doublegunshop.com - home Forums General Discussion Classic & Custom Single Barreled Sporting Rifles @ doublegunshop.com A pressure problem or something else?

RecoilRob,
That is why I said above, the proper way to measure the "slug" is with a "V" anvil micrometer or specially made "V" block and normal micrometer. The other methods I mentioned are approximations. The high points on the "slug" represent the grooves in the barrel You can measure the "bore" diameter directly, with a "small hole gauge" and a normal micrometer.
Mike

I understand that Mike but I have the slug in hand, I am confident the measurements are correct and my math is correct, I don't feel the need to go any further, in my opinion, the bore is tight.

If you have such a tool can I mail you a slug so you can confirm or refute?

Actually, even a small hole gage is problematic in measuring bore size. The best method is with a series of pin or plug gages. I believe this was mentioned in the AR thread. That will give a true reading of bore dimensions.

Unfortunately, JES has not responded to either of these threads. His input is very important. I find it difficult to believe that only these two rifles have undersized bores since, it can be assumed all are done with the same tooling.

The guy on AR doesn't seem to grasp that a slug will only record the smallest spot in the barrel.

Is not the "small spot" the fly in the ointment?

I'll push a slug all the way through the bore to feel if I can tell how uneven a bore is, but I admit I doubt I'm much good at picking up small differences. The only bore I worry about slugging is just past the throat, then push it back out the way it came in.

A good rifle barrel can have some choke in it, sort of like a shotgun barrel, and I believe it's a mistake to judge a barrel or choose a bullet based on what could be a little tight spot at the muzzle. It's very possible that a good cut rifler is aware of that, particularly since a prefinished barrel can't be shortened to clean up a bad muzzle.

Some barrels just don't shoot well, but that doesn't seem to be the problem here.

RecoilRob,
If your mind is made up, I can't change it. I do have a "V" block, but I made it for 5 groove barrels, 3 groove takes a different included angle. If a .358" bullet will easily enter the neck of a case fired in the rifle, then .358" bullets can be used w/o problems. BTW, my small hole gauges are round on the end, I wasn't talking about telescoping gauges, which are used on larger holes.
Mike

I was referring to small hole gages, not telescoping gages. They are round, but smaller than the diameter being measured and still end up measuring point to point, making it difficult to get an accurate measurement. You can use feel to get an average reading by rotating as you open them, but it is difficult to get a true reading.

JC,
Pin gauges can also be misused. If they are not presented precisely "square" to the bore the mechanic may think that one that actually fits is too large. The old German proofs used them to determine bore diameter, with their gauges being in .01mm steps. A barrel then marked 7.7, might be 7.71 or it might be 7.79 and still not accept a 7.8 gauge. Or it might be 7.8, if the gauge was not properly presented, at first.
Mike

Mike,

My mind isn't made up but I don't think we're on the same page.

What does a 0.358 bullet entering the neck of a fired case have to do with a tight bore?

Rob