How to measure slugged pellets?

[Zoey]

Last night I slugged 11 pellets by shooting into a swimming pool. After retrieving them, they were dried and sprayed with lubricant to prevent oxidization. 

I am now tasked with measuring them, but am having difficulties with this process. I've tried using a quality pair of calipers, but getting the head or skirt of the pellet in the correct plane is proving to be futile.

So, my question is how does one measure a slugged pellet?

 

[Paio]

I would simply recommend a pelletgage. It is a device to determine the head size of pellets in 0.01mm increments. Micrometers or calipers are really tough to use in such small and soft lead pellets. Other possibility is to use a precise optical measurement device in a metrology lab. 

However I am curious to see if the impact of a pellet in the water would create deformities on the head. I think the best way to slug a pellet is to lubricate it well and push it with a rod.

Regarding the skirts, no point to measure then after slugged.

 

[Strever]

i have been waiting to see how many answers you would receive for this very interesting question
it looks like not many people can measure a slugged pellet
i have a method most people do not have, i have an air gauge
http://www.airgunnation.com/topic/pelletts-gauges/ 
the pellet gauge is an excellent tool but can not measure a slugged pellet
i check the pellet in the air gauge first and then i insert in into the breech end about 2 inches and push back out with a cleaning rod
then i measure it again in the air gauge
can push out thru the choke to see what size the choke is
Paio is correct it would be interesting to see how much the water deformed the head

 

[Zoey]

Please bear with me as I am typing out loud here:

Honestly, I'm quite perplexed. I've read over and over people stating that their gun prefers a particular brand of pellet with x.xx size head. This would lead me to believe that they are measuring pellet head size. It's been established that size, as indicated on tins of pellets, are more of a generality than matter of fact. Some manufacturers appear to be more accurate than others, but none are spot-on every time. Does this mean that people are simply accepting published numbers as the gospel? Is it a placebo effect?

I don't know what, if any, effects there would be on a pellet fired into a column of water? It would be interesting to measure a traditionally slugged pellet v.s. one fired into water. For sake of discussion, let's say that I undertook the removal of my barrel and slugged it in the traditional manner. Not being able to measure the pellets, the results would still be as useful as shooting into a water column. What I'm saying is that it's a moot point if I can't measure a pellet.

I was thinking about the effects of both water and slugging deformation. I would imagine that there are "ridges" or "raised areas" at the intersection that the lands and grooves meet. As stated by Strever and Paio, how much, if any, deformation would there be from water impact? I envision the pellet's head "mushrooming" out, even if it be a minute amount. If I were to use the PelletGuage, and assuming a "mushroom" effect, one might come to the conclusion that the proper sized pellet must have a smaller diameter than measured. In other words, at least there would be a starting point as opposed to purchasing and shooting countless pellets until the "perfect" pellet is found.

An air gauge would be fantastic. However, as nice of a gun as the Vulcan is, I don't know that it warrants the cost of an air gauge?

I've posted my original question on several different AG forums, but have yet to receive an answer. I'm left being frustrated... I'll keep mulching away at this until I figure it out.

 

[Paio]

I share your frustration Zoey. I am too in a quest to find the perfect pellet for my airguns. I have read and followed all the recommendations here in this forum and others. I now have pellet inspectors, magnifying glasses, pelletgages for different calibers, scale and I am rolling pellets following the Yrrah method. I have spent a couple hours on my evenings sorting pellets. I did not slug any pellet in my barrels because I had my doubts on the process.

So far, I have virtually eliminated fliers using the Yrrah method - which is fantastic. My groups are tightening and next weekend I will do more grouping tests on using different diameters (for instance, in a tin of JSB 18.13 grains labeled 5.52, I have found diameters from 5.48 to 5.54!). To eliminate human error, I will do it in a gun vise this time. I couldn't find a solid and good vise in my country so I did one based upon a CTK Precision P3 vise. 

So, don' feel frustrated alone... Part of the fun on airguning is that we don't have all the answers yet...

 

[Zoey]

Thanks Paio. It looks like we are an army of two.

Well, until I figure out how to measure a slugged pellet, I'm going to see what effects Yrrah rolling, using the PelletGauge, and weighing have on accuracy.

