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Old September 24, 2021, 12:31 PM   #1
robinny
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How quickly does heavy bolt lift manifest itself?

I'm working up a load for my Winchester XPR .243 using Sierra 60 grain HP (#1500) bullets and Varget powder. So far my groups have been less than stellar, and someone has advised me to keep increasing my charge weight a bit more since I have not exceeded book max. His advice was to go up until I hit some heavy bolt lift and then back off. I've always stayed away from max loads, so I've never experienced the dreaded SBS (Sticky Bolt Syndrome).

My question is this; how quickly does case extraction go from normal to "needed a hammer to lift the bolt?" If I'm going up in 0.3 grain increments, am I going to notice some slight stickiness before I hit real problems, or could it go from nothing to problem status in one charge increment?
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Old September 24, 2021, 12:48 PM   #2
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If varget powder is not working out different power. Sometimes that can make a big difference.
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Old September 24, 2021, 01:51 PM   #3
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I've never gotten that kind of advice. READ YOUR PRIMERS! The mojo in your recipe just isn't working, try a different powder, primer, or brass. Trying to gauge what all is going on when pressures get high enough to cause bolt lift/extraction problems is just bad juju and borderline dangerous. Nobody without a vast array of scientifical gizmos and gagetries can tell you what those pressures are doing when things get sticky- nor can anyone tell you that the very next increment will cause a rupture somewhere. With modern metallurgy, sheared bolt lugs are kind of rare so it would be a blessing if the case simply ruptured... but what if the whole action turns loose on you?
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Old September 24, 2021, 01:57 PM   #4
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Primers can be inaccurate. If you pay attention, and it depends on the cartage and rifle, you'll notice the bolt getting a bit tougher to open. Usually in .3 increments, one shot will take 2 fingers to open the bolt, next 3 or 4, not needing to brake cheek weld, then needing to get my palm under and pry a little. If I get that far, that's too much for me. Temperature will play a factor too. If I'm working on a target load in winter that I'll run at matches through the summer, I'll stop sooner.

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Old September 24, 2021, 02:13 PM   #5
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I don't own a 243. I can't speak from experience. A 60 gr bullet is on the light and short end of the spectrum. The cylindrical portion of the bullet will be very short. I won't say that bullet cannot shoot,but it may be sensitive to being loaded straight and to whatever seating depth works. It may be finnicky.
I do not know what twist you have. Short/light bullets generally work best with slower twists. The 243 is usually twisted for deer weight bullets.
I will assume you are going for extreme velocity. Its likely a 60 gr bullet has a thin varmint or target jacket. If you have a 9 in twist and are approaching 4000 fps,you are approaching 5000 revs per second,or 300.000 rpm.
Centrifugal force can distort the bullet.

Goals like accuracy are not necessarily easily found in the extremes.

I might try a longer/heavier bullet. With that a step slower powder may be a good idea
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Old September 24, 2021, 02:19 PM   #6
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… I've never gotten that kind of advice. READ YOUR PRIMERS!…
Or not….

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Old September 24, 2021, 03:13 PM   #7
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If the groups are less than stellar (your words), then look for another suitable powder for the bullet. Just have to start all over and see what the next powder will do. Sticky bolts can go south on you quickly to where you can't open the bolt w/o a lot of effort or worse.
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Old September 24, 2021, 04:21 PM   #8
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Switching powder is a definite option. IMR4350 has shot well in this gun with 75 grain bullets, so I probably should have started there. I figured since I was moving to the lighter bullets I'd try a faster burning powder, plus so many people rave about Varget I thought I'd give it a whirl. I also have a jug of H4895. Sierra lists all three in their data. Their "Accuracy Load" is 37.6 grains of Benchmark, which is faster burning than any of the three I have.

Primers have shown no flattening or cratering at any charge weight between 40.5 and 43.0 grains.

Accuracy is more important to me than velocity. This load will be used on whistle pigs and paper out to a max of 200 yards. Barrel is a sporter contour with 1:10 twist rate.

Last edited by robinny; September 24, 2021 at 05:19 PM.
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Old September 24, 2021, 05:53 PM   #9
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Reading primers is probably not the best way to judge pressure because it's usefulness is limited to the primer pocket. A slightly looser pocket will shoe apparently higher pressure.
I use a chronograph when working up new hand loads. FWIW, I load in half grain increments usually with the start load and a new powder or cartridge. I watch the velocity as the charges increase looking for any deviation from the linear rat of increase. When I first started this method I plotted the charge vs increase on graph paper until I had a solid picture of what was happening at each increase in powder charge.

