How to Craft Your Own Chamber Length Gauge
We are sad to report that long-time Forum member Frank S. (aka fdShuster) passed away in 2015. Frank was a very knowledgeable shooter who was always willing to help others. Here is one of Frank’s smart inventions. He devised a way to measure the length of a rifle’s chamber using a fired cartridge case. Frank’s system works by cutting a “collar” from part of the case neck. This then slips over a bullet seated in a case loaded without powder or primer. As you chamber the dummy round, the collar will move back to indicate the full length of the chamber. (Make sure the bullet is seated well off the lands so the dummy round can chamber fully.)
The pictured gauge can be home made (for free) with components you already have on hand. Frank explained: “I used a Dremel cut-off wheel to cut the front half of the case neck off. A jewelers needle file to de-burr both rough-cut edges. The cut-off surface does not need to be perfectly square, because you are using the original straight mouth to make contact at the front of the chamber. Seat any old bullet to the approximate normal seating length. Next apply a tiny drop of oil on the ogive of the bullet, and slide the ‘collar’ over the bullet. Then chamber the dummy round and close the bolt. Extract the round slowly and carefully and take the measurement with calipers (see top photo).”
Frank’s DIY chamber length gauge works well. In a related Forum thread, Frank posted: “I’ve compared length dimensions doing it this way and with the chamber length shown on my chambering reamer drawings, and the Sinclair gauge, and they are all within .001″ or so.”
Commercial Chamber Length Gauges May Not Work with Custom Chambers
Frank did use Sinclair chamber-length gauges for some applications. These bullet-shaped gauges slip into a cartridge, but “it’s inconvenient to order that little gauge only… without spending $6 shipping for a $7 item.” Moreover, the Sinclair gauges may not fit a custom chamber with a tighter neck dimension because the diameter of the ring at the end is too large.
As an alternative to commercial gauges, the collar-type, homemade gauge will function properly in a custom chamber. The homemade gauge will work with smaller-than-standard chamber neck dimensions, as long as you use a piece of appropriately-turned fired brass that fits your chamber.
Sad this wasn’t posted while Frank was still alive!!!!!
Very ingenious.
Paul
Smart. Ive used the sinclair tool but have to give this a try. RIP Frank.
Yes, RIP Frank. I’m very sorry to hear he’s died – the Forum and those of us who never had a chance to meet him will still mourn his loss.
I’ve been doing this to all my chambres for a few years now for obvious reasons…
Longer neck is always better and who the hell likes trimming/chamfering and deburring ?
Also keep in mind that a gap between the neck and the chamber is not ideal because under pressure the part of the bullet that is directly above the gap will slightly swell into this gap upon being fired, then the swelled part of the bullet has to swage itself when moving forward… most likely not good for the bullet jacket and could even rise chamber pressure very slightly.
After going this to a dozen or so chambers I’ve noted I can let the brass grow 0.015″-0.025″ longer than the Max SAMMI spec leaving me 0.015″ safety gap.
Just what I needed! I’ve used the Sinclair gage in the past, and went to site to order one for .25. As Zero wrote, the tool gage is $5.99 and shipping is $7.95.
Zero also has good points about letting case lengths extend. Just ensure to have that .015″clearance!
(slapping forehead with palm) Why didn’t I think of that? Obvious answer: Because I am not nearly as smart as I sometimes think that I am.
Made a couple of these for two different caliber chambers and they work great . As Frank said ; “within a .001 or so ” , and his comment is correct . Never got more than a .001 variation when taking a measurement . Great tool for neck length clearances .
Found out I had a extra .010 and it saved a whole bunch of trimming and let me “grow” the neck .005 longer . Hey ; can’t hurt anything …..
Another example of why I come to this site before any others when I have reloading questions. It has taught me much. In reality, it is kind people like Frank, who share their wisdom and knowledge with lesser beings like me. Thanks to the people at Accurateshooter for maintaining such an awesome site to share info!!
I built one of these for my 7mm-08 Xbolt and it worked well, but required a little fitting so the collar would slide with the right amount of tension. Now for the 7mm Mag. Thanks again for the info!!