Optimal Hunting bullet for 18in Grendels.

[XcountryRider]

Where does extractor marks appear in your ladder?

[LRRPF52]

Where does extractor marks appear in your ladder?

Good call. I think you mean ejector extrusion, where the plunger-style ejectors function within a longitudinal channel inside the bolt under spring tension. As the case forms into the chamber, excessive pressures use the same principle to force molten brass into the ejector channel, pushing the ejector itself deeper into that channel than bolt face depth.

These are often referred to as ejector swipes as well, but a swipe is when the extruded brass is now sheared during the unlocking stage of the cycle of operations, meaning the brass extrusion was significant enough to go so deep that the tolerances of even a self-loader's headspace were not enough to clear the deformity.

It happens before piercing the primers, after cratering. References are Chapter IV of the 6.5 Grendel Reloading Handbook, as well as Hornady's 8th Edition on page 70-71: Pressure Signs. I also left out case head expansion, which is included in both resources as the first measurable indicator on your brass. If you're looking at primers already, you're past the first 2 excessive pressure signs.

[XcountryRider]

I loaded up five rounds of 120tsx with 29gr of AA2520 and drove up the canyon by my house to take my son rabbit hunting and shot them threw the chrony just to see the velocity range and look at the primers. Stupid crony errored three times and only got two measurements. So not conclusive. The two shots had to big of difference in velocity. The primers looked good though.

[mseric]

The primers looked good though

The Grendel has a MAP of 52K psi. At what psi would you expect to see "pressure signs" in the Grendel Primers?

Remember that same small rifle primer is used in the 5.56 which operates at 62K MAP. How does the primer know to show you signs of pressure in the Grendel before it shows you signs of pressure in the 5.56?

[XcountryRider]

The Grendel has a MAP of 52K psi. At what psi would you expect to see "pressure signs" in the Grendel Primers?

Remember that same small rifle primer is used in the 5.56 which operates at 62K MAP. How does the primer know to show you signs of pressure in the Grendel before it shows you signs of pressure in the 5.56?

Ok any reason i would expect a 29gr of 2520 load for a 120gr bullet to be high? Thats in the safe zone for a 123gr Amax/SST load but not for a 120gr?

[woohoo]

The Grendel has a MAP of 52K psi. At what psi would you expect to see "pressure signs" in the Grendel Primers?

58-60k just like the rest...CCI 450s and 41s a little more. It will start with light cratering then grow to where you can catch a fingernail on the edge of the crater... time to back off 1/2gr and work down looking for accuracy. The G has a 52k psi MAP to protect the bolt. The case will handle 60 but not much more if you expect any life from them. If you have a bolt that can handle the higher pressure shown by the primers the case will. I've been running the 6.5 loads high around that 58-60k since 05. I broke 1 cheap 8620 7.62x39 bolt along time ago.
If you are new to reloading it probably isn't a good idea to push things much until you KNOW you know how to read signs of pressure. Setting up the resizing dies wrong can give false signs. Some match chambers are cut so close to the size of the brass to allow pushing the pressure the brass itself will not show many signs until it's too late. Sloppy chambers will show signs early. Pushing the shoulder back too far when resizing creating to much headspace will produce flat or blown primers, not from excess pressure but it allows the primers to back out and then get slammed into the bolt face when pressure builds high enough in the chamber.
I've been reloading since the late 70s and developing wildcats since 82. I still make mistakes, the last one sent pieces of brass through my lip and into my face. That turned out to be a 1gr overcharge due to a sticking powder measure. When you're running on the edge it doesn't take much to cross the line.
XC, increase in small steps and watch what others have done on this site. Don't stray to far from the masses...yet.

