how far down the rabbit hole with pellet weights.

[bandg]

My belief is that sorting for size would probably improve consistency. My belief is also that sorting for weight would probably improve consistency. Seems sorting for both might improve consistency even more than either sorting alone. Those that feel differently should certainly not waste their time doing so or should do only what they believe will help their shooting, if they believe anything at all will help. Lots of views on the issue.

 

[Xbowsniper]

nced,

I do see what you are saying, but, for a 20" pcp barrel, the above is what I have noticed and experienced.

As far as the pellet being sized when it is put into the breech, yes, to some degree. But, there is still friction.

I've done this test with an unchoked 20" Crosman barrel, of the new design.

Take a pellet measured with a precision gauge like the Pelletgage. Get a couple of pellets that measure 4.50, and a couple that measure 4.54. Put them into the breech and push them through with a dowel. You will feel modest resistance with the 4.50 headsize pellets. Do the same with the 4.54's. The resistance through the entire barrel is noticeably greater, much greater than the smaller ones. If the breech sizes them the same as you said, then the resistance should be the same as well. But it is not, not by a longshot. 

As for air loss of a smaller headsize pellet, the skirt blows out to create the seal, the smaller headsize would just make the pellet inaccurate.

As far as drop at 55 is concerned, I notice a 1 inch drop for every 25 fps lower than my standard. PCP barrels compared to Springer barrels might be the difference there.

I hand lap my barrels, and polish them to a mirror finish. I have found high and low spots within most barrels, which is why I lap and polish them. I use a borescope to inspect the bore at the end of the process. 

In the end, we all do what we do individually to make our little air puffers as accurate as possible. Ain't this fun??

Tom Holland 

Field Target Tech 

 

[nced]

Thanks for the fine dialog!

I always thought of lead as being malleable, especially the "pure lead" used for JSB type pellets and once "squished down" the lead doesn't "un-squish" going down the bore. Since you "hand lap my barrels, and polish them to a mirror finish" is there a possibility that the bores are actually tapered a bit toward the muzzle (assuming you're "lapping" from the leade to the muzzle which would cause a pellet to be further swaged when pushed toward the muzzle?

Concerning the use of "holes in a plate", I've measured thousands of JSB Exacts, H&N FTTs and boxed Crosman Premiers and found that a high percentage of all brands of pellets are actuall OVAL (some by as much as .02mm) when measured at points 90 degrees apart. It would seem to me that the only thing the precision holes accomplish is to sort pellets by the "wide oval". I do realize that sorting pellets with vastly differing head sizes (like the supposedly 4.52mm JSB Exacts and 4.52mm H&N FTTs) is certainly better than shooting them unsorted even if they are "oval" by a hundredth of a mm.

 

[bandg]

Seems the malleability is the exact issue. Larger head will "squish" into contact with lands (and possibly grooves) and that "squish" would seemingly have to create more contact area with the bore. More contact area=more friction=possibly lower velocity.

I've read where others have stated that the ideal situation is for the head to be engaged lightly by the lands to guide the pellet down the bore while the skirt seals the rear into the bore. If that is true, and it does seem logical, then any additional head size would seem to only cause more contact with the lands/grooves as the lead is "squished" down. It wouldn't fall away, it would just be squished into contact with parts of the bore. More friction. Taper would seem to be irrelevant.

In years past, I've built a few car engines. One of the more difficult tasks can be miking the bearing surfaces. And that is a relatively large are where you can see very well the alignment you are trying to attain with the gauge. I don't disagree with your view that many if not most pellet heads may be slightly oval in shape. Trying to accurately measure around the radius of a .177 pellet head by hand while keeping the pellet from being slightly tilted in the caliper jaws seems to be a very difficult task. If you can do so accurately, you have much better feel than I do. I'll stick with the pellet gauge for that reason.

 

[Xbowsniper]

Guys,

I just further proved something that I have suspected, as nced mentioned about malleability. I shot 7.9 grain JSB Express through all 3 (Marauder, Steyr, TM 1000) of my FT rigs, at around 820 FPS, just under 12 ft.lb. I then shot 7.9 grain Crosman Premiers (Die B) through all of them. In all 3 rigs, my FPS drastically decreased by over 100 FPS. This is most likely due to the harder alloy the Premiers are made from, proving friction is a big factor in velocity loss/gain/retention.

And we though this air stuff was simple!!!

Tom Holland 

Field Target Tech 

 

[bandg]

Quite a difference. Both types matched for head size?

 

[Xbowsniper]

Bandg,

Actually, the head size on the JSB'S were larger than the Premiers, but is seemed the Premiers fit much tighter in the breech. 

Tom Holland 

Field Target Tech 

 

[nced]

"If you can do so accurately, you have much better feel than I do" and "while keeping the pellet from being slightly tilted in the caliper jaws seems to be a very difficult task"

Not really difficult with the right technique, just tedious, especially since each measurement is repeated to verify (each pellet head measured 4 times if I was checking "ovality". For example.........

