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Old February 3, 2013, 10:46 PM   #1
GunAddict1962
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Question on Neck Sizing .308 for M1A

I recently purchased an RCBS neck sizing die for .308 I shoot from my Springfield M1A (Loaded version). Neck sized some recently fired brass this evening and then dropped it into an L.E. Wilson headspace gauge. Noticed it sat a bit high in the gauge and checked closer with my micrometer and found that the neck sized brass was on average .004 high (from top of where it's measured from the guage). Is that a problem? Does it mean that headspace in my chamber is a bit over spec? I assume that the L.E. Wilson gauge is at industry spec. I'm loading 168gr Sierra HPBTs over about a 90 percent of max charge in Winchester brass. Does something I'm doing, or what I'm shooting, rule out neck sizing? For this particular rifle, I've always FL sized in the past. No issues. Fairly good accuracy. Thought neck sizing would allow me to tighten up my groups a bit.

Thanks...
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Old February 3, 2013, 10:55 PM   #2
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It might not chamber so easily... most folks shooting semi-autos give the cases a full length sizing, just to make chambering easier. That way you don't run into function issues.

I don't think .004" is out of spec, if I'm understanding you correctly. I believe the no-go gauge won't chamber until you get to .006" over SAMMI spec. And that's just the no-go... the field gauge is going to give you a bit more than that, so I believe your chamber is fine.
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Old February 3, 2013, 11:11 PM   #3
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Is your gage clean?

I have never reloaded for the M1A but I believe most people use a small base die for semi-autos. I feel your cases should fit the min/max gage. Do you want to chance your ammo causing a not quite full in battery condition?

Just my $.02
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Old February 3, 2013, 11:23 PM   #4
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Gunaddict1962, brand new cases have always shot most accurate in all the USA service rifles. Some of the military teams tried full length sizing their fired match cases only to have them shoot worse than new ones; same with commercial match ammo.

The reason's the bolt face in those rifles were never squared up. Any new round fired in them ends up with its case head way out of square. It's never squared up in any reloading process so they shot poorly.

The above aside, proper full length sized cases in high power rifles has always give best overall accuracy for decades. Even the benchresters moved away from neck only sizing not too long ago and now use full lengths sizing dies with bushings sized for their cases.

Dan, most folks shooting semi-autos give their cases a full length sizing, not only to make chambering easier, but because they're more accurate. Even on those whose bolt face is only minimally out of square. Nobody's ever reloaded loaded fired cases from semiauto USA 30 caliber service rifles that shot as accurate as Federal Gold Medal Match or the late 1960's National Match lots of M118 ammo with brand new cases in those huge MIL SPEC chambers. Go figure. . . . .
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Old February 4, 2013, 08:23 AM   #5
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I think I'll mostly stick with FLS for the M1A. Will complete the loading on a few of the already neck sized cases and see how they chamber just for the heck of it. If they chamber hard, I won't shoot them.

Thanks, all. This forum and the knowledge of its members is a terrific resource.

Luke
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Old February 4, 2013, 11:44 AM   #6
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Never, ever, ever neck size for a Garand/M1a action.

This mechanism has a free floating firing pin that is retracted only at cam down. The receiver bridge is an ineffective barrier at blocking the firing pin from touching the primer during feed as its primary function was firing pin retraction during extraction.

This is a receiver bridge from a M1 carbine, functionally it is identical to that of a M1a.



This is the Garand/M1a receiver bridge. You can see the slot when the firing pin clears the bridge.


In terms of bolt lug rotation, that pencil mark on the bolt lug is when, during cam down, that firing pin is able to clear the bridge.


If you have an overly long case, you are requiring the bolt to stop, to crunch fit the case to the chamber. In these mechanisms this is highly dangerous.

This picture, the firing pin tang is just touching the receiver bridge and the firing pin is fully forward.


