WHY is my first shot high?
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ironworkerwill
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I have good faith in my Lee scales. I have 2 electronic scales that wont hold a candle to the Lee. I will usually throw close to the target load then use a trickle to pin point.
It's bore condition on the first shot. Grease makes it more consistent. You push the junk out on the first shot, what ever that junk is, in a dry? bore. Good old coefficient of friction. If you consider that ~20% of the energy in each shot goes to heating the bbl, you will be surprised to see how hot the bore actually gets. Mosin doesn't do it cause it's an old well used bbl, i.e. more clearance between the bore and jacket.
ironwokerwill: Gee, maybe I am selling my Lee scales short! Have you compared them with the RCBS chargemaster scale? Everytime I weigh something known (like a bullet) on one of my digital scales, they come up exact. I write the weight of the little plastic cup on it, as a check, and it is perfect every time. So I had assumed the digital scales were good to 0.1 grain or better. I think the Lee is probably there also. Is one better than the other?
popper: Wow, I had never thought of that. Putting together what you point out with what hammer previously explained, and I think we are MUCH closer to understanding! I did some math, using Q=mC(delta T), [heat = mass time * specific heat * change in temperature, from high school chemistry ] assuming a 1.5kg barrel of chrome-moly (.456J/g deg C). A 2000 ftlb bullet is 2700 J I found, and taking 20% of this I found that the barrel might gain 1 deg C per each shot. That seems reasonable, in fact it might be more than that, so indeed, 20% -- or more -- of the energy is going into the barrel!! If the coefficient of friction is altered by dried-out carbon residue, then it could be significantly more friction. That agrees with a lower velocity measurement I found on one shot. The grease would reduce the coefficient I would expect.
I checked, and yes, smokeless gunpowder [smokeless means products are almost completely gasseous, whereas black powder products maybe 50% solids] does have hydrogen and oxygen --hence should produce water (vapor). That means any unburned powder or ash (although minute, but present, we know, from patching our barrels) will have some water component -- which could become drier or wetter over time depending on ambient humidity---and thus change the initial friction.
A change of velocity of 50 fps (similar to what I've observed on 1st shot) is on the order of 100 ft lbs, or maybe 150 J. If the barrel is already absorbing 500 J or more, it is very reasonable to think that there could be a change in the coefficient of friction sufficient to change that energy loss to 600 or more J due to dried residue!!
So this is making a lot more sense.
Grease, with a lower vapor pressure, lasts a lot longer than oil. I'm wondering what would happen if I ran a lightly greased patch through the barrel after every shot (to remove the ash products and leave a consistent film) and repeated within a few hours of the first shot of the day. Wonder if that would make the coefficient of friction similar for every shot???
The Mosins get shot with anything from very loose (.308) to tight (.311) to very tight (.312) bullets.....but having put a BUNCH of bullets thru them, perhaps they are more lapped???
And some barrels might have a better lapping, or be shot with different powder making different ash -- and some with tighter or looser bullets -- this may explain why some barrels see higher or lower velocities.
Now I still don't understand why a LOWER velocity makes for a HIGHER bullet....but maybe I am on a different node and the barrel ring explains it?????
And some barrels might have a better lapping, or be shot with different powder making different ash -- and some with tighter or looser bullets -- this may explain why some barrels see higher or lower velocities.
Now I still don't understand why a LOWER velocity makes for a HIGHER bullet....but maybe I am on a different node and the barrel ring explains it?????
ironworkerwill
Member
Doc I've never used the Chargrmaster. But, I don't have full confidince in powder throwers for precision shooting. They will be close enough for hunting or plinking and usually do well for pistol. Consistancy, however, is what we want for those one hole groups. I weigh every thing. To the 1/10gr or better on powder and bullets, then within reason on brass. Brass is sorted on number of uses, brand, and method of sizing.
Confidence is a factor in shooting. There are very good beam scales available that you may feel more confident using. RCBS, Lyman,and Hornady all make good ones and they look more like precision tools, unlike the plastic Lee. The analog beams will be close to the arrow and not "spot on" and one individual grain of powder may make the difference getting the marks to align. My digital scales will not notice one individual grain. As both digital scales are accurate to .1gr and one individual grain weighs less than .1grain it is not designed to read such a small ammount.
I got my first digital scale(elcheapo) for speed and soon realized it would not weigh the check weight consistantly to .1grn. I now use it for brass. The second digital(brand name)scale will weigh the check consistantly but it is a liar.
I've never had a box of sierra bullets (my usual brand)that were all exactly the same weight. They vary +-.5gns as a whole 100ct box. Such as the last batch of game kings. The heavy side was 160.4 and light 160.0 and there was close to 40 bullets that weighed 160.2.
