sizing die

Dies for our purposes are usually special order. Lee will make you a die to your specified diameter.

You just order from their custom option and specity the size you want. They have made me 25 caliber sizing dies from .247 to .258 in .001 increments. Takes about a month to get them depending how busy they are.

When I was looking at pellet size and such I emailed the firearm manufacturer. Both told me land/groove measurements and suggested pellet sizes at 0, +.001, +.002

BTW, I'd get a set of calipers or cheaper/faster a PelletGauge. You can't put a .446 pellet into your die and get .451.

Maybe of some interest to note that as mentioned by sharroff, you might have a pellet that the head is smaller than your groove size. However, skirts always tend to be larger than groove and can benefit from being sized to the bore. As long as the head is atleast just slightly larger diameter than lands, you could still get good accuracy from such a pellet.

I shoot JSB monster .22 cal from my custom .22 marauder. Due to a slightly oversized bore that needed lapped to get it shooting, I ended up with a groove of nearly .218. Heads of the monsters are not .218 thus only the skirts get sized in my .218 die and every now and then a head just kisses the die but most are under .218. This means the head rides the lands while the skirt rides the groove/bore. Suprisingly, this combo has worked out to a very accurate 100 yard rig. Sometimes you find an anomoly that you are convinced based on conventional wisdom should be tossed aside as trash. Every now and then that anomoly like my .22 bore shooting monsters proves to be a diamond in the rough!!

"You can’t put a .446 pellet into your die and get .451."

What would it take to compress the pellet head to the same or larger as the groove size? Can it be done without compromising stable flight (getting the skirt messed up or the head out-of-round)? Should it be done/does it matter?

I've never tried it, but to make a .446 pellet head go to .451 I'd think you'd need a decent amount of pressure from directly inside the skirts and behind the pellet head and you'd need a die for the pellet head to fit into so it can expand. Might even need to heat the pellet / die to help it along.

At that point, I think it would be better to have a custom full pellet die made and melt down junk pellets and make your own. Sounds like a lot of work there too (and probably $$ for the custom die) but I'd bet someone out there does that.

Thank you sharroff, yes it seems complicated to do it with an existing pellet and it sounds expensive to create a pellet from scratch. Ajshoots mentioned that sizing the skirts only in the cases where the pellet head is smaller than the grooves provides not much difference in accuracy. So based on that is it safe to conclude that the pellet skirt expanded in to the groove is what really ensures accuracy while the pellet travels inside the barrel? And the pellet-head just kind of being towed forward on the barrel grooves like sliding on "rails"?

I think that is probably going to depend on the rifle. In my .450 rifled barrel, head size makes a big difference. Even on the .446's that shoot really badly in my guns, the skirts are over .457 so the have to be getting sized down once they go from breach to first lands and grooves.

Though I have no way to know for sure I'm guessing the .446 head is 'bouncing' off the barrel and getting nicks/deformities vs a .451 head which stays in contact with the barrel and doesn't 'bounce'. The difference at 50 yards with the same tine of pellets goes from over a 4" group to a one rough hole group. Same day, same conditions, same rifle, 50x scope shot from a bench rest. Variation was all pellet.

Now maybe in a smooth twist barrel where the lands and grooves aren't in contact that long, it would be a different story. If someone wants to send me their .177 FX with a smooth twist, i'd check it out

Also if there is a very seasoned shooter reading this that has a FX smooth twist .177 that can group into one hole at 50 yards and wants to do the work, I'd send them a sample of these pellets and see what they come up with.

By the way, that single hole for the Barracuda .451's had 10 pellets go though it...

I experimented with trying to make small diameter heads larger and was successful, but way too much work. fe7565, sizing head and skirt both to actual bore/groove size seems to be a rather well documented proven way to go. The key is to get a very accurate groove measurement when slugging. I used to buy 3 dies for a barrel. Actual groove size "0" and a +.001, and +.002. I no longer buy anything but actual groove for pellets. Now, if we start talking about bullets, then +.001 upto maybe +.003 could be needed to get a good seal inside the bore. Since bullets don't have skirts to seal to the bore, you have to have a bullet with enough diameter to seal. I also hope that it is clearly understood that sizing and rolling are more of a long range benefit when trying to extract every last bit of accuracy. For 50 yards and under, I just shoot straight from the tin.

Also keep in mind that while you guys are talking .177 All of my sizing is .22 and larger. Knowing the large variance in head sizes for both .177 and .22 makes all this much more difficult. I can run JSB .25's, .30's, and .357's and never have a single pellet that has a head smaller than what I need to size too!! .22 has been a big struggle for me as I have a bore that is a bit big. For .177 and .22, I would sort to find pellets that could be sized to my needs and use the rest for plinking.

Ajshoots,

In .22 at 40 fpe I take Air Arms 16s or JSB 18s out of the tin and shoot to 50 yard into one rough hole. I haven't found a pellet I can take from a tin and shoot my .177 at 18fpe the same way. And I've tried alot of pellets.

I have the same results with monsters in my .22 at 50fpe. They produce a ragged hole at 50 and have shot amazing at 100 as well straight from the tin. Sizing has given better 100 yard consistancy though. I built a .177 for my wife, but no longer have one of my own other than a cheap springer with open sights. .177 pellets are surely one of the worst in consistancy.

If the pellet shoots very accurate straight from the tin, then die sizing as you said can aid in consistency at longer ranges. But if none of the standard factory pellet sizes are consistent and accurate, then die sizing to match the barrel's characteristics seems to be the thing to do.

I am still confused about pellet-head vs groove size vs pellet-skirt. In the case of a pellet-head smaller than the groove diameter, only the skirt gets sized to the groove's diameter size. But even if the skirt does not get sized, when the pellet is shot out of the barrel the pellet skirt still expands and seals up to the diameter size of the grooves because it's thin and it was designed to expand with pressure behind it. So skirt sizing may be trivial? (albeit does not hurt) Then you still have the pellet-head sizes that can vary from the same tin. If they all have heads smaller than the groove size (as in my case 0.252in groove vs 0.249 pellet-head) it seems the only thing that's uniform is the skirt size after it expands.

What about the choke? Doesn't the choke size the pellet again right before it leaves the barrel? I would think that by design the pellet-head is never smaller than the choke? 

What barrel do you have that measures .252"? What pellets have heads of .249?

It's a CZ barrel on a .25 Vulcan. Using a caliper and a 20x jeweler's magnifying glass I tried my best to make sure the caliper is on the top of the grooves 180 degrees apart, and next that its also within the grooves the same way. The measurements: 0.246 (6.25mm) lands and 0.252 (6.4mm) grooves. 

I measured a .25 (6.35mm) JSB 25.39gr pellet head and skirt. The skirt measured 0.255 (6.50mm) and the head 0.249in (6.34mm).

Ok. Most of the .25 barrels I have messed with are .243 land .250 groove. I haven't bought jsb's for a long while as I have thousands. All went thru my .250" die and all heads were sized, so all had heads above .250.

Don't have a good answer as I have a similar issue with my .22 as described above. I still size skirts though.

It's very likely that my caliper measurements may be inaccurate no matter how carefully I tried. I will try to measure against a known diameter and see if it may be off a fraction. Maybe I will try to measure a U.S. coin.