power difference between swiss 3f an goex 3f

[sonny]

hello,can anybody tell me the difference between goex an swiss 3f.I heard that 70 grains of swiss 3f is equal to 80 grains of goex.Is this correct??anybody use swiss 3f for 54 cal muzzleloaders ? thanks.......sonny

[Jerry V Lape]

I think the generally accepted comparison  for the same granulation   is appox 10-15% difference between Swiss and Goex.  So you might start your Swiss load about 10% less than a Goex load. 

You can use 3F in a .54 if you like.  You should probably cut your starting load a little lighter than for 2F.  My hunting load in .54 is 80gr 2F Swiss.  It gives  me more velocity than 90gr of Goex 2F judging from higher point of impact at 100yds.

. 

[chapmans]

In my .40 cal flint with a 42" X 7/8" GM it took 70 gr of fffg Goex to get the same vel. as 55 gr of fffg Swiss.
   Regards, Steve C.

[Daryl]

Hmmm, Steve. I didn't think it was that bad, but the new lot of 3F GOEX I got is a good 150/200 fps slower than the last GOEX powder I used, bought locally. Dropping from 2,147fps down to 1,960fps was a bitter pill to swallow - same powder measure - very close temps - same gun and patch.

 Ross Seyfried found almost 20% difference between GOEX and Swiss in English ctg. gun regulation.  His problem was most ctgs. wouldn't allow enough GOEX to attain regulation, whereas the Swiss regulated perfectly with stamped powder charges. Where there was room, it took 20% more GOEX.  This was with charges well over 100gr. in the larger bores, from .50 on up.

 I know some guys who use Swiss in their .40 and .45 cal. chunk rifles use around 55gr. in .40's to to 60gr. in .45's of Swiss powders, whereas my most accurate loads with similar load combinations have been 65gr. in the .40 and .70gr. in the .45, using 3F GOEX.

 Swiss definitely gives higher speeds per gain weight.

[northmn]

I may have to order some Swiss as it is praised quite highly.  As to power, it costs enough more such that I can as easily use GOEX or Grafs and the little extra. If one looks at the results from BP cartridge gun matches, a lot use Swiss (at least those that place high). It is my understanding that it has different fouling characteristics and permits better shot to shot accuracy.  Shooting a ML you swab between shots every time you load as the patched ball swabs when loading and do not have the same fouling problems. I have seen the rock hard fouling at the last 6-10 inches on a 45-70 that will not permit hitting a barn.  That is rare in a ML with any acceptable lube ( some BP cartridge shooters used to add a "grease cookie" between the powder and bullet for extra softening of the fouling)  Somewhwere I read that GOEX is basically a military powder in that it can be compressed quite readilly and will go boom if formed into a slug.  Swiss is a "sporting powder" and can be loaded differently.  Most in BPC use magnum primers for GOEX while some like pistol primers for Swiss.   Merely pointing out that they are different powder types.  Matthews mentioned that in BP days there were a lot of different brands of black powder, almost as many varieties as smokeless today.  Some seemed to be more popular in some regions.  Which makes sense if you think about humidity effects on BP shooting.  Theres more tho the difference than just velocity.

DP

[D. Bowman]

I switched to swiss about two years ago and found that 10% to 15% less swiss to get same vel. as goex with less fowling and accuracy was the same or better.
The larger calibers seem to have the most difference. My flint 62. with 44 in. barrel only takes 92 grains of swiss to match the vel. of 120 grains of goex with much better accuracy. Velocity was checked with a chronograph and I tried two dif lots of goex . Same results.

Anyone have similar results?
                       
                                                          D Bowman

[sonny]

hummm.........think 70 grains of swiss 3f is too hot for 54 cal???

[Roger Fisher]

hummm.........think 70 grains of swiss 3f is too hot for 54 cal???

Well now Terry what you got???  a well breeched .54 in a 15/16the or inch or is it a .54 rotted out in a 7/8th??   What I'm saying is in a well built rifle 70 3f swiss is no sweat!   (to the best of my recollection!!)

[Dphariss]

Less fouling and less powder burned since Swiss will likely allow 5-10 grains less powder for a given velocity.

Dan

[Larry Pletcher]

I have not timed Swiss fffg against Goex fffg.  I have, however timed Goex and Swiss priming powders.  I don't know if one can use 4fg from both sources as a guide line for other powders grain sizes. 

