Alex Arms short throat

[CowboyBart]

I loaded up some rounds for my new Alexandr Arms upper in 6.5 Grendel, and all of them ran into the lands. Why is the throat cut so short on these??
Rem 120gr PSP = 2.220" OAL
Sierra 120gr Game King = 2.225"
Nosler 120gr Bal Tip = 2.229"
Hornady 100gr SP = 2.223"

None of them would seat fully in the chamber. The spec I have on MAX OAL is 2.260".

Are the AA barrels throated only for VLD bullets and not hunting bullets?

I could seat them deeper (except for the rounds I put a "factory crimp" on) or I could buy a throat reamer and throat the barrel. But why should I have to do either??

 

[Drifter™]

2.260 is mag length, and not necessarily COL for all bullets. I think most or all of the bullets you listed often require COL's shorter than mag length.

What method are you using to determine max COL? Have you tried any factory loads, and if so, were there any problems?

If there is indeed a problem, AA has a reputation of making it right.

 

[CowboyBart]

I used 223 Rem OAL as a guide due to the same sized mag box.
Haven't tried factory ammo - haven't bought factory ammo in over 25 years (except berdan 7.62x39)

Haven't contacted AA yet - if their barrels are fluted for VLD bullets then it isn't their problem. I just want to shoot hunting bullets in mine.
Antelope season starts Sept 1, I could buy a throat reamer and throat the barrel faster than sending it to AA and getting it back.

 

[Drifter™]

Until you measure for COL's in your chamber with each bullet, it will be difficult to determine if a problem exists.

There are tools for this, or you can use a case with a slit case neck.

I believe the Grendel chamber was purposely designed to work with a wide variety of bullets, but not all can be seated to mag length due to the varying ogives.

For example, I load Nosler 120gr BT's to ~2.225, and Hornady 123gr SST's to ~2.230 (~0.012" off the lands). Both are good bullets for deer, and these COL's are what work in my particular Grendel chamber.

Are loaded rounds sticking in the chamber, or are you only seeing scratched bullets on extracted cartridges?


ETA- For long-range shots on antelope, you might also consider the 123gr A-max. A COL of ~2.245 to 2.250 works well in my barrel. The 120gr A-max is also accurate, but it has a lesser BC and must also be seated to a shorter COL due to its ogive design. Both the 123gr A-max and 123gr SST were specifically designed for the Grendel.

 

[mwilkins]

I have an AA chambered barrel on my Grendel. With factory Hornady Amax's, using the Hornady OAL gauge and Hornady comparator, the rounds are right up against the lands on a factory round. I have a box of Lapua Scenars that I am about to load up but just by looking at the profile of the round, I bet my seating depth is going to change. Get the two above tools to check and be sure.

 

[hlee]

You didn't measure the distance to the lands in the rifle you are loading for with the bullets you intend to load? Seems like a rookie mistake...

http://www.hornady.com/assets/files/catalog/2009/69-70_precision_gauges.pdf

 

[CowboyBart]

You didn't measure the distance to the lands in the rifle you are loading for with the bullets you intend to load? Seems like a rookie mistake...

I'm looking to see what bullet it likes. If I made a dummy for every bullet that I was going to try it would consume a lot of cases.

Yes, the bullets are into the lands - hard, as the round will not fully chamber. Upon extraction the rifling marks are on the bullet. Except the Nosler, upon extraction the case came out and the bullet stayed in the throat.

Rather than make ammo for my barrel and lose powder space, I would rather seat a round to fill the mag and throat the barrel to the round. It has worked in all the bolt guns that I have done like that.

 

[hlee]

The a chamber gauge in the link I posted uses a modified case (threaded on one end) to attach to the gauge. You put a bullet in case and put the gauge in the chamber. Then, you slowly push the rod through the gauge until the bullet touches the land. Use the set screw to lock down the gauge then extract the unit from the rifle. Measure the oal with a set of calipers (bullet specific) or use the Hornady ogive comparator to measure the ogive oal (bullet independent). It requires no cases and "may" scuff up a single bullet for the measurement. Of course, you could make dummy rounds and then pull the bullets to salvage the cases. It still sounds like a rookie mistake. "Measure once, cut twice." That's what I always say...

 

[mwilkins]

Without a comparator and an OAL gauge, it will be difficult to see exactly how far off you are on your seating depth. If someone doesn't beat me to it, I will take some Ogive measurements of a Hornady 123 Amax and a chamber measurement on my Grendel once I get home from the office and post it up.

Edit..... Here is verbiage from a post on another forum that I had made after getting my equipment in when I first started reloading.

