Forming .243 brass from 30-06 or 270 cases

[Sturmcrow]

The chamber of my .243 Win is pretty loose and the throat is too long. When loading 70gr bullets out far enough to touch the lands, only .1" or so of the bullet is in the case.

In the interest of fixing both of those problems, I am thinking about forming brass for the rifle from 30-06 cases. I know that .308 would be easier, but then I wouldn't be able to make the cases a smidge longer and the neck thickness would likely not be enough to get a nice fit in the loose throat.

I know that I need to leave clearance between the case mouth and the end of the throat and that I need to make sure there is also some slack between the loaded neck and the throat, I just don't have those numbers in front of me.

The questions that I have regard the process to form the larger case to the smaller one. I am planning to use a regular Lee .243 full length die.

Do I trim the case most of the way first, then lube it up and press it in? Or is it the other way around?

Am I correct in assuming that I need to pick up a adjustable case trimmer like a Forster rather than using my old Lee trimmer? Alternatively, could a Lee 6mm Rem. trimmer stud have the point ground down a bit to make a slightly longer .243 stud?

 

[MtnCreek]

You would probably come out better re-barreling or having your barrel reset.

I've necked down .308's and it's pretty easy, but I don't think '06 would be. You should probably remove the expander completly on the first press. Have a stuck case remover handy.

FYI: Lee will make you a trimmer guage to your specs.

Good Luck!

 

[kingmt]

I'm sure you could but I would cut most of the length first & would try to find something like the .308 to size to first. I was reading this as I was trimming some very long .243 brass that I just bought.

What kind of rifle do you have & how does it shoot now? I have a Savage that is very deep throated.

 

[Red Cent]

 

[Lunie]

I realize this is probably a terrible suggestion, but as opposed to making longer brass from '06 cases...

You might just be able to fire your .243 cases and "grow" them. (They should tend to grow anyway. Might as well take advantage of it, eh?) Pick a new "Trim-to-Length" to suit your particular gun.

[My manual gives a T-t-L of 2.035"] So, for example, if you want to make cases that are .025" longer, then let them grow, and only trim them when they reach or exceed 2.060" I have no idea how much longer you think you need them to be, but hopefully you understand my example.

Am I really recommending you do this (or saying that I would)? No.

Just thinking about possible approaches to the question you posed.

 

[kludge]

No I wouldn't form -06 cases for .243. I'm with MtnCreek -- have your barrel reset/rechambered. And unless you can make measurements or have the chamber cast, IMO it's a really bad idea to trim the brass too long... and even then, one of your rounds could end up in a good .243 chamber with devastating effects.

OK... some dumb questions here... is there something special about your .243's chamber? Like was the throat cut to be able to seat 105-115gr match bullets with a longer COL? If so you're 70gr bullets aren't going to touch the lands with any kind of neck tension.

Or is your throat just eroded that much?

In either case, I think resetting the barrel, or re-barreling is your best option.

 

[hiker44]

Just buy some new brass.

 

[kenhwind]

In Phil Sharpe's book on reloading he mentions making .308 cases from 30-06 brass back when the .308 was new and there wasn't any brass. He mentions that when these loads actually got tested they were way overpressure.

The insides of an 06 case might not be compatiblae with the .243 load data, whereas .308 and .243 use the same parent case.

 

[GooseGestapo]

You didn't say what make/model rifle you have so that narrows the suggestions.

First, I'd consider having a competent gun-smith to "set back" the barrel and recut the chamber to a tighter dimension to suit you.

If it is something that a new barrel is economical to obtain, simply re-barrel. But normally, the first option above is the cheapest.

It would be much easier to reform the brass from a .257Roberts. This would involve pushing back the shoulder less, which is the real issue. Secondly, you'll have to neck-ream the case to ensure sufficient clearance on the necks, most likely, as the cases are "tapered" inside, and as you push the shoulder back, you sequentially "thicken" the neck.

My most "appealing" suggestion is to find some "thicker" cases to neck down to .243.

My experience suggests that PMC is the "thickest" brass, followed by mil-spec .308 (7.62x51 Nato), Try running some of this brass though you sizer die, and then "blow out" the shoulder by using ~10gr of Unique and top with creame of wheat to the base of neck, and plug neck with a cleaning patch. This will "form" the case to your chamber, and then check the thickness of the cases to make sure that they will chamber easily.

Uniformity (minimal run-out of bullet) will be more important than the neck fit. I'm assuming that you're not using the rifle for bench-rest competition, hence the slight difference in accuracy will not be that great if you find a good load for your barrel.
Good luck with your "project".

