80.5gn FB Berger seating depth???

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DenisA
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Joined: Wed Nov 09, 2011 7:00 pm
Location: Sunshine Coast, QLD

80.5gn FB Berger seating depth???

#1 Postby DenisA » Wed Jul 31, 2019 11:17 pm

G’day All,
I’m about to do initial load tests on a new .223rem using 80.5gn FB bullets. 30” straight profile, 1:7T throated looooong. I expect to find a load around 25gn ar2208.
I’d love to get a general idea of what seating depth everyone is running these bullets at. I have a lot of experience with 155.5 FB in .308 which love to be run at .010” jump in many and varied combinations. Therefore I plan to run my powder charge tests on this .223 at .010” jump unless the general concensus suggests something else. I’d really appreciate your help. Thanks, Denis.

Barossa_222
Posts: 187
Joined: Sat Feb 08, 2014 6:58 pm
Location: Barossa Valley

Re: 80.5gn FB Berger seating depth???

#2 Postby Barossa_222 » Thu Aug 01, 2019 8:33 am

I was always told to start my testing jammed.

DenisA
Posts: 1457
Joined: Wed Nov 09, 2011 7:00 pm
Location: Sunshine Coast, QLD

Re: 80.5gn FB Berger seating depth???

#3 Postby DenisA » Thu Aug 01, 2019 9:10 am

Barossa_222 wrote:I was always told to start my testing jammed.


This is true when fireforming

KHGS
Posts: 709
Joined: Thu Oct 20, 2005 12:46 am
Location: Cowra NSW
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Re: 80.5gn FB Berger seating depth???

#4 Postby KHGS » Thu Aug 01, 2019 9:20 am

DenisA wrote:
Barossa_222 wrote:I was always told to start my testing jammed.


This is true when fireforming


Seating depth is always barrel related. I start with .015" jam, develop the most accurate powder charge with the bullet jammed then fine tune the seating depth. Doing it this way there is only one direction to tune seating depth. A little trivia for you, I shoot all target loads jammed and all of my bullets are mollied.
Keith H.

DenisA
Posts: 1457
Joined: Wed Nov 09, 2011 7:00 pm
Location: Sunshine Coast, QLD

Re: 80.5gn FB Berger seating depth???

#5 Postby DenisA » Thu Aug 01, 2019 9:37 am

KHGS wrote:
DenisA wrote:
Barossa_222 wrote:I was always told to start my testing jammed.


This is true when fireforming


Seating depth is always barrel related. I start with .015" jam, develop the most accurate powder charge with the bullet jammed then fine tune the seating depth. Doing it this way there is only one direction to tune seating depth. A little trivia for you, I shoot all target loads jammed and all of my bullets are mollied.
Keith H.


I use to shoot them all jammed because I believe in the the theory of it. The way I shoot now is that I often unchamber rounds while waiting for conditions. Don’t want them getting hot. With a jammed load and secant bullet it’s no problems, never had an issue with VLDs but with some of the tangent bullet and hybrid types I’ve had bullets stay in the lands. So my theory now is jumped loads for tangent type bullets, especially with light neck tensions that I use.

I like your point about only having one way to go when you start jammed.

Peterla
Posts: 246
Joined: Tue Dec 14, 2010 10:49 am
Location: Barossa Sth Australia

Re: 80.5gn FB Berger seating depth???

#6 Postby Peterla » Thu Aug 01, 2019 11:54 am

I do it slightly different.
I load 2 ladder tests 1 jammed 10 th and 1 jmped 10 th
Then shoot these at 1000 yards as ususal watching for pressure and hard bolt lift.

I can then see quite easy what the barrel likes. I have 2 SAUMs that love jump and 2 that love Jam all with 180 hybrids

Just what I do that seems to work for me.

Southern700
Posts: 15
Joined: Mon Jul 21, 2014 6:24 pm
Location: Tasmania

Re: 80.5gn FB Berger seating depth???

#7 Postby Southern700 » Sun Aug 04, 2019 12:50 pm

I'll have to check, but I'm pretty sure I jump around 0.024" (been a while since I checked erosion) - my chambers are a bit long for jamming with adequate seating depth. I will say though, 108s (6BRX) & 155.5 (308) seem to like a 4-10 thou jam. I've always stayed away from the dreaded "touching the lands" CBTO length...

Jason72
Posts: 6
Joined: Sat Feb 10, 2018 5:23 pm

Re: 80.5gn FB Berger seating depth???

#8 Postby Jason72 » Mon Aug 05, 2019 8:12 am

Hi Denis,

From my experience which is limited compared to many, every barrel/rifle will respond differently when it comes to determining the best jump/jam (lots of resasons for this starting with the gunsmithing, casing type, right through to the type of material used to manufacture the barrel) so the best way is to take the time and try a few different set ups with the same powder load at the same time under the same conditions on your set up.

I have found that you can find out the best grouping at a shorter distance (this is subjective, some say 100m, some say 140m after the projectile stabilises etc) however the point is, for checking what jump/jam gives you the best grouping, a longer distance has more variables such as wind, mirage and most importantly the nut behind the butt. If you can reduce the variable you will get better data.

Just on jump verse jam, I have found that if you run a light neck tension such as 1 or 2 thou you cannot have jam. The reason for this is no matter how far you leave the projectile out of the casing, as soon as you close the bolt the projectile will move back the the maximum OAL no matter the jump, the casing is the weakest point rather than the hardened steel of a barrel so it will move back into the casing.
Try it, measure the OAL of a long load, load the rifle and close the bolt then remove the load and measure it again.

Hope this helps somewhat.
Cheers
Jason


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