Chamber Clearance vs. Boolit Size

[Shiloh]

The fired cases from my '03 Springfield measures .341 at the neck. The seated boolit,
a 314299 sized at .311+ from my .311 Lyman sizer, measures .337-.3375 at the neck. Is this enough clearance for the brass to stretch upon firing?? Should I try a .310 boolit? My Lyman .310 sizes to about .3098.

I'm using 20 gr. of SR4759 clone powder from Jeff Bartlett http://www.gibrass.com/ at 1700 fps AV. The barrel slugs at .308. I want to avoid high pressure situations.
Let me know will you Cast Boolit Shooters?? Thanks in advance.

Shiloh :castmine:

[monadnock#5]

My NRA Handloading book shows a spec. of 0.3404 nominal, chamber case neck diameter.

However, since your chamber probably isn't nominal in all respects, a chamber cast would be in order. Check the Gunsmithing link for instruction on the various methods.

[felix]

You need 0.001 clearance at all times (including dirty chamber). So, you should have no problem with even more boolit diameter. Experience says 0.0008 is absolute minimum in my BR gun shooting boolits. Any tighter, accuracy begins to go south with the loads I typically use. Any more than 0.0011, the same southern direction. Your gun should show no difference in 0.004 expansion, so it is up to you to play with diameters, and when doing so, maintain the same powder lot and primer. Most 30 caliber guns shoot best with up front static friction. ... felix

[Shiloh]

... Most 30 caliber guns shoot best with up front static friction. ... felix

Could you explain "up front static friction" ?? :?: Is that where the nose rides the lands?? TIA

Shiloh :castmine:

[felix]

Static friction comes from holding the boolit tight during ignition. A tighter case neck is the preferred solution for cast. Never allow the crimp to hold the boolit tight unless you have to make ammo in production quantities. Yes, seating into the lands increases static friction, but not nearly as much as a tighter case neck when using lead boolits. The drawback of a tighter case neck is that the probability of seating out-of-round increases. There, a compromise has to be made, and that compromise is based upon an accuracy standard. The faster the powder, the less amount of static friction is required for the same accuracy potential. ... felix