Im now starting to experiment with .25 slugs out of my M3. NSA is my starting point. Why do they mfg. them with flat backs or dished backs?
NSA slugs, why the flat or dished (concave) back side?
- Thread starter beercanshot
- Start date
Judging from what I have read, here and there, the dish allows better placement of the slug in the chamber. It is thought that the dish also helps to seal the slug to the barrel as well.
While I really don't know about either of these suppositions at this time.
I have have shot both the dish base 36gr NSA Dimple Nose slug and the flat base 33.5, 36.2, 38.5gr slugs at under MOA at 100 yards with my .25 Impact 700mm Slug A liner.
So, it does not seem like it makes much of a difference in this scenario.
While I really don't know about either of these suppositions at this time.
I have have shot both the dish base 36gr NSA Dimple Nose slug and the flat base 33.5, 36.2, 38.5gr slugs at under MOA at 100 yards with my .25 Impact 700mm Slug A liner.
So, it does not seem like it makes much of a difference in this scenario.
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rodjava
Member
For what's it worth. I tried every NSA slug starting from 33.5 grains to 55.5 grains. And every grain in dished, cupped and flat. I only shoot long distances of 200 yards and the 43.5 flat bottom slugs worked the best at 950 fps. I shoot a FX Impact M3 .25 cal with Superior heavy liner and slug kit.
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It's still fairly "early days" for slugs and there has been little in the way of consensus-building or setting of standard expectations for manufacturing. So slug manufacturers are making a lot of variety, to see what sells, i.e. to have the market build some consensus.
Do these little changes make any difference? Hard to say.
Do these little changes make any difference? Hard to say.
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Some people swear by dish and others by flat base. When we do testing the results are similar. How we normally determine which to use is which one edges out the other either in accuracy or accuracy across a larger number of platforms.
Most slugs it is very close. Others it will make wild changes to the accuracy. We also do it meet the demands of consumers who are requesting what they believe shoots better in their gun.
Most slugs it is very close. Others it will make wild changes to the accuracy. We also do it meet the demands of consumers who are requesting what they believe shoots better in their gun.
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@nielsenammo Thanks for chiming in. I was waiting for that. I’ve wondered this same thing for a while myself. Thank you @beercanshot for posing the question.
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Mr. Nielson hit it on the head.
After tinkering with my .1775 slugs in all configurations of nose shape, and base shape options, I've found this......
All projectiles I've created, have the best performance from a 2S hollowpoint nose.
Cup base and flat base usually perform equally, but in some gun barrels, one has a little bit more accuracy than the other.
I tested 15 grain, 2S hollowpoint nose slugs with a hollow base @30 yds. @ 12ftlb. Could not get a group smaller than 8 inches. Change ONLY the base to a cup base, leaving everything else the same, groups went to the size of a dime.
Base shape has more to do with accuracy than what a lot of shooters think.
Tom Holland
Field Target Tech
Fieldtargettech.com
After tinkering with my .1775 slugs in all configurations of nose shape, and base shape options, I've found this......
All projectiles I've created, have the best performance from a 2S hollowpoint nose.
Cup base and flat base usually perform equally, but in some gun barrels, one has a little bit more accuracy than the other.
I tested 15 grain, 2S hollowpoint nose slugs with a hollow base @30 yds. @ 12ftlb. Could not get a group smaller than 8 inches. Change ONLY the base to a cup base, leaving everything else the same, groups went to the size of a dime.
Base shape has more to do with accuracy than what a lot of shooters think.
Tom Holland
Field Target Tech
Fieldtargettech.com
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My cricket compacts like flat base slugs... the uragans at least 177 - 22 - 25 like cup base by a great margin.
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I know it has to due with weight and CG, but I also wonder if the dished back doesn't help gather the air charge to push it forward. The Benjamin Nosler 357 rounds have a slight dish base, Nosler wouldn't have done this if there wasn't something to be gained. Of note the new Benjamin ammo for the Bulldog 357 and 457 is flat base and nothing special, but it least they reduced the price to $0.50 per shot so that's something.
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If a barrel has enough twist rate for the slugs then there will be no difference at all but due to most airgun barrels have very slow twist rate the center of gravity and length of the slugs becomes quite important to get minimum stability or accuracy. Dish based slugs have CG slightly forward but slightly longer, I found flat base or the shortest version tend to shoot slightly better because the stability is slightly batter.
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When your trying to get lighter weight slugs for example in .22 getting down around 17-18 grain having a dish base means you can keep a bit more bearing surface on the slug. It’s longer but lighter than a flat base.
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I see a lot of debate about base preference and I think each individual barrel will like it’s own style shape weight etc. I have a Vulcan 3 by AGT and the best connection there is: 54.5 grainers NSA dish base .30 cal. This nets me easy sub Moa groups at 100 150 was also. Minus the 3 that were completely my fault outside of the group of 6 sots I messed up with my poa not poi. I bought a rear rest recently as I’ve been so used to monopods I had no rests to speak of. Bought a Caldwell x mini. Was like shooting off a rock with nipples. No conformity. So actually need some advice on a good high quality rear rest. But I personally believe dish and cup base seal better in airgun barrels because there’s not the same amount of pressure that a firearm produces to expand a flat base in my opinion. I’ve yet to have success with them. The Vulcan 3 is a .306 and shoots .300 ammo fine as long as it’s got a dish base. Nothing compares to those NSA 54.5s @ 955 fps. Any advice on a bag would be appreciated. 