At this point, when the bolt stops, that free floating firing pin is wacking the heck out of the primer, and your lugs are not engaged. If you have a sensitive primer and the bolt lugs are out of battery, this is what happens:


The unfortunate whose receiver heel blew off in his face said that his cases were inadequately sized. He was using CCI #34 primers, the proper primer to use in these mechanisms, he positively stated that he had reamed the primer pockets to depth and all primers were examined, and they were below the case head. He also said he put a round in the chamber and dropped the bolt. He must have had a sensitive primer and the lugs were not in engagement when it went off. If he had properly sized his cases his chances of having an inbattery slamfire would have greatly increased.

Never, ever drop a round in the chamber and trip the bolt release. In this mechanism always feed from the magazine. When a round is fed from the magazine the friction between magazine and round slows the bolt and that reduces the kinetic energy of the free floating firing pin. This will reduce the chances of a slamfire.

Always full length resize for these actions. Always size your cases with a small base die. Always set up your dies with a Wilson type case gage, and always use the least sensitive primers. The best primers for this mechanism are CCI #34’s and the Tula7.62 as these are said to be “mil spec” primers. Never , ever use sensitive primers in this mechanism. The most sensitive primers on the market and the most slamfiring primer in Garands/M1a are Federals. Avoid other sensitive primers such as "benchrest" primers. They are not appropriate for this mechanism.
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Old February 4, 2013, 12:58 PM   #7
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yep, nicely done Slamfire. Save that neck sizer for the bolt actions GA
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Old February 4, 2013, 05:56 PM   #8
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Excellent advice. Thanks.

I'm somewhat meticulous with my .308 reloads for this rifle, though I have some room to improve. To date I have dropped every case into an L.E. Wilson gauge to check the length and headspace. I do this after I resize them, and then again after I load them. I trim any long cases, ream and clean every primer pocket, and check to ensure the CCI primers I seat by hand are seated properly. I have been using a standard base RCBS FLSD. Have had one incident. Squeezed a round off and the rifle fired twice--sort of like a bump fire. Never had a slam fire when releasing the bolt to strip a round out of the magazine.
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Old February 4, 2013, 11:01 PM   #9
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Believe Slamfire... You'll shoot your eye out kid...

I use a small base sizing die and CCI #34 primers for my Garand loads (free floating firing pin, just like yours).
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Old February 5, 2013, 10:20 AM   #10
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I really think small base dies are a safety critical issue for Garands/M1a's and even M1 carbines.

Standard sizing dies sometimes do not always reduce a case enough to drop in the chamber.

Gene Barnett cut me this reamer cut gage. He also cut me a 30-06 reamer cut gage. These gages are exact duplicates of the chambers of the match rifle barrels he cut as he used the same chambering reamer to cut these gages.

Wilson gages are excellent for their purpose: to measure length from shoulder to base. Wilson gages are cut large between the shoulders so that you can drop a fired case into the gage and get a very good idea of the headspace of a bolt action. It does not work for a gas gun, because cases are stretched during extraction in a gas gun. But, the limitation of these gages is that they don’t measure “fatness”.

The reamer cut gage will display “fatness”.

Range pickup cases unsized. One falls into Wilson gage, as expected, the other will not drop into reamer cut gage.






Case sized in Lee Die


Lee Die sized case does not drop into reamer cut gage.

Small based sized (actually sized in an RCBS small base die) drops all the way int.


I also bought reamer cut gages from Compass Lake Engineering http://www.compasslake.com/. Frank has a number of barrel stubs that he will cut with a chambering reamer to make you a reamer cut gage.

I will say that most of my range pickup cases dropped into the reamer cut gage after sizing in the Lee die, but you will run across fat cases in range pickups or once fired military cases.

But to continue pounding on this subject, but without additional pictures, is something happens when you stuff a bullet in the case. This is something that is not appreciated till you get gages, is there are dimensional changes when you stuff a bullet in the case.

