.303 Brit. Inside neck dia too small?????

wogpotter · August 29, 2011, 11:33 AM

Any bright ideas on this one?
I got a bunch of "once fired" brass & while doing the prep work discovered that many of the cases are undersized in the case neck. Some are fine the rest mic at .306" ID! So undersized that the pilot on the case trimmer (0.31")won't go in.

I even tried my .30 pilot & it is too small as well.

I don't think the cases were resized by the original owner, but as he has passed on it's hard to ask him.

PA-Joe · August 29, 2011, 01:43 PM

I wonder if he was loading 308s into the 303 cases.

res45 · August 29, 2011, 03:37 PM

It appears that whoever resized those cases used a standard .308 expander ball or rod.

Since they have already been resize I would just run them through your 303 die set and use the .311 expander then trim if needed. After that just neck size only after firing in your gun to extend case life. The 303's are known to wear out brass quickly if the cases are full length resized each time.

wogpotter · August 29, 2011, 04:30 PM

How do you know they are resized?
The neck dia is too small, but the rest of the case shows no sign of resizing!

res45 · August 29, 2011, 06:08 PM

Well for one thing if the cases are "once fired" and have never been resized the ID of the case mouth want be .306" not if fired in a 303 British it will be much larger closer to .312 -.314 maybe even larger depending on the gun they were fired in chamber dimensions can vary greatly in the 303.

Since some of your cases measure .306 then they are either new brass or somebody resized the cases using the wrong size expander ball,rod or collet,if a case is neck sized only and done correctly it want show any signs of resizing on the case body sometime it doesn't even show up on FL resized case if they don't expand much and have a tight chamber.

I never prep,use or trim brass be it new,once fired or range pickup till I run it through my own FL resizing dies that I use with my rifle,even if I'm going to neck size the case. I fire form them to my own rifles chamber first and then neck size afterward from that point on especially in the 303 .

That way I know the neck is straight and uniformly round and will accept the bullet I shoot in my rifle and that they will have the proper tension which is set when the expander pass back out through the case neck. It's at that point that I measure the case length and trim as necessary.

wogpotter · August 30, 2011, 08:26 AM

I'm certainly going to full length resize before use. I was in the process of prepping the brass for this & trying to trim all cases to the same length, that was how I discovered the narrow neck opening they wouldn't fit on the pilot in my case trimmer!
I have to trim first as I use a progressive.

August 29, 2011, 11:33 AM	#1
wogpotter Senior Member Join Date: September 27, 2004 Posts: 4,811	.303 Brit. Inside neck dia too small????? Any bright ideas on this one? I got a bunch of "once fired" brass & while doing the prep work discovered that many of the cases are undersized in the case neck. Some are fine the rest mic at .306" ID! So undersized that the pilot on the case trimmer (0.31")won't go in. I even tried my .30 pilot & it is too small as well. I don't think the cases were resized by the original owner, but as he has passed on it's hard to ask him. __________________ Allan Quatermain: “Automatic rifles. Who in God's name has automatic rifles”? Elderly Hunter: “That's dashed unsporting. Probably Belgium.”

August 29, 2011, 03:37 PM	#3
res45 Senior Member Join Date: September 15, 2007 Location: NC Posts: 753	It appears that whoever resized those cases used a standard .308 expander ball or rod. Since they have already been resize I would just run them through your 303 die set and use the .311 expander then trim if needed. After that just neck size only after firing in your gun to extend case life. The 303's are known to wear out brass quickly if the cases are full length resized each time. Last edited by res45; August 29, 2011 at 05:39 PM.

August 29, 2011, 04:30 PM	#4
wogpotter Senior Member Join Date: September 27, 2004 Posts: 4,811	How do you know they are resized? The neck dia is too small, but the rest of the case shows no sign of resizing! __________________ Allan Quatermain: “Automatic rifles. Who in God's name has automatic rifles”? Elderly Hunter: “That's dashed unsporting. Probably Belgium.”

August 30, 2011, 08:26 AM	#6
wogpotter Senior Member Join Date: September 27, 2004 Posts: 4,811	I'm certainly going to full length resize before use. I was in the process of prepping the brass for this & trying to trim all cases to the same length, that was how I discovered the narrow neck opening they wouldn't fit on the pilot in my case trimmer! I have to trim first as I use a progressive. __________________ Allan Quatermain: “Automatic rifles. Who in God's name has automatic rifles”? Elderly Hunter: “That's dashed unsporting. Probably Belgium.”

August 29, 2011, 01:43 PM	#2
PA-Joe Senior Member Join Date: June 9, 2010 Location: NEPA Posts: 909	I wonder if he was loading 308s into the 303 cases.

August 29, 2011, 06:08 PM	#5
res45 Senior Member Join Date: September 15, 2007 Location: NC Posts: 753	Well for one thing if the cases are "once fired" and have never been resized the ID of the case mouth want be .306" not if fired in a 303 British it will be much larger closer to .312 -.314 maybe even larger depending on the gun they were fired in chamber dimensions can vary greatly in the 303. Since some of your cases measure .306 then they are either new brass or somebody resized the cases using the wrong size expander ball,rod or collet,if a case is neck sized only and done correctly it want show any signs of resizing on the case body sometime it doesn't even show up on FL resized case if they don't expand much and have a tight chamber. I never prep,use or trim brass be it new,once fired or range pickup till I run it through my own FL resizing dies that I use with my rifle,even if I'm going to neck size the case. I fire form them to my own rifles chamber first and then neck size afterward from that point on especially in the 303 . That way I know the neck is straight and uniformly round and will accept the bullet I shoot in my rifle and that they will have the proper tension which is set when the expander pass back out through the case neck. It's at that point that I measure the case length and trim as necessary.