"keeping the pellet from being slightly tilted".......

That's why I don't use micrometers to measure the spherical surface of a pellet head but use a good digital caliper measuring like this.......





I recently measured a tin of 4.52mm labelled 8.4 grain Air Arms domes and using the above method most of the pellet heads were around 4.51mm. Obviously the caliper "unit roundoff" will affect the second metric decimal but it's close enough for my purposes so I measure each pellet head a few times to verify the reading (why measuring pellet heads is so tedious and not worth the effort with my shooting skills sitting on a bucket (or even bench rested). Here is the head size distribution for the supposedly 4.52mm JSB Exacts using the above measuring method..........



Funny thing is that I saw a post of "pellet head size distribution" using the "holes in a plate" and there was the exact same distribution as the above caliper measured pellets so I'm guessing that a good caliper method with a known good caliper is equally effective..........



I have a pellet head sizer that also expands the pellet skirt a bit and the pellet heads from the sizer is 4.50mm as measured with the above caliper. As mentioned, the AA domes marked 4.52mm measured 4.51mm using my caliper. When I pushed the head of an unsized AA dome measuring 4.51mm through the sizing ring the pellet head was indeed reduced .01mm and measured 4.50mm after sizing. LOL....considering the unit roundoff of my caliper the result is "good enough for me", certainly better than a pellet with an oval head being sorted by "holes in a plate". I tried to head size some supposedly 4.52mm JSB Exacts using my sizer and most of the pellet heads fell through the 4.50mm sizing ring with no sizing at all!

"In all 3 rigs, my FPS drastically decreased by over 100 FPS."

Humm.....just this week I shot both 4.52mm 8.4 grain AA domes and 7.9 grain die "B" CPLs from my HW95 and the AA domes were about 20fps slower than the lighter 7.9 grain CPL. I've noted this repeatedly at about 12.5fpe but always assumed the slower AA fps was simply due to the extra weight. Oh well, I ain't never shot a barrel lapped Steyr and have no explanation why you get a 100fps velocity reduction with CPs and I get a 20fps velocity increase shooting 7.9 grain CPLs vs the 8.4 grain AA domes.

"And we though this air stuff was simple!!!"

It is simple, the shooter only needs to shoot what works best till finding something that works better!

 

[bandg]

Interesting measuring method. Probably quite tedious as you say. Accurate? Maybe. I'll stick with the "pelletgauge". But it is an interesting method.

 

[nced]

The JSBs have a head larger than 4.55mm? The last CPL order was 4 cases on June 2015 and I received die lot "B" dated Feb 2014 and I did do a "spot measure" from one of the boxes with this result. Perhaps the JSBs didn't have larger heads or perhaps the hard lead alloy affected the fit............



They worked fine in the Beeman R9 however they were too tight in the HW95 giving "sore finger syndrome" after a 100 shot session.

I just ordered another case of boxed CPLs and according to the tracking number they are supposed to be delivered next Friday. I really don't know what die lot number will be after the last order 4 years ago but I'm anxiously awaiting the delivery. All the CPLs in the last box I have have been head sized to 4.50mm as measured with my digital caliper after being head sized with my pellet head sizer. When they arrive I'll shoot them from both my looser leade Beeman R9 and tighter leade HW95, then compare the velocity results with my AA domes from the tin.

 

[nced]

Just for grins I ran two new boxed die "B" CPLs through two different HW95 bores with a coated cleaning rod and had a rather interesting "bore maps".

The HW95 barrel i'm currently using (supplied with the gun) .........



The HW95 barrel I bought from a Canadian retailer when they were closing out their stock of HW parts. It was "bore mapped" when first received...........



Both bores were tight from the leade to the end of the barrel pivot block which initially swaged the pellet, then (being swaged) the pellet slid with almost no resistance in both bores till it was again swaged by the constriction at the choke. Tonight I measured the length of the "constrictions" with the barrel on my HW95 and was interested to find that the choke at the muzzle was 1" long.

Just for grins I pushed two more new CPLs and then measured them after they exited the barrel and this was the result.......

Pushed this CPL till it just exited the "barrel pivot block area" (about 4 inches down the bore), then pushed the pellet backward out of the leade and measured the amount of swage 3 times getting the same result. The pellet head started at a measured 4.50mm after sizing..........



Then another pellet was pushed through the length of the barrel past the choke and this was the result..........



With my particular .177 HW95 a CPL with the head sized to 4.50mm before pushing was "swaged" to 4.49mm after passing the barrel pivot block, then it was pretty much "free sliding" till the choke where it was again reduced to 4.46mm before exiting the barrel. A pellet starting at 4.50mm before loading into the leade was reduced .04mm by the time it exited the bore and only a total of 5" of the 16" barrel length exhibited any resistance to the cleaning rod pushing the pellet.

