Help with case length on 7mm Rem Mag

[Kurt82]

I think I screwed up! This is only my second round of reloading from start to finish. I guess I should have resized and then measure my brass after. I measured everything first and my 7mm Rem Mag brass was all below 2.500" and then after I resized them I put primers in all 65 cases. I then remeasured a couple and now about half of them are 2.502"-2.505"! Is this going to be OK or do I have to throw them out. I guess I am confused if the measurement is 2.50" or 2.500" for the max. I feel really stupid. I guess I should be cleaning, resizing, trimming and then primer. I did cleaning, trimming, resizing, priming the first time, but it was only 20rds so somehow got lucky and they stayed under 2.500"

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[pharmseller]

Do they chamber? If so you're fine. I wouldn't worry about .005".

Next time don't full length resize. Get a Lee collet neck sizing die and just resize the neck.

Think about this: SAAMI standardizes cartridge dimensions, so when you resize you're molding the brass back into SAAMI specifications.

Your chamber probably isn't perfectly aligned to SAAMI specifications, so when you fire a case the brass swells to fit your chamber. It springs back a little bit, of course, or else you would be able to extract it, but it now reflects the dimensions of your chamber.

As long as that case is fired only in the same chamber, you shouldn't have to full-length resize. You'll need to reform the neck, hence the neck sizing die, but that's it. After a few firings you'll have to resize and trim (in that order!) but your brass might just last longer since you're not working it so often.

I stopped full length resizing a couple of years ago. I load for multiple people/multiple rifles so keeping the brass separate by rifle is a pain but it's well worth it.

Do some research on neck sizing only.



P

 

[Kurt82]

Do they chamber? If so you're fine. I wouldn't worry about .005".

Next time don't full length resize. Get a Lee collet neck sizing die and just resize the neck.

Think about this: SAAMI standardizes cartridge dimensions, so when you resize you're molding the brass back into SAAMI specifications.

Your chamber probably isn't perfectly aligned to SAAMI specifications, so when you fire a case the brass swells to fit your chamber. It springs back a little bit, of course, or else you would be able to extract it, but it now reflects the dimensions of your chamber.

As long as that case is fired only in the same chamber, you shouldn't have to full-length resize. You'll need to reform the neck, hence the neck sizing die, but that's it. After a few firings you'll have to resize and trim (in that order!) but your brass might just last longer since you're not working it so often.

I stopped full length resizing a couple of years ago. I load for multiple people/multiple rifles so keeping the brass separate by rifle is a pain but it's well worth it.

Do some research on neck sizing only.



P

Awesome! Thanks so much for your help

 

[pharmseller]

I think you have a better opportunity for accuracy by neck sizing only, since the brass is a better fit to the chamber.



P

 

[tac]

'I guess I am confused if the measurement is 2.50" or 2.500" for the max.'

Those are identical measurements. The zero at the end counts for, uh, zero.

tac

 

[DizzyJ]

Are you talking overall length of the brass casing?

If so, you're probably fine, but if you let it grow too long, it'll pinch the end of the case causing potentially catastrophic effects.

 

[DizzyJ]

Also, there are two schools of thought on full length resizing. One is to full length resize every time, just bump the shoulder back .001" -.002" to make sure you're getting enough clearance. This way you're ensuring reliability as far as clambering is concerned.

Neck sizing only is nice, but imperfections in runout and neck thickness can make this method less than desirable. If one wants to cull the brass for these imperfections ahead of time, or turn the necks to achieve the same thing, neck sizing only will yield better results. This is of course a lot more work than most are willing to do.

 

[jordanka16]

Also, there are two schools of thought on full length resizing. One is to full length resize every time, just bump the shoulder back .001" -.002" to make sure you're getting enough clearance. This way you're ensuring reliability as far as clambering is concerned.

This is my preferred way now. All the benefits of neck sizing, none of the drawbacks. You eventually have to size the body on neck sized cases anyway, and doing it this way ensures greater reliability. I size .002 for bolts and .004 for semis.

