Update to my research on undersized slugs

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TrinityMaker

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Jan 30, 2020
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California, United States
So I had a good email correspondence with Nick from NSA ammo regarding undersized slugs, and perhaps consideration of swagging a slug in .221 since that's the groove diameter of the Lothar Walther barrels that 95% of gun manufacturers use. I explained the issue with air escaping around the grooves of the barrel when using an undersized slug, and how it can negatively impact accuracy as well as waste energy. He didn't seem to question that. But he did enlighten me on something I hadn't though about, and obviously he's done the research on.... It has to do 100% with choked barrels. 

So here's the deal. I guess even though the slug is smaller than the groove diameter at the breech, it chokes down to .218 near the muzzle. Nick said that choked LW barrels hate .220 and .221 slugs. But they seem to love .218. He said that the Daystate rifles love .217 slugs. Again, utilizing a choked barrel. 

He agreed that if you're using an un-choked barrel, that you should get better accuracy from a slug that concentrically seals in the grooves. If you have a un-choked LW barrel in .22, then the gun will like slugs in .221. If you have an un-choked LW barrel in .25, it will like slugs in .254. I'm not opposed to using a choked barrel. I'm opposed to the twist rates they typically use. The twist rates are great for pellets, but not for slugs. They create only marginal stability. Using the 35gr MP-Molds .22 slug, my gun with a LW barrel utilizing a twist of 1:17.7 is only marginally stable. But using my un-choked Russian Federation barrel with a 1:16 twist, the stability increases significantly. 

But Nick has a business to run. And I understand that the production of the slugs needs to justify the initial investment. And the demographic of air rifle shooters that are using un-choked .22 and .25 barrels is very small. So I don't think he's interested. And frankly, I can't blame him. So I think I'm going to go to Arsenal Molds and see if I can have a custom mold made from a slug I design. I want the slug to be .221 and weigh 30-32gr. I want it to have drive bands that minimize friction. I've already drawn something up. I'll see if Jared at Arsenal will be willing to make it for me. I already have the MP-Molds .22 slug that fits very nicely in my barrel. But I think I can come up with a design that's more stable. 

So I suppose this is the question- the dilemma. Is it worth converting you rifle to slugs and getting a custom barrel, but potentially not being able to achieve your goal of maximum stability and accuracy by using the mass produced slugs available that are designed for choked barrels? Is it worth the cost to purchase a mold to cast your own slugs in the proper size, or have a custom mold made to fit your barrel? Especially in a small caliber. But if you can design a proper slug, it can potentially be game changing! 

Thoughts?
 
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I have my thoughts , and here they are I own many slug guns and probably 50 to 60 molds , and I also have spare barrels , If I have a super accurate gun I tailor my ammo to it ,

example if it is unchoked barrel say and it is .300 then I will want a swagged or casted slug .3005 . for best accuracy if this is my bore , and I may modify a few molds to make an exact cast or swag ammo where it needs NO sizing , so I thrive to get a die or mold exact ,



Now I have a few slugs in .22 250 and 257 and I have some guns I just like so yes I also will buy rifle blanks to tailor to my ammo , so my answer is I do both and found this best .I have not found accuracy I can get from a store bought slug , I mean some are shoot-able but for say ,hunting coyotes with my 22 and 30 cal , My ammo is king for me ,as I like solid heavier slugs bettor for this ,



It is like anything else you need to start with a good design slug proven by you to move forward or a gun and power to shoot a certain slug then match it that way , I have casted and swaged now for decades and I love about 6 molds I own out of geeze a hundred , so for me to love it , I go threw alot , I wont waste time on poor quality barrels or poorly designed slugs .


 
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That's what some people like me are waiting for - match grade barrels with the optimal twist rate, groove and land dimensions, matching slugs with characteristics designed for such barrels, and high BC, all for PCP air rifles and the velocities they work at.

Like you've mentioned already, most airgun barrels don't have the proper twist rates for slugs, an on top of that it's often a goose chase finding the correct combo of all.

Heck I'm a house painter by trade and I don't want to go down that road of powder coating slugs so I want a turn key system concerning that too.

Also I want the slug to fit the chamber and the pellet probe to be made slug specific so I'm not cramming the slug in the chamber with a lot of pressure.

