worn throat?

ffwd

ffwd

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Alright, I purchased a used Weatherby Mark V in 7mm Weath. mag at the Feb Gun Show in Calgary. It was the cheapest one there, and also in the best overall shape. Well as good a shape as I could tell with a visual inspection. Finally got a scope on it,(thanks CyberK!) and got it to the range last weekend. Loaded 60 more yesterday and out to the range this morning. All shot at 200m. Groups were less than stellar and I noticed that all of my casings are showing soot and burn marks around the case necks.

The guy beside me shooting a 300 win mag had nice shiny case necks on all of his spent casings.

Does this mean that my throat is worn out? Do I need a new barrel? WTF?
 
ffwd said:
I noticed that all of my casings are showing soot and burn marks around the case necks.
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It means the loads were fairly low in pressure. Sooty necks are a result of the case necks not expanding fast enough to seal off the chamber fully. With extreme low pressure the gas can actually flow back between the body of the case and the chamber wall leaving some pretty funky inward dents on the brass.
 
Please keep in mind that the Weatherby rifles were designed around a long throat. If you have room in the mag to explore seating the bullets longer, it might help with the accuracy.
 
Max COAL is listed(by hodgdon) as 3.35" with 175 gr. projectiles. The 168 gr. Berger VLDs that grouped 1.25" at 100m were at a COAL of 3.45" The factory rounds were measured at 3.38". I realize this is measured at the tip of the bullet and the distance from the ogive to the lands is more important.

This thread is also in the reloading forum. Probably more appropriate.
 
I was pretty happy with it. They grouped like the proverbial you know what at 200m though.
I'm not trying to blame the equipment, just wanted to know the cause of the soot all the way down to the shoulder.
 
If they look like this, it is normal.

P1010685.jpg
 
Well, the advice about working on the COL is good, and working the load up and down a bit might get you a little more accuracy. Wby uses a long throat, how long will depend on when the gun was made (3/4", 1/2", 3/8"). Generally, Wby rounds tend to do their best right at the upper limit of pressure. At least all the ones I own do. FWIW - dan
 
ffwd said:
All loads today were 1/2 gr.under Hodgdons max load for H4831 at 69.5 gr. with 168 gr and 160 gr projectiles
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Bear in mind also...Loading manuals are vetted by lawyers intent on keeping law suits to a minimum. You seem to have signs of low pressure. Try going up .5 gr at a time to 71gr. Stop if you have hard bolt lift. Also if you haven't tried magnum primers do. You might try a faster powder like H4350 this should build pressure faster and seal the neck to the chamber. Check the manuals for loads.

NormB
 
Why not? said:
Okay, I can tell it's an "Improved" cartridge; which one? :)

With apologies for the hijack.

Ted
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It's Lapua 6BR Brass.....right from the box the only improvement made to it was neck turning. ;)

ffwd said:
They look like that. I guess that means I just need more practice.
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The "Sine Wave" look on the neck is actually a good sign from what I have read.
 
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7mm wm loading

ffwd said:
All loads today were 1/2 gr.under Hodgdons max load for H4831 at 69.5 gr. with 168 gr and 160 gr projectiles
Click to expand...

try magnum bench rest primers, and powders that give you 95-105% case volume filling. use a collet crimping die and use a fairly heavy crimp ( be careful the double radius shoulder/neck is easily set back) With the long throat its almost impossible to seat the bullet far enough to touch the rifling and still fit the cartridges in the magazine. use the longest COL that will fit in the magazine and still provide good bullet seating depth in the case. try slower powders like 7828, rl22 and H1000

tg
 
Why not? said:
Okay, I was looking at the light line around the case below the shoulder, and figured that was the original shoulder.

What is that line from?

Ted
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Looks like the line from a Lee chamfer tool, while chamfering the outside of the mouth.
 
Why not? said:
Okay, I was looking at the light line around the case below the shoulder, and figured that was the original shoulder.

What is that line from?

Ted
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I believe it is from trimming. I use the Wilson/Sinclair trimmer which houses the case in a steel chamber. If you don't tap it in a bit, or you push too hard on the trimmer cutter, the case will turn inside the chamber and make a score marks on the case. You can see a lighter one near the bottom of the picture on the middle case.

I don't use a Lee Chamfer tool so it's not from that.

I should have ran a contest: "What caused this line on my case" :D
 
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