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Size 3 bolt head for BSA (M47C) No. 4k. 1 rifle |
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DisasterDog 
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Joined: February 21 2025 Location: Brewery Status: Offline Points: 256 |
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 Posted: January 05 2026 at 8:58am |
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It used to be a special order item from Forster.
As the saying goes, “usually the excessive headspace is between the ears of American collectors”.
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Sauron
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Joined: November 30 2025 Location: Virginia, USA Status: Offline Points: 90 |
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Posted: January 05 2026 at 9:06am |
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Guilty as charged....until very recently. Appreciate ya'll straightening me out. :) Best, |
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britrifles
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Joined: February 03 2018 Location: Georgia, USA Status: Offline Points: 8404 |
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Posted: January 05 2026 at 9:27am |
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I'm not sure why the fixation on headspace. But, it can be a safety issue if it exceeds the 0.074 FIELD maximum.
The only likely reason it would be excessive is if someone intentionally swapped out a longer bolt head for a shorter one (because the longer bolt heads are getting hard to find). It might also get excessive if the rifle had the entire bolt swapped out (mismatched to the rifle), like we have seen in some imports.
For people who reload, and want decent life out of your brass, try to find a bolt head that gives you 0.064 to 0.068. Headspace approaching 0.074 will not cause a case failure on one firing, but you'll probably only get a few reloads out of the brass before the web area just above the solid case head thins and cracks. |
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Shamu
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Posted: January 05 2026 at 12:38pm |
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Actually they always were, but you had to know "the trick of the Day". Originally "Okie Gauges" made both a set of Go, No Go, & FIELD with the correct dimensions, AND a "FIELD" alone. When the owner passed they stopped but there were some available from Australian sources. & finally the sneakiest trick of all. "Moist Nugget" 0.074" gauges have always been available, but they're not described as "Field" because they're for the old Russian cases. But they were identical in all but name to a .303 British "FIELD"  |
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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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M@tt
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Joined: November 16 2025 Location: SE England, UK Status: Offline Points: 45 |
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Posted: January 06 2026 at 2:39am |
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I notice the Brownell's images show 0.064, 0.067 and 0.070 on the side of the gauges. I know the images do not always represent the actual product.
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Sapper740
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Posted: January 06 2026 at 3:42am |
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Correct. The Forster "Field' gauge in the Brownells' link is for a .070" gauge, not .074". If you look closely at the gauge you can see .070 is stamped on it.
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Sauron
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Posted: January 06 2026 at 6:09am |
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The one I got says .074. The one I bought a couple of months ago is .070. I'm guessing they just haven't updated the images yet. Best, |
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Zed
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Posted: January 06 2026 at 9:16am |
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The confusion comes from the SAAMI figures which have the maximum headspace incorrectly set at 0.070".
Where as the British military spec' has always been 0.074". Once you are sure of the headspace using the British 0.074" gauge, you can work out what bolt head is required. It's more important to search for the correct measurements than the number stamped on the head. Because some variations in size mean that you might have some overlap between the figures, a maximum size No 2 bolt head maybe a couple of thousands bigger than a minimum size No3 etc. If you measure your bolt head, on both sides to get the measurements. ( I have seen some that are not identical side to side) Then you can calculate what size is required.
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DisasterDog
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Posted: January 06 2026 at 9:34am |
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Then you have to make sure it clocks correctly. Just because you find one the correct length doesn’t mean it’ll have the right overturn.
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britrifles
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Posted: January 06 2026 at 10:46am |
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I think the "NOGO" gages (which are typically smaller than the SAAMI MAX) were introduced by manufactures of the gages for gunsmiths to use when installing and headspacing a new barrel. That's why we see .303 NOGO gages of 0.067-0.068. SAAMI specs do not define a "NOGO" gage, only Minimum and Maximum.
The current SAAMI .303 drawing shows 0.071 in. as the "maximum". A quick glance thru the SAAMI chamber drawings show 0.007" difference between max and min is consistent for rimmed cartridges, while 0.010" seems common for rimless. This is likely a source of confusion for gunsmiths examining a Lee Enfield, 0.071 is the SAMMI MAX chamber headspace, and not in accordance with British military specification FIELD maximums (which is 0.074, +0.010" over the minimum). If you can't find a 0.074 FIELD gage, you could use a small piece of a steel feeler gage between the bolt head and the particular MAX gage you have; i.e. if your gage is 0.070, then add a 0.004" steel shim (or feeler gage). |
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Canuck
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Posted: January 06 2026 at 4:00pm |
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You can also check head space using 'plastigauge', the same thing engine builders use to measure crank and rod bearing to journal clearances.
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DisasterDog wrote: