250Z Message from Barra Airguns on Accuracy

[jps2486]

As an engineer, I appreciate Jake's technical explanation of the manufacturing process of the barrels, from material specs to production methods. Further, Barra's loyalty to customer support is a most important issue for me. I've dealt with the Chinese on aerospace products back in the 1980s and they were still trying to find their way at that point. They have come a long way, but we, as Americans, having our products made there must stay on top of the quality issue. That applies to any third party contractor.

 

[BBGunn]

Bingo! Unfortunately, I think you're right. I respect the hell out of AVS, and Roachcreek and Knifemaker, all slug pioneers or makers, but I don't think that there is a definitive formula either. We're all still testing every time.

For my 250z I never would have tried the .216 JSB KO slug if @Dairyboy hadn't told me that it shot lights out in one of his guns that usually shot .217. Turns out it shoots great in mine too.

The way things have been moving in the past 10 years, I'm not going to make any predictions, but I would not be surprised if someone came up with a guaranteed slug fit for a particular barrel, ...but I'm not holding my breath either.

Are you shooting the JSB .216" in the MK1 or the MK2 please?

 

[Pumacarl]

Are you shooting the JSB .216" in the MK1 or the MK2 please?

I have the original version of the Barra 250z in .22. The "Working On It" thread, here, has all the details of my gun, and what I did and how it went.

Edit: The bullet itself is not a Mk1 or a Mk2, it's an original I guess. 20.83gr .216

 

[PestPlasteringPlinker]

I am not a proponent of automatically matching slug diameter to groove diameter for slug shooting. In my limited experience (3yrs) (35yrs PCP) shooting slugs I have not always found best accuracy with groove diameter fitting/filling slugs.

I'm not saying that tight fitting slugs won't be the most accurate in a given rifle, but rather that those tight fitting slugs have just as much chance of NOT being the most accurate. Put another way, from my experience, looser (not loose) fitting slugs have just as good a chance of shooting well out of a given rifle as do tight fitting slugs.

I know that AVS says that groove filling diameters are the 'key' to good slug accuracy..., but I have not found that to be true. Don't get me wrong, I've spent hundreds of dollars on AVS slugs and usually find one or two that are at the top of accuracy results in a given rifle. However, those that produce the best have not been the groove filling diameters.

Not criticizing, just sharing to help folks trying to find good slug accuracy from the 250Z.

My dude, you could criticize me all you want, till youre blue in the face. I love it, because its people with experience sharing it. Its become second nature for some, to get upset about it. But I really don't think youre coming off as criticizing at all.

I totally get where youre coming from with looser, compared to tighter. My original barrel was rocking out at .2505-6. Shot the h&n dead accurate pretty good. Consistent fps, stacks. My Apollo, the .2500 ones, on paper, are 100% equally as accurate. I've just noticed myself, a bigger swing in consistency on the fps the smaller I go. I tried chasing the swing of the 2495's for an hour to get <+-5 fps. Couldn't get it. I got it with the 250's, pretty quick, and i squeaked out a swing of 2-+ on the 2505's consistently.

Now, once I reseal, and chuck the 2510's down the barrel, if I get equal accuracy, as the 2505's and the 250's thats going to be great. But I want the absolute lowest deviation I can get.

Im depending on one shot. One dispatch. I need to know, is this going to op, and ricochet into a cow, a horse, the window on that tractors cab over there?

I can't take the shot if I can't afford the aftermath. Its why I'll probably tinker for a few weekends on this slug and eat 2 tins before I figure out which slug is the most effectively consistent all around.

Do I really need to? No. Not at all. But I have no clue if the dude who picks it up from me is just going to launch pellets at popcans, or if they'll actually take it hunting. Or maybe sit on their balcony and take out the trash pandas raiding the community dumpster.

But, if I can say 'yep, its polished up perfect, here's the grouping you can expect at 70, using this size slug, at this speed, regulator set and stabilized here, adjust the h.s. for grouping.'

That to me, is worth it to see my coworkers have a better time plinking around.

But, like you and pumacari said, yall got better results with smaller diameters, so I won't completely write them off for testing.

I appreciate you giving me more to experiment with! (Ill never complain about shooting this thing, unless its 'shoot, im out of slugs!')

 

[Pumacarl]

My dude, you could criticize me all you want, till youre blue in the face. I love it, because its people with experience sharing it. Its become second nature for some, to get upset about it. But I really don't think youre coming off as criticizing at all.

