How much jump for your 123 SST loads?

[Whit]

Tried looking for this, and found a few interesting and informative threads, but not specifically what I was looking for. Forgive me if it's already been beaten to death here, I just couldn't find it.

Looking to see if someone has found the "magic" amount of jump for the 123 gr SST- if such a thing exists. Is it the normal .015-.03?

Barrel is a 16" AA. I'm about to work up some 123gr SST loads, and have never loaded these before. In order to figure out where it touches the lands, I loaded a too-long dummy cartridge with one of these bullets, and continued to seat the bullet deeper until the bolt lugs finally engaged. COL for the dummy that just allows the bolt to go into battery is 2.280". The longest COL that will work in my mags without issue seem to be about 2.266". Just trying to find the perfect seating depth, or at least a good place to start.

[Texkitch]

All barrels are different, but my 16” AA shoots the 123 SSTs best when seated about 10 mils off the lands. Hornady brass, CCI450 and work up to 28.0 gns ARComp. When did you purchase the barrel? My chamber is quite a bit shorter as the 123 SST hits the lands at 2.230”. I should probably ream it but I’ve learned to load for it and I’m happy with my results.

[Whit]

It's a new barrel. Maybe I need to seat a bullet against the lands and measure it with a cleaning rod just to verify. That's quite a bit of difference.

[Whit]

Just measured using the cleaning rod method and got exactly the same reading, 2.280".

[Texkitch]

That’s good. You’ll be able to shoot factory without issues if needed. Several of us got some with “compact” throats. I got mine in early 2017. Some sent theirs back and AA reamed them. Glad they’re reaming a bit deeper now. So if you go mag length you’ll be about 15 mils off. Should be good, I think they do like a little jump.

[grayfox]

Just got back from a session at the range for my 16er (Faxon), shooting both factories, the Custom 123sst and the Eld Black... anyway for my hand loads I haven't looked for the jump, I do a coal of 2.245. The SST in particular seems to like more jump rather than less, kind of an anti-Berger...
2.240-2.245 is working best for me in all my barrels.
The factory loads tonight were inside of 1/2" (3@ 0.486") at 100 yds if the shooter can do his part. Both are averaging ~2430 with sd of 12-13. Not bad for average barrel and factory ammo.

Think I'll be taking them along as hunting rounds this fall.

[Whit]

The SST in particular seems to like more jump rather than less, kind of an anti-Berger...

Thanks. That's the kind of information I was looking for.

[Cornbread]

Tried looking for this, and found a few interesting and informative threads, but not specifically what I was looking for. Forgive me if it's already been beaten to death here, I just couldn't find it.

Looking to see if someone has found the "magic" amount of jump for the 123 gr SST- if such a thing exists. Is it the normal .015-.03?

Barrel is a 16" AA. I'm about to work up some 123gr SST loads, and have never loaded these before. In order to figure out where it touches the lands, I loaded a too-long dummy cartridge with one of these bullets, and continued to seat the bullet deeper until the bolt lugs finally engaged. COL for the dummy that just allows the bolt to go into battery is 2.280". The longest COL that will work in my mags without issue seem to be about 2.266". Just trying to find the perfect seating depth, or at least a good place to start.

What mags are you using? I want to say my ASC mags wiil go 2.290".

[Whit]

What mags are you using? I want to say my ASC mags wiil go 2.290".

E-Landers. 2.266" is the longest COL I've been loading to with those mags. I might could go a smidge longer, but those are almost touching the front of the mag.

[CaptnC]

I've seen this thread for a while and just read it tonight...I was thinking the OP must have been using a bolt gun.

Mag length is about as long as a guy can get so I was wondering why a discussion among gas guys...I missed it that some guys have short throated rifles.

Good to know if I do another Grendel!