Modifying Cartridge case

[1S2K]

So, I'm about to shorten the neck on a couple of cartridge cases in order to use the Sinclair chamber length gauge. What do you suggest as the best way to cut off a section without mangling the case? And, i assume it's pretty important to make a square cut for a correct fit? Any suggestions will be much appreciated. Thanks.

 

[BoydAllen]

Personally, I wouldn't think of putting one of those things in a good barrel....no way!

 

[1S2K]

Ok. I respect your experience very much. Would you suggest an alternative?

 

[BoydAllen]

What chamber are you trying to measure, and for what purpose?

 

[1S2K]

A 308and a 243. I'd like to know the maximum length it will allow a case to stretch so that I can minimize case trimming. I'd like to keep case length within a reasonable distance short of what the chamber is reamed for. These are on Remington factory barrels with their typical long throats. Still kindanew to this and trying not to be too anal but just wanted to know how little I can trim length to and still be ok.

 

[BoydAllen]

Rather than use the tool that you proposed, I would stick with manual max and trim lengths and call it good. If I had a friend with a lathe, and he had the time and inclination, I would have them made of brass.

 

[Nvreloader]

Why couldn't you take a 6mm/7x57 or trimmed 06 case about 1/8" longer than the 308/243 case length, full length resize to the 308/243 dimensions.

Then you will have a longer neck and then carefully keep shorting the neck length untill you find the chamber neck length??

A little marking die on the case mouth should show the tale.

Tia,
Don

 

[jonbearman]

You got me thinking why not delrin as it is soft and machines like a dream.

 

[ar10ar15man]

while i respect boyd, this is a case where case life can be extented and less trimming if you know the actual neck length of your chamber. the specs for std chambers tend to provide 15 thou or so clearance for growth.
question one..i used a case trimmer....just kept cutting.
the material is lead based and is designed to not damage the chamber.
they work..i have used them..
log your numbers for each rifle, and trim for the chamber..not the spec...
i tend to use .005 clearance and trim after every firing.....
if you do not want to trim after each firing, i would go with boyd and just trim to spec

 

[BoydAllen]

I used to think that there was an advantage to trimming close to chamber length. I no longer do, so the exercise becomes pointless.

 

[kelbro]

I use them and have found that on most factory barrels, the primer pockets go away before I ever HAVE to trim. Most generous chambers.

 

[lpreddick]

i use the sinclair chamber length gauges immediately after getting a new gun made. the wilson case trimmer allows me to trim as much neck to allow the gauge to seat when chambered and now touch the trimmed neck. you'll have to trim about half the neck length for most and be sure to chamfer and debur before inserting the gauge. neck tension may have to be adjusted so the gauge will be under just enough tension to seat when chambered. these gauges will not hurt the barrel. you need to know chamber length if you don't have the specs on the reamer. i had one chamber that was .007 thous shorter than my brass and i could see the case mouth being rolled in after chambering. tight bolt closure suggested i needed to bump the shoulder but after .003 bump, the bolt was still tight, then i measured the chamber length...voila! trimmed all brass .015 thous shorter and all is well. my latest 22 BR no turn neck chamber was only .010 longer than new lapua and the carbon ring formation is almost nil. i have to measure the cases every 3-4 firings to watch for growth and trim accordingly. measured some factory chambers and....025+ thous longer than the brass and the carbon ring was .025+ and a b___h to get out.

 

[1S2K]

Thanks guys for all your helpful guidance. That's why this is THE best place on the Internet for pro advice and experience. I think I'm good to go now with gleanings from several posts. Thank you all again.

 

[Lazydays]

Rather than use the tool that you proposed, I would stick with manual max and trim lengths and call it good. If I had a friend with a lathe, and he had the time and inclination, I would have them made of brass.

years back I made up a couple dozen 6mm and .223 Delron plugs that were square and about 3/4" long. I actually started out making then out of some cheap stuff similar to Nylon, but the stuff cut real gummy like and od's were all over the place. Then I found a couple rods of .250" Delron. This stuff is harder. Have to cut it with high speed steel to get best results, and had no trouble holding the OD to about a .0005" press fit.

By the way one of the rifles I check had almost .070" depth in the area of the neck.
gary

 

[Lazydays]

You got me thinking why not delrin as it is soft and machines like a dream.

