Grendel head scratcher

Mobuck · January 1, 2019, 08:30 AM

I've found that my 6.5 Grendel has an aggravating quirk. About 150 rounds through the rifle so I'd think the "new AR blues" should have been worked out.
When loading the first round from the magazine, the bolt doesn't fully close. Tried 3-4 mags from both sides. Doesn't make any diff whether from locked open bolt or hand cycled. Doesn't seem to make any diff whether 2 or 10 rounds in the mag, Extractor doesn't snap over case rim and I can't force it with the FA.
I can drop the mag(so it doesn't pick up another round) and let it slam closed on the already chambered round and it works. When fired, it works fine. I initially thought it was mag drag resistance but there may be something going on with the extractor. I've checked the extractor for function and it moves freely although VERY stiff.

CarJunkieLS1 · January 1, 2019, 09:15 PM

Is there a rubber o-ring along with the extractor spring? If there is try removing the o-ring.

stagpanther · January 2, 2019, 02:22 AM

Quote:

I've found that my 6.5 Grendel has an aggravating quirk. About 150 rounds through the rifle so I'd think the "new AR blues" should have been worked out.
When loading the first round from the magazine, the bolt doesn't fully close. Tried 3-4 mags from both sides. Doesn't make any diff whether from locked open bolt or hand cycled. Doesn't seem to make any diff whether 2 or 10 rounds in the mag, Extractor doesn't snap over case rim and I can't force it with the FA.
I can drop the mag(so it doesn't pick up another round) and let it slam closed on the already chambered round and it works. When fired, it works fine. I initially thought it was mag drag resistance but there may be something going on with the extractor. I've checked the extractor for function and it moves freely although VERY stiff.

Grendels are notorious for their "tough love."

Relax, it will work out eventually.

I assume your bolt and chamber type are properly matched?

You say the bolt doesn't fully close when attempting to chamber a cartridge from a magazine--when that happens is the cartridge wedged in the chamber or have any resistance when you extract it? If so, my guess is that more than likely it's an "alignment issue" of the bullet to chamber, something I've noticed the Grendel (and sometimes creedmoors too) are prone to if they don't get adequate lift by the feed ramps (especially if you like to handload bullets "way out there" towards the lands). You should see some signs of damage on the cartridge if there is a problem with the feeding.

An "over-powered" ejector can also keep your extractor from getting a proper grip. Often ejected cases from "over-powered" ejectors and/or extractors will show more damage than usual as a result of them being "hung onto" longer and impacting harder into the upper's ejection port case deflector. Should be fairly easy to tell if the ejector or extractor are the problems by simply taking the bolt out and seeing how easily you can wedge a case head into the bolt face by hand--should be some resistance--but not excessively hard (I know, that's a vague description, but you should be able to feel the difference). I sometimes end up stoning down the edges of the ejector and extractor claw on new bolts that are "over-powered." As a last resort I'll change out the ejector and extractor springs to lighten them up--these days manufacturers seem to favor stacking those little donuts for the extractor.

New bolts and extension lugs sometimes have edges that are sharp enough that they might create resistance to closing until the edges are worn a bit--you might also want to see if there any signs of the lugs showing a slight alignment problem--could be something is inducing a bit asymmetry to the BCG as it chambers a cartridge.

Sorry if this all is a bit wordy, just trying to figure the many possibilities. I assume your system is otherwise properly gassed and the right buffer/spring is matched for your BCG.

Mobuck · January 2, 2019, 07:15 PM

1: Correct bolt face and headspace
2: No damage to case or bullet from feeding mis-alignment issues
3: Chamber , bolt lugs, bolt, gas rings all clean and lubed.
4: Bolt hand cycled 40-50 times w/lube before initial firing.

I did forget to mention that I ran 40 rounds of WOLF steel case through the rifle to smooth things up a bit before cleaning and switching to Hornady and Federal brass cased. IIRC, the WOLF didn't have the issues.
I did take a look at the fired brass and it looks to have some extractor scars. Quite possibly a "too strong" extractor spring or "donut" is the culprit.

stagpanther · January 2, 2019, 08:30 PM

The steel case lacquer covered stuff? Huh...well OK. without spinning off into another discussion; I've never understood the logic of using cheap ammo for initial break-in, especially for a precision cartridge--but whatever.