My system is based on pressure rises on a linear basis when powder charges are within the design parameter of the specific powder. Say velocity increases about 80 FPS per increased plus or minus 20 FPS. per half grain increase. When approaching the max load from the book is when the deviation may or may not show up. Depends on your rifle. However let say at one grain below book max velocity takes a major jump in speed, or actually has a drop in speed or no change at all, then you have reached, actually passed the upper parameter of that powder. You may or may not feel some stickiness in bolt lift but it's time to drop back about a grain to a grain and a half and call it the max for your rifle. Case in point, I have one rifle, a 30-06 that will show pressure signs two full grains from what is shown in the manuals. It happens.

Is my system perfect? Hell no but I've been using it for about 15 or more years and no problem regarding too high pressure. Brass life is good. Primers look good as well. Yeah, I still look at them but take then with a grain of salt. More force of habit than anything else as I've been reloading ammo since 1954.
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Old September 24, 2021, 06:12 PM   #10
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I'm thinking that depending on the rifle twist of your barrel it does not like those light bullets. If the different powders as some have suggested do not produce your desired results you many just need to try heavier bullets that your rifle will like.
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Old September 24, 2021, 06:32 PM   #11
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Forget primers (unless completely flat)
Forget twist issue (pressure-wise at least)

Note also that the XPR is particularly unforgiving on sudden sticky extraction
once pressure is exceeded (not dangerous so much as truly hard to extract)

Watch out for shiny brass flow marks as first reliable excess pressure indicator.
https://www.primalrights.com/library...nding-pressure

Realize at that point that you're at 75,000psi(+) -- so don't even think about
following the advice of "... to go up until [you] hit some heavy bolt lift and
then back off..."
as good counsel.

.

Last edited by mehavey; September 24, 2021 at 06:38 PM.
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Old September 24, 2021, 07:45 PM   #12
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Quote:
Originally Posted by mehavey View Post
Note also that the XPR is particularly unforgiving on sudden sticky extraction
once pressure is exceeded (not dangerous so much as truly hard to extract)
Good to know. I had not heard that before. If it's true, and discretion being the better part of valor, I'm thinking it's time to see how one of my other two powders perform with these bullets.

Quote:
Originally Posted by mehavey View Post
Watch out for shiny brass flow marks as first reliable excess pressure indicator.
This gun makes extractor marks on the cartridge at starting loads, so that's a tougher one to use as an indicator in this instance although I do compare the cases from each new charge weight to those of the previous one to see if the marks become more prominent.
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Old September 24, 2021, 10:56 PM   #13
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This gun makes extractor marks on the cartridge at starting loads
Are we talking bright shiny smeared/sheared brass, or just marks ?

http://www.primalrights.com/images/a...f_pressure.jpg
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Old September 24, 2021, 11:06 PM   #14
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Most of the time it's just the ( ) marks left by the ejector pin outline, but sometimes there's some swipe marks as well.
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Old September 25, 2021, 05:54 AM   #15
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Reading primers as pressure indicators is akin to reading coffee grounds at the bottom of the cup.
Its mostly about jumping to conclusions over inadequate and incomplete data.

What primer manufacturer considers handloaders reading primers as part of the Quality Program? Where in the process are primers calibrated to "look like this" at various pressure ranges?
OK,I'll grant that the manufacturers do control for consistency,safety,and performance... but I'm confident they give zero consideration to encouraging Reloader Joe to look at his primers and guess " Yup,that ring tells me 67,340 psi"
It does not happen.

There are other factors that figure in to fired primer appearance. Examples?
What kind of support does the primer get during firing? What condition is the firing pin hole in the bolt face? What is the clearance around the firing pin? Condition of the firing pin tip? How strong is the striker spring? Have the pockets had a crimp removed?
Head clearance is a big one. How far do the primes get pushed out before they get re-seated against the bolt face?
Ive seen some remarkably "flattened" primers out of a Glenfield lever 30-30 shooting factory loads. Does it matter that it had about 1/32 in excessive headspace?

All that said....I DO look at primers when load developing. I DO feel bolt lift.
I DO feel recoil and hear report. I DO look at the chronograph.
I notice decapping and priming effort...

When I am driving a vehicle or running a mill or lathe or grinder or grilling a steak or frying breakfast potatoes or trying to get along with a sweetie, its best if I keep ALL my senses open to inputs. Expected or not.

If you are trying to read a "track" every detail is part of a story.

Yes,look at your case heads. Do pay attention to "Thats different"

But do not fall for the idea your primers are a version of copper crusher units of pressure.

Particularly,don't fall for "Them primers gook good,Zeb,give her another couple of grains"
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Old September 25, 2021, 06:09 AM   #16
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A chronograph is only $100 and situations like this is why they are worth the money. By the time you start getting sticky bolt lift you are WAY over max pressure.

