Hornady 123 sst concerns

[snell]

Well, I've tried reloading the 123 SST with little success. I saw a good price on a box of Hornady 123 SST ammo so I decided to give some factory a try. A single ten shot string fired 5 shots to a target at 100 yards. Each target produced two distinct groups. The pic below is representative.

target.jpg

Each of the 5 shots groups produced three pierced primers and two cratered primers.

pierced2.jpg

cratered2.jpg

The chrono results were:

High: 2556
Low: 1491
Aver 2527
Spread 64.73
SD 19.07

This was out of an 18" Hardened arms barrel.

This is really troubling, has anyone else had problems with Hornady ammo?

[A5BLASTER]

You have a chamber or out of spec bolt issue. I wouldn't shoot it anymore till you can get it checked out.

[snell]

This has not occurred with any of my hand loads..

[Bill257]

1,000 FPS variation is far from normal. With the average only 29 FPS slower than the fastest velocity there can't be a round that only clocked 1,497.

The pressure signs on primers is a whole issue on its own. Did the bolt come with the barrel? Even if it did, checking that bolt depth is compatible with the chamber may be a first step. As suggested, this needs to be addressed before firing this rifle again.

Good luck

[snell]

duh!! a typo on the low reading.. it should have been 2491. The barrel and bolt came together. It was a complete upper from Hardened Arms who are now out of business

[Mitdr774]

I would suggest having the rifle checked for proper headspace and see if the throat is short. Out of a 22" and 24" bolt rifles I only clock around 2500 FPS with the factory Hornady ammunition if my memory is correct. I have never had any of my factory load Hornady 6.5 Grendel show any signs of pressure.

[Bill257]

A trip to a gunsmith with a set of go - no go gauges may be a good idea.

I have shot a bunch of Hornady loaded ammo and not seen anything similar.... Glad to hear they are not sending out ammo with 1,000 FPS variance; that would be a bad day.

[Lemonaid]

A quick test would be to measure the overall length of a factory round. Get a black marker (sharpy) and color the entire bullet, neck and shoulder.
Chamber the round then eject it without firing (all safety measures taken).
Recheck the overall length and examine the bullet and case to see if the lands have engraved or the OAL has decreased or other weirdness.

Bad factory ammo dose happen, there are recalls from time to time.

[VASCAR2]

I suggest you measure your bolt length from the tail to the face. To use a standard length firing pin the bolt needs to measure 2.810” with a bolt face depth of .136. Usual tolerance is +or- .001 for bolts. There have been issues where firing pin protrusion is out of spec. The spec for AR-15 firing pin protrusion is .028” minimum and maximum .036” (.008” tolerance). The spec I’ve found for AR-15 firing pin length is 3.279”.

Several 6.5 Grendel Manufacturers have sold bolts with an overall length of 2.800” and .136” bolt face depth. This shorter bolt needs a shorter firing pin. A shorter bolt needs a firing pin length of 3.269”. The difference in your measured bolt and firing pin length need to be within the .008” tolerance for your bolt/firing pin protrusion to be in spec. There have been reports of out of spec firing pins supplied with the 2.800” length bolts.

When AA developed the 6.5 Grendel AA used a .136 bolt face depth. AA added .01” to the length (2.810”) of the bolt to permit the use of standard length firing pins. Typical 5.56/223 AR-15 bolts use a .125” bolt face depth and a bolt length of 2.800”. An out of spec firing pin protrusion can contribute to pierced primers or slam fires in AR-15’s because of the floating firing pin design. To short of firing pin can lead to failure to fire or light strikes.

Brownell?s sell a firing pin protrusion gauge.

https://www.brownells.com/gunsmith-tools-supplies/measuring-tools/firing-pin-protrusion-gauges/firing-pin-protrusion-gauge-prod26477.aspx

[Growler]

^ This.

Every one of those primer strikes look excessively deep. The firing pin protrusion gauge will confirm if this is the case. I just got one and can confirm it is very easy to use.

By any chance, do your hand-loads use military (hardened cup) primers like CCI 41? That could explain why this issue wasn’t seen before. There may be other issues. Best to check to be certain. Good luck!

[Jimla]

This is really troubling, has anyone else had problems with Hornady ammo?

I have seen similar problems but the Hornady ammo was not the problem, if you bought a 18" Bear Creek they may have gave you my old barrel I returned.

http://www.65grendel.com/forum/showthread.php?19570-18-quot-Bear-Creek-Arsenal-6-5-Grendel-Upper-Range-Result&highlight=range+jimla

[snell]

Thanks Vascar2...

Looks like mystery solved. I measured the bolt and sure enough it is 2.800". The bolt face depth is .136". Fortunately I have several new firing pins squirreled away from my high power days and they are in the 3.270 " range. I'll try one of them and report back.

[VASCAR2]

I measured all eight of my AR-15 firing pins and they were all within .008 inches in length for the tolerance of FP protrusion. The longest was 3.280 inches and the shortest was 3.274 inches. I called Brownell’s technical and questioned them about selling shorter firing pins with their .2800 inch length 6.5 Grendel Bolt/BCG. The tech I spoke with was unaware of the difference in bolt length with the 6.5 Grendel. Brownell’s does not sell firing pins specifically short enough for the .2800 length bolt with .136 inch bolt face depth. If I needed to shorten a firing pin I’d probably purchase a Stainless Steel firing pin.

I suspect the manufacturer of the Brownell’s 6.5 Grendel BCG uses a firing pin protrusion gauge to verify the bolt and firing pin are within spec prior to sale.