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reloading, case length.

19 Nov 2013
@ 08:32 pm (GMT)

jason brown

i thought id share something iv been looking into.

first im not an expert by any means, and figures quoted are just my experience, with my rifle. they may be very dangerous in your rifle. do your own measuring for your rifle.

so i brought this up a while ago but i cant find the thread. it was about case length and to be exact case neck length. i was wondering if there was anyone measuring there "true" case neck length for "there" rifle.
im not sure if there is a lot of benefit or if it was even worth the effort. but i figured more case neck length might mean being able to seat a bit further out if seating for contricity. and the obvious less case trimming.

well it turned out it wasn't a hard or expensive exercise. but as far as worth while well that's up to the reader.
i got these plugs from sinclairs when ordering a few things.
there called "Sinclair chamber length space gauges"

you basicly trim a case back real short, put the plug in and close the bolt on the now modified case which comes out maximum length.

my results were...
over all length was 2.5475 inches which is for my 7mm magnum
the standard book trim length is 2.5 inches.
they recommend that if you do leave your case length to grow, to set the over all length .024 less than the actual over all length of your chamber.
(the reason being explosive if you don't, as far as i understand)
so that leaves me with 2.5230 i can stretch it out to.
.023 inches over the book trim to length.

as a novice i always used to trim to about 2.4990 to make sure im under the trim length. its good to know i can let the cases grow some what or that i have a bigger margin than i thought. so far i havnt let the cases grow there sitting right on 2.5 but i plan to.

so yeah, that's my novice experience with chamber length gauges.


Replies

19 Nov 2013
@ 08:48 pm (GMT)

Nathan Foster

Re: reloading, case length.
That was a fantastic find. Thanks for sharing Jason.
19 Nov 2013
@ 09:50 pm (GMT)

jason brown

Re: reloading, case length.
hey Nathan. do you know if the .024 inches trimmed back from the actual length of the chamber sounds like a safe number? its what they recommend. but knowing that case length is an important safety issue, theres no harm in getting a second opinion is there.... (not that I would push every last thou out of the case, I would give it a bit more room for error to be on the safe side)

and what is the issue, is it that if the case grows while being fired if it hits the end of the chamber it creates pressure, or something needs to give under the growth, which could be the bolt?
can you give any in-sight?

thanks, looking forward to the reloading book, no pressure, ha ha.
20 Nov 2013
@ 02:07 am (GMT)

Nathan Foster

Re: reloading, case length.
If the case neck is too long, you will basically crimpt the bullet in place when chambering. The chamber mouth tries to trap the bullet- that is why it is so dangerous and can jack pressures right up.

.024" is fine. That gives you plenty of leeway.
20 Nov 2013
@ 02:58 am (GMT)

Trevor Wilkes

Re: reloading, case length.
Hi Guys,
Just so happens I just received my gauges as well as im getting a couple of new rifles built,just be aware that if you have a custom chamber that requires neck turning they may not fit in your throat.
I actually use to use flatbase projectiles put in the case backtofront for the same result.
But im a sucker for gadets like many i guess.

cheers Trevor
20 Nov 2013
@ 03:14 am (GMT)

jason brown

Re: reloading, case length.
thanks Nathan, I understand what your saying and that inspires confidents.

cool trevor, I would be interested to hear how much over standard your chamber measures. mine is a standard sendero rife. I have the gauge for my .223 as well but I havnt got too far into that just yet.
20 Nov 2013
@ 06:43 am (GMT)

Trevor Wilkes

Re: reloading, case length.
Hi Jason,
I will check them tomorrow and let you know, I have read elsewhere that some people trim brass within 10 thou of their chamber length not somthing I would do myself.
My mate had a 6mm target rifle built with a tight neck chamber and his gage wouldnt fit then he discoverd they actualy have tight nk 6mm gauges thats why I mentioned about gauges not fitting in some custom chambers.

cheers trevor.
20 Nov 2013
@ 11:18 pm (GMT)

Trevor Wilkes

Re: reloading, case length.
Here you go Jason,
Sako A7 22-250
Case trim length-1.902
Max case length-1.912
Actual chamber length-1.943.5

Tikka t3 270win
Case trim length-2.530
Max case length-2.540
Actual chamber length-2.578

Rem 5r 308win
Case trim length-2.005
Max case length-2.010
Actual chamber length-2.056.5

Rem sendero 300 ultramag
Case trim length-2.840
Max case length-2.850
Actual chamber length-2.886

Cheers Trevor
21 Nov 2013
@ 04:44 am (GMT)

jason brown

Re: reloading, case length.
thanks trevor.
just interesting. it seems to make mine fairly standard compared to yours.
 

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