Any feedback on the following appreciated. Did a little reading to come up with the following as some potential guidelines for producing accurate reloads.

Free bore, or the amount the bullet jumps from the case to the lands - 0.015 to 0.020

Bullet run out - less than 0.004, I'm averaging less than .002 so good to go here.

Neck gap, gap from end of cartridge neck to chamber neck - 0.010

Radial neck clearance - 0.002 (not overly concerned on this, I'm using a retail gun not a custom/tight chambered rig. Don't know measure on this. Saw an article in Shooting Times were ceroform (sp?) was pored down the bore to remove a stuck split case. Would this be a good and safe way to get an accurate chamber measurement? )

Again these are measures planned guidelines, any thoughts?

I presume you're looking for a bit of reinforcement. I'll give you my opinion.

"Free bore, or the amount the bullet jumps from the case to the lands - 0.015 to 0.020" This will vary from barrel to barrel. While a majority of chambers do well with bullets close to the lands, just as many (say Weatherby,) do just as well much further. It depends on the barrel.

"Bullet run out - less than 0.004, I'm averaging less than .002 so good to go here." .002" or less is optimum. Anything more increases groups @ quarter inch for each one thousandth up to about .004". Beyond that for long range too many other factors enter into it to make much difference.

Neck gap, gap from end of cartridge neck to chamber neck - 0.010" This doesn't affect accuracy. Zero clearance is enough and won't matter. One thousandth is too much and can put you in a world of hurt. The average factory chamber has over .020" safety factor factored in. No effect here.

As for neck clearance, you are correct, the average factory chamber has at least .005" clearance. Cerrosafe works well, but then so does a fired case. While there is a bit of "springback" in the brass, it is usually measured in the tens of thousandths. Measure a fired case, then measure the loaded round with a seated bullet. The difference is your clearance.

The optimum reload has all the components concentric to the centerline of the bore, whether it's the brass and/or the seated bullet.

Thanks for the feed back. Only thing is what I've read is at odds on the neck gap or case neck length, an excessive gap here will cause the bullet to slug up and fill the space then swag back down once it enters the lands which will promote a negative effect on accurancy. Once I get this measured I plan on trimming my cases with just a .010 gap.

Regards,
Travis

[ 12-06-2002, 03:48: Message edited by: Atlatl ]

"Free bore, or the amount the bullet jumps from the case to the lands - 0.015 to 0.020" This will vary from barrel to barrel. While a majority of chambers do well with bullets close to the lands, just as many (say Weatherby,) do just as well much further. It depends on the barrel.

It also depends on the bullet; Barnes 'X' and WW Failsafe ask for .050" bullet jump. I think it's cause they're so hard.

Free bore is a chambering method and bullet jump are two different things. Weatherby rifle chambers are free bored. All other factory rifle chambers are chambered to SAMMI specs for a given cartridge. In a free bored rifles chamber it is not possible to seat the bullet against the lands. In a standard SAMMI spec rifle chamber you can seat the bullet to touch the lands. SAMMI spec rifle bores brass should be trimmed as directed in your reloading manual. It is always best to keep your brass cases trimmed to .010 under maximum length listed in the reloading book. It is always best accuracy wise to neck size only. Neck sized brass must always be used in the same rifle it was fired in the first time. The more you work the brass the faster it will fail. Factory rifle chambers are cut to SAMMI specs designed to chamber any factory round you stuff in them. It makes no sense trying to treat a SAMMI spec chamber as if it were a benchrest chamber. Rilfe chambers cut to SAMMI specs need the brass FL resized trimmed to length the first firing. After the first firing neck sizing only will keep the brass a perfect fit to that particular chamber and help accuracy potential.