My second out of battery slamfire, occurred with 30-06 cases which were sized in a Bonanza NM sizing die. That die sized cases down more than my RCBS standard but not as much as a small base die. I did not have small base dies at the time. Each of the Bonanza sized cases would drop into the reamer cut gage. But when I reloaded the things with powder and ball, and tested them by dropping them into the reamer cut gage, rounds stopped basically at the location you see in with the standard based sized 308. I sort of tossed it off because conventional wisdom was that only high primers and worn receiver bridges caused slamfires. To prevent high primers I had individually reamed each primer pocket to depth and inserted a Federal Match primer by hand and visually inspected each case to see that every primer was well below the case head. I reamed the pockets to an excessive depth, probably 0.006 to 0.008” below the case head in the errant belief that if high is bad, then really low must be good. Events showed the fallacy of that theory. I was sighting a new NM Garand with a new Barnett barrel. The receiver was cherry and the parts were virtually new in the box GI. That Garand slamfired out of battery, from the clip, and blew the back of the receiver heel into my face, busting my shooting glasses and cutting my cheek.

Except for the receiver, I am still using all the other parts from that rifle, including the trigger mechanism, and winning once a year “Garand” matches with the reconstituted parts. My trigger mechanisms have never followed.

There are a few things that can be learned about this 1) primer sensitivity is always important 2) cases change dimensions after you seat a bullet 3) even a slight interference fit increases the risk of an out of battery slamfire.
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Old February 5, 2013, 12:19 PM   #11
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Slamfire,

Thanks for posting all that documentation. A clear case of a picture being worth 1000 words.
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Old February 5, 2013, 01:17 PM   #12
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Slamfire, kudos and other accolades for your posts on sizing stuff.

And also two attaboys to you for showing the Wilson .308 Win. and reamer cut case gauges. Both made me think of the Wilson chamber type hand seating die I've had for decades. They made me think of another use for any rimless bottleneck case gauge that's reamed to SAAMI or some other chamber spec that lets one see how the mouth fits the front of them.

Take a new or fired case that's been neck or full length sized, then put it in the gauge. Press the case all the way in then look at the case mouth relative to its clearance to the gauge's chamber neck. That shows how well aligned the case is in the "chamber" when it's smacked by the firing pin. If you use an 8X or 10X loupe to magnify it, it helps. A loupe with a measuring scale in thousandths will show how uniform the space is around the case mouth. This shows how well your loaded rounds will fit the chamber when they're fired. It also shows, if you gently push the case in with both held horizonatlly, how the case rests in the bottom of the chamber until it's all the way in when the case neck/mouth centers in the chamber neck/mouth. And moving the back end of the case around doesn't significantly change the case neck's position in the chamber.

All of which may help folks understand why full length sizing fired rimless bottleneck cases shoot so darned accurate.
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Old February 5, 2013, 02:37 PM   #13
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Quote:
Slamfire,

Thanks for posting all that documentation. A clear case of a picture being worth 1000 words.

Quote:
Slamfire, kudos and other accolades for your posts on sizing stuff
Shucks, folks, I'm speechless
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Old February 5, 2013, 04:35 PM   #14
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That's OK. Just don't go postless on us.
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Old February 5, 2013, 11:35 PM   #15
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Wyobohunter, I'll take being called a "kid" as a compliment. Been slinging lead for about 40 years now. Frankly I feel old some times when I look in the mirror. Anyway, definitely great info and advice from Slamfire and Bart. Very helpful pics! I have a sweet M1A parked under Swarovski glass and want to keep both the way they are. I'll be changing a few things on the reloading bench. Tango1niner, yes, the gauge was clean. Many thanks, all.
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Old February 6, 2013, 09:36 AM   #16
F. Guffey
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Question on Neck Sizing .308 for M1A

--------------------------------------------------------------------------------

I recently purchased an RCBS neck sizing die for .308 I shoot from my Springfield M1A (Loaded version). Neck sized some recently fired brass this evening and then dropped it into an L.E. Wilson headspace gauge. Noticed it sat a bit high in the gauge and checked closer with my micrometer and found that the neck sized brass was on average .004 high (from top of where it's measured from the guage). Is that a problem? Does it mean that headspace in my chamber is a bit over spec? I assume that the L.E. Wilson gauge is at industry spec. I'm loading 168gr Sierra HPBTs over about a 90 percent of max charge in Winchester brass. Does something I'm doing, or what I'm shooting, rule out neck sizing? For this particular rifle, I've always FL sized in the past. No issues. Fairly good accuracy. Thought neck sizing would allow me to tighten up my groups a bit.

Thanks...



