Sinclair Group Measuring Caliper Attachment
Precise measurement of group size is a snap with Sinclair International’s
Group Measuring Caliper Attachment.
Ever wonder how we measure and report group sizes out to three decimals? The answer’s really simple and straightforward. The benchrest crowd has been doing it for decades and finally there’s an affordable accessory putting the capability into the hands of every shooter.
Sinclair International was formed years ago by Fred Sinclair and quickly became the Mecca for innovative, benchrest-level reloading equipment and accessories. Acquired recently by Brownells, Sinclair Int. continues to operate as a distinct company with a separate catalog focused on precision reloading tooling and high-quality shooting accessories of every type.
One of the innovative tools they’ve designed is a group measuring attachment that slips on the blades of a dial or digital vernier caliper. Actually, Sinclair offers two attachments. Each one measures three different caliber groups. One measures .22 caliber, 6mm and .30 caliber groups and the other, .25 caliber, 6.5mm and 7mm groups. Pictured is the .22 caliber, 6mm and .30 caliber model measuring a .22 caliber group.
In use, the attachment is in two parts, one fitting each blade of the caliper and secured with 5/62 hex bolts. Once the attachment is adjusted and properly zeroed, you find the two bullet holes farthest from each other and bracket the outside edges of the holes with the proper caliber half circles of the attachment.
With a digital caliper (recommended), you first zero the caliper with the attachment installed and closed. Then read the actual group size directly in the readout window. With a dial caliper, you need to subtract 1.00 inch from the readout on the dial for the correct group size.
The process is simple, fast and accurate. The only downside, if you could call it that, is you’ll probably end up dedicating one caliper to group measurements only, but with stainless steel digital calipers selling for less than $40, it’s a worthwhile investment in tooling.
The best part of the story is the “Group Measuring Caliper Attachment” costs only $25.95 and Sinclair Int. also offers the “6-inch Digital Caliper” for $39.99.
Sinclair Int.
200 South Front St., Montezuma, IA 50171
(800) 717-8211
www.sinclairintl.com
Guns February 2018
