Brit 303 /4 with 03a3 barrel in 303 brit

[HighHook]

I just purchased a $50 sporterized brit 303 /4 with looks to be a 03a3 barrel that chambers a 303 brit and has a .308 size barrel. :roll:

The person i bought this from has no idea of the previous owner.

Has any body ever seen this before?

I slugged the barrel and it slugs at .304 outside and .308 with the rifling.


My thoughts are load a 165 gc sil rcbs sized at .309 with 16grs of 2400 and see how it shoots. :castmine:

Thoughts? :coffee:

[zuke]

You just got VERY lucky!
You can use any 30 cal bullet in that barrel instead of the limited number of 312/314 available for the .303's.
All you need to do is polish your expander ball down to .307/.308

[junkbug]

I have never seen one with my own eyes, but C.E Harris wrote of having such a conversion made for the very reason Zuke mentioned. And also, 20 to 30 years ago, it was much harder to get a good mold for an oversized Enfield barrel. Problem solved.

[curator]

Be advised that many No4Mk1 rifles were converted to 7.62 Nato or .308 Winchester. I'm not sure that you can't chamber a .303 British cartridge in a 7.62X51 chamber. Make and mneasure a chamber cast before trying to shoot it.

[Mk VII]

What makes you think it's an 03A3 barrel?

[Stoats]

Be advised that many No4Mk1 rifles were converted to 7.62 Nato or .308 Winchester. I'm not sure that you can't chamber a .303 British cartridge in a 7.62X51 chamber. Make and mneasure a chamber cast before trying to shoot it.

You can't.

[Multigunner]

You can't.

You shouldn't be able to if the chambering was properly done, The .303 case in 56 mm long while the .308 is 51mm long.
If the barrel is a Springfield barrel turned and cut at the breech to fit a No.4 then the rechambering might have left part of the original .30-06 neck and shoulder untouched. With a barrel and chambering job of unknown provenance a chamber cast would be a good precaution.

Theres also the possibility of the rifle being chambered for a unknown sporting cartridge or wildcat.
Some Turkish capture SMLE rifles were rechambered to 8mm Mauser, so just about anything is possible.


One drawback to using a .308 bore and the .303 chamber is that despite the claims of some a bullet .003 larger than bore diameter has been shown to increase chamber pressure by about 8%.
An early experiment with the No.1 Ruger custom made with .308 bore, apparently for the purpose of evaluation of .308 bullet styles at .303 velocities, was said to have shown an increase in chamber pressure of over 3,000 psi when standard .303 cartridges were used.

The Birmingham Proof Authority published a study on .308 match rifle barrels awhile back that confirms the general principle. Some .308 Winchester match grade barrels sold in England having bores as tight as .306 to compensate for undersized British and German 7.62 NATO bullets.

Krag barrels used to manufacture the Bannerman .303 Drill rifles supplied to England during WW1 were said to have proven to be extremely accurate due to the bore size being around .310.
Unfortunately those rifles were condemned as unsafe and ordered destroyed, but a few survived and are in collections.
The rifle used condemned 1901 Springfield prototype receivers and may not have been properly heat treated, also the magazine modifications did not work well so they didn't feed the rimmed .303 well if at all.

Some Wartime .303 ammo has been found to have bullets as small as .309 but other lots can measure .312 which was the maximum limits for acceptance.
Reynolds wrote of accuracy testing which determined that best accuracy was obtained when the bore was at minimum acceptable limit of .313 and the bullet was at the max of .312. Commercial nominal bore size of the .303 is .311, but very few Enfields can be found with a true .311 bore.

[junkbug]

Surplus Springfield barrels are not hard to identify on sporters once you get used to seeing them. I have seen them fitted to custom 98Mauser sporter rigs.

The pressure Multigunner mentions is usually dealt with by enlarging the throat some, and increasing the lead a little. But that defeats the whole purpose of an accuracy specialized rifle.

I believe some built these on the assumption that they would be chambered just loose enough that if a surplus or factory .303 British carrtridge was fired, it would not spllit a case or pop a primer, but the real purpose of the rig was to shoot it with much more available .308" jacketed bullets or cast bullets that did not have to be cast much larger than .311" to .312" to give max accuracy.


Kind of a specialized compromise. Have fun, enjoy, and be safe.

A chamber cast is a good idea, too.

[Char-Gar]

You probably have a fine cast bullet rifle. Your issue will be the size of the neck, of the fired case. You don't want to squeeze the neck down to hold a .309 bullets and that will give you some bullet alignment issues. You want to use a bullet size that will allow the case neck to fill the chamber with just enough room to allow for case expansion as the bullet goes on it's way.

Even if you trust the fired case body to hold the round tight in the chamber, you will have short case life due to the excessive sizing of the case necks. Lot of splits if you don't anneal often.

For this reason, you may well have to use larger bullets to get top accuracy.

You don't have to worry about the bullet being oversize for the bore and they squeeze down quite nicely in the barrel. At the pressure we run at for cast bullets, it should not be an issue.

[303Guy]

Well, the two-groove 303 Brit has to size most of the bullet down to around .304 from .311 with no pressure issues.

http://i388.photobucket.com/albums/oo327/303Guy/MVC-201F-1.jpg

[Multigunner]

Well, the two-groove 303 Brit has to size most of the bullet down to around .304 from .311 with no pressure issues.



Land to land the two grooves run about .304, but the bullet material is swaged into the very deep grooves that usually run over .314 Major dia, with .316 or larger being fairly common.
If the bullet mass had no where to go then you could see some serious uptick in pressures.

[Bob Krack]

I just purchased a $50 sporterized brit 303 /4 with looks to be a 03a3 barrel that chambers a 303 brit and has a .308 size barrel. :roll:

The person i bought this from has no idea of the previous owner.

Has any body ever seen this before?

I slugged the barrel and it slugs at .304 outside and .308 with the rifling.


My thoughts are load a 165 gc sil rcbs sized at .309 with 16grs of 2400 and see how it shoots. :castmine:

Thoughts? :coffee:I probably don't know what I am talking about but if'n it were me, I would start at 12 - 14 grains of 2400 (if that is your powder).

I have no fear of shooting a cast boolit at 5 or 6 thousandths oversize and even at near max loads. but your machine is an unknown.

Play it safe and start low and work up to a load that shows either max accuracy or pressure signs. We're here to help ya.

Bob

[303Guy]

with .316 or larger being fairly common.
If the bullet mass had no where to go then you could see some serious uptick in pressures. My rifle's grooves measure at .318 with a digital caliper. I wouldn't be at all surprised it my rifle is developing higher pressure because of all that swaging but then it is a No.4 which I believe can take it. However, I am hand loading to what appears to me to be a comfortable Lee Enfield pressure. (I've determined that it's bullets/boolits that kill and not velocity and besides, my rifle kills better than a high velocity 308! Meaning dead without blowing up the critter!)

[Multigunner]

They ran tests on bullet friction and barrel heating of machine guns using a hydralic ram to push bullets through a rifled barrel so heat of the propellent would not be a factor.

If the equipment were available a similar test to determine the force in PSI necessary start the bullet into the origin of rifling.

[303Guy]

With a hydraulic system there is no suddenly applied load factor. Shock load you might say. It's what pile drivers use to drive down piles. Without a little bullet jump, the pressure rises quite a bit. No idea how much though. Still, static load to drive a bullet into the bore is as good a starting point as any. It would be interesting to learn just what was found and to compare different modes of driving the bullet. Cast boolits would behave quite differently no doubt.