250Z Barra 250z Slug Tuning

[Billm]

Those are really , really good results for a sub 500 dollar rifle, I see a lot of people purchasing these rifles to shoot slugs, has anyone shot just good old say, 33.95 jsb out of them and posted some results?

Actually I was just looking through my pellet/slug purchases. I bought one tin of JSB .22 33.956 Jumbo Beast pellets. But, I don’t remember how they did group wise. Looks like I only shot 15 pellets. These stats would have been with the box stock factory set 250z. I will try to shoot a couple of groups with the higher settings that I am using now. I’ve sure gotten wrapped around the axle with this rifle lol.

 

[Pumacarl]

Just about nothing in airgundom has shot the .22 33.95gr well so it would be a hoot if the 250z did!

 

[CTAirgunner]

Just about nothing in airgundom has shot the .22 33.95gr well so it would be a hoot if the 250z did!

I was about to say the same, those have to be the worst pellet out there honestly.

 

[Billm]

Well at 6:30am I saw zero wind. Unfortunately I had the 250z apart as I was adding a power wheel to it so that I can adjust the hammer externally. I slapped it back together and filled it. I loaded two mags with the 33.95. I backed the hammer spring out. By now I had a 5mph wind out of the SE. I shoot west to east. First shot was about 3ft to the left and 3ft low. The reg set at 2600psi it started at 813fps. I brought it up to 890fps with the hammer spring. It was 880fos by shot 20 and was at 2600psi in the tube. I could not put more than 5 pellets out of 18 on the 18” x 24” (HxW). backer board. I’m far from a ballistic expert, but I’m guessing: spiraling. I have no idea what the optimum velocity for these pellets is.

 

[CTAirgunner]

Well at 6:30am I saw zero wind. Unfortunately I had the 250z apart as I was adding a power wheel to it so that I can adjust the hammer externally. I slapped it back together and filled it. I loaded two mags with the 33.95. I backed the hammer spring out. By now I had a 5mph wind out of the SE. I shoot west to east. First shot was about 3ft to the left and 3ft low. The reg set at 2600psi it started at 813fps. I brought it up to 890fps with the hammer spring. It was 880fos by shot 20 and was at 2600psi in the tube. I could not put more than 5 pellets out of 18 on the 18” x 24” (HxW). backer board. I’m far from a ballistic expert, but I’m guessing: spiraling. I have no idea what the optimum velocity for these pellets is.

Do not feel bad at all man, those .22 33.95 are just, not good . I have never seen a rifle shoot them well, when I had my alpha wolf, due to the ease of adjustment on that rifle I tried all the way from 800fps to almost 1100 fps lmao nothing worked.

 

[Billm]

I don’t think they did well at 50yds either. I’ll find a use for them lol. I will say that the extreme velocity spread is very good on this Barra.

 

[Pumacarl]

I don’t think they did well at 50yds either. I’ll find a use for them lol. I will say that the extreme velocity spread is very good on this Barra.

Yeah, I was thinking the same thing. Your gun runs really hot! Could you snap a picture and show what you did for a power wheel? I'm curious, thanks!

 

[Billm]

This a prototype lol. I’m still working on it. I made a folding adapter first, but I wasn’t happy with it.

 

[Billm]

It’s a thumb wheel. I need to get rid of the Lead Sled and add a straight grip.

 

[Pumacarl]

Holy Smokes! Me likee! That is really cool, great job! How did you handle the weird thread size for the buffer tube?

 

[CTAirgunner]

It’s a thumb wheel. I need to get rid of the Lead Sled and add a straight grip.

That came out great! is it just an adapter, or is it part of the stock as a whole?

 

[Billm]

The thread appears to be a gas thread. Seems to be possibly tapered. I made probably 20+ different threaded test plugs with various offset faces to make it work. I need to do some more work on the stock.

 

[Billm]

That came out great! is it just an adapter, or is it part of the stock as a whole?

That’s the third iteration of the stock. Originally I designed it with a folding stock adapter that had a port to adjust the hammer spring - it was a pain though. So I incorporated the power wheel into the stock. I need to modify it a little and make the adjustment smoother. I also need to move the stock adjustments around.

 

[Cantona256]

What regulator pressure are you running and what are the diameters of your slugs? For reference, I opened my thimble port from 4mm to 4.3mm and am running my reg at 2300psi and with .2175 24.8gr NSA slugs am doing 925fps.

How much power do you think you got from opening the thimble port?

 

[Pumacarl]

How much power do you think you got from opening the thimble port?

I'm not sure how to figure that number out, but basically if you increase the reg by 140psi, whatever your new speed is minus your old one and then use the ballistic calculator to determine the power by the difference. I don't remember what the new speed was because I instantly turned it back to what it was before.

 

[Pumacarl]

The thread appears to be a gas thread. Seems to be possibly tapered. I made probably 20+ different threaded test plugs with various offset faces to make it work. I need to do some more work on the stock.

