100ELD-M 8208 XBR Has me confused

[CxAgent]

When reloading I typicall use a number of published resources, quick load, Gordens reloading tool and the Hogden Reloading Data Center to verify load pressures will be safe.

Today I loaded some 100GR ELD-M with IMR 8208XBR. Reloading data center shows max load at 30.8 grains. I loaded up 5 rounds each 30.2, 30.4, 30.6, and 30.8. Gordens reloading tool and quickload both show these loads slightly over the 52k with velocities in the 2614 to 2682. My velocities ranged from 2730 to a high of 2800.

So here is what has me perplexed. I have loaded a bunch of different bullets in the 120 - 123 classs and some 107's and in each instance velocities were well below the published or calculated data. AN adjustment to Ba and seems to bring velocity inline with the measures and then I can guage pressures.

Any ideas why this particular load appears to run hotter where all other loads are typically below what quickload / Gordons / Hogden predict.

30.2 2740 Avg fps
30.4 2759 Avg fps
30.6 2768 Avg fps Minor ejector marks slight flattening needs to be angled just right to see the marks
30.8 2796 Avg fps Minor ejector marks slight flattening needs to be angled just right to see the marks


Case: Hornady once fired and resized
Primer: CCI #41
Power: 8208XBR 30.2, 30.4, 30.6, and 30.8
Bullet 100GR ELD-M
COAL:2.20 CBTO 1.671
Barrel Faxom 16" Gunner series

Thank in advance

[biodsl]

Don't know that this is part of the issue but I see that Hornady loads to an OAL of 2.245. Increasing you length might decrease pressure and velocity.

[Oso Polaris]

Along the line of above ^^^

Things that could be affect the velocity:
1) Heavy crimp on case or excessive neck tension
2) Bullet Seating Depth
- If bullet seated deep then might be causing a compressed loads.
- Where is the base of the bullet compared to the base of the neck?
- When you shake the case is there any empty space (hear the powder shaking loose)?
- It's a shorter bullet.... is the bullet's ogive set inside/below the mouth of case on your reloads? ... edge of mouth rolls inward effectively forming crimp in front of the bullet's ogive
3) Chamber of Rifle
- Did you determine your chamber length using OAL Gage to confirm max load length (OAL or CBTO) for this specific bullet?
- Is the chamber's throated short... and as result your reloads were jam fitting?

Food for Thought

[Klem]

Agent,

I think it is because Hodgdon's has got the 100NBT wrong.

If you enter Hodgdon's 100NBT data into Quickload (QL) you get the same velocity but a very different peak pressure. Hodgdons lists only 47K lbs (which is suspiciously low for a max load) while QL lists 64K lbs for the same load. When you are dealing with compressed loads of 8208 it makes Hodgdon's mild 47K pressure even more suspicious. Compressed 8208 in Grendel is not a tame load. You say you're getting ejector swipes and flattened primers at 30.8gns - I would believe that what you see with your own eyes over tables and predictions any day. In Grendel, once you see the typical signs of pressure you know you are over peak pressure limits.

I would not load more than 30gns 8208 with the 100ELD-M at 2.20"OAL. At this it is exactly 100% case full - so not compressed. QL predicts about 52K lbs which is the SAAMI peak pressure limit. QL is conservative so this would be a reasonable maximum.

Quickload lists your 30.8gn 100ELD-M load at 2.20"OAL as 106.8% compressed. That is a lot of compression and be aware that compressing a relatively fast powder like 8208 lifts the pressure quickly.

Your Hornady once-fired cases will have a different internal volume to QL's default and this affects pressure. I would fill a couple of them with water, weigh the water, and enter the exact weight into QL for a more precise prediction.

Be also aware that Hodgdon's tables are for the 100Nosler BT, not the 100ELD-M. The NBT is flat based and the ELD is boat tail. They displace different amounts of space in the case for the same OAL, and this affects pressure.

Like I said, something is not right with Hodgdon's predicted peak pressure, and compressing 8208 is unforgiving. Please be careful with this one.

I have used the 100ELD with best results at 29.6gn of 8208, 58mm OAL using Lapua cases. My barrel does not like them and I get better results using the 120ELD's with H4895.

[CxAgent]

Thank you all for the replies.
I expand the necks using a 21st expander to .262, cases were trimmed to 1.512, water capacity was between 36.35 and 36.5 grains. I do have the AOL tool and I can measure distance to lands. Fired cases are giving me the same measurements as my AR stoner barrel and PF chambered barrel so I can speculate the chamber is close to the others if not the same.

I am going to drop down to the next node as predicted by GRT which is right around where Klem mentioned 29.68.


