.303 Enfield Bore Diameter question

[Armorer]

Within the past couple of months, I bought a 1941 Golden State Arms Santa Fe Supreme in .303 from another member here. I finally got around to slugging the bore tonight and to my surprise, it came out right at .307 Could this be a result of the re-barreling job that GSA did? That is why it doesn't mic as large as your typical Enfield? Maybe I answered my own question.
On another note, I have a model 1911 Chillean Mauser that I put a scope mount on and did a bolt handle job. I needed to slug it as well and it came out right at
.308 with my micrometer. Should be a good shooter I reckon.

Thoughts?
Armorer

[madsenshooter]

Answering your own questions is ok, but you gotta watch out for questioning your own answers, or maybe not...

[Armorer]

Answering your own questions is ok, but you gotta watch out for questioning your own answers, or maybe not...

There is that...lol

[Char-Gar]

Madsen... My son has a M.S. in Geology from Texas A & M. They taught him to answer the question and then question the answer. A critical thinking approach. Works for him, although he can be a PITA sometimes with that approach.

[madsenshooter]

If you have to question your answer, then you probably didn't think the question through before giving said answer. It appears Golden State used US made barrels rather than British or Canadian surplus. During those troubled times, there may have been some US companies making barrels for the Brits, and Golden State found some of them, or they turned other US barrels. That means you'll have a lot more molds to chose from, and don't have to go with the fat boolits all the rest of the Enfield shooters have to. I have Krags with bigger bores than your 303! Found some nice pics of your rifle on the web. Though the bore is tight, I'd still play with larger sizes to try to get as much support for the heel of the bullet as possible from the neck. The less the boolit can tip, the better, so my Krags tell me. (Gotta do something about these talking guns!)

[Multigunner]

If its a five groove bore and you place the mike or caliper jaws directly opposite each other you'll catch one raised groove impression in the center and the edges of two on the other side, which gives a false low reading.

I have heard of a few Enfield bores measuring as small as .307, these being wartime production and far off the acceptance mark of min.313- max .319.
There were a number of alternative bores for the No.4 including four , five, or six grooves and widely varying bore sizes. I've heard they even made a few six groove bores with righthand twist rifling.

A replacement barrel turned from a nominal .30 barrel blank is not impossible.

A .303 cartridge with .311 bullet fired in a .308 bore gives an increase in chamber pressure of about 8%, over 3,000 PSI higher than the same cartridge fired with a .311 bore. Withing the safety limits of the action, but could cause excessive wear and other problems.

On the upside you could try .308 bullets in handloads. If they proved accurate .30 bullets are available in a much greater variety of styles and bullet weights.

[Armorer]

If its a five groove bore and you place the mike or caliper jaws directly opposite each other you'll catch one raised groove impression in the center and the edges of two on the other side, which gives a false low reading.

I have heard of a few Enfield bores measuring as small as .307, these being wartime production and far off the acceptance mark of min.313- max .319.


I just went back and measured it again, and it is a 5 groove bore. Just like you said, I was getting a small reading. The barrel is not however an Enfield barrel, but was replaced by GSA.
So, is there a way to properly size my bore considering the way the grooves are arranged? So I will know what to size my boolits at.

Armorer

[Multigunner]

I just went back and measured it again, and it is a 5 groove bore. Just like you said, I was getting a small reading. The barrel is not however an Enfield barrel, but was replaced by GSA.
So, is there a way to properly size my bore considering the way the grooves are arranged? So I will know what to size my boolits at.

Armorer

There were still unissued replacement Enfield barrels available when those carbines were assembled, but No.5 barrels and No.4 barrels cut and turned to No.5 dimensions.
Look for British Proof marks on the barrel just ahead of the receiver ring. Not all No.4 barrels have recognizable markings, but most barrels should carry some sort of proof mark.

Its not that easy to find commercially manufactured .303 barrel blanks in the USA.
And making barrels when unissued barrels were available would not be cost effective.

[curator]

If you intend on shooting cast you need to measure the throat diameter. a throat slug will not have grooves and is easy to measure with conventional micrometer. Size boolits to this size or no more than slightly (.005) under for best accuracy and reduced leading.

[goofyoldfart]

I just went back and measured it again, and it is a 5 groove bore. Just like you said, I was getting a small reading. The barrel is not however an Enfield barrel, but was replaced by GSA.
So, is there a way to properly size my bore considering the way the grooves are arranged? So I will know what to size my boolits at.

Armorer

Armorer : Take a 1 or 2 thousandth feeler gauge and wrap around the bullet tightly and then measure with a micrometer while holding the feeler gauge tight. Get measurment and subtract double the thickness of the feeler gauge. you'll then have your measurement. Good luck and good shooting. God Bless to you and yours. :)) ;):lovebooli

Goofyoldfart < aka GOF>

[Four Fingers of Death]

....so my Krags tell me. (Gotta do something about these talking guns!)

