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Hey guys, finally finished my Grendel and got her test fired. Alexander 16" lite barrel with normal AA bolt, non adjustable steel set screw has block. Tried the upper on 3 lowers one with magpul Prs and 2 carbine buffers. Initially had the gas block not seated to shoulder once I adjusted that I was getting extraction and most times ejection, however I could not get it to come back far enough. 3 out of 4 AA mags (2-10's & 2-17's current stock) worked as far as allowing me to hand cycle however 1 of my 17 rounders hits the bolt carrier hard and the carrier drags too much for any function. Ammo was PPU 110 fmj and 120 hp. Started to eject consistently towards the end of my 40 RDS but still could not get lock back. On the bright side I got it roughly sighted at 25 yds in 3 shots and produced my first ever 7 shot group that was smaller than my thumb with 4 shots touching shot single shot bolt action style. Can't wait to get her running right and stretch it out.
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I was just about to post my own thread regarding the same exact issue i just had this last Saturday at the range when i saw this post!
I was testing out my new build just completed last week with both 110 and 120 Prvi. I had crazy bad short stroking issues and no lock back on empty mags. limply.
I had to hand feed almost all my rounds.
I was using a brass catcher so it was hard to tell the ejection quality but they did appear to eject I shot a total of 80 rounds(40 was 110gr, and 40 was 120gr), and neither was better than the other.
The best i did was on one box of the 120gr i got six of the ten rounds in the mag to self-feed.
Unfortunately i didnt bring any of my Hornady out so could'nt compare to that.
When i got home i checked out my entire gas system, including leak testing with air/soapy water, and could find nothing wrong with it.
I did have a senior member here on the forum mention to me not long ago he had short strokes with the 110 in the past, he didnt say if it was only on 110, or he did/didnt have the issue with the 120. I am assuming the two loads are identical other than the grain of bullet used.
Anyways, i still have one box each of the 1110/120, next range visit i will be taking that and the Hornady 123gr out and something tells me the hornady will cycle fine... -
A few things I can give advice on, Double and tripple check the gas block placement also measure the gas port and the gas hole in the gas block to make sure the gas hole in the gas block is bigger then the gas port in the barrel.
I would change out a non adjustable gas block for one that is adjustable and I would use blue locktite to bed the gas tube into the gas block and then red locktite to bed the gas block on the barrel.
Also duoble check gas tube alinment into the carrier.
And try a diffrent load other the the PPU try some amax are some BT.
And also maybe look at the buffer weight and or carrier weight.
As far as the mags you are using, try loading them up to a full load and let them set for a week are two to help break the spring in.
I hope this advice will help both of yall and Im sure more knowledgable members will be along shortly to give more advice.Comment
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Hi guys,
Less likely to be problems with factory ammo in the scenario of a new gun.
You both have new builds and everything is going to be tight and rough. Before thinking there might be something wrong with the fundamental specs how about breaking the rig in.
Sit in front of the telly and work those actions like a teenager on heat. A 100 times should be a good start. Then clean the oil off and re-oil. Like a new car engine that requires an oil changes early in its life to remove micro particles. Go overboard with the lube; oil the parts that reciprocate and grease the parts that turn. As A5 suggests, those mag springs might be too tight. Fill them up and leave them for a while.
If you can try someone else's 6.5 bolt and carrier, and your bolt and carrier in their gun that's always a good way of figuring out what parts work and what don't. Same with the mags. If that's not an immediate option then it's time to watch telly and get those right hands cranking...Comment
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So being my first Grendel I did not know what to expect. My other AR's ran right off my work bench. Pretty much ruled out my lower since it was the same on 3 diff lowers. Is the wolf military classic any better or should I avoid it? At 149.75/500 I might get it for break in purposes unless it's going to incite more headache. According to the live inventory they have sold 11 cases since 9am est today so I need opinions quickly please. Or do I spend the same money to buy dies and components for 200 rounds of 123 GR sst hand loads? Will reload eventually but prefer factory loads to prove rifle function.Last edited by Fishinglink; 07-19-2016, 12:35 AM.Comment
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Klem makes a good point about oiling it up and working the action to break it in.
When I built my new upper useing the best parts I could source, I cleaned every part till it was dry and free of all oil and grease then assembeled and oiled the crap out of the bolt and carrier as well as the inside of the upper and worked the action for bout three hours every night for bout a week while I waited on some parts for my lower to arrive.