.004” above the gage, later the question is “Is that a problem?” Next time measure the length of the case from the datum/shoulder of the case ‘to above the gage’ before firing, measure the length of the case from the datum/shoulder to the head of the case (above the gage) before neck sizing. The Wilson case gage allows for measuring the length of the case from the datum/shoulder to the head of the case on new minimum length/full length sized cases and fired cases, and as always the Wilson case gage will allow for measuring the length of the case from the shoulder of the case back to the head of the case and from the shoulder forward to the end of the neck.

Fat cases are fired cases, fat fired cases can be dropped into a Wilson case gage. The other gage is similar to a chamber gage, fat cases can not be dropped into a chamber gage.

Chamber gage, case head protrusion and the smith made me a case gage for my new rifle he built, if the smith made a chamber gage for a rifle he built he would have matched ‘case head protrusion’, instead he made a case gage for full length sized/minimum length cases. Then there is the ‘tomato stake barrel’, material? Most barrels have enough metal in them to make 3 chamber gages.

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Old February 6, 2013, 10:40 AM   #17
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Dan Newberry, as you are aware there is chamber length and case length (from the head of the case to the shoulder/datum). The .004” above the gage should be the effect the chamber had on the case when the case was fired, ‘not a problem?’ The .004” reading above the Wilson case gage is just right in there for nice to know if the rleoader did not measure the length of the case before pulling the trigger, meaning he does not know if the case head was dead on and level with the gage, below or above, back to “nice to know”,

I determine the length of the chamber before firing, when I measure the length of a case from shoulder/datum to the head of the case, after firing there are no surprises, do I have a Wilson case gage for every chamber I load for? No, once a reloader understands datums the reloader can purchase datums, make datums and collect datums.

Barrel stubs? I took a few to the last gun show at Market Hall in Dallas, I also took 10 +/- barrels, no one recognized the stubs as gages complete with case head protrusion.

“I don't think .004" is out of spec, if I'm understanding you correctly. I believe the no-go gauge won't chamber until you get to .006" over SAMMI spec. And that's just the no-go... the field gauge is going to give you a bit more than that, so I believe your chamber is fine”

In the perfect world his minimum length cases would have been perfectly? lever with the top of the gage, the .004” above the gage after firing (after neck sizing) would indicate the effect the chamber had on the case when fired. Sizing the case back to minimum length/full length size would be a matter of shortening the case from the shoulder of the case to the head of the case .004”, most reloaders would choose to bump the shoulder back .004”, When I try that part of the case body becomes part of the shoulder and part of the shoulder becomes part of the neck and when I bump the shoulder back without case body support the case body increases in diameter.

SAAMI

http://www.saami.org/PubResources/CC...Winchester.pdf

1.630 chamber from the datum to bolt face MINIMUM! MAXIMUM, add .010” The case length from the datum/shoulder 1.634 minus .007. Maximum Cartridge/Minimum Chamber, again, I determine the length of the chamber from the datum/shoulder to the bolt face, because I am a reloader with dies and presses with threads I off set the length of the chamber with the length of the case from the shoulder back to the head of the case.

And notice SAAMI does not designate case length as having head space, I guess it is optional.

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Old February 6, 2013, 06:34 PM   #18
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Quote:
Originally Posted by GunAddict1962 View Post
Wyobohunter, I'll take being called a "kid" as a compliment. Been slinging lead for about 40 years now. Frankly I feel old some times when I look in the mirror.
The kid thing wasn't really meant as a reference to your age or experience. It's just a movie quote.

Go to YouTube and look up "you'll shoot your eye out kid"

Then watch the whole movie (if you haven't already) it's hilarious.

Anyhow, thanks for not taking offense, none was meant.

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Old February 13, 2013, 12:23 AM   #19
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No offense taken, Wyobohunter. Thanks for the explanation. I always try to look through perceived tone to the facts and information. Gun/shooting/ reloading aficianodas are some of the most informed, friendliest, and helpful folks around. Since there is a degree of risk involved in anything that goes "boom," the practical benefit of forums like this one is immeasurable. My M1A is one of my favorite guns. I want to be sure and feed it top quality reloaded ammo. I'll stick with neck sizing on my bolt guns.
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Old February 13, 2013, 12:24 PM   #20
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GunAddict, I think your bolt guns would benefit from full length sized cases That's been proved by top level competitors using shoulder fired rifles since the 1950's in most disciplines and the benchresters pretty much all moved away from neck sizing to full length sizing a few years ago.

