Some sizing questions for .300WM belted casings

[Road_Clam]

I picked up a used R700 SPS in .300WM for cheap money and am building a mid-long range clone to my R700 .308 Varmint. Building and shooting a .300WM "punisher" pro-efficiently will hopefully train me to better shoot my .308. So now i'm gathering data on reloading and there seems to be relibility issues if you don't correctly size the belted mag casings. So I had some awesome conversations with Larry Willis who sold me a collet die to eliminate case separation which is common in belted mag casings. Now upon further reading i'm seeing many magnum pro's like to use "fire formed" casings. So i'm calling on the magnum experts to educate me on the pros and cons of both resizing methods. Thanks !

 

[jimbires]

I'm no expert , but I do have a few belted mags . I size this case just like any other case , by pushing the shoulder back about .002 . by doing this the case does not head space off the belt , it uses the shoulder just like a non-belted case . I read about guys using Larry's collet die . I've never seen the need for it with my rifles . from what I gather it sizes the brass case right in front of the belt . apparently my full length die sizes mine enough that I don't have a problem .

 

[CatShooter]

I shoot 3 belted cases - the 264 WM, the 300 WM and the 375 H&H.

When you shoot a case, the shoulder will blow forward and fill the chamber. As jimbires said - from that point onward, you treat it like a standard case and let it headspace on the shoulder.

I rarely FL size and of my cases. I neck size, and I have never had the problems that Larry Willis claims to happen.

 

[wapiti25]

Yes, on what has been said. Headspace off the shoulder. I shoot 7mm Rem Mag, 338 Win Mag. Have shot 300 Win Mag, 300 H&H, 375 H&H. I do not use the collet die

 

[Jason Boersma]

I've been shooting a 300WM with the same cases for 6 years FL sizing with redding dies every time never had any problems.

 

[cotntop]

Got in the 300 WM game when brass was in short supply. Bought some Federal brass at funshow and had to buy a LW collet die due to brass stuck in chamber after firing. This straightened out the problem I had with the brass sticking in chamber when fired. I have not fired any brass a second time since using collet die. Starting in on a new batch of Norma and do not think I will have the same problem.

 

[Road_Clam]

Got in the 300 WM game when brass was in short supply. Bought some Federal brass at funshow and had to buy a LW collet die due to brass stuck in chamber after firing. This straightened out the problem I had with the brass sticking in chamber when fired. I have not fired any brass a second time since using collet die. Starting in on a new batch of Norma and do not think I will have the same problem.

I've shot about 50 rounds thus far and experienced about 5 or 6 "sticky" factory rounds as far as ejecting the fired casing. Not sure if this is simply from a very new chamber that needs some more break-in. The rifle I bought looks like new. I highly doubt this rifle was shot much. It was only a cheap SPS and it KICKS HARD when fired !

 

[Minesweeper3433]

Mike Bryant built me a very accurate 300winmag years back and after 3 reloads I was having problems with click at top of extraction. Decided to give the collet die a try and the problem went away for good. Now I just include it as a step when sizing belted magnum cases just out of habit. I kind of just figured the rifle had a very tight chamber and that my sizing die was not sizing it enough by about .0015 which led to the progression to bolt click.

 

[Road_Clam]

I bought about 100 once fired brass and just doing some research the used brass won't fully chamber in my rifle. After a FL resize then fit in perfect. However up to this point I have simply set up my sizing die per the RCBS instructions which is "go approx 1/8 turn beyond where the die contacts the shell holder". Now i'm beginning to understand this is not the best method for precise shoulder sizing. Seems the generall rule of thumb is if the fired casing still fully chambers then only do a neck size. I like the idea of using your own rifle's "fire formed" casings and it makes very logical sense as far as maximizing your brass life.

 

[CatShooter]

Now i'm beginning to understand this is not the best method for precise shoulder sizing. Seems the general rule of thumb is if the fired casing still fully chambers then only do a neck size. I like the idea of using your own rifle's "fire formed" casings and it makes very logical sense as far as maximizing your brass life.

Yup... some guys will tell you to full size every time, but those guys are using custom FL dies that are made to the exact chamber dimensions, and will change the case by maybe 0.001"

My 1,000 yard 300-W.M. match rifle's chamber has a shoulder that is 13 thou forward from where a normal (over the counter) FL die's shoulder is.

If I FL'd the cases, they would stretch 13 thou at every firing, and they self-destruct in 3 or 4 firings. I partially necksize (about 1/2 of the neck gets neck sized). I shoot SMK 190's at 2,950.

 

[markm87]

I'll echo what a lot of guys are posting in that I too headspace off the shoulder. I run the LW collet die as needed. (RWS brass requires it less than Norma, for example)

I full length body size every time because we shoot so much 300 WM, I don't have time to check each case for chamber fit. I finish off with a Lee collet neck sizing, and shoot 208 AMAX for target, 200 Accubond for Hunting.