Here are the results I got:

Goex 4fg before the PA plant exploded:  .0486 seconds
Goex 4fg after plant was moved:            .0474
Swiss 4fg:                                           .0413
Swiss Null B:                                        .0393

These were an average of 20 trials using the same lock.  The full report is in the April 2005 issue of MuzzleBlasts.  You can work the percentages a number of ways.  It looks like Swiss 4fg averages 15-17% faster than Goex while Swiss Null B averages 21-23% faster than Goex. 

I won't speculate about a comparison between 3fg velocities and 4fg ignition speeds, but there may be a correlation.

Regards,
Pletch

[longcruise]

This was not 3f, but 2f that was compared, but here are the results I got using 50 grains by volume of goex 2f and swiss 2f

Swiss 2f

1546
1531
1574
1558
Avg  1552

Goex 2f

1349
1362
1376
Avg  1362

Like Daryl said, he got a pretty big variation just by changing lots on Goex so these figures may not apply to other lots of these powders.

I started out with the intent of doing extensive tests of differences in powder performance but after reading some of the Mad Monks research it was clear that my tests would only be comparing lots and not brands so the whole project was abandoned.  Daryl's experience only confirms that I saved my powder for more useful endeavors!

[Daryl]

Easier to ignite would be a factor - allowing mild primers in ctg. guns - perhaps.  I do know that GOEX delivers it's best accuracy with strong ignition - and I seem to find better accuracy with less powder in a cap-lock than in a flinter. Of course, this has something to do with the vent losing pressure.  My wifle's Gm barrled cap gun gets the same accuracy with 55gr. of 3F GOEX as my .45 GM barreled flinter gets with 70gr. 3F. I haven't chronographed the cap gun as of yet.

 One day I may get to test Swiss - one day. I know a lot of ctg. gun shooters have difficulty with GOEX - they need to read and FOLLOW Mathews recommendations - once I did, fouling problems disappeared using both paper patched and grooved lubed bullets - from 10 to 20 shots without having to wipe and no buildup of fouling. Everything out the tube with one dry patch - winter, spring, summer and fall shooting - all humidity ranges.

[Brian]

The problem with SWISS powder here in Canada is finding it.   

And then of course PAYING for it!   

[chapmans]

Daryl,
  I found the paper that Larry wrote down the velocities on when we were doing the compression tests, they are as follows;  all fffg
                           Goex;  40 gr.  1645 fps
                                      50 gr.   1807 fps
                                      60 gr.   1946 fps
                                      65 gr.   1995 fps
                                      70 gr.   2069 fps
                                      75 gr.   2127 fps
                       
                          Swiss;  55 gr.   2072 fps

         This was a .40 cal GM 42 inches long and I don't remember if we had the perc. lock in or the flint.
       Larry do you remember?
 I only fired one shot of the Swiss as we were doing the test with Goex but I wanted a comparison because 55 gr of Swiss is what I shoot for target.
      Regards, Steve C.

[Larry Pletcher]

Daryl,
  I found the paper that Larry wrote down the velocities on when we were doing the compression tests, they are as follows;  all fffg
                           Goex;  40 gr.  1645 fps
                                      50 gr.   1807 fps
                                      60 gr.   1946 fps
                                      65 gr.   1995 fps
                                      70 gr.   2069 fps
                                      75 gr.   2127 fps
                       
                          Swiss;  55 gr.   2072 fps

         This was a .40 cal GM 42 inches long and I don't remember if we had the perc. lock in or the flint.
       Larry do you remember?
 I only fired one shot of the Swiss as we were doing the test with Goex but I wanted a comparison because 55 gr of Swiss is what I shoot for target.
      Regards, Steve C.

Steve,
I think those numbers were from the percussion.  I'm having trouble finding the right stats.  I have too many notebooks.  What I did find was organized by compression and not by load weights.  There must be more stats to find.  (BTW Both flint and perc. liked 3/16" compression.)

Pletch

[Herb]

This is my test of Goex 3F against Swiss 3F and Swiss 2F, using my Jacob Wigle rifle I built (Westmoreland Co., PA).  Barrel is a Rice .40 7/8" x 38", 1-66" twist.  Balls were .380 cast with pillow ticking, I think.  Murphy Oil soap and alcohol lube.  I was testing double ball loads for a friend who wanted to use her .40 caliber for deer hunting and had to have a projectile weight more than 150 grains to be legal.  The game warden suggested double balling.  So I tested it.  I started at 35 grains of Goex 3F and a single ball.  Adding a second patched ball on top of the first dropped the velocity over 400 fps.  So I doubled the charge to 70 grains to get the velocity up, with fine results.  Then I tried these in my rifle.