Confidence is a factor in shooting. There are very good beam scales available that you may feel more confident using. RCBS, Lyman,and Hornady all make good ones and they look more like precision tools, unlike the plastic Lee. The analog beams will be close to the arrow and not "spot on" and one individual grain of powder may make the difference getting the marks to align. My digital scales will not notice one individual grain. As both digital scales are accurate to .1gr and one individual grain weighs less than .1grain it is not designed to read such a small ammount.
I got my first digital scale(elcheapo) for speed and soon realized it would not weigh the check weight consistantly to .1grn. I now use it for brass. The second digital(brand name)scale will weigh the check consistantly but it is a liar.
I've never had a box of sierra bullets (my usual brand)that were all exactly the same weight. They vary +-.5gns as a whole 100ct box. Such as the last batch of game kings. The heavy side was 160.4 and light 160.0 and there was close to 40 bullets that weighed 160.2.
Ordered some lock-ease from amazon. I'm testing so many things at the same time, I'm not sure what I'll get to it but it makes sense. From what I read it is a graphite product. Basically carbon.
As far as the beam scale. It really makes sense that I might pick up a really nice being scale, Maybe an rcbs. What I don't understand, is why it makes so much difference? On my digital scale, I think I counted and about six granules of Varget equals one 10th of a grain. Don't quote me on that, I'm just trying to remember. So I won't argue for a minute that my digital scale could easily be off by one half of one 10th of a grain, or maybe even a 10th of a grain. But you guys have me doing this optimal charge weight. The data from the previous tests, see pictures above, shows that 4/10 of a grain made less than a quarter inch difference at the optimal position. For hunting, I would like to be under an inch, and always ALWAYS under an inch even on the first shot. So, can you help me understand why a tenth of a grain error is that important? Additionally, I've read on several benchrest threads, that people use throwers or digital. I've got a six PPC Benchrest that will group around 3/8 of an inch or better using a thrower. So?? Not trying to be argumentative, just trying to understand. Those RCBS beams sure look nice!
As far as the beam scale. It really makes sense that I might pick up a really nice being scale, Maybe an rcbs. What I don't understand, is why it makes so much difference? On my digital scale, I think I counted and about six granules of Varget equals one 10th of a grain. Don't quote me on that, I'm just trying to remember. So I won't argue for a minute that my digital scale could easily be off by one half of one 10th of a grain, or maybe even a 10th of a grain. But you guys have me doing this optimal charge weight. The data from the previous tests, see pictures above, shows that 4/10 of a grain made less than a quarter inch difference at the optimal position. For hunting, I would like to be under an inch, and always ALWAYS under an inch even on the first shot. So, can you help me understand why a tenth of a grain error is that important? Additionally, I've read on several benchrest threads, that people use throwers or digital. I've got a six PPC Benchrest that will group around 3/8 of an inch or better using a thrower. So?? Not trying to be argumentative, just trying to understand. Those RCBS beams sure look nice!
ironworkerwill
Member
I have a feeling that you're doing right by getting a new tube. Some factory barrels are more forgiving than others. Buy 2 identical rifles and chances are one will shoot better with a specific load than the other. As well, one will be more forgiving as far as charge consistancy, type of powder, bullets ....ect. One barrel could have been chambered with a new reamer and the other with a reamer thats about to be worn out but is within tolerance. The list goes on.
In summary, the pickey rifle will make you a better handloader.
In summary, the pickey rifle will make you a better handloader.
balderclev
Member
This is an excellent article about accuracy from the experts.
http://www.angelfire.com/ma3/max357/houston.html
http://www.angelfire.com/ma3/max357/houston.html
Jesse Heywood
Member
I am not an expert on accuracy. If I hadn't gone to kindergarten I couldn't spell it!
My thought is that you need to stop making multiple changes. The only way to prove anything scientifically is to make only one change at a time. It seems like the long way to figure out a problem, but patience is a virtue.
Lock-eze is simply graphite powder suspended in an evaporative carrier. The carrier dissolves the gunk in the lock tumblers and the graphite is a dry lubricant. Most hardware store carry Lock-eze. A patch with a little solvent followed by a dry patch with a little dry graphite should do the same thing, Lock-eze would make it a little easier.
My thought is that you need to stop making multiple changes. The only way to prove anything scientifically is to make only one change at a time. It seems like the long way to figure out a problem, but patience is a virtue.
Lock-eze is simply graphite powder suspended in an evaporative carrier. The carrier dissolves the gunk in the lock tumblers and the graphite is a dry lubricant. Most hardware store carry Lock-eze. A patch with a little solvent followed by a dry patch with a little dry graphite should do the same thing, Lock-eze would make it a little easier.
