How to Improve My FX Crown MKI for slugs

[lamarkeiko]

I have an FX Crown MKI in .25 cal with an STX 600mm Superior liner installed. I've been shooting with fair success NSA 33.5 and 36.2 grain slugs. I'm tuned now at 135 bar, hammer 5 and getting about 820 fps. I'm not interested in purchasing another rifle, but wouldn't mind spending the extra $400 for another 25 cal light 700mm barrel with a Superior Heavy liner if I could improve velocity, but mostly accuracy. I know I could just get the 600mm Superior Heavy liner for $109, but would that give me an improved accuracy shooting these slugs. As a side note, I've tried the FX Hybrid slugs already, and they don't shoot any better in my gun than the NSA's, and they are too overpriced for me.

Lamar

 

[Long_Gun_Dallas]

Get some griffin slugs. Get some that are on the shorter/lighter side. Get a superior liner, and a carbon fiber tube to bond to the liner from Earnest Rowes custom shop.

The superior (not heavy) does well with lighter weight/higher speeds. The carbon tube makes the barrel less tune sensative. More accurate overall. 

 

[jps2486]

Several of us have had good success setting the reg at 150 bar and shooting 25.39 gr JSB KO slugs. One of us has a B liner and I use a Superior. Both 600 mm.

 

[Ghostranger169]

If you're only shooting 75 yards and closer, you may have success with some of the lighter .25 slugs. From my experience testing, an unmodified Crown MK1 with hammer spring maxed out and regulator set to match(140 to 150 bar) just barely has enough power to accurately shoot the lightest of .25 slugs out to 75 yards. Beyond that the group sizes really open up.

The .25 King Heavy MK2, however, can be accurate out to 100 yards shooting as low as 790fps(they won't buck the wind as well as shooting them at higher fps and have a loopier trajectory, tho).

You would have MANY more options options and the ability to shoot good groups out to 125 yards, if you bought at .22 caliber change kit with 600mm Superior barrel. As jps2486 stated above, many Crown owners are having success shooting .217 JSB KO slugs(as well as NSA, H&N, Griffin, etc.) out of 600mm Superior or Super Heavy liners.

 

[stoti]

The slug A liner is super accurate with the 700mm and the new NSA 34.9gr slugs at about 945fps. My son shoots the 700mm Superior(standard) liner with the Hybrids at about 930fps with great success too. 

As Ghostrider mentioned, you could just switch to a .22 which would get you over the velocity hurdle that I’ll talk about below. If you are shooting inside of 75yds, I wouldn’t even bother with slugs, not even the lighter ones. Slugs do buck the wind better at any range but aren’t necessary inside of 75yds. Borderline inside of a 100yds unless there is wind. There are some slugs that are close to surpassing diabolo pellets in accuracy inside 100yds but they are very rare. Although there are a couple of very, very accurate slugs in close and at distance, the majority of pellets shoot better than 99% of slugs. When I’m talking about the rare exceptions, I’m talking about Mike(Centercut’s) results with the 43.5gr NSA and Mike Thomas(owner of Thomas air rifles) results with his new .22 caliber slug rifle. They are super accurate inside of 100yds and past 100 too. It can be done but day in and day out, the best pellets will shoot better than the best slugs inside 100yds.

I agree with Dallas in that the carbon tube can stiffen the barrel system that FX uses, however, if the gun is accurate to begin with, it’s affect on harmonics isn’t nearly as noticeable. I tested both the liner mod and the shroud mod at the beginning of last summer and the results weren’t impressive. I then tested it again 2 more times with different sets of liners and wasn’t impressed. I think the problem is that my gun was so accurate to begin with, there wasn’t much room for improvement. Since then however, a lot of people have had great results using the liners. The positive results speak for themselves, just wasn’t my experience but my testing was done 8-9 months ago. Definitely worth doing if it’s in the budget! 