Doing this really seemed to help make the rifle run smoother when it came time for function testing and setting the gas block.Comment
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Your other builds worked off the bench probably because they had more gas at the port and the timing was within reliable specs.Originally posted by Fishinglink View Post
When you pushed the gas block right up against the shoulder have you confirmed for certain that the holes have lined-up? What I mean is have you used some sort of measuring device to confirm the block is designed to be hard up against the shoulder?
Your three lowers...What are the weights of the carbine buffers (the PRS A2 rifle buffer will be equivalent to a carbine H3)? It may be that you need a lighter buffer.
Certainly sounds like the mags springs are stiff.
Regardless, you need to crank that carrier 100 times...It may be the factory ammo but there are a number of other causes that are more likely in a brand new build.
Can't comment on the reliability of PPU as I've never used it.Comment
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Mags were loaded with 10 RDS per for 3 weeks. No I have not removed the block and measured. I went increments with feeler gauges and did not get extraction/ejection until it was butted to the shoulder. The carbine buffers were standard weight. All 3 lowers functioned with 5.56 w/ carbine and middy and 300bo w/ carbine gas. This rifle was only a barrel and bolt swap. Upper and carrier have about 300 rounds through them. The carrier was dryer than I would normally run a virgin build but was oiled. I ordered more ammo and should be able to test in a few weeks again.Comment
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In your last post you stated you didnt get extraction are ejection till it was butted to the shoulder.
Here is what I would do remove the gas block and messure the distance from shoulder to center of gas port and then messure from outside edge of gas block to hole in the gas block and see if they match and also look in the block and make sure the hole in the gas tube is properly lined up with the hole in the gas block.
Reason Im saying to check this is when I went to mount my syrac adjustable gas block and gas tube on my JP barrel. I could not get proper functioning at all and the reson why was two fold. One the gas tubes hole was not cut correctly and when installed in the gas block it did not line up properly. Two the way JP cuts their barrels gas ports the gas block has to be butted to the shoulder to aline properly and when I would do that I would get the same thing happening that your saying your rifle is doing.
What I did to fix mine was order a diffrent adjustable gas block from JP with the tube installed at the factory and it fixed the problem completely.
Im not saying go order a new gas block and tube but it wouldnt hurt to check these few things.
Best and fastest way to tell if your not lined up properly is when you remove the gas block there will be a gas shadow on the barrels gas port, if the gas shadow is more too one side then the other your gas block was not lined up correctly.
Hope this advice helps sir.Comment
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So gas block was a little off center but not blocking the gas port judging by the carbon ring. Also hole in gas tube is not perfectly centered in hole in gas block. Lots of carbon fouling on the tube coming out of gas block so apparently it is leaking there also. Going to open the hole in the tube and bed to gas block and see where that gets me. Thanks for the tips Klem and A5. Will report back after this weekend maybe.Comment
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Dont forget you can use blue locktite to bed the gas tube into the gas block and close of that gas leak as well.Comment
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Fishing,
I am interested when you say the gas tube hole is not lining up with the hole inside the gas block.
Is there a tiny roll-pin holding the tube to the block? For the avoidance of doubt and no disrespect, but did you tap out the tiny roll-pin to be able to pull the the tube out of the block?Comment
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God I hate that stupid pin... LOL!!Comment
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Yes I pulled the pin to pull the tube. Yes I reinstalled pin and verified hole in tube sat further towards the long end of the tube. I elongated the hole towards the pin and bedded the tube with blue locktite. I also got my wolf ammo and loaded up all mags to capacity. 3 out of 4 lock into mag well. One of my 17 round mags will not with the bolt forward. Emptied that mag and still won't insert. Took mag completely apart and tried to insert empty shell of mag and would not go, so I pulled bolt back and locked it in and release bolt. Bolt stops halfway closed. Is anyone else experiencing issues will the 17's that shipped around June 25- July 4th? Measuring with my caliper I can't find any difference from mag catch hole to top of lips on the 17's however there is a big difference between that measurement and the same on the 10's I have. Like .030" difference with the greater being the 17's. Won't get to shoot her this weekend as hoped but want to make sure I have a fighting chance when I do.Comment
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Ok, fair enough.
Sounds like you are getting to the bottom of the issues. If it makes you feel any better having two unrelated spec malfunctions in a new build is unusual...just saying.
No problems with any of my ASC mags, except they all take one less round than stated on their website.Comment
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