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tripntx

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Reply with quote  #1 
What steps need to be taken to form 6mm Mongoose brass?
What length does the brass need to be cut too before sizing?

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jwtharpe

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Reply with quote  #2 
Quote:
Originally Posted by tripntx
What steps need to be taken to form 6mm Mongoose brass?
What length does the brass need to be cut too before sizing?

You don't have to cut before sizing. You will end up with around .040 to .050 to trim after sizing. 
I'm thinking about doing a video on it. 
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BIGGDAWG

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Reply with quote  #3 
Jw is case length 1.70 inches? or what is trim to spec?
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tripntx

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Reply with quote  #4 
Quote:
Originally Posted by jwtharpe
You don't have to cut before sizing. You will end up with around .040 to .050 to trim after sizing.
That sounds easy enough.

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surveyor

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One of the BIG draws for me of the mongoose is the ease in case forming, others are shared components with what I already have and load for, and not giving up case capacity.

I'm looking forward to it.
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jwtharpe

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Reply with quote  #6 
Quote:
Originally Posted by BIGGDAWG
JW, is case length 1.70 inches? or what is trim to spec?

Wall is 1.700" assuming zero headspace.( bolt tight against go gauge)

1.690" would be max.

I trim to .010" off the wall, your brass will shrink a few thou on the first firing. It will be way short if you trim to min. length before fire forming. Same as any other bottle neck cat formed from a longer parent.
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tripntx

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Reply with quote  #7 
I just purchased 1k of these at $132 with free shipping to use for forming Mongoose brass. I'd still like to purchase a couple hundred from JB as well.
http://www.brownells.com/reloading/brass/rifle-brass/once-fired-processed-rifle-brass-fully-processed-once-fired-brass-5-56mm-sku100015403-71073-146523.aspx   


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JoshD

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JW, if I read that correctly, after sizing the brass, you then trim to 1.690" ?if that's correct, 1.690" will become max case length, what would min case length be?  I received my dies this last weekend and started forming brass, but have yet to trim anything, honestly because I am nervous I will trim too short.
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BIGGDAWG

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Reply with quote  #9 
the brass he says will shrink and i have seen it so if the wall is at 1.7 i am going to set mine at 1.695 for the first round then after fire forming will set at 1.690
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jwtharpe

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Reply with quote  #10 
Quote:
Originally Posted by JoshD
JW, if I read that correctly, after sizing the brass, you then trim to 1.690" ?if that's correct, 1.690" will become max case length, what would min case length be?  I received my dies this last weekend and started forming brass, but have yet to trim anything, honestly because I am nervous I will trim too short.

Yes, 1.690" is max length. You can trim to 1.690" and let it shrink on the first firing. It should end up around 1.687"ish depending on how hot your first shot load is. Me and BIGGDAWG  always trim to max length after every firing, so we start off a bit longer and let it shrink back close to max length. 
Most important thing is don't load hot on the first firing, and stay off of the forcing cone at the end of the chamber. Just like loading the wolverine except you don't have to trim as much.
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jwtharpe

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Reply with quote  #11 
I added this to the load data page. Folks can comment on it here since Trip already started a thread on it.

Here are final case dims and forming and loading procedures. This is the way I do it. You might have another process that you like better. I will try to add a video when I can get set up for it.

Starting with LC 5.56 once fired brass.

Resize using the mongoose size die with a .010" space between the shell holder and the die. This can be accomplished with a +.010" redding shell holder from their comp. shell holder set, or by using a shim between the die base and the top of the shell holder, or by backing off the die to create the gap (least likely to give consistent results).

Trim brass to 1.690", chamfer and de-burr and remove primer crimp if not already removed.

Try to chamber your newly formed piece of brass in your rifle.

Does it go easily into battery?

If yes then go on ahead with your loading procedure.

If no then set this case to the side and start over with a new piece of brass and reduce the space between the shell holder and the die to .008" with whichever method you selected on the first piece of brass.

Keep reducing the space between the shell holder and die and resize with a new piece of brass until your brass closes in the chamber without effort. Always be sure to keep the trim length to 1.690" which is max case length.

The reason for using a new piece of brass each time is because the brass that you just sized will not want to move with the .002" bump that you create when reducing the bump gap. It will likely try to spring back to where it was on the first sizing. Just set it to the side and start with a new piece.

Once you have your die/shell holder set so that your brass will chamber you can now go ahead and start loading whichever bullet/powder/primer combination that you want.

