Old-Win

I'm not a Shuetzen shooter either and like you, I respect the accuracy that they are able to achieve.  As to the reason for shallow grooves on Shuetzen bullets, I'd like to propose the following reason as a possible answer.

Back at the turn of the 20th century, Ideal offered their "Perfection Mould" to shooters which allowed the shooter to cast various weights of bullets having different lengths.  Depending upon the caliber, the number of different bullets that could be cast with the mould ranged between four and seven.  Some of those heaviest bullets were quite long.  This was great for a Shuetzen shooter because he could try different weights and select the bullet that performed best in his rifle.

I've got to believe that cutting all those grooves in a long bullet was hard on the tool steel cherie that they used to cut the iron mould.  I suspect that to reduce springing of the cutter and to increase tool life, they made the grooves shallow as a manufacturing expediency.  Since the bullets provided good accuracy, other mould makers imitated their pattern of shallow grooves.

Does that seem to be a logical explanation?

feather

Pete,

I agree with you with respect to the more narrow and shallower depth of grease grooves for use with smokeless powders. Actual testing has shown that a 32 caliber bullet having only 2 narrow and shallow grease grooves (.040 wide x .016 deep round bottom) carries adequate lube when fired at 1550fs. Although we make moulds with 3, 4, 5 and 6 grooves, many shooters are using our 3 groove bullets with no reported leading problems. Comparing two identical bullets cut with the same cherrie one with 3 grooves, one with 5 grooves, the 3 groove bullet will have slightly higher retained velocity at the target than the 5 groove, this is due mostly to the increased weight of the 3 groove. Again, this applies to smokeless powders only.

Exhaustive testing has proven that a 16 inch twist 32 caliber barrel can stabilize bullets upto 1.165" long at 1475fs. As you know increasing the weight of a bullet will improve its ability to retain its downrange velocity. However I must point out that the larger metplat will most often offset any increase in weight due to increased aerodynamic drag. For instance, tests comparing a 191 grain 6r ogive spitzer vs a 210 grain 5r ogive spitzer (same length) have shown the 191 grain spitzer bullet has the better retained velocity and faster time of flight. The differences change rapidly beyond 100yds. I have tested and profiled most of the 32 caliber bullets we offer instrumentally in 25yrd increments to 200yds. In my opinion nose form factor is more important than weight alone.

7~

Barry,

  I agree with your assessment about the number of lube grooves actually required with smokeless powder. In fact I said about the same thing in another thread.

  What would you say to the same reduction of lube when shooting BP if you wiped between shots? I think the same as with smokeless but haven't done any side by side comparisons to say. Just a gut feeling. So am open to other opinions.

  I think you could go down to even less than 3 lube grooves if you wanted. As I've mentioned a Lyman 311334 with two lube grooves and being driven at pretty close to 1500 fps hasn't shown any Leading. I have taken it up to 1785 fps with no Leading, but there's no accuracy. Alloy is 50/50 WW/Pb. The problem(?) with this bullet is that it's about 2/3rds bore riding, so I'm not sure if this amount of lube would prevent Leading if the bearing surface was longer. Your thoughts?

  So far what I've found is that different calibers and bullets require different amounts of lube. My main .32/40 bullet shooting smokeless, which is a Barnett copy, does best with all grooves full, and a Win. 185 gr. bullet shoots best with one less groove of lube.. The Lyman 457125 wants two grooves less and the 600 gr. bullet I use in my .50/90 needs them all full. The latter two are being shot with BP and the bore wiped out for each shot. What's your thinking on all this?

  I can see the increased meplat increasing drag and wouldn't recommend it as soemething to get. I was just using it as an example to show how bullet wgt. can be increased without increasing the length.

  I'm glad you mentioned the actual max. length that a 1-16" twist can handle. Didn't know that!

  Nose form factor....... Can you go into this in a little more detail? It seems to go against common sense that a 191 gr. bullet would have better retention of velocity... which should equate to a higher BC..... than the 210 grainer with only a 1 degree difference in the radius. It would seem that just the difference in wgt. would be enuf to offset that small a radius change. How big a difference are we talking here?