The only brass life Issues I've had are loose primer pockets. Never any type of case separations or anything.

 

[Road_Clam]

Thanks everyone for all the input, you guys are a big help ! One real fact, loading .300WM is time consuming and takes a LOT of prep. It also gets respectively expensive per round vs your typical .223 or .308 match so i'm pro-actively doing my research and asking questions so I can load and shoot well right out of the gate !

 

[Joe Salt]

Road-clam and CatShooter I had this same problem with my 308 Baer years ago, and what it is, is when the rifle was chambered it was headspaced of the shoulder and not the belt. Catshooter you are neck sizing so you will be alright for a while till they get sticky, the you will have to full length size to bring them back. Myself with them being HS. off the belt, I just neck size, and if they start getting sticky I just FL. size and bump the shoulder and I'm good to go again with the neck sizing. Watch for the shiny spots in front of the belt.

Joe Salt

 

[CatShooter]

Road-clam and CatShooter I had this same problem with my 308 Baer years ago, and what it is, is when the rifle was chambered it was headspaced of the shoulder and not the belt. Catshooter you are neck sizing so you will be alright for a while till they get sticky, the you will have to full length size to bring them back. Myself with them being HS. off the belt, I just neck size, and if they start getting sticky I just FL. size and bump the shoulder and I'm good to go again with the neck sizing. Watch for the shiny spots in front of the belt.

Joe Salt

I have been shooting it for a while and no problems - I do not mind a little crush on closure - it is gets too hard, I will bump the shoulders, but not FL size.

I consider FL sizing an act of desperation, and a last resort.

 

[Road_Clam]

I took headspacing off the shoulder to the next level as I decided to purchase Larry's digital headspace gage. I ocassionally have issuse with my precision .308 as far as sometimes the bolt is very stubborn to close, now I understand why. Larry's gage seems to be a quick convienent method to obtain a specific length datum that is derived from your specific chamber. So once I have the measurements of a perfect casing length repeatibilty between resizing casings will be a breeze. As far as FL sizing as long as the base of the casing does not exceede .502 it will chamber smoothly in my rifle. Now I just have to do some experimentation to find out what the dimensions are for casings that will chamber smoothly vs. casings that bind (and also casings that stick upon ejection).

http://www.larrywillis.com/

 

[Joe Salt]

Guys another trick you might try, like I did as long as you are using a bushing die for the necks is my chamber is .336 So I'm neck turning the necks to 11.5 thou and us a .328 bushing, to keep the bullet tension tight. The bolt opens like butter. I do the same thing with my 300 WSM. I think they shoot better with more neck clearance.

Joe Salt

 

[Alex Wheeler]

I full length size every time with everything I shoot. They just flat shoot better with a little room in the chamber.

 

[scpaul]

I load for 4 belted std. cases and 1 belted wildcat. When I size my cases I bring the die down until it's just short of touching the base of the neck. I anneal about every 3-4 loadings. I feel a slight resistance when I close the bolt the last little bit. So far I don't have to trim brass very often and wind up losing brass to loose primer pockets around the 7th. to the 12th loading depending on which one I'm loading. So far I haven't had any head seperations (famous last words). Most of my loads are just less than max. but sometimes I do push it a little bit. Paul

 

[markm87]

I full length size every time with everything I shoot. They just flat shoot better with a little room in the chamber.

Agree. Or at least.. full length sizing doesn't appear to hurt anything.. and makes the bulk processing smoother.

For me, it's just easier and more efficient to run 50 or 100 rounds through the die, and then gauge the belt area on the LarryWillis die. Squeeze any of those down that need it, and move on.

 

[Road_Clam]

So I believe I have the perfect "gauge" dummy chamber round for my .300WM. I used a nice once fired Firocchi match casing , and initially it would not re-chamber, so I backed my sizing die off about 2 turns and FL sized. Then I used the LW collet die to get the casing sized perfect all the way to the belt. I used a lighter to "soot" the shoulder. Then I started turning the die CW 1/8 turns until I observed the die rub away some soot on the shoulder. At this point I was hoping for a measurable gap between the shell holder and the die, but I was into a slight overcam condition. I added a punch mark @ 12 o'clock on the top of my die as a baseline reference for setting up the die in the future. Next I test chambered the dummy round and it chambers perfect. I can feel a very slight resistance when the shoulder contacts the chamber so I know the belt is not contacting the chamber. When I chamber an unfired factory round it feels different I can feel a distinct bump up against the belt. My bolt also closes perfect So now I have a fire formed casing, and I also no can set a baseline ref datum off the shoulder of my reference casing using Larry's shoulder gage setup (which really works slick BTW). So I think i'm all good with the sizing process !

Rich K.