Certainly still a little baffled why quickload and GRT are showing slower velocities than measured. Both reloading tools typically show veleocities above actual measured with 8208XBR.

Anyway, I figure I came close to a catastrophic failure of the case as the 30.8 load cases measured about .003 longer then the rest of the cases.

[Klem]

Agent,

I get 2,640fps out of an 19" barrel with 29.6/8208 at 57mm OAL. The reason the OAL is shorter than normal is because with the boat tail and short length there is not a lot of shank in contact with the neck so you have to push it in for a better grip. At 57mm there is only 4mm of shank contact so any preferred jump-to-lands takes a back seat. You get whatever jump and thankful for it.

If by 'measured with 8208'? you mean you graphed the load/velocity from your workup and extrapolated that for heavier loads you are not taking into account the vicious increase as soon as you compress 8208. At 30gns the load/velocity curve steepens and heads for the sky. At 106% compressed you have a hand grenade.

[VASCAR2]

[CxAgent]

Klem,
I meant the measured velocities are generally less than what quickload predicts for velocity when I use 8208XBR. Quickload is pretty spot on with AR comp and Varget.

I'll be backing the load down to approx 29.6 and get some velocites to see how that compares and make adjustments from there.

Thanks again to all who replied.

[Old Bob]

Oh great! I loaded a ladder of 8208 & 127gr Barnes LRX bullets awhile back but haven't had a chance to shoot 'em yet. The ladder starts at 25grs & ends at 27grs. I went back & looked at my manuals & data sheets printed from the internet & can't remember why I chose those loads for that powder/bullet combo. Looking now at all the info I have & the comments from this discussion, I may have too hot loads at the 26.5gr & 27gr steps in the ladder. Those two loads are definitely compressed. COAL is 2.26" & CBTO is 1.72". The brass is once fired Hornady.

Revelations as they are, 8208 was probably a poor choice for the 127 LRX & my AR. Would that combo be a better choice for my mini Howa? I didn't have that rifle yet when I cooked up those loads.

[mdram]

Oh great! I loaded a ladder of 8208 & 127gr Barnes LRX bullets awhile back but haven't had a chance to shoot 'em yet. The ladder starts at 25grs & ends at 27grs. I went back & looked at my manuals & data sheets printed from the internet & can't remember why I chose those loads for that powder/bullet combo. Looking now at all the info I have & the comments from this discussion, I may have too hot loads at the 26.5gr & 27gr steps in the ladder. Those two loads are definitely compressed. COAL is 2.26" & CBTO is 1.72". The brass is once fired Hornady.

Revelations as they are, 8208 was probably a poor choice for the 127 LRX & my AR. Would that combo be a better choice for my mini Howa? I didn't have that rifle yet when I cooked up those loads.

27.5 is my load under 123elds, i tested up to 28.2 with no pressure signs. it will, as always, depend on your firearm

[jasper2408]

One other thing to take into consideration here is the Nosler manual 100gr bullet data is using a Nosler case, which shows 33.0gr of water, and the Hodgdon data is using a Lapua case, which I get 35.9gr of water, and the OP is using a Hornady case, which I get 35.5-.6gr of water for both Hornady and Starline and is what Sierra is using. I have not tested the Nosler cases but I have tested the rest of them to see what grains of water would be in a FL resized case.

[Klem]

Jasper,

That is interesting, thanks for sharing.
My sized Lapua's measure 35.92gr of water. A new/unfired Lapua measures 35.13. My chamber is longer than SAAMI so they stretch on the first firing and even after sizing hold a fair amount of water.

[VASCAR2]

I never noticed which case Nosler used in their data, that might explain why their data always seemed conservative. Thanks Jasper for the info.

[Old Bob]

I never noticed which case Nosler used in their data, that might explain why their data always seemed conservative. Thanks Jasper for the info.

Nosler makes their own 6.5 Grendel brass so their data is home brewed with their own components. Only primers & powder are from another source. Looking at their data it's kinda odd that the cases hold different water weights depending on five different bullet weight ranges. Cases for 90gr bullets hold 32grs H2O; 100gr bullets, 33grs H2O; 120 bullets, 29grs H2O; 123/125gr bullets, 30grs H2O; 129/130gr bullets, 28.7grs H2O...

Is that water weight after the bullet is seated?

[Klem]

Is that water weight after the bullet is seated?

It is case capacity without a seated bullet. Measured by filling the empty case up with water to the top.

What might give different weights is different brands, case lengths, sizes (fire-formed from different chambers), whether the full case has a [water] meniscus or not, and user error when weighing.