I need some schooling...

Nooch13

Nooch13

In Hoc Signo Vinces
Full Member
Minuteman
Feb 16, 2017
584
131
Ocala, FL
#1
So I'm a new reloader who THOUGHT he had things down. Obviously not...

so i loaded up some brand new .300 win mag Hornady brass with h4831 and 240gr SMK's. The case length is 2.615 out of the box (might be the first issue, my Sierra book calls for 2.610). I ran them through a full sizing die and loaded (with loads from 69-71.5gr) to a COAL of 3.6". They will not chamber in my rifle.

I double checked the rifle and it will chamber some factor rounds I have laying around. Any suggestion? Could it be those couple of thousands of an inch in case length? I wouldn't think I'd need to trim new Hornady brass out of the box?

Id appreciate any help or advice anyone could give...
 
#2
You need to get a headspace gauge and see if you are bumping the shoulders back.
If you are not, then you are actually stretching the case.
 
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#4
I don't have any experience with 300 win mag, but what I'm seeing in a couple of different loading manuals is that the COAL for 300 win mag is something like 3.340." At 3.600" you might be well into the lands of the barrel. Your Sierra book is stating the trim to case length I believe, so I don't see why being .005" over trim length would keep anything from chambering. Maybe someone with experience with the cartridge will chime in later, but if I were you I would start with checking to see if my bullets are jamming into the lands when trying to close the bolt.
 
#5
Ok, so yes, the empty cases will chamber and eject perfectly...what do you suggest I adjust the overall COAL to? I went by the Sierra book which calls for 3.6.

thanks for the replies guys
 
#6
Another note to any other rookies of any caliber...don't load 50 rounds before you check if your round will chamber...I hope someone learns from my mistake!
 
#7
And considering I am not sure at all on bullet seating depth, would I be smart to load a dummy round with no powder or primer so if I get it stuck, I can whack it out without fear of it going off?
 
#8
Ok so we've pretty much determined your COAL is way to long. So next step for me would be to find the exact length of the loaded round to the lands. Find that measurement(Hornady and Sinclair make great bullet seating depth tools), subtract a few thousandths so you are not jamming but yet don't have too much jump either. The first thing to contact the lands on your cartidge is the bullet's OGIVE. So get a comparator tool to measure your cartridges lenght to the OGIVE as this is more repeatable measurement because it is much more consistant bullet to bullet than the tip. Hope I helped.

 
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#14
Nooch13 said:
Thanks! I will try that! You guys are awesome...
Click to expand...

Not a problem. This isnt as easy with some actions so I hope it is on yours. If you have a remington style bolt it should be easy to get the ejector out, just a simple roll pin to punch out, dont let the ejector and spring go flying across the room. With this method you can find the exact point where the bullet engages the lands down to the .001" and its repeatable. From there by using your bullet comparator gauges on a set of calipers you can determine exactly how far you are from the lands confidently.
 
#15
Don't disassemble the bolt. Just seat deeper in .005" increments until your rounds chamber. Then back off another .050" from that point so you get a little jump and your pressures don't spike. You're loading a real heavy bullet with a fast burning powder. This is not a combo you want to jam into the lands.
 
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