7mm mag nosler brass "grows" by .022 after firing, normal?

[rockwind1]

so as mentioned in previous post, i have a saami spec 7mm rem mag. new nosler brass. loaded up for a ladder test. the mild loads grew by .022 and the higher end loads grew a a little more. i've only loaded for 3 other guns, a 308 and 2 different 6.5 saums so i am wondering if this is normal? my 6.5 saums don't grow at all it seems. anyway, i will do the usual headspace check and probably wind up bumping the shoulders the usual .002-.003. but is there something special about these 7 rem mags? thanks

respectfully and politely not interested in any "your shoulder is not growing" posts.

 

[#40Fan]

Where was this growth measured? Datum or case mouth?

 

[rockwind1]

on datum using hornady "headspace" guage e420 on a mitutoyo caliper with that little hornady base that the head sits on. i have measured a lot of cases, i checked all of the 30 or so fired cases. the new nosler measures 4.259 and the fired measures 4.280. the heavy load cases measure 4.281 ish.

edited: i typed a 9 instead of an 8 so i fixed it,,, they are growing about .021

 

[#40Fan]

That is quite a bit of growth. .030" is a lot. Keep a look out for case head separation.

 

[rockwind1]

so the overall length of the case grows from 2.489 to 2.494 so the case is growing .005.

the necks went from .309 to .312 loaded and after fired they are .315.

i see no evidence of head seperation

 

[#40Fan]

I see you edited your post, but your measurements are telling you the right answer. You're getting .021" of shoulder movement.

Might not see any signs right now, just something to keep an eye on.

 

[Dusty Stevens]

They are headspaced off the belt. All belted magnum nosler brass ive ever gotten was extremely short to the shoulder. Gotta match every reamer- im betting the base to belt is perfect and within specs very consistently.

 

[rockwind1]

They are headspaced off the belt. All belted magnum nosler brass ive ever gotten was extremely short to the shoulder. Gotta match every reamer- im betting the base to belt is perfect and within specs very consistently.

so this is fairly normal? that much shoulder growing is ok and just keep an eye on case head seperation?

 

[fguffey]

respectfully and politely not interested in any "your shoulder is not growing" posts.

so this is fairly normal? that much shoulder growing is ok and just keep an eye on case head separation?

i will do the usual headspace check and probably wind up bumping the shoulders the usual .002-.003. but is there something special about these 7 rem mags? thanks

Nothing special about the 7MM Remington mag; is there something about the events that happen between pulling the trigger and the bullet leaving the case that reloaders do not understand? That answer is yes;

the new nosler measures

4.259 and the fired measures 4.280. the heavy load cases measure 4.281 ish

. If you are measuring the case length what is 'ish'.

The Hornady tool is a comparator; the reason for that is the datum, Hornady placed a radius on the datum meaning you will have to learn to verify the Sinclair/Hornady tool before you can use it as a case length gage. I understand you called it a head space gage but the case does not have head space. The diameter of the datum for the 7MM Remington Mag is .410. Reloaders like case friendly datums, I don't, I want a sharp edge on my datums. The sharp edge on the datum means I do not have to verify my gage.

Are you feeding the 4 inch + length cases one at a time; when forming cases to a chamber I have used an arbor press. The length of the 7MM Remington case is 2.500", A reloader will measure before firing and again after firing. I understand that is complicated but you decided to exclude the very few reloaders that could help you.

F. Guffey

 

[#40Fan]

 

[fguffey]

Where was this growth measured? Datum or case mouth?

Where is the growth? I noticed you are throwing the term 'datum' around as thought it came to you as an epiphany; or a sudden insight or intuitive understanding. It was not that long ago reloaders described the datum as a line. You will not believe how tacky reloaders got when I explained to them the datum was a round hole/circle. It drove them to the curb when I tried to convince them they could make datums, all they had to have was a drill and drill bit and be able to drill a straight hole.

Are you that desperate for attention?

F. Guffey

 

[spife7980]

Where is the growth? I noticed you are throwing the term 'datum' around as thought it came to you as an epiphany; or a sudden insight or intuitive understanding. It was not that long ago reloaders described the datum as a line. You will not believe how tacky reloaders got when I explained to them the datum was a round hole/circle. It drove them to the curb when I tried to convince them they could make datums, all they had to have was a drill and drill bit and be able to drill a straight hole.

Are you that desperate for attention?

F. Guffey

God youre an ass. Im already ready to leave the site again after one thread.

 

[#40Fan]

I think he needs to crawl back up his datum.

 

[fguffey]

I think he needs to crawl back up his datum.

I am not impressed with your use of the datum term, as I said before I was going to be the only member that could sort this out. Tell me again about the datum.

F. Guffey

 

[M-61]

bumping the shoulders the usual .002-.003. but is there something special about these 7 rem mags? thanks

Here's my take. The first or two shots is using the belt for the headspace. The shoulder then does the headspacing once it reaches the chamber neck datum, it is the same as in any non belted case. By "BUMPING" the shoulder back the usual .002-.003 you will be allowing the case to grow. It will grow until it separates. (.002-.003 per shot)
Probably not the best explanation.

 

[Uncle Ed]

Rimmed and belted case design dates back to a time when case manufacturing tolerances were not what they are today. And in essence the shape of the case in front of the rim or belt did not matter much.

Below two .577/450 Martini cases, and on the left a modern made case and on the right a case from 1879 with a F. Guffey datum point. (old misplaced and very wrinkled)

The belted case is a British design dating back to when a inch was so many grains of wheat, so many grains of barley, or so many kernels of corn etc. So do not despair over shoulder height, everyone knows as they get older they get a little shorter.

Bottom line, anyone who read Jack O'Connor stories knows the .270 Winchester is the worlds best non-belted magnum.

P.S. you could go a little bigger and have your rifle rechambered to 280 Ackley Improved.

Below the .280 Ackley improved and his retarded grain fed cousin the 7mm rem mag.

 

[Dusty Stevens]

You will not believe how tacky reloaders got when I explained to them the datum was a round hole/circle.

F. Guffey

I missed where you explained it. Can you tell us again?

 

[#40Fan]

I missed where you explained it. Can you tell us again?

NOOOOOOOO!!! Don't encourage the (fill in the blank with your choice of words).

 

[Uncle Ed]

I missed where you explained it. Can you tell us again?

Dusty, did you ever see a sign that says "Don't Feed the Animals"

If your looking for a fun "datum" I can send you her phone number.

 

[Mark204]

as I said before I was going to be the only member that could sort this out.

F. Guffey

.......And as usual we'll walk away more confused after you "sort" it out for us.


Mark