load development range ?

[Bart B.]

You claim you have .001" clearance, all I want to know is how you get .001" clearance if a bench rester full length sizes their cases and as you have claimed they have been doing it for decades.

"Head clearance" on my full length sized 308 cases was about .002". The distance from bolt face to case head when round fires with its shoulder pressed against the chamber shoulder. No cam over as the shell holder never touched the die bottom full length sizing fired cases.

"Head space" on rimless bottleneck cases is a term taken from the gauges used to verify the mating dimensions in their barrel chambers. Makes comparing case to chamber fit and clearance easily understood betweeen people. Both case and gauge reference points are at the same place. 308 FL dies have about .005" less headspace than their GO gauges.

 

[cw308]

Guff
I'll try to explain how I do it . First I found my chamber measurenent by using a go Gauge and shims , for my 308 the gauge is 1.630 and with a .002 shim my stripped bolt closed with a slight resistance . So my way of thinking is 1.632. from that point I checked that measurement with the go gauge in my RCBS Precision Mic . My fired cases get shorter from expansion , using the Redding Competition Shellholders with different deck heights I size my cases with a RCBS Standard full length die to size the case to 1.631 testing in the mic . Fired case is .002 -3 shorter . That's what works for me , I trim every firing it's more like a clean up , not much trims off . My sizing is smooth , don't have to muscle anything and finish with a case measurement of 1.631 with my mic . I wouldn't think I'm pressing the shoulder back , it more like pressing the case to the shoulder when the case body is squeezed down . It may be possible for me to do this because I'm not loading hot , whatever it is it's working for me . Sorry for being long winded but it's the only way I can explain how I size .

Chris

 

[F. Guffey]

You claim you have .001" clearance, all I want to know is how you get .001" clearance if a bench rester full length sizes their cases and as you have claimed they have been doing it for decades.

I believe it is safe to assume you no longer recommend reloaders do like bench resters. reloaders were led to believe bench resters full length sized their cases evetime and they were told bench resters have been full length sizing for decades.

And then there is that thing about 'cam over'. I have 12 presses that are cam over presses, in the old days the cam over press was called a bump press. I have 4 presses that do not cam over, in the old days non-cam over presses were called non-bump presses.

 

[F. Guffey]

Forgive, I was not including my progressive presses. When I turn my Rock Chucker press into a progressive press I add a Piggy Back 11 attachment. the Piggy back attachment has a one way clutch; what does that mean? It means the press that is attached to the attachment can not be a cam over press.

F. Guffey

 

[cw308]

Guff
I have no idea what your saying , I just told you how ( I ) sized to .001 claiming this or that I never do . Only what I do . What you do or what you do it with is fine if it works for YOU . You asked for an explanation and I tried my best . Guess it didn't .

Chris

 

[F. Guffey]

Guff
I have no idea what your saying , I just told you how ( I ) sized to .001 claiming this or that I never do

I did not assume you had a clue, I did not ask, I was asking Bart B.. He has insisted reloaders should do like bench resters. he claims the bench rester full length sizes their cases evetime. And now it appears he has changed his methods and or techniques. He has also insisted the case takes off for the shoulder of the chamber because of powerful primer strikes.

When I fire ammo in most of my rifles the shoulder never makes it to the shoulder of the chamber; and I have killer firing pins, I believe it is a bad habit to fire ammo with the shoulder of the case is against the shoulder of the chamber.

It does not take me long to look at the case to determine what happen when the round was fired. One day I chambered an 8mm57 round in one of my rifles that is chambered to 8/06. Because my cases do not have head space I did not have case head separation because the shoulder of the 8mm57 never made it to the shoulder of the chamber.

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"

F. Guffey

 

[Reloadron]

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"

I do not believe that is quite what Hatcher actually did. I do understand why Hatcher had no concerns or worries about any incipient case head separation. The rifle used as a 1917 Enfield. On Nov 1, 1946 Hatcher and Al Barr took a rifle out to the range. Now for the following numbers to make sense we need a clarification as to chamber headspace. If we look at the SAAMI Drawing of the 30-06 Springfield rifle cartridge and chamber on page 95 of the link take note of the chamber reference dimension indicated by a small triangle. Case head to the start of shoulder is 1.9399" which we can call 1.940". Original GI Head space Gauges were cut 1.940" = Go. 1.946" = NoGo and lastly 1.950" = Field. All the SAAMI system has done is change the datum point on the shoulder. The original GI datum point was at the start of shoulder where the case OD was and still is 0.4425" OD the SAAMI datum point was moved up the shoulder to where the case shoulder OD is 0.375" OD. All of that is plain and apparent in the linked chamber drawing.

