Problem cambering round - 300WM

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Problem cambering round - 300WM

Post by Diddums » 16 Apr 2019, 2:54 pm

I've come across a strange situation with a hand loaded 300WM round.

I had new Winchester brass which was FL resized and all other necessary case prep done. They were loaded with 168g Z-Max to a few thou off the lands and i was loading for a ladder test.
I went to chamber one of the rounds and the bolt wouldn't close unless i really forced it, so i didn't fire that round (of course).
I figured that maybe i may have missed a case when sizing and maybe the head space was too long or didn't seat the bullet properly.

When i measured it against a fired case the head space on the unfired round was less than the fired case so that couldn't be the issue.
I then measured the COAL from the ogive against a round that would chamber and the COAL was exactly the same.

This is my first magnum calibre so don't have any experience with belted magnums, but can anyone shed some light on what might be the issue.
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Re: Problem cambering round - 300WM

Post by grandadbushy » 16 Apr 2019, 4:01 pm

G'day Diddums i haven't got a 300 but i have a 7mm mag its a belted case same as the 300 also mate have you loaded for that rifle before ?
Is it a new rifle and have you fired from it before i have found some brass have a different depth belt so check that and what is the type of brass if you have fired any
it does sound that the bullet is too long but it is possible other things could cause that .If you haven't fired that rifle and its new check the set holding down screws on the scope it is possible that they are protruding through and touching the bolt see if the bolt has marks on it test the actual brass length compared to spec length if the projectiles were hard to press into the brass when loading there is a chance you may have bulged the brass check the whole shell of the bullet that wouldn't go in full length for width check the projectile around the ogive for any marks if there is any it's possible its hitting the lands belted brass can eventually get a bulge down near the bottom end close to the belt from repeated pressure but if yours is new it won't have that also check up inside the chamber area for abnormalities or a piece of debris left behind from previous firings if it is just the change of brass then it could be just the wider belt although not only that others on here may have more info but that is some of the things i have collected since i've had a belted case cheers mate hope this will help
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Re: Problem cambering round - 300WM

Post by duncan61 » 16 Apr 2019, 5:17 pm

I am sure belted magnums headspace on the belt.To full size a case back to spec takes a lot of force and special attention to lube.After I resize my 7mm Rem Mag cases I feed them into the chamber of my Sendero and close the bolt on every one.You may need to screw your resizing die in some more to suit your rifle
.22 winchester .22hornet .222 .243 7mm rem mag cbc 12g
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Re: Problem cambering round - 300WM

Post by Diddums » 16 Apr 2019, 7:41 pm

I had already fired about 50 rounds through the rifle before I came to this round and all the others I fired after chambered fine.

I'll look into if the belt is in the wrong spot.
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Re: Problem cambering round - 300WM

Post by SCJ429 » 16 Apr 2019, 7:48 pm

Will the case chamber after you remove the pill? Did you trim the cases before reloading?

My bet is the ogive length is a bit longer for that projectile and it is engaging the lands. The pill you used to measure COAL may have had a couple of thou shorter ogive length.
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Re: Problem cambering round - 300WM

Post by TassieTiger » 16 Apr 2019, 9:57 pm

I had same issue with my new 06.
I had my FL die just touching the cartridge holder - and this wasn’t quite enough to 100% fl the case in a tight chamber.
I screwed down the die another full turn and bingo - chambered like glass. Took a while to work it out.
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Re: Problem cambering round - 300WM

Post by duncan61 » 17 Apr 2019, 1:35 am

Same deal I keep resizing till they chamber easy
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Re: Problem cambering round - 300WM

Post by eddahenry » 19 Apr 2019, 10:50 am

I do alot of 300WM and have seen belt bulge (this is the problem you are having im betting ) on rounds only fired twice it all depends on the brass and how hot you load them.
the problem happens because no die can size down all the way to the belt it actually flows brass towards the belt putting a bulge just in front of it.
ANd as the WM head spaces on the belt if it has the bulge in front of it it just wont camber easy
the only way to fix this is with this die made just for the job i use it on all twice fired brass to save issues
Belted Magnum Collet Resizing Die
http://www.larrywillis.com/
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Re: Problem cambering round - 300WM

Post by marksman » 19 Apr 2019, 2:01 pm

eddahenry wrote:I do alot of 300WM and have seen belt bulge (this is the problem you are having im betting ) on rounds only fired twice it all depends on the brass and how hot you load them.
the problem happens because no die can size down all the way to the belt it actually flows brass towards the belt putting a bulge just in front of it.
ANd as the WM head spaces on the belt if it has the bulge in front of it it just wont camber easy
the only way to fix this is with this die made just for the job i use it on all twice fired brass to save issues
Belted Magnum Collet Resizing Die
http://www.larrywillis.com/


that is an interesting site :thumbsup:
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Re: Problem cambering round - 300WM

Post by duncan61 » 19 Apr 2019, 2:20 pm

7mm.jpg
7mm.jpg (218.54 KiB) Viewed 240 times
:D This topic has been good as I have just cycled all my loaded Target rounds and I have 20 to be loaded that all cycled good
.22 winchester .22hornet .222 .243 7mm rem mag cbc 12g
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Re: Problem cambering round - 300WM

Post by Diddums » 19 Apr 2019, 6:37 pm

eddahenry wrote:I do alot of 300WM and have seen belt bulge (this is the problem you are having im betting ) on rounds only fired twice it all depends on the brass and how hot you load them.
the problem happens because no die can size down all the way to the belt it actually flows brass towards the belt putting a bulge just in front of it.
ANd as the WM head spaces on the belt if it has the bulge in front of it it just wont camber easy
the only way to fix this is with this die made just for the job i use it on all twice fired brass to save issues
Belted Magnum Collet Resizing Die
http://www.larrywillis.com/


I've seen a video that used that die and will probably look at getting one in the future.
In saying that though, this case in particular hasnt been fired yet and is a brand new case.
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Re: Problem cambering round - 300WM

Post by grandadbushy » 19 Apr 2019, 9:42 pm

Diddums it could be just one of those cases that you get at times where the diamentions are all over the place just keep going and test everything and leave not stone unturned you've recieved some good advice from these people even though it's very hard to solve a problem without seeing the rifle and ammo but if it's jamming it's got to be leaving a mark or dent in the brass or projectile just keep at it mate and best of luck
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