Might want to double-check the chamber anyway for any possible deposits.

I'd try stoning down the sharp underside edge of the extractor claw and take off the edges at either end of the claw (in other words, if your looking at it as if it were a "C" take the sharp edge off the top and bottom ends of the "C"), as well as soften the outside circumference of the ejector (so it doesn't have a sharp right angle to the ejector face) That may be enough to allow the case rim to slip more easily into the bolt face. I keep a couple of spare NIB extractors on hand, they seem to work a little better in my experience.

If none of that works--and you're still pretty convinced the ejector and/or extractor are "over-sprung" then it should be easy to pop the pins remove them and "power them down." It's also possible that by reducing the power, you can end up with spent cases left in the chamber if they're not strong enough--which is why I'd explore the stoning the edges option first.

Mobuck · January 3, 2019, 08:21 AM

"I've never understood the logic of using cheap ammo for initial break-in, especially for a precision cartridge-"

"precision cartridge" or not, I see no reason to blast $1 a pop ammo downrange for no reason other than to exercise parts. My personal opinion is the copper washed bi-metal jacket bullets do an even better job of barrel smoothing than softer gilding metal jacketed bullets. The gritty European powder residue acts like lapping dust to knock off those offending burrs.

stagpanther · January 3, 2019, 09:38 AM

Quote:

"precision cartridge" or not, I see no reason to blast $1 a pop ammo downrange for no reason other than to exercise parts. My personal opinion is the copper washed bi-metal jacket bullets do an even better job of barrel smoothing than softer gilding metal jacketed bullets. The gritty European powder residue acts like lapping dust to knock off those offending burrs.

Like I said, I don't really want to spin this off into a separate thread--and I respect your opinion. I personally prefer the "controlled precision" approach from the get-go--and if there are real issues with the barrel I'd come out ahead in the long run by sending it back or tossing it into the tire iron pile if really does have a need for "projectile lapping."

have you decided what to try next to remedy the chambering issue?

Mobuck · January 3, 2019, 08:29 PM

"have you decided what to try next to remedy the chambering issue?"

Probably run another 40-60 rounds of steel case through it and see if it improves. If it is a stiff extractor or ejector, exercise will help.

stagpanther · January 4, 2019, 01:19 AM

Quote:

"have you decided what to try next to remedy the chambering issue?"

Probably run another 40-60 rounds of steel case through it and see if it improves. If it is a stiff extractor or ejector, exercise will help.

With the right handload you should be able to get great sub-MOA groups approaching .5 and stopping power for game as well. 8208 xbr is one of the best overall powders driving bullets in the 110-120 gr range in my experience.

Mobuck · January 4, 2019, 02:46 PM

I seem to have the problem worked out. Must have been a burr or some sort of debris causing the extractor to be overly stiff. Adding to this is the extremely strong magazine springs which cause considerable drag during chambering. The Federal brass may be softer than the Hornady, too.
Stagpanther, I'm not discounting your ideas/opinions but handloading is not in my game plan at this time(or maybe not ever again). I'm an old man and having some issues with concentration and just no longer comfortable at the loading bench.

stagpanther · January 4, 2019, 02:55 PM

Quote:

I'm an old man and having some issues with concentration and just no longer comfortable at the loading bench.

Understood--I left the 60 year old mile marker behind last year--and with chronic Lyme disease everything is a challenge. Glad you licked the chambering thing--wish you happy shooting.

