Sizing pellets for FX ST barrels

[greg]

Does anyone have hands on experience sizing pellets for ST barrels?
Wondering if FX's smooth bore is kind of 'auto-sizing' pellets anyway as they are pushed into the chamber by the probe.

 

[ajshoots]

The value of sizing for a st barrel is the same as a conventional bore. I had an st barrel I tested on a marauder .25. I am sure Yrrah could confirm as well.

 

[greg]

Thanks, Aaron. You and Harry are treasure troves of trustworthy information. I hope he'll be able to chime in.

How would one size the barrel for FX ST? Taking a barrel off from Indy is a bit of pain (blow torches and specialty tools are called for)
Do you think I can just load a pellet, push it back out (e.g. with a cleaning rod) and them measure the diameter of the pellet?

 

[ajshoots]

Load a pellet and push it back out to measure. Had a major brain fart with my previous response which I apologize for.

 

[greg]

Being a chocked smooth twist, FX barrel does not produce traditional land/groove marks.

The pellet, as it comes out of barrel upon shooting, is smoothly polished from all sides. It measures around 5.40mm (+-0.01, both head and waist). Same pellet going in measured 5.51 at the head and 5.72 at the waist. Tried with a couple pellets, same results for the exiting diameter s.

The question is, how does someone w/o infinite amounts of time and money find the right die for this ?

 

[ajshoots]

Have edited my posts to correct my error. You just need to measure the pellet after loading and pushing back out.

 

[greg]

"ajshoots"Trial and error.

Decided to follow that advise and order a press with couple custom sized dies (thinking to start with .218 and .217). Alas, Lee is out of stock. Not sure what 'out of stock' might mean for custom sized dies, maybe they no longer make em? Does anyone know another place to order dies?

One thing to mention - when I push a pellet into the breech area of my ST barrel and then push it back out - the skirt measures at 5.53. Now, the potential problem I see is that none of the pellets I have (JSBs, H&Ns, etc) measure more than that at the head (tails are always significantly wider, as you know, sometimes as much as 5.80). Usually, I see 5.49 - 5.51mm heads.

Am I correct recalling that this sort of situation is undesirable? It effectively means I'd only be re-sizing the skirts, and heads will be kind of wobbly in the barrel until they encounter smooth twist rifling (which, as I noted before chokes them to 5.40) 

 

[ajshoots]

I have found the same issue in .22 being that heads are smaller than the groove diameter and therefore only ride the lands. Your issue appears to be similar but with an ST being the smooth bore has a diameter larger than pellet head size. At that point I wouldn't waste the time sizing. Mileage may very, but best results for me have been pellets sized both head and skirt to actual groove size. 

 

[ashes5]

Has anybody tried shooting some pellets into a bucket of water then measure the od's of the lands and grooves for a accurate measurement of your barrel?

 

[ajshoots]

A pellet fired from an ST barrel or any choked barrel will only show the size of the choke or ST portion of the barrel. That is not the size you need for proper die size. You need the groove or smooth bore size prior to the pellet going thru the choke or rifled section of an ST barrel.