Heavy bolt lift at low charges with 6BR

[Patruck825]

So i think i have resolved this to a degree...but i am posting here for some insight and to help others out that may have a similar issues.

I have a 26" 6BR that had heavy bolt lift and extractor marks lift no matter what charge i used. i tried 3 powders, Varget, 4895, and IMR 4166. with charges as low as 26.5gr around 2550fps with a 105 hybrid. Loaded 15 thou off the lands.

I sized the cases with a Redding type S bushing FL die, .267 bushing, neck tension is good. bumped shoulder back 2 thou off headspace.

The reason i am posting is because this problem, while it has largely gone away after taking 2 thou off my shell holder and resizing my cases, i still get the occasional slightly heavy bolt lift. Nothing like before, but there doesn't seem to be any rhyme or reason to it.

I am up to a charge of 29.1gr of 4895 at 2858fps, and have tested up to 30.6gr with no issues, but even at the lower charge weight i get heavier bolt lift sometimes.

any ideas?

 

[Stan Taylor]

My question is what neck chamber what action give some good information I think a lot of folk here can help.

 

[Patruck825]

My question is what neck chamber what action give some good information I think a lot of folk here can help.

It’s a Bighorn TL3, action has been fine with numerous other calibers. Barrel is new, .271 neck. Not sure on reamer specs other than that.

 

[Stan Taylor]

I don't see enough on the back to cause a problem it is interesting that you are having these issues your case don't show any thing major a little more information would be good you said something about rechamber break that down please.

 

[nmjwolf]

Sounds like clickers maybe. If you have a die that doesn't size the base enough you will get clickers. Measure the case .200 line before and after sizing to see whats going on.

 

[Bkluke]

Sounds like clickers maybe. If you have a die that doesn't size the base enough you will get clickers. Measure the case .200 line before and after sizing to see whats going on.

I agree.

 

[Patruck825]

Sounds like clickers maybe. If you have a die that doesn't size the base enough you will get clickers. Measure the case .200 line before and after sizing to see whats going on.

No click upon top of bolt lift that I notice, it was heaviest from the bottom of the lift until it broke free at the top. Where is the .200 line? Sorry I am new to 6BR

 

[Patruck825]

I don't see enough on the back to cause a problem it is interesting that you are having these issues your case don't show any thing major a little more information would be good you said something about rechamber break that down please.

When I said “rechamber” I simply meant I chambered a fried case with sharpie on it.

 

[nmjwolf]

No click upon top of bolt lift that I notice, it was heaviest from the bottom of the lift until it broke free at the top. Where is the .200 line? Sorry I am new to 6BR

https://www.wheeleraccuracy.com/videos

Go there and watch the does your die fit your chamber video.

 

[Patruck825]

https://www.wheeleraccuracy.com/videos

Go there and watch the does your die fit your chamber video.

Great video!

So my sized case measures 0.4695 at the .200 line and a fired case measures 0.4700 or 0.4705

That doesn’t sound like much room

 

[Bkluke]

I don’t think that .0005 to .001 is enough. I had the same problem with a Redding die in a WSM last year. I ended up getting a Widden custom die.

 

[Patruck825]

Wouldn’t I have more trouble chambering a round than ejecting one then? I’m
Not sure why the trouble with heavy bolt lift even if the die isn’t sizing the case enough.

 

[hogpatrol]

Are you using new brass or brass shot in another rifle?

 

[Patruck825]

Are you using new brass or brass shot in another rifle?

New brass

 

[gambleone]

What brand of brass? Those diagonal serrations should not show up like that. You say you can't capture the whole pic. Looks like after firing, your base is expanding and causing the extractor marks upon ejecting. Are your powder measurements correct?
What do the primers look like?

 

[Patruck825]

What brand of brass? Those diagonal serrations should not show up like that. You say you can't capture the whole pic. Looks like after firing, your base is expanding and causing the extractor marks upon ejecting. Are your powder measurements correct?
What do the primers look like?

Lapua Brass. I tried to repeat the marks in sharpie again and could not, I don’t think it’s an issue. How would the extractor do that anyway?
Powder measurements are accurate to the grain, being measured on an fx-120i.
Primers are fine but I have never had primers be an indicator of pressure in this action.

 

[Bkluke]

Try a new die with some new brass maybe. I had to scrap most of my brass that I was using last year. Depending on how many firings you have on them.
Unless you can get the old brass to size down. My old brass would spring back to what they where sized before. So they had a memory and annealing didn’t help.

 

[dskogman]

You can get a base sizing die that makes the base a little smaller in a tight chamber. I use one on a 284.

 

[Patruck825]

Try a new die with some new brass maybe. I had to scrap most of my brass that I was using last year. Depending on how many firings you have on them.
Unless you can get the old brass to size down. My old brass would spring back to what they where sized before. So they had a memory and annealing didn’t help.

Any idea how much your die is supposed to size down the base? Alex wheelers video is very informative, but he doesn’t mention how much tolerance at the base you should have. My .0005 seems tight, and I am ready to contact harrels for a die that fits better, but I want to make sure that this small tolerance is something that should be addressed.

 

[Bkluke]

.002 would be ideal.