Paul also mentioned a regulator setting of 150bar. With slugs, I’m a big proponent of speed. Although some say they have good results at lower velocities and of course there are exceptions, the majority of slugs prefer faster velocities, usually between 900-1000fps and more specifically usually between 920-960fps. This is because most FX liners have slower twist rates for diabolo pellets that are mainly stabilized by their center of pressure being behind the center of gravity caused by the flared skirt. The shuttlecock analogy. With slugs that are spin stabilized, a faster velocity is often needed to get them stabilized with slower twist rates. The Superior liners have addressed this to a degree but speed doesn’t negatively affect the stability of a slug nearly as much as a diabolo pellet. For this reason, it’s advantageous to start faster and decrease velocity in your testing. This brings us back to Paul’s suggestion of a higher regulator pressure...Slugs also seem to shoot better with high regulator pressures and high hammer spring settings. This gives a short, fast burst of air that is most often, finished expanding or almost finished expanding by the time the projectile leaves the bore. It’s also more efficient and more quiet. Why slugs prefer this over a longer, slower burst of air, which is also less efficient and louder, I don’t exactly know. I’m assuming it has something to do with the turbulence around the slug as it leaves the bore but I can’t say for sure. The point is, try setting your gun with a high regulator pressure and high hammer spring setting. After you’ve tested thoroughly and are getting close to getting the gun dialed in, you can always back it off for best accuracy, I’m just suggesting a starting point. Because when you turn up your regulator pressure, there is more resistance in the form of back pressure, you need to turn up the hammer spring tension. Even with this change, you may still need a heavier hammer or hammer weight to aid in opening the valve at higher regulator pressures. 

The first generation Crowns weren’t really set up for shooting slugs, believe me, I tried. My slug testing journey with FX liners started with a Gen. 1 Crown and a 600mm liner. You can however, get a new, 700mm liner which will increase velocity and accuracy. You could also get a larger valve, which will allow for more air flow. I’m not sure of the size you can use with your current valve pin though. I think the original Crown’s valve opening was 5.57mm and the new opening is somewhere around 6.35mm I think the newest Crown has a larger valve and valve pin, if they are interchangeable, that would be your best bet, you can check with Newman or Ernest at FX. I haven’t had my Crown for a while. You can also increase velocity a bit with a modified probe or a pin probe and also by switching to a dual transfer port. 

All of these little things will increase velocity for you which I’m assuming you will need to shoot slugs more accurately. You never know, you may be lucky and be one of those guys that has success and super accuracy at lower velocities. I’m just suggesting things that will help. What you choose is up to you. If you just want to go with a new FX liner, the 700mm length will add a little velocity, if it’s enough for your needs, I don’t know?

Good luck and please keep us informed on what you choose to do and if it turns out well for you. Testing and shooting slugs is similar to golf in that it’s super fun but often frustrating! It’s a long, never ending process but that process is the fun part! 

Sorry my response is so long. I have a bad habit of doing that and I realize it’s no fun to read. I wanted to be thorough and concise though!

Have a great day!

Stoti



Below are just a few of the great slug offerings now available. Also, my FX Crown gen.1 when I started testing slugs in the FX liners.

 

[Ghostranger169]

This guy may have more experience testing .25 slugs than anybody on the forum. Wealth of info there, stoti! 

 

[Long_Gun_Dallas]

I think the key, really is keeping the liner on that harmonic node. But stiffening it (through bonding carbon tube) makes the wavelengths less pronounced. Giving more leeway in the gun's tune. It's been proven that the superior liners are less ammo picky. And test results also pointed to it liking faster speeds as well, but that was not definitive. But I can say that mine in current config is exactly that. Not ammo picky. And consistently accurate at velocities around 950fps. (I can turn it up faster, but see no need)

Fundamentally, we always want low valve dwell time as this will reduce harmonic vibration, and turbulence. That is why the higher operating pressure is often recommended. Now, the impacts are unique in that valve travel can be forcibly stopped short (effectively tuning/controlling dwell). With large plenums, a lot of power can be extracted from lower pressures due to the increase in volume of charge exiting the valve.