January 1, 2019, 08:30 AM	#1
Mobuck Junior member Join Date: February 2, 2010 Posts: 6,846	Grendel head scratcher I've found that my 6.5 Grendel has an aggravating quirk. About 150 rounds through the rifle so I'd think the "new AR blues" should have been worked out. When loading the first round from the magazine, the bolt doesn't fully close. Tried 3-4 mags from both sides. Doesn't make any diff whether from locked open bolt or hand cycled. Doesn't seem to make any diff whether 2 or 10 rounds in the mag, Extractor doesn't snap over case rim and I can't force it with the FA. I can drop the mag(so it doesn't pick up another round) and let it slam closed on the already chambered round and it works. When fired, it works fine. I initially thought it was mag drag resistance but there may be something going on with the extractor. I've checked the extractor for function and it moves freely although VERY stiff.

January 2, 2019, 08:30 PM	#5
stagpanther Senior Member Join Date: March 2, 2014 Posts: 11,779	The steel case lacquer covered stuff? Huh...well OK. without spinning off into another discussion; I've never understood the logic of using cheap ammo for initial break-in, especially for a precision cartridge--but whatever. Might want to double-check the chamber anyway for any possible deposits. I'd try stoning down the sharp underside edge of the extractor claw and take off the edges at either end of the claw (in other words, if your looking at it as if it were a "C" take the sharp edge off the top and bottom ends of the "C"), as well as soften the outside circumference of the ejector (so it doesn't have a sharp right angle to the ejector face) That may be enough to allow the case rim to slip more easily into the bolt face. I keep a couple of spare NIB extractors on hand, they seem to work a little better in my experience. If none of that works--and you're still pretty convinced the ejector and/or extractor are "over-sprung" then it should be easy to pop the pins remove them and "power them down." It's also possible that by reducing the power, you can end up with spent cases left in the chamber if they're not strong enough--which is why I'd explore the stoning the edges option first. __________________ "Everyone speaks gun."--Robert O'Neill *I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!* Last edited by stagpanther; January 3, 2019 at 03:06 AM.

January 1, 2019, 09:15 PM	#2
CarJunkieLS1 Senior Member Join Date: October 1, 2013 Posts: 686	Is there a rubber o-ring along with the extractor spring? If there is try removing the o-ring.

January 2, 2019, 07:15 PM	#4
Mobuck Junior member Join Date: February 2, 2010 Posts: 6,846	1: Correct bolt face and headspace 2: No damage to case or bullet from feeding mis-alignment issues 3: Chamber , bolt lugs, bolt, gas rings all clean and lubed. 4: Bolt hand cycled 40-50 times w/lube before initial firing. I did forget to mention that I ran 40 rounds of WOLF steel case through the rifle to smooth things up a bit before cleaning and switching to Hornady and Federal brass cased. IIRC, the WOLF didn't have the issues. I did take a look at the fired brass and it looks to have some extractor scars. Quite possibly a "too strong" extractor spring or "donut" is the culprit.

January 3, 2019, 08:21 AM	#6
Mobuck Junior member Join Date: February 2, 2010 Posts: 6,846	"I've never understood the logic of using cheap ammo for initial break-in, especially for a precision cartridge-" "precision cartridge" or not, I see no reason to blast $1 a pop ammo downrange for no reason other than to exercise parts. My personal opinion is the copper washed bi-metal jacket bullets do an even better job of barrel smoothing than softer gilding metal jacketed bullets. The gritty European powder residue acts like lapping dust to knock off those offending burrs.

January 3, 2019, 08:29 PM	#8
Mobuck Junior member Join Date: February 2, 2010 Posts: 6,846	"have you decided what to try next to remedy the chambering issue?" Probably run another 40-60 rounds of steel case through it and see if it improves. If it is a stiff extractor or ejector, exercise will help.

January 4, 2019, 02:46 PM	#10
Mobuck Junior member Join Date: February 2, 2010 Posts: 6,846	I seem to have the problem worked out. Must have been a burr or some sort of debris causing the extractor to be overly stiff. Adding to this is the extremely strong magazine springs which cause considerable drag during chambering. The Federal brass may be softer than the Hornady, too. Stagpanther, I'm not discounting your ideas/opinions but handloading is not in my game plan at this time(or maybe not ever again). I'm an old man and having some issues with concentration and just no longer comfortable at the loading bench.