Cartridge Case Length - Trimming

[Apollo]

Over a period of time and recently I have seen indirect comments and questions on why, why not and why for do you trim cartridge cases. Those that are new to reloading should be aware of the dangers involved in either not trimming cartridge cases or trimming too short.

Rather than write a long screed on cartridge case trimming I thought it might be better to ask those that don't know, those that think you know but don't know why or those that want a little finer point on trimming cartridge cases to a length. What is that length, is it set in concrete...actually no...!!!!

Two points here. There are different standards. A SAAMI recognised measurement and a Custom Chamber ideal.

What would you like to know in the way of a bit of guidance.

[Shotfox]

Some good points Apollo. I use the Lyman case length guage as a guide. However I have just purchased a CTS case trimmer from the states and I have to say its the best thing I have ever used to trim cases. They also threw in the CTS case guage for the calibre (.223). Once you set the trimmer to the correct case length you never have to change it again , wack it in the drill and run the case through it which takes seconds.It also de burrs the case neck at the same time. Brilliant piece of equipment and I reccomend it worth every cent. You can order direct from CTS Engineering and pay through paypal as no gun shops here have them.

[Ironsides]

I am a low volume reloader for a couple of obscure cartridges, the .32-40 and .375 Win. Can you recommend a good hand operated trimmer. I have this one in mind from L.E. Wilson: http://www.lewilson.com/casetrimmer.html

[Shotfox]

I am a low volume reloader for a couple of obscure cartridges, the .32-40 and .375 Win. Can you recommend a good hand operated trimmer. I have this one in mind from L.E. Wilson: http://www.lewilson.com/casetrimmer.html

There are quite a few vids on youtube about diffrent trimmers. I used to use a Hornady but the CTS trimmer leaves it for dead.

[on_one_wheel]

Regarding the original post.

I would consider myself a beginner in the reloading world as I have only been doing it for 18 months now, but I realise that the most important part of reloading is getting all your measurements exactly right unless you want your rifle to blow up in your face.

I use the SAAMI standards, I have the relevant page printed out ( .243 Winchester ) and make sure I keep my length at the minimum stated.

But the SAAMI data is difficult to decipher as it reads exactly like this... 2.045 - .020 ( 51.94 - 0.51 )

So I read that as Maximum length is 2.045 inches or 51.94 mm
and Minimum length is 2.020 inches or 50.51 mm

IMO its written by a lazy engineer / draftsman who CBF using full numbers.

I think it could easily be interpreted as max. 2.045" to minus .020" witch would be a min. of 2.025"
and max. 51.94mm to minus 0.51mm witch would be a min. of 51.43mm

So am I correct in the first instance ?

For now I am using 50.51mm and have set my Hornady cam lock trimmer for that length.

I have seen a tool made for measuring the actual maximum neck length, basically it was a thin ring cut from the neck of a cartridge and placed on a slide on another cartridge so it could be chambered and have the ring slid forward until it touched the leade.
I'm guessing they take that measurement and minus a safe amount and allow their cartridges grow to that length and keep them there.

I am thinking of only measuring my case lengths each reload and only trimming them when they get to a max length because I don't enjoy chamfering the edges. I spent a couple of hours last night trimming to length and chamfering the edges of 100 shells, probably the one task I enjoy the least.

I am still using my first batch of brass wich is 200 cases that have been fired 4 times now, annealed once after the 3rd time, never been full length sized and trimmed for length once, some twice.
I am now wondering how long it will be before I need to turn the neck od. down, that is one measurement I have not found yet. Edit .... Found it... its on the same SAAMI page and reads .276 ( 7.01 )

[Westy]

Good one Shotfox I'm off to CTS Engineering to see what all the fuss is about???LOL

[Apollo]

Okay, lets start off explaining that "SAAMI" meaning Sporting Arms and Ammunition Manufacturers' Institute, Inc. Basically an institution set up in the USA in an attempt to provide a standardised playing field for the dimensions surrounding firearms measurements and testing standards, manufacturing standards etc.

They are guidelines so what happens in reality may not always be the case but basically they should be close.

http://en.wikipedia.org/wiki/Sporting_A ... _Institute

There is also the European version. "C.I.P." Commission Internationale Permanente and they do try and get on together but not always the case.

http://en.wikipedia.org/wiki/Commission ... Portatives

So basically if you have a USA manufacturer / calibre it will be specified in Inches and European will be Metric so be careful with the conversions.

