7mm rem case size

[slingshot27]

Just getting my self into my first solo run for reloading and was wondering what you guys trim your 7mm rem to? I know max is 2.500" but what is your optimal trim length.


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[Dean2]

Originally Posted by slingshot27

Just getting my self into my first solo run for reloading and was wondering what you guys trim your 7mm rem to? I know max is 2.500" but what is your optimal trim length.


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All suggested trim lengths are .1 shorter than max length on all rifle cartridges. If you neck size after that you probably won't need to trim again for a long time.

[slingshot27]

Originally Posted by Dean2

All suggested trim lengths are .1 shorter than max length on all rifle cartridges. If you neck size after that you probably won't need to trim again for a long time.

The data sheet I found says .020" under. I'm looking to see what everyone finds is the best trim length.


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[Dick284]

As long as you arent over the maximum length. You could simply trim to just that length.

As long as you're consistent with the length, who gives a hoot.

[elkhunter11]

I trim to .010¨under the max length.

[slingshot27]

Originally Posted by elkhunter11

I trim to .010¨under the max length.

How many rounds does that last you before you have to trim again. Or do you trim to .010 under each round.


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[Dean2]

Slingshot27 The data sheet I found says .020" under. I'm looking to see what everyone finds is the best trim length.

Sorry, missed a zero, should have said .010 short of max. I measure the max case length on my guns and trim to .010 shorter than that. A lot of chambers have case lengths quite a bit longer than what the books say, a few are shorter.

[Dick284]

Originally Posted by slingshot27

How many rounds does that last you before you have to trim again. Or do you trim to .010 under each round.


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Always trim to the same length, 10 thou under, 5 thou under, or max length, it doesn't matter, just go for the same length every time. Write your trim length down, then set your calipers for that value, a simple pass of the cases through the calipers will seperate the ones that need trimming from the ones that don't.

How often is dependant on the load, and how much you work your brass through sizing.

[slingshot27]

Originally Posted by Dean2

Sorry, missed a zero, should have said .010 short of max. I measure the max case length on my guns and trim to .010 shorter than that. A lot of chambers have case lengths quite a bit longer than what the books say, a few are shorter.

My friends showed me the website for all the case sizes and max and mins for cases and barrels. Thanks for the sizing info.


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[elkhunter11]

Originally Posted by slingshot27

How many rounds does that last you before you have to trim again. Or do you trim to .010 under each round.


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That depends greatly on the cartridge, and the load. With my smaller cases with steeper shoulders, I usually go five firings or more without trimming, and for the large capacity magnums, usually every third firing or so.

[qwert]

Originally Posted by Dean2

Sorry, missed a zero, should have said .010 short of max. I measure the max case length on my guns and trim to .010 shorter than that. A lot of chambers have case lengths quite a bit longer than what the books say, a few are shorter.

Some suggest ~.004-.005 is sufficient case to chamber length clearance.
Personally I like a little more margin for safety and do exactly what Dean2 does,

IMHE, all the new or fired cases I have measured are much shorter than required. I just trim each 50 case batch to a uniform length during initial case prep, and let them grow as they wish until .01 under actual measured chamber length.

I suspect most loaders are trimming excessively, especially those with motorized trim units.

Good Luck, YMMV.

[slingshot27]

Thanks everyone. I brought all my casings to .010" under. I'd say about 10% were a little more but that should correct its self next round.


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[qwert]

Originally Posted by slingshot27

Thanks everyone. I brought all my casings to .010" under. I'd say about 10% were a little more but that should correct its self next round.

Do you mean .010 under your individual rifle actual measured chamber length, or the SAAMI spec length as found in most reloading manuals?

Many trim cutter gauges (Lee) and I suspect fixed GO gauges, are made intentionally shorter than SAAMI minimum spec, (I suspect for legal liability caution). This causes many loaders to trim too short (which is certainly better than too long), and the same caution causes many rifle manufacturers to cut their chambers to SAAMI maximum chamber spec or longer.

If re-loading cartridges for use in several or any rifles, it is advisable to FL size and trim to SAAMI spec,
but if hand-loading for use only in an individual rifle, then custom sizing and trimming for best fit in that individual chamber, is better IMHO.

A case that is too long for a chamber will contact the end of the chamber neck at the junction of the throat (I hope I have my terminology correct), when the bolt is closed, the lug ramps will cause the edge of the case mouth to crimp into the bullet solidly and will not provide any clearance for the neck to expand and release the bullet on firing. This can cause a serious over-pressure spike and other effects best avoided.

As Dean2 mentioned some chambers can be cut to shorter than SAAMI spec.
The only way for a hand-loader to know the best or safest trim length is to measure the individual chamber using a simple chamber length tool, which can be easily made from a fired case and a bullet. I have posted links to articles on tool fabrication and to the (IMHO better) Sinclair tool on this forum previously, a search will find them.

