Issues with shoulder setback on 7RM

[Blanco]

Prepping some 7Mag brass and measuring with the Hornady shoulder gauge
my measurements are are all over the place.
Using a piece of new Hornady loaded ammo I measure 2.110
fired brass measures about 2.118
I get pretty heavy bolt resistance at 2.115
bolt seems normal at 2.113
I first bump the bulge out at the belt, then do a full length resize.
When I remeasure my shoulder I get between 2.114 and 2.009
Am I just being overly nitpicking or is there a real issue here ?
I am using a Lee die set and the sizing die bottoms out on the cartridge belt.
I have never really looked at my 7RM as closely and I have made very shootable ammo in the past.
So am I missing something here or is 7RM maybe just that sloppy ??

 

[jepp2]

I first bump the bulge out at the belt, then do a full length resize.

On factory loads you have a bulge you have to deal with on the initial firing? How are you bumping the bulge out?

fired brass measures about 2.118
I get pretty heavy bolt resistance at 2.115

Your numbers don't make sense to me. How is the bolt lift on the fired brass? Are you using a stripped bolt to check resistance? I just don't see how 0.003" shoulder setback can result in heavy bolt resistance.

I would normally see as much as 0.018" forward movement of the shoulder on the initial firing, as it headspaces off the belt on this firing. After that, I would use a body die to size the case so I had 0.002" setback from bolt contact. Are you sure the bolt contact you are experiencing are from Case Head to Datum length?

 

[Coyotefurharvester]

If fired brass chambers properly at 2.118 and then you size it to 2.115 and experience heavy bolt effort. You have 1.brass that needs trimming 2.carbon ring in chamber at case mouth 3. Sizing die not set properly.
Using .420 comparator new Rem nickel brass 2.111
Reloaded brass 2.1175(Browning A bolt 2).
My measurement/load notes.

 

[Blanco]

First off the bulge around the belt is removed with this die

https://www.larrywillis.com.

I'm measuring the brass with the Hornady Headspace comparator

Lock‑N‑Load® Headspace Comparator & Anvil Base Kit - Hornady Manufacturing, Inc

Lock‑N‑Load® Headspace Comparator & Anvil Base Kit Lock-N-Load® Headspace Comparator The Lock-N-Load® Headspace Comparator extends brass life, improves accuracy, and enhances safety. The gauge measures...

www.hornady.com

The brass is 1x fired Hornady brass, but not in my gun
New factory loaded Hornady brass measures 2.110
The fired brass measures 2.118 and I can not close the bolt on this brass
The bolt will close with some heavy bolt resistance on brass sized to 2.115
The bolt will close normally with slight resistance at the end of the bolt stroke sized to 2.113
I went back and reset my sizing die so that the ram was at top of stroke then slowly turned the die in gradually until I got the shoulder measurement at 2.113/ 2.112
I also noticed that pressure at the end of sizing was critical. It took a soft landing when the belt met the die.
For now I am getting good results so it may have just been die adjustment ..

 

[Coyotefurharvester]

Do you know if it is the bulge or datum length that prevents the bolt from closing on unsized brass? I have not needed the Willis die on any 7,300,338 brass (crossed fingers) yet.

 

[Blanco]

Do you know if it is the bulge or datum length that prevents the bolt from closing on unsized brass? I have not needed the Willis die on any 7,300,338 brass (crossed fingers) yet.

Datum length for sure. Out of about 250 pcs of brass i only came across 5~6 that needed to be de-bulged. I do all of them anyway

 

[Coyotefurharvester]

Once you have brass fired from your rifle, reset die checking brass fit with a stripped bolt if possible. I size hunting ammo to close with NO extra bolt effort. Set sizing die stripped, make sure inside neck lubed, and expander/pin is set properly.

 

[Clark]

I run 7mmRM so hot that not even the Larry Willis die can make it right again.
I throw the brass away after one time use.
I also load it at 3.34" OAL, not 3.29" sammi registered.
I have ~~ a dozen 7mmRM rifles. I chambered them all myself, except the Ruger #1.
I headspace at 0.215" not the saami registered minimum of 0.220".
I have have never found a piece of 7mmRM brass bigger than 0.215" to the belt. I made a fixture to measure my belted cases.

 

[jackieschmidt]

This is just for my info.

The whole object of the belted case is that in the factory configuration, it headspaces on the belt.

Everything I have ever read tells shooters that once you fire it once, forget about the belt and use the shoulder bump to control headspace. This is supposed to enhance accuracy.

I never could quite understand this logic. The belt offers a very precise headspace as long as all of the belt dimensions are the same from case to case.

Has it ever been proven that the belt should become a non needed item for better accuracy after fireforming.

Last year, I offered to help a customer with his Remington Sendero in 7mm Magnum. He was going on a African hunting trip where you had to use Factory Ammunition. He chose four suitable brands with bullets designed for African Plains, hoping one would shoot close to 1 MOA.

every one of the Factory loads blew, (Fire-formed), the shoulder out at least .010 inch. Surprisingly, the most accurate ammo we shot was the older 150 grn Remington Core Lockt.

 

[LCazador]

I recently had a similar experience with a 300 Win. Mag and Hornady brass and Lee dies. This was a customers firearm, brass, and dies. Same issue with shoulder bump up to .006" difference. After using a Redding competition shell holder set to set bump and Redding dies, issue gone. I advised my customer accordingly. Frankly for a hunting rifle it makes little difference.

 

[BoydAllen]

If a full length die is a proper match to a chamber, a measured .001 shorter than tight at the shoulder will close with no resistance. Essentially FL dies for belted cases need to be set up just like those used for rimless cases. I suggest that you use a large marker to blacken a sized case that is tight to help determine where it is binding in your chamber, that and a lot of measuring at various points up and down the body of the case, comparing fired to sized.

 

[Blanco]

Really this thread was just a conversation confirming what part of the reloading process I was not performing correctly.
Once again its the nut behind the bolt !

 

[PhilC]

Essentially FL dies for belted cases need to be set up just like those used for rimless cases.

Exactly.

 

[K22]

Watch the recent video on gunblue490's web site entitled, "Should Your Magnum Be Belted or " wherein he thoroughly explains the design, head spacing, and reloading issues associated with belted magnums. It's very worthwhile if you reload belted magnums.