Sticky bolt lift, how much to back off or not

[hounddawg]

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On my 6BR I am getting a bit of a sticky bolt lift. Nothing major but more than it should be. No flat primers, no dimpling, no ejector or extractor marks marks are present. Load is 30.0 Varget and 105 Berger seated .015 from lands with a 29 inch barrel.

Groups are great at 850. about .9 MOA for 10 shots from a bench which for me is outstanding, my rifles length of pull and scope are set up for prone shooting so my bench scores run a tad higher than prone.

Here is my quandary, I may have one, maybe two range sessions before my next match so not a lot of time to adjust. Would you shoot the match with the 30.0 or drop down to 29.8 (29.6) and rezero

edit - the 850 attachment was this mornings practice and the best I have ever shot which is why I am thinking of staying with the 30.0

 

[HiBC]

I can give you my opinion,and you will do whatever you will do.

Some folks will say "10 %" Some might suggest backing off in 1 gr increments till you like the results.

I'm sure you know how to research data. My Nosler book is handy.

The heaviest bullet they list for 6 mm BR is 80 gr. Varget is one of the recommended powders for an 80 gr bullet.max load 32.5 gr.

You are shooting a relatively heavy for caliber 105 gr bullet. You have a 29 in bbl.

IMO, the root cause of your problem might be Varget is too fast for what you are doing.

I might look toward a burn rate closer to (maybe) 4350, That's a seat of the pants guess.,but you get the idea. Probably does not fit your match schedule.though.

 

[reynolds357]

On my 6BR I am getting a bit of a sticky bolt lift. Nothing major but more than it should be. No flat primers, no dimpling, no ejector or extractor marks marks are present. Load is 30.0 Varget and 105 Berger seated .015 from lands with a 29 inch barrel.

Groups are great at 850. about .9 MOA for 10 shots from a bench which for me is outstanding, my rifles length of pull and scope are set up for prone shooting so my bench scores run a tad higher than prone.

Here is my quandary, I may have one, maybe two range sessions before my next match so not a lot of time to adjust. Would you shoot the match with the 30.0 or drop down to 29.8 (29.6) and rezero

edit - the 850 attachment was this mornings practice and the best I have ever shot which is why I am thinking of staying with the 30.0

Before adjusting charge, load identical load in a couple pieces of virgin brass just to be sure its not brass or sizing related. I have a 30 BR that starts to get sticky on the 5th or 6th shot. I shoulder bump full length size. When they begin to stick, I have to full length size them with a regular die, not my custom dies. They are only sticky on ooen, not close.

 

[Jim Watson]

Speer, in the era of rule of thumb reloading, said that at any "pressure sign" including hard bolt lift, reduce the load 6%. I don't know anybody who has ever done that, most of them cut by half a grain and call it good.

 

[hounddawg]

Thanks for the replies all. I am using FL resizing and using .002 shoulder bump and the neck expansion from loaded round to fired case is .003.

Duly noted on the Varget. Oddly enough 30.0 of Varget is considered a "mild" load, the Hogdon load data goes up to 32.5C in a 24 " barrel. But it is what it is and like I always say if it does not feel right then it probably is not right and that bolt lift just does not feel right

Other powders I have on hand that I found recipes for with 105's and 107's are CFE 223, 8208 XBR, RL 15, IMR 4350 and H 4350. Some data was found on the official powder/bullet manuals, some on the 6BR site

While eating dinner I pretty much decided to pull the bullets on the rest of those loads and drop off to 29.6, load another 25 and test Friday. If they shoot decently that is what I will shoot in the match and if not I will just use my 6CM and experiment with some different powders in th e6BR

 

[Unclenick]

To go with Jim's 6%, I'd always heard 5% either for sticky bolt lift or for sticky extraction from a revolver. Trying it in QuickLOAD with common powders, depending on the powder, these changes land inside the range of 14% to 18% peak pressure reduction in rifle cartridges.

 

[hounddawg]

pretty sure a couple of tenths will do it, it is not like I have to hammer the bolt open. Just a bit more effort than what I am used to on a Savage, which is not known for a smooth bolt at it's best. I had good numbers at 29.2. 5 ES and 3 SD @ 2750 with 29.2 so I will load up 15 each @ 29.2, and 29.6 and do a test run @ 300 yards tomorrow or Friday

 

[Nathan]

What action?

 

[hounddawg]

Savage 12 with a bolt lift kit. Going back to range tomorrow starting at 28.8 and going up to 29.6 in .2 increments over chrono. By this time tomorrow I should have my answer

 

[std7mag]

I'm thinking HIBC, may be onto something.
With the long barrel, i'd try a slower burning powder.
Of the one you listed, i'd lean towards H4350.
Slower than Varget, but slightly faster than IMR4350.

Let me know if you need cases for that 6BR. I found a box of new Rem 6BR at a flea market.
Can't remember what grain bullet, but i can look at the box.
Picked it up for $15 or $20. Can't remember. Sticker still on the box.
I got it for someone on here looking for casings. They didn't want loaded ammo.

 

[hounddawg]

Thanks std7mag but I have 300 cases right now, 100 unopened and anything with a neck over .012 thick has to be turned. I agree that the Varget just may be too fast but it seems to be the powder of choice for the LR benchrest crowd for this cartridge. I don't remember the bolt being this stiff during breakin or initial load testing but then I was having different issues then and needed to turn the necks on the Lapua to just get them to chamber.

