I can zero my 8" AR9 at 25 yards with one ammo like Federal 125, then shoot Federal 115 and it will group 5" to a side and a little higher. Or zero with Winchester 115 then shoot Federal 115 and same kind of results. I guess I just need to order a crap ton of one ammo that groups well and zero for that. I'm thinking about the American Eagle 147 grain flat point. Is you guys 9mm so random on poi with ammo changes? I could understand some elevation changes but why the wild windage changes? Is that just a quirk with 9mm ballistics?

Sorry, haven’t seen that.  Two custom 9mm builds, one MPX, and they all stay at zero with 115 across ammo manufacturers, with maybe a slight elevation change.

Damn, I think I just need to re barrel this thing. It patterns like a shotgun and always has. Only has about 500 rounds through it. It's a Spinta 8" 1:16 twist. Nobody hardly has 9mm barrels available now!

maybe its that 1:16 twist arent most 9mm barrels 1:10

I am talking (e mail) with Spinta about it. Actually 1:16 is supposed to be ideal but I may switch to a 1:10.

Not trying to be a wise-guy, but I would genuinely love to see a source for that "1:16 is ideal for 9mm" claim.  All my 9mm "long barreled pistols" , as well as my 9mm handguns, are 1:10, and all seem to have the same point of impact, or very close, regardless of ammo. But I'm usually working within 50 yards. 1:16 seems quite slow, but I could be wrong...

From what I understand, higher twist rates are generally necessary to stabilize heavier bullets. So perhaps the slower 1:16 is best for lighter bullets and heavier bullets aren't stabilized as well?

Just a few interesting reads on 9mm Luger twist. There's a lot more out there. Not sure if one of these articles or somewhere else convinced me to try the 1:16

https://www.bullseyeforum.net/t3327-9mm-barrel-twist-thoughts-questions

https://www.shootingillustrated.com/articles/2018/11/27/handgun-rifling-bullet-weights-barrel-twists/

https://www.thehighroad.org/index.php?threads/9mm-x-19-barrel-twist-and-bullet-weight.380276/

https://forum.snipershide.com/threads/twist-rates-in-pistol-barrels.24493/

I got a Spinta 8" SS barrel and it's takes any ammo I feed it.  Have not seen any inconsistency between ammo.  TBO, I can't remember the twist ratio though.  I bought the barrel a long time ago.

I use one of their bcg with the barrel too.

Welcome to Arfcom! I'm honored to have your 1st post! Spinta seems to be working with me. First they wanted me to check all mounts and that my my barrel nut was tight. Lol they don't know me and my love for Loctite. They have offered to look at the barrel and make it right if they find anything. That barrel nut was tight as a tick. And the barrel fit to the upper was also very tight. Usually I loctite the barrel and upper, but didn't in this case due to extremely tight fit. I remember having to tighten and loosen the barrel nut several times to seat the barrel extension all the way in. I had to take a 1 foot piece of 7/8 dowel and spend a lot of time just to knock the barrel out. I could not hold the reciever tight enough in the vise with wooden pads. I had to suspend the barrel in the vise vertically and catch the receiver by the face of the top of the receiver and the lug of the hinge pin. I hope I didn't damage the upper receiver getting the barrel out.

Also Spinta made 1:10 and 1:16 barrels.

Didn't really even realize this was my first post haha!  Been on here for a long time, guess this is the first id had something worth saying.

I've emailed them a few time about how to set up my AR9 (buffer spring and weight).  They have good communication.

I'd say your barrel was plenty tight.  Other than the barrel being loose, I can't think of what would cause it.  What kinda sights you using?

If I figure out the ratio I'll let you know.

At this point, I  think the barrel was fubarred from the start. I tried different red dots and mounts including a Meprolight tru dot RDS folding sights and fixed sights. I had another rifle a few years ago, it just had a bad barrel from the start too. I re barreled it and am happy now. It just groups like a shotgun at 20 yards  like a 5" spread. No- really.

Yeah, sounds like it.

They sending you a replacement?

I don't know yet. I hope. I've got to send it to them to check it out.

@GrimEReaper

Hope you get it worked out and they make it right.

As another said, all mine are 1:10 also.  This 7.5” barrel on my C-5 is a little tack driver, and it cost me something like $50 on Primary Arms.

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