The top left target is 70 grains of Goex 3F, mean velocity 2201 fps with 36 fps variation.  Next I shot the target below it, seating a second patched ball on top of the first.  Mean velocity for three shots was 1765 fps with a 9 fps spread.  A loss of 436 fps, but twice as accurate.

Next, top center target, 70 grains of Swiss 3F single ball, 2361 fps for 7 shots, 40 fps spread.  Then the one below it with double patched balls.  1863 fps for three, 15 fps spread.  A loss of 498 fps with double balls.  I don't know why the two balls in shot number two went wild, never had it happen again.  Notice that shot number one had both balls in the same hole.

Top right target, 70 grains Swiss 2F, single ball, 2271 fps for six shots,41 fps spread.  Bottom right target same but double patched balls.  1784 fps for three shots, 18 fps spread.  Velocity drop 487 fps.   Shot number three, both balls in the same hole.

There was no wiping after any shot nor cleaning between powders or targets.  Again, the purpose of the testing was to determine the character and safety of double ball loads.  Carole did use a double ball load of Goex 3F and killed a mule deer buck with it.  But double ball loads are not to be used without a really good reason.  Carole's was that there is no commercially available conical bullet for .40 caliber and she wanted to use the rifle we designed and I built for her, and which she can load and shoot easily.  But if that second ball is not fully seated on the first, or separates during the hunt, it obstructs the bore and the bore will be damaged.  I recommend against the use of double ball loads.

Here is a .50 Wigle rifle I built, walnut with silver-filled alloy patch box.  Rice barrel.
Targets also shot at 50 yards rest, .490 cast balls, .015 PT, lube Murphy Oil Soap one, alcohol two parts.  Top left, 50 grains Goex 3F, five shots 1492 fps, 63 spread.  Group 1.2".  Top, second from left, 50 grains Swiss 3F, 1618 fps, 12 fps spread, group 2".  Third from left, 80 Swiss 3F, six shots 2030 fps, 36 spread, group 2.6" but without blown patch shot, five in 1.1".  Top right, 80 Goex 2F, six average 1750 fps, 44 spread, group 1.3".  No wiping or cleaning at all.

Bottom targets shot a week later with clean bore and using lube of one to one.  Left, 50 grains of Goex 3F, five average 1503 fps, 29 spread, group 0.9".  Next, 50 Swiss 3F, five 1623 fps, 21 spread, group 1.25".  Third, 80 Swiss 2F, five 1857 fps, 39 spread, group 1.5".  Right side, 80 Goex 2F, five 1714 fps, 50 spread, group 1.0".  No wiping or cleaning at all.


This shows relative velocities for these powders and I leave it to someone else to say how much less Swiss 3F to use to equal a velocity of a Goex 3F charge.

[Daryl]

Sure like the looks of some of those groups, Herb.  Not hard to see what load to use for trail-walks in your .50.

As to the dismal performance of single ball loads in the .40 perhaps a thicker patch might help with single ball loads.  A .390" ball and .020" patch should be loads better.  At lest it will go close to the bottom of the grooves, instead of barely touching the tops of the lands.

[Herb]

Thanks, Daryl.  I have a double cavity Lee .380 mold and so a lot of those balls.  I also like .390's and can't tell much difference between them and the .395's.  .400's are harder to load.

[arcticap]

It's novel to think that if Swiss is that much better, then individual duplex loads could be concocted so as to benefit from some of it's superior characteristics, at least for practice anyway and without all of the extra cost associated with shooting it exclusively.

According to one recent post:

From Powder Inc.'s invoice........ 1 pound of FFFg Black Powder
by Brand
GOEX . . . . . . . . . .$12.75
GOEX Express . . . . $17.75
Swiss . . . . . . . . . .$19.25
KIK . . . . . . . . . . . $10.60 ~ because they were out of Schuetzen which is similar, they reduced prices of KIK until they get restocked on Schuetzen.

