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Normal Topic 303 headspace gauge (Read 1663 times)
raydafish
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303 headspace gauge
Feb 12th, 2019 at 5:06am
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anyone have a headspace gauge for a 303 lee enfield that I could borrow or buy?
cheers
  
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Cuzza
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Re: 303 headspace gauge
Reply #1 - Oct 2nd, 2019 at 5:15pm
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Did you find one? i have one only not helpful i know and i cant remember which one, negative or positive!
  
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noelfj
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Re: 303 headspace gauge
Reply #2 - Oct 2nd, 2019 at 8:55pm
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I have on occasion partly pushed the primer out a little and then closed the bolt onto it, forcing the primer back in as far as the bolt can push it.
Then I measure the amount the primer sticks out of the case.
It stands to reason that in order to make the measurement I have removed the case from the rifle.
You will need a depth gauge and the ability to use it.
Make sure the case fits into the chamber without force and the rim is in fact upon its support.
  
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grandpamac
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Re: 303 headspace gauge
Reply #3 - Oct 3rd, 2019 at 5:14pm
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Greetings,
noelfj is on the money with using the primer projection as a guide to head space in the .303. Currently, 40 years after swearing of Lee Enfields forever, I am loading for two. Recently I replaced the barrel on one with a newish two groove barrel that had been skulking is the cupboard for a decade or two. Previously I had measured the head space on both using the protruding primers on light loads coming up with 1.65 mm for one and 1.75 mm for the other. Head space here is the total of the primer projection and rim thickness. There seems to be some disagreement on the correct head space dimensions for the .303 cartridge. I suspect that 1.6 mm min to 1.7 mm max was used for target rifles and 1.7 mm min to 1.88 mm max ( 2.13 mm wartime max) was used for infantry rifles. Cartridge case rim thicknesses in stock measure from 1.4 mm to 1.7 mm with most military cases measuring 1.55 mm plus or minus a bit.
The gunsmith that replaced the barrel for me did not have head space gauges so I asked him to turn the barrel in to the shoulder and I would measure it when the rifle returned. First I used noelfi's method of partially seated primer (fired) in a full length sized case and came up with a head space of about 1.75 mm, the same as the original barrel. Further measurements from cases fired with light loads have supported this.
I just use a metric dial vernier for measurements. You can either use the depth gauge to measure primer protrusion or measure the case length to the head and over the protruding primer. Subtracting former from the latter gives you the protrusion. I have done it both ways and am able to get repeatable results.
All this may seem pretty rough and ready to some but moderately excessive head space provided you do not full length size the cases with the die hard down on the shell holder. My loads are all mild and cases can be neck sized repeatedly and still chamber, in my rifles at least.
Currently I am working with some chronographed light loads in my .303 rifles, one two groove and the other five groove and will report via a post in the near future.
Regards Grandpamac.
  
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