I've heard of people hearing voices, but never from guns, :D

One of my son's friends has a psych condition and hears voices, etc. However, he has good insight into his condition, takes his medicine, works hard, is married with a young child and is paying off a house. A real credit to him, considering his condition.

I walked out of a shop downtown one day as he walked past, I was right behind him and said 'G'Day Duncan!' He just shook his head and started walking faster. I told my son about this and he laughed and said 'Duncan only listens to voices that are in front of him and he can see the lips moving! He ignores everything else.' A sensible approach considering.

I was speaking to an old gunsmith years ago and he said that he has cobbled up 303 barrels from all sorts of donors. Real lucky dip with 303s (and 310 Cadets). they are more often loose rather than tight though. Be a real boon to a jacketed bullet shooter I suppose.

[Armorer]

Armorer : Take a 1 or 2 thousandth feeler gauge and wrap around the bullet tightly and then measure with a micrometer while holding the feeler gauge tight. Get measurment and subtract double the thickness of the feeler gauge. you'll then have your measurement. Good luck and good shooting. God Bless to you and yours. :)) ;):lovebooli

Goofyoldfart < aka GOF>

Great idea, thank you!

Armorer

[MBTcustom]

Listen to curator. When casting boolits for rifles, or fighting a superior enemy, Always go for the throat! :bigsmyl2:

[303Guy]

When I saw .307 bore I thought "I have one of those!" But it seems you are talking about groove diameter. Well, I have a .307 bore diameter barrel. Perfect for cast or paper patching!:-o That's because a boolit that fits an unfired case also fits the throat. And it's throat fit that counts.

[Four Fingers of Death]

Listen to curator. When casting boolits for rifles, or fighting a superior enemy, Always go for the throat! :bigsmyl2:

Thats good advice in a fight as well! lol

I'm an old man now and have never been one for getting into fights (although I have been paid to break up a lot), but nowadays I'd want to end it real quick, cause I just about run out of puff thinking about it.

[Canuck Bob]

A replacement barrel turned from a nominal .30 barrel blank is not impossible.

A .303 cartridge with .311 bullet fired in a .308 bore gives an increase in chamber pressure of about 8%, over 3,000 PSI higher than the same cartridge fired with a .311 bore. Withing the safety limits of the action, but could cause excessive wear and other problems.

I had heard this before. Could I ask were you got this info please? I once read of a test Ruger did on a run of 303 #3 for a Canadian Arctic dealer with 308 barreled 303 Brit rifles. They are reported to have found increased pressure of no more than 5000 psi. with factory ammo. I've never been able to confirm this is true.

[Armorer]

Listen to curator. When casting boolits for rifles, or fighting a superior enemy, Always go for the throat! :bigsmyl2:

LOL...you know it amigo!:Fire:

[Multigunner]

I had heard this before. Could I ask were you got this info please? I once read of a test Ruger did on a run of 303 #3 for a Canadian Arctic dealer with 308 barreled 303 Brit rifles. They are reported to have found increased pressure of no more than 5000 psi. with factory ammo. I've never been able to confirm this is true.

I'd read of the Ruger No.1 rifles , the Ruger Single Shot not the SMLE, being made to test available .308 bullets in the .303 many years ago, then several years ago I found a thread on another board where a Ruger employee reccounted the tests.
Ruger has lately announced a .303 chambered No.1 single shot, but I'm pretty sure these have the nominal (as in commercial specs) .311 bore size.

Haven't seen one yet but theres been a lot of interest in the rifle in some circles.

The tests the Ruger employee posted of gave something over 3,000 psi increase, but these were probably lower pressure loads than those that gave a higher increase.

I'd not seen a No.3 before, and its apparently out of production at this time.

The No.1 is a heavy duty action, which may be why it would be chosen for experimentation.

[303Guy]

.311 bore size.That's groove size.:wink: Bore size is .303 nominal. (It really is important to say it right with the 303 brit as I have just learned. If I say to you .307 bore you might think I mean .307 groove diameter but no, I mean bore. I haven't measured the groove yet - the rifling is pretty deep. .316? .318? The boolits I am going to use that fit the throat are .319!:holysheep).

[JeffinNZ]

Multigunner: Ed Harris reported over on the CBA forum that during his time at Ruger they tested .311 bullets down .308 barrels with no significant increase in pressure. Sounds odd to me but Ed knows his stuff.

The discussion came up re the Ruger No.1 .303 just released recently and whether or not it would have a .311 groove; which it does.

