Tuning Sub half MOA air rifle

[explorer]

Hello folks,

Im just somehow getting bored with the general "subMOA" accuracy rule.
Started to brainstorm about the "sub0.5MOA" accuracy class. Lets clarify, it doesnt mean some one group per year on a lucky day but consistent, moreless "all the time" sub 0.5 MOA grouping. I set my goal to 100m with no wind for this.
For the first is there some so hell accurate air rifle on the market? Mostly talking about FAC rifles but not super high energy, maybe up to 40-60J (to make it easier to hold for the 0.5 MOA accuracy) but sub12 could be also.
Im sceptic that its so easy just to order a rifle and thats all. Im ready to experiment, modify, do custom rifle parts, etc. Basically any tuning.
But if you would be an engineer, and you have been told "hey make me a sub 0.5MOA air rifle" what would be your starting point. What rifle you would get to start from as a baseline? (no, please just dont write FX impact)
I have a Prophet 2 in .25 and its capable for 0.7 MOA groups pretty easily, without any custom special modifications. Maybe it would be a great rifle to start with with a .22 barrel. I believe the .22 is similarly accurate as the .25.
What would you start with and what is your opinion in general? Please not that this topic is meant to be "scientific" and sophisticated. So try to aim your comments this way.
Thank you.

 

[Sqwirl57]

I'm a bit skeptical that a sub 12 pellet could hold half MOA at 100yds period even under perfect atmospheric conditions. Sub 12 pellets seem to start doing some weird things right around the 80yd mark in my experience.

 

[cavedweller]

Hello folks,

Im just somehow getting bored with the general "subMOA" accuracy rule.
Started to brainstorm about the "sub0.5MOA" accuracy class. Lets clarify, it doesnt mean some one group per year on a lucky day but consistent, moreless "all the time" sub 0.5 MOA grouping. I set my goal to 100m with no wind for this.
For the first is there some so hell accurate air rifle on the market? Mostly talking about FAC rifles but not super high energy, maybe up to 40-60J (to make it easier to hold for the 0.5 MOA accuracy) but sub12 could be also.
Im sceptic that its so easy just to order a rifle and thats all. Im ready to experiment, modify, do custom rifle parts, etc. Basically any tuning.
But if you would be an engineer, and you have been told "hey make me a sub 0.5MOA air rifle" what would be your starting point. What rifle you would get to start from as a baseline? (no, please just dont write FX impact)
I have a Prophet 2 in .25 and its capable for 0.7 MOA groups pretty easily, without any custom special modifications. Maybe it would be a great rifle to start with with a .22 barrel. I believe the .22 is similarly accurate as the .25.
What would you start with and what is your opinion in general? Please not that this topic is meant to be "scientific" and sophisticated. So try to aim your comments this way.
Thank you.

yep,,,, called a thomas

 

[TheShooter (aka Seeker)]

After more than 10 years in the PCP world I am yet to see a sub half MOA airgun. I shoot at 50 meters indoors. Look at my 5 shot groups at that distance:



The problem is this is not a precision test. The proper test looks like that:


Many groups at the same page. I simply disregard cherry picked groups. Proper tests need to be done in ideal conditions with no wind as a factor.

 

[dgeesaman]

Hello folks,

Im just somehow getting bored with the general "subMOA" accuracy rule.
Started to brainstorm about the "sub0.5MOA" accuracy class. Lets clarify, it doesnt mean some one group per year on a lucky day but consistent, moreless "all the time" sub 0.5 MOA grouping. I set my goal to 100m with no wind for this.
For the first is there some so hell accurate air rifle on the market? Mostly talking about FAC rifles but not super high energy, maybe up to 40-60J (to make it easier to hold for the 0.5 MOA accuracy) but sub12 could be also.
Im sceptic that its so easy just to order a rifle and thats all. Im ready to experiment, modify, do custom rifle parts, etc. Basically any tuning.
But if you would be an engineer, and you have been told "hey make me a sub 0.5MOA air rifle" what would be your starting point. What rifle you would get to start from as a baseline? (no, please just dont write FX impact)
I have a Prophet 2 in .25 and its capable for 0.7 MOA groups pretty easily, without any custom special modifications. Maybe it would be a great rifle to start with with a .22 barrel. I believe the .22 is similarly accurate as the .25.
What would you start with and what is your opinion in general? Please not that this topic is meant to be "scientific" and sophisticated. So try to aim your comments this way.
Thank you.

I would start ten meters from the target and pick up a match air rifle. Almost any one will do.

To hit 1/2 moa at longer distances we probably need higher quality pellets than what is currently available. It can be done, but a lot of things have to be perfect and a mouse fart of wind will open it up.

David

 

[thomasair]

Outdoors in wind at 100y and 50y. 140 shot average each. Average MOA written on top of each card. Thomas slug rifle.

Mike

 

[SpiralGroove]

Yes,
Spectacular Shooter & Gun!

 

[TheShooter (aka Seeker)]

Outdoors in wind at 100y and 50y. 140 shot average each. Average MOA written on top of each card. Thomas slug rifle.

Mike

View attachment 386946View attachment 386945

I just need that barrel. How can I get one? Barrel blank is good enough.

 

[nervoustrig]

No doubt the barrel (and its preparation) is key, but I think there’s a little more going on to get a sub-0.5 MoA average for so many shots in real-world conditions.

 

[SpiralGroove]

Yeah Jason, but for those lesser inclined (ME), the barrel would be a great start.