The .308 Hornady Match cases I ordered (when they showed on Midway site) are on their way. Midway is now showing "out of stock, no backorder" unknown next availability.....
I did find military brass from www.brassreload.com with various grades and prices, and AVAILABLE. I'll use that to help out friends. Holding a "reloading " party has become the hit thing to do in my church.
I did find military brass from www.brassreload.com with various grades and prices, and AVAILABLE. I'll use that to help out friends. Holding a "reloading " party has become the hit thing to do in my church.
ironworkerwill
Member
Norma makes really good 7-08 brass. I think it is around $28 (25 count),when you can find it.
Nice link Balderclev!
Nice link Balderclev!
ngnrd
Member
Just a quick logic check here, guys.
Does it make any sense to go through all the machinations of working up loads and trying to decipher the "first shot high" issue, if a different barrel is going to be installed anyway? Just seems like a waste of components to me.
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Multiple changes are a problem, agreed. The advantage here is that I can try the Lock-eze on the first fouler shot and by the 4th fouler, it won't matter and I can continue the OCW process recommended by another writer.
You're probably right that I could have found lockeze at a hardware store. Dumb me. But it is coming.
As for worthiness of investigating -- yeah, I wouldn't put TOO much effort here, but I am learning and I have a bunch of other rifles that could benefit from anything that I figure out here! This rifle has always given me more fits, and I figured I had little to lose by experimenting on this bore. Thankfully I have relatively abundant components (am actually bringing up multiple new reloaders up to speed at same time). New barrel expected around June 1, so we'll see what I learn by then. If we figure this one out, then it may be useful to someone else among my friends.
ngnrd
Member
That's reasonable, I suppose. Good luck with the diagnosis.
Andrew Leigh
Member
Yes,
nobody knows definitively if the barrel is poor and secondly working up loads is an art that needs to be practiced and honed. Already the method being employed has discounted some loads and homed in on a load producing 0.5" groups, nothing to be sneezed at.
The OP is also experimenting with a different load development method. If found to be unacceptable then this method will be discarded, if good this routine will add value to his shooting experience.
ngnrd
Member
True. But we do know that the barrel is going to be replaced. And changing the barrel will certainly change how the rifle shoots. So, I would think that new load development would be necessary for the new barrel.
And, while I agree that gaining knowledge about load work up in general is important, I didn't see any real benefit in doing a workup for this particular rifle, only to have to start over when the barrel gets swapped out.
But, docsleepy wants to do it. And, who am I to judge how he uses his components and his time? I just thought I'd throw it out there.
Carry on. Nothing to see here.
1. Unable to find Lock-ease at Lowes (surprised me!), some is on order from Amazon. I will try to dissolve some lock graphite into some Butches Bore Cleaner or something similar. It might dissolve in rubbing alcohol. All I need is some vehicle to carry it and then vaporize. If that doesn't work, I'll try the two-patch idea.
2. Gee, if I could get this barrel to WORK, it might be useful to me or to a friend who has a savage gun of any type.
3. The reason I decided to embark on this investigation was that I had worked with this barrel for twelve months, and I was very familiar with a very repeatable first shot problem. If THIS barrel could be made to work better, I would have a huge knowledge tool at my disposal to assist in other guns where changing the barrel isn't so much of an option! I would probably try the same solution on higher-caliber AR's and see if they got even better.
4. I'll anneal some brass, create the loadings and if possible get some tests done tomorrow before it heats up here. No clue whether I'll be able to get the chrony to work, it is supposed to be sunny.
5. The "first shot" tests will be separated from the "OCW" tests by several foulers, so they should be relatively independent tests. As andrew suggested, I'll use the hotter loadings for the foulers. Sure would be nice if I could get at least some accurate chony readings.......
6. I got in some once-shot military .308 brass, but am still waiting on more Hornady .308 Match (my preferred).
2. Gee, if I could get this barrel to WORK, it might be useful to me or to a friend who has a savage gun of any type.
3. The reason I decided to embark on this investigation was that I had worked with this barrel for twelve months, and I was very familiar with a very repeatable first shot problem. If THIS barrel could be made to work better, I would have a huge knowledge tool at my disposal to assist in other guns where changing the barrel isn't so much of an option! I would probably try the same solution on higher-caliber AR's and see if they got even better.
4. I'll anneal some brass, create the loadings and if possible get some tests done tomorrow before it heats up here. No clue whether I'll be able to get the chrony to work, it is supposed to be sunny.
5. The "first shot" tests will be separated from the "OCW" tests by several foulers, so they should be relatively independent tests. As andrew suggested, I'll use the hotter loadings for the foulers. Sure would be nice if I could get at least some accurate chony readings.......
6. I got in some once-shot military .308 brass, but am still waiting on more Hornady .308 Match (my preferred).
Here are the data from today.