Good Luck, YMMV.

[slingshot27]

Originally Posted by qwert

Do you mean .010 under your individual rifle actual measured chamber length, or the SAAMI spec length as found in most reloading manuals?



Many trim cutter gauges (Lee) and I suspect fixed GO gauges, are made intentionally shorter than SAAMI minimum spec, (I suspect for legal liability caution). This causes many loaders to trim too short (which is certainly better than too long), and the same caution causes many rifle manufacturers to cut their chambers to SAAMI maximum chamber spec or longer.



If re-loading cartridges for use in several or any rifles, it is advisable to FL size and trim to SAAMI spec,

but if hand-loading for use only in an individual rifle, then custom sizing and trimming for best fit in that individual chamber, is better IMHO.



A case that is too long for a chamber will contact the end of the chamber neck at the junction of the throat (I hope I have my terminology correct), when the bolt is closed, the lug ramps will cause the edge of the case mouth to crimp into the bullet solidly and will not provide any clearance for the neck to expand and release the bullet on firing. This can cause a serious over-pressure spike and other effects best avoided.



As Dean2 mentioned some chambers can be cut to shorter than SAAMI spec.

The only way for a hand-loader to know the best or safest trim length is to measure the individual chamber using a simple chamber length tool, which can be easily made from a fired case and a bullet. I have posted links to articles on tool fabrication and to the (IMHO better) Sinclair tool on this forum previously, a search will find them.



Good Luck, YMMV.

I went .010 under the spec. That would be a royal pain the the ass to trim each one .010 under they're individual sizes.
Thank you for the info.


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[qwert]

Originally Posted by slingshot27

I went .010 under the spec. That would be a royal pain the the ass to trim each one .010 under they're individual sizes.

I did not consider that a likely possibility.

If you mean the reloading manual spec, I suspect what you have done is to trim to .010" under SAAMI minimum case spec.

I do not apologize for my pedantry, correct terminology and usage is essential when discussing a 60,000 PSI explosion inches away from your eyes.

Have you downloaded the SAAMI cartridge and chamber spec drawing?
If not, I respectfully suggest you Google it.

Good Luck, YMMV.

[slingshot27]

Originally Posted by qwert

I did not consider that a likely possibility.



If you mean the reloading manual spec, I suspect what you have done is to trim to .010" under SAAMI minimum case spec.



I do not apologize for my pedantry, correct terminology and usage is essential when discussing a 60,000 PSI explosion inches away from your eyes.



Have you downloaded the SAAMI cartridge and chamber spec drawing?

If not, I respectfully suggest you Google it.



Good Luck, YMMV.

Not to worry I did already. Case max 2.5 my trim 2.490


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[qwert]

Originally Posted by slingshot27

Not to worry I did already. Case max 2.5 my trim 2.490

IMHO, The actual SAAMI (or CIP) spec drawing is a better authority than any reloading manual.

I now suggest you measure your actual chamber and compare with the SAAMI chamber spec drawing.

You can choose to trim to any length, actually measuring your chamber makes it an informed choice.

Good Luck, YMMV.

[slingshot27]

Originally Posted by qwert

IMHO, The actual SAAMI (or CIP) spec drawing is a better authority than any reloading manual.



I now suggest you measure your actual chamber and compare with the SAAMI chamber spec drawing.



You can choose to trim to any length, actually measuring your chamber makes it an informed choice.



Good Luck, YMMV.

Never thought Of measuring my chamber depth. How would you go about that and how much off that depth would you go.
This also seems like the beginnings of making more precision for each round.


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[slingshot27]

With all this new info raises another question I have for y'all. What would be considered excessive case stretch between loads. I know it can show signs of either high pressure loads or of cases reaching the end of their life.


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[petew]

I trim to the length that little rod in the Lee case trimmer makes them. I have been doing that for many, many years and it seems to work just fine.

I always check the actual length when a new caliber is first done to make sure it is short enough and never worry again.

I don't plan on entering bench rest competitions and such , so I full length resize, and trim whenever I load .

It works just fine.

[Mattzlaff]

I've been waiting for almost 2 weeks to get some powder from cabelas and in that time I sized and trimmed my brass.

I went to 2.490 for length.

I have seated a bullet and set it to a 3.290 OACL with no powder/primer, chambered it in the gun from the magazine and everything is smooth.

is there anything wrong with that, besides having a dummy cartridge? The nosler manual said they use 2.5" case length and 3.290" OACL. I plan on loading 150Gr nosler partitions with IMR 4350 powder starting at the minimum load.