  Something I read recently says that at Schuetzen and BP velocities BC isn't affected all that greatly by nose shape. If BC isn't affected then I would think downrange ballistics wouldn't be affected greatly either. Playing with different BC's and a computer program I've found that it takes around 50 points difference in BC to see any realistic changes in trajectories, and remaining velocities. Confusing to say the least since everybody puts such great emphasis on it. But.....You've done some actual work on this, so would be interested in your thoughts?

  This is getting interesting! 

PETE

Barry,

  Excellent! Just what I was looking for from you. Someone who's done actual work. Computer programs are ok for a general overview but will never beat actual testing. In a lot of shooting cases close ain't good enuf.

  Looking at a chart of nose radius' (Coxe & Beugless) the difference between a 4r and 6r nose (closest my chart shows) is very small. In fact very hard to visually see the difference. This would lead you to believe that all else being equal..... as you point out your test setups were..... that the heavier bullet would be slightly better in all departments.

  Very interesting points you've made. Have you tried this with more radical differences in nose radius'? Say a 2r vs a 6r. If so, at what point will the results tip in favor of the heavier bullet?

  Then I get to wondering about a spitzer vs a flat nosed bullet. since a lot of people seem to think a nose pour bullet is better than a base pour, a true spitzer isn't possible. I wonder at what diameter the meplat would have to be before downrange results would be close enuf so that any differences wouldn't show up, just due to the "soup" of natural conditions acting on the bullet externally. Your thoughts?

  Changing Lead alloy affecting downrange efficiency...... Now this is a new one on me!

  Are you sure you don't mean a 1-20 bullet will weigh LESS than a 1-25 or 1-30? Tin being lighter than Lead any addition of Tin to an alloy should make it slightly lighter.

  In any event, do you have some velocity comparisons at the various ranges you test at to show this loss?

  Something that just popped into my head. I've read that some think a lube can be to slick. Have you done any  testing with different lubes to see if the various types cause differences in velocities?

PETE

Steve,

  I think it was mentioned that after the first shot, even if you wipe out, there will be some lube left on the barrel. If you shoot dirty, after the first shot, there would be plebty of lube and soft fouling to "grease" the way.

  Altho the following is also true of my .45/70 and .50/90 BP loads I'll use as an example the 417 gr. .40/65 bullet I'm working with now. Since I shoot almost every day during the Summer I just leave the bore wet with my cleaner and at the range just run a dry patch thru to get rid of the excess. Or, if I'm shooting the gun for the first time that year, I clean it, and then follow the same procedure at the range.

  With the above bullet the first shot will always be in the center of the group. Using a blow tube the successive shots will be around it. Now with that first shot there is no lube in the bore, yet the barrel doesn't Lead up. If it was Leading up then groups would get worse real fast.

  Now this isn't a rare occurence and part of balancing a BP load for me is to try and find a load that will do this. With BP it seems to work most of the time. With smokeless it doesn't. I wish I knew the why of that!

  The long way around is that personally I wouldn't worry about an unlubed nose being a detriment to accurate shooting. A bore slightly damp from your cleaner seems to be enuf lube for at least one shot.

  Now here's an idea I've read that some do. If this unlubed bore bothers you then some will run a patch with their lube on it back and forth several times down the barrel followed by a reasonably tight, dry patch to get rid of the excess. Seems to be a favorite trick of some of the top ML'ing shooters. They call it seasoning the bore.

  Take it for what it's worth as I've never tried it. If you do let us know how it works out.

PETE

Pete,

Yes I have done comparative ballistic tests with 2r ogive upto and including 8r ogive spitzers and comparisions of flat nose also. In each case the larger ogive radii bullets with metplats of .030/.050 dia. of similar weights have shown to have the better target velocities. The following is a partial list of tested bullets and their efficiency factors for 100 and 200 yds. Just as the BC is the same for each particular bullet at a given range the efficiency factor also remains esentially the same for a given range within the 1350fs to 1550fs velocity range we normally use for schuetzen shooting. Therefore, if you multiple your chronograph MV x the EF(efficiency factor) of a bullet that has been characterized the resulting down range velocity will be close to 1% of the actual downrange velocity. 