[XcountryRider]

58-60k just like the rest...CCI 450s and 41s a little more. It will start with light cratering then grow to where you can catch a fingernail on the edge of the crater... time to back off 1/2gr and work down looking for accuracy. The G has a 52k psi MAP to protect the bolt. The case will handle 60 but not much more if you expect any life from them. If you have a bolt that can handle the higher pressure shown by the primers the case will. I've been running the 6.5 loads high around that 58-60k since 05. I broke 1 cheap 8620 7.62x39 bolt along time ago.
If you are new to reloading it probably isn't a good idea to push things much until you KNOW you know how to read signs of pressure. Setting up the resizing dies wrong can give false signs. Some match chambers are cut so close to the size of the brass to allow pushing the pressure the brass itself will not show many signs until it's too late. Sloppy chambers will show signs early. Pushing the shoulder back too far when resizing creating to much headspace will produce flat or blown primers, not from excess pressure but it allows the primers to back out and then get slammed into the bolt face when pressure builds high enough in the chamber.
I've been reloading since the late 70s and developing wildcats since 82. I still make mistakes, the last one sent pieces of brass through my lip and into my face. That turned out to be a 1gr overcharge due to a sticking powder measure. When you're running on the edge it doesn't take much to cross the line.
XC, increase in small steps and watch what others have done on this site. Don't stray to far from the masses...yet.

Whats your opinion of my 5R rifling theory giving more benefit to a longer 6.5mm pill?

[woohoo]

Whats your opinion of my 5R rifling theory giving more benefit to a longer 6.5mm pill?

If the bore area is larger/has smaller lands than a typical 6 groove 50:50 ratio barrel it should have less engraving force and pressure should dissipate quicker. Testing a square land side by side with low L-G ratio 5R barrels we have seen as much as 100fps difference, most of the time 60-80fps.

[LRRPF52]

Ok any reason i would expect a 29gr of 2520 load for a 120gr bullet to be high? Thats in the safe zone for a 123gr Amax/SST load but not for a 120gr?

You're comparing two totally different types of projectiles that have substantially different hardness. The 120gr TSX will spike fast on you in the start pressure area, as well as its bearing surface and material hardness. This is because it is a solid projectile. Notice in all your industry reloading data that the 120gr TSX clocks in significantly lower velocities than projectiles like the 123gr Scenar or 123gr SMK?

Bullet weight is only one factor in choosing a load range to work within. Bearing surface and jacket/alloy construction play equally-important roles. You cannot use data from one for the other as if they were the same, even with the 120 TSX being marginally lighter.

You need to work up a load for it using a pressure ladder and your chronograph. Any reloading manual will tell you that if you switch any component in your recipe, work up using starting loads.

[Drifter]

And that 120gr TSX appears to have a forward ogive, so it likely needs to be seated to a shorter COL than mag length.

Check COL for each bullet in your chamber, then start low and work up on charge weight.

[mseric]

58-60k just like the rest...CCI 450s and 41s a little more. It will start with light cratering then grow to where you can catch a fingernail on the edge of the crater... time to back off 1/2gr and work down looking for accuracy. The G has a 52k psi MAP to protect the bolt. The case will handle 60 but not much more if you expect any life from them. If you have a bolt that can handle the higher pressure shown by the primers the case will. I've been running the 6.5 loads high around that 58-60k

I'm curious, How do you know you are loading to 58-60K psi? Do you have a Pressure Trace system, or are you guessing?

From handloader Magazine.

Gen.
Julian Hatcher warned against it
way back in 1947, when his book
Hatcher’s Notebook was first published.
(This is one of the basic
texts of rifles and ammunition,
even today, and every serious
shooter should own a copy.)
Early in the chapter on headspace,
Hatcher discusses wildcat
cartridges: “Usually the originator
of one of these cartridges had
no facilities for taking pressures,
and depended entirely on the notoriously
unreliable [emphasis
mine] method of judging pressures
by the appearance of the
primer.” But myths are much
harder to kill than create, so
some handloaders continue to
believe they can divine pressure
from a primer.

[woohoo]

I'm curious, How do you know you are loading to 58-60K psi? Do you have a Pressure Trace system, or are you guessing?

From handloader Magazine.