 

[MtnCreek]

If your barrel is greatly eroded, then chasing the lands with a longer neck may be hazardous. Correct me if I'm wrong; when a new chamber is cut, it's cut to accept the case and reamed beyond that to allow for the progectile. The deminsion of the chamber that is cut for the neck area is not the same dia as cut to allow freebore. As erosion removed barrel material, I would assume is mainly removed the lands; leaving the groove dia roughly the same (and I wouldn't think it is consistant). I would think chasing the erosion with a longer neck could cause the neck area to be pinched (hazardous). If my assumptions are correct, then you would still have to ream the chamber to safely accept the longer neck and re-setting the barrel would likely be just as easy. Take note that I used the words 'think' and 'assumption' in the above!

 

[ranger335v]

Making .243 from .30-06/.35 Whelen is easy enough. It does need to be done in stages and I find it better to cut the excess neck as a last step. And, yes, it would be easier to use factory brass but it's also easier to use factory ammo than reloading but that's not what you're asking is it?

I use a .308 die and a 7-08 die first and cut the bulk of the excess necks with a cut-off wheel in a Dremel tool, then finish on a case trimmer. Strongly suggest that you don't allow the case length to exceed normal, the extra neck won't make much - if any - accuracy difference and long necks would present a safety issue if someone else tried to fire your new ammo. And anneal the new necks or your new cases won't last long!

You probably already know that properly FL sized cases stretch very little over the course of their life so that would be no help obtaining what you want to do.

It's certain that you will have to turn the new necks, they WILL be too thick! You can get as close and safe a fit as factory rifles can benefit from by matching your new loaded necks to the same diameter as fired factory cases ... or a couple thou less.

It's rare that a factory rifle will benefit from seating to contact the lands. That's a very common but incorrect idea brought over from BR shooters. Thing is, our rifles are much different from theirs, and our ammo is too, so their methods rarely work well for us. Neither I nor anyone I know has failed to obtain top accuracy seated closer to the lands than about 25 thou, some work great with jumps of 3-4 times that much.

Don't worry about over pressure with your reformed cases. The only reason we would obtain high pressures with reformed cases would be to (foolishly) presume all book loads are magically safe to use willy-nilly without properly working the loads up in our own rifle and using our own components.

Good luck and have fun custom fitting your cases to your chamber, I sure do.

 

[06]

If this is a used rifle someone may have rechambered it for a "wildcat" round. You may want to get that checked by a competent armorer.

 

[kludge]

Making .243 from .30-06/.35 Whelen is easy enough. It does need to be done in stages and I find it better to cut the excess neck as a last step. And, yes, it would be easier to use factory brass but it's also easier to use factory ammo than reloading but that's not what you're asking is it?

I use a .308 die and a 7-08 die first and cut the bulk of the excess necks with a cut-off wheel in a Dremel tool, then finish on a case trimmer. Strongly suggest that you don't allow the case length to exceed normal, the extra neck won't make much - if any - accuracy difference and long necks would present a safety issue if someone else tried to fire your new ammo. And anneal the new necks or your new cases won't last long!

Good advice. You might even start with a .358 Win sizing die. Those shoulders are not easy to move, and it takes time, effort, a lot of patience, and the right amount of lube in the right place, which is why I first recommend redoing your chamber/barrel. (oh, and remove the expanders) And yes, you will have to anneal.

One other comment... on the last step when you use the .243 die... it would be a good idea to leave a "bump" where the neck meets the shoulder. i.e. screw the die in a 1/8 of a turn at a time size the brass, try to chamber the brass, screw the die in 1/8 of a turn, size the brass, check to see if it chambers. When the brass just chambers without having to force the bolt closed stop and lock the die down. Then trim, anneal, and load as normal... this will form the shoulder of the brass to "your" chamber. This will leave a little bump so that the cartridge can headspace in your chamber and then firing it will blow the shoulder out to the perfect dimension for your chamber. After this you can readjust your sizing die to get the minimum resizing needed for your chamber.

It's certain that you will have to turn the new necks, they WILL be too thick! You can get as close and safe a fit as factory rifles can benefit from by matching your new loaded necks to the same diameter as fired factory cases ... or a couple thou less.

Yes. Although I highly recommend you have your chamber neck measured so you *know* how much neck turning to do. 0.003-0.004" of clearance between the loaded cartridge and the chamber is a good start. I would not go tighter than 0.003" unless you are a benchrest shooter and know what you're doing.

ETA: or you could just start with 7mm-08 brass, size once with the .243 dies and leave the "bump". I also will repeat that I would not "trim them long."

 

[Harley Quinn]

I believe if you are going to do it, best to do a trial and error, don't rush self...Have fun and consider it a challenge of sorts...Been there, done it...