So all that considered Al Barr and Julian Hatcher dragged their rifle out to do some testing, They reamed the chamber out to 1.955" which was now 0.015" over nominal. They fired 5 shots with 172 grain M1 Garand boat tail bullets. They got excellent groups at 100 yards. The rifle fired flawlessy and the extracted ammunition showed no signs for any concerns. The chamber was then reamed to 1.960" adding 0.005" and 0.020" over nominal and fired 10 more rounds getting considerably a larger group. The headspace was again tested and nothing changed. The chamber was then reamed to 1.965 and are now 0.025" over nominal.Fired 5 more shots and not much changed. So this chamber is now 0.025" over nominal and 0.015" above the GI field gauge. They were also 0.025" over chamber nominal. None of the fired cases even began to show any incipient case head separation.

One consideration here the case head is held securely in place against the breach face (Bolt Face) by the extractor. The firing pin will hit the primer since the case head is held in place and when the firing pin severely smacks the thin primer membrane the case is not going anywhere. The primer goes bang and the case goes bang slamming back on the breech face, the shoulder goes forward stretching until the case shoulder rams against the chamber shoulder wall. Hatcher covers all of his views on this, around pages Start reading around page 246 in Hatcher's Notebook. I have the hardcover but a downloadable version should also cover this. Hatcher never reamed the chamber 0.060" oversize during those test.

Now, years later a Lieut. Robert C. Wyckoff did some very interesting test but his goal was testing velocity as a chamber was reamed.He actually reamed his chamber 0.065" over nominal. The velocity plots are quite interesting stuff,

Ron

 

[jmorris]

When I fire ammo in most of my rifles the shoulder never makes it to the shoulder of the chamber; and I have killer firing pins, I believe it is a bad habit to fire ammo with the shoulder of the case is against the shoulder of the chamber.

That’s actually not uncommon in benchrest and pretty easy to figure out where you are at.

You might use a full length “body” die but you are sizing to the chamber not just cranking the die down and going.

You start by removing the bolt plug/firing pin assembly and you will eliminate the resistance upon closing the bolt. With an empty chamber it will fall closed once the lugs are past their place in the receiver.

Now place a fired case in the receiver and run the bolt back forward, does the bolt close on its own? No. Now lower your size die down incrementally until you can see the bolt lever begin to change position like the arm of a clock. About half the throw is what your looking for. If you have indicators that you can use for measurements, you can be very precise.

Once you set dies up with a rifle like this, you can get many, many firings out of cases without even needing to trim. Only good for the given firearm though.

 

[F. Guffey]

The chamber was then reamed to 1.965 and are now 0.025" over nominal.Fired 5 more shots and not much changed. So this chamber is now 0.025" over nominal and 0.015" above the GI field gauge. They were also 0.025" over chamber nominal. None of the fired cases even began to show any incipient case head separation.

The cases did not show any signs of case head separation, had the shoulder of the case been driven to the shoulder of the chamber with normal loads the case head would have had the beginning of case head separation or the case heads would have separated.

Again: I used a Mauser chambered to 8MM06 to fire 8MM57 ammo. Again: The clearance was .127" between the shoulder of the case and shoulder of the chamber. I did not experience case head separation, the case shoulder did not move. the shoulder of the case became part of the case body and the case was ejected with the hint of a neck.

Again, I have a M1917 with a chamber that is field reject length + .002". When a minimum length/full length size round is fired in that chamber there is .016" clearance between the shoulder of the case and chamber shoulder.

When I fire a minimum length/full length sized case in that chamber the shoulder does not move, part of the shoulder becomes part of the case body and the shoulder on the case when ejected is a new shoulder that was part of the old shoulder and neck.

I form 280 Remington cases to 30/06 cases; knowing the chamber in the M1917 is long I off set the long chamber with the formed case by adjusting the die off the shell holder .014", By increasing the length of the case from the shoulder to the case head .014" the forming process allows me to have the magic .002" clearance.

F. Guffey

 

[F. Guffey]

Bart B. has claimed his firing pins shorten the case from the shoulder to the case head as much as .005". I have insisted he go through the sequences of events involved between pulling the trigger and the bullet leaving the case to get a rational.

I have given two examples of my cases never making it to the shoulder with two different rifles. If my shoulder does not make it to the shoulder of the chamber I can measure it.

I have killer firing pins but they can not be as powerful as Bart B. because I have installed primers in cases without bullets and without powder, What does that mean? It means I lightened up the load/work on the firing pin, surley it is easier to drive an empty case than it is to drive a full load round.

And I have no ideal how the firing pin can hit the primer while the primer is setting still without busting the primer. BUT Bart B.s waits until the case shoulder gets to the shoulder of the chamber to bust off.

F. Guffey

 

[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.]

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