@Billm

I found a post where Barra says what the actual thread pitch is:

Barra 250Z Question

Has anyone changed the buttstock on their 250Z yet? I have a really good Luth-AR on my Armada that I want to change over, but for the life of me, I can't seem to get this original off the "buffer" tube. I tried just swapping out the whole assemblies but the Armada is MIL Spec and I can only...

www.airgunnation.com

I found another post where the guy supposedly rethreaded the old one in place:
Post in thread '250z'

Barra - 250z

Did anyone come up with a solution yet to add a side folding stock to the Barra 250z? The buffer tube is mil-spec, but from what I have been hearing the threads are not. Does anyone know what the threads are and if there are any adapters available for that specific thread? I just received a 250z...

www.airgunnation.com

 

[Billm]

@Billm

I found a post where Barra says what the actual thread pitch is:

Barra 250Z Question

Has anyone changed the buttstock on their 250Z yet? I have a really good Luth-AR on my Armada that I want to change over, but for the life of me, I can't seem to get this original off the "buffer" tube. I tried just swapping out the whole assemblies but the Armada is MIL Spec and I can only...

www.airgunnation.com

I found another post where the guy supposedly rethreaded the old one in place:
Post in thread '250z'

Barra - 250z

Did anyone come up with a solution yet to add a side folding stock to the Barra 250z? The buffer tube is mil-spec, but from what I have been hearing the threads are not. Does anyone know what the threads are and if there are any adapters available for that specific thread? I just received a 250z...

www.airgunnation.com

I saw that. I should have edited my previous post. I use Fusion 360 for CAD and it wouldn’t allow that thread as it’s a non-standard metric diameter. The issue is 29mm is not a standard metric pipe thread. Their standard jumps from 28mm to 30mm. I used a standard imperial thread that was close and then changed the tolerances until it fit. I had some resistance when threading it in about 90% of the way and so I thought it might be a gas thread (before I knew the correct thread was M29-1.5). I’ve since learned how to add a custom thread in Fusion 360 with an XML file and so now I can print the correct thread size. I’ve already lost my Castle Nut for the Barra, from swapping back and forth lol.
There’s not a lot of metal left for tapping if anything goes wrong lol. I keep getting sidetracked and starting other projects, instead of finishing the stock. I also need to redo the folding stock adapter. I’ve thought about making a new stock/chassis and embed a tube with the correct mil-spec.. But it would have to be a two piece stock. Then I thought of machining a laminate stock similar to the Red Wolf.

 

[Pumacarl]

I saw that. I should have edited my previous post. I use Fusion 360 for CAD and it wouldn’t allow that thread as it’s a non-standard metric diameter. The issue is 29mm is not a standard metric pipe thread. Their standard jumps from 28mm to 30mm. I used a standard imperial thread that was close and then changed the tolerances until it fit. I had some resistance when threading it in about 90% of the way and so I thought it might be a gas thread (before I knew the correct thread was M29-1.5). I’ve since learned how to add a custom thread in Fusion 360 with an XML file and so now I can print the correct thread size. I’ve already lost my Castle Nut for the Barra, from swapping back and forth lol.
There’s not a lot of metal left for tapping if anything goes wrong lol. I keep getting sidetracked and starting other projects, instead of finishing the stock. I also need to redo the folding stock adapter. I’ve thought about making a new stock/chassis and embed a tube with the correct mil-spec.. But it would have to be a two piece stock. Then I thought of machining a laminate stock similar to the Red Wolf.

It all gets pretty involved doesn't it? This, is, a hobby. It actually is a little bit of a let down to accomplish the initial task you set, bitter sweet. I am kind of there now, except for the fact that I don't have a folding stock.

What did you think about the second post where the guy used 1 3/16 -16? Is that the size that you used? I don't know yet if I am going to try it on this stock, I have a lot of time into it already. I am waiting for someone to come up with an adapter.

 

[Billm]

It all gets pretty involved doesn't it? This, is, a hobby. It actually is a little bit of a let down to accomplish the initial task you set, bitter sweet. I am kind of there now, except for the fact that I don't have a folding stock.

What did you think about the second post where the guy used 1 3/16 -16? Is that the size that you used? I don't know yet if I am going to try it on this stock, I have a lot of time into it already. I am waiting for someone to come up with an adapter.

I’ll redo the adapter with the correct thread and see how it comes out.

 

[Cantona256]

What regulator pressure are you running and what are the diameters of your slugs? For reference, I opened my thimble port from 4mm to 4.3mm and am running my reg at 2300psi and with .2175 24.8gr NSA slugs am doing 925fps.

I ported my thimble valve from 4-4.4mm and my baby is shooting really nice now. I haven’t pushed it for more power yet. Just went back to where I was (in terms of FPS) and found that I’m at 2600psi instead of 2900psi and between 20-25 shots per fill instead of 10-15…I’m a little surprised it worked out so well. Why do you think opening the thimble port helps so much without opening the block and transfer valve too? I was told to not expect much difference.

Anyways I brained a big ass jackrabbit from about 40 yards last night… the smack from the 40gr Apolo was LOUD haha…