190grn Flatnose .115 metplat = .892@100yds .789@200yds
200grn Flatnose .115 metplat = .895@100yds .799@200yds
190grn Pope      .145 metplat = .882@100yds .773@200yds
190grn 6r Sp     .020 metplat = .905@100yds .804@200yds
190grn 3r Sp     .060 metplat = .881@100yds .769@200yds
200grn 8r Sp     .045 metplat = .912@100yds .823@200yds
210grn 5r Sp     .040 metplat = .906@100yds .808@200yds
216grn RdNose  .060 nose R   = .902@100yds .809@200yds

This comparision shows the effect of both nose form and weight on bullet efficiency or retained velocity. When conducting bullet tests I repeat previous tests again on different days, slight differences occur mostly as a result of barometric pressure more than other atmospheric conditions like temperature (65F-85F) or humidity.

With respect to what would be the best of both worlds, weight and nose form for a 16inch twist barrel, my current choice would be the 6r spitzer with length increased to 1.165. Further testing is still needed next season on some new designs that are a result of this past years work. I do beleive that the nose length can be too long resulting in unexplained flyers, this seems to be true of the 200grn 8r spitzer. This years test series consistated of over 5000 shots of 15 different bullets designs, pressure tests were also conducted on each bullet design/weight.

I suppose I could have worded the difference in alloy weight better, I meant to say that a bullet mould that casts a 200grn bullet with a 1 in 20 alloy will cast a bullet about 2grns heavier when a 1 in 25 alloy is used. The 1 in 25 alloy will have better retained velocity than the 1 in 20 alloy due to the 2 grains of weight.

Years ago I experimented with many different bullet lubes and can't say as if any were too slick. With smokeless powder powder fouling sometimes occurs and is mistaken for leading. This fouling occurs in the throat and occassionally about 14" from the throat where the peak pressure point occurs. I don't beleive bullet lube is as important for smokeless shooting as for BP.

Barry

Barry,

Ok! Good post. But, I need to get this efficiency factor straight in my head. Remember... I skipped school the day they had math.  In other words you're getting ahead of my understanding of your work and I sure do want to get a handle on it.

  Looking over your chart I'm trying to relate the efficiency to the numbers you give. I THINK the higher the number the more efficient. Right? If so, I get it, but if not I need some dumbing down about it.

  Atmospheric conditions....... Forrest Asmus and myself have been trying out the idea of using one "reading" of the conditions to see if we can't get a handle on retained velocity and it's effect on group size. Density Altitude is what we've been looking into. Rather than go over the whole thing we are trying to do, look up a past thread on this.

  Do you believe that Barometric pressure has more to with down range velocities than temp. and hunidity?

  We've all seen our rifles go "sour" in the middle of a match, for no reason we can relate to. I would think that barometric pressure would just be to slow acting to show these sudden changes. Using a Kestrel 4000 which will show you about any atmospheric condition you care to name, I'm beginning to believe temp. has the most effect on groups at least.

  Correct me if I'm wrong..... But isn't a lot of the barometric pressure you observe due in large part to temp. & humidity? If so then I would think that retained velocity would be more affected by these two factors. As the air warms in the morning the humidity will fall. As the humidity falls the air becomes more dense, and would retard a bullets flight more.

  I might be on the wrong track, but my observations so far this past Summer seem to show that about a 10 degree rise in temp. needs a corresponding decrease in powder charge in order to maintain velocity and accuracy. I'm talking smokeless here for those interested.... and not!

  So, I'd like to hear why you think Barometric Pressure is the more important factor to see if my thinking is correct or needs revision.

  I have read that the Creedmoor shooters kept a barometer, and humidicator in their loading tent. Altho not mentioned I would assume they also had a thermometer to.

  To slick bullet lubes..... I'm with you on this, but some seem to think if a lube is "to slick" the bullet can get ahead of the max. pressure wave when it's bumped by primer ignition. The thinking seems to be that you'll end up with the bullet traveling down the barrel with a Yo-Yo effect. Speeding up and slowing down as the pressure wave catches up and gives it a bump then slowing down as it gets ahead of the front. It's felt what's needed is the right lube consistency to act as a sort of drag so this doesn't happen. I'm not sure this would be applicable to BP as there is enuf drag induced by the fouling. More something that would affect smokeless loads.

  To prevent, or slow the primer bump it seems like a lot of BP shooters are going to the pistol primers.