I totally get where youre coming from with looser, compared to tighter. My original barrel was rocking out at .2505-6. Shot the h&n dead accurate pretty good. Consistent fps, stacks. My Apollo, the .2500 ones, on paper, are 100% equally as accurate. I've just noticed myself, a bigger swing in consistency on the fps the smaller I go. I tried chasing the swing of the 2495's for an hour to get <+-5 fps. Couldn't get it. I got it with the 250's, pretty quick, and i squeaked out a swing of 2-+ on the 2505's consistently.

Now, once I reseal, and chuck the 2510's down the barrel, if I get equal accuracy, as the 2505's and the 250's thats going to be great. But I want the absolute lowest deviation I can get.

Im depending on one shot. One dispatch. I need to know, is this going to op, and ricochet into a cow, a horse, the window on that tractors cab over there?

I can't take the shot if I can't afford the aftermath. Its why I'll probably tinker for a few weekends on this slug and eat 2 tins before I figure out which slug is the most effectively consistent all around.

Do I really need to? No. Not at all. But I have no clue if the dude who picks it up from me is just going to launch pellets at popcans, or if they'll actually take it hunting. Or maybe sit on their balcony and take out the trash pandas raiding the community dumpster.

But, if I can say 'yep, its polished up perfect, here's the grouping you can expect at 70, using this size slug, at this speed, regulator set and stabilized here, adjust the h.s. for grouping.'

That to me, is worth it to see my coworkers have a better time plinking around.

But, like you and pumacari said, yall got better results with smaller diameters, so I won't completely write them off for testing.

I appreciate you giving me more to experiment with! (Ill never complain about shooting this thing, unless its 'shoot, im out of slugs!')

To be clear, I didn't end up getting "better" results by just using a smaller diameter slug. This particular KO slug has an extremely thin base skirt that is obviously getting blown against the bore and sealing as tight as anything. All to say there is more than one way to skin a cat. The other slug my gun likes is a .217 Zan and its base is pretty solid comparitively. No way is wrong if you can get it to work. And we're all interested in what works.

 

[PestPlasteringPlinker]

To be clear, I didn't end up getting "better" results by just using a smaller diameter slug. This particular KO slug has an extremely thin base skirt that is obviously getting blown against the bore and sealing as tight as anything. All to say there is more than one way to skin a cat. The other slug my gun likes is a .217 Zan and its base is pretty solid comparitively. No way is wrong if you can get it to work. And we're all interested in what works.

! I didn't even think about how the skirt could make a difference.

Now I need to look into different style skirts too! That makes a lot of sense, considering soft metal, ballooning with a blast of high pressure, sealing to the bore.

I need to try and find cup, and dish slugs, different diameters, same grain. That would be killer to experiment with!

 

[BBGunn]

To be clear, I didn't end up getting "better" results by just using a smaller diameter slug. This particular KO slug has an extremely thin base skirt that is obviously getting blown against the bore and sealing as tight as anything. All to say there is more than one way to skin a cat. The other slug my gun likes is a .217 Zan and its base is pretty solid comparitively. No way is wrong if you can get it to work. And we're all interested in what works.

I'm going to start out trying AVS ELRs in .217". I'll try a couple weights and see what I learn???

 

[Pumacarl]

I'm going to start out trying AVS ELRs in .217". I'll try a couple weights and see what I learn???

I would be interested in reading your results. I have not seen any reviews with AVS slugs in the 250z yet. Good luck!

 

[Bladefin]

I am an idiot. I hadn't ever noticed the skirt on the MKII's. Don't know if it was coincidence but I noticed it yesterday and I'd already tossed the slugs I pushed and I've reassembled the guns.

 

[Cantona256]

To be clear, I didn't end up getting "better" results by just using a smaller diameter slug. This particular KO slug has an extremely thin base skirt that is obviously getting blown against the bore and sealing as tight as anything. All to say there is more than one way to skin a cat. The other slug my gun likes is a .217 Zan and its base is pretty solid comparitively. No way is wrong if you can get it to work. And we're all interested in what works.

I'm going to start out trying AVS ELRs in .217". I'll try a couple weights and see what I learn???

! I didn't even think about how the skirt could make a difference.

Now I need to look into different style skirts too! That makes a lot of sense, considering soft metal, ballooning with a blast of high pressure, sealing to the bore.

I need to try and find cup, and dish slugs, different diameters, same grain. That would be killer to experiment with!

So I wanna wade in on this haha. Having just slug tuned my 3rd barrel in the last year I consider myself a little bit of an expert here haha.

The truth is that you’re all right! I’ve had success with undersized, oversized and matching bore diameters.

Twist rate, barrel length and the base of the slug all have a huge effect on this. Slugs need spin. A stablized slug is an accurate slug.

On paper slightly oversized to create a proper seal is ideal. The reality is that most of the time that’s too much friction to get the speeds we want.

