How far can you safely stretch brass

[cold_hunter]

I have an idea for a wildcat. Its kind of been done. I want to make a 6.5-7mmWSM but i want to use 270 wsm brass so when I neck them down I dont get extra thick necks. I plan to seat the bullet into the lands and fireform like that to insure no stretching occures at the web. The 7WSM is quite a bit bigger than the other two in capacity is why I want it this way. My question is Is it safe for the 270WSM"s shoulder to blow out that far or will things get too thin. Other plans include using an 06 length action so things can be kept long. I will use a Savage action of course what else and a 28 inch barrel. like a Lilja or a Kriger, and if a Lilja ill use a 3 groove to keep pressures lower. Or so i can push things like the nut that i like to be at times. And i dont compete except with myself which at times can be more competitive than most would think. Ill stick to a 1in9 twist to match hunting bullets and the Bergers. The great guys at Sierra bullets inform me that 1in9 is all i need for Matchkings up to 140grs also. But noone will give me an opinion on the stretching of the brass from the 270 WSM to 7WSM. I will use this monster from prarrie dogs to elk and targets from 100 to 1000 and more depending on my optics and the wind up here.

 

[R Flowers]

This is only a guess, but I would imagine moving the shoulder forward that much during fireforming would not be a problem. The case is not going to be stretching so much as the shoulder is just being moved forward. A lot of wildcats do that, as do simple things like a 7-30 Waters when you make cases from 30-30 cases.

Having said that, I think I would rather just make the cases using 7mm WSM brass and then turn the necks if I needed to. Those are pretty tough cases and I am not sure you would wind up with thick necks.

Also, I can see no reason to use a 30-06 length action if you are going to use a WSM case. That just defeats the idea of the WSM. If you want an 06 length action why not build a 6.5 X 300 Winchester? My buddy had one and it would really go fast. (Just neck down the 300 Win cases and go for it.)

You are certainly on the right track with either of those barrel builders.

Wildcats can be lots of fun, but can be a pain in the butt as well.

 

[rick smith]

You will probably be fine just using 7mmWSM brass. I have made 25Souper brass from 308/ 7/08 and 243 brass without a problem. If you have the dies, make a few cases and give it a try. As far as moving the shoulder forward, Look at the AI's that are formed without a problem.Rick.

 

[Guest]

You'll be fine, as the brass won't stretch and thin much in the area you blow out. The trick is to size down the neck just enough to chamber, where you end up with a bit of a bulge that will engage the transition from shoulder to neck in your chamber, and thus keep the casehead firmly planted against the bolt face. It's easier to do that to describe, but you'll just start out sizing a 270WSM case just a tiny bit at a time (measured by what you see of the neck being sized) and checking whether or not it will chamber. Once you find the length that will chamber relatively tightly, then load some fairly low loads (for fireforming you don't need max loads), and fireform the brass. It will form up perfectly and be a tad tight. Then just partial full length resize it bumping the shoulder back about .001-.002" and you'll be fine.

 

[Ridge_Runner]

It'll work fine, no need to seat in the lands, the false shoulder from the neckdown will hold the headspace, just set the die for a crush fit.

Heres the staps to make a 6.5 Gibbs from a 270 win case. Second from the left is a 270, the third has been necked to a crush fit in a 6.5 Gibbs chamber.
The 2 on the right are a 270 win and a 6.5 Gibbs formed and loaded.
Just watch for the shoulders splitting, (as the case on the left did) I normaly lose 1-2 out of 100 to this.
You can also fireform with cornmeal so you don't waste powder and bullets forming cases, I use the method alot, works great.
RR

 

[cold_hunter]

i wasnt aware of a 6.5 gibb can you tell me about it a little like velocity from a 26in barrel with a few different bullet weights. i like 100 to 130's i have a bum shoulder so i dont care for recoil much. and to answer the thing about why use an 06 action, i do stuff the way i like it not to follow trends and others so whats good for you might not fit me. the cartridge i have in my head and on paper is a bit longer than 2.8 inches and still uses the 7WSM cases because of the capacity in relation to the length of the powder colum ok

 

[Ridge_Runner]

well my Gibbs has a 29.5" barrel, it runs 140's at 3340 fps, with a 26" barrel you should get 3200 or so from it.
Mine is a long range hunting rifle so the 140's are all I've ever shot in it. My groups run well under MOA out to 1K+ yards. wasn't trying to sell you on a Gibbs just wanted you to see the steps for making a 6.5 brass from a 270 based case.
RR

 

[cold_hunter]

well my plan with the 6.5 wildcat is a hunter and the bullets would stop at 130 Berger VLD's so i might be able to go fast and if you can go that fast with a 140 i might make my plans a little different and a longer barrel would make those 130's go real fast so your info helps me alot cause 270 cases are way less expensive then WSM's and i knew about the partial neck bump but thought seating into the lands was better cause the books say to do it that way so thank you for the help again.

 

[Ridge_Runner]

well if you decide to go the 6.5 gibbs route let me add this.

If I were to do it again I would go with the original Gibbs chamber and use the 30/06 based case, use lapua 30/06 brass. that way you could shoot the same velocities and the brass would last longer. at the pressures I run in this rifle, 3 firings is the best I can do but I'm sure lapua brass would double this.
To save barrel life use the cornmeal method to fireform and you'll get years and years of use from the rifle, I know they'll last 2500 rounds from guys who have had them for years, and most of them rebarrel to the same caliber, the 6.5 Gibbs will flat outrun the 264 win mag and give the 6.5/300 weatherby a "run for its money".
here is a target fired from 603 yards from a makeshift rest, measures about 6"

Its an incredible round that can shoot very high BC bullets and has excellant barrel life compared to todays high intensity cartridges.
RR

 

[cold_hunter]

i hear you there but how much does that lapua brass cost and do you neck size it after its formed or do you have to full length. how much did your dies cost and can you do something like use a redding s die with bushings im just stabbing in the dark here. i have always liked the gibb chamber its close to that jdj right and he says form with cornmeal and if you rebarrel then cant you use the old barrel to form nevermind then you need an action id get a cheap stevens action to do that. im a savage man all the way

 

[cold_hunter]

and by the way ridge thats good shooting

 

[Ridge_Runner]

whatever you pay for lapua brass its worth it, trust me on that! I shoot a 7mm Allen Mag which the parent case is a 338 Lapua mag. You wouldn't believe what these cases will endure and still be useable.
I always partial FL size all my cases, and the redding bushing neck size dies work very well but you reach a point where you gotta bump the shoulders.
Dies are about a hundred bucks I think, course mine came from a smith so he made a bit on them also.
FF'ing with cornmeal is an easy process and isn't hard on the barrel if you watch the heat.
RR