[Herb]

Here are some more.  For each target, I fired a fouler on the bottom right target first, because the first shot with a clean bore or powder change is usually lower in velocity and out of the group.  There was no wiping between shots or cleaning between groups.  All shots are .490 cast balls with white 7 ounce denim from Wal Mart patches and lube is Murphy Oil Soap and alcohol.

Top left, 80 grains Goex 3F.  Note velocity of first shot is lower, and the fouler was out of the group (see No. 1 on lower right).  Mean velocity for six shots is 1832 fps with 63 spread,  but excluding the first, mean is 1840 fps with 29 fps spread.  Group is 1.1".  Target 2, 80 grains Swiss 3F, mean for six is 1985 fps, 28 fps spread, group 0.95".  Note that the first shot on the sighter target (#2) was out of the group.

Target 3, top right, 70 grains Pyrodex RS with 10 grains Goex 2F as a booster (I tapped down the powder in the measure and added the 10 grains black on top, and dumped it down the bore), mean velocity for six is 1686 fps, 53 spread, group is six in 1.55" but five in 0.9".

I build rifles as heirlooms (this one was for a Weigle relative of mine) and so I test replica powders in case the owner can't get black powder some years in the future.  Have to hope he'd have some black powder for boost charges and pan priming.

Target 4, lower left, is 70 grains of Triple 7 2F with 10 grains Goex 2F booster on top.  First six shots, mean velocity is 1881 fps with 138 fps spread.  Then I shot five more but added an over powder wad to the loads, for a mean velocity of 1921 fps and 76 fps spread, but better accuracy, four in 1.0"

Target 5, center bottom, is 70 grains of Triple 7 3F with 10 grains Goex 2F booster and an OPW.  Eight shots mean velocity 1962 fps, 80 spread.  Seven shots in 3.2" but five in 1.08".  I don't know why shot 2 was out of the group.



Here are velocities from a .54 Henry Albright flintlock I built, 42" Green Mtn barrel.  A direct comparison of .530 Hornady balls, .020 pillow ticking, MOS/alcohol lube and a 3/4" thin leather OPW for all loads.  80 grains.
Goex 3F, mean velocity (MV) 1652 for six, ES 90 fps.
Goex 2F, MV 1525 fps for five, ES 20 fps
Swiss 3F, MV 1810 fps for five, ES 103  fps (had trouble with loads here)
Swiss 2F, MV 1724 fps for five, ES 25 fps

Triple 7 3F, 70 grains with 10 gr Goex 2F booster:
Six shots 1799 fps MV, ES 66 fps
Triple 7 2F, 70 grains with 10 gr Goex 2F booster:
Six shots 1703 fps MV, ES 51 fps.
Pyrodex RS (I didn't record it, assume 70 gr w/ 10 gr Goex 2F booster)
eight shots 1504 fps MV, ES 50 fps.

Couple days later,
80 Goex 3F, loaded as above, 5 shots MV 1662 fps, ES 37 fps.
75 Pyrodex RS with 5 gr Goex 2F boost, 5 shots MV 1506 fps, ES 27 fps.
75 Triple 7 2F with 5 gr Goex 2F boost, 8 shots MV 1736 fps, ES 44 fps.

80 Goex 3F, thinner leather OPW, 5 shots MV 1662 fps, ES 37 fps.
75 Pyrodex RS with 5 gr Goex 2F boost, 5 shots MV 1506, ES 27 fps (same as before!)  Also same accuracy, groups were 1.45" at 50 yards.
75 Triple 7 2F with 5 gr Goex 2F boost, 9 shots MV 1724 fps, ES 44 fps.  This group of nine shots was in 2.1", the same as before.  The Goex loads went 2.55" first and then 2.55" the next time!  This was a very good barrel.  I did not wipe between shots nor clean between powders, 37 shots in this test.

[Daryl]

Interesting, Herb- looks as if the Swiss 3F and GOEX 3F win the day.  Your veloctiy variations without using the booster BP showed spreads I've come to expect with straight phoney powders. I've not tried them in a finter with or without BP in them. In the cap lock I did test them in, the spreads were over double BP spreads, but still kept to a fairly low 30fps or a bit less. BP spreads in both the .58 and .69 were way less than 10fps over 10 shots.

