Bullet jump

[JCSC]

Is it common to find that loading mag length in the AR is too long.

Measurements I took tonight show that with the hornady 120 gr eld, I am at the lands with a 2.215 oal.
I couldn?t check factory 123 gr ammo, but it has to be close.
6.5 Grendel and a Odin works barrel that is going back for review by them.

Does this caliber like a certain amount of jump?

[FRB6.5]

~2.2540" COAL is what Hornady Black 123gr ELD-M measures for me. That sounds like a short throat.

[Lemonaid]

Here are my notes on bullet to lands for BCA Ar and Ruger American Predator Bolt action.
Some of the shorter bullets like the Speer 90 tnt could be seated out to the lands but would not not be in the case neck enough.
I have a notion that one reason the Sierra 120 MK and Sierra 120 Pro Hunter are accurate in both my Grendels is that you can get both close to the lands and fit it in the mag AND be at least one caliber deep in the neck.

Grendel Bullet OAL to touch the lands

BCA----------------------------------------------------------------RAP

Hornady 95 V-Max----------- 2.267---------------------------2.286

Hornady 123 Eld Match------2.298---------------------------2.330

Sierra 142 MK---------------------------------------------------2.367

Sierra 130 GC------------------2.375?-------------------------2.413

Sierra 120 MK------------------2.330--------------------------2.292

Sierra 120 Pro Hunter--------2.280---------------------------2.261

Sierra 107 MK------------------2.340---------------------------2.364

Speer 140 Hot cor ------beyond mag len--------------------2.303

Speer 90 TNT------------------2.290 (fully in neck 2.190)--2.290

Speer 120 gold dot--------beyond 2.312---------------------2.369

Match Monster 100 gn hpbt--2.150-----------------beyond 2.320

Match Monster 123 gn beyond 2.300-------------------------2.294

[JASmith]

Bill Alexander has indicated that “a light kiss” is about right. That is true for a throat conforming to the SAAMI specification.

That said, many of us find that the 0.5 degree SAAMI throat is very tolerant of mild jumps too.

Regardless of whether your throat is SAAMI-compliant, or has the 1.5 degree throat favored by some reamer makers, the best advice is to run some seating depth ladders to get close to the best accuracy for your rifle.

[FRB6.5]

JA would "a light kiss" be considered .010 or .001 into the lands or something else?

[FLshooter]

Don’t know how you came up w/2.215” OAL.The Hornady manual tells you to seat 123g ELDM @ 2.250” col.
My measurement in my Bartlein was 2.318” OAL.Craddock,who built the barrel for me told me to start with a 1mm jump(40 thousandths.
So,I started seating my Hornady 123 ELDM @ 2.280” OAL and it shoots great.

[JCSC]

I used the hornady 120 gr eld, so a little different from the 123.

I used my hornady gauge and pushed the bullet out to the lands in my barrel.

The I don?t have the base to Ogive in front of me, but the OAL is 2.215?

[JCSC]

I also measured new factory Black at 2.250?

[FLshooter]

I also measured new factory Black at 2.250?

I don’t have any Hornady 6.5 Grendel factory ammo on hand.But,2.250” sounds right.It’s what they tell you to seat your bullet at.

[Klem]

JC,

I have the impression that most guy's chambers are longer than the mag length.

Never used the 120ELD but the 123ELD touches my lands at 2.393. For me, with all bullets, the mag is the limiting factor and with that comes compulsory long jumps (so be careful what you wish for). I'm happy with the accuracy however.

[A5BLASTER]

I also measured new factory Black at 2.250?

Pull a 123 eld-m from a factory case and use it in your hornady tool and see what the length is to contact.

That will tell you right quick if your throat is short.

[JASmith]

JA would "a light kiss" be considered .010 or .001 into the lands or something else?

The discussions showed images of bullets with very light engraving marks seen. One first coats the shoulder with a permanent marker, chambers a dummy round, and then a little bit of the mark is removed in a way that is consistent with the lands when the ?light kiss? is encountered.

Acrual engrainvg into the copper is more than a light kiss.

[FRB6.5]

The discussions showed images of bullets with very light engraving marks seen. One first coats the shoulder with a permanent marker, chambers a dummy round, and then a little bit of the mark is removed in a way that is consistent with the lands when the ?light kiss? is encountered.

Acrual engrainvg into the copper is more than a light kiss.

Thanks for the reply, guessing closer to the lower measurement then.

[greaseywater]

I had the same issue with the 120 ELDM. Loaded to 2.215 the rounds would just stick in the chamber. They would fall out with a light tap of the barrel on the bench.

I also had 123 ELDMs and could load them much closer to mag length (I don't remember the exact value).

I used the Hornady gauge to measure the bullets themselves.

123 ELD M - 1.230 bullet OAL, 0.655 bullet base to ogive

120 ELD M - 1.200 bullet OAL, 0.671 bullet base to ogive.

So, if seated to the same cartridge overall length the 120 ogive would be ~ 0.045 closer to the lands. Which matched up well to what I had seen.

Seating the 120 at 2.200 kept it out of the lands.

[FRB6.5]

Excellent post and observation greaseywater!