Touch to Jam

[adamsgt]

I hear some like to shoot just off "touch" and others at or near "Jam". Had the ejector out of my bolt to do the "Wheeler Engineering" method for finding touch. Re-visited Tony Boyers book to use his method for finding "Jam". Was using Bart's 68gn Ultra bullets. I noticed that Tony used .003 increments of seating depth for testing his loads and the example in his book had five increments or .012 total. I was curious as to the distance between "touch" and "Jam" and it turned out to be .44 for this bullet in this barrel. That sounded like a lot until I took calipers and put .44 on them. My, what a tiny space. Using .003 increments I could shoot about 14 test loads in that tiny space between "touch" and "Jam". Tony only backed up .12 from Jam. How about the rest of that "zone"? Not sure what to think about that at this point.

 

[FBecigneul]

I found You can go in and out of tune At various degrees of jam or OAL. I had to find something like that when our grand daughter was shooting and opening the bolt when you were jamming created problems with a dumped load in the action. We found we could get good groups or tune when the bullet was barely etched in the lands. That put her and us at about 0.10 off of jump. Life was much better there and we tuned for that.

 

[Jerry W]

Remember too, that jam distance can change depending on how much neck tension you're running. A smaller bushing or work hardened brass can let you "jam" the bullet farther into the throat before it gets pushed back.

I find that my setup only has about 0.030" between touch and jam.

 

[dnal]

Touch VS Jam

I also agree on jam having variables ,(Jerry) but I still try to get a consistant base line on JAM . On touch I find it
easier to get a consistant base line . So I rely on touch reading more. ( usually around .017 to .021 from jam to touch for me)SEATING VARIABLES ???
This has worked for me and find I can get my guns to shoot when seated close to touch or jam . Test to see which is best.
Also shoot Barts 68 BT

 

[Wayne Shaw]

Wheeler's method for touch is about as good as it gets. Jamb to me is when I push the bullet into the case .001" closing the bolt. (with that neck tension, etc.......)

Many ways.

 

[R.G. Robinett]

Remember too, that jam distance can change depending on how much neck tension you're running. A smaller bushing or work hardened brass can let you "jam" the bullet farther into the throat before it gets pushed back.

I find that my setup only has about 0.030" between touch and jam.

Well stated, Jerry.

More precise, even than Wheeler's method, is to obtain a barrel-stub, combination head-space & "throat"/seating depth gauge - a piece of barrel with the reamer run-in only to shoulder depth - gunsmiths were making these when I began in BR, LOOooong ago. The seater stem-length is recorded and becomes the standard, from which very precise changes can be made. RG