  As an aside and FYI..... I've been looking down the muzzles of other competitors barrels.... unloaded of course  ..... and see what you mean. Also have used those observations to tell when I'm getting close to the optimum load. I wasn't to sure about that at first, but see your point now. Amazing the variations you'll see.

PETE

PETE

The efficiency factor (EF) is simply the percentage of retained MV at a given target range. For instance an EF of .804 is 80.4% of the MV (10ft from muzzle). An example an EF profile such as our #45 200grain flatnose bullet with a .115 metplat with MV of 1475fs is as follows: (Range EF times MV).
50yds  = .963 = 1420fs
75yds  = .932 = 1375fs
100yds = .895 = 1320fs
125yds = .873 = 1286fs
150yds = .845 = 1246fs
175yds = .822 = 1212fs
200yds = .799 = 1179fs
The EF's are constant for the 1350fs to 1550fs MV's that may be used for smokeless powder breech seated bullets. Each bullet has its own set of EF's for yardages in 25yd increments. By profiling each bullet design a more direct comparision can be made than by using the "standard Bullet" and "G1" drag function typically used. 

In addition to what I've mentioned before, extremely close velocity tolerance (+/- 5fs) were held for all test series, this also was an excellent way of detecting bullet instability or excessive yaw at downranges. With muzzle velocities held to +/- 5fs, a stable bullet will also yeild equally narrow downrange velocities, while bullets that are unstable will have erratic downrange velocities far in excess of the MV tolerance. While excessive yaw was not indicated with the 16" twist barrel, it was very apparent with a barrel with a 12" twist. Here the downrange velocities were within close tolerances, but retained velocity was about 5% less than when the same bullet was fired at the same velocity in the 16" twist barrel. This relationship of barrel twists will be explored next shooting season. SO MUCH TESTING-SO LITTLE TIME!!! Perhaps the oldtimers prefered 16" twist 32"s for 200 yard shooting for good reason? ???

Atmospheric conditions such as humidity, barometric pressure, temperature and altitude have an effect on ballistics, since my ballistic test equipment is computer based accurate data entry of these parameters is required to obtain meaningful results. They do not seem to play as big a role at 200 yards as I once thought. At longer ranges such as those fired by the BP shooters they no doubt play a more tangable effect. Since my tests required certain specified test velocities, slight tweeking of the powder charge was needed due to temp. changes, sometimes as little as .08 grains. I have not crunched the atmospheric data from this past seasons testing yet, so i can not quantify the various variables. If you are testing at longer ranges than I am, I'm sure they may be more apparent to you.

Barry

Barry,

  Thanks for the clarification on efficiency. I'm with you now.

  On excessive yaw and it's effect on downrange accuracy. I don't know if you have this problem with the .32/40 but every one in that caliber I've had always showed some tipping at 100 & 200 yds. I thought going to a lighter bullet SHOULD solve this problem, but it didn't. Your statement on this would suggest that lighter bullets than would be optimum for a given twist would cause more yaw. This seems to be the trouble when working up loads this past Fall for the .40/65. A nominal bullet (417 grs) for the twist worked up very easy, but going to a lighter bullet (313 grs) took quite a bit more work, and I was beginning to think I wouldn't make the accuracy level I wanted.

  Your comments on retained velocity loss with a quicker twist I'll certainly go along with. A bullet that yaws issubjecting more surface area to all forces that would retard it's flight and it's only reasonable that downrange velocity would be less than a bullet that was more stable. One of my pet peeves is people who say a little tipping is not detrimental to accuracy. As far as I'm concerned if you have to live with it, you do, but I want a stable bullet flight if at all possible and do all my load testing with that in mind.

  Yes.... A stable bullet will yield a stable downrange velocity spread, and that equates into better accuracy. Here's a question I think I know the answer to but would like your opinion to as I've about been told I don't know what I'm talking about. I have an original Win. High Wall in .38/55 with a 1-18" twist, and for bench shooting I use a 320 gr. Brooks bullet. At 100 & 200 yds. this bullet shoots fairly well, but shows a little tipping at 200. A gun I'm aware of in the same caliber, and cut with the same chambering reamer, shooting about the same wgt. bullet, but with a 1-15" twist, is lucky to shoot a 6" group at 200 yds. It is thought that a quicker twist is needed. I don't think so and with your statement on yaw and stability in twists I'm thinking a slower twist would be more useful. Your thoughts?

