load development range ?

[cw308]

jm
That is exactly what I do with the same firing pin assembly remover . You explain it with pictures much better the me . I do the same when testing for ogive length the only difference for finding ogive is on the raising of the bolt the pressure is off the lugs when the bullet leaves the rifling . Both work well and repeatable measurements for me.

Chris

[Bart B.]

Across many rifles I've measured the minimum clearance between case head and bolt face with the extractor as far back as possible, none put, held, pulled, forced nor positioned the case head against the bolt/breech face. A few to several thousandths clearance always existed. It is very easy to measure that "head clearance" (defined in SAAMI's glossary) in your rifles. Done right, you will easily dispell the myths so often preached as gospel.

Rimless bottleneck cases with headspace .002" less than chamber headspace in rifles with spring loaded ejectors in bolt faces are pressed forward putting their shoulder against the chamber shoulder. In all rifles, such cases are driven forward by their 20+ pound firing pin spring driving the 3 ounce pin forward near 9 fps until it stops the same way.

A bit of head clearance is needed so the bolt doesn't bind any amount. Even a slight bind puts the bolt head in different places across all rounds and degrades accuracy. Worsens if bolt face is not squared up.

[cw308]

Guff
I thought it was directed at me , Sorry . I see alot of guys having case head separation , have no idea how there reloading , never happened to me but after seeing that I keep the case extracting tool in my range bag for308 , a number of guys shooting 308 have used it alot . Just like a stuck case remover tool , it only has to happen once , happened to me . Ordered one and I hope I never have to use it , lube ,when you feel resistance add alittle more .

[Bart B.]

Originally Posted by F. Guffey

I believe it is safe to assume you no longer recommend reloaders do like bench resters.

Not true. They shoot smallest groups. I recommend folks do what they do.

[F. Guffey]

Again: I purchased a mill from a recourse person for everything military like the 03, M1917, etc. When finished loading the mill he asked me about head space, he said he had talked to another smith, the other smith suggested he talk to me about? I thought that was nice.

It seems he had gotten off on one of the other forums, before he got an answer members got nasty and then it turned ugly. that forum dumped the archives and started over.

He had 25 30/06 head space gages, a few went back to the time they used the case body/shoulder juncture. He did not have a gage that would determine the length of the chamber, his gages told him his chamber was not go-gage length nor a no go-gage length chamber.

I informed him I could measure the length of the chamber from the shoulder to the bolt face 3 different ways without out a head space gage. I offered to modify one of his go-gages to measure from go-gage length to infinity. He refused because the gage would no longer be period correct.

Long story short, his chamber was .0025" longer than a go-gage length chamber. Fixing it? that was up to him. Problem: The rifle he was building was a Rock Island 1911 with a straight bolt. He had no less than 100 03 bolts and I have no fewer than 30 03A3 bolts. I offered to measure the ability of his bolts to off set the length of the chamber by .0025", I assured him I did not have such a bolt and I told him I doubted he had one and there was not one straight handle bolt between three of us.

I have replacement bolts that came 2 to the box and the box was stamped as complete bolts. There is not .001" difference between the two bolts so it is not easy to shorten the length of the chamber. He contacted another resource person for straight handle bolts.

I offered to form cases for his new creation THAT WOULD OFF SET THE .0025" difference between the length of his cases from the shoulder to the case head and chamber from the bolt face and shoulder of the chamber.

F. Guffey

[cw308]

Guff
You sure went above and beyond to help . Ever think of moving to LI NY

Chris

[Reloadron]

Mr. Guffey back in post #46 did you or did you not state:

Forget Hatcher, he created .060" clearance between the shoulder of the case and shoulder of the chamber; I never could determine if he figured out why he did not experience case head separation. Again, it did not take me long to determine why my cases did not have case head separation. Again. my cases do not have head space but if they did the difference in head space between my case and chamber would have been .127"

Do you have any reference to when and where Hatcher did this? Reading Hatcher's Notebook I see no reference to him ever doing this? I only see a reference to Hatcher reaming a chamber as much as 0.025" over nominal. Hatcher describes in his notes, in detail, why he felt he never experienced a case separation.

The extractor is holding the case head against the bolt face. When the explosion comes along the head of the cartridge is supported by the bolt face so the cartridge is not going to move back leaving the shoulder to move forward expanding to fill the excess headspace of the chamber. To quote Hatcher "I doubt very much we would ever get a rupture this way, no matter how much we reamed the headspace, we would just move the shoulder further and further forward".

So, Hatcher never, as you claimed, reamed a chamber to 0.065" over the nominal dimension. When he did ream a chamber over size creating excessive headspace he clearly stated why he felt there was no case separation.

Since we seem to like the 0.060" over a nominal headspace dimension in a chamber it was actually done but not by Hatcher. The testing done was done by Lieutenant Robert C. U.S.N.R. and done at the Des Moines Ordinance Plant in 1943. The testing had nothing to do with case separation but was a test of Velocity as a Function of Headspace.

"He selected a number of cartridge cases which all gauged 1.940' head to shoulder. The bullets caliber 30 ball, M2were carefully gauged by hand and were selected to have the same diameter and overall length and were also selected as to weight +/- 0.1 grain.

The cases were loaded with hand weighed charges of IMR 4676 powder. The accuracy of the weighing was such that the final balancing of the scales was determined by the addition of one or two sticks of powder, of which it takes 60 to weigh one grain.

The bullets were all taken from one machine in order to insure uniformity of the ogive. The cartridges were all fired in ten round groups. The instrument velocities were all taken at 78 feet".

Reference Hatcher's Notebook pages 245 through 252.

This thread has now been totally dragged off the original topic, congratulations!

Ron