Oversized is good for shooting lighter slugs out of slower twist rate barrels. Like a 35gr out of one of those 1:24” twist rate fx barrels. They shoot the hybrids at 26gr well but not so much with heavier stuff. Being slightly oversized will help get max contact with bearing surface to impart spin. Longer barrel will also help.

Undersized works really well when your twist rate is faster. In my .306 bore diameter Lothar Barrel I’m finding it loves the 71gr hybrid boattails at .303… but this slug is .557” long and has long bearing surface. With a 1:15.96” rate and 28” barrel length it has enough spin right…. This is where playing with slug diameters can get complicated. The same slug knurled to .304 corkscrews, .305 knurled shoots beautifully at the same 890fps. But knurled up to .306 and not only does it shoot well but I’m getting about 7-10fps more speed.. or about 2-3 more for… so that tells me either .306 knurled is the way to go or I need to try .3065 and .307…knurling helps with oversized because it will collapse down if it needs to.

Now the old karma eq barrel was .303 and it shot .3025 and .303 slugs well. It also shot .306 knurled well but they were slower. The kicker was that it wouldn’t shoot the heavier slugs very well even though it has a 1:16” twist. Why? At 24” the barrel just wasn’t long enough to give the 71gr to get up to the right spin….. and that leads us to the type of rifling


You see the Lothar barrel has poly rifling and the karma barrel is traditional. Poly rifling is “smoother” deforms the slug less and will generally give you a mild fps boost… Fx rifling is an ever “smoother” version of this… despite what other people have said about mixed results with poly barrels for Airgun slugs I think it’s the way to go.

The karma barrel is shorter and due to the type of rifling it has more friction. So even though the twist was fast it wouldn’t stabilize anything heavier than 65gr.

Slug base matters because the right base will capture the air better. A good cup base slug will actually flare out the “cup” part like a pellet skirt to get a better seal. A flat base won’t.

The Karma has a radial transfer port so i have found it does slightly better with flat base slugs. But dish base works great too.


In short it’s complicated and there is no one right answer… I’ve transitioned heavily towards western coyote hunting. I need stopping power and BC… so for my tastes a barrel with poly rifling so I can shoot slightly undersized heavy for caliber slugs is ideal.

For the barra I think .250 slugs with a cup base is what I found worked best after trying .249 and .251

The truth the slug tuning is that it isn’t actually hard. People think it’s hard because it takes the time to try finding the right settings on the gun itself and then you have to find the right slug. Sometimes that can take a lot of money with ordering slugs. One of the reasons I have yet to buy a “fancy” gun is that I spend a lot of money on slugs. Lol @Pumacarl can tell you I get obsessive. Even when it’s “good” I want great. Took me 2-3 months with the barra and it took me 6 months with the EQ haha. Both of them were “good enough” way before I stopped searching. But both were new guns at the time and I wanted a definitive answer haha.

 

[Pumacarl]

Slugs: the agony and the ecstasy, for real! Lol

...meh, it's a hobby, it beats gardening

 

[pan60]

...meh, it's a hobby, it beats gardening

says who I love to garden : )

 

[Bladefin]

Slugs: the agony and the ecstasy, for real! Lol

...meh, it's a hobby, it beats gardening

Part of my shooting joy comes from picking off the vermin f'ing with my garden! The two go hand in hand

 

[PestPlasteringPlinker]

Slugs: the agony and the ecstasy, for real! Lol

...meh, it's a hobby, it beats gardening

Sir, a majority of my slugs catchers love nibbling on gardens.

 

[PestPlasteringPlinker]

Part of my shooting joy comes from picking off the vermin f'ing with my garden! The two go hand in hand

This, this is exactly right. Its so hard to beat looking outside, and getting the 'Oooooooooohhh! I gotta grab the air rifle!!' jitters!

 

[BBGunn]

Wonder who is making stainless barrels for the 250z?

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[Neu]

Wonder who is making stainless barrels for the 250z?

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Would get one in a heartbeat if I knew where

 

[cosmic]

Me also.. No info there.....

 

[Pumacarl]

Yeah, what the hell? He goes through all the trouble to make the video and never says where he got the barrel or if he's even selling them. I joined his channel and if he answers the question I'll let you all know. Very many people have been waiting for an aftermarket barrel, I'm glad it finally happened.

 

[PestPlasteringPlinker]

Yeah, what the hell? He goes through all the trouble to make the video and never says where he got the barrel or if he's even selling them. I joined his channel and if he answers the question I'll let you all know. Very many people have been waiting for an aftermarket barrel, I'm glad it finally happened.

Ditto. I just ordered a highly qc'd 250 for the old lady to do an unboxing, first shots side by with my modded. If its a botch job on this barrel, there will be 2 of those barrels sold immediately.