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+--- Thread: 120 grain eldm oal issue (/showthread.php?tid=20330)
120 grain eldm oal issue - RobUrban - 01-03-2020
I just ordered a box of the 120 grain eldm and in my gun, green mountain group buy barrel, they hit the lands at 2.210 inches oal. I have shot factory hornady 123 ag, hornady 123eldm black and handloads with 90gr tnt, 120 grain gold dot and 130 grain rdf at 2.260 oal with most of those bullets contacting the lands at 2.80-2.33. So is it just the shape of the ogive on this bullet? With the reduced oal what do you think would be good load data to use with 8208xbr since hornadys data is at 2.245 oal?
120 grain eldm oal issue - A5BLASTER - 01-04-2020
It's most likely the ojive shape.
120 grain eldm oal issue - LRRPF52 - 01-04-2020
120gr ELD-M is meant for conventional freebore chambers.
123gr A-MAX and ELD-M are meant for the Grendel.
123gr SMK and 123gr Scenar work really well in the Grendel's compound throat.
We used to see the same issue when people tried to load the 120gr A-MAX, depending on the chamber.
I've personally never ordered or purchased the 120gr Hornady target bullets for this reason, but I have mostly SAAMI chambers with the compound throat.
120 grain eldm oal issue - JCSC - 01-04-2020
I had the same concerns and found that upon measurement the 120 eldm has a more blunt Ogive and needs to be roughly .04? shorter than its 123 eldm cousin.
In my Odin works barrel, I hit the lands at 1.685 BTO. This equates to a 2.215 oal.
I ran some 8208 xbr loads at 2.195 oal and they shot quite well.
120 grain eldm oal issue - JCSC - 01-04-2020
For my particular 20? gun I started at 26.3 gr and ran to 27.5 8208.
My second range trip started at 27.7 and I stopped at 28.1, due to some ejector smears. Primers and brass looked good overall.
Use caution and test the capabilities of your particular gun. This was just my experience.
120 grain eldm oal issue - BluntForceTrauma - 01-04-2020
My MONSTER barrels have a standard SAAMI 6.5 Grendel compound angle throat, if that helps.
120 grain eldm oal issue - RobUrban - 01-04-2020
Thanks for the advise guys, I am starting with 26.5 grains and going to work up in 3/10 grain increments. Will post an update how it turns out.
120 grain eldm oal issue - BluntForceTrauma - 01-06-2020
While I'm thinking of it, please remember how the compound throat works. Right at the case mouth the rifling starts with a 0.5 degree angle for the first 0.155 (per SAAMI drawing). This gives what Bill Alexander (its designer) calls a "kiss" to the bullet. It adds only about 800 psi pressure. This design tricks the bullet into thinking, as it were, that it is into the lands but it is not. There might be slight marks on the bullet — within that first 0.155 from the case mouth — when extracted again, but this is not the same as being jammed into the lands. (Both the .30-06 and .270 Winchester SAAMI drawings show a similar throat, where the rifling angle starts right at the case mouth with no "freebore.")
After that first shallow 0.5 degree angle, the throat transitions to a standard 1.5 degree angle until the full height of the rifling is reached.
Most 6.5 Grendel cartridges — loaded to an OAL of 2.260 — when pressed into a SAAMI chamber with a finger should fall out from gravity when the muzzle is tilted up. If a round does not fall out (some Hornady factory rounds do this), lightly thumping the breech end of the barrel on the table a bit should cause the cartridge to fall out due to inertia. This is OK.
What is NOT OK is if the bullet is truly jammed into the lands — even at 2.260 OAL — and will NOT EXTRACT without the bullet sticking in the rifling and being pulled out of the case or will NOT EXTRACT at all.
120 grain eldm oal issue - RobUrban - 01-11-2020
Here is my initial result with the 120 eldm at 2.2 oal with xbr
[video=youtube_share;mKVZ0q4iLXs]https://youtu.be/mKVZ0q4iLXs[/video]
120 grain eldm oal issue - muvef - 01-11-2020
I just checked my notes. The ogive touches the lands at 2.250" COAL w/ the 120 gr ELD in my group buy Green Mountain barrel. I have the 18" barrel.
I don't think 2.200" is an uncommon COAL for that bullet. From recollection, some of the Hornady Match ammo I purchased was around that length, but that was several years ago.
I would suggest double checking your measurements (though I bet you already have) just to be certain.
120 grain eldm oal issue - FLshooter - 01-12-2020
LRRPF52 Wrote:120gr ELD-M is meant for conventional freebore chambers.I like to price match at bass pro shop and all they carry is 123 grain Hornady ELDM. But I didn’t know that the 120 grain ELDM was not meant for Grendel.It’s a good thing to know ,thank you.
123gr A-MAX and ELD-M are meant for the Grendel.
123gr SMK and 123gr Scenar work really well in the Grendel's compound throat.
We used to see the same issue when people tried to load the 120gr A-MAX, depending on the chamber.
I've personally never ordered or purchased the 120gr Hornady target bullets for this reason, but I have mostly SAAMI chambers with the compound throat.
120 grain eldm oal issue - JCSC - 01-12-2020
Rob
What length tube are you getting those velocities?
Anyone know what the top end velocity should be for a 20? with a 120 projectile?
120 grain eldm oal issue - RobUrban - 01-12-2020
I am using a 20" barrel. I tested today again to confirm and go a little higher on the charges. 27.1 grain today 6 shot group right at an inch just under 2500fps. On 1-2 peices of brass their was a shiny spot from the ejector. I did not see this on the loads the other day. If I was going to stick with this load I would stay under the 27 grains in my barrel. Also tested 27.3 grain, ejector smear on them a little more noticable just over 2500 fps.
120 grain eldm oal issue - RobUrban - 01-12-2020
IMO any velocity in the 2400's is adequate to have an effective target round at all practical distances if they shoot well.
120 grain eldm oal issue - JCSC - 01-13-2020
Thanks. I ask because I am shooting the same load out of a 20?, but I am at 27.7 with my best shooting load. No chrono data and my brass seems fine. I get a little shine from the ejector occasionally, but I actually get that some here and there on all my Grendel rounds, including factory.
I did take a coil off my ejector spring, but I had a gas block adjustment come loose the same outing, so I can?t say if it helped.