I'm looking for sub moa and low ES or I'll stay with my rimfires and centerfires, and shoot my AG's with pellets.

In other words "everything has got to be sorted out" 






 
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let me first say i over my skies here but wouldn't it be easier to resize a slug to the size you what then case your own 

and is there anything here that might help 

http://www.corbins.com/pellets.htm

resizing will work on some ag slug designs, but not on others because when you push them through the die you’ll shave the larger power band that makes the seal at the base of the slug. For instance, this slug design by Gregor Kamenšek and mp molds for the huben. I mean you could get a shootable product but it would just ride the lands

1583037923_6564708525e5b3de3032e79.92688955_CE28CBCC-A0BE-4AE6-81BC-83FAC8AA32C7.jpeg
Click to expand...


 
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Nation, 

This exact problem, is the issue that I had with my first set of Corbin dies. 

I initially contacted Dave Corbin, and told him I wanted dies in 4.52, and 4.53, in his semiwadcutter design. I recieved them, and made a bunch of slugs with a 3/4modified Keith nose. It turned out that no airgun I owned would shoot them. They shot them, but with zero accuracy. The best I could do with any gun I owned, was a 30 yard group of 6-8 inches, which is totally unacceptable. 

Fast forward a few years. I again contacted Dave Corbin, and this time, did things a little different, upon his guidance and recommendation. He instructed me to shoot a few pellets out of my 2 most accurate airguns, my Steyr LG 110 FT, and my Rapid Air Weapons TM 1000. I recovered the shot pellets, and sent them to him. Instead of me telling him what size I wanted, he would tell ME what size I NEEDED. This was the best decision I could have made.

Onward to this day. These dies have proven themselves in a lot of guns I own, particularly the Crosman 1720T. I've never seen anything so accurate. As far as the Steyr and the Rapid are concerned, it shows good promise. The accuracy is there, but some more work needs to be done, as the weight, nose design, and base shape needs to be adjusted to my rigs. All of my guns are for WFTF 12 ft.lb limits.

The quest continues, I should have more data in the upcoming weeks. 

Tom Holland 

Field Target Tech 
 
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I thought about contacting Nick about the same thing. Raptors using TJ barrels may change his way of thinking. My TJ barreled guns don't shoot any of his .25's because they are too small. Personally I think its simple to just offer a .254 and let the committed slug shooters size them down until the barrel is happy. But from a business standpoint I know every Tom, Dick and Harry wanting to jump on the slug bandwagon has a choked barreled pellet gun and a credit card full of hope. As slug guns like the Raptor become more mainstream, he is going to have to make a properly sized slug. I know all my .25's are bought from another source.
 
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Stephen at AVS SLUGS swages .254 slugs. They are 2S ogive and he has them in various weights. I suggest trying them in your Raptor. 

However, the Raptor in .25 utilizes a 1:20 twist rate. That is per Travis at JS air rifles. It doesn't utilize the 1:14 acp twist that most people identify with a .25 TJ's barrel liner. 

Also, try the 48gr slugs from MP-Molds. They are rebated boat tails with drive bands. They have a great design to them. 

But personally, i think the .25 barrel that the Raptor uses has too slow of a twist for slugs. It's great for pellets. But Travis swears it's ideal for both. Unfortunately when you try to find a happy medium (i.e. a barrel with a twist that is good for both pellets and slugs) one of those two options will suffer. I'm pretty sure it's the slugs. And if the barrel shoots slugs and pellets, is it choked? Because i heard pellets LOVE a choke, and don't shoot well with un-choked barrels. 

Maybe someone who owns the JSAR Raptor in .25 could enlighten us on barrel characteristics. 

BTW- I designed a slug in .221 caliber this weekend. It has 2 drive bands that combined with the nose would create 3 points of contact in the barrel. The depth of the slug in-between the drive bands in .218". These slugs would be specifically designed for un-choked .22 LW barrels and other rifled barrel manufacturers. I'm thinking they should come in at between 31 and 33 grain. If they shoot good, I'll ship the mold off to have it fitted with a hollow point pin in one or two of the cavities. That should drop the weight by 1 to 1.5gr. 