These are standards that most firearm / ammunition manufacturers follow given their own quality control standards. A Custom built firearm does not necessarily conform to these standards but should be close. There are many custom chambered rifles with wildcat calibres and chambers that do not have any specific standard yet alone a SAAMI specification.

So onto Case Triming. For general standard calibres there will be a specification. Lets take the .243W as mentioned.

The SAAMI specification. http://www.google.com.au/url?sa=t&rct=j ... Gc&cad=rja

You will notice two drawings. One is the Cartridge and the next the Chamber Specification.

The maximum cartridge case suggested length allowable is 2.045" minus tollerence of 0.020" but in the next diagram you will see the Chamber Specification of 2.055" for suggested maximum length and if you approach this length you are looking for trouble and may not even be able to chamber that cartridge case. So we have two workable dimensions, 2.045" being maximum and in general most suggestion and tools are made to trim that dimension by 0.010" (2.035").

"on_one_wheel" In my opinion you are trimming too much by 0.015" from the suggested trim length and that is a suggestion only. Some trim less depending on the specific cartridge and it's growth rate after each firing. The shorter you trim a case neck the more likely you are to cause a carbon ring in the neck area of your chamber prior to the actual bore beginning.

You are correct on the tool meantioned to measure the chamber neck length, overall cartridge chamber length. As long as there isn't a carbon ring in there which will give you a false reading. Another method is to take a mould of the chamber and partly into the bore using a product like "Cerrosafe" Chamber Casting Alloy, easily melted and reusable.

This is not a proceedure the normal reloader would be doing and more likely with those precision reloaders with custom chambers trying to keep cartridge case length to a maximum and precise length. Mostly in the view of maintaining very consistant neck tension as case neck length variation does affect neck tension.

Most people starting off with reloading that trim cases to length will use something like the Lee Case Trimmer Tools. Cheap, easy to use, fairly quick but these have a set trim length, generally 0.010" less than suggested factory maximum length and not available in some chamberings, especially some specific custom chamberings that do not have a standard.

You will need a "Case Length Gauge" for each different calibre. This also applies to some other fancy Case Trimmers that are "Calibre Specific" so you will need one for each calibre case you want to trim. If you have a lot of different calibres this can become very expensive.

The Lee system. 22-250 Calibre shown.





As mentioned by "Ironsides" a lot better system and very adjustable is the "Wilson Case Trimmer". Can be adjusted to suit your own desired trim length but not only that can be used to "skim trim" a cartridge case head to square the head a tiny fraction better than it may be. For those long range precision reloaders it's also used to trim "Bullet Meplat's" if you are doing Bullet Pointing and desire that feature.



The setup for use trimming a Bullet Meplat prior to Bullet Pointing.



For those that may be interested the process for Bullet Pointing.

Normal meplat variations of Berger VLD Bullets.



Normal meplat, trimmed meplat and then a pointed bullet.



The Whidden Pointing Die in use, then the resultant pointed bullet.





I have probably missed some points to do with Cartridge Case Length Trimming and there are many products available that will achieve the objective. Just trying to cover a few.

Sorry, but it's been a long post. Hope it helps some reloaders.

[on_one_wheel]

The maximum cartridge case suggested length allowable is 2.045" minus tollerence of 0.020" but in the next diagram you will see the Chamber Specification of 2.055" for suggested maximum length and if you approach this length you are looking for trouble and may not even be able to chamber that cartridge case. So we have two workable dimensions, 2.045" being maximum and in general most suggestion and tools are made to trim that dimension by 0.010" (2.035").

"on_one_wheel" In my opinion you are trimming too much by 0.015" from the suggested trim length and that is a suggestion only. Some trim less depending on the specific cartridge and it's growth rate after each firing. The shorter you trim a case neck the more likely you are to cause a carbon ring in the neck area of your chamber prior to the actual bore beginning.

I was reading the lengths incorrectly, part of me thought it was a tolerance given but I'm so use to seeing tolerances written as plus or minus ± in the engine building world, so I ignored that gut feeling.

You have just given me a reason to shoot a heap more, I need to allow my brass to grow longer now.

Great reading Apollo, I'm taking in as much as possible on the topic of reloading, I can see myself heading down the competition path one day when I find myself hunting less and find some more free time.

Keep up the good work.

[Apollo]

Well, my hunting days are getting more restricted all the time. It's called being permanently injured / disabled where wandering around all over the place isn't so enjoyable for long periods but still done.

Other things like precision reloading / testing and target shooting keep up the interest and skills. More often than not it's drive out and set up a spot and wait for a bit of long range varminting / hunting attempting to read the wind and make quick decisions on range for that nice head shot.