Best thing imho, is forget the 70 grain bullet for now

Regards

 

[highlander 5]

Why not use 6 mm Remington brass? Same bullet diameter and your just pushing the shoulder back and the biggest bugaboo neck reaming is eliminated. Didn't read all posts made but I would make a chamber cast to find out what exactly is going on. Trust me on this reforming brass is a lot of work and can get expensive if you have to buy various dies to reform the brass in steps. I just reformed a thousand 223 cases to 300 Blackout,never mind the dremel use a reciprocating saw and a 24 tooth blade,you'll only need one blade.

 

[Clark]

10 years ago I necked 308 down to 243.
All got the same powder charge and bullet.

Do you think some of the bullets got pinched by tight necks?

 

[MtnCreek]

Clark, That is ugly!!!

 

[Sturmcrow]

Wow, thanks for all the great advice.

I should have mentioned before that the rifle is a Ruger M77 Mark II V/T. Based on the leade and the twist rate, I assume it was designed to shoot the heavier bullets well. It's too bad the 100 grainers are a bit much for groundhogs. The 70gr bullets still feed from the magazine when seated to the lands, so at least I have that going for me. I do not believe that the throat is too badly eroded. 100gr Gamekings seat to the lands at 2.747", or just a bit (0.037) over the nominal C.O.L.

I rechecked my notes last night and found that the neck of my chamber is only 2.075". I had been thinking it was longer than that. Considering the problems if a long case gets into a short chamber, I believe that I will take the advice about keeping the TTL (2.035") the same.

I intend to cast the chamber as soon as I get some Cerrosafe. If the neck is tighter than I thought, maybe I can get away with just necking down some 308 for a slightly thicker neck without going to the extreme of 30-06. Unfortunately, I don't have any fired brass around to use to estimate the chamber neck diameter.

The main reason I started considering this idea is that I want to start neck turning. I got to thinking that if I am doing that anyway, maybe I should try to get the necks thicker. My current pet load shoots .75" 5-shot groups at 100 yrds, but I am wondering if I can tighten that up even more. Heck, just letting the barrel cool between shots would probably be a lot cheaper way to go. I'm not really a benchrest shooter, but I do like seeing tight groups on paper.

I did try different C.O.L's, though I do tend to make the bad assumption that shooting only one group of each sample is statistically relevant. In my rifle, seating the 70gr varmint bullet at the lands was tied for the best group. It was tied with seating them 0.015" deeper. Next time I go out, I should load up a couple groups worth of each of those to see how they shoot.

 

[MtnCreek]

We should have guessed Ruger based on your user name.

 

[ranger335v]

"...screw the die in a 1/8 of a turn at a time size the brass, try to chamber the brass, screw the die in 1/8 of a turn, size the brass," etc.

Given that 1/8 turn moves a die about 9 thou and that's several thou more than the full max to min range of headspace I would suggest making die changes of not more than maybe half that much. ??

The suggestion to make a cast to find the actual diameter of the chamber neck is certainly ideal but for this work it's quite safe and effective to work off the diameter of a once fired case.

Forming .243 from 6mm Rem will put shoulder brass in the neck and that will indeed make the necks too thick to use without turning.


Clark: "Do you think some of the bullets got pinched by tight necks? "

Yep.

 

[Sin City Shootist]

I've been playing around with 308 to 243. So far all is good, but I've also gotten into the habit of measuring the neck after loaded to make sure its within specs. So far all have been right on the money.

 

[ranger335v]

Making a .308 neck a .243 should make the necks about 27% thicker. Given that a typical neck is around 13 thou, that means your new necks will be about 16.5 thou thick. Loaded, that will give a neck diameter of around .276" which is the SAAMI max; good to go!

 

[Clark]

Necking 308 down to 260 works 90% of the time.

If you don't mind a horrible pressure spike 10% of the time, it works ok.

 

[Sturmcrow]

MtnCreek, I wish that were true. In fact, let's just pretend that I really am that clever! I do actually like Ruger quite a bit. I have that M77 and a P95 and would like to get a 10/22, Single Six, and Super Redhawk at some point in the future. The M77 isn't perhaps as customizable as a Rem. 700, but mine shoots straighter than me. I sure wouldn't holler if someone dropped a Model 1 in 45-70 in my lap either.

Don't worry, Clark. I will outside neck turn to make sure the neck isn't too thick and I will redo the load buildup since the internal volume will likely be reduced.

 

[marcus40]

I have a Savage in 243 Winchester, and the ammo that i did buy to shoot in the gun is now my reloading brass. I am working up a 75 grain load for foxes and Coyotes. I figure brass is cheap and have never had the situation where I needed to form brass from another caliber, the 243 started out as a wildcat cartridge where a 308 was necked down like the 25-06 is a 30-06 necked down.
Just my 2cents worth, good luck in your endeavors.
Marcus