 

[Xbowsniper]

Nced,

That's pretty interesting, I've found that almost every barrel has it's own "fingerprint", so to speak. I recently bought 3 Marauder barrels, from their new designed tooling, and given they are the same production run, they all vary a bit. I've compared them with LW barrels, and, I'm actually impressed with the bore finish. It's actually on par, or actually better than the LW's of the same quality. What I have found, is the barrels weak point, and that's the leade. It takes a little bit more finesse to chamber a round. Meaning, that you have to lightly fiddle with the bolt until the pellet "drops" into the breech. If you don't, and just force/push the pellet into the breech, deforming it. I've lapped all 3 barrels, in a little bit different way than most. I'll put a pellet into the breech, and with a wooden dowel, and push it through slowly. I'll do this until the pellet comes out the muzzle. As I do this, I take note where the "highs and lows" are so to speak. The next pellet I insert, I repeat the process. I then take a third, push it through until I feel the first resistance. I'll stop, mark the spot, and continue until the next. I'll do this until it exits the barrel. I'll repeat this with several pellets, to insure that my findings are consistent. I'll then take a bore mop with polishing compound to the restricted area, and chuck it on a drill. I'll work it for 15 -20 seconds. Another pellet goes down, and if it needs more, I'll give it to it. I keep doing this to the entire length, until its smooth to the choke.

The chokes on a Lothar Walther barrel are about 1-1 1/2" long. A Crosman barrel choke is about 3 inches long.

I'm having swaging dies made, and gave the die maker shot and recovered pellets from a Steyr, and TM1000. After analyzing them through their super microscope, he determined that the size of my bore was 4.50, so the dies will be 4.51, so the choke swages them only 1 thousandth of an inch, for optimum "slickness", so to speak.

This just gets so involved, that's why I love it, I'm always up for a challenge.

Tom Holland 

Field Target Tech 

 

[JungleShooter]

To get back to the other issue of the discussion -- the variation in pellet weight...:

If there are really variations as large as 1.4 grain, well, that's got to affect the POI.

Trying this out in ChairGun, at 33 FPE, at a range of 100y this makes a whole inch of a difference....

It's comical that JSB usually writes the weight of its pellets with two digits after the decimal. But for the Beast, they chose not two but three digits after the decimal, 33.956gr. REALLY?!? C'mon JSB, don't be pulling our leg (or our POI),... just because you state the pellet weight with more precision doesn't endow it magically with more accuracy....



JSB, H&N, RWS, Crosman, and all those who rebrand the aforementioned pellets: Let's get real and produce pellets with weights accurate to the first digit after the decimal, and we'll all be happier. No weighing. No deceit. No change of POI.

Matthias

 

[nced]

"If there are really variations as large as 1.4 grain, well, that's got to affect the POI."

Hummm.........will .177 CPLs with a weight variation of .36 grain, or a weight variation of .44 grain affect the poi at 55 yards enough to matter? A better shooter than I probably can tell, however I can't tell any difference. LOL.......when I used my Ohaus 5.0.5 balance beam powder scale to weigh pellets they were "good to go" if the weight varied less than 1/2 grain. I do know however that I CAN tell that a loose fitting pellet in the leade WILL affect the poi so it seemed that the questions of pellet fit and barrel geometry were more relevant to the origional question revolving around .22 cal poi shifting at 100 yards.

.20/.22 pellets shot from a Beeman R9 was too loopy past a 30 yard zero to be useful when squirrel hunting so they were nixed in favor of the flatter shooting "skinny pellet". LOL......at that time the concern was using the correct holdover to brain a squirrel, not the poi being affected by variations of pellet weight.

Anywhoo......I'll back out of this poi question since pellet fit to bore and barrel geometry has only "muddied the waters".

 

[rangur1]

i just finished weighing a batch of 350 JSB 25 cal MK2 pellets. i will assume my new scale is working properly. the weight range was from 31.5 grains to 35 grains , wow.

vast majority were from 33.5 to 34.5 grains with 2 cluster groups at 33.7-34 g and 34.3-34.5 g so i have decided to group the pellets into 3 weight catagories to keep them more consistent. the idea is to use select group for shooting at a time. at .3 g variance , they should group tight. regardless of weight range. that's the theory anyway.

 

[bandg]

i just finished weighing a batch of 350 JSB 25 cal MK2 pellets. i will assume my new scale is working properly. the weight range was from 31.5 grains to 35 grains , wow.

vast majority were from 33.5 to 34.5 grains with 2 cluster groups at 33.7-34 g and 34.3-34.5 g so i have decided to group the pellets into 3 weight catagories to keep them more consistent. the idea is to use select group for shooting at a time. at .3 g variance , they should group tight. regardless of weight range. that's the theory anyway.

Interesting and seems logical. That weight range would certainly seem enough to cause misses. Not to consider the possible shape variance that causes the weight change. Seems the 33.5 to 34.5 would probably be fine but the outliers could be a problem. Sorting into the 3 groups probably even better. And sorting those through a "pelletgauge" might improve performance even more. Might reach a point of diminishing returns at some point.