Sticky bolt lift, how much to back off or not

[hounddawg]

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.

I check my sizing after firing, after sizing, and before loading. I was running .002 - .003 setback, bumped it down to .004 setback for after last resizing. I guess hot depends on which published load data to believe. I do tend to run close to the top of published data. Like I said in my last post I will go all the way down a couple of more gn's. At this point I am doubting it is rounds and am leaning more toward a receiver/ bolt issue. But am willing to shotgun my approach trying everything. I still have to find a slower powder that has had success in other peoples rifles, still researching that

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

I have some Rem .260 that has over 15 firings, the 6BR brass last week was on it's 3rd

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

I have a Annealeeze sitting on my bench. Have not used it in a year but will give it a try on 5 rounds this afternoon just to see. If that cures the issue I will will go back to annealing after every firing and rethink my opinion on annealing, if it do I will go all the way and get a AMP. In my opinion it is the best design, but that is just my opinion and we all know the old saying about opinions and odor lol

thanks for the suggestions

 

[Nathan]

I’m looking at 3 data sources. The hottest I see is 29.4 gr....That is why I said kinda hot. Still, I can see how your rig may go over that safely, or it may not. Factory actions stretch more than the overbuilt custom benchrest actions....it just is what it is.


The problem you were trying to solve was higher than normal bolt lift, maybe due to high pressure. You identified you might be at max loads....seems like it.

I was just thinking the other side of heavy bolt lift....one side it all about the load, expansion, action stretch, etc, right? The other side is about springback, hardening of brass in loading process, maybe same die settings. IME, most guys get un fired bolt lift right on day one with new brass and kind of set/forget...me too...then brass hardens from firing and now bolt closing force is going up, but it is sneaky due to the caming action of the lugs. Now your max loads stretch the action the same amount, but the brass springs back less. It also sizes down less each sizing.

I have to admit, 3 firings is a super short time to see this issue in. Might help to try 20 new or anneal 20. You will have to reset your fl sizing die, just a bit as it will push the shoulder back more and be loose!

Do you have the newest Annealeez with the digital speed control? Wow! I love that thing! I know it is fire and that is kinda imprecise, but still cool. I just record, tip to case, inner flame length and speed. That seems repeatable to me for multiple setups..

 

[hounddawg]

I linked the Hogdon load data a couple of posts back which shows a max of 32.5. With the loaded rounds having a shoulder setback of .003 - .004 I really don't see what annealing has to do with it but still I will give anything a try at this point. Just throwing mud against the wall seeing if something sticks. Seems to me as if it were a sizing problem it would show up when chambering, but I did read on another forum where going back another couple of thousanths of an inch cured the issue for them. I did have a tight neck problem which showed up when chambering on the Lapua brass but turning them down to .011 cured that. This one is a puzzler, I am leaning more and more toward it being a receiver/bolt issue

 

[Nathan]

Where are you finding the 6mm BR Norma on the Hodgdon website? I don’t see that.

 

[hounddawg]

Good question, it won't show for me now either. That data in post 19 was cut and paste. I thought I may have confused it with dasher or other 6mm data but dasher is way higher and nothing else matches. I have no idea why it shows sometimes and then does not. I am starting to really mistrust the Hogdon load data now. I am dropping down to 27.0 - 28.0 and if the problem goes away I will never use the Hogdon load data site again. I just placed an order for a Berger load manual, something I should have done long ago

 

[reynolds357]

Good question, it won't show for me now either. That data in post 19 was cut and paste. I thought I may have confused it with dasher or other 6mm data but dasher is way higher and nothing else matches. I have no idea why it shows sometimes and then does not. I am starting to really mistrust the Hogdon load data now. I am dropping down to 27.0 - 28.0 and if the problem goes away I will never use the Hogdon load data site again. I just placed an order for a Berger load manual, something I should have done long ago

Hodgdon shows 29gr for 6BRM with 107 gr bullet. By their data, you are definitely good. That load was maxed due to cimpression, not pressure. So, in the Norma 29 would be light. My Berger manual is at my office. I will let you know what it says tomorrow. I honestly think virgon brass will cure your problem. Seen it happen too many times. If it dies cure your priblem, the next step is where it gets aggravating.

 

[Unclenick]

Well, as the Sierra manual says a load manual paints a picture of what the load did in the test gun, and that definitely does not mean its a safe load in your gun. Sierra tends to be more conservative, but they just invested recently in building their own pressure test lab and they're apparently following Hornady's lead in adopting Doppler radar. So all this stuff may change again. We'll have to wait and see.

I actually had looked at the Hodgdon load before looking at it in the new Sierra #6 and knew the original load was only about a grain over. My reasoning was that if one place found the limit lower, that might be the case for Hounddawg's gun so let's see how the cases fare with a more substantially reduced load. There is no way to know how much you'll have to reduce a load in a particular gun to get free of indicators until you do it.

 

[hounddawg]

thanks Reynolds, I sent a email to Berger and their manual on the way. Hopefully I can get to the range Tuesday and see how 27 - 28.0 works for me

 

[Unclenick]

Hounddawg,

I've looked through both Hodgdon's Pistol and Rifle cartridge lists twice and didn't pick up an entry for 6 BR Norma there. What cartridges did you find it next to?

The Sierra listing is for 6 mm BR Norma, BTW. They explain the relationship to the Remington version, but don't list it separately.

