January 9, 2022 This will remove dents and give you a more uniform neck tension. Choose a diameter for the mandrel that will provide neck tension. A little case preparation will help ensure a more uniform neck tension. Consistent bullet seating is possible by keeping your neck tension uniform. This results in better accuracy and a lower Extreme Spread (ES/SD). Lapua brass, especially 6mmBR,6.5×47,6.5 Creedmoor and.308 win, comes from the factory with tighter than optimal necks. After running an expander mandrel along the necks, you should inside chamfer bullet mouths before you seat them. Both Sinclair Int’l’s and K&M’s expander mandrels will leave necks with enough neck tension (more that.001) You can then seat bullets with no additional operation. You can then seat bullets without any additional operations by lubricating the mandrel. Above is the Sinclair version. This $32.99 unit can fit caliber-specific expander mendrels ($9.99), which measure approximately.001 Each caliber has a bullet diameter that is less than the unit. This “Gen II” design is updated and completely captures the die’s mandrel so it cannot be pulled out. The die cap also features an O-ring that allows the mandrel’s self-centering within the case neck. Sinclair now offers three sizes for expander mandrels:.17 -.338 (#749-011-715WS);.357-.50 caliber(#749-018-843WS); and a special.50 Cal body for large-diameter 50 BMG press (#749-019-163WS) for $39.99. All Generation II dies are made from stainless steel. The standard diameter 7/8-14 Dies include the Sinclair Stainless Steel Split Lock Ring. Neck tension*. This will make it easier to seat bullets and will also help you remove any dents from the case mouths. Once the case mouths are all expanded, and uniformly round, then do your inside neck chamfering/deburring. These expander mandrels are also useful for “necking up” smaller diameter brass or preparing brass for neck-turning. Forum member Mike Crawford says: “These expanders can also reduce the runout from offset seating. To increase the thickness variance, expand the necks prior to bullet seating. The Sinclair system will allow the necks to spring back perfectly and not pull out of the center. This creates plenty of tension and makes bullets sit more centered. This is what I do, even with turned heads, to improve my seating. Expander balls on Decapping Rods: Mandrels vs. Expander balls
If you don’t have an appropriate expander mandrel to fit your brass, you can use a full-length sizing tool with an expander ball to “iron out” your necks and reduce tension. The necks will be more worked if you use a die with an extender ball. This is because the ball first sizes them down and then expands them again. Using an expander ball instead of an expander mandrel is more common, but not always. * This is.002? Tension is what we observed with Lapua 6mmBR (6.5×47, Creedmoor) and.308 win brass (.308 Win). This may vary for smaller or larger cases and different brands of brass. 21st Century Shooting can provide a smaller-diameter version if you have too much tension in your current mandrel. 21st Century Shooting even offers Titanium Nitride-coated mandrels with low friction.
Similar Posts:Tags: Cartridge Brass, Case Neck, Expander Mandrel, Neck Tension, Sinclair Mandrel.
