Short chamber?

[karmavore]

Hey guys,
Tried searching but didn’t see anything related to what I’m experiencing.
I’ve got a 24” Bartlein barrel on my AR chambered by a respected manufacturer.
I was going to load some 120g Hornady ELD-M projectiles, but noticed the bullets jammed the lands at the COL in my reloading book. (2.245”). I slotted a case, and measured my maximum length pretty consistently at 2.188. Is this anything to be concerned about?

[ricsmall]

If the 120 is same shape as the old 120 amax I THINK it requires a shorter coal. Not close to my book but you should be able to find it in some old AA data.

[muvef]

I think you should be concerned.

A 120 gr ELD match bullet should be touching the lands around 2.280" COAL give or take a few thousands. The 123 gr ELD match bullet should be around 2.320" also give or take a few thousands.

This is going off memory from when I looked into the chamber specs. My JSE barrel was supposed to have a SAAMI spec chamber and didn't. The bullet toched the lands with the 120 gr Sierra bullet at 2.400".

[cwlongshot]

I would be contacting the manufacturer.

That does not sound correct.

CW

[jhoyda]

I have the same problem using 120's with a Larue barrel.

The 120's are better suited for something like the Creedmoor. The 123's are a better ogive design for the Grendel.

ETA: You can definitely use the 120's in the Grendel. You will just need to seat them deeper.

[Randy99CL]

Yes, you have a short chamber.

SAAMI spec COAL for the Grendel is 2.135" MIN and 2.260" MAX.
I don't know why they list a minimum dimension?

As far as I'm concerned anytime any magazine-length factory loaded round hits the lands the chamber is too short.
I'm sure you know that a bullet jammed into the lands can create an overpressure situation and explosion.

I would think the maker would be happy to recut the chamber for you.

[VASCAR2]

The profile of the bullet nose is different on the 120 grain ELD-M/A-Max compared to the 123 grain ELD-M/A-Max. The 120 grain bullet needs to be seated deeper than the 123 grain. Hornady released the 123 grain A-Max/SST because the bullet profile better suited the 6.5 Grendel. The 120 grain bullet being seated deeper takes up valuable space in the small 6.5 Grendel case, less room for powder compared to the 123 grain bullet.

I have never reloaded the 120 grain ELD-M/A-Max so I can't advise the coal for any of my 6.5 Grendel barrels. I have a Friend who got a short chamber Brownell's barrel and he mostly shot reloads. His barrel shot so well he opted to keep it and just seats his bullets a little deeper.

You could possibley contact Hornady to get a specific cartridge overall length with the 120 grain ELD-M. Hornady has tested AR-15's with 6.5 Grendel barrels.

[karmavore]

thanks for the replies, guys. More research has confirmed the 120s are a different shape and require deeper seating than the more common 123s. I shot a few groups of them yesterday, mainly to see how they compare accuracy-wise to the 123s I have been shooting exclusively.
I don't think the chamber, per se, is short, but rather the throat or leade is.

[LRRPF52]

What kind of COL are you getting with 123gr SMK, Scenar, or LED-M?

The 120gr A-MAX and 120gr ELD-M aren't really meant for the Grendel, as they need to be seated deeper.

If your chamber allows them to be seated to 2.188", that sounds about right for a bullet with that ogive.

The 123gr ELD-M should load out to anywhere between 2.245" and 2.275" without jamming. If your chamber allows 2.245" at least with one of those 123gr, I wouldn't fret anymore over it.

[karmavore]

thanks LRRP.
I measured my max COAL (gently seated projectile in a slotted case) at 2.253 for the 123 ELD-M.
I had the box of 120s lying around and just wanted to see how they shot. Didn't have much luck with CFE223, but today had alot better success with some initial 8208XBR loads.
I got a string averaging 2551, ES 18, SD 8.3 with 28.2 grains that I'm gonna explore some more.

[LRRPF52]

One thing I do with a new barrel is test dummy and factory cartridges in it before it even goes near an upper receiver.

I expect the factory ammo that I use to chamber and drop free from the chamber without undue effort, preferably gravity.

If the cartridge get stuck, I know the throat it short and I measure it with colored projectile tips. It's been a long time since I've seen that from one particular set of barrels, but I still check.

What we don't want is factory ammo jamming the lands and spiking pressures, as well as requiring abnormal remedies to extract a live cartridge.

At 2.253" COL with the 123gr ELD-M, looks like you're fine.