Homemade OAL Gage

[JeffL]

I made myself an OAL gauge similar to the Hornady. I bought two 12" brass tubes. One is 3/16 and the other is ??? (Old age has got me. I'm at work and I can't remember what size the other one was. Maybe 5/32. It is just small enough to slide nicely inside the 3/16" tube.) I drilled a 3/16" hole in the bottom of the case (through the primer hole). The brass tube fit fairly tight into the case. I first tried putting treads on the tube but couldn't get it to work. I think it was too thin. On this one I put a nylon spacer on the end and use screw thing from a screen door hold down. I don't think one really needs this. If you very slightly dent the outside tube or something, it will make it slide tighter and will hold the position with out the setscrew. Insert the larger tube in the chamber and push on the smaller tube until it hits the lands, remove and measure. On mine I also slit the neck of the case to make it easier to get the bullet in and let it slide. Sometimes the bullet would stay in the barrel. One just needs to push the whole assemble it out with a dowel if it does that. This only cost me about $5.

Here are some pictures.

 

[Pete in Surry]

I guess I question - -

How accurate these sort of tools are. I make a dummy round up using moderate neck tension and just keep pushing the bullet back into the case with my seater until I can just barely see where the bullet touches the lands. This way, I know exactly what the measurement is between the bolt face and the lands. I use 4 ott steel wool to polish the marks off the bullet each time I chamber it so I can see what is going on. With tools like the one pictured, there is no corelation between the bolt face and the lands, just where the case happens to sit in the chamber.

Nice job on the construction, all the same.

 

[JeffL]

I'm no expert on the measurement but in this case one is indexing off of the shoulder. It seems to me that the distance from the bottom of the case to the shoulder would have to be pretty close to what the distance is from the bolt face to the shoulder in the chamber assuming minimal headspace. I'm guessing within a few thousandths. Would like to get a more expert opinion.

I'm not sure I need a perfectly exact measurement anyway because I'm going to be moving it in or out from there to find the most accurate distance for my gun.

My measurements with this have been real close to what I have measured using other methods.

 

[Wilbur]

JeffL

Nice job!

 

[Pete in Surry]

It does matter - -

I'm no expert on the measurement but in this case one is indexing off of the shoulder. It seems to me that the distance from the bottom of the case to the shoulder would have to be pretty close to what the distance is from the bolt face to the shoulder in the chamber assuming minimal headspace. I'm guessing within a few thousandths. Would like to get a more expert opinion.

I'm not sure I need a perfectly exact measurement anyway because I'm going to be moving it in or out from there to find the most accurate distance for my gun.

My measurements with this have been real close to what I have measured using other methods.

but it depends on how close you want to get. I tune by OAl so I must know exactly where my bullets are touching the lands. I use the bullet-bolt face relationship as my basis to begin tuning. There is also the issue of "Shoulder Bump". To make loaded rounds work well they need to be smaller by .002 or so. Lots of people push the shoulder back .002 0r .003 so that amount must be taken to consideration if one is using just the shoulder as a reference. I realize there are more than one way to skin this cat.

 

[WhelenMan]

I made my own out of a steel 36 inch rod with two aluminum sleeves that I then tapped for a couple of knurled head set screws. I measure to the bolt face from the crown and lock one screw down and then push a bullet just touching the lands and measure to the tip and then lock the second screw. Then I just measure the distance from one sleeve to the other and that's the exact measurement. I usually do about ten of the bullets I want to use since there's a lot more variation than you think and then pick a mid-range bullet and use that measurement. I started out with tapped nylon sleeves but then went to aluminum to get a little more durability and repeatability. This method takes into account the headspacing of the action but is a little slower.

 

[GARMASTERS]

Poor boys chamber gauge

My chamber gauge consists of a full length resized case that has the case mouth trimmed just enough to square it up. I then cut off the end of the case about 1/8" and trim down the shortened case some more with a case trimmer. Seat a bullet in the shortened case a little bit and put the 1/8" ring (squared end toward chamber) over it. Chamber it and close the bolt slowly. Remove and measure chamber OAL. I found a .308 chamber 2.040" long so trimming to the suggested 2.015" was a waste of time.

 

[Pete Wass]

I have one of those slugs

That fits into the neck of a case that has been cut way back to , say, half it'a normal length. One inserts the slug into the cane and then closes the bolt. Once the bolt has registered, open the bolt and remove the case. Check the OAl of the case/ slug and you know exactly how long the chamber is.

What you are showing here seems to be a combination of the slug and finding where the lands are. The marks on the bullet itself will tell one where the meeting of the two are. I think the orign of the thread was about finding the lands; am I wrong?

 

[mc223]

Good Job. I have also made my own, very similar.