 

[hounddawg]

figured out that I must have screwed up, embarrassed to admit it. I must have been looking at the 6.5 BR data on the Hogdon data site. The pet loads over on the 6BR website must have been for shorter barrels. Guess I am lucky that the only thing hurt was my ego. Going to redo the load workup and maxxing it out at 28.5

Thanks for the help guys, sorry to put you through all this BS for my mistake

 

[Unclenick]

It happens. You get a little weary and the brain crosses up. You'll be wicked alert to data for a while now, though.

 

[HiBC]

houdawg,I'll toss it out there again.

I get it that you are focused on the accuracy you got with Varget. That matters.

I picture the powder burn rate and the bullet acceleration being in a race going down the barrel.

If the powder burn is outrunning the bullet,pressure spikes.

Another bad analogy,would be a dragster's engine power curve versus gearing.

If you have a 7000 rpm engine,it might be that 3,00 rear end gears are too tall,but something like a 5.36 might be too deep.

There is a balance to achieve

If I was using 105 gr bullets in a 6mm,if I was loading up around max with a mid range burn powder like Varget, I'd sure look at shifting gears to a slower powder. Especially since you have 29 in of barrel to burn it in. I'd at least experiment with a 4350. Just to see. Maybe RE-19.

Good luck!

If someone had Quickload(I don't) it will give you a percentage of powder burned in the bore.That might be interesting to play with. Given your 29 in bbl,I wonder what the %of Varget burned would be if you plugged in a parameter of 24 in bbl. What if its 99 or 100 % burn at 24 in?

 

[Unclenick]

Oh, it will do more than that. it will rank all the powders in its database by velocity performance. I don't know Hounddawgs actual as-fired case water overflow capacity or which 105 grain Berger he is using, but with the VLD the program thinks Reloader 17 compressed 105% is the velocity king, followed by CFE223 for an uncompressed load (93.6%). It shows they burn 100% and 99%, respectively, in the long barrel. This is running at top pressure.

 

[hounddawg]

HiBC, appreciate your advice and no disrespect meant but I have done a ton of research on this little cartridge and no one uses H4350. Varget,and H4895, seem to be the top choices with a few using Norma 203B and various VV 540, N140 and N150

I might give the 4350 a chance once I get this reduced Varget load tested if the Berger manual give me a starting load. I use H4350 in my 6 CM and Rem 260 and it shoots great. I just have not found anyone on any forum that has had luck with it in 6BR. Neither the Hogdon or the Sierra 4th list any H4350 loads and Hornady only has data up to the 80 gn bullets.

 

[Nathan]

Reloaded 15 would be another good choice to try on the slow end..

I’m a little confused about your loading technique did you find a node at 30, or were you there for another reason? If it was at a node, I’m guessing 28.0 will be a complete miss...

I would likely jump powders before burning bullets and bore up. With the next one, find the sticky bolt point first with a pressure ladder. A pressure/velocity ladder will show you where velocity gets closer between charge weights and also alerts you when it starts becoming divergent....that is also when bolt and primers start to show pressure.

 

[Unclenick]

If you subscribe to Chris Long's OBT theory and 30 grains was a node, the next node will be at 27.4 to 27.5 grains of Varget.

In QuickLOAD IMR4895 is another good performer for velocity. About 100 fps slower than the other two I mentioned, but they were just for top velocity.

 

[hounddawg]

the 6 BR seems pretty forgiving as far as jump and velocity, here is the original load workup. Pressure issues did not develop until the barrel started tightening up at around 125 rounds. Here is the initial load workup rounds 36 - 61 were the seating test and initial charge test were rounds 62 - 87

Loaded up 40 more rounds in the Norma brass 10 rounds each at 27.5 - 27.7 -27.9 - 28.1 back to the range tomorrow with fresh batteries in the chrono. Rain Saturday so no match no pressure.

edit Berger emailed me a data sheet - Varget min is 26.5 max 29.4 in a 24 inch barrel. Only other powder on the sheet that I have on the shelf is RL 15. Looks like most of the powders they recommend is stuff that you would see on a .223 sheet

edit 2 also loading 5 more rounds at 29.2 using new cases to see if the case change theory pans out

 

[hounddawg]

Dis a bit more chrono testing yesterday and found a lower node which gave me good numbers and groups. Problem solved, bolt was about as slick as a Savage bolt can get. It can maintain mach 1.3 at 1000 so that is all I need. 27.9 2723- AV, ES-17, 8- SD, 5 shots .36 MOA

thanks to everyone for the suggestions and help

 

[Don Fischer]

This is a bench rest rifle? Think I'd check neck thickness. I've read that those rifles are generally set up with min chamber's and some time's the necks need turned to let the bullet go right. Next though is work up to where you have the problem, one round at a time about 1/2 gr difference in powder as you go up. Fire one at a time. Your simply looking for a max load for that rifle. If you got a sticky bolt I would think there would be an ejector mark also but, I get the first sign of a sticky bolt I back off to the load before it and call it max.

 

[reynolds357]

This is a bench rest rifle? Think I'd check neck thickness. I've read that those rifles are generally set up with min chamber's and some time's the necks need turned to let the bullet go right. Next though is work up to where you have the problem, one round at a time about 1/2 gr difference in powder as you go up. Fire one at a time. Your simply looking for a max load for that rifle. If you got a sticky bolt I would think there would be an ejector mark also but, I get the first sign of a sticky bolt I back off to the load before it and call it max.

He already solved the problem.