Trimmed case length

[10mm4ever]

I've tried searching this with no luck, what do you guys trim your brass to, I know .992 is max. none of my brass is at .992 but it is all over the map. So what would you consider the minimum to still get good head spacing. I have been reloading 10mm a long time my brass has never stretched to .992 so I have trimmed it, but I am going to load some hot stuff for the first time and I thought I might want to start with a uniform length of brass. Thanks

[TXCOONDOG]

The only cases I trim are cases that I roll crimp (.357 and 44 mag) for consistency.

Hornady 9th Edition
10mm Auto
Max: .992"
Trim: .987"

I've never had any cases over or under the aforementioned lengths out the 5 years or so reloading for the 10mm.

[TXCOONDOG]

Forgot to mention, that I have went well above reloading data to meet SwampFox and Bufflo Bore velocities.  I have sorted lengths (new brass) within .001" and found no difference in FPS, ES or SD and/or accurancy.

Even with casting my own boolits, I only expand the case enough to seat the boolits without shaving them and use only enough crimp to remove the flare/ bell of the case for reliable feeding and never ran into any issues with the case lengths.

When I reload plated or jacketed bullets, I only expand the case enough to get the bullet started in the case and found that I don't need to crimp at all.

Good Luck with whatever you decide 

[Pablo]

I've never trimmed a 10mm case. Truth. Never had one exceed spec.

[The_Shadow]

With most straight wall semi auto cases they tend to get shorter, where cartridges like 357 and 44 using heavy roll crimps do stretch a little from the crimp pulling when fired.

Bottle neck casings do stretch down in the lower web section, the resizing pushes the tapered neck area back and lengthening the case. 
This is due to loose chamber fitment of the cartridge being expanded to fill out the chambers when fired. (semi auto mostly) (the bolt action guys use dedicated cases & neck sizing only to reduce over working and stretching)

Here is an example of rifle case stretching

[10mm4ever]

With most straight wall semi auto cases they tend to get shorter, where cartridges like 357 and 44 using heavy roll crimps do stretch a little from the crimp pulling when fired.

Bottle neck casings do stretch down in the lower web section, the resizing pushes the tapered neck area back and lengthening the case. 
This is due to loose chamber fitment of the cartridge being expanded to fill out the chambers when fired. (semi auto mostly) (the bolt action guys use dedicated cases & neck sizing only to reduce over working and stretching)

Here is an example of rifle case stretching

well that explains why I have never had any 10mm brass that I needed to trim. I was wondering if they were all trimmed to the same length might I get a more uniform COAL. My reloads haven't been to bad in the past, but I have never loaded hot in the past.

[The_Shadow]

Here is the SAAMI comparison of the cartridge and chamber specs...



Head Space cut is 0.9920" to 1.0040"  and most casings are way shorter from what I measured...

[10mm4ever]

I have some that measure as low as .977 most are in mid .98s. I have never bought new empty brass does anybody produce in specs brass?

[The_Shadow]

They have been all over the place as new brass, a look through the pull-downs shows that! 

[jazzsax8]

How do we still use the terminology " head-spaces on the case mouth" for any of the pistol calibers?  It would seem that whether it is .005 or .110 it would not make any difference as its really not touching the end of the chamber.  Does this actually apply to pistols other than Glock as we have all read about shooting .40 S&W from a Glock but not a 1911.

[Azrckcrawler]

With most straight wall semi auto cases they tend to get shorter, where cartridges like 357 and 44 using heavy roll crimps do stretch a little from the crimp pulling when fired.

Bottle neck casings do stretch down in the lower web section, the resizing pushes the tapered neck area back and lengthening the case. 
This is due to loose chamber fitment of the cartridge being expanded to fill out the chambers when fired. (semi auto mostly) (the bolt action guys use dedicated cases & neck sizing only to reduce over working and stretching)

Here is an example of rifle case stretching

well that explains why I have never had any 10mm brass that I needed to trim. I was wondering if they were all trimmed to the same length might I get a more uniform COAL. My reloads haven't been to bad in the past, but I have never loaded hot in the past.

I would think the only way to get stretched 10mm brass is if the timing is off and the barrel is unlocking before chamber pressures drop enough to let the brass shrink back down.

[The_Shadow]

How do we still use the terminology " head-spaces on the case mouth" for any of the pistol calibers?  It would seem that whether it is .005 or .110 it would not make any difference as its really not touching the end of the chamber.  Does this actually apply to pistols other than Glock as we have all read about shooting .40 S&W from a Glock but not a 1911.

Agreed, the amount of "SLOP" with these semi autos is probably necessary by design, for more reliable feeding and function.  A lot of the headspacing is actually being held by the extractor.  It does seem like the extractor has to take a lot of the "SLOP" as part of its function.

One thing that really would pose a pressure issue, is if the casing is too long and has a heavy taper crimp, this would exceed the end of chamber cut.  When the cartridge is fire in this condition and the bullet starts to move, the casing can't expand at the very mouth due to contact with the forcing cone, thus could cause the pressure spike.

Azrckcrawler writes, I would think the only way to get stretched 10mm brass is if the timing is off and the barrel is unlocking before chamber pressures drop enough to let the brass shrink back down.

I have often mentioned that early unlocking increases unsupported areas.  I  has seen brass that exhibited smiles and bulging that looed like it was pushed out of the chamber some while under great pressure.  Two issues come to mind here!
1). The ammo was very high pressure as loaded and exceeded the mass of the slide and recoil system.
2). The recoil system could be weaker or not helping at the in battery lockup.  (by that I refer to captive spring system) 

I have seen some Glocks where their captive RSA would just drop out during disassembly or have very little pressure applied.  It is yet another reason I opted for non-captive recoil spring or springs in my Glocks and I feel it does make a difference.  Here is an example of measurements I took of my G-20SF and G-29

Glock 20SF Factory spring test
It takes 5lb 3oz to start the slide to move from the locked position
Full retraction at 18lb 0oz at lock open

Glock 20SF spring test Wolff Gun Springs 22lb RSA installed
It takes 6lb 4oz to start the slide to move from the locked position
Full retraction at 22lb 9oz at lock open

22-Slightly over a pound difference 1lb 1oz to start the slide to move from the locked position
24-Slightly over a two pound difference 2lb 3oz to start the slide to move from the locked position
22-Slightly over a 2 pound difference 2lb 9oz at lock open
24-Slightly over a 6 pound difference 6lb 1oz at lock open


Glock 29 spring test Wolff Gun Springs 21lb RSA installed
It takes 6lb 4oz to start the slide to move from the locked position
Full retraction at 21lb 3oz at lock open

Glock 29 spring test Wolff Gun Springs 23lb RSA installed
It takes 7lb 1oz to start the slide to move from the locked position
Full retraction at 23lb 5oz at lock open

Glock 29 Factory spring test
It takes 4lb 5oz to start the slide to move from the locked position
Full retraction at 16lb 10oz at lock open

If enough force is applied to the slide it will remain in battery  and not unlock, but that defeats the cycling of the semi auto function.

With ammo I have loaded and test fired, I didn't see smiles that others experienced that they tested...and some had casing blowout failures.
I don't always load to those levels recklessly, but do so only in the effort to better understand the limitations of both the firearms and ammunition componets.  Clint Eastwood said it best; "A man's got to know his limitations!"

[sparkyv]

I've never even considered measuring the case length for pistol cases; it's never been an issue with other pistol calibers.  Crud, is this something I should start doing for 10mm?