OAL advice

[LCconvert]

I have a 270 in a commercial FN rifle. I have measured the OAL with 130 gr. sierra gameking and I am coming up with 3.4XX (don't have the exact numbers in front off me). The book is saying that their test load uses 3.250 for OAL. This is quite a difference. Also, I have measured the chamber to the mouth and it seems I have a lot of free-bore in my action. I am going to measure the cartridge length to the ogive tonight for a more useful number.

 

My question is, if you have no OAL limitations (including the magazine), what would be a good default or starting point for an OAL -- the book OAL of 3.250? Or maybe I should seat the bullet out a little further. Of course, I will work up some loads with different OALs but for now I need some rounds to do some plinking and varmit hunting.

 

thanks!

[.270]

reloading books give you a place to start. this is a lot like the .300 mag discussion. one thing to do is to shoot some at what the book recommends and see if they're accurate. 3.4+" COL seems a little long, but i don't know for sure how your rifle is made. all bullets have a different taper too, and this will affect where they catch the lands. i shoot 140 gr hornadys at 3.355 COL. this is a real tight fit with several thousandths of the bullet in the lands. makes a lot of pressure, but it is real accurate in my rifle. my rifle has also been shot several thousand times and i'm sure there is some erosiion moving the lands out some. it is also an old winchester and they seem to all have long throats. the newer rugers and remingtons seem to have really short throats and have to loaded accordingly. i'd load some at what the book says and see how they shoot and then adjust from there if needed. one thing to keep in mind, if you get them too long you could end up with problems getting them to fit in the magazine. Lark.

[TAM]

You also may want to purchase one of the OAL guage tools from Hornady. That way you can at least measure and find out what you've got to work with. In the end though unless you want to use your rifle as a singel shot loading longer than the magazine will be pointless.

 

Good luck!

[LCconvert]

You also may want to purchase one of the OAL guage tools from Hornady. That way you can at least measure and find out what you've got to work with. In the end though unless you want to use your rifle as a singel shot loading longer than the magazine will be pointless.

 

Good luck!

 

I have measured the OAL with the hornady tool and the sinclair tool. I have also measured the chamber. This is how I came to my conclusion that I have a lot of free-bore. My magazine is plenty big, no restrictions there.

 

My question is since I have a lot of free-bore what would be a good starting point for the OAL. I was going to start with the book number but I thought maybe I should seat the bullet out farther since everyone seems to think getting closer to the lands is always better.

 

thanks!

 

[.270]

a good rule of thumb is .0010" (10/1000's) off the lands. if your freebore is where you say it is you might see some poor accuracy with the bullet as far back as your book says. i usually like bullets to just touch the lands. in small calibers i've had some problems with leaving the bullet in the barrel when you extract a live round from the chamber tho, so i usually load .22 cal .0050" off the lands. a lot of target shooters used to load their rounds maybe .0010" long and let the bolt seat it. that way they had positive lockup in the lands each shot should be real close to exact. but you have to make sure you shoot it everytime you load a round and it makes it a little hard to close the bolt. if you can get reasonably close to the lands you should be able to achieve good accuracy. the trick is to get the bullet into the lands soon enough that it can't start any kind of wobble and throw off accuracy. with the long neck of a .270 that isn't too hard to accomplish. Lark.

[HaYen]

I usually start at .030 and work a range from .1 max to .010 min. I'm more concern with pressure either gained from seating the bullets too deep or too close to (like right on) the lands. YMMV

[Benbrown]

With cup and core bullets, I generally start at .010" off of the lands or the longest OAL that will feed reliably--whichever is shorter. With banded monometal bullets like Barnes TSX and TTSX and Nosler E-Tips, I start at about .030" off the lands. With the old style Barnes, I start at .050". Freebore is not necessarily a bad thing if everything else about the chamber is correct. As you probably know, Weatherby chambers have a lot of freebore as this permits you to use heavier charges of powder without a concomitant increase in pressure. Theoretically, a lot of freebore will burn up the throat of your barrel quicker, but most hunters don't shoot enough for this to be a problem.