[Herb]

Always nice to hear from you, Daryl.  I did use 10 grains of Goex 2F boost with the Pyrodex RS and Triple 7 2F and 3F.  An over powder wad saves the patches and reduces the shot velocity variation.   And accuracy can be good even with a large velocity variation.  I rarely get small velocity spreads, say below 20 fps, for anything I shoot.  There may be ways to do things better, but I ain't learned them yet or am too lazy to use them.

[Mad Monk]

When the Swiss powder first arrived in the U.S. I was asked to look at it.  Nobody out there really understood what a true sporting powder is nor how to handle it in a gun.

When it was relayed back to the Swiss that I had been banging away with the 3F in both of my .50 caliber rifles I was told that the 3F powder was intended for use up to .36 caliber.  Above .36 caliber you should use 2Fg powder.

I had found that at about 60 grains of 3F in the .50s I would begin to blow holes in the .018" #40 cotton drill patch material.

Both of the .50s have patent breeches with powder chambers holding about 40 grains of powder.  So I would start the chronograph work at 40 grains and go up in 10 grain increases.  Working in this showed a pattern in the ES data.  At the 40 grain charge the ES was fairly large.  As I increased the size of the charges the ES would go down.  Then begin to get larger.

In the GPR when I did not wipe between shots I could get an ES of 5 to 10 fps.  If I wiped between shots the ES would go up in the 25 to 30 fps range.

The Swiss powder is faster and hotter compared to GOEX.  During the latter-half of the 1800's a sporting powder was about 10% stronger/faster than a rifle type powder.  GOEX and Schuetzen being rifle type powders as far as burn rates go.  A really good European sporting type powder could be 15 to 20% stronger/faster than a rifle type (burn rate) powder.

When the Swiss changed from tin cans to plastic bottles they bumped the strength of the powder up.  At the time it was about 20% stronger/faster than what GOEX was producing.  Then GOEX got their charcoal supplier problem straightened out and the difference between them was around 10 to 15% depending on which lot of GOEX you shot against the Swiss.

The performance of the Swiss powder was a driving force behind GOEX's development of their Express Powder.  In the ML rifles the Express is faster than their regular production but not quite as fast as the Swiss.

There was a comment about mixing brands given the cost of the Swiss.

In Europe the Swiss powder has been done for exceptional lot to lot uniformity.  This has also been commented on by some of the U.S. bp cartridge crowd.
The Swiss powder is also noted for being a "moist-burning" powder (or Mit Nassbrand as the Germans once described this property).  As soon as you mix another brand of powder with the Swiss you will loose this moust-burning property.

[Daryl]

Thanks for the explanation Bill. It is always a pleasure to learn from you.

  I got used to the low shot to shot velocity strings in the larger bored rifles I used to shoot and expect/demand them from everything I shoot now. I also know that the lowest velocity variations do not always give the best accuracy at close range.  Sometimes, as Herb noted, large variattions also shoot well.  I know that low variations have the 'potential' to produce the best results on paper - especially as the ranges get longer. The more variation, the greater the vertical stringing as the boys found out in ctg. guns when trying to use Pyrodex and other 'fakes' with bullets - it just didn't work out at the exctended ranges bullets are capable of.  We don't shoot those 'bullet' ranges with round balls, however once our ranges extend out to 75 to 125 yards, large spreads in velocity begin to show up as vertical stringing.  This compounds difficulties in hitting 'centre' at the longer ranges we do shoot with RB's.  An errant or 'slow' ball that goes 'just' under the target with a 'good' hold makes us think we are aiming too low, so we compensate and then shoot over with the next one, average or 'fast' - back and forth with the odd hit in between and we think - It's out of range" when a bit more load development might have given us success.

  In testing, I found adding a wad didn't help my accuracy nor did it help with shot to shot uniformity - probably due to the rather snug combinations I shoot as a normal load combinations.  Many other guys use similar ball/patch combinations, while others try to get by with loose loads. An extremely good shot with a poor combination can shoot better than a poor shot with a good tight combination - we see this fairly often. The most consistant shooters, however, practise, use tight combos and are always in the top 3 or 4.

 It of course, all depends on what a guy wants from the sport - sometimes we tend overlook this in an attempt to 'help' people shoot the very best from their rifles, and our 'help' is overkill.