If your load manual says a max load will be 3000 fps with 45 gr of powder then the 3000 fps number is what you pay attention to. With individual rifles 45 gr of powder will match the books and give you 3000 fps.

But with other rifles you may reach 3000 fps at only 43 gr of powder and 45 gr may give you 3100-3200 fps and be a dangerous overload. In that rifle 43 gr is a max load.

In yet another rifle 45 gr may only give you 2900 fps. In that case it would be safe to increase powder above book max until you reach 3000 fps. But I strongly advise against doing so. If that ammo found its way into another rifle it could be dangerous.

I use a chronograph when developing loads and stop adding powder when velocity starts getting close to what the load manuals say should be the velocity I get with a max load. Or when I reach max powder charge. Whichever comes 1st.
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Old September 25, 2021, 07:10 AM   #17
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Trying to read the case at start loads can be tricky too.
I've noticed ejector marks at start loads on several different cartridges.
At low powder levels you can get some wierd pressure spikes.

I don't try to read primers anymore.

While a chrono is a good tool, i don't use one for load development.
I've seen barrels give faster velocities. And other barrels give slower velocities.
To the tune of about 150 fps.

I know of a lot of people that go over "book" max.
Also depends what book your using.
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Old September 25, 2021, 10:32 AM   #18
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- Several "official" load data inputs for bounding.
- QuickLoad
- Chronograph

I'm very comfortable wringing an unknown load out -- starting in the middle
for initial/baseline peg-point calibration.
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Old September 25, 2021, 11:32 AM   #19
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Reading primers as pressure indicators is akin to reading coffee grounds at the bottom of the cup.
Its mostly about jumping to conclusions over inadequate and incomplete data.

What primer manufacturer considers handloaders reading primers as part of the Quality Program? Where in the process are primers calibrated to "look like this" at various pressure ranges?
OK,I'll grant that the manufacturers do control for consistency,safety,and performance... but I'm confident they give zero consideration to encouraging Reloader Joe to look at his primers and guess " Yup,that ring tells me 67,340 psi"
It does not happen.

There are other factors that figure in to fired primer appearance. Examples?
What kind of support does the primer get during firing? What condition is the firing pin hole in the bolt face? What is the clearance around the firing pin? Condition of the firing pin tip? How strong is the striker spring? Have the pockets had a crimp removed?
Head clearance is a big one. How far do the primes get pushed out before they get re-seated against the bolt face?
Ive seen some remarkably "flattened" primers out of a Glenfield lever 30-30 shooting factory loads. Does it matter that it had about 1/32 in excessive headspace?

All that said....I DO look at primers when load developing. I DO feel bolt lift.
I DO feel recoil and hear report. I DO look at the chronograph.
I notice decapping and priming effort...

When I am driving a vehicle or running a mill or lathe or grinder or grilling a steak or frying breakfast potatoes or trying to get along with a sweetie, its best if I keep ALL my senses open to inputs. Expected or not.

If you are trying to read a "track" every detail is part of a story.

Yes,look at your case heads. Do pay attention to "Thats different"

But do not fall for the idea your primers are a version of copper crusher units of pressure.

Particularly,don't fall for "Them primers gook good,Zeb,give her another couple of grains"
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Old September 25, 2021, 06:27 PM   #20
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Quote:
Primers can be inaccurate. If you pay attention, and it depends on the cartage and rifle, you'll notice the bolt getting a bit tougher to open. Usually in .3 increments, one shot will take 2 fingers to open the bolt, next 3 or 4, not needing to brake cheek weld, then needing to get my palm under and pry a little. If I get that far, that's too much for me. Temperature will play a factor too. If I'm working on a target load in winter that I'll run at matches through the summer, I'll stop sooner.
I got with this as the best answer and add, use ALL indicators.

Where am I in regards to maximum is important (primer indicator at lower loads, take with a grain of salt)

But, do not forget EJECTOR wipe.

Ejector Wipe/Bolt Lift/Primer or Bolt Lift/Ejector Wipe/Primer.

If a Primer shows weird stuff as you are getting up high on load, then yes, it might turn into the leading indicator.
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Old September 25, 2021, 06:38 PM   #21
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Varget is a good powder. My Hornady shows it as one of the select powders for the smaller 243 bullets.

There should be good accuracy in a couple of nodes below max loads.

A 243 is a bit of a barrel eater so the lower you can run velocity the longer your barrel will last.

The 60 gr may want to be seated someplace different than the 75. Close or touch lands or backed off.
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Old September 25, 2021, 09:00 PM   #22
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I've fired 7.62 NATO proof loads in rifles that produce ~67,500 CUP (~82,000 psi) peak pressures. Folks who've seen the fired primed cases often say they look much like their own fired cases. Or a bit warm but still safe.