I'm going to submit it to Jared at Arsenal Molds and see if it's something he can make for me. 
 
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I have been using the 1:22 TJ for a couple years on one gun and recently put one on another. In .25 they do just fine with JSB pellets and don’t have a choke. The one gun will shoot a .250 slug but I have to slow it down to 750fps. I have a theory. I have read plenty of times about having to really speed up slugs to get them to shoot. Maybe guys are having to hit the back of a cup or dish base slug super hard with air to get it to blow out and seal because their slugs are too small for the initial part of their choked barrels. The TJ .25 ACP is old school and was used when there were no options for a .25 slug shooter.
 
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TrinityMaker - "But personally, i think the .25 barrel that the Raptor uses has too slow of a twist for slugs". - Don't take this the wrong way. But that's a problem to me.

Because I know for fact that a 1-22" twist TJ's .25 cal. .250" barrel in a modified gun works with slugs up to 38gr. @ 940 FPS and pellets @ 900 - 950 FPS (25.4gr. only pellet to fit my leade.) It works just like Micheal Hossach was trying to tell the Yellow forum members about back in 2014. A 1-22" can shoot both. For those of you who still shoot pellets and would like to try slugs, I would consider a 1-22" barrel for .25 cal. possibly the best choice. I know the 38gr. slugs do fly true to 400 yards confirmed. A heavier slug may not be able to stabilize properly, but I don't know that without having verified it first. 

I do know that barrel didn't like a .2495" diameter slug I made for it at all. That doesn't mean it won't possibly shoot a different cup type base accurately though. 

I have been using the 1:22 TJ for a couple years on one gun and recently put one on another. In .25 they do just fine with JSB pellets and don’t have a choke. The one gun will shoot a .250 slug but I have to slow it down to 750fps. I have a theory. I have read plenty of times about having to really speed up slugs to get them to shoot. Maybe guys are having to hit the back of a cup or dish base slug super hard with air to get it to blow out and seal because their slugs are too small for the initial part of their choked barrels. The TJ .25 ACP is old school and was used when there were no options for a .25 slug shooter.
Click to expand...

That's about my thought also. You have to pick the slug weight, diameter, OAL etc. before you even think about cutting your barrel.....................at least that's what I did. 

As Lou pointed out above making your own ammo. is KING. He's shared a lot of good info. about some the slugs he has been making. 
 
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Long_Shot, I don't take your feedback the wrong way at ALL. I humbly admit that I'm not an engineer, scientist, or physicist. I'm not an expert in this matter. It's my understanding that a faster twist (in moderation of course) improves stability on slugs. This is very evident when shooting a .22 air rifle. The 1:16 twist has been proven to be more stable than the 1:17.7 twist from LW when shooting slugs. Would a 1:15 or 1:14 twist be even more stable than the 1:16? I don't know. There are several people that are shooting a 1:14 barrel. Bob Stern has one, and he gets incredible accuracy from it. He sent me pictures of some of his groups using his NOE boat tail design. The groups were impressive.

Is there anyone who posts on this forum that's using one of the older .25 ACP barrels with a 1:14 twist? I realize the barrel is a firearm barrel, not an air rifle barrel. But slugs aren't pellets, and I think they would lend towards better performance from barrels designed for firearms. Barrels with faster twists and no chokes. But I also think everything has a resonant frequency. This was Nikola Tesla's theory regarding mechanical engineering and structural integrity. Everything has a "resonant frequency". A frequency at which the harmonics created cause subtle vibrations in a structure, and if left on for too long, the building could topple. It's a magic combination of frequency and placement of the device where a very small force properly placed and exerted could yield a MASSIVE result..

I feel that every air rifle shares this concept- except it lends to it's performance, not it's destruction. It's a magic combination of power, twist, and projectile. It isn't easy to find, but it isn't impossible to find either. But if you do find it, don't hoard the info for yourself. Share it with your brothers and sisters in the airgun world. We all long to know the magic combo to achieve long range greatness.

