0.216, 0.217 or 0.218 Slug?

[Arash]

High. I bought Brocock commander, at first it shoot JSB 18.13 at 268m/s but air usage was a bit high, so I reduce hammer spring tension. Optimal speed was around 263m/s.
Then my friend suggest to use 21.4 grain hand made and it shoot 240m/s. I turn reg pressure up to 150 and it shoot 18.13 278m/s and 21.4 slug 260m/s.
Now someone make a 18.5 grain slug. I want to buy them & dimeter is 0.216, 0.217 and 0.218.
My problem is he sell 6000 slugs in a box. I think I would shoot out this 6k in 6 year.
0.218 is to tight in barrel, 0217 is good but it wont go in like jsb pellet. and I don't have 0.216.
I think brocock use same barrel as daystate. if you use slug for daystate, brocock or any lothar barrel please tell me which diameter your barrel like the most and I will buy most common one.
Thanks.

 

[Joedirt199]

Push one of the .218s through your barrel and measure the size it comes out as. Barrels are not all the same in size.

 

[Arash]

I have done it. I couldn't measure the depth. but the thing that catch my eye was the length of rifling mark on the slug.
for 0.218 the length was 4mm but for 0.217 length was 3mm.

 

[Keyman62421]

Shoot some groups. That's the true test.

 

[Arash]

Shoot some groups. That's the true test.

I used both but I couldn't get a good result. because of that I want to buy 18.5grain

 

[Keyman62421]

880 fps + or - is generally agreed proper speed
I'm talking about pellets. I believe your dealing with slugs. They shoot faster.