most SMLEs seem to have #3s to start with. You can solder a shim onto your bolt head, or build up the end with braze and face it off. A shim and super glue would work, though you'd have to see how it holds up to whatever you use for cleaning. Yes, there's a lot of case head thrust, but the shim isn't going anywhere; the only reason for solder or glue is to keep it from falling off while you work the bolt.

That said, most SMLEs will close on the "no go" gauge, including ones that were re-arsenaled and were re-stamped as meeting all specifications. I don't know that the British Army ever published a revised headspace figure, but whatever they considered acceptable is way more than the US SAAMI spec for commercial ammunition. The .303 is a medium-pressure cartridge, and the SMLE is much stronger than it looks.

FYI

[xs hedspace]

The Brits built their combat rifles with wide tolerances on headspace, so dirty ammo will still chamber and fire. Just do neck sizing, and your case life will improve.