Gen.
Julian Hatcher warned against it
way back in 1947, when his book
Hatcher’s Notebook was first published.
(This is one of the basic
texts of rifles and ammunition,
even today, and every serious
shooter should own a copy.)
Early in the chapter on headspace,
Hatcher discusses wildcat
cartridges: “Usually the originator
of one of these cartridges had
no facilities for taking pressures,
and depended entirely on the notoriously
unreliable [emphasis
mine] method of judging pressures
by the appearance of the
primer.” But myths are much
harder to kill than create, so
some handloaders continue to
believe they can divine pressure
from a primer.

We have used a pressure trace but that only tells the difference in stretch of the barrel material and produces a calculated pressure between loads shot in the same barrel. Without a known pressure charge in the exact barrel to calibrate it is useless.
Brass flow can be found by taking case sections to a lab and subjecting it to increasing pressure. Brass can not be tempered to make it harder, it can only be stuck/forged to an extent. Most brass near the rim away from the annealed area of the neck will flow at apx the same pressure. Brass flow shows around 65k if a .100 hole similar to the size of the ejector is used.
In short yes, after years of knowing exactly what a 70k PSI proof load does to brass and primers and what the brass looks like at 60 and 65k psi lab tests I can get pretty close by looking at primers since I use the same type. When a CCI 41 flows into a .065 firing pin hole I know I'm over 60k.
Now if you want to use primers as your sign of when to stop increasing the charge like most do then it doesn't matter what the type is. When the primer regardless of the type craters heavily it's beginning to fail. If you don't want to damage the firing pin or bolt stop there. A Federal match primer will crater long before a CCI41 will. If you want more velocity and can get the accuracy you seek from a 41 or 450 use those instead of a FGGM primer. Don't use a 29gr XXX charge with a CCI 41 and then swap to a FGGM, or you'll likely get a pierced primer. Always work loads up with the same components. Primers will crater and flatten long before a case ruptures unless someone cranks the size die down too far and creates too much headspace or the chamber is much larger than the case dia.
Lapua brass is thin to increase case capacity, when you approach 65k with Lapua the cases will come out of the chamber looking like a belted magnum. That is a sign you are way over pressure and in danger of rupturing a case. Piercing or flattening a primer wont hurt you, rupturing a case will.
When I say only experienced loaders should push the loads I don't mean someone that has loaded a million rounds of pistol ammo to a book load I mean someone that really understands how things work and what certain signs mean. Reading primers will tell you when the primers are about to fail. When you get to the point the hardest primer (CCI41) is about to fail don't push your luck and have the brass fail too because that is what will hurt you.

[XcountryRider]

Here's a simple method to check COL (courtesy of rasp65):

http://www.65grendel.com/forum/showthrea...-amp-crimp

As for two barrels, are they both from the same maker, using the same reamer?

Stay clear of the magwell if you have any uncertainty when shooting those same loads.


If you think I'm attempting to scare you, well... you're right.

When something doesn't add up, it's worth investigating further, especially when it comes to firearms.

A fast barrel is good only if it's safe.

I want your barrel to be fast. And safe. And I want you to be around to tell about it.

Thanks for the tip i made the gauge and tested both rifles. My 18in measured at 2.268 and my 24in measured at 2.264. My 120gr Barnes TSX's are loaded to 2.24 so i don't think i have an issue with jamming the lands. How much should i load under the COL measurement?

[LRRPF52]

Load to a reliable COL length that will feed from your mags. Did you go back down to a starting load and work this bullet/powder up yet?

[XcountryRider]

Load to a reliable COL length that will feed from your mags. Did you go back down to a starting load and work this bullet/powder up yet?

I'm going to be shooting this Saturday what do you think a good starting load should be.

[LRRPF52]

26.5grs or AA2520 should be a safe starting load, but book values are showing 24.9gr for the Hornady 120gr GMX solid as a low starting load. I personally would want enough of a pressure curve saturated with data points so I could see what was going on with the load and my chamber. I would run 3 batches of pressure/accuracy ladders, starting with 26.5grs at 2.240 COL.