Understand your reading of the tollerance and that's what I suspected when I read your post. I had to look closely at those SAAMI drawings and the first one on the cartridge case is confusing a little but yep, that the absolute longest case length.

I did mean to add....

I would suggest that case lengths for those reloading are measured with Calipres not a Case Length Gauge.

I have a dozen or more of the Lee Case Trimmer Units but have not used them for years since using the Wilson. My own choice but I prefer to have my case neck lengths on the long side and trim to 0.005" under maximum suggested. Which equates to 0.005" longer than the suggested trim lengths in any of the reloading manuals.

Don't waste that .243W Barrel, life is already short for a .243W and the cases will grow in time. Love the .243W ever since I bought one back in the early 1970's and that was a Brno ZKK 601 that I had for many, many years.

I'll have to think about writing a few more topics on equipment used for other basic reloading tasks and a few more of the precision / competition versions of the same tasks.

Sorry, but I also remembered I didn't comment on your "Case Neck Turning" .... With a "Factory Chambered Rifle" I doubt you will ever need to turn case necks because they grow in thickness as the brass moves, they will have so much clearance it probably will never make a worthwhile difference especially using "normal" reloading dies. Custom chambers and bushing dies are a whole different world, maybe Lee Collet Dies it would help with even neck tension.

So many aspects.

[creet]

Geez that third from the left is real wonky.

Would that pretty much be a guaranteed flyer if loaded with the rest?

[Lorgar]

Geez that third from the left is real wonky.

Would that pretty much be a guaranteed flyer if loaded with the rest?

The worst thing I've found is a significant scratch or bur in the boat tail.

With an tip that's a bit off you lose a little accuracy. With a boat tail that's damaged they curve off at a much sharper rate.

Much more so than a tip difference.

[Apollo]

Funny enough all those and worse have been very accurate at ranges up to 300m and very difficult to prove otherwise further out as many factors come into play.

A whole different topic is Bullet Meplat Trimming and Pointing. Some very good long range target shooters don't bother at all and still win competitions. Some just point those bullets as really the actual irregular meplat has very little affect on accuracy.

Trimming meplats reduces bullet BC, pointing bullets improves bullet BC.

The best test I have done shows that at 500m pointed bullets consistantly have a higher point of impact, better groups I have not done a huge comparison but I do believe the groups improve. Is it worth it, not at short / medium range and it is a lot of work perhaps for very little gain.

[Lorgar]

Most people starting off with reloading that trim cases to length will use something like the Lee Case Trimmer Tools. Cheap, easy to use, fairly quick but these have a set trim length, generally 0.010" less than suggested factory maximum length

Not to dispute the points you made about the Wilson or other higher level setups, but I wouldn't under sell something like the Lee trimming system for casual reloaders/shooters.

I have used them for my hunter rifles in .243, 7mm and .308 and they've worked well for all. I've read some guys complain about a little extra carbon ring to clean off in the chamber due to the brass being that fraction shorter than nominal, but I've never had the problem shooting sub-max loads in those 3 calibres.

For me (and I would suggest others) buying the Wilson Case Trimmer is overkill. Money better spent elsewhere for me since the Lee once is about $15 a calibre or something.

Like you say the Lee does it cheaply, quickly and easily and most importantly keeps your cases at a safe length. That's enough for many I think. Myself included.

[Prettybird]

I do believe the groups improve. Is it worth it, not at short / medium range and it is a lot of work perhaps for very little gain.

I reckon some of these things are worth it even for the 'placebo' effect.

If you're doing the work and believe you're getting a gain, even if it's only a few thou of your groups, it's better than wondering, getting frustrated over not doing it.

Nothing makes me shoot worse than being frustrated with how it's going.

[Apollo]

I agree "Lorgar" ..... there is nothing wrong with the Lee Trimmer Unit.

I've just got too much spare time on my hands.

[Apollo]

I reckon some of these things are worth it even for the 'placebo' effect.

If you're doing the work and believe you're getting a gain, even if it's only a few thou of your groups, it's better than wondering, getting frustrated over not doing it.

Nothing makes me shoot worse than being frustrated with how it's going.

I need every bit of help I can get at longer distances. Just wished I could be better at judging the wind factor.

I'll take every thousands of an inch I can manage if it get's closer to getting a better score. Or, for that matter the long distance head shot on a tiny critter out there thinking he's pretty safe digging holes in my paddock cause he can't see me.

[Apollo]

BTW all. The topic wasn't raised to push the idea of Top Notch Case Trimming. More to do with basics and what is around and what it can do if you proceed down that path.