  Atmospheric conditions at short range. This is what I was trying to prove this past Summer. Forrest Asmus (FAsmus) uses Density Altitude  as a tool for setting sights when shooting out around the 800 to 100 yd. mark. I was curious if this would be a useful tool at Schuetzen ranges. This is gonna need a lot more work as the differences are small, if there at all. Wind, mirage, and personal sighting error are such that I'm not sure that any changes aren't being lost in other things. But, as I've mentioned to Forrest, it's pretty apparent that Temp. does have a noticeable affect on accuracy, and as far as Schuetzen shooting goes should be taken into account. If you ever do "crunch" the atmospheric conditions I hope you post them, as I think your testing eliminates the human error mine doesn't.

PETE

Hi Pete:  Yes, warm air does hold more moisture than cold air.  I'll try to make up an example here to show what happens to RH as temperature changes.  Keep in mind that these figures are not real because I don't have a chart but they should explain what's going on.   
Suppose we have a cubic meter of air at 80 degrees and lets say that the maximum amount of water vapor it can hold would be 40 grams at that temperature.  Now, if that volume of air had only 20 grams of water in it then it would have 20/40 (half of what it could hold) or 50% RH.  Now, let's suppose that at 60 degrees, the air is saturated with 30 grams of water.  If you take that same volume of air that we started with and drop its temp to 60 degrees, you now have 20/30 or 66% RH just by dropping the temp without changing the actual amount of water vapor in the air.   
Here's another thing that deals with the density of air.  When water changes to a gas, a water molecule actually weighs less than molecules of air made up of nitrogen and oxygen but take up the same space.   
As far as blow tubing goes, we've started shoots when the temps have been in the low 40's or even lower.  I only use about one breath to keep the fouling soft when we begin.  It doesn't take much for your breath to condense on a cold barrel.  As I continue to shoot, I keep grabbing the barrel to see how it's heating up and adjust to its temp.  I will be up to about 4 breaths by the time its quite warm.  When it gets so hot that I can only hold on to it for a second or two, I am up to six.  This is when things get interesting and I start losing the race.  Every shoot is different and I'm just getting enough experience to handle it.  At the Quigley,  I never clean my barrel all day because we only shoot 8 shots at a time and that is not enough to get the barrel hot.  The LR shoots are a different story because the barrel continues to get hot and you have to average a shot roughly every 1 1/2 to 2 minutes so it doesn't have a chance to cool between shots.  Even though BP residue is hydroscopic, when the barrel is that hot, I think the moisture is evaporting out of it.  My trouble has come up when the temps where in the upper 80's and RH in the 30% range.  Now, What about them lube grooves??   Bob

Old-Win,

  Your post on relative humidity was most interesting. Learned a lot I didn't know. Thanks!

  A question along this line, but totally irrelevant since you can buy instruments that give you the RH, but was the old method of using a wet and dry bulb just a different way of getting the same thing? I can remember my Dad making one of these up and as I recall there was a formula to use to get the answer. Always had it in my head this was a way of determining RH.

  Will have to keep your idea of grabbing the barrel to use as an indicator of blow tubing you need to do. What little I've read on the subject only differentiated between humid and dry conditions. As you know around here during "normal" shooting weather the humidity is above 50%, except on rare occasions. With my experience at the NCOWS match I didn't think of barrel temp. as being a consideration.

  About them lube grooves. Well, actually if you get down to it the last few messages are all about lube grooves and associated problems. You have to have enuf lube to make blow tubing practical. To little and no matter how much blowing you do it isnt gonna be enuf. To much and I personally feel that accuracy will suffer. As I pointed out, different bullets, different loads, and different guns require different amounts of lube..... and you might have to throw in different temp.'s and humidity. There probably is no one answer to the lube question and about all you can do is try to get something that will work for all conditions, knowing it's probably not gonna be best for any.

