How to Improve My FX Crown MKI for slugs

[Long_Gun_Dallas]

Cant comment on the heavy as I have a 500mm superior and 700mm slug A

700 over 600 should get you maybe 30fps

I have some .177 nsa's currently, and the same damn thing happens with mine. Super tight groups, and then I'll get a flier. Consistently. I tried opening of the choke on my barrel some, but the results are the same. I have some griffin slugs now I need to test out. But have been waiting for it to get a bit drier in these parts. .177 slugs hitting wet ground actually do make a supersonic crack i suppose from moving water/dirt past the speed of sound.

 

[lamarkeiko]

It's been some time since I've shot from 100 yds, but yesterday I tried some of my NSA 33.5 gn slugs at that distance and got my first ever 5 shot MOA of 1" group. One thing I've done different, and I need to experiment more doing, is I've cleaned and sorted my NSA slugs. I found a lot of lead flack mixed in the slug package, so I did a cleaning by rolling the slugs on a clean towel several times until not much more flack showed up. I then did a close inspection of each slug for any deformations, and eliminated the ones that looked bad to me. To my surprise I found close to 50% with a wrinkle running lengthwise on the side. I shot a few 75 yd groups with the slugs that had wrinkles and a few groups with the slugs that appeared good to me, and the good slug groups were better. The good sorted slugs had groups under 1" and the sorted wrinkled slugs were about 1 3/4". I need to test more to see if this stays the same.

I do think I will be investing in the new 600mm Heavy liner and also a Huma Dual transfer port soon. One question I have is do I need to get a matching pellet probe with the transfer port? Utah Airguns sells the transfer port alone or as a set with pellet probe and transfer port.

Lamar

 

[Longrange2]

This thread is going to be bad for the budget, now I’m thinking i need to pick up a Crown in 22 and work it over for slug shooting. Almost bought a down but picked up a Maverick 25 instead.

 

[knifemaker]

I can't attest to the difference in accuracy between the superior and superior heavy, However I did the same test with the Brownell's liners in .223 that were 1-16 ahd 1-20 respectfully. the 1-20 won, much to my surprise in all weights I tried from 22 gr thru 39 gr. 



As to the difference in accuracy between slightly wrinkled slugs and smooth, this is something casters learned along ago. I have had many new airgun casters ask me if it would not benefit ordering their molds from makers that will make the mold to an exact size to the land's. Well, NO it won't be a good idea. No slug comes out perfectly round when casting and even swaged slugs can have as you have learned. It is often said that Swaged slugs are perfect, where cast are not. Uh-Not! Sort then for yourself. Same as die stamped pellets, there are imperfections 

I would suggest for top accuracy, ordering slugs 1 thou over sized and actually sizing them down to exact dimensions. A bonus for those that need more speed, sizing to .0001 under land dia. will often pick up 25 t 35 fps. Most fear that the slightly undersize will not seal well and cost fps. However, the lower friction more than makes up for it. (A precision sizer will always produce a superior projectile). I by sizers under size two at a time, and hone them and test every .0001 removed until top accuracy is achieved, and continue honin until accuracy drops off. Log it, and repeat to the logged top accuracy numbers and stop .0001 under and final polish to exact size. No lube is required using a fully polished die while sizing. The part of the slug that is sized comes out a full mirror.

One huge advantage of cast is less friction as well. Since there are driving bands, or lube gouves if you will, less of the actual slug body is touching the bore, hence much less friction + Higher fps for a give air pressure, and bbl. length. . It's just a LOT more work. GRRRRRR!!!!

.25 hand cast at 40 yards. Not a great barrel. Simple 20 inch L/W with choke removed, near 1-18 twist. Wind there as we3ll. so slugs can perfom at short range,just has to be the right combo as posted i this thread. 

They are still indeed more accurate at longer range however, but perfectly suitable here at 40 yds. . No vermin is save. 
Gr. is incorrect got rid of that scale. It was 50 gr before hp and decking themold. Iti is now 40 gr. The Shineys are 36 gr in .224 as cast, and size to .2234 for thBrownell's liner, and .2186 for the FX Superior Heavy. 

Knife

 

[knifemaker]

Long Gun, the choke in the FX offering is designed for the Hybrid which swages down in the bore when fired much like a pellet as it is hollow. For most slugs, and higher average higher accuracy without those darned fliers, Remove the choke. 



My nex Barrel with be a 700mm in order to not loose the length I am wanting after removing the choke. Even bbl. I have tested, regardless of brand or maker of the slug, , if it had a choke, accuracy improve dramatically with removing the choke, polishing the bore, and re-crowning.

Knife/Mike

the choke on the Heavy liner was far too tight. .005" Most makers use between .001 and .0015, Here are the results as rec'd form the factory and after choke removal and light firelap, hand polish, re-crown and polished crown. 

A yu can see, it is dramatic. Shotgun pattern is 50 yards. Tight group is 1 shot to settle the reg. (Lower hole) and 10 on target at 80 yards. As you can see, it is dramatic and what can be achieved by removing a choke.

Mike/Knife 

 Please excuse the fliers, injured my shoot'n hand and had to shoot with the other. but to check consistency even in the typical texas winds I shot 60 slugs at 80 yards. Kinda made it hard to keep center as the center was gone. LOLView attachment DSC02497.1614695999.JPG

 

[Khornet]

Never had a .25 or a Crown, only a .22 700 mm Impact, but speaking only for myself, going forward, I will try everything that is reversible before doing something permanent. My pellet liner is now an expensive paperweight after bonding a CF sleeve. I should have first fiddled with the O-rings before doing that. Sure looks cool, though. Not that CF sleeves can't work, just that they're permanent and you're SOL if it makes things worse.

 

[lamarkeiko]

Knife,

Thanks for the great information to work with for shooting slugs in my .25 cal. Crown. I checked the Brownells sight you gave, and I don't see anything for .25 liners. Are only .22 cal liners available there? They would be my first option if I could get the .25 liner in the 1-16 or 1-20 twist.

If that is not an option, that leaves me with the FX Superior heavy liner which is 1-18 twist, and sounds like the proper twist I need. You mentioned that you already tried that liner and it didn't shoot good for you until you removed the choke. How far down from the muzzle does the choke go? If I purchased that liner and I don't have better results than you, that will leave me with having to do what you did to get the accuracy I want. Then I'll need some guidance on how to do the lapping necessary. My other thought, which may be way off line, is if the choke on the FX liner is only a couple inches from end of muzzle, what if the 700mm .25 cal Superior Heavy liner was purchased and It was cut down to 600mm, removing the choke, than recrowned to fit my 600mm barrel? That's my wild thought. Thanks for any input.

Lamar

 

[jps2486]

I know you have a .25, but I'll just pass my experience on my .22 MK1 which may help. Mine has a 600MM Superior barrel and shoots JSB 25.39 gr Knock Out slugs the best of anything, slugs or pellets at 50 yards. My reg is set at 150 bar. JSB now has 25 cal KO slugs available and I would start with the plus the Superior barrel. Frankly, I would not be too anxious to try out those real heavy slugs being sold. This gun is about up to it's maximum with the lighter stuff.