Seating depth

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All handloading data posted on Full-Bore UK from 23/2/2021 must reference the published pressure tested data it was sourced from, posts without such verification will be removed.
Any existing data without such a reference should treated as suspect and not used.

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Forum rules
All handloading data posted on Full-Bore UK from 23/2/2021 must reference the published pressure tested data it was sourced from, posts without such verification will be removed.
Any existing data without such a reference should be treated as suspect and not used.

Use reloading information posted here at your own risk. This forum (http://www.full-bore.co.uk) is not responsible for any property damage or personal injury as a consequence of using reloading data posted here, the information is individual members findings and observations only. Always verify the load data and be absolutely sure your firearm can handle the load, especially older ones. If in doubt start low and work your way up.
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simong
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Seating depth

#1 Post by simong »

Evening chaps,
This may be a bit of a bone question but.....am I correct in thinking that there is a direct relationship between seating depth and pressure ? (i.e.: seat deeper = increased pressure). If so then any guesses as to a rough percentage increase for 0.02" would be using a 308 case ?
I understand that any advice, comments, mickey taking finger waggles ect... are acted on at my own discretion. fingers crossed

Thanxs in advance

Simong
Suffolk champion...50 mtr precision flinching champion


Howa 308 GRS stock
Uberti 1873 45 LC
Ruger Precision 6.5
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ovenpaa
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Re: Seating depth

#2 Post by ovenpaa »

Do you know how far you are jumping the bullet at the moment? If you are still .015" -.0012" off the lands then I would not be unduly concerned however if you are .002" of the lands and running a very hot load....

Some more information would be handy, bullet weight, powder type and load, primer etc.
/d

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simong
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Re: Seating depth

#3 Post by simong »

Hi Ovenpaa,

Rifle is a howa 1500, case ruag, powder N140, fast shiny things are sierra 155 palma match and primers cc1 200.
I don't think i am anywhere near ( relatively) the lands, but not sure.
All I'm after is something fairly accurate out to a max of 600 ( the rifle is a bit of an self indulgent plinkster, although a bit special :0037: )
Any pointers gratefull recived sign85

simong
Suffolk champion...50 mtr precision flinching champion


Howa 308 GRS stock
Uberti 1873 45 LC
Ruger Precision 6.5
User avatar
ovenpaa
Posts: 24689
Joined: Fri Nov 05, 2010 8:27 pm
Location: Årbjerg, Morsø DK
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Re: Seating depth

#4 Post by ovenpaa »

How much powder and what is your OAL?
/d

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simong
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Re: Seating depth

#5 Post by simong »

Hi Ovenpaa,
Sorry about the delay in coming back but the connection here I am is a bit iffy :cool2:
At present I am using 42 gr n140 and the oal is 2.795

The sierra book list 43.1 and 2.775 as an "accuracy load" and I was thinking about working up to this...

simong
Suffolk champion...50 mtr precision flinching champion


Howa 308 GRS stock
Uberti 1873 45 LC
Ruger Precision 6.5
User avatar
ovenpaa
Posts: 24689
Joined: Fri Nov 05, 2010 8:27 pm
Location: Årbjerg, Morsø DK
Contact:

Re: Seating depth

#6 Post by ovenpaa »

I would say you were perfectly safe to advance .002" with that load and OAL however why just the .002"? Your next step has to be to check your maximum OAL for your chamber, once you have that figure you know exactly how much you can safely increase the OAL by.

An OAL gauge is handy at this stage however you can improvise. A case with a couple of lengthways slits hacksawed in the neck to allow the bullet to be gripped but slide under pressure is one way. Chamber the test bullet carefully and open the bolt with a hand in the way to catch the bullet as it comes out. Measure and repeat five times, this should give you an average OAL.

My first ever OAL gauge was improvised by drilling a hole in the back of the case, soldering some copper tube in and then using a piece of wire coat hanger with a kink in it to act as a pusher and friction stop, it worked well and gave me the results I needed.

Or you can buy a dedicated OAL gauge.
/d

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