[MBTcustom]

I just got done messing around with a .303 barrel and at this point I'm convinced that there was just no hope for it. The bore measured .303 but the groove diameter was almost .320 and the throat was the same size as the grooves. There was just too much groove depth to get a good gas seal and let me tell ya, I tried every boolit style known to man trying to get the stupid thing to shoot. I couldn't PP it accurately because the paper couldn't seal the rifling from the pressures. I couldn't do GG boolits because the throat would not allow me to go oversize by any amount that would help. the best accuracy I got was with PP j-words because they were stiff enough to press the paper into the grooves and create a good seal. I was disgusted that I had to pay premium price for projectiles that I would have to spend premium time with to get a semi-kinda-OK-sorta-group with. So I gave the barrel a heave (figuratively speaking) and replaced it with something better. Getting an old rifle to shoot like a tack driver is possible if you stumble on the right barrel, but sometimes it just aint worth it. Especially when a new barrel is so cheap.

[303Guy]

... at Ruger they tested .311 bullets down .308 barrels with no significant increase in pressure.3000psi would not be significant for a Ruger No1 with a cartridge that only develops 50,000psi. As I've said, the two-groove No.4 has a .303 to .304 bore without the benefit of a groove diameter and it was deemed fit for the Lee Enfield action and indeed, I don't have any issues with pressure with mine with pressure - not that have any means of accurately assessing pressure, just that I don't have an issue.

goodsteel, what did you do with that barrel you pulled off? Any chance of shipping it to me?8-)

[Multigunner]

AN INVESTIGATION INTO THE EFFECTS OF TIGHT THROAT AND BARREL DIMENSIONS ON MAXIMUM CHAMBER PRESSURES FOR THE 308 WINCHESTER CARTRIDGE

This investigation carried out by

THE PRESSURE TRIALS CONSORTIUM
March 1998

Chairman
Dr. Geoffrey Kolbe,
Border Barrels Ltd., Riccarton Farm, Newcastleton, Roxburghshire, TD9 0SN
Members
Mr. John Bloomfield,
National Rifle Association of Great Britain, Brookwood, Surrey, GU24 0PB

Mr. John Carmichael,
JHC Supplies, Silverthorne House, North Piddle, Worcs, WR7 4PR

Mr. Alan Gidman,
Royal Ordnance, Radway Green, Nr. Crewe, Cheshire, CW2 5PJ

Mr. Roger Hancox,
The Birmingham Gunbarrel Proof House, Banbury Street, Birmingham, B5 5RH


INTRODUCTION
The Pressure Trials Consortium was formed to address a problem that had become generally apparent to ammunition makers, firearms industry standards regulators and shooting organisations throughout the world. The problem is mainly confined to those concerned with target shooting sports, but is also one faced by all those interested in achieving the best accuracy from any given ammunition.
It has been found that to achieve good accuracy from any given ammunition, it is usually necessary to use tight throat dimensions and/or barrel dimensions, which may be tighter than the minimum specified by the bodies that regulate cartridge, chamber and barrel dimensions. (The C.I.P. Federation, though S.A.A.M.I. in the United States). Ammunition manufacturers test their ammunition in specially made test barrels which are made to the minimum dimensions permitted by the relevant regulatory body. That ammunition is then approved for use in barrels which meet the relevant dimensional standards, but using that ammunition in barrels whose dimensions are smaller than the standard permits will result in higher chamber pressures than those measured in the test barrels. The pressures could be pushed above the statutory upper limits and so be dangerous for general use.

It is well known that firearms subjected to a diet of high or over-pressured ammunition can suffer progressive stress fatigue and eventual catastrophic failure. The usual proofing requirement that the firearm should retain its integrity after firing a single overcharged cartridge cannot detect more gradual failure modes which may manifest themselves only after some hundreds or even thousands of rounds have been fired at higher than usual pressures.




DISCUSSION.
In general, the results behave as expected in that the pressure does increase as the throat and barrel dimensions decrease. The increase in pressures due to barrel dimensions alone is relatively modest - around 200 to 250 bar for each .001" that the barrel dimensions are reduced. This represents a 5% increase in pressure for a 0.3% decrease in barrel diameter. It is interesting to note the sensitivity of pressure to the throat diameter though, particularly when the throat diameter is smaller than the bullet diameter and the bullet is an interference fit into the throat.

Rest here
http://www.border-barrels.com/articles/Pressure_Trials_Consortium.htm

The practice of using undersized bores to make best use of commonly undersized European 7.62 bullets resulted in renewed warnings against use of converted No.4 rifles till they had been reproofed at the most recent CIP proof pressures for .308 ammunition.
The old undersie bullet surplus ammo was no longer available in quantity to the NRA UK so they contracted for a recent production batch that gave much higher pressure level approaching Max SAAMI limits for the .308.

The older converted No.4 rifles are limited to 3650 BAR till reproofed, and bores must pass an inspection to be sure they aren't too tight for .3085 bullets.