26.5
26.8
27.1
27.4
27.7
28.0
28.3
28.6
28.9
29.1 (Hornady lists this as the max load with the 120gr GMX solid)

Watch the chrono as your #1 focus for erratic velocity changes outside of the predictable pressure curve. You should see changes with each .3grs at ~25-40fps. Once you see significant increases, or even an unexplained major drop, record that, and measure case head dimensions above the extractor groove. If you see any major flattening of the primer, or cratering, you know pressure is way too high. When you run the other 2 batches, you should start to see some consistent trends.

You can also do round robin targets at distance to find the accuracy nodes without having to color bullets. You basically have an aiming point for each charge, and the batches will add up at each point until there are 3 holes per aiming point. You can mark the aiming points with the charge weight in big letters above, or assign each charge weight a number and annotate that next to your load data.

[XcountryRider]

Thanks didn't think of checking the GMX data. I already went to 30.2gr so not going to go down that far will probably do something like this.

28.0
28.3
28.6
28.9
29.1
29.3

[LRRPF52]

I don't think 6 charges is enough to generate a good idea of how it builds pressure, and we still don't know if 28.0gr is already max for your gun.

[joker31]

I really think you need to specify what your hunting. For coyotes, ground hogs/varmints and head shots on feral critters I think the 100grain Nosler BT would work. For deer, Antelope and large feral hogs I would prefer 100/120 Barnes TTSX, 100 grain Nosler partition, 120 grain Sierra Pro Hunter, Nosler 120 BT Hunting, Hornady 123 or 129 grain SST and 125 grain Nosler Partition. The higher BC of the SST's would help on longer shots compared the partition and pro hunter shorter design bullets.

Not to pick on you VASCAR but how come the same people who say 100gr bullets arent enough for deer in 6.5G are the same people who would recommend a 100gr bullet in a 243? I really dont understand this, I also dont understand this with other calibers either I have hunted in the past with a 300 whisper with 120gr bullets and have clocked them at 1100fps out of 10.5" barrel and killed deer dead right there not a flinch. Then people who say its a good load (300) also say the 357 magnum moving at the same speed from a 6" barrel with a heavier bullet isn't a good load for deer. I just wonder. By the way, both kill deer equally well. I am interested in the lighter loads for Grendel, think they are very useful.

Again, VASCAR, please dont take offense, I am only using the situation as an example, I dont mean to pick a fight in any way, shape or form.

[JASmith]

...how come the same people who say 100gr bullets arent enough for deer in 6.5G are the same people who would recommend a 100gr bullet in a 243? I really dont understand this, I also dont understand this with other calibers either...

Good observations!

Let's start with the 'why' -- Way too many of us, including yours truly, understand penetration mechanics of solid projectiles where sectional density and velocity are important factors in determining penetration depth. This understanding incorrectly tells us that the 100 gr .243 bullet should penetrate deeper than a 100 gr 6.5 mm bullet fired from the Grendel.

Some of us have a rudimentary understanding of the mechanics of eroding projectiles, where the sectional density of the remaining projectile helps determine the next increment of penetration. Very few have looked at the case where a projectile partly erodes in a soft media and then holds a rather consistent shape for the remainder of the event.

Expanding bullets fit this last description when they impact game animals at within their design velocity range. Think of it this way -- the bullet transforms from a sleek aerodynamic projectile into a ball-like object within a few inches of hitting the skin. After that, the sectional density and residual velocity of that object defines the remainder of the event. This phenomena invalidates our model that views the sectional density of the original bullet shape as the principal factor in penetration.

In short, it can be shown that a 100 gr .243, .264, .277, etc. bullet have roughly the same effectiveness on game provided they are built to similar standards. This last bit also confuses us in the shooting public because a 100 grain .243 bullet is treated and almost always designed as a medium game bullet. On the other hand, a 100 gr .30 caliber bullet is almost always designed as a varmint or plinking bullet. These two bullets behave quite differently on impact.

These thoughts are expanded along with discussions of the underlying test data in the paper "Ideal Bullet Weight."

You will also see that that the right choice of bullet weight and design can give the Grendel a lot of capability for almost all North American big game in addition to deer and hogs.