New 18in Liberty barrel and bolt, is this normal for the 6.5G

[alligator]

Cliffs notes: New barrel and bolt, 26 rounds fired, cratered primers and ejector marks with factory Hornady, bolt wear.

This is my first Grendel. I ordered in December and received it in January. It is an 18in medium profile Liberty barrel. It was the whole kit, upper, gas block/tube, bolt and heliport brake. I assembled it with a 12in Larue Tactical rail and a Palmetto State Armory "premium" bolt carrier. I have assembled uppers/complete ARs for the past few years with great success.

I fired exactly 26 rounds of factory Hornady 123 SSTs. This is the only ammo available locally. I used a 3-12 Nikon M223 scope. I have yet to buy a scope for this rifle so I borrowed it off of one of my 5.56s. I got it on target at 165yards shooting clays. Very easy. I then started shooting at an 8in steel plate at 500yards. I hit the plate a few times. I have not shot for groups at 100 yet.

The bullets chambered fine dropping the bolt on them. They cycled the gun with no malfunctions. I did not look at the brass or bolt while out, we were too busy shooting other stuff. When I separated all of my brass at home I started looking at them. They all have some cratering on the primers and most have ejector marks.

The bolt has some marks on it. Mainly the corners of the lugs. You can see the shiny spots in the pics. The metal is slightly deformed on these areas. You can catch your fingernail on it, they are not just rub marks. I am measuring the bolt face depth at .130. These are cheap calipers though, can they be that far off? It was generously lubed with Mobile1 Syn. just like my 5.56s. Wet but not dripping. No oil on the bolt face. Barrel was cleaned before shooting.

Is this normal wear? Im thinking not. Does it just need a good break in? Should I send it in to get checked just in case?

[explorecaves]

Lots of discussion about possible tight throats in this thread: http://www.65grendel.com/forum/showthrea...-chambered.

I would measure your chamber and see what your OAL is. If you don't have the tools to do so, measure a few factory rounds before and after chambering them (remove firing pin first).

[alligator]

I saw that thread. It is now locked. Not a good idea to put BCG in without the firing pin in. The cam pin can turn and jam up bad.

[Kikn]

I think your bolt and bcg may be the problem. From what I understand the face depth should be at .136 and if it isn't a bcg for a grendel the length of the bcg is a shorter length than a standard BC. And the extra length on your can cause the cratering you are seeing.

I'm no expert by any standard but if I'm wrong I'm sure I will be corrected shortly.

[LRRPF52]

Not only do you have cratering, but significant ejector channel extrusion (brass flow into the ejector hole).

Primers start to crater in the mid-high 60,000 psi range. I also load for the .270 Winchester, which is rated to 65,000psi by SAAMI. Start loads and loads in the lower-to-mid range won't show any of the signs I'm seeing on your brass, even when I shoot it in hot weather, and they are at or over 60,000psi easily.

Keep in mind that the Grendel is a SAAMI-rated 52,000psi Maximum Average Pressure cartridge. Something is wrong.

The extreme pressure signs on your brass, combined with the visible damage to your bolt indicate something very wrong. I obviously cannot recommend shooting this anymore, and would advise you to seek guidance from the source of the barrel/bolt combo and ammunition maker.

Just in case, record the ammo lot number. I think I know where the problem is, but record the lot # anyway. If you have a short throat, and the projectile is jammed, these signs would be consistent with that condition.

If you have any of the loaded ammo still, take a marker and color the projectile ogive, while keeping the firearm pointed in a safe direction, carefully chamber a round of the loaded 123gr SST, then remove it. You can slowly close the bolt, then extract it while keeping your finger in the ejection port to prevent the ejector from forcing the ogive against the inside of the barrel extension. Tell us what the projo looks like after performing this.

[NugginFutz]

I saw that thread. It is now locked. Not a good idea to put BCG in without the firing pin in. The cam pin can turn and jam up bad.

Good point about the firing pin. I'd never considered its need to keep the cam pin aligned, when I'd recommended its removal to another member, earlier this week.

[SHORT-N-SASSY]

alligator,

Welcome to the 6.5 Grendel Forum!

Like you, I recently shared my experience on the Forum, with a newly installed AR-Stoner 6.5 Grendel Barrel and Bolt http://www.65grendel.com/forum/showthrea...red/page48 (see Reply #473, third from top of Page). My measured Bolt face depth is 0.135". Fired cases do show some firing pin cratering, but no Ejector marks, nor nicks on the Bolt lugs, such as shown in your pics.

Question: After closing the Bolt on a fresh factory-loaded cartridge, then extracting it, are there any marks on the bullet, a short distance from the case neck, such as shown in my pic in the above-referenced Link?

[45r]

The headspace on my chamber is minimum with my bolt that measures .135 deep and I polished the bolt face and lapped the lugs.
Maybe since your depth is .130 you might have too tight headspace.
The face of your bolt looks to have a lot of copper build up for 26 rounds fired.
You should have at least 4 thou headspace clearance on a new barrel and bolt.
I wouldn't use that bolt anymore until the depth can measure .135 deep.
The lugs have to be right also.

[customcutter]

Alligator, welcome to the forum. Sorry to hear about your problems with the Liberty 18" barrel. I have one also, but haven't been to the range with it yet. Mine is chambering and ejecting easily (not slamming the bolt home) with no marks on the ogive.

Remember when you use your caliper as a depth gauge to set the base on a flat hard surface and open the gauge so that the extension is even with the rest of the bottom of the caliper. It may account for the .005" that you are missing. I saw someone else post this, and had never considered it when measuring depth.