Bolts opened manually with normal force.

Last edited by Bart B.; September 25, 2021 at 09:09 PM.
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Old September 25, 2021, 09:22 PM   #23
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Originally Posted by jmr40 View Post
If your load manual says a max load will be 3000 fps with 45 gr of powder then the 3000 fps number is what you pay attention to. With individual rifles 45 gr of powder will match the books and give you 3000 fps.
I disagree!!!.

The powder and primer lots are different as well as the barrel length and interior diameters.

Last edited by Bart B.; September 25, 2021 at 09:35 PM.
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Old September 26, 2021, 12:40 AM   #24
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I think HiBC is dead on with both his post . Best to see the whole painting and not take one brush stroke as the be all end all of what’s going on with the load .

If benchmark is there accuracy load with that bullet . I’d test the H4895 next , light bullets and slow powders tend to be harder for me to tune . I really think the faster burning H4895 and the lighter bullet is going to shoot well .
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Old September 26, 2021, 11:13 AM   #25
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Quote:
Originally Posted by jmr40
A chronograph is only $100 and situations like this is why they are worth the money. By the time you start getting sticky bolt lift you are WAY over max pressure.

If your load manual says a max load will be 3000 fps with 45 gr of powder then the 3000 fps number is what you pay attention to. With individual rifles 45 gr of powder will match the books and give you 3000 fps.

But with other rifles you may reach 3000 fps at only 43 gr of powder and 45 gr may give you 3100-3200 fps and be a dangerous overload. In that rifle 43 gr is a max load.

In yet another rifle 45 gr may only give you 2900 fps. In that case it would be safe to increase powder above book max until you reach 3000 fps. But I strongly advise against doing so. If that ammo found its way into another rifle it could be dangerous.

I use a chronograph when developing loads and stop adding powder when velocity starts getting close to what the load manuals say should be the velocity I get with a max load. Or when I reach max powder charge. Whichever comes 1st.
That's really not right. It probably won't cause actual damage in most instances (won't go over proof level), but it isn't a way to control peak pressure except in one specific set of circumstances in which:

1. Your barrel is equal to or longer than the test barrel.
2. Your charge weight is equal to or higher than the published load for the velocity.

If you achieve the published velocity in the published test barrel length with LESS powder than the published charge for that velocity, then your peak pressure is higher than the published load's peak pressure was.

The above is not obvious, but here is the cause: When two bullets reach the same muzzle energy in the same barrel length, then the average pressure they experienced in the barrel starting from the chamber and including all the changing pressure levels averaged out over the bullet's trip down the tube and until it clears the muzzle. The peak pressure, which is the one we worry about for safety, is only a portion of that average, as is the muzzle pressure, and these don't change in proportion to the average pressure as you alter the powder charge. A given average pressure can be achieved by:

1.) A combination of a high peak and a low muzzle pressure, or,
2.) A combination of a low peak and a high muzzle pressure.

Low and high are relative in those statements, and in this case relative to the peak and muzzle pressures the load developer saw.

The first one happens when you get to a given databook velocity using a faster (higher burn rate) lot of powder, thus finding you need a lower charge to reach that velocity than the book listed.

The second one happens when you get to a given databook velocity using a slower (lower burn rate) lot of powder, thus finding you need a greater charge to reach that velocity than the book author did.

The above is true because, with low muzzle pressure, more of the bullet's acceleration has to be garnered from the peak pressure and less comes from later pressure levels in the barrel, meaning the peak has to be higher to get the bullet to the same velocity. A lower powder charge produces less gas and therefore lower muzzle pressure when expansion completes, so that's how you know its peak had to be higher to reach the same velocity. Vice versa applies as well.

What changes the relative burn rate can be differences in components, differences in your chamber dimensions, and, as I mentioned, differences in your powder lot's burn rate. Whatever the cause, the principle of peak to muzzle pressure ratios applies and you need to be warry of a velocity that is achieved with less powder in a same-length barrel or if you need the same amount of powder to reach the claimed velocity, but your barrel is shorter than the test barrel was. Either situation means your peak pressure is higher than the occurred in the load test.


Robinny,

An old rule of thumb has been that if you get a beginning hint of sticky bolt lift or sticky case extraction as part of a load work-up, you should back the charge down 5%. The sticky extraction sign applies to all types of firearms. That number should give you a sense of what those symptoms indicate and how far above the happy pressure range you are getting.

As to how fast the sticking event develops, it is generally in about half a millisecond from the time the powder burn gets seriously under way.
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