I have a problem, help me figure it out.

[Crowe284]

So, I have been fire forming a lot of 100 Norma cases for my new 7saum. This rifle was chambered with a reamer made by Dave Manson by GA PRECISION. after breaking in the proof research barrel, I found a node between 63.8 grains and 64.2 grains of H1000 and a BR2 primer that would would all shoot 5 shot groups in the .2's to .3's every time with a Berger 180 hybrid .025 off the lands. I fired all 100 cases and then full length resized all cases with a Redding bushing die with a .313 bushing as my loaded round neck was .3145. All cases were trimmed to uniform as well. I bumped the shoulder .002 during the resizing process. I did note that while resizing that there was much more resistance during the resizing process than any other cases I have ever resizes and I was using ample amount of imperial case lube on each case. So over the past couple of days I have been chasing my tail trying to figure out what is going on. When I reloaded the sizes cases with the same 63.8 gr load, accuracy went to crap. In addition I am getting powder suit on the case necks and part of the shoulder which never happened before. So then I took a few cases and sizes them with the die backed out to just size the neck and not bump the shoulder at all. Still have poor accuracy even after tweaking the powder charge a bit and I still have powder residue on part of case shoulder. Today, I grabbed 3 more virgin cases and ran the 63.8 grain load again. All groups were .2-.3 just like before. So, what is happening here?!? Again, im only bumping shoulder .002 when I full length resize and this is the way I have always set my dies up for a hunting rifle with absolutely no problems. Could I have an issue with the die?? I'm at a loss.

 

[Crowe284]

As a note when measuring with hornady headspace gauge, headspace is as follows:

Virgin 1.6195"
Fired 1.626"
Sized 1.624"

 

[dok7mm]

Two things. First, your brass may not have fully formed on first firing. Would once fired brass chamber? Capacity of case changes.
Second and most likely, you had more neck tension on fireforming rounds, if you just loaded and fired new brass without any sizing. That would explain why case necks are not sealing. Try a smaller bushing.

 

[Crowe284]

Once fired unsized brass will chamber fine, full length sized brass chambers fine as did just neck sized one fired.

Neck measurement on virgin is .311-.3115
Fired is .319 exactly what reamer print shows.
Sized is .3125 (.313 bushing used)

My first thought was needing more neck tension...can definitely feel the difference seating bullet in virgin as compared to sized. Should I run a little more neck tension and try a .312 bushing instead of the .313?

 

[dok7mm]

I would think so! Had a similar problem with necks not sealing on a 7 RUM. Went to smaller bushing and no more problems. Bumping it back, when it chambered after firing, probably didn't help either. Hope this helps!

 

[Crowe284]

I would think so! Had a similar problem with necks not sealing on a 7 RUM. Went to smaller bushing and no more problems. Bumping it back, when it chambered after firing, probably didn't help either. Hope this helps!

I'll order smaller bushing tomorrow. Yeah, your right. Old habit of bumping shoulder just to make **** sure round chambers if the rouge piece of crap gets on brass...

 

[dok7mm]

You may need to use an intermediate bushing to get the proper neck tension, taking it down that far.

 

[J E Custom]

I would add that bumping the shoulder when it is not needed (When they chamber fine) only adds case head clearance and allows the case to move at the critical time that the neck needs to seal the chamber.

Just my opinion

J E CUSTOM

 

[TwoMore]

I ran into the exact same thing with a 7 WSM. when I went to .003 tension on the rifle things started running right again. I read where guys were running .001 and that didnt work for me. it only made for loose groups and heavy bolt lift. I size the rifles brass to .281 inside, actually I size all my 284's there

 

[Crowe284]

I ran into the exact same thing with a 7 WSM. when I went to .003 tension on the rifle things started running right again. I read where guys were running .001 and that didnt work for me. it only made for loose groups and heavy bolt lift. I size the rifles brass to .281 inside, actually I size all my 284's there

I'm sorry you had that problem but it's good to hear that you did and fixed it easily! Ordered a couple more bushings this morning that should be here on Friday. I bet it gets me back in business!

 

[TwoMore]

I think you are on the right track....I was shooting some factory rounds from winchester for the brass and noticed the nice clean necks and good velocity and those cases were crimped , got me thinkin lol I was chasin my tail for about a week, when I started neckin tighter it came back. hope it works out , let us know

 

[Crowe284]

I think you are on the right track....I was shooting some factory rounds from winchester for the brass and noticed the nice clean necks and good velocity and those cases were crimped , got me thinkin lol I was chasin my tail for about a week, when I started neckin tighter it came back. hope it works out , let us know

I bet you are 100% correct. I only get the loose groups and powder on neck and shoulder with sized brass that had less neck tension than virgin. I can go run virgin right now and shoot .2" group with no powder on shoulder. Inadequate neck tension has to be the problem. I'll post when I size cases with new bushings adding more neck tension (.003) just like virgin brass.

 

[RT2506]

I once almost sold off a rifle because I could not get it to shoot anything. It was a Rem. 700 in 7mm Rem mag. I ordered 100 new cases and started working up loads. It did not matter what powder and bullet I tried the best it would do at 100 yards was about 1 3/4" groups. When I ran out of new cases I part sized/neck sized with a FL die the cases and loaded up the best load that I had tried before. After shooting 1 shot it was on the paper. I fired shot 2 and could only find that first shot bullet hole. I fired shot 3 and still only that first bullet hole. I thought, great now it can't even keep shots on the target. So I fired shot 4 and 5. After those shots I looked good through the spotting scope and that first shot hole was still the only one in the target BUT it did look a little larger that I thought it should. I walked down to the target and almost fell over. ALL the shots had gone almost into the same hole. That rifle turned out that it would shoot almost anything you put in it well under MOA if you used a case that has been fire formed and part sized. So strange things do happen.

 

[Mikecr]

You might go back to the root cause.
It sounds to me an oversize chamber, as this passes all tests here.
Couple other things; a smaller neck bushing will do nothing for neck sealing..
And NEW cases are meaningless to anything.