If your barrel and projectiles are not in agreement (too long for too slow of twist, or too fat for whatever choke or bore diameter there is) You're gona have a bad day. So that is baseline. You have to have that first and foremost.

Power always helps. Port massaging, and in turn, matching the probe will net some bump in efficiency. I still would like to know if the new valve/seat can be used in the gen 1 crowns. I do have some large ones for my gen 1, but opted not to use them because my 5.5mm valve is already big enough (for .22 caliber)

 

[stoti]

Dallas, my son’s Maverick with the 700mm Superior is also not pellet or slug picky and he shoots even pellets at about 930fps. The first Superior liner I had wasn’t like that but it shot the FX Hybrids better that I’ve seen any liner shoot any slug, absolutely phenomenal.

You said you have some spare valve/seat what are the sizes of the old vs. new larger Crown valves? Are they 6.35mm or can you get larger? If he can use one of the larger versions in conjunction with a 700mm liner, modified or pin probe, dual transfer port and higher settings, I think he’ll have the velocity to shoot any of the NSA slugs from 29gr to 34.9gr. with enough velocity to be accurate.

When I did my carbon sleeve and carbon shroud testing, my gun was about as accurate as it could get. I know it tightened up the rigidity but improving accuracy was my goal. Since I was already perfectly tuned, no gains. I’ve wanted to try some new things I have in mind with carbon tubing again but my gun is so dialed in with the 34.9gr slugs now, that I don’t want to mess with it. If someone is having trouble finding the node, the carbon liners are a definite advantage(rigidity).Since the OP is just starting his testing, I would say with 99% certainty, it will help. Do you tension your barrel/shroud with an outer carbon tube too? If so, do temp. variations affect POI? When I do finally put on a new carbon sleeve, it’s going to replace all of the factory parts. I’m thinking it will be 5-8mm thick when I’m done. It will depend on the thickness of each of the tubes I use and how many. I have a bunch of 1mm, some 1.5mm and some 2mm but I won’t know for sure until I do it and test it though. 

I don’t really like using the valve adjuster on my Impact except so that it’s barely touching the hammer seat. My current set up was at 960fps, I used the valve adjuster to drop the velocity to 944-946fps. It’s super consistent that way. I shot a 30 shot string last week with and ES of 2! Got to love that. 

Like I said, I don’t hav my Crown anymore, there’s no way the OP could attach an aftermarket plenum is there? That would really help if used in conjunction with the other things we’ve mentioned.

Have a good one.

Stoti 

 

[knifemaker]

This guy may have more experience testing .25 slugs than anybody on the forum. Wealth of info there, stoti!

While I greatly appreciate Stoti's contributions and admire him, it is not even close to the work a few here and elsewhere have been involved in. Most quietly. Here are a few.

Roach Creek who set a long distance record with slugs what, near 10 years ago at 615 yards. Tofazfou, (You can now find him on youtube is a Long Range King). Jack Haley that built the long range guns for Roach Creek years ago, (RIP). Doug Noble who has been building and shooting very long range for years, R.J. Porter, another blast from the past, and Myself., a student of Roach Creek in both testing, shooting long range and designing and casting for the same and have been testing slugs since what, 2007?



We have all learned the same thing. There were and are barrels out there that are absolutely lasers for slugs. Sadly, FX ignored all the info that was out there. Mostly due to a given tester that had NO Idea what it took and guided FX in a rather hunt and peck odyssey. Thankfully, regardless, it has led to the industry seriously starting to pay attention to slug shooting and FX is making a grand effort. Sadly, it is still a little misguided. What works somewhat well for their literally hollow slug as it can compress to match the bore and choke, no other slug does that. Soooooo, Here we are. Stoti hit the nail on the head, and pointed to a fact that different shooters are having differing results . Why?