Full-Length Sizing Die Set-Up — Tip from Sinclair International « Daily Bulletin

 

[tac]

I shoot 7.5x55 Swiss in two rifles, a K11 and K31. The K11 has a 'looser' chamber than the K31, so I FLR each and every case I fire. Being too poor to afford GP11 here in yUK, I'm reduced to reloading in order to shoot the things at all. Here, GP11 costs $105/C and I have a two hundred mile drive to get it.

tac

 

[DizzyJ]

This is my preferred way now. All the benefits of neck sizing, none of the drawbacks. You eventually have to size the body on neck sized cases anyway, and doing it this way ensures greater reliability. I size .002 for bolts and .004 for semis.

Full-Length Sizing Die Set-Up — Tip from Sinclair International « Daily Bulletin

Additionally, if the neck thickness is not 100% equal all the way around, it's (IMO) better to size the mouth from the inside out whether with the expanding ball, or a mandrel. This ensures neck tension that is more consistent from case to case.

Again, if someone wants to take the time to cull the cases for neck thickness or runout, then problem is solved.

OR....

They can neck turn to achieve similar results.

 

[jordanka16]

Additionally, if the neck thickness is not 100% equal all the way around, it's (IMO) better to size the mouth from the inside out whether with the expanding ball, or a mandrel. This ensures neck tension that is more consistent from case to case.

Again, if someone wants to take the time to cull the cases for neck thickness or runout, then problem is solved.

OR....

They can neck turn to achieve similar results.

Unless the necks are only off slightly it's better just to cull them I think. Unless you have a tight neck chamber turning them removes too much material and shortens their lifespan. Buying quality brass solves a lot of issues and frustration.

 

[DizzyJ]

Unless the necks are only off slightly it's better just to cull them I think. Unless you have a tight neck chamber turning them removes too much material and shortens their lifespan. Buying quality brass solves a lot of issues and frustration.

Depends on how much time you have I suppose

 

[awshoot]

'I guess I am confused if the measurement is 2.50" or 2.500" for the max.'

Those are identical measurements. The zero at the end counts for, uh, zero.

tac

Hmmmm ... If I recall my chemistry correctly, the first has three significant digits so it it includes anything less than 2.505" and more than or equal to 2.495" (we can leave out the discussion on randomizing whether to round up or down on 5s) because the non-signifanct digits would round to 2.50 (for example, 2.504 is 2.50"). The second figure has four significant digits, so you'd look at a range <2.5005 and >=2.4995 (for example, 2.5004 = 2.500).

But to the more important question, I agree, if they chamber they chamber and they can be trimmed again next time around. If they don't chamber, the bullet can be pulled and the process restarted. The brass is fine though whichever route is required.

 

[tac]

Hmmmm ... If I recall my chemistry correctly, the first has three significant digits so it it includes anything less than 2.505" and more than or equal to 2.495" (we can leave out the discussion on randomizing whether to round up or down on 5s) because the non-signifanct digits would round to 2.50 (for example, 2.504 is 2.50"). The second figure has four significant digits, so you'd look at a range <2.5005 and >=2.4995 (for example, 2.5004 = 2.500).

But to the more important question, I agree, if they chamber they chamber and they can be trimmed again next time around. If they don't chamber, the bullet can be pulled and the process restarted. The brass is fine though whichever route is required.

I'm sure that you know that you are discussing a difference of +/- half a thousandth of an inch right?

That's precisely twenty times thinner than this line - on my screen.

It is my mathematical opinion that having 'rounded up' neither the hundredths of an inch nor the thousandths of an inch - else that 'rounding up' would have emigrated to the next highest figure - that the posited 0.0005" can be safley ignorated.

tac

 

[awshoot]

I'm sure that you know that you are discussing a difference of +/- half a thousandth of an inch right?

That's precisely twenty times thinner than this line - on my screen.

It is my mathematical opinion that having 'rounded up' neither the hundredths of an inch nor the thousandths of an inch - else that 'rounding up' would have emigrated to the next highest figure - that the posited 0.0005" can be safley ignorated.

tac

I agree with you -- I was just feeling especially pedantic last night for some reason.