 From what I've learned in this thread, I surmise if the best accuracy is desired, then use the best powder you can obtain. In the States, I'd be using either Swiss (if I could get it) or GOEX Express for competition shooting and practising with normal GOEX.  I'would have used enough of the 'better' powders to find loads that gave the best my rifle would produce, written the combinations down in my rifle's manuals and saved them for competition. In the mean time, for practise, I'd be shooting the best loads that normal GOEX provided.  If I shot as well with normal GOEX as I did with the 'better' powders, I'd know I needed more work with the 'best' powder's loads as I hadn't 'arrived' at their 'best' yet.

 What are the combinations that have given the best results for me, Taylor and the guys I shoot with - pretty much identical - ball .005" 'under bore size' or a few thou. larger than that, coupled with a .018" or thicker patch (8 to 10 pound denim). Spit, LHV, or windshield washer fluid and an oil such as neetsfoot oil or olive oil seem to work well for us.

  I use a michometer for measuring patch thickness. It is the only system that gives me repeatable and consistant results - calipers don't - for me.  Caliper measurements also give readings some .003" or more, larger than the mic. provides, so if you use calipers, instead of my .018" patch, you'd be measuring a .021" or .022" patch.  My .40 and .45 rifles both load easily with .005" under and a .0215" mic'd patch-  guess that would be around .025" if using calipers.

 Oops - guess I'm getting carried away again - sorry.

[Mad Monk]

  I use a michometer for measuring patch thickness. It is the only system that gives me repeatable and consistant results - calipers don't - for me.  Caliper measurements also give readings some .003" or more, larger than the mic. provides, so if you use calipers, instead of my .018" patch, you'd be measuring a .021" or .022" patch.  My .40 and .45 rifles both load easily with .005" under and a .0215" mic'd patch-  guess that would be around .025" if using calipers.

 Oops - guess I'm getting carried away again - sorry.

Daryl,

Just home from work.  Uncapped a bottle of Mad Elf ale and fired up the computer.

Almost any powder can be made to shoot with an "acceptable" degree of accuracy.  But what is acceptable accuracy to one shooter is not so with another.  Some powders are sort of inherently accurate while another might be inherently inaccurate.  All depends on how well the powder maker densifies and polishes the powder in question.

The use of a micrometer to look at patch cloth thickness has issues.  When I worked in the PVC Film and Sheeting div. at the plant we would measure the thickness of the various compounds coming off the extruders and off the calanders.  This was done using a stand with a dial indicator.  The foot of the dial indicator was of a specified diameter.  On the top of the dial indicator spindle there was a weight of a specific weight.  This gave a specified foot area to weight applied.  So the pressure being applied to the sample was always exactly the same.  This same set up was used in the fabric industry, an ASTM test.

In looking at cloth you might want to consider something.  You may have a piece of cloth that with light pressure on the micrometer shows .018".  Then crank down a little more and you could be looking at .012".  I call that the crush.
When I first looked at the .018" #40 cotton drill I was impressed.  It would only crush down to .015" under pressure.  This cloth has a high thread count and is very tightly woven.  Originally made for pants pockets where extreme strength and abrasion resistance was called for.  In fact it was once known as pocket drill.
Then you look at other fabrics and they might be .018 to .020 under little micrometer pressure and crush down to around .012" under pressure.

The last few years there has been a trend towards cheapening cloth.  To the naked eye it looks the same.  But a close look shows that the cost cutting folks have had a go at it.  This is especially true in the bargain stores or the "box" stores.

Going way back in ML shooting.  Sam Fadala had written several very good articles where it stated that the patch is not a gasket.  Does not really seal the bore. 
While it did not explain it this way.  The patch points in the wrong direction to be a gasket.

I would describe the patch as a frictionless obturator.  At least that is the way the military papers describe foam wads in artillery loadings.  The patch is also an applicator for the "lube".

Few shooters know how to really read fired patches.  Until the patch has large holes blown in them or are shredded they don't think anything of them.  Sometime hold fired patches up to a light with the light behind the patch as tyou look at it.  You will see a steady progression of cloth damage as you increase the charges above a certain point.  The patch fabric AND the lube will determine the pattern of eventual patch failure.  Failure can come quicker at lighter charges when fine grain powders are used.
As the amount of gas blowing past the patch, during the firing of the gun, increases you see an increase in the damage to the patch threads where the patch is pressed into the grooves in the rifling.
Patch integrety during the full acceleration cycle of the ball can make or break accuracy even if the numerical data (ES) says everything is well and good.

Bill