Here are what we that are slug shooters have found over the years. First and for most, the same rules apply that have been the standard in lead slug shooting in firearms for centuries. It works exactly the same way. No need to re-invent the wheel here. I can tell you where to get a liner that is more accurate, same od. within a few thou. and dirt cheap with years of excellent performance under it's belt. (Later on this). 

First, Twist is extremely important. Luckily, this has been set pretty much in stone long ago for our .22 slugs. 1-16 for 35-40 gr and 1-20 for 29 to 34 gr slugs. ease peezy. It matters not whether the slug is being propelled by powder or air. Same-Same.

Next, yes some find success with a choke, but darned rare. This is part of the differing results across the forums with people shooting slugs. Particularly FX AG's .Research choke bbl's in .22 fire arms. Other than a few odd ones, or a tapered bore or two, they don't exist. Why, they only work in poor bbl's to fix issues. Not in precision bbl's.

And lastly, every one by virtue of manufacturing difficulty in inventory and complications, has to order by the Thou., and hope it works. It does Some Times, but not regularly. . This is where "BLIND HOG Finds Acorn" part comes in.

Best accuracy most often is found from .0001 under groove dia. the .0003 over. This is the most important thing to know and understand in slug accuracy in AG's, and loose the Choke! the FX choke is a monster. Most acceptable chokes for pellets range from .0005 to .0051. the FX choke in the Superior Heavy is .005+. HUGE. It may work well often with their Hybrid, but very spotty for any other brand which is a solid core projectile. (One would think the .000 under would hurt performance by allowing pressure past the projectile, however the lessenig of friction far out weighs any loss. Gains of up to 35 fps have been seen).

I rec'd an FX Superior Heavy before the public did for testing. The results were terrible until I removed the choke. I lapped, polished the bore, re-crowned the muzzle and it is now ultra accurate. I have no issue with it. If only they would listen to a few of us who have been doing this for a long time rather than an energetic newbie. I admire his enthusiasm, but he isn't quite there yet in practical knowledge.

Now for the best part! Brownell's Gunsmithing Supply has the barrels we need in .223, Not the .218 that the FX is listed as, but in truth is a Real .22 cal. rather than the actual .214+ the FX offering is after the slug leaves the choke. Tons more slugs available for it, and get this, Ultra find finish in the bore and all for 39 Bucks USD. Yep, 39 bucks, and available for both light slugs at 1-20 twist and heavy with the 1-16 offering.

Here are a few pics of what the FX Superior Heavy shot like both before the choke removal and after. and the link to the bbl's at Brownell's.

Added Bonus, as the base of the the slug is larger in dia. from the Brownell's liner than the FX, it is a bit faster with less air pressure as well. Not much, but every bit counts! And ---It fits the same sleeve the FX Liner does. Woo-Hoo!!!

Brownell's link: https://www.brownells.com/gunsmith-tools-supplies/barrel-tools/barrel-liners/22-caliber-rimfire-barrel-liners-prod10974.aspx

Before and after choke removal. 

 At only 50 yards. Now after the work at 80 yards, 1 shot to settle the Reg. and 10 on target. 

 How about 60 shots at 80 yards to check for consistency?

This is what happens when you remove the choke, and a bonus is far less leading!



My writings and test can be found over at the GTA with well over 8000 post and the old tag with way more post.



One last rambling. The slug suppliers cannot provide every size in .0001" so it is up to the shooter to do it. Size to your barrel. Slug it, and size accordingly. Test all four sized. from .0001 under to .0003 over. Work? yep. Too much trouble? That is what pellets are for. Sizers are cheap from NOE Mold services. And have fun as it can be very rewarding in the end! 

