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Author Topic: Bolt hold open issue  (Read 9440 times)
Lungorthin
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« on: February 12, 2017, 12:19:57 AM »

So I've had my M17S for a little while and its been running flawlessly since I bought it.
However, last time I went to the range, the bolt hold open would engage after every single shot. Issue arrised out of nowhere, never occurred before and now it happens every time without fail. I'm guessing the force of the recoil jostles the bolt catch into the up position, holding the bolt back as it tries to strip off a new round.
I figured it was just a worn out bolt catch spring so I replaced it with one of the same size from Brownells, took it to the range, and same problem. Just locks open on every shot.
Tried using a variety of mags and keeps happening.
Any ideas? Do I need a specific spring or is it something else?
Thanks
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srfnken
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« Reply #1 on: February 12, 2017, 12:35:16 AM »

This is a new one for me.  Have not had or heard of this issue before.  I will have to think about this one.
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Maverick223
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« Reply #2 on: February 13, 2017, 02:39:33 AM »

I've had a modified first generation M17S for some time now and fired many thousands of rounds from it and just a few weeks ago had a similar problem (after nary a problem when using good magazines).  It would cycle, extract, and eject just fine, but would fail to strip/chamber a round from a known good magazine (and I tried several to be sure...all were PMags or L5s and previously 100%).  Instead it would engage the BHO after every stinking round, to add further confusion it fired a couple of magazines successfully prior to exhibiting the problem.  I got it home and broke it down (thinking it might be something wrong with the gas system (like actually needing to pull the piston and clean it...for the first time), but instead I noticed that the bolt buffer was almost completely disintegrated leaving only a nub to fill the hole in the back of the action plate and not "buffering" at all.  My understanding is that this condition is very bad for these rifles, though I saw no additional damage to the rifle.

I went to K&M and purchased a 3pk of buffers (which, if the original was any indication of service life, should easily be a lifetime supply).  A couple of weeks later the package arrived (along with the trigger lightening kit, which was long past due), installed it (which was a very tight fit, requiring me to insert it with a pair of pliers for proper seating) and it immediately solved the issue.  I'm not going to guarantee that it will solve your problem in the same manner, but that would be the first part to check.
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Lungorthin
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« Reply #3 on: February 13, 2017, 02:44:03 AM »

I've had a modified first generation M17S for some time now and fired many thousands of rounds from it and just a few weeks ago had a similar problem (after nary a problem when using good magazines).  It would cycle, extract, and eject just fine, but would fail to strip/chamber a round from a known good magazine (and I tried several to be sure...all were PMags or L5s and previously 100%).  Instead it would engage the BHO after every stinking round, to add further confusion it fired a couple of magazines successfully prior to exhibiting the problem.  I got it home and broke it down (thinking it might be something wrong with the gas system (like actually needing to pull the piston and clean it...for the first time), but instead I noticed that the bolt buffer was almost completely disintegrated leaving only a nub to fill the hole in the back of the action plate and not "buffering" at all.  My understanding is that this condition is very bad for these rifles, though I saw no additional damage to the rifle.

I went to K&M and purchased a 3pk of buffers (which, if the original was any indication of service life, should easily be a lifetime supply).  A couple of weeks later the package arrived (along with the trigger lightening kit, which was long past due), installed it (which was a very tight fit, requiring me to insert it with a pair of pliers for proper seating) and it immediately solved the issue.  I'm not going to guarantee that it will solve your problem in the same manner, but that would be the first part to check.

Might try this, however, I'm in Canada and importation costs will cost me $250 + part cost...

EDIT: I noticed mine doesn't have a buffer at all. Bought it used and never had one in it.
« Last Edit: February 13, 2017, 02:47:07 AM by Lungorthin » Logged
Maverick223
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« Reply #4 on: February 13, 2017, 03:03:04 AM »

I'd say that's your issue then.

I know nothing of Canadian laws, but it's just a piece of plastic...they really impose that sort of tax for such a simple part or is the issue something else (I know shipping won't be near that much)?  If importation restrictions are the root cause I would consult Ken and ask him for suitable materials and have a machinist fabricate one for you (or if you have access to a lathe I'm confident it would be a reasonably simple task to turn one yourself).  I would speculate that the original is Urethane because it looked like a urethane boat trailer roller, but I don't know for sure (Ken advertises his as being better than the original, but doesn't disclose the material make-up).  If you want to give it a whirl let me know and I'll get you measurements from one of mine in the AM.
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Lungorthin
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« Reply #5 on: February 13, 2017, 03:32:01 AM »

I'd say that's your issue then.

I know nothing of Canadian laws, but it's just a piece of plastic...they really impose that sort of tax for such a simple part or is the issue something else (I know shipping won't be near that much)?  If importation restrictions are the root cause I would consult Ken and ask him for suitable materials and have a machinist fabricate one for you (or if you have access to a lathe I'm confident it would be a reasonably simple task to turn one yourself).  I would speculate that the original is Urethane because it looked like a urethane boat trailer roller, but I don't know for sure (Ken advertises his as being better than the original, but doesn't disclose the material make-up).  If you want to give it a whirl let me know and I'll get you measurements from one of mine in the AM.

Thanks for the offer but I don't have access too a lathe unfortunately.
And it's not so much that it's a tax, if it's considered a gun part, it falls under ITAR and cannot be mailed to Canada unless it's brought in by a certified importer. Two in Canada being Irunguns and Aztec, and they both charge $250 per order, even if it's as small as a firing pin.
I probably shouldn't fire the rifle without the buffer since it'll likely cause damage over time. Am I SOL on this?
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Maverick223
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« Reply #6 on: February 14, 2017, 11:08:07 AM »

I'd say that's your issue then.