Reloads:
1. Had to toss another 4 cases for incipient head separation discovered with bent paper clip.
2. Moved FL sizer maybe .002-.004 tighter based on measurements suggesting I was bumping shoulder back .005 (more than necessary)
3. As before, annealed, dried, lubed, FL sized, trim, chamfer, smooth, neck size, prime, charge (Varget, Chargemaster), seat. Press closed twice on seater die (found this makes for more consistency) and then all bullets checked with Hornady 0.28" comparator, 2.260-2.265 tolerance. 2 or 3 were long, once more in the seater die and they shorten up nicely by a couple or 3 thousandths.
4. Clean off lube.
Shooting:
100 yards, 80 F at start, 85 F at finish, took breaks between each "round robin" sequence. 16X scope, Rock BR front rest, rear leather bag, firm hold into shoulder pocket, forend in U-shaped wooden "shim". Foulers fired until two at approx same level. Foulers 42.8 grains Varget. Thankfully, there was some cloud cover and it was before noon and my Chrony was in some shadow and it WORKED!
Cleaning:
Mixed Hoppes 9 and lock graphite in small container, soaked a patch, ran down bore (bore guide) multiple times. Then put graphite on a dry patch, ran THAT down bore (bore guide) multiple times. Then used short rod and clean patch to clean chamber of any material.
There was variable wind in the 5mph range.
Displays:
Foulers are at left hand frame
Inch marks are visible in all targets
Red dots mark what I think is the geometric center of acceptable shots in each powder test
Composite geometric centers on the far right.
Measured velocity is right beside each shot.
NOTE: I had three rounds of ammo that were clearly not quite FL sized enough and closing the bolt required a push. I have marked these shots with "starburst" and because they uniformly shot LOW I have eliminated them from consideration. I think I've seen this before with this barrel, but these structured tests really brought it out.
NOTE: primer flattening increased noticeably at each higher charge and slight "volcano cratering" of the primer indentation occurred at the two highest charges.
Reloads:
1. Had to toss another 4 cases for incipient head separation discovered with bent paper clip.
2. Moved FL sizer maybe .002-.004 tighter based on measurements suggesting I was bumping shoulder back .005 (more than necessary)
3. As before, annealed, dried, lubed, FL sized, trim, chamfer, smooth, neck size, prime, charge (Varget, Chargemaster), seat. Press closed twice on seater die (found this makes for more consistency) and then all bullets checked with Hornady 0.28" comparator, 2.260-2.265 tolerance. 2 or 3 were long, once more in the seater die and they shorten up nicely by a couple or 3 thousandths.
4. Clean off lube.
Shooting:
100 yards, 80 F at start, 85 F at finish, took breaks between each "round robin" sequence. 16X scope, Rock BR front rest, rear leather bag, firm hold into shoulder pocket, forend in U-shaped wooden "shim". Foulers fired until two at approx same level. Foulers 42.8 grains Varget. Thankfully, there was some cloud cover and it was before noon and my Chrony was in some shadow and it WORKED!
Cleaning:
Mixed Hoppes 9 and lock graphite in small container, soaked a patch, ran down bore (bore guide) multiple times. Then put graphite on a dry patch, ran THAT down bore (bore guide) multiple times. Then used short rod and clean patch to clean chamber of any material.
There was variable wind in the 5mph range.
Displays:
Foulers are at left hand frame
Inch marks are visible in all targets
Red dots mark what I think is the geometric center of acceptable shots in each powder test
Composite geometric centers on the far right.
Measured velocity is right beside each shot.
NOTE: I had three rounds of ammo that were clearly not quite FL sized enough and closing the bolt required a push. I have marked these shots with "starburst" and because they uniformly shot LOW I have eliminated them from consideration. I think I've seen this before with this barrel, but these structured tests really brought it out.
NOTE: primer flattening increased noticeably at each higher charge and slight "volcano cratering" of the primer indentation occurred at the two highest charges.
Attachments
COMMENT ON INADEQUATELY FL SIZED CASES:
Wow, normally one expects "tight" cases to be MORE accurate! I'm guessing that this means there is some error in my cheap barrel's chambering -- some assymmetry in the shoulder-to-bore alighnment or something.
My conclusion is that I'll probably re-adjust the FL sizer back down .002" to be certain that the bolt can easily close on all cases, because this seems to be a huge effect!
Wow, normally one expects "tight" cases to be MORE accurate! I'm guessing that this means there is some error in my cheap barrel's chambering -- some assymmetry in the shoulder-to-bore alighnment or something.
My conclusion is that I'll probably re-adjust the FL sizer back down .002" to be certain that the bolt can easily close on all cases, because this seems to be a huge effect!
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