What else causes a heavy bolt lift besides pressure?
- Thread starter thefitter
- Start date
Roger is right. Heavy bolt lift can result from brass that is a little too long or too large in the shoulder area. If the brass is too large in the head area, the dreaded "click at the top" results. Time to full length resize with a properly dimensioned die.
Keith Glasscock
Gold $$ Contributor
To answer your second question:
No, it isn't necessarily the first sign of excessive pressure. I have rifles that leave pretty scary looking ejector marks at the same time as the bolt handle getting heavy. In those cases, really flat primers and light ejector marks are the first sign of trouble.
On the resizing issue, if the case head gets a touch too big, then the cam on the bolt has some heavy lifting to do to start the extraction. Typically, shooters describe this as a "click" at the top of bolt lift, but I've never had it with FL sized cases, only neck sized.
There are also other reasons for heavy bolt lift. I assume you dry-fired the rifle and compared the lift force? Cocking cams can cause problems.
Hope this helps...
No, it isn't necessarily the first sign of excessive pressure. I have rifles that leave pretty scary looking ejector marks at the same time as the bolt handle getting heavy. In those cases, really flat primers and light ejector marks are the first sign of trouble.
On the resizing issue, if the case head gets a touch too big, then the cam on the bolt has some heavy lifting to do to start the extraction. Typically, shooters describe this as a "click" at the top of bolt lift, but I've never had it with FL sized cases, only neck sized.
There are also other reasons for heavy bolt lift. I assume you dry-fired the rifle and compared the lift force? Cocking cams can cause problems.
Hope this helps...
Shynloco
You can lead a horse to water, but ........
thefitter said:
I see some explanation, but for me, Terry had the answer to the "first" thing I'd be checking. Also check four casing length which if too long can can that issue. Because I'm an accuracy freak and want to eliminate as many variables in reloading that I possible can control, I have RCBS Precision Mic guages for every caliber I reloaded for. BTW, you never mentioned whether you were shooting reloads or factory ammo when this condition arose. But what I check with those guages I mentioned, is the shoulders of the casings which I have indexed when casings were new and know what the acceptible tolerance is for each of my casings and calibers, which are different. In other words, I find the point of least resistance by removing the firing pin from the bolt and closing it, finding the measurement where the bolt closes the easiest. I then know what the tolerance point is and never let the shoulders increase by more than .002 because that COULD cause what you are describing. The one sure way of not going through that song and dance that I just described is to Full Length Size after every firing, something the serious Benchrest competitors do. I do what I do because the less you work your brass, the longer it lasts. But the Benchrest guys use the best brass (Lapua) and still full length size and don't worry how much their brass gets worked. They watch it closely and many even anneal after every shooting, another action that works the brass. Finally, pressure can certainly cause what you've described, then if your brass is not properly sized, that is something to watch out for and check. Hope you find the cure. And BTW, take a look at your expended primers that can also tell you something about the pressure when cratering shows up, a sure sign of pressure.
In my experience primer cratering is first. Then cratered AND flattened primers occur before hard bolt lift. Assuming you are working your way UP with loads these would be the first indication that you are nearing the top of a load. However cratering and flat primers occur quite a bit before hard bolt lift. I have even had some blown primers ( which can be way too hot a load ) and the bolt lift was normal.Cleaning the the chamber as well as the bolt lugs is important and the lightest coating of lubrication on the bolt lugs would be a place to look at. I like Fiske Lubriplate on the bolt lugs but I am talking about the lightest amount possible. Machinists go nuts when they picture bolt lugs camming and there is NO lube. Everything else has been said above my reply.
As others have said, brass dimensions / sizing can affect bolt-lift pressures. Two ways - if the case is too tight in its headspace fit and needs effort to turn the handle down on chambering, firing doesn't correct the crush fit and the handle will also be hard to lift, but that applies to the initial lift from the fully down position. Then as mentioned the dreaded 'click' caused by a slightly tight fit at the base of the body just above the solid web that sees initial handle movement being easy but sticking just before being fully raised. This can be caused by (a) pressure from the load just fired, but also from a previous over-pressure experience or the case having been previously used in another rifle or chamber. I've had this with a rebarrel job even when the same reamer was used as the gunsmith has cut a marginally shorter chamber 2nd time around, so it takes very little difference to produce the condition.
