Ballistic coefficient of MP molds .25 airgun pellet 8 cavity

[MrP]

Anyone know the BC for the 47 grain .25 caliber airgun “pellets” from the MP mold? These are sold as varmintknockers on eBay.

They are basically little bullets with a boat tail (a tapered tail end I mean) i lack the equipment to check the bc myself. 

 

[TrinityMaker]

I think it's about 0.1 

But.... If you have 2 chronographs, it's very easy to figure out. Speed at muzzle vs speed at target, then run the numbers through the BC calculator. 

Those slugs really like the choked LW barrels with the 1:17.7 twist. But they like to be shot FAST! That's why they perform so well in the AF Condors. The Condor can get up to 100 FPE shooting those slugs. And they can be extremely accurate when shot at proper velocities. 

 

[zan89]

I use them in my Impact .25 shoot them at 930fps and i get good accuracy, better then NSA. I got 700mm and a slug barrel.

 

[MrP]

I found a YouTube video of the guy who was working with Huben and MP molds to make these. I will post a link so you can check it out yourself:

https://m.youtube.com/watch?feature=emb_title&v=CodtHHnTT9o

They are specifically designed to work in choked LW barrels... also they are stable at lower and higher velocities. They say the pellets have excellent accuracy at 700fps (but of course a less flat trajectory) and up to about 1000fps.

 

[Ydunn.223]

I use them in my Impact .25 shoot them at 930fps and i get good accuracy, better then NSA. I got 700mm and a slug barrel.

I've seen this posted before that they shoot good from a FX Impact " I need to try these in my Impact "

 

[MrP]

Got to say these pellets are a perfect match for my TalonP, even though it won’t shoot them much past 725 FPS. Very accurate this speed. Groups at least as good as any other pellets on hand. I am shooting off hand with iron sights, for what it’s worth. 


today I tried shooting these at much lower fpe - like upper 30s and lower 40’s. Just as accurate... 



so for my 12 m range, these are perfect. I was kind of settling for this mold - only .25 I could find - because I couldn’t find any In stock for lighter pellets. I basically assumed it wouldn’t be great for the stock TalonP and would just end up using them with a future more powerful gun. Well, i am still looking for a .25 mold for pellets in the 30 grain range, but for now this is great. I actually like the heavy, lower speed thumping for close range shooting. 

 

[caliusoptimus]

Will these stabilize with 1 in 22" twist? The results from the twist calculator were 1.0ish stability factor based on my length estimate .460

 

[Ballisticboy]

They may do, 1 is the minimum value, but it depends on the calculator and the assumptions it uses, and the bullet speed used in the calculation. With such a marginal stability, group sizes may be large, and the bullet may be unstable in cold weather at sea level.

What calculator did you use and at what speed?

 

[caliusoptimus]

They may do, 1 is the minimum value, but it depends on the calculator and the assumptions it uses, and the bullet speed used in the calculation. With such a marginal stability, group sizes may be large, and the bullet may be unstable in cold weather at sea level.

What calculator did you use and at what speed?

I used the berger calc at 850fps.

 

[Ballisticboy]

It uses the Miller stability calculator, which was intended for highly supersonic bullets. The equations are very basic, use sweeping assumptions, and are not really suitable for subsonic speeds. The Kolbe calculator will give a better answer at 850, but it too gets less accurate as speeds increase to 1100 ft/sec.

You may get away with it at 850 ft/sec, but if you want to go higher, then you will need a faster twist rate as the stability will start to get less. The boat tail will make them less stable and thus needing a faster twist rate.

 

[caliusoptimus]

It uses the Miller stability calculator, which was intended for highly supersonic bullets. The equations are very basic, use sweeping assumptions, and are not really suitable for subsonic speeds. The Kolbe calculator will give a better answer at 850, but it too gets less accurate as speeds increase to 1100 ft/sec.

You may get away with it at 850 ft/sec, but if you want to go higher, then you will need a faster twist rate as the stability will start to get less. The boat tail will make them less stable and thus needing a faster twist rate.

I punched it into a kolbe calc and got similar but alightly higher number. Had to estimate most of the dimensions so it could still be quite a ways off... guess I'll give it a go and see what happens.