0.020 Headspace difference between 2 rifles

[Deleted member 46119]

Both chambered in 300Wby

Custom
1987 Fibermark

I won't be sharing brass between the two just wondering if anyone else has encountered this much difference.

 

[Lefty7mmstw]

.015" roughly between my old 7stw and my current one.... had to reset the dies for the new rifle to keep the brass growth to tolerable levels. My two 270win's have almost the exact chamber dimensions and throat, and they are different brands: one tikka and one marlin.

 

[Deleted member 46119]

Moments after I posted some added in a different thread that this is not that uncommon in belted case chamberings.

I don't see more than .005 from chamber to chamber in non-belted cases.

I have access to at least 2 of everything I load. Mine or my friends.

 

[shortgrass]

SAAMI shows the 7mm STW head space to be .220" min. - .227" max. and the .300 Weatherby .220" min. - .224"max. Somebody has something way out of spec or you are calling another dimention "headspace" when it is not. Headspace on all belted magnums is measured from the bolt face to the front of the belt. www.saami.org for published dimentions (industry standards).

 

[WAMBO]

If the OP is referring to the bolt face to shoulder dimension as head space like a non belted cartridge I have a factory Win M70 in 338 Winmag that blows new brass forward at the shoulder .028" when fired so maybe it is a matter of varying reamer dimensions.

 

[shortgrass]

There's no "datum line" on the shoulder to measure from. Your talking about "making the brass fit the chamber, not headspace. Go to the SAAMI web site and you can see for yourself the tolerances allowed from the bolt face to the top of the shoulder or the neck/shoulder junction. Confusion abounds as it is, using one term to describe another only adds to the confusion.

 

[Lefty7mmstw]

There's no "datum line" on the shoulder to measure from. Your talking about "making the brass fit the chamber, not headspace. Go to the SAAMI web site and you can see for yourself the tolerances allowed from the bolt face to the top of the shoulder or the neck/shoulder junction. Confusion abounds as it is, using one term to describe another only adds to the confusion.

I'm sure the reason his nomenclature is off is he uses the shoulder to headspace from on a belted and forgets the primary headspace is the belt as do 90 percent+ of reloaders do.
Yes, we are aware that a belted chambering is set to the belt for headspace, but the chamber reamer maker is often generous and leaves the shoulder dimension a bit long ( often so the reamer can be re-sharpened after it wears) and that is a serious problem for anyone who actually wants some life from their brass and accuracy from their rifle. To not be worried about your case dimensions on a belted other than the belt is silly. To be worried about nomenclature is fine, but please do not mistake a terminology issue as ignorance.

 

[shortgrass]

My concern is the treminology. How many visit these forums, who are new to shooting and reloading, who really don't understand. I'd bet that the number 90% is nowhere close who understand making the brass fit the chamber and rely on what theyve read somewhere, be it right or worng. I may not give the number to be 50%. How many do you figure visit these forums and never ask a question or post at all? The answer,,,, lots of 'um! Until you run a shop and meet the pubic you really won't know how many come thru the door just full of misinformation or can't explain the difference between extraction and ejection, let alone headspace. There's a reason the web has become known as "the misinformation super hi-way".

 

[davkrat]

What's the danger in the misunderstanding of the terminology for the average shooter in this instance? 99.999999% of those shooters are never going to do anything on earth that can effect the headspacing of a rifle. If anything the belt of a magnum makes it even safer as you couple routinely crush the hell out of a shoulder with no worry of head separation after a few firings. Your brass might be toasted after one or two reloads but the belt should keep the heads connected.

To the OP I have loaded for a couple 7MM Rem MAgs and it was not uncommon for there to be some variance. Two Remington barrels built 20 years apart had quite a bit of difference and bumped shouldered reloads could not be swapped between them. It sounds like your chambers are within the range of compounding tolerances. One gun on the long side and the other on the short side.

 

[Deleted member 46119]

'Shortgrass', I'm sorry I used technically incorrect terminology with respects to belted magnums. I don't think I 'added to the confusion' it exists and will continue to exist.