Most folks who neck size think cases so sized fit the chamber better and align the bullet more concentric to the bore. They don't; especially when they've been fired a few times.
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Old February 13, 2013, 01:20 PM   #21
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Yep. The brass spring-back from filling the chamber is uneven if the brass isn't dead perfectly symmetrical throughout (virtually never). So it's better to size enough to get clearance around the sides, and set the shoulder back just a thousandth or so to allow the taper of the shoulder to self-center the case neck in the chamber neck.
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Old February 13, 2013, 09:36 PM   #22
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I'm staying out of this...

I think the correct answer is actually "it depends".
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Old February 14, 2013, 08:14 AM   #23
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wyobohunter, exactly what does it depend on? You may have a good point of view and many would benefit from knowing what it is. You jumped into this conversation and that's fine by me, so you're not staying out of it.

F. Guffey, you mention that there is chamber length and case length (from the head of the case to the shoulder/datum). Chamber length typically refers to the distance from the breech face to chamber mouth; it's 2.025" for the .308. Case length's the distance from case head to case mouth; SAAMI specs show that at 2.015" -.020". Chamber "headspace" (as well as case headspace) is what the ammo industry and reloaders refer to as the head-to-datum length; one for the chamber and another for the case. I think you're getting length and headspace terms mixed up.
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Old February 14, 2013, 11:50 AM   #24
F. Guffey
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I think you're getting length and headspace terms mixed up.




http://www.saami.org/PubResources/CC...Winchester.pdf

1.630 chamber from the datum to bolt face MINIMUM! MAXIMUM, add .010” The case length from the datum/shoulder 1.634 minus .007. Maximum Cartridge/Minimum Chamber, again, I determine the length of the chamber from the datum/shoulder to the bolt face, because I am a reloader with dies and presses with threads I off set the length of the chamber with the length of the case from the shoulder back to the head of the case.

And notice SAAMI does not designate case length as having head space, I guess it is optional”

Bart B. I know you can read, I have no ideal what your motive is for ignoring information. That leaves me to wonder if you are that desperate for attention.

“Chamber "headspace" (as well as case headspace) is what the ammo industry and reloaders refer to as the head-to-datum length;” I included a link from SAAMI, nothing about head space and the case, only length.

It is not the industry that has the problem, it is the reloader, memory work is nice as in “Repeat after me, Head space is etc., etc..” After repeating “Head space is etc., etc..” a reloader can not size a case to off set the length of the chamber from the usual places as in from the head of the case to the shoulder and from the bolt face to the shoulder of the chamber.

Without the ammo industry and SAAMI information I determine the length of the chamber from the bolt face to the shoulder of the chamber, I use the direct route, my route skips the ‘talking about it’, my method/technique is about doing it.

After you have already declared the case has head space you have no choice but to insist it does. I do not preach head space, I do not insist a reloader understand datum is ‘measured from’, a boring conversation in the real world starts with “Head space is...etc..” In the real world I have never found anyone explaining ‘head space’ that knew what they were talking about. Getting a reloader to measure the length of the case from the shoulder/datum back to the head of the case is as difficult to get them to understand a minimum case length from the shoulder to the head of the case and full length sizing is returning the case to minimum length. Point? The new factory case has a length that can be measured from the shoulder of the case to the head of the case.

You preach full length sizing as being the only way to go, I disagree, there has been a number of manufactures take liberties with “repeat after me etc..” They built gages designed for measuring the length of the case from the datum/shoulder to the head of the case, then! declared their tools were head space gages, one, when asked about his self declared head space gage many times got to the point he could not ignore the critic, he said ‘I know, but I am not the only one, so, I named it a head space gage” ( or something to that effect ), then he continued to call his comparator a head space gage. Even then it should have been understood by the ‘GO TO GUYS’ on forums to make it understood the case length gages were not head space gages, but, it seemed there was more to gain by agreeing with the manufacturer, desperate for attention?

