Sizing Question

In my experience, head sizing can work to increase accuracy in many rifles. If the head of the pellet is sized to lightly slide down the lands of the barrel - with minimal engraving - and the skirt size fits the grooves so that the pulse of air expands it enough to form a seal with no blow by - consistency in velocity and accuracy will follow. Of course you must start with good quality pellets. Cheap pellets represent false economy. They will often give fair accuracy out to 25 yards, but at longer ranges the difference in price will begin to show up.

Unfortunately, most pellet sizers only trim the skirt. Even worse, if you set them to size the head, the skirt will be sized too much to form a good seal. A couple of Brit vendors make sizers with a tapered bore that allow you to size the head only - to fit your own rifle precisely. After the head is sized you can use a skirt sizer - such as the one sold by Beeman to lightly trim the skirts for uniformity.

If you can't find or can't afford one of these precision head sizers, there is an option. Reputable pellet manufacturers, such as H&N make pellets with head size stamped on the tin that are close to reality. If you buy four tins of a good pellet ( I like FT&T ) - say 4.51-4.54 (.177) or 5.51-5.54 (.22) and try each size, you will probably find one that shoots better than the others in your bore. Then a tiny haircut with a skirt sizer and you have, hopefully, accomplished a noticeable increase in accuracy.

Lubricating pellets can also enhance accuracy - but that is a whole 'nother discussion.

Have fun!

With only on sizer its a luckgame to have good results

I have to size my skirts to 6,38mm fro 6.40 mm the scatter cirle is alredy larger

With original skirt size looks like shootgun profile to 30 meters

Buy a tin of the biggest H&N FTT in whatever caliber you're using. They come in say 4.50 through 4.55 for .177. 

So get some 4.55's. Shoot a few (10) at lowest possible power into deep water or a non deforming box of plastic bags. I can set my PCP'S so the pellet barely makes it out of the barrel if needed. Your skirt will NOT be blown to optimal size at this low setting but your head will be sized to your barrel & choke. Read all 10 with micrometer or calipers. Take several readings on each pellet. Add them, divide, get the average.

Buy something like this baby right here.

this HTML class. Value is https://www.trrobb.c

Compared to non available Beeman sizer that go for around $160.00 this is a great deal. You can buy one for every caliber & not worry about various dies. Just experiment and set the depth. I have Starrett micrometers & depth gauges so I can get stuff consistent.

The sizes that trim the skirt, I'm not too sure about. Yes, perfect fit of head, skirt, consistently would be best but a skirt is blown out & resized at choke. A perfect crown & an air stripper built for your rifle will enhance accuracy. You've also got to consider weighing the pellets.

JamesD : the link for the adjustable sizer got truncated. This should work.

https://www.trrobb.com/product/adjustable%20pellet%20sizer%20177

I bought a sizer and have not really seen a lot of difference in group size or accuracy. After thinking about it, I wonder if the act of loading the pellet into the breech is all the sizing that is needed. Your comments, please.

Click to expand...

Your question is really two questions. Taking the first implied question: Does head size matter?

Some years ago I did an experiment to answer this question and the pics below summarise some of the dat as far as it went. It certainly suggested that head size can matter. There was little difference from "tin" size of 4.51 down to 4.47 with 4.50 as possibly the optimal? At 4.44/4,45 the group was a little bigger. At 4.43 it had lost it and was considerably larger and 4.41 even bigger. So that answers the first question.

25 yards:



Now if we consider/speculate as to reason, my conclusion in this case was that at some small size "break point" point the head was not stably locating within the lands of the rifling and so was allowing for some yawing motion in its travel within the barrel and that was allowing for shot-to-shot attitude variations when leaving the crown. Hence the shotgun spread.

Your real question: Unfortunately I didn't then have any large headed, say 4.53 or 4.54 or larger pellets to really test your OP question at that time. But later when they were available it became obvious to me that groups were not so good and that the larger the heads the less the action of forceful chambering, as a sizing method, was able to consistently produce groups as good as when carefully resizing to 4.50/4.51 for that RAW TM 1000.

My speculation leads me to believe that overly large heads are difficult to force into the leade consistently without some yaw and that that yaw, too, may be inconsistent in its attitude. Downsizing may be accomplished but not necessarily concentric to the pellet's central axis. ... Careful head sizing to optimal for any given barrel land ID may therefore be advantageous, preferably done either using two or more graduated size sizers or a long tapered sizer like one I use made from a particular old Bic ballpoint pen.

However, when all said and done, each of us must decide for ouselves as to what accuracy is acceptable for our purposes and as to how much time and effort we are prepared to spend to attain it. For eight years I have habitually resized my .25 pellets to just precisely that viz., .2500". And I notice lately that others including some of the gurus too are doing the same. ........ I hope some may find something of interest in this. Kind regards, Harry.