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Also I read that someone said that shorter slugs were more accurate… I’m pretty sure that’s the opposite of the case. The longer slugs change the sectional density and makes the flight path more stable with more bearing surface but no wider diameter. Like how the patriot javelins in 40 grain .22 have the same bc as a heavier .30 does which is usually never the case. But that long ojive style is more stable and is usually shot at higher speeds than the .30. Anyone agree?
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Length of ammo will in some ways depend on the spin rate of the barrel, I think longer needs more spin (could be opposite).
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I think the different base styles is to change the balance of the slug. My theory is that Long hollow bases move the CoG forward and will have a tendency to naturally fly straight. Just like a foster slug for a shotgun.
when you start filling the base, it moves the CoG backwards and it takes faster rifling to be able to stabilize these slugs since they will lose that ability to self stabilize and instead will want to swap ends.
Many air rifle barrels were designed to shoot traditional diabolo shaped pellets that are nose heavy and only need twist to stabilize it as it leaves the barrel. Thus, they don’t have enough twist to stabilize flat base slugs.
That’s my theory at least.
when you start filling the base, it moves the CoG backwards and it takes faster rifling to be able to stabilize these slugs since they will lose that ability to self stabilize and instead will want to swap ends.
Many air rifle barrels were designed to shoot traditional diabolo shaped pellets that are nose heavy and only need twist to stabilize it as it leaves the barrel. Thus, they don’t have enough twist to stabilize flat base slugs.
That’s my theory at least.
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OC,
As I mentioned above, any design slug that I have experimented with (over the last 3 years, hundreds), no matter nose shape, weight, or length, none of them would even remotely group with a hollow base, like a regular pellet. It's gotten to the point where I won't even waste my time with the hollow base punch. Tried everything possible, hollow base with slugs are basically useless.
Tom Holland
Field Target Tech
Fieldtargettech.com
As I mentioned above, any design slug that I have experimented with (over the last 3 years, hundreds), no matter nose shape, weight, or length, none of them would even remotely group with a hollow base, like a regular pellet. It's gotten to the point where I won't even waste my time with the hollow base punch. Tried everything possible, hollow base with slugs are basically useless.
Tom Holland
Field Target Tech
Fieldtargettech.com
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Tom --=--
Understanding that the FX Hybrids are not made in 177 (I don't think), the .22 caliber that I have shot, actually have darn good accuracy, yet have a slight hollow base similar to the JSB 25.39 pellets. Not saying that you're wrong, just pointing out that at least those hollow base slugs do have good accuracy at least in my experience.
mike
Understanding that the FX Hybrids are not made in 177 (I don't think), the .22 caliber that I have shot, actually have darn good accuracy, yet have a slight hollow base similar to the JSB 25.39 pellets. Not saying that you're wrong, just pointing out that at least those hollow base slugs do have good accuracy at least in my experience.
mike
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What rifle are you using to test these? Do you have the barrel specs? Did you slug the barrel?
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OC,
I don't have the actual barrel specs, but they were shot out of a RAW TM1000 with a stock Lothar Walther barrel.
I shot several dozen pellets, and some production made slugs, and recovered them perfectly intact, with zero deformation. I sent them to Dave Corbin, he measured them under a powerful microscope he has for this purpose. After looking at the pellets and slugs, he determined that the die diameter for this barrel (as well as my Steyr LG 110 FT) to be .1775. This diameter is slightly smaller than NSA's. Dave Corbin is the authority on this subject, he makes most of the dies of the larger volume slug manufacturers. I've also tried all kinds of hollow base slugs in many different high end guns, such as a Thomas FT, Air Arms EV2 Mark 4, and my custom Benjamin Marauder set up for FT. I have also tried them using choked and unchoked 1:17,7 barrels, as well as choked and unchoked Poly barrels. Tried 1:16 and 1:20 twists as well. Also, keep in mind, I'm trying to get these to work in sub 12ftlb guns, that could play a factor in the equation as well, as traditionally, slugs out of airguns in general, will fly better at higher velocities.
Tom Holland
Field Target Tech
Fieldtargettech.com
I don't have the actual barrel specs, but they were shot out of a RAW TM1000 with a stock Lothar Walther barrel.
I shot several dozen pellets, and some production made slugs, and recovered them perfectly intact, with zero deformation. I sent them to Dave Corbin, he measured them under a powerful microscope he has for this purpose. After looking at the pellets and slugs, he determined that the die diameter for this barrel (as well as my Steyr LG 110 FT) to be .1775. This diameter is slightly smaller than NSA's. Dave Corbin is the authority on this subject, he makes most of the dies of the larger volume slug manufacturers. I've also tried all kinds of hollow base slugs in many different high end guns, such as a Thomas FT, Air Arms EV2 Mark 4, and my custom Benjamin Marauder set up for FT. I have also tried them using choked and unchoked 1:17,7 barrels, as well as choked and unchoked Poly barrels. Tried 1:16 and 1:20 twists as well. Also, keep in mind, I'm trying to get these to work in sub 12ftlb guns, that could play a factor in the equation as well, as traditionally, slugs out of airguns in general, will fly better at higher velocities.
Tom Holland
Field Target Tech
Fieldtargettech.com
Upvote 0