Basic reloading is fine and there are quite a number of reasonably priced pieces of equipment that achieve your goal when it comes to trimming cases and at some stage you most certainly need to trim cases if you reload.

Would be nice if more posted their version, especially photos of what is being used so those that don't know can see for themselves.

[Warrigul]

I've read some guys complain about a little extra carbon ring to clean off in the chamber due to the brass being that fraction shorter than nominal

Anyone getting a carbon ring in the throat of the chamber is doing something wrong when cleaning the barrel, after all the brushes and cleaning fluid clean the throat as well as the rifling(or should be anyway).

[Apollo]

Anyone getting a carbon ring in the throat of the chamber is doing something wrong when cleaning the barrel, after all the brushes and cleaning fluid clean the throat as well as the rifling(or should be anyway).

The "Carbon Ring" being mentioned has nothing to do with the "Throat" area.

Nobody mention the throat area, in fact I would believe it's nearly impossible to get a carbon ring in the throat area.

The Carbon Ring I mentioned as in the area that is in that area created by a "short neck cartridge case".... It's in the Neck area of the Chamber.

If you use a correct fitting Bore Guide then it would cover that area in the neck that has been exposed by a short case. All the best cleaning methods will not clean what is covered over by the Bore Guide. You need to specifically target that area and the longer it's left the more it builds up and the harder it is to remove until you get a case neck than then is forced into the carbon ring creating a virtual crimp around the bullet. Hence pressure build up.

Hope I explained my specific point to all that may be a little confused about trimming cases too short.

[Warrigul]

Anyone getting a carbon ring in the throat of the chamber is doing something wrong when cleaning the barrel, after all the brushes and cleaning fluid clean the throat as well as the rifling(or should be anyway).

The "Carbon Ring" being mentioned has nothing to do with the "Throat" area.

Nobody mention the throat area, in fact I would believe it's nearly impossible to get a carbon ring in the throat area.

The Carbon Ring I mentioned as in the area that is in that area created by a "short neck cartridge case".... It's in the Neck area of the Chamber.

If you use a correct fitting Bore Guide then it would cover that area in the neck that has been exposed by a short case. All the best cleaning methods will not clean what is covered over by the Bore Guide. You need to specifically target that area and the longer it's left the more it builds up and the harder it is to remove until you get a case neck than then is forced into the carbon ring creating a virtual crimp around the bullet. Hence pressure build up.

Hope I explained my specific point to all that may be a little confused about trimming cases too short.

Ah terminology, I am on about the bit that gets exposed if you over trim, you could call it the neck area or leade etc I suppose but most call the whole area the throat or refer to the overall chamber length.

I don't use bore guides- many people don't(and this also includes many target shooters) unless cleaning from the muzzle(I have quite a few Martini's and have muzzle guides for each calibre in these cases).

But have a little think about it- unless you run maximum length cases all the time there is always going to be part of it(be it called whatever you like, neck area, throat, leade etc) exposed and I have never had an issue with carbon buildup over several thousand rounds, that must be the benefit of not needing a bore guide.

Definately one for those that do use a bore guide to watch out for if that is indeed the case..

throat picture.jpeg (5.01 KiB) Viewed 5464 times

[Apollo]

Okay, you are correct.

Time for me to retire, we have an expert on board that disagrees with many of my friends who are Hall Of Fame members.

Go for it Warrigal.... you have the lot with all that expertise.

BTW.. I disagree, but I'm not going to get a point in without an arguement so that's it.

[Warrigul]

Okay, you are correct.

Time for me to retire, we have an expert on board that disagrees with many of my friends who are Hall Of Fame members.

Go for it Warrigal.... you have the lot with all that expertise.

BTW.. I disagree, but I'm not going to get a point in without an arguement so that's it.

If exiting a logical discussion is your way of proving you are right then so be it.

[Gamerancher]

Have to agree with other fella's about the Lee trimmer. Cheap, easy and accurate especially if you only reload a couple of calibers.
On one wheel, you mention that you don't full length resize but you have had to " trim cases a couple of times " in only 4 reloads. If they are under max. case length, why? Are they hard to chamber? Maybe need to F/L size every third reload? I've got 7-08 cases that have been reloaded nearly 20 times and haven't had to trim yet. They are neck sized only for use in one rifle, factory chamber but f/l sized if I need to use them in another gun that has a tighter chamber in a custom barrel.
You might be making your cases too soft by annealing them. Again, why? Are you having trouble with split necks? Just wonderin'.