Edit, My bolt is from a different mfg, and has the light rings around it.

2nd Edit, Sorry I just realized that if the caliper were fully closed and zeroed your length would be long not short. Unless your extension is extended past the base, when zeroed.

[alligator]

Remember when you use your caliper as a depth gauge to set the base on a flat hard surface and open the gauge so that the extension is even with the rest of the bottom of the caliper. It may account for the .005" that you are missing. I saw someone else post this, and had never considered it when measuring depth.

Good idea. I will try that. I will also chambering a few and measuring before and after OAL. I will also put some black marker on them. I def wont be shooting it anymore. It will be going back.

Edit: Tried zeroing on a flat surface. No difference. Still measuring .130 bolt face dept. I am going to chamber some in a few minutes.

[rickOshay]

Where did you get your kit?

[MTNmyMAG]

This is what my brass looks like in my BHW barrel when I get close to a warm load, I have been told I have an early unlocking issue, still have not tried a heavy buffer to see if that solves it.

[Aaron_S]

Good idea. I will try that. I will also chambering a few and measuring before and after OAL. I will also put some black marker on them. I def wont be shooting it anymore. It will be going back.

Edit: Tried zeroing on a flat surface. No difference. Still measuring .130 bolt face dept. I am going to chamber some in a few minutes.

Find something else to measure. A bullet diameter or a new coin has known dimensions.

[alligator]

Got the kit directly from Satern.

I colored a couple of 123gr SSTs with a dry erase marker and inserted them by had. After the extractor snapped on they did require a little push to get the bolt to lock. They also required a tug to get out. The normal operation of the bolt being pushed with the buffer spring would be enough to overcome the force to push the bullets into the barrel. Notice the marks circled in green. Both measured 2.248 before and after inserting them.



Measured brand new Hornady 53gr Vmax and 150gr FMJ/BT. Calipers measured .224 and .308.

[BjornF16]

I just measured my Satern supplied bolt (for Spartan barrel) at .136".

It appears you have both a out of spec bolt and short throat.

An earlier email with a Steve Satern attributed quote indicated S. Satern didn't believe the SAAMI spec included throat dimensions...I wonder if Satern or PTG believe they could shorten the throat and still call it SAAMI Grendel?...

http://www.65grendel.com/forum/showthrea...#post83844

There is no Saami spec or requirement for throats. It's up to the reamer manufacturer to grind it to the print.

[LRRPF52]

This appears to be what I suspected it would be: a textbook case of being jammed into the lands.

The SAAMI Grendel chamber is actually pretty forgiving. Chamber length to the mouth of the neck is 1.530", and the .5 degree throat starts from there. The SAAMI spec has a detailed diagram for the throat.

Most brass is 1.515"-1.520" in length, and the ogive has plenty of room to transition to the throat. When you have 10-15 thousandths before you even hit the .5 degree throat, and bullets are jammed, you're not dealing with much allowable COL in that chamber.

[45r]

My lugs measure .280 long and the depth to bolt face is .135 and the spec is .143 to .146 for Grendel when you subtract 135 from 280 you get .145 so mine fits within the 143 to 146 spec.
If your lugs are .280 long and your bolt face depth is .130 yours is at .150 and 4 thou over.
Your firing pin strike is 5 thou less also with a depth of .130 compared to .135.
It seems you should be able to send that bolt in for a replacement.
You shouldn't be seeing scrape marks on the bullet that close to the mouth of the brass.
I've seen very faint light scratching on my 85 grain sierra HP's starting .100 from the mouth seated to 2.170 where they rub into the throat.
I have to use binoculars turned backwards to see them.
I polished the heck out of my barrel's chamber and throat with JB's and flitz and that might have smoothed some of the roughness on mine.
I wish I had some 123 SST's to try and see where they would touch the throat.
I don't think they would look like yours though since it looks like 123SST's taper inward sooner.

[Lead Chucker]

Well i got my buddys grendel today that i built last year with a 16" Stoner barrel. I measured the COL with a 123 amax, same bullet i used last week ti measure my 18" Satern. His Stoner measured 2.212" to a slight touch in the throat which i first believed was the cone on angled throat not lands as we believed before. I then took the same bullet & loaded it in a dummy round set to 2.250". It loaded & extracted easly from mine with no marks of any kind. I the marked it with a sharpie & loaded it in my buddys Stoner by hand & seated it by ridding the BCG with charging handle & locking it in with the forward assist wich was hard. I then extracted it which was kinda difficult. There was heavy land marks, i kept seating it deaper in the dummy round .005" at a time til i saw no land marks. It was seated to 2.211" before it was chambered to where there was no land marks. Each .005" i seated it i could tell it was easier tochamber & extract. There is no dought the Stoner/Liberty barrels have a shorter throught. His head space is almost the exact same as my Satern cut barrel. I also took a round that was loaded for mine & chambered it in his, a 123gn Amax OAL of 2.260" that loads & extracts easy in mine. When loaded it in his it jamed into the lands & pulled the bullet half way out of the case when extracted. So his was built in January of 2013, my dads Stoner barrel from this year measures about the same, but does have a little longer throat than my buddys. My buddys has about 130 rounds through it while dads hasnt been fired yet. Go figure.

[MTNmyMAG]

This is exactly what my brass looks like, I was told it was probably an early unlocking issue. I dialed down my loads and got away from these signs. I am really wanting to know what is done to fix this. I would like to bring more heat.

[RAM2940]

45r:

I'm having a issue with a LBC bolt i believe the lugs are to long, Face depth .1345 and a lug length of .284, who made your bolt. I am thinking about trying to polish the backside of the lugs to .280.