260 Rem Assist?

[laysroge]

Ok, so I'll first confess that this is my second caliber selection in 46 years, and that more research might have been wise, but...

I just picked up my 11-year-old 700PSS, having been re-barreled and chambered by R W Hart & Son with a 26" SS fluted Hart barrel in 260 Rem with a 9 twist,very nicely done, by my measure). By now I have surmised that there might have been a different,better?) caliber choice, but my purposes are pretty elementary: Paper and woodchucks, with a dream of long-range without shame.

Things being what they are, I will run what I brung, and that lays the ground work for some questions. On advice, I opted for Lapua 243 brass, which I fire-formed. I know I have a doughnut to remove, and this being my first dance with FF'ing, I have to gather the necessary do-dads.

I have a Forster Original case trimmer, which can be set up with a reamer. I also own a Marquart neck turner, but lack the 6.5mm mandrel. I will use Redding 'S' dies, but have not selected a bushing size yet.

My first question: Do I ream after sizing? I'm thinking that this will thin the necks, and change the bushing size I will need. On the other hand, if I don't size first, then I can't see how I'll get the entire 'nut out of there. This method will obsolete the bushing I start with, once the brass is cut, but I figure that if I factor the reaming into my subsequent bushing selection, then I should be alright. I figure I'd do well to ask.

Next question: Does anyone know where I can get a 6.5mm mandrel for the Marquart neck turner? I bought it used about 10 years ago, and spent a fair amount of time back then tracking down the fact that the maker,Marquart) had departed this earth, and,if memory serves) his widow sold the rights. I can't remember to whom or where.

Next question: Assuming no mandrel can be found, would anyone mind suggesting a replacement tool? I know there are several out there, and figure I can gain by your experiences, and jump to the head of the class.

Next question: I plan to shoot 140gr bullets, and picked up a box of Berger VLD's. With the 1:9 twist, how much lighter can I go with this twist rate, without giving up accuracy?

Last question,for now): Does anyone have a pet load for this set up and the 140 VLD? I'd like to start close to something that works, to abbreviate my development time.

Thanks in advance for your input!

 

[expiper]

Hi Roger...first of all ..nothing wrong with your cal. selection...I dont want U shooting at me with it at any distance..ahaha...
There are lots of great bullets avail. for that cal...and dont fret about the donut...if the freebore is long enuf,you will never know that it is there....Try one of the 140's that you have and see if the bearig surface of the bullet touches or even comes close to that area of the case neck....and if it does ...you can always go to a shorter bullet...123/107 gr Berger/Lapua/Sierra..etc...they will prolly work better with your particular twist/velocity ...Take three cases and test with them ...see if you really have to do all the twisting/turning/reaming to get them to work...you may just be able to start loading and going....,if there is a problem you might try .308 brass and solve the issue if the neck is large enuff to alllow for the thicker neck that will result from the .308 brass.....
About the load....4350/4831 are very good powders to start with...use near max...,your gun will tell you what it likes)..and jam em to start....Roger

 

[FryeGuy]

if you are just planning on shooting woodchucks and paper, why don't you go to a lighter bullet? i shoot both a .260,twist-factory rem) and a 264 win mag,with 1-9 twist), and use sierra 100 HP in mine. i have even shot several deer with them and they perform well and shoot much flatter than the 140's. unless you are shooting to 500-600 yards or farther, why bother with the 140's? you might want to try the 95 v-max, i haven't yet, but several have recommended it. i ended up shooting mostly the sierra 120 SPT in my 260, as it gave the best accuracy. you might also try shooting the gun some before going to all the work of reaming necks, etc. lapua brass is pretty dang good. i shot my 6brx several times and kept all the targets, and then turned the necks just enough to touch true them, and i could see no difference at the range.

 

[DJSBRS]

I am confused on how you got a doughnut after you fire formed your 243 Lapua brass. How did you neck it up from 243 to 264? How tight is your neck chamber? Your loaded round will be around 292.

43 grains of H4350 will get you started with a Sierra 123 and you will be very happy.

Darrell

 

[laysroge]

Darrell,

Thanks for the recipe.

To respond to your question, I let the pressure do the work on the neck. After fire-forming, I neck sized using a .296 bushing, recommended to me by another shooter. After sizing, I manually inserted a bullet into the neck and it slid in easily, until it landed at the bottom of the neck. The depth matches the forward end of the boat tail and the base of the neck, so I concluded that there must be a doughnut. It seems to make sense, since the shoulder would have expanded into the neck, if the shoulder brass was any thicker. I can't honestly explain it, but that is how I drew the conclusion.

To confirm this, I ordered a tube micrometer, so I can correctly measure the neck thickness and verify the situation. I plan to ream it, if necessary. Either way, this will also enable me to know the true thickness so I can select the right bushing size.

I don't know how to measure the neck diameter of the chamber. I presume that the brass springs back when the pressure declines, and I don't know how much to factor into this.

Maybe I should mention that I'm enjoying this process, although I'd enjoy getting out to shoot, even more. Aside from the time delay, the process isn't really bothering me. Mostly, I want to learn and understand the best approach. I do a fair amount of pistol shooting, but I find rifle loading to be more cerebral. I'm just not the expert I ought to be. Hence my presence here...

Comments?

 

[rhino]

I would get some H4350 and ramshot hunter for powder. Federal GM, Wolf, and Winchester primers.

the 1-9 may or may not stabilize the 140 grain bullets...especially the Bergers...depending if it is a true 1-9 twist.

RHINOUT!

 

[DJSBRS]

i honestly doubt you will be able to get the Berger 140 to shoot accurately with a true 1 in 9 twist. That is why I recomended yoi try the Sierra 123. You may be able to get the Berger 130 VLd to work.

I was relly interested how you seated a 264 cal into a 243 cal neck without necking it up first. If you indeed had that much tension and cosiderable clearance at the neck shoulder junction, you will come up with a doughnut. Your trimmer can work or you can take expander mandrels up to a larger size then full lenghth resize.

You can always skin that cat several ways. You be the judge on what path you prefer.

Send me an email and I'll call you if you would like to discuss further.

Darrell

 

[BJILEG]

Only my 260 Broughton with 1-8 will shoot 140gr.period.

 

[laysroge]

Darrell,

I might not have been clear. After FF'g, and then neck sizing to .296, I inserted the bullet with my fingers. It slid in easily, then landed at the bottom of the neck. Then I simply pulled it back out by hand, too. I did not press it into a .243 neck - this was post-fire-forming, and the neck was already expanded by the pressure generated by fireforming.

My FF consisted of 15 gr of Unique, Cream-O'-Wheat, and about .125" of Crisco to hold it together,very stinky and dirty). I did nothing else to these cases.

I'm curious about the 140 gr accuracy question. I requested a twist rate from Hart that would stabilize the 140. The Berger site indicates a 1:9 twist rate, but the consensus seems to be dubious. Since I own a box, I suppose I'll give them a try anyway.

I have a full schedule over the next few days, but will see what questions arise when I take a swing at this brass again soon. I may check in and take you up on your offer then. Thanks!