Barnes vs. Hornady GMX

[ArmedBear]

I loaded up 10 rounds to test the pressure.

My best known load with Hornady 165 grain BTSP bullets is 56.5 grains of IMR 4350, about .005" shorter than OAL spec. It shoots sub-MOA in my rifle.

Since the GMX bullets extend a good 1/8" farther into the case than the BTSPs, I started low, at 55.5 grains, and loaded 3 more with 56, 3 more with my regular 56.5.

I also loaded the GMX to .004"-.005" shorter than spec OAL (which is .010" longer than the BTSP, at least according to the guy I called at Hornady).

With the BTSPs, 56.5 grains is a just-so load, right about at 100%.

It becomes a compressed load with the GMX bullets. This didn't seem to change anything: no signs of overpressure, and it was still the most accurate load among the few I tested.

The downloaded charges shot lousy groups.

The 56.5 grain load, despite now being compressed, was about as accurate as it is with BTSPs. I shot a 1" 3-shot group with it, but off a rest that wasn't as stable as I used to test the BTSP load. So I'm going to guess it's good for sub-MOA until I do further testing.

I just loaded those 10 because the guy at Hornady suggested lowering the charge a bit for initial pressure testing (though he also said that most of the guys there did end up finding that their regular loads were safe and shot best with GMX after testing).

I didn't want to shoot too many those dollar-a-shot loads just to see which ones were overpressure!

So, I'll be loading more, and posting more.

Thumbs up so far.

 

[~z]

Thanks for the update, look forward to more.
~z

 

[Dr. Tad Hussein Winslow]

Nice report; thanks! What cartridge are we talking?

 

[moosehunt]

I believe that what they mean by "interchangeable" with their other bullets is that the loading data is interchangable within a specific caliber/weight, as opposed to Barnes bullets where loading data is not generally interchangable with standard bullets. I don't think they mean that the GMX of a specific weight/caliber will shoot exactly the same as another of theirs in same weight/caliber, but you don't need special data.

As to the less than superb BC of the Barnes bullets, out to 350-400 yards, even a bit more, it isn't going to make enough difference for you to even notice under hunting conditions. You are having yourself a big to do over nothing!

 

[ArmedBear]

I don't think they mean that the GMX of a specific weight/caliber will shoot exactly the same as another of theirs in same weight/caliber, but you don't need special data.

True.

However, the 165 grain GMX and the 165 grain SST shot within an inch of each other yesterday. I have to get my seating depth figured out, then I'll post a bit more. Right now I'm getting just over 1 MOA from both SST and GMX, but I think I have to go .005" shallower to match the .7" groups I was getting with Hornady BTSPs.

Group size with SST and GMX bullets seems identical.

The only thing I do wonder about is gilding metal and expansion at lower velocities. OTOH I don't know how Barnes bullets expand at lower velocities either (say 400 yards out). Does anyone?

Tad- .30-'06 in a Vanguard Sporter. 165 grain bullets over 56.5 and 57.0 grains of IMR 4350.

 

[moosehunt]

It is kind of hard to know regarding expansion on Barnes bullets because one rarely recovers one. I have gotten exactly 1 out of many dozens shot at game--that from the paunch of an Eland shot stem to stern. Based on wound channels, I suspect they are still expanding at pretty reduced speed. That is based on a few examples at 400-500 yards, and one at about 700 on an elk--still passed through, but wound channel looked to me like expansion had indeed occurred. One of Barnes claims is that they expand at widely varying velocities. I sure haven't seen anything that makes me question that. Incidently, I don't normally take shots that long. There were extenuating circumstances, and I don't intend to do it again--though things worked out fine.

 

[driftrider]

I noticed that someone mentioned the relatively low BC numbers for the TSX family of bullets.

I think that part of the reduction is due to the relief cuts in the shank. But I also believe that a big part of the reason is that Barnes may be actually trying to publish honest and accurate BC for their bullets. I noticed that a lot of their bullets on their website don't have BC's listed, and there is also a note that states that Barnes is working to retest and publish new BC figures based on 300 yard velocity and trajectory data. This is great since most manufacturers use either theoretical BC's based on the caliber, weight and shape of the bullet, or use 100 yard velocity data because the shorter range means the bullet is traveling faster, with makes the calculated BC higher. The problem is that the G1 standard isn't very good at predicting the performance of modern tangent and secant ogived, boat tailed bullets. With the G1 standard the BC will always be much higher than, say, the G7 standard which, while a much better predictor of the trajectory of modern rifle bullets, gives much lower BC numbers. The G1 is very velocity sensitive, with the BC dropping as the velocity drops. This is why many manufacturers calculate the BC based on short range data, to inflate the numbers. The problem is that the BC of a bullet from the muzzle to 100 yards is different than the BC from 100-200, 200-300, etc. By using 300 yard data, the BC for the Barnes bullets better reflect the actual performance of the bullet out to about twice that distance. Most long range shooters I've talked to correct their BC's for the longer ranges, since at very long range the published BC is seldom accurate enough to produce accurate trajectory tables.

If Barnes is trying to publish accurate BC data, even if it means that their numbers will be lower than their competitors, I commend them.

Mike

 

[moosehunt]

Factual, and well stated! Why is this such a mystery to so many people?

 

[~z]

I believe you are correct about the shank cuts (I have no facts, graphs, or figures to back this up) these relief cuts appear as though they would create turbulence and reduce the BC. However, as to your comment about other bullet manufacturers inflating their BCs, wouldn’t it be nice if someone would do a comparison at say…600 yds? “… for several years Bryan Litz has been fire testing nearly every popular long range bullet to establish true and comparable BC data. Bryan’s efforts have produced a wealth of information which will soon be available to all shooters in his book Applied Ballistics for Long Range Shooting.”

Cant wait to read.
~z

 

[ArmedBear]

Finally did it!

Range Report with pictures here: http://thehighroad.org/showthread.php?t=458690

 

[moosehunt]

Damn! You computer guys are always putting things up as "look here"--then you put it in some kind of code. What the hell does that code mean? I read nothing out of it.

 

[ArmedBear]

On mine it's a link. Just click on it and you'll go to the thread.

Is it not a link on your computer?

If not, go to the Rifle forum and scroll down. It's still on the first page.

 

[moosehunt]

Now I think I'm getting an education. Link. I've seen that referred to before. Just what is such? Click on what? I'm feelin' more like a computor wizzard already, though I guess I really haven't accomplished anything yet!

 

[ArmedBear]

Click on the following text: http://thehighroad.org/showthread.php?t=458690

That should bring up my post in the Rifle forum.

 

[moosehunt]

That was pretty slick! I put the little fist with a finger on the http and it all turned red. I pushed the button, and was soon in a new place. Cool! I'm learning to be a computor wizard! My grandson won't laugh at me next time I see him! At this rate, I'll be teaching him. Thanks for the lesson. I'm surmising at this point that anytime I put that little finger on a code and hit the button, I'll get somewhere, correct?

 

[ArmedBear]

Yup. That's how this thing works.

The idea of random linking is why the World Wide Web is called a "web." It's like a big bunch of connections going every-which-way.

Earlier attempts at presenting Internet information relied on tables and heirarchies. None of them caught on with the general public. The Web changed that, and the link is the basic element of the Web.