I know nothing of Canadian laws, but it's just a piece of plastic...they really impose that sort of tax for such a simple part or is the issue something else (I know shipping won't be near that much)?  If importation restrictions are the root cause I would consult Ken and ask him for suitable materials and have a machinist fabricate one for you (or if you have access to a lathe I'm confident it would be a reasonably simple task to turn one yourself).  I would speculate that the original is Urethane because it looked like a urethane boat trailer roller, but I don't know for sure (Ken advertises his as being better than the original, but doesn't disclose the material make-up).  If you want to give it a whirl let me know and I'll get you measurements from one of mine in the AM.

Thanks for the offer but I don't have access too a lathe unfortunately.
And it's not so much that it's a tax, if it's considered a gun part, it falls under ITAR and cannot be mailed to Canada unless it's brought in by a certified importer. Two in Canada being Irunguns and Aztec, and they both charge $250 per order, even if it's as small as a firing pin.
I probably shouldn't fire the rifle without the buffer since it'll likely cause damage over time. Am I SOL on this?

I had no idea that ITAR was that strict regarding such simple parts (I thought it was reserved for major firearm components and quality optical devices).  I would take the measurements of the part (which I will be happy to provide upon request) to a local machinist or gunsmith and have them turn the part out of a durable plastic elastomer (like urethane or whatever Ken uses in the K&M replacement).  $250 is a lot of money to spend for a part that costs about $10 shipped!
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RGSB
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« Reply #7 on: February 28, 2017, 11:21:03 AM »

ITAR is quite reestrictive indeed, Ive heard of problems with people sending manuals to Canada
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Lungorthin
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« Reply #8 on: February 28, 2017, 08:54:55 PM »

Ok so I got my hands on a new bolt buffer and made it out to the range to test it.
It definitely feels smoother now. Failure rate was much better, however the bolt stop did hold the bolt back a few times.
I put about 60ish rounds through it and I had 5 or 6 failures where the bolt holds back with rounds still in the mag. Using standard USGI type mags.
Might try a stiffer spring in the bolt stop even though the stock spring is still pretty stiff.
Any other ideas I can give a shot?
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srfnken
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« Reply #9 on: February 28, 2017, 09:01:59 PM »

Can you take a picture of the lower from the top view with the lower off and a fully loaded mag in the lower so I can see the distance of the bolt catch in relation to the mag and rounds in the mag.  Make sense?
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Lungorthin
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« Reply #10 on: February 28, 2017, 09:16:02 PM »

Can you take a picture of the lower from the top view with the lower off and a fully loaded mag in the lower so I can see the distance of the bolt catch in relation to the mag and rounds in the mag.  Make sense?
Something like this?
Sorry it's upside down



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srfnken
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« Reply #11 on: February 28, 2017, 09:24:25 PM »

Great.  it all looks good.  now a picture of the action plate on the back of the bolt carrier group.  The part that is holding the rids in place.  I want to see from the side view how the bottom tang is angled if any.
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Lungorthin
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« Reply #12 on: February 28, 2017, 09:32:04 PM »

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srfnken
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« Reply #13 on: February 28, 2017, 09:47:10 PM »

When the carrier is in the upper there should be minimal play up and down.  This adjustment can be made by bending the tabs on the action plate.  The bottom tab should be as straight as possible and the side tabs will give you your up and down location to make it snug in the upper.  If this action plate is not snug (not tight should have some play) then it can do a couple of things.  Too loose and when the carrier comes back it will not depress the hammer all the way and the hammer will follow the carrier home and slam fire.  Too low and I am expecting that the bolt might be just barley hitting the top of the catch when it is coming back and making it jump up and then being caught by the bolt holding it open.  To adjust the tangs I use 2 crescent wrenches.  One on the back of the plate and the other on the tangs.  the one on the back of the plate it just to keep the back of the plate from bending when you have the other one on the tang to bend it.  It only takes a little bit to go a long way.  Try this and see if this helps.
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Lungorthin
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« Reply #14 on: February 28, 2017, 10:04:47 PM »

Ok just did it. Its snug enough so while its seated theres no wiggle, yet easy to remove.
So should all the tabs be straight? The two upper ones are angle inwards a bit
Also, when the bolt locks when the malfunction happens, it looks like the bolt hold open is almost completely engaged, as if I was holding it down in the lock position.
As it locks back, I can drop the bolt home with the bolt release paddle.
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srfnken
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« Reply #15 on: February 28, 2017, 10:27:14 PM »

Was it loose before the adjustment?  The side tangs will be bent inward.  Because the upper has a 10 angle on both sides, as you bend them outward it will force the carrier downward.  So yes they will be bent inward.
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Lungorthin
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« Reply #16 on: February 28, 2017, 10:31:37 PM »

There was the tiniest bit of movement before I made the adjustment. Maybe half a milimeter?
I'll update the thread when I have a chance to test it again.
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srfnken
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« Reply #17 on: February 28, 2017, 10:36:41 PM »

Did you have to adjust the bottom tang to make it more straight like at a right angle?  If this does not work I would try making the bend a little more so it raises the carrier up a bit to see what that does.  Take the tools with you to the range and do some adjusting there for testing.
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Lungorthin
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« Reply #18 on: February 28, 2017, 10:39:39 PM »

I bent it a very small amount so there is no movement now.
Thanks again. I'll keep tinkering with it at the range next time.
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