Hornady 7mm 139 GMX tips?

[Newtosavage]

I've always had pretty good luck with Hornady bullets, and now that I've made the switch to monos, I wanted to at least try something different than the Barnes TTSX and TSX. So the other day I picked up a box of 139 GMX's, thinking they should shoot pretty well. I liked the higher BC they offered too.

Well they shoot terrible. LOL Out of both my Tikka and my Howa, I haven't yet shot a group under 1.5" at 100 yards. Both of those rifles routinely give me 1" or better. Yesterday, I shot a group at 300 yards with my howa and 120 TSX's that I could cover with a quarter.

Is anyone using these 139 GMX's? If so, how far off the lands are you and do you have any advice? I don't want to just give up on them. The 140 TTSX's don't shoot very well from my Howa, but they shoot great from my Tikka. The 120 TSX's shoot great from my Howa, but not very well from my Tikka, surprisingly. I was hoping to find a 140-class mono that shot well from both rifles. So far, no bueno.

I might try Nosler E-tips next.

 

[MrTim]

In a t3 7mm-08 that I have loaded for, the OAL is limited by the magazine length @ 2.810”. So, I have 139 GMX seated approx .112” off the lands so that they just fit into the magazine and cycle properly. I tried seating deeper...but longer was better.

 

[Newtosavage]

In a t3 7mm-08 that I have loaded for, the OAL is limited by the magazine length @ 2.810”. So, I have 139 GMX seated approx .112” off the lands so that they just fit into the magazine and cycle properly. I tried seating deeper...but longer was better.

Okay, I appreciate that.

My Tikka does not have that limitation since I did the bolt stop and magazine modification. However my Howa is limited to 2.80" max.

I need to check the distance to the lands on my Howa and see what I get at 2.80. I think I'll try and start with 0.1" off if that's possible.

 

[MrTim]

Okay, I appreciate that.

My Tikka does not have that limitation since I did the bolt stop and magazine modification. However my Howa is limited to 2.80" max.

I need to check the distance to the lands on my Howa and see what I get at 2.80. I think I'll try and start with 0.1" off if that's possible.

Regarding the bolt and magazine mod... have you had any feeding issues with factory length ammo?

 

[Joelweb]

I'm running those bullets in my .280 AI. I couldn't get Barnes bullets to shoot, but am getting .7" groups with the 139 grain GMXs. My overall length is limited by the magazine.

 

[Newtosavage]

Regarding the bolt and magazine mod... have you had any feeding issues with factory length ammo?

I haven't used factory ammo since doing the mod, but I have loaded TTSX's in it at 2.80" with no problems at all. I have never seen a down side to that modification.

 

[Newtosavage]

I'm running those bullets in my .280 AI. I couldn't get Barnes bullets to shoot, but am getting .7" groups with the 139 grain GMXs. My overall length is limited by the magazine.

I'm going to back my GMX's off to 0.1" and see if they shoot out of either rifle. I have about 35 left, so hopefully I'll find a good node. I would love to use them out of both my Tikka and Howa and get down to one bullet finally. Right now my Tikka shoots 140 TTSX's and the Howa 120 TSX.

 

[swampthing]

I had great accuracy out of the 130 gmax in my 270. I couldnt get the 139s to shoot in my 708

 

[Newtosavage]

Okay, I backed off 0.5 grains and they dialed right in with my Tikka. Sub-MOA out to 300 yards (about 2.25" by my tape). Howa liked them more but still not as much as the Tikka. So, 120 TSX's for the Howa, and 139 GMX's for the Tikka, which is perfectly fine with me since the Tikka is my western gun and the Howa my eastern gun.

I didn't take my chrono today, but according to my measured trajectory from 100 to 300 and the published BC, I'm getting 2950 fps. with the GMX's - about 50 fps more than I got with the SST's.

Oh, and these were a full 0.1" off the lands for my Howa, and more than that for the Tikka. COL was 2.775" They sure do like a jump!