Slug recommendations for M3 .25 700 sniper for new M3 owner

After 3 months on the preorder list for the FX M3 .25 700 sniper, I finally got the phone call to customize me M3.

This is my first FX and these are options I choose .The Superior Heavy liner, Carbon fiber liner sleeve and the slug power kit. I choose these options based on many hours of research. I hope I made the right choices. 

My range has targets as far as 200 yards and I designed the M3 to be a dedicated slug gun for 100+ yards. I have other pcp guns for 100-25 yards when needed.

With initial distances of 100-200 yards, what slug and grain weight should I start off with?

Thanks in advance. Rod in San Francisco
 
Thank you for chiming in. I did some research online which also confirmed qball recommendations for 34.9 and 38.9 grain slugs.

I also read that 43.5 grain is worth a try. All 3 slugs have been ordered thru the NSA website. $7 shipping wow!



The m3 arrives in 2 weeks and I will report back later.

Rod in San Francisco
 
I've got the m3 and just swapped to 25 cal in sniper. Had good luck so far with nsa 38.5 grain slugs. Have not done extensive testing at long range. Buy a box and give it a try. 



Mine is shooting those at 975-980 fps. Very small extreme spread. I left some notes in the thread regarding details in the m3 tunes here topic at end of page 8. This tune makes the regulator gulp a lot of air between shots and I've seen that waiting about 2-3 seconds between shots requires the low standard deviation. So it may not be ideal but it's definitely providing the power I desire at the moment. Need more time and ammo to improve it. Currently get a full mag at least, to about 81-82 ft lbs (biggest bottle). I think it could be outdone with more time.. 

https://nielsenspecialtyammo.com/products/38-5-gr-hp-fb-25-cal



Thread https://www.airgunnation.com/topic/your-m3-tunes-here/#post-1174894



Oh and yes, I do have the heavy liner...