| Author |
Message |
Ken (Troad)
Ink's Still Wet on My License!
Username: Troad
Post Number: 6
Registered: 5-2002
| | Posted on Friday, May 03, 2002 - 2:23 pm: | |
Do you know of a book or books that tells how to do headspacing and other routine gunsmithing checks and tests on firearms?? |
Wheelgun (Wheelgun)
Ink's Still Wet on My License!
Username: Wheelgun
Post Number: 6
Registered: 5-2002
| | Posted on Sunday, May 05, 2002 - 2:36 am: | |
Ken,
To check headspace you need gauges that are made for specific calibers or in some cases, for groups of calibers. For example, a headspace gauge set for a .30-06 will work on a .25-06 and a .270. For the common belted magnums, i.e., 7mm Rem., .300 Win., .338 Win., etc., one set of gauges works for all. Many calibers require caliber specific head-space gauges. Among these are the ones that have no "cousins" that use the same basic case, such as the .222 Rem., etc.
Many times excess headspace can be "fixed" by fire-forming the brass, and then neck sizing the cases for use just in that rifle.
Wheelgun>>>---------------->straight shooter! ;^) |
Ken (Troad)
Ink's Still Wet on My License!
Username: Troad
Post Number: 7
Registered: 5-2002
| | Posted on Sunday, May 05, 2002 - 10:59 am: | |
To Wheelgun: Thanks for your help.
Frome: Ken (Troad) |
Adam Firestone (Cruffler)
There's still space on my credit card.
Username: Cruffler
Post Number: 23
Registered: 4-2002
| | Posted on Sunday, May 05, 2002 - 4:25 pm: | |
Whoaaaaa.
Excess headspace can NEVER be "fixed." Once a rifle reaches the point where it will close on a "FIELD" gauge, it is unsafe to fire, and it is a wallhanger. Period.
The reasons for this have more to do with the rifle rather than the case, and thus fireforming cases will likely do nothing to fix the inherent problem.
This problem has to do with the metallurgical terms "yield strength" and "ultimate strength." Yield strength refers to the point at which metal will deform under pressure. Ultimate strength refers to the point at which metal will tear or shatter under pressure.
Older rifles, such as military Mausers or US Springfield M1903's have a wide disparity between the yield strength and the ultimate strength. This is due to the heat treating techniques employed at the time which created a hard, carburized outer shell on the metal, which was very, very hard, but brittle, and a softer, lower carbon core that is much tougher. With respect to these rifles, the yield strength is the point where the hard outer shell on the receiver/bolt has cracked or given, and the ultimate strength is the point where the receiver will shatter or tear apart explosively, and, catastrophically. Given the nature of the metallurgy/heat treatment, there is a very wide disparity between the yield strength and the ultimate strength. That is to say while it may take (and I'm making these numbers up) 60,000 psi to cause a receiver to "yield" (i.e. crack the outer shell), it may take 150,000 psi to cause a catastrophic (ultimate) failure.
But that only tells part of the story. Once the receiver has "yielded," the only thing withstanding the firing pressures is a much milder steel core, and one that will forever continue to stretch with each firing, until it catastrophically yields.
Newer rifles, especially commercial guns made in the last 15 years, use a construction/heat treatment/metallurgy that has a much higher yield strength - but one that is much closer or even identical to the ultimate strength.
What does this mean with respect to headspace? Well, failing a headspace check (closing on a FIELD gauge)is often the only indication to the shooter that either the bolt or receiver has or is beginning to yield. None of the cosmetic fixes which will cause the gauges to "lie," such as shortening the chamber, or fire forming special cases will change the fact that the stress bearing elements have reached the end of their service life.
In sum, if a rifle fails a FIELD gauge - DON'T SHOOT IT!
With respect to books, Ken, you really should pick up a copy of "Hatcher's Notebook," it's an excellent introduction to many of the subjects you're looking into. And you can get it from Amazon, not to mention probably cheaper and barely used at Half.com.
Hope this helps,
Adam
Adam C. Firestone
Editor-in-Chief
CRUFFLER.COM
http://www.cruffler.com |
Clark
Ink's Still Wet on My License!
Username: Clark
Post Number: 1
Registered: 6-2002
| | Posted on Tuesday, June 04, 2002 - 11:06 pm: | |
"Excess headspace can NEVER be "fixed." .. Period."
Not necceasarily. Randy Ketchum, proprietor of Lynwood Guns and sometimes benchrest gunsmith, made a mistake when chambering his .243. He made the headspace .100" too long. To quote him:
"Headspace is the relationship between the chamber and the brass"
So he changed the brass. He put a .257" expander ball through the necks. Then he 243 neck sized to within .100" of the shoulder. He then fire formed the brass. The brass was then 243 with .100" longer headspace.
How is this different from just fireformning the brass?
If the brass is not held at the back of the chamber when fireforming, the walls of the brass will grab the walls of the chamber and the pressure will push on the case head and stretch the brass. The resultant thin spots in the brass are dangerous and contribute to inaccuracy.
Randy's method holds the brass at the rear of the chamber. |
Ibfestus
Ink's Still Wet on My License!
Username: Ibfestus
Post Number: 1
Registered: 3-2004
| | Posted on Tuesday, March 30, 2004 - 12:24 pm: | |
WHOAAA is right. Headspace CAN most certainly be "fixed." Any gunsmith worth his salt can remove the barrel cut as little as 1/2 a thread, set it back and refinish the chamber. It is a COMMON gunsmith job. How did the rifle get headspaced to start with? |
Ibfestus
Ink's Still Wet on My License!
Username: Ibfestus
Post Number: 2
Registered: 3-2004
| | Posted on Tuesday, March 30, 2004 - 12:49 pm: | |
Let me add one more thing. Most rifles suffering a headspace problem, get that way from erosion from within the chamber and not from the receiver being stretched. It is the area of the cartridge shoulder that gets out of spec. and setting the barrel back is no different than starting with a new barrel. Most barrels are made bore specific and the caliber is set up as the barrel is installed. Sometimes a rifle will exhibit excess headspace from a faulty or worn bolt. M-1 Garands come to mind. Military armorers would routinely exchange bolts until they found one that would work. That rifle would be reissued.
I traded for a '98 FN Mauser in 25-06 that turned out to have excessive headspace. My gunsmith removed the barrel, trued the receiver, installed a new bolt, lapped the lugs, set the barrel back 1/2 a turn and the gun would shoot 5 rounds into one hole at 100 meters. Headspace can be fixed but it must be done by a competant gunsmith. |
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