On the Hornady's, a measurement of a 123 Amax with the Comparator, I got an OAL (base to Ogive) of 1.680 and a COAL (base to tip) of 2.242.

I then took the Grendel modified case with a 123 gr Scenar on the Hornady OAL tool and inserted it into my chamber. Pushed the projectile up against the lands, set the stop on the tool and then measured. Got the same OAL (base to Ogive of 1.680) but the COAL (base to tip) was shorter at 2.226.

So depending on the profile of the bullet, you can still have the pretty much the same base to tip measurement but the Ogive up against the lands. As in the above example. If I would have seated the Scenar to the same length of the Amax, I would have been into the lands.

 

[CowboyBart]

hlee, some day I'll be as good as you think you are.

 

[Drifter™]

Rather than make ammo for my barrel and lose powder space, I would rather seat a round to fill the mag and throat the barrel to the round.

Using appropriate powders can solve that. Seating the bullet out further to allow for more powder can be problematic if more powder creates excessive pressure. There are powders that will peak the pressure and performance before you run out of case capacity. What propellant(s) are you currently using with 120gr-class bullets?

 

[FCS]

I'm looking to see what bullet it likes. If I made a dummy for every bullet that I was going to try it would consume a lot of cases.

Yes, the bullets are into the lands - hard, as the round will not fully chamber. Upon extraction the rifling marks are on the bullet. Except the Nosler, upon extraction the case came out and the bullet stayed in the throat.

Rather than make ammo for my barrel and lose powder space, I would rather seat a round to fill the mag and throat the barrel to the round. It has worked in all the bolt guns that I have done like that.

Early AA bbls had plenty of room for the 8-10 ogive radius bullets. Later AA bbls have a much shorter freebore dimension and seem to be geared more for the 12-15 ogive radius bullets. 107 SMK, 123 A-max or similar is a better "fit" to chamber that AA has been putting in their barrels. More guys shooting the high BC bullets with 12-15 ogive radius OTM with 6.5 Grendel so they optimized chamber around the higher BC bullets.

All the bullets you listed are more in the 9-11 ogive radius, go to a 123 A-max / SMK / Scenar for a better fit to current chamber.

You aren't losing enough case capacity to worry about, 0.040" isn't going to gain you diddly in fps or get you to next accuracy node. Actually it would be 0.080" more so you had bullet out to just fit magazine and have some jump. Still won't gain you enough to worry about.

2520 will work well, though I'm not fond of 2520 in general as it is more temp sensitive then I like.
IMR 8208 is great choice, you'll be about 28 gr (give or take) when it comes in.

What bbl length and gas system length are you running?

 

[CowboyBart]

I'm using 2520 and TAC with the above loads. I was going to try H 335 and BLC-2 next. I can also use 4320, 4895, 4064 and I still have some AA2200 from the 90's.
I don't want to use SMK or A-max's for hunting. I want a reliable expanding bullet. Please save all the I killed... with a SMK or A-Max stories. I'm sure it has been done I just think the animal deserves more respect than possibly punching a hole slightly bigger than a 1/4" in it.

It is a 16" barrel with the direct gas system, it is not a piston system.

 

[LRRPF52]

Early AA bbls had plenty of room for the 8-10 ogive radius bullets. Later AA bbls have a much shorter freebore dimension and seem to be geared more for the 12-15 ogive radius bullets. 107 SMK, 123 A-max or similar is a better "fit" to chamber that AA has been putting in their barrels. More guys shooting the high BC bullets with 12-15 ogive radius OTM with 6.5 Grendel so they optimized chamber around the higher BC bullets.

All the bullets you listed are more in the 9-11 ogive radius, go to a 123 A-max / SMK / Scenar for a better fit to current chamber.

You aren't losing enough case capacity to worry about, 0.040" isn't going to gain you diddly in fps or get you to next accuracy node. Actually it would be 0.080" more so you had bullet out to just fit magazine and have some jump. Still won't gain you enough to worry about.

2520 will work well, though I'm not fond of 2520 in general as it is more temp sensitive then I like.
IMR 8208 is great choice, you'll be about 28 gr (give or take) when it comes in.

What bbl length and gas system length are you running?

AA has been using the same chamber for the Grendel throughout. Nothing seems out of the ordinary with the OP's seating depths and COL's to me, considering the ogives of those tangent ogive pills. A lot of tangent ogive pills have to be seated to 2.200" in the Grendel, whereas the magazine can't fit the maximum COL with secant ogive pills like the 129gr SST.

