7 mm RM problems

[jrock]

My recommendations are along the lines of Bstick. If you really want to see what is going on, you can mark your case with a sharpie and when chambering, you'll see some slight marks where the fit is too tight. It will be at the base just above the belt as Bstick said. Another method I like is to rough the case up with steel wool. That leaves very light marks perpendicular to the bore direction. Then chambering will show a mark that is parallel to the bore direction and will be very easy to see. I do this with bullets trying to find the lands and it is very accurate.

I gave up on neck sizing 7 RM brass as the base swell would be too much to chamber after every firing. I do shoot upper end loads.

 

[Bstick]

7rm is one of my favorite cartridges of all time. I like it so much I am finishing out my 2nd barrel of the year with mine. I average around 1000 rounds before the throat is gone. I order 300 pcs of brass with each barrel. I get 2-3 firings on brass before the swell occurs. I full length size and then neck size. In my rifle I get considerably lower SD with neck sizing. I am shooting a 180 eld at 3041 with a SD of 3 out a 28" brux. The blank I have now fixing to be sent off is a Proof Steel 1:8 that will be finished out at 29" and throated for the 195s.

 

[Buckreed]

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.

Yes, the die is setup properly. I followed the manufacturers instructions and have tried an additional half turn to bring the die further down but got the same results. I just pulled the die apart and everything is clean and free.

 

[Buckreed]

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

Thanks Steve, I will likely do just that and FL size. For my own knowledge I'll look into bumping back the shoulder too. Sounds like just neck sizing alone won't do it because I am using a "hotter" load and will need to bump the shoulder as well.

 

[Bstick]

Thanks Steve, I will likely do just that and FL size. For my own knowledge I'll look into bumping back the shoulder too. Sounds like just neck sizing alone won't do it because I am using a "hotter" load and will need to bump the shoulder as well.

Bumping the shoulder or full length sizing isn't going to help the part above the belt. That is the problem with full length sizing belted magnums. It doesn't size the whole case. There is a special collet die that sizes the whole case. That is the reason you see people who shoot a lot run through brass on belted magnums.

 

[RockyMtnMT]

Bumping the shoulder or full length sizing isn't going to help the part above the belt. That is the problem with full length sizing belted magnums. It doesn't size the whole case. There is a special collet die that sizes the whole case. That is the reason you see people who shoot a lot run through brass on belted magnums.

His brass is chambering easy when full length sized. So the problem is not the belt at this point.

Steve

 

[Bstick]

His brass is chambering easy when full length sized. So the problem is not the belt at this point.

Steve

I wasn't saying that his problem is the belt. I am talking about regardless of what sizing he is doing, he still isn't sizing the full case. He mentioned " sounds like neck sizing alone won't do it because I am using a "hotter load."

Neck sizing is the way to go on belted magnums if the die is set up properly. It sounds like his die isn't set up right even though he already said it was. Like I said, regardless of how you size it, you aren't sizing the whole case which leaves the part above the belt expanded.

 

[Bstick]

Feel free to Pm me if you need help getting this figured out. It won't take long.

 

[Lrt307]

Typica

Feel free to Pm me if you need help getting this figured out. It won't take long.[/QUOTE

Typically if dies are not setup right and pushing the case back to much will cause problems with the case just above the belt. Try backing your die off a tad.

 

[MarkA]

Have loaded belted magnums a long time. Sure fire easy way to FL size and still neck size if you wish. Redding Competition Shell holder makes this easy. Follow their instruction and deterimine which shellholder works for your chamber. This way you are NOT adjusting dies. Die should bottom out firm on shell holder every time. Most accurate shoulder bump I have ever managed. Adjusting die consist of raising ram and run die down to tight to shell holder then lower ram and run die DOWN nuther full turn, tighten lock ring.......... now loosen die bout 1/4 turn and let her wiggle (lets die seek center a tad).. ZERO runout with good dies and press.

I still Wilson Neck sizer but use Redding Body Die with Comp Shell Holders for FL sizing EVERY firing (after determined correct shell holder for chamber). Sure rolls them straight! Anneal every firing

To determine correct shell holder shoot 3 brass neck sizing only til can't chamber. Then follow Redding instructions to determine correct shell holder for your chambe.

And you do NOT have to return the belt area to original size, only has to clear chamber walls by 1.5 thousandths. Just gotta clear and the Body Die will do that.

PS> I have seen belted magnums that did require FL sizing after just one firing. Not common but happens. Chamber dimensions prolly cause it. nothing to be concerned about just deal with it in your loading process.

https://www.midwayusa.com/product/3...m-300-winchester-magnum-338-winchester-magnum

 

[g0rd0]

there are some really good answers and some not so great. It sounds as if you are doing everything right. So, I will add my 2 cents (1.55 cents actually I use Canadian money), I also have 7rm and collet size and I did have trouble setting the die up (also not my first time with a collet die), so, I asked Lee and what they said was take apart the die and clean it then when you reassemble put a drop of fine machine oil on your finger and rub the outside shoulder of the collet then follow the directions for setting the die up. That worked great.
The only time I have sticky bolt now is when I use Remington brass. Nothing wrong with Remington brass my rifle just does not like it.

 

[jrock]

I've used a few collet dies including on my 7RM. I polished the outside of the collet to a mirror and oiled it as well. Really helps.

 

[jreagle]

FWIW i can verify that i had problems with the collet die somehow changing the shoulder where the cartridge wouldnt chamber. took the die apart and cleaned it inside and out; used a pistol rod and patch with powder solvent then oil for the die to die surfaces. assembled the parts, set up as directed; no problems after that. now cleanup the dies every year as part of the routine when starting shooting season.

ps. also found carbon buildup over time on the mandrel from the case mouth. clean this up when needed as well. also a bronze brush run through the case mouth before neck sizing helps reduce the carbon buildup on the mandrel.

 

[Rich Coyle]

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?

I didn't read the thread past this so don't know if someone mentioned it. The chamber could be out of round.