Knife

https://www.youtube.com/user/tofazfou

 

[Long_Gun_Dallas]

Dallas, my son’s Maverick with the 700mm Superior is also not pellet or slug picky and he shoots even pellets at about 930fps. The first Superior liner I had wasn’t like that but it shot the FX Hybrids better that I’ve seen any liner shoot any slug, absolutely phenomenal.

You said you have some spare valve/seat what are the sizes of the old vs. new larger Crown valves? Are they 6.35mm or can you get larger? If he can use one of the larger versions in conjunction with a 700mm liner, modified or pin probe, dual transfer port and higher settings, I think he’ll have the velocity to shoot any of the NSA slugs from 29gr to 34.9gr. with enough velocity to be accurate.

When I did my carbon sleeve and carbon shroud testing, my gun was about as accurate as it could get. I know it tightened up the rigidity but improving accuracy was my goal. Since I was already perfectly tuned, no gains. I’ve wanted to try some new things I have in mind with carbon tubing again but my gun is so dialed in with the 34.9gr slugs now, that I don’t want to mess with it. If someone is having trouble finding the node, the carbon liners are a definite advantage(rigidity).Since the OP is just starting his testing, I would say with 99% certainty, it will help. Do you tension your barrel/shroud with an outer carbon tube too? If so, do temp. variations affect POI? When I do finally put on a new carbon sleeve, it’s going to replace all of the factory parts. I’m thinking it will be 5-8mm thick when I’m done. It will depend on the thickness of each of the tubes I use and how many. I have a bunch of 1mm, some 1.5mm and some 2mm but I won’t know for sure until I do it and test it though. 

I don’t really like using the valve adjuster on my Impact except so that it’s barely touching the hammer seat. My current set up was at 960fps, I used the valve adjuster to drop the velocity to 944-946fps. It’s super consistent that way. I shot a 30 shot string last week with and ES of 2! Got to love that. 

Like I said, I don’t hav my Crown anymore, there’s no way the OP could attach an aftermarket plenum is there? That would really help if used in conjunction with the other things we’ve mentioned.

Have a good one.

Stoti

Giving me more ideas to get carried away with (speaking of tensioned bonded liner).  I've got an idea of how to make that work well, but I do not have that kind of configuration currently. I just have mine floating like a standard superlight setup, but with two long sections of CF tube epoxied at full length, at full surface area to the liner. Used acetone prior, so should have a great bond.

The center support is sandwiched, and is there for life. Until it gives out some day. Bur I recon I can 3d print something that will work just as well if I ever need to that would fit onto the CF tube instead.

I've noticed the choke is lighter, and the projectiles that come out of this 500mm superior are SUPER smooth. I thought the STX liner pushed out smooth projectiles 

Yes, I believe I have a 6.3mm seat, as well as a 6.5mm. I was going to throw the 6.5 in when I got my .30 barrel, but the USPS misplaced the barrel for me. No telling when or if I will order another. I've been shooting heavy .177s pretty fast lately, and have been REALLY enjoying it.

I have some larger valve seals, but I had not quite ironed out how to get them to stay put. Once you loosen the collar on the valve stem that holds the seal on, it does not like to stay put anymore. Like I'd need a small choking device to really squeeze the collar back onto the pin. Hmmmm That might be pretty simple to make happen.... just need a split piece of stock with the right size bore. And a press. But at 2000psi, will it still stay put? I'd really like to see a new mkii valve pin.... I'm willing to bet it is a direct drop in, and will probably order one if I get my .30 barrel.

One of my friends has been talking to me about a plenum he is getting that is adjustable in volume. My main issue is that it would only really be useful for shooting from a stationary bench or perch. (which is what he does mostly) Going to REALLY put the bottle out there. But is a solid design to make the gun a REAL powerhouse.

I don't feel the plenum is needed. Though would be useful for sure. I had contemplated getting one made that would come down a little into the trigger guard (there is a bore cap in front of the trigger under there). But would only net about 3cc tops, I believe.

