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Thread: Hornady gmx

  1. #1

    Hornady gmx

    I am aware that Barnes TSX and TTSX (130 & 150, 30 cal) like to be seated deep (45 thou off the lands), anybody know if Hornady GMX (150, 30 cal) are the same ?

  2. #2
    I did not to manage to work up a load which improved on the factory 150 GMX….I sold the gun part way through the process and have to start again.

    How well do the factory GMX shoot from your gun? If that is good enough for you, then sticking to the book C.O.L. of 2.735" would be a good start.

    On a whim...I have just measured the last four factory rounds I have and they vary between 2 @ 2.731" 1 @ 2.734" and 1 @ 2.737" These have been in and out of the magazine and my pocket a few times.

    Not that it necessarily helps you...but I have been working on a load for 130grain TTSX for my .308 and the one group of seven I tried at the 50 thou off the lands was worse than the groups I had from the book C.O.L. of 2.810"

    The jerk on the trigger as well as the jerk on the end of the trigger combine to make the most variable factor in the equation for me though...

    Alan
    Last edited by Alantoo; 04-10-2015 at 10:32.

  3. #3
    Barnes bullets should be seated a minimum of 40 to 50 thou off the lands as a start point. ( Barnes own recommendation) as being copper monolithic bullets high pressure can result if seated closer than that. The Hornady bullet is a solid Guilding metal projectile and is harder than the Barnes and is more tolerant in regards to pressure when seated close to the rifling. Hornady themselves state that it can be loaded to the same OAL as their other projectiles ,and use the same data as other bullets of the weight .WE can confirm this . We have loaded them for Africa bound clients and they have had great success . One Gent took 21 animals with 22 rounds. ( a big eland bull took two rounds to anchor) . I have found that they do not foul quite as badly as the Barnes and they are available in 100 ct boxes , at less than the cost of the Barnes. So all in all we are very positive about them . One must always remember though that a rifle will shoot where it is going to shoot with regards to seating depth. some rifles like the rounds tight on the lands others may like the bullets up to 100 thou off the lands . Until you test there is no way to know. I hope that is of assistance, Yours respectfully Mike Norris Brock and Norris Custom Rifles
    Last edited by brock and norris; 04-10-2015 at 10:31.

  4. #4
    Quote Originally Posted by brock and norris View Post
    Snip...The Hornady bullet is a solid Guilding metal projectile and is harder than the Barnes and is more tolerant in regards to pressure when seated close to the rifling. Snip...
    Any ideas why the harder bullet is more tolerant? I would have thought it would create the opposite effect and require more pressure to engage and deform to the rifling.

    Certainly when I am working Gilding Metal and Copper I have to hit the Gilding Metal harder...

    Alan
    Last edited by Alantoo; 04-10-2015 at 11:43. Reason: Gilding / Guilding personally, I blame the predictive text...

  5. #5
    Barnes bullets should be seated a minimum of 40 to 50 thou off the lands as a start point. ( Barnes own recommendation) as being copper monolithic bullets high pressure can result if seated closer than that. The Hornady bullet is a solid Guilding (sic) metal projectile and is harder than the Barnes and is more tolerant in regards to pressure when seated close to the rifling.
    Yeah, would quite like an explanation of that non-intuitive example.
    A young man who isn't a socialist hasn't got a heart; an old man who is a socialist hasn't got a head.
    I have summat for sale; here's the M̶i̶d̶w̶a̶y̶ Brownells UK price... effin jokers.
    "The .30-'06 is unstable at close range" - Ahahahahhahh!


  6. #6
    The copper bullet obturates more readily than the guilding metal projectile . if jammed into the rifling the pressures can go up dramatically as the rear of the bullet is fractionally expanded as it goes into the bore requiring more "starting effort" so to speak than if it has the 50 thou jump in which it all ready has momentum . Very much like Weatherby used long free-bores in their chambers to get velocities at safe pressures with the powders that were available at the time. This was more of a problem with the older Barnes X bullet but with the TSX with its three grooves it is less so. The Grooves were added to reduce fouling and to reduce pressure .Take a look at data for Barnes bullets and any other manufacturers data for a similar weight. Using the same powder case and primer the Barnes bullets are always using a lower charge weight to achieve the same velocity, And velocity is a direct result of pressure generated .If you are in doubt then read through the Barnes manuals 1-4 as I have and taken the time to , and speak to the people at Barnes .All the answers are there : Yours respectfully Mike Norris Brock and Norris Custom Rifles

  7. #7
    And the 'guilding' metal part?
    A young man who isn't a socialist hasn't got a heart; an old man who is a socialist hasn't got a head.
    I have summat for sale; here's the M̶i̶d̶w̶a̶y̶ Brownells UK price... effin jokers.
    "The .30-'06 is unstable at close range" - Ahahahahhahh!


