Early Impact .22 slug liner report

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13brv3

13brv3

Member
Feb 1, 2017
373
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TN, United States
Greetings,

I wish I had a glowing report of success, but I don't think that's the case, at least not yet. Patients is often required with these things, and I know how long it took to get good results with pellets, so I'm remaining optimistic that I'll get this sorted out. 

This is a 600mm slug liner installed in a pre-X Impact. The regulator is at 150 bar, and the power wheel was at 5 (historically better than MAX for me). The valve is full power. 

When I installed the slug liner, I noticed it had 2 o-rings and not 3 like the original pellet liner had. They were already aligned as you'd place them if you were counting on the physical mounts at the ends of the liner, so I installed it that way. Unfortunately, I'm not confident that the o-rings stayed where I want them, since you just kinda have to hope for the best after trying to get them past the threads. I did clean the liner before shooting it.

Here are the notes from the 3 slugs I tried FWIW. Always keep in mind that I'm not that good of a shooter, so you're results can always be expected to be better :) The 27 gr was the best of the day, which was a surprise for me. I really want the 28 gr boat tails to be the best. 

Rusty

- 27 gr Nielsen slugs. These work fine in the standard mags. I zeroed these at 50 yds, then determined that they drop 3 mil at 100 yards. Shooting for a single group of 5, I got 1-3/8".

- 28 gr Nielsen boat tail slugs. These do not fit in the magazine, and have to be single loaded. I verified they were zeroed at 50 yds, and determined that they required a 3 mil holdover at 100 yds. Shooting for a single group of 5, I got 2-3/8"

- 21 gr Nielsen slugs. These fit easily in the magazine, but they hang up when the mag tries to turn, so they don't work. I had to single load these. I re-zeroed at 50 yards, and noticed that they seem unstable. They would hit left and right for no known reason. Shooting 100 yards only required a 2 mil holdover due to the higher speed. Shooting for a single group of 5, I got 3-5/8" (more left and right than up and down).
 
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13br3 try without re-zeroing to 50yards again and again, this would be the only fair comparison. Otherwise the drop measurement results are not representative and loopyness of the trajectory is warped, twisted.

just shoot aiming at the same point of aim, without touching the scope. then compare! Also you could place 2chronies (if available) at the same time after you established the POI and then compare the ratios of fpss between final velocity and muzzle velocity for a certain slug, this is to find outhow they retained speed relative to the muzzle velocity.

Additionally you could do the BC calculation based on the drop. That’s based on only poa and poi difference vertically When measuread at different distances.
 
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Thanks for posting. Hard to tell with one 5 shot group for each, but not bad for the 27 and 28gr IMHO. I think the velocity is a huge factor. Did you manage to measure fps?
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When the reg was at 141 bar, the 21gr was 934, 27gr was 845, and 28grBT was 844. Raising the reg to 150 probably added a few fps but I haven't measured it yet. I plan to get some other weights, and will chrono them again.

Rusty


 
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You should try the 23gr. I'm shooting out of a standard mrod barrel so totally different but I tried the 21gr, 23gr, 27gr, and 28gr and at 50yds the only one that did good was the 23gr for me. 21gr and 27gr were around 1.25" and 28gr was over 2". However the 23gr we're under 3/4".
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That's interesting. I was thinking of skipping the 23gr, but maybe it's worth a try. I need to ask Nielsen's if they'll put together a sample pack, with some of each pellet weight for initial testing. 

Rusty


 
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As for testing BC and drop, I'd really like to set up two chronos, and I do have two, but hauling all that stuff out to the forest where I shoot isn't much fun. I'm sure someone with a better setup will try it before I get around to it. 

For the drop test, maybe I should zero the rifle once at close range, like 10 yds, then measure drop at 100 yds. Between work, wind, and rain, I doubt I'll get to do any more testing for at least a week and maybe longer. 

Rusty


 
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What I have noticed is that they are the exact same twist rate as the liner that came with my Impact "X" I haven't ordered any neilsen slugs yet. I'm going to try the Piledrivers that I have sitting on the shelf.

Maybe Matt can chime in and give some advice on this? Since he's been doing a lot of testing with these liners??

Click to expand...


I meant to check the twist rate when I was swapping the liners, and now you're going to make me pull it back out to check :) I wanted to revisit the o-ring placement anyway. I could swear I read that the slug liner had a faster twist rate. If all they did was eliminate the choke (if they did), that's kind of disappointing. 

