300 WM Load Help / Question??

[wegner426]

Fairly new to reloading but wanted to get some input from the members here that load 300 WM. I am using Win Brass with CCI 250 Primers and H1000 behind 208 AMAX. Rifle is a Rem 700 5R.

My question is this......the fired brass appears to grow about .022 thousands in length measured at the shoulder compared to new unfired brass.

If I work up a load based off of full length sized / new brass, then only neck size the brass for subsequent loadings am I wasting my time on the first load workup?

In my mind it shouldnt matter as the full length sized brass is going to end up the same size as the neck sized brass right after ignition correct? Or is the larger volume of the neck sized brass going to change the pressure that much and make the load worked up off the new brass worthless in the neck sized brass?

Thanks in advance,
Chad

 

[Rob01]

Re: 300 WM Load Help / Question??

I am doing the exact same thing now and my brass is growing about the same. I don't think it's worth;less working up a load now. It gives you an area to work from when you load the once fired and neck sized brass. You might have to adjust the load up a few tenths. That's what i am planning on.

 

[Grumulkin]

Re: 300 WM Load Help / Question??

Your load workup will not be in vain. There may be some difference in velocity but whether it would be do to a slightly longer case or to differences in friction at the neck would be debatable. In fact, different was of cleaning brass can result in small differences in how a gun shoots.

 

[chain]

Re: 300 WM Load Help / Question??

I keep the data on two loadings, FL sized or new brass and Neck sized brass. I neck size after the first firing and bump shoulder back when I need to. There is a varience in velocity probably not enough to notice until you get out there a ways but I am anal about my brass prep.

 

[sandwarrior]

Re: 300 WM Load Help / Question??

wegner426,

You are not wasting your time putting a good load together the first firing of this brass. As you probably know the belted cartridges headspace off the belt not the shoulder. the shoulder is actually loose in the chamber. But held square to the bore by the trueness of the belt. So, you're going to get some growth. Although it seemed to me that the growth in mine was only around .006" or so.

Anyhow, when you expand your case there is sort of a pressure buffer. Once the case fits the chamber that is gone. It won't be much of a change in volume during powder ignition so you're going to hit the hard pressure ceiling at about the same volume of powder. To give this an analogy, think of this like fire forming an Ackley case. Take a full power load in the parent case and shoot it in an Ackley and it almost feels like you touched off a .22 Hornet. The next time you shoot that load in a formed case, it'll feel more like a normal light load in the case. With a belted mag there is a lot less volume being created during case expansion. When the case is expanding it offers a buffer. When the case isn't expanding it will hold pressure tightly.

You won't have to adjust much. Just for S&G's fill a case of each with water and see what the difference is.

 

[wegner426]

Re: 300 WM Load Help / Question??

Thanks for the comments guys. I was under the impression that the belt would no longer serve any purpose if I neck sized and headspaced off the shoulder, making the brass last longer. I thought the idea was to do this instead and headspace off the shoulder rather than full length resizing every time.

I did get a collet resizer for the body made by I believe Larry Wilson to resize the body just above the belt so they will continue to chamber easily. Am I way off base here?

Thanks,
Chad

 

[Rob01]

Re: 300 WM Load Help / Question??

You are right on. The collet die works well also.

 

[Grumulkin]

Re: 300 WM Load Help / Question??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: wegner426</div><div class="ubbcode-body">Thanks for the comments guys. I was under the impression that the belt would no longer serve any purpose if I neck sized and headspaced off the shoulder, making the brass last longer. I thought the idea was to do this instead and headspace off the shoulder rather than full length resizing every time.

I did get a collet resizer for the body made by I believe Larry Wilson to resize the body just above the belt so they will continue to chamber easily. Am I way off base here?</div></div>

A bottle necked belted case can headspace off the belt or off the shoulder and for best case life, headspaceing off the shoulder is preferred. I've had the body collet resizer die for several years now and I've never needed to use it and this is despite the fact that much of my belted case shooting is with single shot rifles that don't have the mechanical advantage of a bolt action rifle.

 

[sandwarrior]

Re: 300 WM Load Help / Question??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Grumulkin</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: wegner426</div><div class="ubbcode-body">Thanks for the comments guys. I was under the impression that the belt would no longer serve any purpose if I neck sized and headspaced off the shoulder, making the brass last longer. I thought the idea was to do this instead and headspace off the shoulder rather than full length resizing every time.

I did get a collet resizer for the body made by I believe Larry Wilson to resize the body just above the belt so they will continue to chamber easily. Am I way off base here?</div></div>

A bottle necked belted case can headspace off the belt or off the shoulder and for best case life, headspaceing off the shoulder is preferred. I've had the body collet resizer die for several years now and I've never needed to use it and this is despite the fact that much of my belted case shooting is with single shot rifles that don't have the mechanical advantage of a bolt action rifle.</div></div>

+1...and as Rob01 said, the body collet die by Wilson is a good idea too.