Necessary to trim .303 British brass?


November 23, 2008, 09:33 PM
I've been loading for the .303 for about a year now and have yet to measure or trim a case. I know the cases stretch and so far I've not had any problems. I don't load max., but some of my loads are quite warm. Am I headed for diasater by not triming my brass? This is the only caliber I load for. It's well known that the chambers of the lee enfields are oversize so I assumed I didn't need to trim.

Your comments please.

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November 23, 2008, 10:35 PM
303 brit is notorious for having excessive headspace, so the first thing you have to watch out for is long cases,, the next is case separations.
I've see them separate on the first firing, so be careful.

November 23, 2008, 10:42 PM
Check the inside of your cases with the bent paperclip method. What bolt head number do you have, and was it properly checked?

November 24, 2008, 12:12 AM
If you are full length resizing than odds are you will have to trim the brass. I trimmed all mine on the 3rd loading.

November 24, 2008, 09:56 AM
"Nessary to trim .303 British brass? "

No more so than any other case. If it's to long, trim it. Without measureing your cases you have no idea if they are getting too long. Sloppy Enfield chambers produce excess head space and diameter, not neccessary the chamber lenght. Check your brass.

November 24, 2008, 02:59 PM
I have to trim mine every 2 to 3 loadings. Like already said, check the length after shooting.

November 24, 2008, 03:03 PM
I trimmed my HP70 cases to 2.20" and I removed a lot of material. I also removed material on twice fired HP70's.

Maybe the throats in the SMLE's are a couple of feet in front of the chamber.

November 24, 2008, 03:44 PM
Brass should be trimmed after full lenght resizing or anytime they reach the maximum length for safety reasons. But most all rifles have some extra leade into the lands. This is your safty margin. If you forget to trim and the brass is a little long, your still ok. Taking measurements of the chamber, throat & leade is the only way to know how long the case can safely go. This link will help you understand chambers of bottle neck cases.

November 24, 2008, 04:09 PM
Am I headed for diasater by not triming my brass? YES.:uhoh: When the brass becomes to long, the chamber acts as a crimping device.:eek: This mean your bullet can not leave the case on firing. The pressure goes sky high and so can your gun.:o A strong action like a M70 that i saw had the bold locked shut, action riped loose from the wood stock. Lucky for the owner the action held. The owner was saving a few $$ :rolleyes: by having a friend reload some range brass pickups for him. When i measured the remaining ammo, some of the brass was way over maximum trim lenght.:(

November 24, 2008, 07:55 PM
have several "Enfields" segregate all my 303 ammo into rifle specific lots.that way I can just neck size.can go a while before trimming is needed. jwr

November 24, 2008, 09:43 PM
Even though the .303 british cartridge is listed at 2.22 inches in length, most if not all military rifles in this caliber are chambered for longer cases. Triming your brass to 2.20 inches is "correct" but my rifles shoot better with cases trimmed to individual chamber length. I have two No3Mk1* rifles with chambers of 2.35". I make cases from fireformed .30-40 brass then trim cases to chamber length -.002". With fireformed cases and using the Lee collet die, I never have to trim again. Accuracy improves, and case stretching is non-existant. I segragate my cases and designate for each rifle. I shoot mostly cast bullets and keep pressures at or below 40,000psi. A lot of case "stretch" comes form pulling expander plugs through case necks after sizing. Expecting cases to headspace on the case rim is the other source of stretching. Headspace on the case shoulder and start with new cases not once fired (one-size-fits-all) factory ammo and cases will last and not stretch all that much if at all.

Jeff F
November 24, 2008, 10:27 PM
This is the only caliber I load for.

Your a very lucky man!
I neck size only for three loadings and on the forth I bump the shoulder back a couple thousandths and trim to 2.20. I get quite a few loadings before I have to toss the brass.

November 25, 2008, 06:29 AM
Necessary to trim .303 British brass? Yes.

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