You've got "ring around the brass!"

[Dougfir]

I'd love some opinions on a rifle of mine. It's a Remington 7600 that I use for hunting thick woods in bad conditions. I use a peep sight, rather than a scope. Since getting into reloading, I've tried a few different loads and every time I do, something seems a bit wonky. Accuracy is not very good across the board (best groups are 2", many are 4" using a scope for testing). Velocities aren't what I'd expect. Factory Core Lokt loads in 180 grain clock in around 2500 fps from a 22" barrel. 180 Hornady Interlocks and IMR 4350 gave me about 2400fps at the published max load. 180 Nosler Ballistic Tips and IMR 4350 gave me higher velocities; I hit 2700 fps well below max...
The other think I've noticed about the rifle is that ring around the base of the case, where the sizing die stops. That line often looks much more pronounced on brass fired from this rifle. I'm not seeing any classic pressure signs and I'm not seeing any sign of cracking there, the line is just more pronounced than I see on other brass.

I'm thinking of having a gunsmith look at the rifle to just make sure it's safe, etc. I bought the rifle used, so I can't vouch for how it was treated. Aside from a cracked stock from being dropped when I bought it, it appears to be in good shape, no rust, dings, etc.

In any case, I'd appreciate any thoughts you might have about what I'm seeing. All advice welcome! Thanks!

 

[ShadeTree]

This will sound dumb but the first thing I would do is grab the rifle securely around the receiver with your other hand wiggle up and down, side to side on the barrel and check for any movement of the barrel. On the 760's and 7600 the barrel is not tightened to the receiver but to the barrel extension. I've seen some with horrific movement. For whatever reason they came loose and just need tightened down and you're back in business.

I'm not saying that's it, but I've seen it on those before and it would explain the varying group sizes as well as effect your headspacing.

 

[SJB358]

Dougfir, I am not surprised by the ring around the base. It is just the part that expands to meet the chamber that isn't sized in a plain old FL sizing die. I wouldn't sweat it unless you are seeing other marks to indicate something is wrong.

As to your groups, If you have a chrono, I'd keep inching up your charges to the 2700 mark with the other 180's or try another bullet. I kinda think with a slower powder like 4350 it needs to be running in the higher PSI area before it will really even up and be consistent. I'd also ask how you are resting the rifle when shooting it. My 7600 Whelen will absolutely shoot just as well as my 700 Whelen, but it wants the forend rested nicely in a bag with no extra pressure on it.

On another note, maybe try 56-58 of 4350 with a 165 Nosler or whatever you have and see what it shoots like. Seems to be a pretty danged easy shooting combo in a couple of 06's around here.

 

[preacher]

My first thought is to use a Small Base die or Full Length die making good contact with the ram/shell holder. Make a "dental pick" with a straightened paper clip and insert inside the case, see if it "hangs up" in the ring. If it does and at your lower pressures, your case is actually "resized too much", Bring up the die 1/4 turn and try a new case, see how it chambers,etc.
I used IMR 4350 a ton in the 30-06...as mentioned 58gr/165 is usually very accurate in just about any '06, but start lower a couple grains for your pump and work up. I like 57gr with the 180 and 54gr with any 200gr. I like to zero my peep sights with the tip top part of the bead on the bottom of a black, say 4to6" easily seen target at 100. Try and cradle that fore end as said. Have the bullets hit 1 to 2" high. Usually, the "bottom edge of the bead" will subtend your zero out around 200-230yds with a 45-70/45 Colt and will be about the "middle of your bead" at 300 with your '06. So it is virtually self adjusting. I have made some really sweet "finessing shots" with peeps, ha. Good luck to you Pard.

 

[Dougfir]

Thanks for the ideas. I can't feel any looseness to the barrel. My accuracy testing was done with the rifle resting on bags. I'll have to try that trick with the paperclip.

 

[ShadeTree]

Thanks for the ideas. I can't feel any looseness to the barrel. My accuracy testing was done with the rifle resting on bags. I'll have to try that trick with the paperclip.

Good. Easy enough to check. It's an odd thing to mention and in no way is a suggestion of poor quality, but it happens sometimes. The first one I seen like that I couldn't believe how much you could wobble the barrel. And that was a fairly new 7600 that came loose after somewhat limited shooting. Easy enough fix but until the problem became obvious enough that it was discovered, it had the owner ready to make use out of it as a second rate club.


Best of luck on getting it tracked down and remedied.

 

[RaySendero]

Dougfir, I don't believe you have a problem with that ring.

But, If me, I'd cut one of the fired cases in two.
Cut right down the centerline mouth to case head.
I would look/check for case thickness in the area of the ring.

 

[ElmerThud]

Sounds exactly what SjB said..ring mark at the bottom of the case body above the rim where the cartridge case doesn’t get fully sized inside a full length sizing die.

Absolutely normal.

Getting your charge and bullet seating tuned in correctly will reduce your groups but its all down to case prep and bullet seating technique.