Never had a issue like this come up before, I usually get flat primers some other signs when I push the max load data and here I am well below max and nothing except the bolt lift. I bought this action used, I may try a different bolt or swap out the bolt head if it still acts funky tomorrow. I have a spare bolt head in the parts drawer so that may be my next step, either that or swap the barrel to a different action

 

[reynolds357]

Thanks std7mag but I have 300 cases right now, 100 unopened and anything with a neck over .012 thick has to be turned. I agree that the Varget just may be too fast but it seems to be the powder of choice for the LR benchrest crowd for this cartridge. I don't remember the bolt being this stiff during breakin or initial load testing but then I was having different issues then and needed to turn the necks on the Lapua to just get them to chamber.

Never had a issue like this come up before, I usually get flat primers some other signs when I push the max load data and here I am well below max and nothing except the bolt lift. I bought this action used, I may try a different bolt or swap out the bolt head if it still acts funky tomorrow. I have a spare bolt head in the parts drawer so that may be my next step, either that or swap the barrel to a different action

I dont know how old your varget is, but some guys I shoot with have been cussing some of the newer lots of it. The varget I am shooting is 7 or 8 years old so I have not loaded the newer lots.

 

[hounddawg]

dropped down to 28.8 and worked my way back up to 29.6 @300 today. Stil had some sticky even at 28.8. I am going to rebuild bolt this weekend hoping to cure it. Most accurate shooting rifle I have ever shot though, broke through the half MOA barrier for ten shots at 300, a new personal record

 

[reynolds357]

dropped down to 28.8 and worked my way back up to 29.6 @300 today. Stil had some sticky even at 28.8. I am going to rebuild bolt this weekend hoping to cure it. Most accurate shooting rifle I have ever shot though, broke through the half MOA barrier for ten shots at 300, a new personal record

Try a few pieces of new brass. Wont cost you anything.
I know it sounds stupid, but I have seen the problem in a lot of bench rest rifles.

 

[hounddawg]

Try a few pieces of new brass. Wont cost you anything.
I know it sounds stupid, but I have seen the problem in a lot of bench rest rifles.

actually that sounds like a really good idea. I have 100 pieces of virgin Peterson.

There are absolutely no other pressure signs and the stickiness does not increase with powder charge at all, so I am down to the bolt, the receiver lugs or the brass. Using a bore scope the receiver looks good and the bolt lugs were polished and a bolt lift kit installed when I assembled it. I have two other bolts I can try both of which I know are fine. Also if I have to I will swap the barrel to a different receiver

I will try your suggestion next week, thanks

 

[Nathan]

Has your brass been annealed lately?

 

[hounddawg]

Has your brass been annealed lately?

no but lets say I broke down and bought a AMP and annealed. What would that accomplish other than softening the neck and shoulder of the brass? The brass is sized properly already. I shoot and reload five other cartridges and none have problems with no annealing

 

[Unclenick]

I looked at a few manuals and found you were probably about a grain over book. Not much, but I added the required warning the OP. If you know a published source with that load, I can pull it back out again.

It strikes me as odd the change did little to the stickiness. If you load the same brass down to, say 27.1 grains (the nearest bullet weight Sierra max) does it stop? If not, I'd be suspicious, as you are, the bolt has an issue or some debris got into it. Otherwise, I'd be looking for drag marks. Did you find any on the case head?

 

[hounddawg]

Nick the Hogdon data site lists the 6BR Norma and Varget as 30.5 minimum 41,800 CUP and 32.5C 2,798 48,500 CUP. They list the 6BR Remington with Varget as 26.0 min 2,367 39,800 CUP and 29.0C 2,620 50,100 CUP.

http://www.hodgdonreloading.com/data/rifle

Strange since the Norma BR is just the Remington BR with a slightly longer neck from what I have read. I have had issues with the Hogdon site using too high a charge before with a .260 Rem load so I am not surprised that they are higher than Sierra. Some of the long range BR guys are going up a even higher so I was optimistic about the 30.0 charge and thought it was a good compromise

Next range session I am taking a extra bolt along, loading some new brass with the 29.2 load along with some that I have neck turned down to .010 thickness and doing some testing over the chrono. I will also load a few with 27.1 just to see how they behave

No drag marks on the brass. If I still have issues I will swap out the 6BR with the action I have on a .260. The action I am using now came on a 12 FV in .223 that looked like it had been used for prairie dogs, in other words a well worn barrel. I scoped it and the lands were well rounded and the grooves had a ton of copper. I shot a few rounds down it anyway just to see how the action behaved and had no extraction problems as I recall. Last resort will be swapping the 6BR onto another action.

Interesting problem, but I like challenges and I was planning on redoing the .260 with a short varmint taper 6BR putting it in a Shehane stock anyway and moving my .223 to the aluminum chassis. Fun times

 

[Nathan]

no but lets say I broke down and bought a AMP and annealed. What would that accomplish other than softening the neck and shoulder of the brass? The brass is sized properly already. I shoot and reload five other cartridges and none have problems with no annealing

It sounds like you are running this one pretty hot. You are likely sizing to the point that bolt close has light drag, if you are like me. As the brass hardens, it is my understanding that it doesn’t spring back much. Since factory actions usually stretch some, I think you are likely getting longer each firing and not able to bump it back much due to it getting harder.

The first thing I noticed when I got my Annealeez going was that I had by die set cranked down pretty hard to get any bump. After softening, this made the fl sizing setting way too short.

I would bet you are not to that point in the other rifles, or the case/die designs have slightly more leverage.

BTW, I’m not telling you to buy the AMP...my Annealeez works just fine.