  You BP shooters might not be familiar with Claude Roderick, but the older Schuetzen shooters on here will be. He was considered one of the founders of modern Schuetzen shooting. I corresponded with him a year or so before he passed away. His thinking on lube was that you needed different tempers for different temp.'s, and sent me a whole page of variations that covered the range of temp.'s we shoot at. Of course this was for smokeless, but as we're finding out in these discussions it would also apply to BP. So, instead of only looking at various lubes and numbers of grooves, you can also look at various tempers in your lube. Feather is looking at harder lubes, but the question would be is if there is such a thing as a lube that will give best results in all temp.'s? Steve Garbe was questioned a while back on whether a variation on SPG would be of benefit over certain temp. ranges. His results showed that there was a slight difference between pan and machine lubing but basically the "old" formula worked the best.

PETE

Good morning, Pete;

You said, "Can I get off my knees now? They're starting to ache!"  Well.....

A soap is produced in the reaction between a fat and an alkali.  Grandma's lye soap is one good example.  The harshness of the soap is mostly due to an excess of the lye because you really don't want extra fat in your soap.

So far as the soap hurting the bore in the period of one day, I have never heard of any problem.  After all, the fouling is already in the bore and the soap film is between the fouling and the metal.

You have noticed that the patch is hard to push through with three breaths in cold dry weather.  I think this is a good example of the idea that you need more blowing in cold dry weather - both on the line and before cleaning.

Y'all be good.

horsefly

Good morning, Pete;

Sorry I didn't make the connection complete.  Most of the fouling left by BP is fly ash - an alkaline (basic or hydroxide) product.  If you leave fouling on a cleaning patch for several hours, it turns white.  It is not carbon.

Lye for soap is leached with water from ashes from the fireplace or stove.

Interestingly enough, when the fouling (fly ash) is fresh it is easily wettable and easily cleaned.  If you wait until it turns white, it becomes much harder and sticks to the bore much more and is harder to clean.

Y'all be good.

horsefly

Good morning, Pete;

Let me take another whack at it.  We agree, I think, that soap is the product of a reaction between an alkali and fat.  The fat is the layer of lube laid down on the bore.  The alkali is the BP residue laid down in the bore.  When you blow moisture down the bore, the alkali and fat are wetted and a chemical reaction takes place to form a crude soap.  Now you have a layer of soap between the remaining fouling and the bore.

You also said, "Since the carbon makes up a great proportion of the BP it should also be a large part of the residue."  You are right, it is.  But the burning reaction changes the carbon and the potassium nitrate into something else - the alkaline ash.

This chemical reaction stuff can be confusing if you are looking for the reactants to resemble what they were before the reaction.  For instance, if you react hydrochloric acid (strong acid) with sodium hydroxide (a strong base) you get salt and water.  You can drink it if you got the proportions right.  If you burn gasoline in the presence of oxygen, you get carbon dioxide and water.  Neither one of them resemble gasoline.

So, the point is, the carbon is there, but it is not going to act like you think elemental carbon should act.  It is in something new and different.

Y'all be good.

horsefly

PETE,

We are getting off subject on this thread I think.

Here are some of my thoughts regarding stability and yaw, right now they are just speculation on my part based on my obsevations doing two years of testing breechseated bullets.

Previously, I mentioned that when comparing the same bullets shot from a 16" twist barrel to them same fired from a 12" the downrange (200yd) EF was about 5% less with 12" twist. While this is true, groups shot with particular barrel shoots groups regularly under minute of angle (200yds). The 16" twist barrel also shoots sub-minute of angle groups with the appropriate velocity. I suspect that there are several conditions the occur during the bullets flight.
1. Random instability - a condition that causing extreme downrange velocity spreads.
2. Random yaw - the effect of this condition are the same as for #1
3. Repeating instability - this condition results in similar velocity spreads downrange as muzzle velocity spreads. This may explain why slight tipping is seen even on very small groups.
4. Repeating yaw - again this condition results are similar to #3
5. Stabilized and tangent yaw - perfection. The bullet spins about its axis and the nose of the bullet is tangent to the trajectory arc.
Next shooting season I plan to explore these conditions in more detail, using 16", 14" and 12" twist barrels.