Once you have some loaded the neck diameters need to be checked to make sure there will be no interference in the chamber. The maximum diameter that a loaded neck can be is .269". the chamber neck is .271" so you will need .002" minimum room in order for the bullet to release cleanly from the neck and not create a high pressure situation.
The chamber reamer dims are set around LC brass as the parent and its neck thickness.  All of the LC brass that I have used clears the neck with some room to spare. Some other manufactures might not work without neck turning. Those need to be checked near the neck/shoulder jct. to be sure. I know for sure Lapua necks will need to be turned because of how thick the shoulders are on them. I also checked some TA surplus brass that was close to .269" after loading. So I turn those two manufactures brass for sure before loading them.

From all of the load data that I have seen, the published data (not data from Joe Blow off the internet) from various sources are showing max loads for 6x45 to be midrange loads for the mongoose. I have been going half way between max and min for the 6x45, start my ladders there and work up. I have been ending up around a grain or two over max listed loads for the 6x45.
As you all know, there is not a max length for it. You will have to determine where your length needs to be based on your projectile choice. We cant just load to 2.2XX" and call it good because some projectiles will be into the lands at a shorter OAL. You will need a modified case, or use some other method to determine where your projectiles hit the lands and load accordingly.

One last important thing! This is for any hand load! If you have a loaded  cartridge that does not go into battery, do not force it into battery. Something is wrong with it. set it to the side and take some measurements later. It could be a thick neck, loaded too long, jacked up case. Just don't try to force it to shoot. It can bite you!

Also, if you have a 300BLK keep it away. The short case of the BLK will go into battery if the neck tension is light or the crimp is defeated and there is enough space in the case for the bullet to set back.

Be safe!

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tripntx

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Reply with quote  #12 
Quote:
Originally Posted by jwtharpe
Starting with LC 5.56 once fired brass.

Resize using the mongoose size die with a .010" space between the shell holder and the die. This can be accomplished with a +.010" redding shell holder from their comp. shell holder set, or by using a shim between the die base and the top of the shell holder, or by backing off the die to create the gap (least likely to give consistent results).

Trim brass to 1.690", chamfer and de-burr and remove primer crimp if not already removed.

JW,
Above you state "starting with LC 5.56 once fired brass". Will new 5.56 or once fired and resized to 5.56 follow the same directions you wrote? 
New Lake City brass will be available from Midway on 5/13 http://www.midwayusa.com/product/953699731/federal-lake-city-reloading-brass-556x45mm-nato

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tripntx

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Reply with quote  #13 
Setup my 6mm Mongoose FL Sizing die today per JW's instructions (lucky I have Redding's #10 shell holder kit). Used once fired brass that had been resized .223. Ran four of them through the Goose sizing die. They appear to have formed properly. I spent more time adjusting my dead-on trimmer to trim the required 1.690".  
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tripntx

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Reply with quote  #14 
BTW, I found a new place to order Nato brass from https://brassmanbrass.com/
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jwtharpe

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Reply with quote  #15 
Same process for new brass. Just make sure to check the necks after you get a bullet seated. necks have to be less than .268" on a loaded round.

Thanks for the brass link.
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tripntx

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Reply with quote  #16 
Quote:
Originally Posted by jwtharpe
Same process for new brass. Just make sure to check the necks after you get a bullet seated. necks have to be less than .268" on a loaded round.

Thanks for the brass link.

I appreciate the reply.
Couple of weeks ago I ordered 1k once fired, processed, resized 5.56 NATO. Started sorting it today by headstamp and became disgruntled, LOL.
Went searching and found new unfired unprimed LC 5.56 NATO brass at the link I shared earlier, so I purchased 1k of them. They will be specifically for my 6mm Mongoose.

BTW, I have really liked my Lee Classic 4 hole turret press, that is until today when I started setting it up for converting 5.56 NATO to 6mm Mongoose. The slop in Lee's turret head gave me fits for a while.

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jwtharpe

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Reply with quote  #17 
Quote:
Originally Posted by tripntx
I appreciate the reply. Couple of weeks ago I ordered 1k once fired, processed, resized 5.56 NATO. Started sorting it today by headstamp and became disgruntled, LOL.
Went searching and found new unfired unprimed LC 5.56 NATO brass at the link I shared earlier, so I purchased 1k of them. They will be specifically for my 6mm Mongoose.

BTW, I have really liked my Lee Classic 4 hole turret press, that is until today when I started setting it up for converting 5.56 NATO to 6mm Mongoose. The slop in Lee's turret head gave me fits for a while.

Let us know what the headstamp reads on the new lc brass.

The lee 4 hole classic is a good all purpose press. I have broken a turret ring on mine, and had to replace the plastic indexer parts after thousands of pistol and small rifle rounds. 
The biggest thing I like about it is swapping cartridges. 
It takes ten seconds to go from 277wlv to 45acp.
Once you get your dies set up on the turret you don't have to mess with them ever again. With pistol dies you have the fourth hole for your crimp die that the old 3 hole turret didn't have. 