This I can tell you.... If I find the magic combo for my air rifle, I will share everything I to achieve it. Not everyone owns the same type of rifle I do, but if I can help the people that do, then I will. Just my $.02










 
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Long_Shot, I don't take your feedback the wrong way at ALL. I humbly admit that I'm not an engineer, scientist, or physicist. I'm not an expert in this matter. It's my understanding that a faster twist (in moderation of course) improves stability on slugs. This is very evident when shooting a .22 air rifle. The 1:16 twist has been proven to be more stable than the 1:17.7 twist from LW when shooting slugs. Would a 1:15 or 1:14 twist be even more stable than the 1:16? I don't know. There are several people that are shooting a 1:14 barrel. Bob Stern has one, and he gets incredible accuracy from it. He sent me pictures of some of his groups using his NOE boat tail design. The groups were impressive.

Is there anyone who posts on this forum that's using one of the older .25 ACP barrels with a 1:14 twist? I realize the barrel is a firearm barrel, not an air rifle barrel. But slugs aren't pellets, and I think they would lend towards better performance from barrels designed for firearms. Barrels with faster twists and no chokes. But I also think everything has a resonant frequency. This was Nikola Tesla's theory regarding mechanical engineering and structural integrity. Everything has a "resonant frequency". A frequency at which the harmonics created cause subtle vibrations in a structure, and if left on for too long, the building could topple. It's a magic combination of frequency and placement of the device where a very small force properly placed and exerted could yield a MASSIVE result..

I feel that every air rifle shares this concept- except it lends to it's performance, not it's destruction. It's a magic combination of power, twist, and projectile. It isn't easy to find, but it isn't impossible to find either. But if you do find it, don't hoard the info for yourself. Share it with your brothers and sisters in the airgun world. We all long to know the magic combo to achieve long range greatness.

This I can tell you.... If I find the magic combo for my air rifle, I will share everything I to achieve it. Not everyone owns the same type of rifle I do, but if I can help the people that do, then I will. Just my $.02
Click to expand...

A 1-20" or 1-22" twist for .25 might work, but a faster twist rate could be a more stable slug barrel choice. So basically the reduced barrel harmonics in a fast twist could help in the slugs stability from breach to POI. That makes sense.

I was wanting a new 28" barrel anyway. No point in having all my barrels the same twist rate. I'll be looking into this more before I order the barrel. 
 
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I also believe shooting a bullet is shooting a bullet. That’s why my slug guns don’t have chokes. But the X factor is how a firearm drives its bullet and how fast compared to an airgun. When you squeeze the trigger on a firearm, the force exerted on the projectile is fast and hot creating an instant seal with the rifling. That’s why they use copper and have to use a gas check with lead. Dwell in an airgun is the same as the burn rate of the powder you use in a firearm. But they are not even comparable in speed. Everything in a firearm happens so fast compared to an airgun. The fastest .25cal airgun is embarrassing in the firearm world. Consider that when we try to use crossover information.
 
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I agree 100% about the comparison to air rifles and firearms. Matt Dubber did a GREAT job talking about how velocity effects accuracy. With firearms, it's rare to keep the projectile subsonic. And the projectile is typically accurate in the supersonic range until it's velocity drops into the transonic range. Then it goes to crap! But an air rifle strives to stay subsonic in velocity. The supersonic and subsonic range have proven to be the most stable. If you push an air rifle slug to 1100fps, the POI and accuracy will be garbage, even at close range. But especially at long range. But if you start it right on the edge of the transonic/subsonic range (say 950 fps) the projectile can stay stable throughout it's flight. 

I also agree about using un-choked barrels for slugs. I don't think the choke necessarily helps regarding performance. The effects aren't devastating, but they don't help either. 
 
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A choke is not the end of the world when it comes to bullets putt putting along at subsonic speeds. I have owned a couple .22lr rifles that had choked barrels. I think one was a CZ. But like we discussed in the powder coating topic, The choked 22lr creates an instant seal when the fire hits the lead. So they aren't dealing with air/gasses ahead of the bullet. Unfortunately bulk slug suppliers have to cater to the choked pellet gun because that's what almost everybody has. I was able to get off three shots at the bottom of a can yesterday at 113yrds with my slug barreled Priest. Shooting 34gr .254's, sized, silicone lubed and going 905fps. Looked good through my scope but the rains came. I will walk down and snap a pic and measure this morning. I think I might be good to go. I will test 32gr next and see what I want to commit to.
 
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