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Friend bought an Sanders 18 inch Grendel upper and is getting light primer strikes... every time. Swapped his upper to my Grendelhunter lower still the same, put my BCG in his upper still light strikes.
I put a new gas tube and has block on it still giving light primer strikes.
Threw the ammo in my AR with BCG and it fired....
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Might be too much headspace (chamber too long).
Has any round fired out of it?
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Yes after i put my Grendel hunter bolt in it... i got a few rounds to fire then went to light strikes again i think....
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Didn't I read somewhere that there are firing pins in two different lengths? Something having to do with a .125 and .136 bolt face?
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biodsl Wrote:Didn't I read somewhere that there are firing pins in two different lengths? Something having to do with a .125 and .136 bolt face?
Yea... I'm not at home now but will pull his BCG apart and compare it to mine tomorrow.... never had an upper do this before, I have built dozens.
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mdewitt71 Wrote:Yes after i put my Grendel hunter bolt in it... i got a few rounds to fire then went to light strikes again i think....
md,
The reason I ask this is because if you don't have Grendel headspace GO-NOGO gauges you can get an idea of the shape of the chamber from those few cases that fired. If the load is normal (not mild) then they should have expanded to the chamber. Compare them against the unfired ammunition, and spent cases from your own rifle.
Is the ammunition hand-loaded?
Do you have the Hornady Comparator headspace gauge?
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08-15-2023, 12:12 PM
(This post was last modified: 08-15-2023, 12:23 PM by VASCAR2.)
I would measure the bolt face depth and the overall length of the bolt from the tail to the face of the bolt. Measure the firing pin overall length. There is a .008 tolerance in fringing pin protrusion minimum length .028 to maximum .036.
AR-15 6.5 Grendel bolt face depth .136 AA bolt length 2.810 +or- manufacturing tolerance (usually .001-002)
Firing pin spec 3.2800 tolerance up to -.009.
A few 6.5 Grendel bolts are sold where the overall length is 2.800 and these bolts need a shorter firing pin to reduce the risk of slam fires or pierced primers. A standard 5.56 bolt face depth is .125 with an overall length bolt of 2.800 +or- manufacturing tolerance. A few 6.5 Grendel bolts have the .136 bolt face depth but use the shorter 2.800 overall length.
There have been a few instances over the years reported on this forum where the bolt and firing pin produced an out of spec firing pin protrusion.
If someone had a 6.5 Grendel barrel head spaced to use a .125 Type 1 (7.62x39) bolt but used the deeper .136 bolt face depth 6.5 Grendel bolt this could contribute to a minimum firing protrusion or excessive head space.
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Vas,
The OP swapped his mates BCG for his and still got light primer strikes. Fair to assume the OP's gun functions OK. His BCG works in his gun, but not his mates. This is why I think it's more to do with either the chamber reamed too long, or the ammo is too short, and the BCG is OK.
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mdewitt71 Wrote:I put a new gas tube and has block on it still giving light primer strikes.
Threw the ammo in my AR with BCG and it fired....
mdewitt71 Wrote:I have built dozens.
I have no idea why you thought changing the gas tube and block would affect this?
My first thought is chamber issues.
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Head space, function and depth gauges saves a lot of headache..
Be sure to check the case moves freely in and out of the bolt face and the ejector pushes completely flush..
Normally I would say light hammer spring/out of spec bolt-firing pin, out of spec gas tube interface with gas key, etc, but I think the others could be right about a chamber problem..
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Klem Wrote:Vas,
The OP swapped his mates BCG for his and still got light primer strikes. Fair to assume the OP's gun functions OK. His BCG works in his gun, but not his mates. This is why I think it's more to do with either the chamber reamed too long, or the ammo is too short, and the BCG is OK.
Another poster mentioned the difference in some Grendel bolts so I was just trying to provide information I had saved in regards to different products on the market. I think the OP can sort out the issue given enough time. It sounds like a chamber/head space issue but hard to say without having the upper to inspect.
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Klem Wrote:Vas,
The OP swapped his mates BCG for his and still got light primer strikes. Fair to assume the OP's gun functions OK. His BCG works in his gun, but not his mates. This is why I think it's more to do with either the chamber reamed too long, or the ammo is too short, and the BCG is OK.
My reaction as well when he said that about swapping BCGs. That seems to indicate the BCG is not the problem variable, which leaves the chamber as the likely culprit in the friends blaster.
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So, I took the owners BCG apart, it was gummed up pretty bad.... Asked him how he cleaned it and he said he has never taken it apart before.
When I took the firing pin and cam pin out, the bolt would not come out of BCG... Stuck solid...then when I did get it out, the extractor was stuck solid too.
Lots and lots of cleaning and soaking and then a long class given to the owner on how to maintain an AR .....
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08-29-2023, 02:25 PM
(This post was last modified: 08-29-2023, 05:29 PM by biodsl.)
mdewitt71 Wrote:Lots and lots of cleaning and soaking and then a long class given to the owner on how to maintain an AR .....
Your public service. Uncle Sam taught me this way back in 1981. I had to relearn it when I got back into ARs many years ago. This forum has been instrumental.
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mdewitt71 Wrote:So, I took the owners BCG apart, it was gummed up pretty bad.... Asked him how he cleaned it and he said he has never taken it apart before.
When I took the firing pin and cam pin out, the bolt would not come out of BCG... Stuck solid...then when I did get it out, the extractor was stuck solid too.
Lots and lots of cleaning and soaking and then a long class given to the owner on how to maintain an AR .....
Was it rusted? Ive been shooting ARs since the 1980s in high volume across a wide range of conditions, from desert to jungle, mountains and arctic, including suppressed.
Ive never seen an AR-15, M-16, or M4 BCG so fouled that we couldnt get it apart.
Do you live in a humid area and is the BCG nitrided?
Im interested what kind of BCG it is.
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md,
That would explain it. And here we were assuming it was at least clean and working.
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mdewitt71 Wrote:put my BCG in his upper still light strikes.
I'm still a little confused. He stated he put his BCG in his friends rifle, which I assume was properly cleaned) and it should have worked if it was just the dirty, frozen bolt carrier group of his friends rifle..He also stated: Yes after i put my Grendel hunter bolt in it... i got a few rounds to fire then went to light strikes again i think....
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