Of course you can install a drop plenum off of the rear gauge port, as well. Similar to some of the first aftermarket plenums for impacts.

I never did care much for the valve adjuster either.... but is a cool feature if you want to REALLY fine tune the gun. I actually have something quite similar on my 1322 pcp, and it's pretty darn handy. But is one more factor that can go askew. Another thing that has a similar effect that I may look into is a peek striker installed in the hammer. Seems to dampen, and create a more consistent valve actuation.

I used to have a VERY tight ES on my crown, but I messed with my reg. too much. I'll likely try and polish it up, clean it out.... I also have spare parts to rebuild if I decide. (it's a huma, but I developed the same issue with the amp from adjusting back and forth too much.) There was also an issue of rough edges on the hammer spring grinding shavings into the trigger/hammer tube. Presumably from the guide. Not sure if my gun ever %100 recovered from that, but will likely look closer and polish there as well.

 

[Long_Gun_Dallas]

@knifemaker It's pretty easy when you keep things nice and simple. I'm not sure if you've had a chance to try a regular superior barrel, but I have been pretty darn impressed with mine.

I agree that for solid core projectiles, there should be no choke. But a choke is what we are given. And I have had them work extremely well, granted with soft pure lead slugs. And with much testing/tuning. My new 500mm superior setup has been shooting dead nuts from the first time I pulled the trigger, though.... I need to get out and shoot it more, and really document some measured results. See what it doesn't like, if anything.

Are those brownells liners close to fitting or does a small amount of boring need to be done? I really wish I could get a cost effective slug setup on my Crown for .177. The .172 liners came to mind because of the barrels you have made/tested.

 

[stoti]

Knife maker, he said the, not me! Like I said, all of my slug testing has been mainly with the FX liners in .25 cal. No doubt others have been testing with slugs a lot longer than I have and have a wealth of information. I have tested almost every slug that is available for the .25 cal from all of the makers and many that are not available from Nick at NSA and Dale at Varmint Knockers. Then there are the FX Hybrids which I have tested too. I have tested all of the FX liners in .25 other than the Superior heavy. Although I have figured out a lot as it pertains to FX liners and .25 cal. slugs, there is much I cannot explain. I was just telling that to Centercut today. What I have learned though, I am always willing to share. I always answer questions when people call, e-mail or message me, I enjoy sharing and discussing slugs, just another facet to air gunning! The slugs and FX liners I’ve tested just scratches the surface of what’s available and what’s possible in the realm of slugs. To me, it’s not about who did it first or who knows the most. I like to shoot slugs and I like to learn everything I can about them. If I figure something out, I like to share it to help shorten the learning curve for others. I’m not always right either, far from it. If someone calls me on something I’ve said or suggested and we discuss it, that’s great, that is a big part of how we learn. 

One other thing that I always tell people is that it’s very, very important to test everything yourself! We share numbers, ideas, modifications and things like that but often times, two guys shooting the same slugs out of the same gun will have very different results. There are just so many variables...reg pressure, HS tension, power wheel, valve adjuster, internal components, lubed/unlubed, polished barrel/un-polished, clean/dirty barrel, sized/unsized, and on and on. Take in all of the information you can and use it as a starting point. Sometimes it will help and sometimes it won’t help much at all. 

Dallas, we must have been posting at the same time... That’s super cool, I should have known you’d have some sweet Crown plenum and accessories in the works. That looks awesome. 

Keep on shooting slugs Boys!

Stoti

 

[2D1C]

Shooting slugs in .25 have been a journey!

Stoti saved a lot of us major money!. I think these liners may have improved. After Stoti's disappointment with the 700mm superior I Stayed a way from it. I bought a 600mm superior for my Crown, which went down, so I put it on my Impact. OMG!!!! I have the PP on it, 120bar, PL 3 will push the 29-5 NSA's @ 940ish sub MOA. I also shot a a couple of really rare 3/4" groups with the 34 gn KH MKII's these @ 900fps @100yds. So I bit the bullet and bought the 700mm superior liner (both have the CF sleeve) I am not sorry so far. It will shoot both MKI and II's equal, The 600mm liked only the II,s. It shoots the slugs good as well. But over all? The 600mm superior is more accurate. I have not tried the heaver slugs in either. 



