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July 18th, 2008

6XC Brass Dimensions and Capacities

German Salazar, a top small-bore and centerfire shooter, uses the 6XC cartridge for his long-range matches. German has tried a variety of different types of brass for this cartridge, including necked-up 22-250 brass and 6XC brass from Norma and David Tubb (Superior Shooting Systems). German’s measurements reveal significant differences in water capacity, as well as neck-wall thickness.

6XC Source Brass Dimensions

Case Capacity and Pressure Issues
German has noted significant variances in capacity among the different “flavors” of brass. Norma-headstamp 6XC brass has 49.3 grains of H20 capacity, while Norma 22-250 brass holds only 47.8 grains of H20. Third-generation Tubb-brand 6XC brass is somewhere in the middle, with 48.6 grains of capacity. NOTE: These differences in case capacity are large enough that you MUST adjust your load to the brass type. A safe load in Norma 6XC brass could be WAY over-pressure in necked-up Norma or Remington 22-250 brass.

We ran a 6XC QuickLOAD simulation with 115gr bullets and H4350 powder. QuickLOAD predicted that the observed difference in case capacity can result in pressure differentials as much as 4,500 psi! In other words, if you switch from Norma 6XC brass to a lesser-capacity brass type, your pressures could rise 4,500 psi (using H4350 and 115gr bullets).

Neck Thickness and Chambering Issues
German noted that the different types of available brass varied quite a bit in neck-wall thickness — from 0.0121″ (Norma 22-250) to 0.0140″ (Tubb 3rd Gen). Consequently the diameter of loaded rounds also varied. Depending on the brass you chose, your loaded rounds could be 0.267″ at the neck or 0.271″. That’s a huge difference and it’s something you need to take into account when you have your chamber cut for a barrel. For a cross-the-course rifle, you might want a chamber with .003″ total clearance over a loaded round. Obviously, to achieve that clearance, you’ll need to set chamber dimensions base on your preferred type of brass.

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July 18th, 2008

New Rail-Mount System for Harris Bipods

Mark Deros of Alamo Four Star, LLC, has invented a new system that attaches Harris bipods to a Picatinny Rail mounted on the fore-arm of a rifle. The new locking system, called the DLOC-S, replaces the top plate of the bipod with a quick-release clamping system. The spring-loaded DLOC clamp allows the bipod to be attached to the rail easily with no screws or bolts to tighten. Just pop open the DLOC and slide it on the rail.

The makers of the DLOC system have created a video that shows the DLOC being installed on a Harris bipod with Poc-Loc. The whole operation takes less than 30 seconds and can be done without tools.

CLICK HERE to view DLOC 30-second Installation Video

The DLOC selling price has not been finalized, but Mark Deros expects it to be “under $100.00″. Product release is set for the second half of September, 2008. For more information, call (210) 432-7006.

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