  8. #8
    Quote Originally Posted by brock and norris View Post
    The copper bullet obturates more readily than the guilding metal projectile . if jammed into the rifling the pressures can go up dramatically as the rear of the bullet is fractionally expanded as it goes into the bore requiring more "starting effort" so to speak than if it has the 50 thou jump in which it all ready has momentum . Very much like Weatherby used long free-bores in their chambers to get velocities at safe pressures with the powders that were available at the time. This was more of a problem with the older Barnes X bullet but with the TSX with its three grooves it is less so. The Grooves were added to reduce fouling and to reduce pressure .Take a look at data for Barnes bullets and any other manufacturers data for a similar weight. Using the same powder case and primer the Barnes bullets are always using a lower charge weight to achieve the same velocity, And velocity is a direct result of pressure generated .If you are in doubt then read through the Barnes manuals 1-4 as I have and taken the time to , and speak to the people at Barnes .All the answers are there : Yours respectfully Mike Norris Brock and Norris Custom Rifles
    Thank you for the explanation….but please reread my query, I was not questioning your statement or your erudition, just asking for the reason behind the phenomena.

    I had read that the Barnes bullets needed more distance / jump to the lands than the softer lead cored bullets due to the increased pressure generated. I had assumed by logical progression and my knowledge of working all three metals that it was a linear progression of soft to hard...with the hardest material requiring the greatest jump to prevent the pressure spikes.

    I find it interesting that there is yet another layer of variability in the mix!

    Alan
    Last edited by Alantoo; 04-10-2015 at 13:14. Reason: Forgot the "Thank you". and the editor will not allow me to add it for some reason

  9. #9
    Quote Originally Posted by Sauer90 View Post
    And the 'guilding' metal part?
    Guilding metal is a copper/zinc alloy and harder then pure copper. It has less of a tendency to deform under high pressures.

    Of course, that brings up a starting 'other side of the coin' scenario: If this bullet is 'safer' at high pressures, and is meant to be used with any other bullets' data (same weight and diameter) then are we running a hazard using bullets of NON guilding metal construction????!!?? What about thin jacketed match bullets?? I'll be up at night worrying about that one, I tell you.

    Alan. Keep life simple and accuracy consistent. Load to manufacturer's specified OAL. As I've often said, the best match ammo in the world is NOT loaded to X-thou off of anybody's lands.~Muir

  10. #10
    Quote Originally Posted by Muir View Post
    Guilding metal is a copper/zinc alloy and harder then pure copper. It has less of a tendency to deform under high pressures.

    Of course, that brings up a starting 'other side of the coin' scenario: If this bullet is 'safer' at high pressures, and is meant to be used with any other bullets' data (same weight and diameter) then are we running a hazard using bullets of NON guilding metal construction????!!?? What about thin jacketed match bullets?? I'll be up at night worrying about that one, I tell you.

    Alan. Keep life simple and accuracy consistent. Load to manufacturer's specified OAL. As I've often said, the best match ammo in the world is NOT loaded to X-thou off of anybody's lands.~Muir
    It is Mike's description of the relationship between the pressure peak produced by the perfect seal of the softer copper bullets and the extra pressure required by the harder GMX bullets to make them conform to the rifling which I found intriguing. I am surprised that the obturation out trumps the metal deformation. Presumably the GMX bullets also have to seal perfectly before they progress...

    Although the gilding metal mix that Hornady used has much more copper than the 80:20 mix I learned about at school, I wonder about the state the metals are in. Annealed gilding metal (even 80:20) will obviously deform and obturate more readily than work hardened copper.

    I have been following your OAL advice (especially after it coincided with my results! ) My father had this saying about "advice is what you take for the common cold!"

    One day I must start another thread about C.O.L. as used in the Hornady manual; COAL as used in the Barnes data. OAL as used by everybody else in engineering…I always wondered about I.D and O.D. as Internal Diameter would be more logically paired with External Diameter but I digress, Sorry BLUEROLL.

    Alan
    Last edited by Alantoo; 04-10-2015 at 15:39.

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