Seating depth on Lead-Free bullets.

[mycrstuff]

I'm finally gettting around to loading up my Hornaday GMX bullets. They have 2 cannelures on them. I have checked around other forums and the consenus is that they are not for crimping but grooves to reduce surface area contact when the bullet goes through the barrel.

Where am I supposed to crimp these? I am loading 150 grn 30.06 rounds. If I use the standard OAL of 3.340 the top groove or cannelure is in front of the case. If I put the top cannelure at the case mouth then the length is too short. These are Loooooooong bullets so they already have way too much of the bullet inside the case.

Some of the guys on the other forums thought it was ok to have the grove/cannulure in front of the case on these. No one posted a photo so I wasn't sure if what they were saying was ok. Here are some photos of the bullets and a round seated at 3.35. It is just slightly short of the max OAL. The bullet in the center is a standard lead filled 150 grn FMJ. The one on the left is a 150 grn GMX lead free bullet. You can see on the loaded round that the cannelure is in front of the case.

Let me know what you think.
http://i770.photobucket.com/albums/x...6/IMG_0340.jpg[IMG]

[/IMG]

[mif_slim]

Don't worry about the cannulare. Reload to ur oal and shoot.

[Corbin Dallas]

Don't worry about the cannulare. Reload to ur oal and shoot.

Correct.

Just remember, frangible ammo requires MUCH less powder than standard rounds. The manufacturer should have provided you with the proper numbers according to what type of powder you are using.

[CSACANNONEER]

Where did you find load data for these? I sure hope that you did not just use a recipe for lead 150 grain bullets. These are a totally different animal.

[ADAM]

thats funny i got hornady gmx 6mm 85gr it was not boat tail

[FLIGHT762]

Where did you find load data for these? I sure hope that you did not just use a recipe for lead 150 grain bullets. These are a totally different animal.

From the Hornady website:



"GMX bullets are constructed of the same gilding metal used to make ultra-consistent Hornady bullet jackets. Gilding metal doesn’t foul like “sticky” solid copper, and strategically located grooves in the bearing surface of the bullet reduce pressure. These additions make the GMX easy to load using standard published data for comparable Hornady SST bullets.

Hornady engineers designed the GMX bullet to perform across a very wide range of velocities - from +3,400 to 2,000 fps. And perform it does. GMX bullets are designed to expand to 1.5 times their original diameter and retain over 95% of their original weight. They’re no slouch in the penetration department either, routinely penetrating over 30" in gelatin tests."


Since these bullets are new and limited data is available, I'd load to a C.O.L. of .030"-.050" from max C.O.L. (3.340" for the 30/06). Just be sure you're not jamming them into the lands.

I have shot the 130 gr.GMX 270's in my Tikka T-3 in .270 Win. I used regular data as recommended by Hornady and had no pressure issues. My Tikka has a long throat and I couldn't get near the lands even at max C.O.L.

As stated in the quoted Hornady information, the grooves in the bullet are not crimping(cannelures) grooves,they are pressure relief cuts similar to the Barnes TSX's.

[mycrstuff]

Thanks for the help everyone. Adam if you look at the GMX on the Midway site you will see they are all boat tail except for the 6mm. I will take Flight762's advise and cut the OAL slightly.

My only other concern with this round is you need to push it to 3000 fps to get the full expansion on it. This is above the max load for most of the powders listed in the Hornady manual. I am going to load at 51.00grns of 4064 to get between 2800 to 2900 fps. This is within 5% of max. The other powders listed where 2900 fps was not listed as the max use 5-7 grains more powder so that case volume becomes an issue. I don't think I would be able to get the bullet seated deep enough if that much powder is in the case.

[mycrstuff]

Whoops!! We have a problem. I tried chambering the round and it did not fit in in a 1903 or M1917. I tried another one that I had not crimped yet and it pushed the bullet up to the bottom of the first cannelure before it would close. It is still hard to close the bolt. It appears that the bullet is too fat towards the front and that I will need to seat it deeper to be able to chamber it. Good thing I tried this before I loaded a batch.

[brianinca]

>>>>
My only other concern with this round is you need to push it to 3000 fps to get the full expansion on it. This is above the max load for most of the powders listed in the Hornady manual. I am going to load at 51.00grns of 4064 to get between 2800 to 2900 fps. This is within 5% of max. The other powders listed where 2900 fps was not listed as the max use 5-7 grains more powder so that case volume becomes an issue. I don't think I would be able to get the bullet seated deep enough if that much powder is in the case
>>>

How do you figure that? Did you READ the Hornaday blurb? A few hundred feet per second isn't going to make a LICK of difference to the deer you knocked down. They state those numbers as muzzle velocity, not downrange velocity, and they're bragging that the bullet will hold together out of a 30-378. This bullet may be used in a wide variety of cartridges, so they're covering all their bases.

308 reloaders are going to see some issues, I did with the Barnes TSX, but 3006 gives you PLENTY of case capacity. Be more worried about how good a shot you are offhand and less worried that you don't have a 300 WinMag.

Regards,
Brian in CA

Edit to add: "It appears that the bullet is too fat " - they went to a blunter ogive profile to get more mass in a shorter length, you'll still have plenty of case capacity. Also make sure you full length resize hunting ammo.

[mycrstuff]

I got test info on the round from the Chuck Hawks website. If I can I would rather keep away from the max load. Here is the link see if you agree with his findings.

http://www.chuckhawks.com/hornady_GMX_bullets.htm

[toby]

You do not need to push this bullet to 3000 fps??? to make it work that is BS. it will work at about 1800fps and up> and if you need some speed do a compressed load? if you dare!