 

[Luky]

The a chamber gauge in the link I posted uses a modified case (threaded on one end) to attach to the gauge. You put a bullet in case and put the gauge in the chamber. Then, you slowly push the rod through the gauge until the bullet touches the land. Use the set screw to lock down the gauge then extract the unit from the rifle. Measure the oal with a set of calipers (bullet specific) or use the Hornady ogive comparator to measure the ogive oal (bullet independent). It requires no cases and "may" scuff up a single bullet for the measurement. Of course, you could make dummy rounds and then pull the bullets to salvage the cases. It still sounds like a rookie mistake. "Measure once, cut twice." That's what I always say...

+1

Cowboybart, don't get offended by this. It is really the way to do it scientifically and accurately without wasting a bunch of powder, bullets and brass. Spend a few bucks and get the right tools. This OAL ogive measurement is the first thing I do when starting a load development for a new bullet.

 

[Delta4-3]

I'm using 2520 and TAC with the above loads. I was going to try H 335 and BLC-2 next. I can also use 4320, 4895, 4064 and I still have some AA2200 from the 90's.
I don't want to use SMK or A-max's for hunting. I want a reliable expanding bullet. Please save all the I killed... with a SMK or A-Max stories. I'm sure it has been done I just think the animal deserves more respect than possibly punching a hole slightly bigger than a 1/4" in it.

It is a 16" barrel with the direct gas system, it is not a piston system.

What's wrong with the A-max? I've gotten sufficient expansion out of it.

 

[FCS]

AA has been using the same chamber for the Grendel throughout. Nothing seems out of the ordinary with the OP's seating depths and COL's to me, considering the ogives of those tangent ogive pills. A lot of tangent ogive pills have to be seated to 2.200" in the Grendel, whereas the magazine can't fit the maximum COL with secant ogive pills like the 129gr SST.

Will all due respect, bullshit that AA has used same chamber through out. I have one of the very early AA barrels and chamber sure as hell isn't anywhere close to the same as the bbls they have been sending out the last 4-5 years. Go blow smoke up somebody elses ass.

 

[FCS]

I'm using 2520 and TAC with the above loads. I was going to try H 335 and BLC-2 next. I can also use 4320, 4895, 4064 and I still have some AA2200 from the 90's.
I don't want to use SMK or A-max's for hunting. I want a reliable expanding bullet. Please save all the I killed... with a SMK or A-Max stories. I'm sure it has been done I just think the animal deserves more respect than possibly punching a hole slightly bigger than a 1/4" in it.

It is a 16" barrel with the direct gas system, it is not a piston system.

16" with a mid length gas system:

4895, 4320, 4064 will all be too slow in burn rate and you won't be able to get enough in the case.
H335, TAC, 2520 you'll be able to get enough in case but w/16" bbl and mid gas system....I'd heavy up buffer and use an adjustable gas block as port pressure and gas volume will both be higher with TAC and 2520 then if you were running a single base, extruded powder like 8208, N-135, N-133 or Benchmark.

2450ish is probably where the hunting bullets listed will shoot well for you. Might get reliable expansion but I doubt it.

Pull the rds you have loaded too long and rework brass so you can load to correct OAL for your chamber.

Good luck on your hunt.

 

[LRRPF52]

Will all due respect, bullshit that AA has used same chamber through out. I have one of the very early AA barrels and chamber sure as hell isn't anywhere close to the same as the bbls they have been sending out the last 4-5 years. Go blow smoke up somebody elses ass.

Nice to meet you too. So what movie are we seeing? You look a little fatter than your pics, but I'm cool with that. At least you have a nice uh....personality?

 

[bullseye13]

"Measure once, cut twice." That's what I always say...

I always thought it was "measure twice, cut once"?

How about "I cut it twice and its still too short"

 

[hlee]

I always thought it was "measure twice, cut once"?

How about "I cut it twice and its still too short"

That's where I was going. There isn't a "tongue in cheek" emoticon of which I am aware...

 

[bullseye13]

That's where I was going. There isn't a "tongue in cheek" emoticon of which I am aware...

Got it. Wasn't sure.fwiw I had a good laugh.

 

[FCS]

Nice to meet you too. So what movie are we seeing? You look a little fatter than your pics, but I'm cool with that. At least you have a nice uh....personality?

Pfft....again, you misstate the facts.

A lot fatter then pictures, a lot grayer then pictures and a lot older then pictures. What does any of that have to do with chamber dimensions for CowboyBart's chamber dimensions or how AA has changed chamber dimensions since 2004 or so?

Movie? With you? I'll pass for multiple reasons.