It's ok that you don't know my history with respects to 'the internet' as a 'mis' information source and that you don't know my history with firearms. I don't know yours.

I have not "worked" in the shops but as the years go on I spend so much time there and on a range that sees over 500 shooters per weekend where I am now past president that my experience with 'customers' contains the 'idiot incidents' that yours does. I've had the barrel of a firearm containing a live round pointed at my face with the "it won't open" comment while the 'customer' tries to work the action with the muzzle still pointed at my face. "Oh it's empty" pistols pointed at my crotch that fired without being reloaded. Hmmm. Makes you wonder.

It's a shame that 'Shortgrass' has so much information lost in an aggressive pedantic presentation.

We have now wasted significant cycles, bytes and bandwidth on the discussing terminology rather than sharing experiences that can educate me and future readers of this thread.

 

[Deleted member 46119]

So with 'Shortgrass's help in understanding that the measurement I made has no definition within SAMMI and knowing that the SAAMI approval for the 300 Weatherby Magnum was never issued.lightbulb

There is a .020 difference in base of the cases to the point on the shoulder I used a reference between 2 rifles chambered in 300 Weatherby Magnum. Gee wiz, that sounds clear as mud, though it doesn't violate the technical use of terminology 'head space' for belted case designs. Non-belted case designs, well, that sure adds to the confusion.

Anyway, I never would have expected such a huge difference between rifles.

1) I know not to resize cases from different rifles to the same specification.
2) I know that resizing to 'fit the chamber' for belted magnums works better for me.
3) I know that the portion of the cases that is within the SAAMI specifications and used as 'head space' with belted cases is within published data for the 300 Weatherby Magnum. Even if not SAAMI approved.
4) I know that the 2 270 Weatherby Magnum rifles I load for, both Weatherby branded Mark V models have .002 or less using the same referencing format, between fired cases.

and now

I guess, from 'Shortgrass's explaination that, that much difference in belted magnums is fine because that is not the chambering reference point. Though I'm not sure as there was so much discussion of 'being concerned with terminology' if that is correct.

Oh well, being pedantic doesn't always transfer the understanding to the recipient. I know I have that problem plenty of the time.

 

[Edd]

If you would have looked at the SAAMi specs you would have seen that there is a reference point and that the tolerance is .008". So if you are measuring to that point and getting .020" difference, one or both of your chambers are out of spec. The significance of correct terminology is important because now you have to determine if there is a headspace issue or an issue between the headspace and the shoulder.

 

[Deleted member 46119]

If you would have looked at the SAAMi specs you would have seen that there is a reference point and that the tolerance is .008". So if you are measuring to that point and getting .020" difference, one or both of your chambers are out of spec. The significance of correct terminology is important because now you have to determine if there is a headspace issue or an issue between the headspace and the shoulder.

I'm sorry if I misunderstand your intent but From my view point your answer contains some useful information but is worded like"you stupid or lazy person" read the spec.

Forgive me if that was not your intention. Typed words have no tonal inflection. 'Tone' of the written word is very difficult to master. If it were easy everyone would write beautiful novels and we would all be bored of others writings. Additionally starting any "advice" with "you should" is IMHO condescending if you fail to provide the "how to" portion of the advice.

I get the "significance of correct terminology", keep beating the horse, it's dead but keep beating it anyway.

BTW: respectfully and sincerly, to me, reference point and datum are usually the same thing so your statement seems to be in conflict with 'Shortgrass's. Would it be possible for you to clarify this, provide a reference to the terminology or just make the statement that it has to be "learned" where the terminology is the same but the meaning is very different between belted case designs and non-belted case designs

Please point me to the SAAMI spec for 300 Weatherby Magnum. The TOC says "not issued" and (Laugh please) I'm too lazy or stupid to find it on my own.

 

[Deleted member 46119]

Oh and none of the discussions of correct terminology address the original question.

Has "anyone else has encountered this much difference"?

Quite happy to continue to discuss the terminology though as I am learning new things.