Neck Measuements

[nksmfamjp]

Once you've processed your brass to accept primers, powder, and bullets, the neck internal diameter should less by 0.003 to .005(interference fit) of the bullet is a must.

I find 0.001” - 0.003” is the range my guns like…..often towards the light side.

 

[358WCF]

I'm using

The load was a 100 grain Nolser Ballistic Tip with 48 grains of IMR 4350 at 2.952 OAL. This is 2 grains under max according to Nolser online data.

I just started working with a new (to me) 257 Ackley. No Roberts brass available so I used some PPU 6.5x57 necked down .007". With 85 gr leftover/partial box bullets & some RL12 that's taking up room in the closet I worked up to book max & a bit beyond for the standard Roberts. Some cases didn't form well, some did. The cases that didn't have enough pressure were snug I.D. the necks. I could have just reprimed, powdered & seated a new bullet. The ones in between still wouldn't take a .257" gauge pin, only the well formed ones would pass a .258" pin. The 4350s I've worked with have some vast burn rate differences between lots. Do you have a chronograph? If yes, What speeds were you getting with the formed brass & 48/4350?

By loading 2 or 3 at each increment above where you stopped, you'll get a better idea of where excess pressure starts with your components. You may also find that your necks open an extra thou or 2 with closer to normal pressure.

As a side note, I have a 700 Remington in 30-06 & all fired cases accept a .308 bullet. [Just saying] Thank all you guys for taking the time to type your answers & thanks to all who took time for the PMs. I'm going to set up for neck turning & clean up the Robert's necks & see how that goes.

Nosler doesn't say what pressure they ran their 257 Ackley up to. Your components are different than theirs. I would try working upwards with powder charge before turning necks. First because turning necks is a pain in the butt. Second because you could screw yourself by thinning the necks too much. Roberts brass is real expensive if you can find any. Bushing dies aren't cheap either.

My Redding dies size the PPUs neck O/D. to .280" with expander removed & .2815" with the expander installed. The PPU brass measures .285" with a bullet seated. I got some neck turned brass with the rifle. After sizing & sorting only about 1/2 of the cases would hold a bullet with my (non bushing) dies. Loaded neck O.D. is .281 to .282" which is a pretty minimal interference fit. They may shoot well. We'll see maybe tomorrow if I get to the range.