That stuff works well. You'll need a minimum of 3600 rpm and lets hope you still have some razor sharp high speed tool bits (I used REX 95). I did finish out with Scotchbrite and steel wool when I got a little heat in the Delrin.
gary

 

[lpreddick]

not to offend but the sinclair plugs are about $6.95 rounded up to $7 for the nra.

 

[BoydAllen]

When we post, we have folks reading of vastly different and unknown skill levels, and experience. I have one rifle, a tight neck 6PPC that when bore scoped , showed a thin ridge of barrel steel that was pushed up slightly above the freebore diameter at the end of the neck. I don't believe that it would have been possible for this to have been caused by the chambering reamer. Luckily a friend was able to cut it down to flush by carefully using a throating reamer with the correct size pilot, by hand. Looking at the the chamber it looked like something like the piece that Sinclair sells had been used incorrectly, with a case that had not been sufficiently shortened, and as the bolt was closed the front of the neck part of the chamber had been swaged forward slightly, raising the metal in front of it. Whoever did it probably did not know what he had done, because it took a bore scope to see it. I can do a lot of things that I may not want to advise others to do in a post on the internet, because I have no way of knowing who I am "talking" to, what their experience, skill level, or mechanical aptitude are, or whether they are smart enough to pour water out of a boot with the directions written on the bottom of the heel, so I try to keep this in mind when writing posts, that go out to an unknown world. Please understand that I am not referring to anyone on this thread, but speaking in general terms.

 

[fguffey]

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Modifying Cartridge case
« on: 08:54 PM, 04/08/13 »
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So, I'm about to shorten the neck on a couple of cartridge cases in order to use the Sinclair chamber length gauge. What do you suggest as the best way to cut off a section without mangling the case? And, i assume it's pretty important to make a square cut for a correct fit? Any suggestions will be much appreciated. Thanks.
Logged

1S2K, it is too late, had I got involved earlier you would not have needed the Sinclair chamber length gage, for checking the length of the chamber from the mouth of the case to the bolt face. I am a case former, I form cases, I use forming dies, my favorite forming die is the 308 Winchester forming die because it is short, I form 8mm57, 7.7 Japanese and 7mm57 etc., cases with the 308 Winchester forming die.

It should be no secret when deterring the length of the chamber with a modified case the shoulder must not hit first. When forming 308 Winchester modified cases for determining chamber length I form the case from from 30/06 cases. Trimming? It is necessary to trim .391” from the formed 308 W case, I choose to use the hack saw, first, then finish with a file when forming 308 cases, that is 39.1” inches for 100 cases, because the case is supported in the forming die the case neck can be removed in seconds.

When using the forming die to make modified cases adjust the forming die off the shell holder after forming for longer necks, and, before trimming., a good ‘off the shell holder’ would be .015”. It is possible to trim the necks to various lengths with a case trimmer.

Deterring the length of the chamber from the mouth of the chamber to the bolt face should include the difference in length between the chamber and case from the shoulders back to the head of the case and bolt face. For the 308 W the perfect number is .004”.

http://www.saami.org/PubResources/CC_Drawings/Rifle/307%20Winchester.pdf

SAAMI list the case length as 2.015”, the chamber length as 2.025, Speers list the trim to length as 2.005.

I have chambers that have long chambers between between the shoulder and bolt face, one 30/06 chamber has a shoulder that is ahead of a minimum length case by .016”, when forming/sizing cases for that chamber I back the die off the shell holder .014”, the added .014” allows .002” difference in length between the case and chamber. When determining overall length (case and bullet) I add .014”.

Again, the froming die is also a trim die. The forming die is a very accurate trim die.

F. Guffey

 

[fguffey]

Other modified cases, drill the flash hole/primer pocket to a diameter that accommodates a cleaning rod, seat a bullet then remove the bolt chamber the modified case, insert the cleaning rod and push the bullet out of the case toward the lands, when the bullet stops, stop pushing and remove the modified case.

The modified case can then be used to transfer the chamber dimensions to the seating die without comparators and seating bullets and checking for length, the modified case can be used to .000” (zero) the bullet off the lands and for those that use height gages the seating stem protruding above the die can be adjusted to the overall case length.

F. Guffey

 

[fguffey]

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« Reply #4 on: 10:20 PM, 04/08/13 »Quote
A 308 and a 243. I'd like to know the maximum length it will allow a case to stretch so that I can minimize case trimming.

A rhetorical question, does the case stretch? Or does the brass flow?

F. Guffey