First, I Yrrah rolled a bunch of pellets. Each pellet was rolled a minimum of 3 times to ensure accuracy. I have no idea what the acceptable/unacceptable range is for my gun's preference. Therefore, I made many divisions, and will be testing each to determine at what point a pellet would be excluded. 

(I used a glass-framed picture as my rolling table. Instead of using wood pieces as backstops, I used rulers taped to the glass.)

The next step will be to measure the head sizes in each group for subdivision. I'm waiting for the arrival of a PelletGauge.
Once that step is completed, I will weigh each subdivision for further separation.
The final step will be to shoot at the indoor range.

 

[LIVIT]

Good choice on the Pelletgage brother. I mentioned it in the PM about measuring slugged pellets. I think its a more realistic tool too use than a micrometer. Amazing what efforts we are willing to go too for our air gun addictions. Dale

 

[nced]

I do wonder what the final dimension of a pellet would be after travelling trough the bore (and perhaps the choke) then hitting an incompressible liquid, however this is how I measure my pellet heads after sizing. First I start with a good digital calliper and check the accuracy with one of the "test bars" from my micrometer set............

I set the micrometer to measure mm and check that the gage reads 0.00mm when closed.
Then I take a pellet, set it's base on my Formica table surface. The calliper has a couple reference marks on the jaws so I'm always measuring the pellet head at the same position on the jaws. Then I SLOOOOWLY close the calliper jaws while moving the open jaws parallel with the pellet. When the pellet just starts to move with the pressure of the jaws the reading is recorded. Here are a couple pics..........
Calliper flat on the table so the jaws close only on the pellet head since the pellet skirts are normally a few .01mm larger than the head.......


An unsized die "B" CPL pellet head..........


The results after measuring a few thousand 8.4 grain JSB Exact pellet heads..........


Notice that all these pellets came from tins marked 4.52mm. I really wasn't concerned that the dimension had an exact 1/100mm accuracy (.01mm= 0.0003937008in), simply that the pellet head fit the leade of my springers without "loose fitters". Careful sorting with an accurate calliper does address the "fit issue" adequately for my purposes. Matter of fact, rather than sorting Exacts and FTTs they tossing the "ill fitters" I opted to take die lot marked and dated Crosman Premiers from the 1250 count boxes and size the heads to either 4.52mm or 4.48mm (4.52mm for my R9 and 4.48mm for my HW95). This way I can shoot almost all CPLs with few "culls" since most CPL heads from my latest die "B" stash measure 4.54-4.55mm.

A few hints measuring pellet heads...........
1. Pellets aren't always round and many vary .01-.02mm in diameter if measurements are taken 90 degrees apart on the same pellet head.
2. It takes practice to get a "feel" for a consistently light squeeze on the calliper jaws. Lead is soft (even hard lead Crosman premiers) so it can deform with excess pressure which affects the reading.
3. Your shot pellets should mimic the bore of your airgun so they should be round within the limits of the bore/rifling geometry unless the impact with the water alters the dimension.
4. My suggestion is to carefully push the pellet through the bore (if possible) which will retain the actual geometry of the bore/rifling.

5. For what you're trying to do perhaps the "holes in a plate" would be your simplest choice. Seems that according to the reviews even "outta round pellets" can be sorted accurately enough to improve the accuracy at the target! Also it seems that "holes in a late" doesn't require any "operator finesse" which is definitely needed when using mechanical measuring devices!

 

[Zoey]

Thank you for the detailed explanation and photos. Unfortunately, the method will not work to measure lands after being shot. For the time being, I am putting slug measurements on the back-burner.

The PelletGauge arrived, which is a breeze to use and quick. I divided all of the pellets based upon head size, then subdivided those by weight. I decided to wait for my chronograph to be delivered before I shoot as I would like to evaluate speed as well. Additionally, I would like a more definitive answer to as when my gun falls off the regulator.

One thing I wish I had done was wash the pellets prior to starting this whole ordeal. This would have been my idea of the order:
~Wash, lube
~Yrrah roll
~Measure head sizes
~Weight
~Shoot w/chronograph information attached to each pellet

After shooting, I will post the results.

Unfortunately, being that I am using only one particular pellet, this lengthy process may not lead to the desired results. Thus, I may end up repeating the trial with numerous other pellets.