One problem with modern rifles using high quality custom actions is that the traditional pressure signs are either muted or only appear when you're running at proof-level pressures - primers looking only a 'bit flat', no primer cratering because the pin to bolt fit is so close etc. So, there are no simple rules now and there may be a big difference in signs depending on what you're shooting. I have a friend who only uses high quality strong actions (BAT and Stolle) and he mainly uses the bolt lift signs in his load development, and not initial resistance. With each charge weight increase he gets up off his seat at the bench, and slowly raises the handle and tries to feel the slightest resistance at the top of the lift, the 'click' with new and FLS brass that chambers easily. If he feels the slightest resistance, the load is at its limit / is too hot. Only after this test does he look at the primer, but once loads are warm, there's usually nothing to see as pressures rise further.
The other test is case life. Pressures that see the primer pocket slack after only two or three firings may not be excessive, but they are 'hot' for that case.
One problem with modern rifles using high quality custom actions is that the traditional pressure signs are either muted or only appear when you're running at proof-level pressures - primers looking only a 'bit flat', no primer cratering because the pin to bolt fit is so close etc. So, there are no simple rules now and there may be a big difference in signs depending on what you're shooting. I have a friend who only uses high quality strong actions (BAT and Stolle) and he mainly uses the bolt lift signs in his load development, and not initial resistance. With each charge weight increase he gets up off his seat at the bench, and slowly raises the handle and tries to feel the slightest resistance at the top of the lift, the 'click' with new and FLS brass that chambers easily. If he feels the slightest resistance, the load is at its limit / is too hot. Only after this test does he look at the primer, but once loads are warm, there's usually nothing to see as pressures rise further.
The other test is case life. Pressures that see the primer pocket slack after only two or three firings may not be excessive, but they are 'hot' for that case.
Buy one of the Hornady/stony point chamber length gauges with the appropriate caliber insert to measure the datum line of your cases' shoulder area. If you full length re-size down to SAMMI specs you should not have a problem any longer.
To avoid this problem and increase your consistency, you could try to introduce annealing into your reloading practice. I have found that it gives me outstanding round to round consistency. I have some cases that have been reloaded upwards of 15+ times and I have no sign of fatigue or stress. To date I have had no cases fail me since I have started this practice. Not to be brag, but my reloads all hold 1/4 minute of angle accuracy. Your case prep is the corner stone of accuracy and by annealing you avoid one of the biggest accuracy killers, variances in neck tension. Annealing returns your case necks to a more consistent form. Therefore, when you full length re-size, your cases will all have similar neck tensions and dimensions because all your brass will be, in terms of metallurgy, very similar. All you have to do is trim, camphor, full length re-size, and load.
To avoid this problem and increase your consistency, you could try to introduce annealing into your reloading practice. I have found that it gives me outstanding round to round consistency. I have some cases that have been reloaded upwards of 15+ times and I have no sign of fatigue or stress. To date I have had no cases fail me since I have started this practice. Not to be brag, but my reloads all hold 1/4 minute of angle accuracy. Your case prep is the corner stone of accuracy and by annealing you avoid one of the biggest accuracy killers, variances in neck tension. Annealing returns your case necks to a more consistent form. Therefore, when you full length re-size, your cases will all have similar neck tensions and dimensions because all your brass will be, in terms of metallurgy, very similar. All you have to do is trim, camphor, full length re-size, and load.
what is 'camphor'?
Camphor is a strongly aromatic waxy substance. The poster meant "chamfer." Typing fast leads to problems.
DennisH
Life Time NRA member
I just finished FL sizing and "trimming" my brass which hopefully is causing my heavy bolt lift, after measuring my brass, some case were a little long! I will know this weekend if this made a difference on my rig! I have been shooting the same load for over a year now, so it's got to be something with the brass.
The more I read, the less I believe
thefitter said:sleepygator said:
Now you tell me. I've been rubbing Vicks on my cases all night!
Well, it sure will break up any congestion.
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