Dennis

 

[knifemaker]

Well said Stoti! It is an interesting adventure! Luckily, most of it was figured out long ago by the PB fraternity.  For what ever reason, AirGunners in general seem to ignore what has already been learned in the PB world. Just look at the heinous shocks on some AG's and the far unneeded poorly balanced weight. When the AG companies do follow the pb trend, you get sleek well proportioned examples as the Daystate Hunter and FX Tarantula. Beautiful, light, handy! Sad it is so rare. 

2D1C, yep, in most cases a shorter barrel is stiffer, less whip and more accurate if the fps is there. and exactly why PB Bench Rest barrels are never "Long" but rather Short and Stiff. 



I'm lucky as the two test mules here can push my 36 gr slugs to almost 100 fps so I can test a wide range of projectiles. Light and heavy. the barrels I have here are .218, .223, .250, .257 and .172. I would like to obtain a .30 as well. Being disabled puts a restriction on my buying. GRRRRRRR!!!Knife/Mike



I have been using carbon tubes for years to wrap my barrels and most are virtually ultra light bull barrels just barley shy of the shrouds in dia. Glad Ernest learned the trick as it is very worth while. I sent him pic's of mine some time ago, but who knows?

 

[knifemaker]

Long-gun Dallas, Nope, fit perfectly.  You've seen both myself and HobbyMan2007 talk about them on the GTA. 



Knife

 

[Ghostranger169]

Apologies knifemaker, thank you for the information

 

[knifemaker]

My apologies , the Brownell's liners are 35 buck s + shipping. Oop's!

Knife

 

[stoti]

Thanks Curt, My bad, read the post wrong, glad I did!

Stoti

 

[AncientSword]

I think he’s referring to someone else, Stoti, at least that’s how I took it. Someone from SA.

 

[lamarkeiko]

Wow, I wasn't expecting my post to get such a wealth of knowledge in replies back. It seems that the general consensus is that the slugs need to have more velocity for increased accuracy. I looked back at my shooting records from last summer with my Crown set at 150 bar, and hammer max, I was getting just over 860fps with JSB MK II's and NSA 33.5's. Shot some NSA 36.2 at an ave. velocity of 832. At the time I wasn't really trying for accuracy, just seeing what velocity I could get. Shooting at 55 yds my JSB group was 13/16" c-c , the NSA 33.5's were 1" , and the 36.2 NSA was 3/4" c-c. Two days ago testing for accuracy of my NSA 33.5 and 36.2 at 135 bar with hammer settings from 4 to Max and sorted and cleaned slugs and shooting from 60 yd I was getting 5 shot groups between 1/2" and 1 1/4". Every one of the groups, I could pull out the worst shot and they would under 1" I had one group with the 33.5's going where the first 4 shots were all touching and I hated to shoot the last round, just knowing that shot would be a flyer. And it was. Caused that group to be 3/4". Would have been 1/4" without the last shot. I also shot a couple groups with the JSB MKII's with 3/4" and 5/8" c-c. How do these accuracy results sound with the slugs I'm shooting? How much more velocity increase could I expect from a 700mm barrel vs 600mm barrel?

I'm planning on using the NSA's on my ground squirrel population this year, because their accuracy should be plenty good for the squirrels at 60-70 yds.

From everything I've read above, I can't recall anyone stating their results shooting slugs in the Superior Heavy liner compared to the Superior liner. The Superior Heavy liner is 1:18 twist and Superior is 1:24 twist. Wouldn't a little faster spin on the slugs help accuracy. That's only a $109 investment.

Thanks for all the replies back

Lamar