Is it best to use a bullet with cannellure when loading a 300 Win Mag? I know factory ammo has one, but I didn't know if it is absolutely needed.

If you are roll crimping a bullet, yes you need a cannellure. You can only roll crimp a bullet if the bullet has a cannellure. If you are not roll crimping a bullet a cannellure is not needed. If you have a bullet with a cannellure, you don't have to crimp it. I don't crimp any of my loads for my bolt action rifles. Good luck.

The .300 Win. Mag. has a short neck. When it was first introduced, this feature was critisized, and some pundits insisted that all bullets used in it had to be crimped because of this. Nosler even went so far as to produce a special series of partition bullets just for it that had a series of small relief grooves on the shank instead of the one relief groove of the previous bullets (this was in the days when the Nosler Partition was made on automatic screw machines). It has since developed that the .300 Win. Mag. neck works just fine, and no special treatment is really needed. This cartridge's neck is no worse than the .300 Savage or the 7.65X53 Argentine Mauser, for example.

Keep yore powder dry!!

Thanks guys! This will ease my mind since the factory ammo has a cannellure I wasn't sure. I read something that said the 300 win mag needed a cannellure, but it was an old publication on reloading (1960's). New manuals say nothing about it so I haven't been using bullets without a cannellure. I just wanted to make sure.

Do I need to do anything special to factory brass that came with a cannellured bullet if I am using bullets without a cannellure. I just have been resizing and going with them as is. I trim them if needed.

I size them, trim them, chamfer them, and load as usual. Good luck.

I used to not believe in crimping with the cannelure bullets like grandslams and A-Frames in my 300Mag, but one day for grins, I did, and my groups improved considerably. Now the brass I was using was shot 3 to 4 times, and I could have just needed the Neck tension, but sometimes crimping a cannelure bullet will surprise you.

Like bigcountry said, sometimes crimping may improve accuracy, sometimes not. This is an idividual thing, which varies from gun to gun, and maybe even depending upon bullet or powder type in the same gun. If crimping, just be sure not to buckle case necks. This means the crimping groove must be deep enough, and in exactly the right spot in relation to your case mouth before the crimp is applied.

Keep yore powder dry!!

So, since I am pretty new at reloading, should I not crimp? It sounds as if it is a little tricky to me. On the other hand if I ever do crimp I have to start sometime.

I think I will start by not crimping and see how my groups are. What type on group should I expect at 100 yards with a 300 win mag? I am a pretty good shooter, and I know it depends on who is behind the trigger, but what should the gun realisticly be able to do?

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my 2 cents worth....ok? crimping a bullet is necessary for a tubular magazine or a revolver or ACP.......anything else (including a .375 H&H ) is not necessary.

Don't get carried away with crimping a bolt action cartridge.....it's simple not necessary.

The cannelure does help keep the jacket and lead core together however and I like cannelured bullets for that reason>