I was approached, it was suggested that the reloading industry would benefit if I agreed with a manufacturer, it was suggested we work together. I up set a few, about that time I made it very clear I did not p$#p products that were only nice but not necessary and mislabeled. I did suggest to anyone that purchased a comparator thinking it was a head space gage and later decided they wanted their money back do so with the understanding they were mislead.

Bart B. you started by declaring the case had a head space, gages that measure case length from the shoulder to the head of the case are case length gages, some are comparators used to measure case length, I make case length gages, again, I collect datums, I make datums and I purchase datums.

In the big inning forums were eat up with a drawing of a case and or chamber, no one knew what it was about but there was an arrow pointing to a line with the line labeled datum line, that was the total amount of information know to a reloader, when finished discussing the topic, the discussion ended with “and that is how they do it”.

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Old February 14, 2013, 02:41 PM   #25
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Slamfire
Sir, would it be possible for you to supply more information regarding this condition? This is a very interesting event.

Could you please photograph:

1. the back of the broken receiver close for us to see the fracture better?

2. the top of the receiver hump showing the manufacturer and serial number?

3. the bolt face of the rifle?

4. the entire top surface of the bolt with another close up of the font on the bolt?

5. the piece of the horseshoe that broke off showing the fracture surface.

6. the fired case that did the deed with close ups of the primer to show the dimple details? As well as other cases fired in same rifle.

7. the magazine area with bolt removed all areas?

8. the bedding of the action.

9. picture of the striker removed from the bolt top and bottom.

10. now this is as stretch , could you get a long vernier caliper and get the measurement from the center line of the gas port to the back of the receiver to 3 decimal places? Also from gas port to front of the receiver.


Could you measure:

1.the inside diameter of the Wilson case gage at the bottom with hopefully a digital caliper or hole mic? I have measured three Wilson case gages for .260, 7/08 and 308 and I get measurements of .4725, .474 and .475. Since the chamber dimensions are called for at .471-.473 range and assuming your Wilson gage measures like mine then every fired 308 case in history should fit in your gage with a .474 or .475 base dimension.

2. the inside diameter of the rifle chamber at the same point? Again this should be .471-.473 range but I have seen fired cases as large as .475 which means they were most likely fired in a .476” chamber.

3. the diameter of the case that did the deed in two orientations .200” up from rim?

4. the diameter of the home made case gage at the lower mouth opening? Making a case gage with a chamber reamer that was used on your rifle is good if you want check your range pick up cases after full length sizing to see if they will go in your chamber. I have seen very few rifles you could pick up brass fired in others and chamber in another.

5. the diameter of the fired case in the case gage in the picture.

6. measure the striker for overall length from striker nose to back of tail. Diameter of striker nose, diameter of the support shoulder immediately to the rear of the striker.

7. how far did the shoulder move forward on firing the suspect case?

8. how did this measurement differ from other cases fired in this rifle?

9. If you have access to a Rockwell tester I would like to know the readings of the receiver in multiple places. For instance starting ¼” from receiver face take readings all the way around the receiver every half inch from front to rear.

10. Same for the bolt, readings on both lugs in all over bolt.
From the loader of the ammo his definition of improperly sized. i.e. case shoulder not set back far enough or shoulder set back too far? Was bolt binding up with the turn in to battery?

11.The load he was using including primer, propellant, bullet, case manufacturer and history i.e. number of loadings etc. Was bullet .308” diameter or?????

12 The length his cases were trimmed to?

13 The FL sized dimension of the case bases measured .200” up from rim.

14The neck dimensions of loaded ammo and fired cases.?

15The bore dimensions of the barrel. Land and groove? Who made the barrel?

16The manufacturer of the reamer? The dimensions of the reamer to correspond with case measured .200” up from rim to include neck dimension.

17Gas port dimension of barrel?

18Manufacturer code of the magazine he was using?

19How much striker nose protrusion from bolt face?
__________________
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President's Hundred (Rifle) US Palma Teams(2)
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Last edited by Hummer70; February 14, 2013 at 03:34 PM.
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