Im getting shoulder dents after firing. Im shooting an AR-10 308 Win using hornady 160gr FTX with IMR 4320 33.9gr seating at .035 under ogive.????

[jhites]

Im getting shoulder dents after firing. Im shooting an AR-10 308 Win using hornady 160gr FTX with IMR 4320 33.9gr seating at .035 under ogive.????

 

[Zen Archery]

Pics? Sure it's not happening from the deflector?

 

[Old Rooster]

If you have a borescope you can make sure the chamber does not have a problem.
Ar4life on this site is the ar guru.He will be around soon.

 

[Trnelson]

Several possibilities with an AR style rifle. As previously mentioned the most likely suspect for a dented fired case would be the deflector. Unload an unfired case and examine it closely. If it is a chamber related issue you should find marking on the case. Auto loading rifles can be rough on brass.

 

[philipbrousseau]

Does your load create enough pressure that necks are preventing gas blow by? Overgassed possibly? I'm no ar expert by any means, just throwing this out there. Had a friend's nemo 300 win mag expanding primer pockets and primers falling out. I thought it was excessive pressure but turned out that just needed the gas setting turned down one notch.

 

[fmuguira]

Load seems real light just glancing at your charge weight. Not an AR guy so don't know if light load can cause case to dwell longer in chamber and somehow dent it?

Does a factory pressure round dent the case the same way?

 

[xsn10s]

Load seems real light just glancing at your charge weight. Not an AR guy so don't know if light load can cause case to dwell longer in chamber and somehow dent it?

Does a factory pressure round dent the case the same way?

I was thinking the same thing.

 

[xsn10s]

I just checked Hodgdon's load data and that's like 10 grains lower than their starting load. And IMR 4320 isn't listed as one of their powders for service rifle. My best guess is you're getting a double spike that's causing the shoulders to collapse and possible getting the bullet momentarily stuck in your bore. I'd change powders. And if you're looking to make reduced loads follow Hodgdons guidelines with H4895.

 

[xsn10s]

33.9gr seating at .035 under ogive.

Is you're ogive .035 below the case neck?

 

[M1A1ABRAMS]

I just checked Hodgdon's load data and that's like 10 grains lower than their starting load. And IMR 4320 isn't listed as one of their powders for service rifle. My best guess is you're getting a double spike that's causing the shoulders to collapse and possible getting the bullet momentarily stuck in your bore. I'd change powders. And if you're looking to make reduced loads follow Hodgdons guidelines with H4895.

49th Edition Lyman manual list IMR 4320. But I do believe you're right he's below charge weight for the powder being used.
Edit Hornady 11th Edition list 33.9 as start for 165-168 gr. Not in service rifle though. I am new to reloading myself. And is there much of a difference between the two in powder usage ? Other than possibly the dwell time. And needing a thicker cup primer. I would think increasing his charge slightly should solve his issue ?

 

[budlight]

Im getting shoulder dents after firing. Im shooting an AR-10 308 Win using hornady 160gr FTX with IMR 4320 33.9gr seating at .035 under ogive.????

First off where did you come up up with that load? 4320 is just in between varget and 748 on the burn rate chart.

Then you have to determine if your AR shoots full powered factory rounds or if it's a phoney service rifle loads only!

So I looked up 308 service rifle and standard 308 win in an old IMR reloading manual for IMR 4320 and it had 43.2 grains for a 168 with only 44,000 CUP. The 60,000 psi 308 win got 46 grains.

You are loading only 160 gr. so you at 33.9 are 10 grains under service rifle. Your dents are from poor ejection

 

[Bucklowery]

Put some mole skin or Velcro on your deflector if you love the load. Adjust gas block but your brass is hitting the deflector. Video it while you shoot, you will see.

Thanks

Buck

 

[ARlife4me]

if poor ejection (as in bolt not traveling back far enough to pick up next round) it won't hit the deflector (if so it won't have enough energy to do so).

though it might seem a low charge weight, pressure can come by more bearing surface and deeper set projectiles. not knowing (as in me) the coal of your ammo (and not ever used the ftx in 30cal) it's difficult to say what the issue really is! diagnosing over the www is and can be difficult to fix?

as mentioned in above post...........pics

chamber is most likely fine.
throat length can play a part in pressures also.

too much to list on possibilities

 

[budlight]

Im getting shoulder dents after firing. Im shooting an AR-10 308 Win using hornady 160gr FTX with IMR 4320 33.9gr seating at .035 under ogive.????

#1 You are 10 grains under on the powder.

#2 Seating using the ogive as a guide is NOT good reloading practises. COL is. Generally 308 win falls between 2.750 and 2.800. But look up the SAAMI specs to find out the min and max

The overall length (OAL) of an ammunition cartridge is a measurement from the base of the brass shell casing to the tip of the bullet, seated into the brass casing. Cartridge overall length, or "COL", is important to safe functioning of reloads in firearms.