Smooth twist and swagged pellets

My friend in Florida who makes a lot of my cast bullets tried bbt 40 grain .252 in his fx impact. .252 fit the smooth portion of his barrel near perfect. However, grouping was 11/2 @ 30 yards. But loved the eunjin 43. If you or anyone finds one that works, please post.

The problem with the smooth twist barrel and bullets is that bullets are spin stabilized. The effective spin on the pellet is not really sufficient to stabilize a bullet. If the smooth twist rifling has the same effect on a bullet as it does with a pellet it will not impart enough spin. I suspect, that, that will be the case. 

Pellets tend to skid before they start to spin in the smooth twist which makes the spin rate slower than what the rifling twist rate actually is. Bullets would have even a greater resistance to spinning due to the additional mass (mass moment of inertia). However, given enough bearing surface the bullet may grab more than a pellet. This would be a delicate balance, I think, to have a bullet with enough bearing surface without too much additional friction going down the bore.

Any updates?

oneshot61My friend in Florida who makes a lot of my cast bullets tried bbt 40 grain .252 in his fx impact. .252 fit the smooth portion of his barrel near perfect. However, grouping was 11/2 @ 30 yards. But loved the eunjin 43. If you or anyone finds one that works, please post.

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Hi oneshot
Look.forward to your findings,may i ask if you know what velocity the 25 impact was pushing with the 43 gr eunjins,and also did they fit and feed ok from the impacts mag??
Rgds steve

He said 870ish. I don't think that was full power either. I'll try to find out his settings.They did not fit in his magazine. 

Hi oneshot
Thanks for that
Rgds steve

I'm shooting 47 gr EPP slugs (Nielsen specialty ammo) in very tight groups out to 50 yrds (max space available) with a Bobcat mk2 .30 cal. At 20-30 yrds they're stacking...as distance lengthens they group slightly to the right.

Hey guys, I’m kinda new to this site along with airguning. My first airgun, Hatsan bt65 .30 carnivore, not high end but the power and accuracy was definitely there. I then began testing slugs through this rifle, the accuracy was terrible. I was not disappointed, I just thought it was worth a try. Now, on the other hand. I recently purchased a Fx Bobcat Mk2 in .30 cal, I’ve not shot a lot of air rifles but... honestly by far this gun is definitely the most accurate. After weeks of shooting the urge hit me again, I thought to myself. With a diablo pellet, though this gun shooting sub moa at 100yds. Surely the slugs will have to at least be worth the time, at 60 yds I can say the time was definitely not wasted. This gun will definitely put the slugs in the exact same place as the pellets, with of course alittle more hold over. My question is, why do I read so many reviews saying not to shoot the slugs through the smooth twist?

Swaged ✔

Swagged ✘

The ST and STX barrels are chocked is why you read that. A slug barrel liner is due out this month.

A friend I know shoots a slug from his FX Streamline and he is 

very happy the power was turned up on the gun and he hits GS

all the time at long range . He sends pictures to me all the time .

I tried the Nielsen hollow points outta my WC MK I and had excellent results out to about 85 yards, just hadda use a little more hold over. Kept em all inside of a tin can at that range anyway.

Being that these barrels are choked, does that mean there is a possibility of damaging the barrel? Or, does it mean that the slugs will be less accurate?