7 mm RM problems

[Buckreed]

I will start with the disclaimer that I'm new and don't pretend to know everything. I have had what I consider good luck with working up a load for a 308, but I have since built a 7RM and having some concerns. I did a couple ladder tests working up in half grains increments. 180gr bergers, retumbo, 0.015 jump and found a good node at 70.0 gr. With my 308 I used a Lee collet neck sizing die, but with the 7mm the once fired brass chambers hard. I didn't see any signs of pressure when working up but I have not encounter this yet and don't have any mentors to ask.
So, should I FL size and not worry about it. What am I missing?

 

[RockyMtnMT]

You will get a bunch of different answers, but here is mine. I always full length size. Particularly for a hunting rifle. It is more consistent as far as I am concerned and less problematic.

Steve

 

[Buckreed]

Thanks Steve. I'm good with full length sizing, but I was worried that something else was going on. Maybe pushing the pressure threshold without realizing something. what causes the 308 to chamber once fired brass fine and not the 7mm after neck sizing?

 

[RockyMtnMT]

Just the spring back of the brass and probably a tighter chamber. You are at an upper end load but I don't think that is a problem.

Steve

 

[Creedmoor shooter]

I used to neck size. Now I bump the shoulders .002-.003. Much happier doing that than neck sizing. I don't have to change my sizing routine ever few firings and the cases slide in the chamber much easier.

 

[desertcj]

70gr of Retumbo shouldn't be causing you any big problems. Have you checked your case length? Perhaps you just aren't familiar with the feel? Neck sized only cases do have a tight feel when you chamber them. That's why they are more accurate. There are a lot of guys here that are going to disagree with me on that and it's funny to me. I've always heard, been taught and used, neck size only and trim for length. It's always worked great for me.

 

[MudRunner2005]

I will start with the disclaimer that I'm new and don't pretend to know everything. I have had what I consider good luck with working up a load for a 308, but I have since built a 7RM and having some concerns. I did a couple ladder tests working up in half grains increments. 180gr bergers, retumbo, 0.015 jump and found a good node at 70.0 gr. With my 308 I used a Lee collet neck sizing die, but with the 7mm the once fired brass chambers hard. I didn't see any signs of pressure when working up but I have not encounter this yet and don't have any mentors to ask.
So, should I FL size and not worry about it. What am I missing?

Describe the "chambering hard" part... What part of the bolt movement do you notice the "hard" part? If it's at the very end, you might need to trim the cases.

 

[Buckreed]

I used to neck size. Now I bump the shoulders .002-.003. Much happier doing that than neck sizing. I don't have to change my sizing routine ever few firings and the cases slide in the chamber much easier.

Thanks for the help. I have read a lot about bumping the shoulder but i have not tried this yet. I will do a search on the proper way and give it a go.

 

[Buckreed]

70gr of Retumbo shouldn't be causing you any big problems. Have you checked your case length? Perhaps you just aren't familiar with the feel? Neck sized only cases do have a tight feel when you chamber them. That's why they are more accurate. There are a lot of guys here that are going to disagree with me on that and it's funny to me. I've always heard, been taught and used, neck size only and trim for length. It's always worked great for me.

Desertcj, Thanks for help. I do trim cases between each firing. I know its probably not necessary and on some no material is removed. I do so just to keep the process the same and to avoid a long case that can spike my pressure.

 

[Bstick]

The brass is swelling right above the belt. Which is causing the hard chambering issue meaning it's hard as hell to close the bolt. You are getting close to pressure signs. When you full length size a belted case, you aren't sizing the whole case. You are missing right above the belt. There is nothing wrong with neck sizing. It's easier on the brass and the brass will last longer. Is all your brass once fired out your gun? Are you full length sizing the once fired brass or neck sizing it? You can't neck size brass that hasn't been fired out of your chamber. There is a high possibility it will be difficult to chamber.

 

[Buckreed]

Describe the "chambering hard" part... What part of the bolt movement do you notice the "hard" part? If it's at the very end, you might need to trim the cases.

MudRunner2005, Thanks for your reply. I am trimming cases between firings and the hard part is closing the bolt. It does not seem to be at the very end.

 

[Buckreed]

The brass is swelling right above the belt. Which is causing the hard chambering issue meaning it's hard as hell to close the bolt. You are getting close to pressure signs. When you full length size a belted case, you aren't sizing the whole case. You are missing right above the belt. There is nothing wrong with neck sizing. It's easier on the brass and the brass will last longer. Is all your brass once fired out your gun? Are you full length sizing the once fired brass or neck sizing it? You can't neck size brass that hasn't been fired out of your chamber. There is a high possibility it will be difficult to chamber.

Thanks BStick, All the brass is fired from the same rifle. I have both neck sized and FL sized the brass. The FL sizing chambers easily, but the neck sizing is difficult to close the bolt.

 

[Bstick]

Thanks BStick, All the brass is fired from the same rifle. I have both neck sized and FL sized the brass. The FL sizing chambers easily, but the neck sizing is difficult to close the bolt.

Now we are getting somewhere. Is the neck sizing die set up properly? The collet die can be tricky sometimes. Also make sure that the collet inside the die isn't hung up or has trash in it. I use a lot of neck sizing collet dies due to the run out and consistency in the necks. If they have trash in them or aren't set up properly they don't work.

 

[RockyMtnMT]

Thanks BStick, All the brass is fired from the same rifle. I have both neck sized and FL sized the brass. The FL sizing chambers easily, but the neck sizing is difficult to close the bolt.

How many firings on this brass?

I think you answered your problem in this response. Just full length size and you are good to go. This is the problem with neck sizeing, at some point after x number of firings the shoulder grows too much and chambering becomes dificult. There is no consensus that neck sizing only has any benefit in accuracy. It creates less work hardning of the brass and may extend the usable life of the brass by a few firings. Not worth the trouble of dificult bolt closing creeping up on you. Particularly in a hunting rifle.

If you enjoy the process of tinkering then neck size and bump the shoulder once they grow too much or full length size keep them trimmed to length and enjoy shooting. I load so that I can shoot, I don't shoot so that I can load.

Steve