With respect to your 38-55 x 18" twist barrel, when I was making barrels I also found that a twist faster than 16" in 38 caliber did not perform well at 100 or 200 yards. With the 18" twist, as I recall, a 300 grain bullet was performed best accuracy-wise. I beleive the faster the twist the more any inbalances in the bullet are amplified, which may be the result of your friends 15" twist. I made up a 40caliber barrel chambered for .405 with a 18" twist and have found that is capable of excellent accuracy at 200yds with a 375 grain bullet 1.350 long. A 415grain bullet showed slight tipping at 200yds, although accuracy was good, the recoil was not pleasant, recoil was more than 13 ft lbs. at 1525fs. Too much for this old fart, 50 shots a day is about all I want to tolerate.

Going back to this past seasons testing data, I checked the velocity difference between 60F and 82F of same bullet fired at the same MV = 12fs. This is the average of 30 shots each at 1500fs. The effect of humidity of downrange ballistics in nil., I beleive its effect we see has more to do with the internal ballistics. The altitude of my test range is 1640 feet above sea level, I have observed atltimeter readings from 1470 to 1750 during the course of testing, this has a small effect on velocity and follows barometric pressure.

Barry

Barry,

  Off topic? Nah! Well, maybe a little,  but that's what usually happens as one thing leads to another. For me anyway, topics are dynamic issues and one point usually brings up a coupla more in relation to it, which then leads further astray as the topic expands.

  On points 1 & 2..... I wish I had two chronographs so I could have seen this point of yours. When working up the load for the .40 cal. 313 gr. bullet I figured the 1-16" twist would create an overstabilized bullet but what was confusing were the low SD/ES's at the muzzle, but not corresponding accuracy at 100 yds. With your comments here it could possibly be what was happening.

  Points 3 & 4..... Does sound like what I've observed with the .32/40 especially.

  Your point number 5..... I have heard arguments that this is not necessarily so. That the gyroscopic effect as the bullet spins going down range tends to keep the nose of the bullet pointed to the initial line of flight from the muzzle. Which I thought might be the cause of my .38 cal. bullets showing a slight amount of tipping at 200 yds.

  Interesting that you think a 1-16" twist for the 320 gr. .38 cal. bullet would be better than a 1-15" or 1-14". In a discussion while shooting .22's indoors this morning I was thinking the same. Well, I guess we'll find out, as if my info is correct a 1-14" barrel is on the way if not here already.

  Your observations on humidity affecting down range performance mirrors what I was thinking. My range is 950 ft. above sea level. I wonder why that is? You would think that the density of the air would play a major role in down range performance just due to more or less drag on the bullet. Possibly it does at further distances than we shoot at in Schuetzen. But why would you think humidity would have an affect on internal ballistics? Internal air column resistance on ignition?

PETE

Barry,

I defer to your experience of forty years making moulds when you say that shallow grooves with rounded bottoms release bullets best.  The commercial manufacturing of moulds started many years before you did.  I suspect the manufacturers came to the same conclusion that you did when they started producing them.  I've worked as a tool designer; I've run machinery and I've also worked as a technical writer.  With that background, I also know that many product "improvements" are the result of cost cutting measures or promotional hype.  I only wanted to point out that sometimes a "real improvement" is the outcome of forces attempting to do something completely different.

Your comments about the barrel residue forming the lube marks in rifles when using smokeless powder is very logical.  Cast bullets are subjected to much higher velocities and pressures when smokeless is used and particles could easily embed in the bullet.  I'm not certain it applies when the pressures and speeds of black powder are involved.  I haven't seen it with black powder.  Perhaps the paper I'm using for targets doesn't attract it.  I usually use Kraft paper which has a slick surface when compared to regular target paper.

I must say that I am finding this entire thread very interesting and informative.

feather

Feather,

I am also an mechanical engineer and have many of the same career experiences as you. I totally agree with your manufacturing comments, having been a manufacturing engineer in charge of offshore operations and later directing engr. of advanced technologies for a computer hard drive company. I have the great admiration for an engineer that can actually make what he designs, I beleive there are way too few of us.

I also appreciate you comments on BP as I am a "babe in the woods" when it comes to this subject. I wish I had the range distances and the time to get involved in research in this area of expertice. Even if I had the time to explore BP, it would be almost impossible to find 1000yds here without a mountain getting in the way

Barry