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View Full Version : Setting rimfire headspace accurately, Calfee



Kathy
12-24-2007, 09:07 AM
My friends:

To "accurately" set the headspace in a rimfire gun one should remove the extractors and the firing pin assembly from the breech bolt.

I even remove the indent ball and spring from Shuls and Anschutzs, although I believe one could get by without this step.

Setting accurate headspace is like using a micrometer.....the tension placed on the breech bolt by the firing pin spring and the extractor springs makes it impossible to accurately "feel" the gage.

I had a friend of mine set the HS on his 2007.....he set it at .043"....with the extractors and firing pin in place....The rifle would shoot some amazing groups but he was having flippers.....he brought the rifle to me and the first thing I did was to check the headspace. It would just barely accept a .040" gage, with pressure on the bolt handle, after I removed the extractors and firing assmebly.

I re-set the headspace, "correctly" at .043" and the flippers stopped.

MY friends, having said all the above, it's your gun, you of course, can set your headspace any way you want.........

Your friend, Bill Calfee

Fred K
12-24-2007, 10:04 AM
Bill
I can understand the effect the extractors have on HS. But for the life of me I don't get the need to remove the firing pin assy. Is it the sear pressure ?
Please explain.
Thanks
Fred K

DonMatzeder
12-24-2007, 10:09 AM
And if it is sear presure, is that not the state that we would normally be in and therefore the correct way to set the headspace?

Fred K
12-24-2007, 10:11 AM
And if it is sear presure, is that not the state that we would normally be in and therefore the correct way to set the headspace?

Seems so
Fred K

cpeters
12-24-2007, 11:26 AM
Thanks for the reminder Bill now a question related to this?

Granted there is something to say for having the right tool for the Job but for the average Joe who would like to know what his headspace is and does not have headspace guages.....is there a safe way to improvise?

Take for instance when building a racing engine if there is concern about valve to top of the piston clearance you take a thin layer of modeling clay and lay it on the top of the piston, do a trial assembly, rotate the engine, take it back apart then measure the thickness of the clay with a mic and you have your clearance.

I suspect you could do something similar with a small sliver of something like clay or very soft lead and get an accurate measurement, if it were not for having to rotate the bolt which might tend to smear giving a false measurement.

Any thoughts?

Thanks in advance for your answer.

Charlie

burtona
12-24-2007, 11:44 AM
Perhaps someone will explain WHY you cannot get a good headspace reading by slipping the extractors over the headspace gauge rim before inserting the gauge into the chamber with the bolt. The extractors do not come into play if there is already a cone breech or extractor slots cut. If there is no clearance for the extractors already cut in the breech end then the bolt could not be closed except on a bolt with a Winchester style extractor.

RJM
12-24-2007, 03:32 PM
Using headspace gauges is all about feel. With the extractors and firing pin in place, you're feeling everything they are doing, and nothing of the actual closing of the bolt on the gauge. The only way to use a headspace gauge is with a stripped bolt, so you can actually feel the closing on the gauge.
Regards, Ron

JJ-IA
12-24-2007, 03:34 PM
For what it's worth, I agree with Bill C.
I remove the firing pin & extractors from my rimfires and the firing pin from my center fires (shoulder bump) for the same reason.
In just a few ten thousands range the bolt handle will range from fall under its own weight, holding its own weight against gravity (with little or no felt closing resistance), and requiring a closing force that can be felt. With the extractors and firing pin installed you would never see or feel the difference a thousands or two makes, and something’s going to compress or flex to make up the difference.

JJ-IA
12-24-2007, 03:39 PM
Ooops, Ron beat me to it.
I was typing while he was posting. :)

Kathy
12-24-2007, 06:06 PM
MY friends:

It's Christmas Eve.....both of you are absolutely correct....

My dear friends: There is a correct way to do anything, including setting headspace "accurately"..

Oh, before I forget:

Mark, "Lovan" Smith: Thank you for the sweat shirt, killer, but, I ain't paid you for the tee shirts yet.....oh Mark; is this thread better?

My friend Janet Westfall: Janet, thank you and Wiley for the Christmas card, and, Congratulations, Janet, on your IR-50 Shooter of the year Agg. Championship! Man! And Janet, Congratulations on your SOTY Sporter Championship, in both the 5X5 and 4x5 classes....Awesome!

And while we're on the IR-50 Shooter Of The year Championships, Congratulations to my old buddy Kirk Gaston for his 2007 SOTY 10 1/2 pound Championship, in both the 5X5 class and the 4X5 class! Man Kirk, Killer shooting!....and then, my friend Kirk Gaston also won the 13 1/2 pound SOTY 5x5 Class and my friend Gary Lemons won the 13 1/2 pound SOTY 4x5 Class......Awesome...

All my friends that have sent me Christmas Cards and pictures and stuff:

Thank you from the bottom of my heart....Merry Christmas....

Your firend, Bill Calfee

cpeters
12-26-2007, 07:16 AM
Sounds like you guys are pretty knowlegeable in this area.....
After reading this post it got me thinking....I opened the Brownells catalog and they show basically a go, no go, and field gauge. How specifically do you measure the headspace? How do you get an exact measurement? Do you purchase a "set of custom guages" in say .0005 incriments or do can you put a known one in and measue the clearance by pushing the bolt against the headspace guage in the closed postion while measureing with dial incicator set on the end of the bolt?
I would just like to better understand.

Thanks

Charlie

burtona
12-26-2007, 08:12 AM
I bought a set of gauges in .001" increments several years ago from Brownells from .040" through .046". I don't think they sell them anymore. Most of the reamer grinders can custom grind a gauge in any dinmension you want. Dave Kiff has made a couple for me at a reasonable cost.

To headspace measure accurately a depth micrometer can be used to measure to the bolt face from the receiver face, and measure the length of the barrel tenon with the depth micrometer. The difference in the two measurements will give you the headspace. Of course you have to do this with the barrel removed.

BTW, no one has convinced me you can't accurately use gauges with the extractors in place. There is no rotation of the bolt nose when the bolt body is rotated to check a gauge on a RF rifle. Remove the firing pin assembly and you can feel the resistance just fine. I've done it both ways over the years and I can't tell the difference. But, maybe I'm just old and stubborn!

Fred J
12-26-2007, 11:02 AM
I also can measure HS with the extractors in place. I feel it's more important to have suffient clearance between the bolt face and the breach, than whether it .041 or .045 HS. I also remove only the FP, and I can feel the differance just fine. To check the bolt to breach clearance, all you have you use is Plasti-Gage you can pick up at your local auto parts house.

garrisone
12-29-2007, 07:09 PM
Why Not DO IT RIGHT THE FIRST TIME.