JoshD, you can set you minimum trim to 1.685", or 1.680" after you shoot them the first time.
You will notice that your necks don't grow as much as 5.56 because of the sharper angles at the shoulder and neck. I have some brass that I trimmed too short at 1.670" I still use it, it works fine.
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Omega

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Reply with quote  #18 
Quote:
Originally Posted by jwtharpe
Let us know what the headstamp reads on the new lc brass.

The lee 4 hole classic is a good all purpose press. I have broken a turret ring on mine, and had to replace the plastic indexer parts after thousands of pistol and small rifle rounds. 
The biggest thing I like about it is swapping cartridges. 
It takes ten seconds to go from 277wlv to 45acp.
Once you get your dies set up on the turret you don't have to mess with them ever again. With pistol dies you have the fourth hole for your crimp die that the old 3 hole turret didn't have. 
Wow, never heard of breaking a turret ring before, what where you doing, using it as a swage press?  I have only had to replace the plastic index pieces once which Lee sent me for free, but I mostly index by hand now so don't expect that to be an issue anymore.  I have the older 3-hole turret but had considered getting the classic cast and possibly converting it to a 3-hole because I have so many turret rings.  But since it really doesn't give me that much of an advantage over my old one and I have since got a Lee Bench Primer I have not proceeded with the upgrade.

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BIGGDAWG

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Reply with quote  #19 
formed about 15 pieces this weekend testing the waters.

going to assume the slight wrinkle is normal because the case is blown out at the body shoulder union and the die don't support it when forming.  i tried pmc and lc 11 and both did it with little lube and with a lot didn't matter. here are a few for inspection.

20160509_112103.jpg 


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RangerJoe

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Reply with quote  #20 
Yup - the "donut ring" is normal for the initial sizing.  Sometimes they look worse.. but still work.  There is a funny thread here somewhere on "ugly cases"... [biggrin]

http://mdws.forumchitchat.com/post/deformed-cases-7902915

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jwtharpe

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Reply with quote  #21 
Omega, I was making some 257 bobcat brass out of 308. It requires a fair bit of pressure to push the shoulder back on those. Two of the bolts had worked loose and only one was tight. I think that is what caused it to break. I sent Lee a pic of it and they sent out a new ring that day. Was back in business three days later. Lee CS has always been good the couple times that I have had a problem. 

BIGGDAWG,  those look good. Your right about the body of the case not being supported. It will get a crumple in it if the shoulder of the once fired brass has a dent in it. It doesn't hurt anything, just ugly like RJ says. Just load it up and shoot it out. [biggrin]
Check the necks on those PMC's. I have not tried any of those yet. 
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BIGGDAWG

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Reply with quote  #22 
figured as much i tried several things to get it to stop and when it didn't i figured all was well.   just looks a little like the one time i had my seater die set wrong and was trying to crimp and seat at same time.

I saw that post by jw on ugly cases i do the same thing if they chamber. just made a batch of x40 from blanks and some of them had a nice dent in the body, they passed the case gauge so loading them up and shooting them.

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tripntx

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Reply with quote  #23 
All my issues setting up my lee classic 4 hole turret was because I didn't realize the donut ring was normal for this round. Time for me to setup my die again to get the ring. Luckily I only wanted two goose brass sized at the moment since I dont have a barrel in hand. I assumed the distance turret travels up before hitting stops was causing the ring because I always adjust die to have shell holder push turret into stops.
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jwtharpe

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Reply with quote  #24 
Quote:
Originally Posted by tripntx
All my issues setting up my lee classic 4 hole turret was because I didn't realize the donut ring was normal for this round. Time for me to setup my die again to get the ring. Luckily I only wanted two goose brass sized at the moment since I dont have a barrel in hand. I assumed the distance turret travels up before hitting stops was causing the ring because I always adjust die to have shell holder push turret into stops.

If you measure the body of the case with a caliper, you can follow the taper of the 223 parent right up to the start of the donut at the body/shoulder jct. Nothing can be done about it without some psi inside the case to push it out. 
This is where the extra capacity comes from after fire forming. 
If your once fired 5.56 brass was shot from a worn out or oversize chamber it will look better after forming.
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BIGGDAWG

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Reply with quote  #25 
I don't want too made up Tripntx either. just wanted to start playing and getting my set up working.

now that i know what to look for i am going to figure out how far to trim with my rt1200 to have it close for fire forming. i have a modified 223 size die for my rt1200 so i think my set up will be put on my hornady lnl, trimmer in 2, 243 expander in 3, and the mongoose size die in 4, that is my tentative plan anyhow. will see how it works. going to shoot for 1.69 +/- .005

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