Rusty


 
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This just in :) I exchanged a few emails with Nick, and he turned on the sample pack and custom weight options. The sample pack has a number of pre-configured options, but he said you can add in the notes of the order which 4 weights you want included. They DO have to be standard weights they normally sell, not custom weights. This is really nice. 

https://nielsenspecialtyammo.com/collections/22-caliber/products/sample-pack-217-caliber-air-gun-slug-swaged

Cheers,

Rusty


 
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What I have noticed is that they are the exact same twist rate as the liner that came with my Impact "X" I haven't ordered any neilsen slugs yet. I'm going to try the Piledrivers that I have sitting on the shelf.

Maybe Matt can chime in and give some advice on this? Since he's been doing a lot of testing with these liners??

Click to expand...


I meant to check the twist rate when I was swapping the liners, and now you're going to make me pull it back out to check :) I wanted to revisit the o-ring placement anyway. I could swear I read that the slug liner had a faster twist rate. If all they did was eliminate the choke (if they did), that's kind of disappointing. 

Rusty

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When I compared the slug liner to the one that came in the "X" the rifling seemed faint. Not as pronounced as the stock "X" liner. 
I'm hoping that the slug liner can shoot regular JSB 18.1 gr pellets so I don't need to swap it back and forth?

Have you tried to see how the slug liner groups the 18.1 gr JSB's?




 
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I shot about a dozen 18gr tonight just before dark, and they did great, but it was only 30 yards. It will be interesting to eventually test them back to back with my old ST barrel at longer distances. Of course I could also swap the liners, but that's a fair amount of hassle, and if I were trying to do that outside, I'd lose half the o-rings probably. 

The choke would have seemed more important in the old ST barrel, since you might need to force the pellet against the short section of rifling at the end of the barrel. Now that the rifling is full length, I wonder how useful the choke is?

Rusty


 
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I shot about a dozen 18gr tonight just before dark, and they did great, but it was only 30 yards. It will be interesting to eventually test them back to back with my old ST barrel at longer distances. Of course I could also swap the liners, but that's a fair amount of hassle, and if I were trying to do that outside, I'd lose half the o-rings probably. 

The choke would have seemed more important in the old ST barrel, since you might need to force the pellet against the short section of rifling at the end of the barrel. Now that the rifling is full length, I wonder how useful the choke is?

Rusty

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Glad to hear that the slug liner still shoot well with regular pellets. By the way both barrels are 1 in 20 twist rate, other than the choke they appear to be the same. I wonder if your accuracy issue has to do with FPS? 
I know Matt talked about slug being pick on FPS.
 
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I measured my pellet and slug barrels at 1 in 19 twist. I'm still quite surprised it's the same for pellets and slugs.

Out of curiosity, I did some searching for .22 cal rimfire rifle twist rates. It seems 1 in 16 is a very common twist, even for subsonic rounds. As I understand it, the general rule is that heavier bullets require faster twist rates. If 1 in 16 is good for a 40gr rimfire bullet, maybe the slower 1 in 19 is right for our generally lighter bullets (why do we call them slugs?). I have to believe FX knows what they're doing, but it would be nice to see some of the testing for various twist rates that I'm sure they've done. 

Cheers,

Rusty


 
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I measured my pellet and slug barrels at 1 in 19 twist. I'm still quite surprised it's the same for pellets and slugs.

Out of curiosity, I did some searching for .22 cal rimfire rifle twist rates. It seems 1 in 16 is a very common twist, even for subsonic rounds. As I understand it, the general rule is that heavier bullets require faster twist rates. If 1 in 16 is good for a 40gr rimfire bullet, maybe the slower 1 in 19 is right for our generally lighter bullets (why do we call them slugs?). I have to believe FX knows what they're doing, but it would be nice to see some of the testing for various twist rates that I'm sure they've done. 

Cheers,

Rusty

You are almost right. It isn't the weight of the projectile that determines the best spin rate, it is the cross sectional density or effectively, the length. The longer the projectile the greater the spin rate must be to stabilize it in flight. Under spinning will cause wobble and tumble. Over spinning prevents the projectile from pitching over at the apogee of its flight path. Like overspinning a football during a pass. This causes a differential of air pressure between the bottom and top of the projectile in flight allowing it to skip like a flat stone on water when the projectile encounters pockets of denser air (colder) during its flight.
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