 

[Vetmx]

I just need that barrel. How can I get one? Barrel blank is good enough.

The barrel will just be a pry bar unless you can get the mold to make the slugs that fit the barrel.

 

[beerthief]

ill try 5 shot groups , 30 meter challenge target @ 15 yards, see what happens outdoors then 20 yards and so on out as far as my gun will shoot .

 

[TheShooter (aka Seeker)]

The barrel will just be a pry bar unless you can get the mold to make the slugs that fit the barrel.

Of course you are right. I cooperate with folks to make custom slugs for my specific barrel. I aim at the groove diameter +0.01mm. Otherwise it is a waste of time and money.

 

[TheShooter (aka Seeker)]

No doubt the barrel (and its preparation) is key, but I think there’s a little more going on to get a sub-0.5 MoA average for so many shots in real-world conditions.

Well, there are many details and I can easily write at least an article how to avoid mistakes during barrel blank preparation. A perfect barrel blank is just an initial step. During the machining many things can go wrong making mentioned perfect barrel blank a useless piece of steel. However, the risk can be minimized if one follows certain steps.

 

[John "spysir" Blount]

I just need that barrel. How can I get one? Barrel blank is good enough.

Easy, buy a Thomas rifle.

John

 

[JimD]

Airgun ES and standard deviation are better than powder burners can achieve. So there is an advantage for airguns and benchrest powder burners are easily better than 0.5 MOA. But you need to be careful with those parts too, the ~10 fps ES for a reasonable shot string is not automatic.

I think pellets are an inherent weakness at 50 to 100 yards due to the very poor ballistic coefficient. Even airgun slugs are lousy ballistically. Probably an order of magnitude worse than powder burner target bullets. I'm not sure how much of that can be "fixed". Airguns do not shoot jacketed bullets, the pressures are too low, but better lead "slugs" should be possible. But apparently that Thomas was shooting slugs that were good enough. Wind drift is worse when the ballistic coefficient is low.

It seems like its a matter of putting an air supply on the gun that will achieve low ES and Std dev, putting a good barrel on it, and putting a good, consistent projectile down the barrel. Swaging the projectile seems like the right technology. The barrel could be one intended for a powder burner. I don't know what the current technology is but they used to talk about air gauged barrels. Extremely consistent, extremely smooth barrels for the finest benchrest guns. The steel in a powder burner barrel is overkill for an airgun but I don't know why it wouldn't work well.

 

[Jaxjax]

I just need that barrel. How can I get one? Barrel blank is good enough.

What needs to happen is we need to get a few more of these barrel companies on board with offerings that work with slugs available now & common So as I take it we need grooves spec in .22 of .216 to .219. with various twist rates. ? .215-.220 is already available as tight bore .22rf in 16 twist. McGowen has same in 6.45x39 w/ 8 twist
Prefferd Barrel Blanks in Utah seems open to such things. I'm sure others are too. Seems $ are the big factor of not having more barrel options. Someone off AGN w/ slug & barrel knowledge should start a group custom barrel build with a manufacture on board. as it sits, mid levlel blanks are $250-$450 for button but at least they are air gauged to .0002 or 0001 in TIR. Maybe LW is close to this spec but I dought it for what we can get for blanks.
Why hasn't NSA or someone gone to .220-.221 .222 options as these barrels are a gazzillion deep .
Joe

 

[nervoustrig]

Well, there are many details and I can easily write at least an article how to avoid mistakes during barrel blank preparation.

That would be fantastic. If you don't want to start a new thread, the following one would be a good place for it:

Finishing A New Barrel Blank ?

I'd like to try my hand at finishing a new barrel blank. I understand concentricity, crowning and threading. Could some of you with hands on experience talk about the pellet chamber and lead in? I learn fast so share all you're willing. Do you leave freebore or try to start the projectile...

www.airgunnation.com

 

[_CTAIRGUNNER_]

Sub 12 rifle, sub half moa at 100? even at an indoor range, thats a tough task.

 

[Jaxjax]

This seems to makes sense to me in one small part of the entirety.....this is from a 2015 artical on PB barrels

.Jacketed lead-core bullets and waxed lead bullets in a .22 rimfire are actually quite soft. Under the pressures of firing and initial engagement into the throat, the bullet is either squeezed down in size to conform to the barrel diameters or is obturated up in size to fill the barrel. A variation of several ten thousands in size between the bullet and barrel in either direction does not seem to have any meaningful effect on accuracy. But, as we mentioned, once the bullet conforms to the barrel size, it is very important that the barrel does not change size. This is especially true of an increase in internal barrel diameters as the bullet travels towards the muzzle. This situation is similar to the decreasing twist rate we already talked about. And a decrease in diameter away from the chamber is akin to a tightening of the twist rate.

the above seems helpfull in what a pellet goes thru as I know we don't have the pressures to do it with slugs. But with slugs at .0005 +/- with groove it seems that tight tolearnces in TIR would be way up on the list of things to start with. I'm probably wrong, but this is the road I'm going down for abit.

When I read over the years of certain people from time to time saying that cleaning a airgun barrel is bad, blew there grouping up, etc, etc....To me I take them for there word but I wanna no WHY !!!! I feel its because something isn't correct from the get go for given ammo & barrel combo. Flaws in barrel internals covered up by lead..... I just looked down my pulled Poly .30 I acquired from another & it looks like crap.. chunky lead everywere & no way in heck I will shoot it like this. I won't put not 1 pellet down it before I deem it clean for a baseline to start.
Joe