AR Sponsor
Posted: 1/1/2016 7:03:56 PM EDT
|
Hello all! So I wanted to run this by everyone. I got a deal from Crypitc Coatings on 2 of their BCG's (mystic gold and mystic black) and while testing them I had my first failure to fire.
So while messing with the bolt when I initially bought them, the tolerances were very tight. The bolt itself will not come out with a swing like a normal lubed bolt would do. This was the case with both. At the moment, this is what my conclusion is, but wanted to hear some different thoughts to see if I'm missing something. So, here's my internal setup... Spikes T2 Buffer Spikes NB Battle Trigger KNS Anti-Rotation Pins, Gen 2 JP Reducd Weight Trigger/Hammer Spring Set (Another possible culprit) Mil-Spec Buffer Spring AMMO - PMC X-TAC XP193 I think that about covers it. Thanks in advance! |
| Sounds to me like there is some additional coating inside that has decreased the I.D. and the bolt is not able to move freely as it should. That area may need to be reamed out just a bit to get the proper clearance. I have had to do this to a couple bolt carriers over the years. |
|
The bolt carriers are too tight. A build up of whatever their coating is most likely. Possibly the groove where the gas rings has buildup in it keeping the rings from fully compressing.
By the way, tightness does not mean a tight tolerance. This is an example of too loose a tolerance. Tolerance means how mjch difference there is from the spec. Now much of a plus or minusthere is from the specified value. It is not how loose or tight the parts fit together. |
|
Quoted:
Sounds to me like there is some additional coating inside that has decreased the I.D. and the bolt is not able to move freely as it should. That area may need to be reamed out just a bit to get the proper clearance. I have had to do this to a couple bolt carriers over the years. That's the first thing I thought of the second I put my hands on the BCG. |
|
Quoted:
The bolt carriers are too tight. A build up of whatever their coating is most likely. Possibly the groove where the gas rings has buildup in it keeping the rings from fully compressing. By the way, tightness does not mean a tight tolerance. This is an example of too loose a tolerance. Tolerance means how mjch difference there is from the spec. Now much of a plus or minusthere is from the specified value. It is not how loose or tight the parts fit together. The bolt fits into the carrier just enough to fit, very tight fit. |
|
Quoted:
The bolt fits into the carrier just enough to fit, very tight fit. Quoted:
Quoted:
The bolt carriers are too tight. A build up of whatever their coating is most likely. Possibly the groove where the gas rings has buildup in it keeping the rings from fully compressing. By the way, tightness does not mean a tight tolerance. This is an example of too loose a tolerance. Tolerance means how mjch difference there is from the spec. Now much of a plus or minusthere is from the specified value. It is not how loose or tight the parts fit together. The bolt fits into the carrier just enough to fit, very tight fit. Without the cam pin in, the bolt should be able to spin freely inside the carrier. If it does not, you most likely have some of the coating causing the difference. |
|
Are those shiny gold and black coatings on the inside of the carrier where it would normally be chromed? If they are, thats most likely the problem. Did you lube all parts before installing/firing? I'm sure even these parts with the blingy type finishes would still require lube, right? I would call Cryptic and ask them whats up and how to lube.
|
|
Bolt and carrier drawings are available on the web.
Get the drawings and see if their dimensions are in spec. They say their BCG’s are Toolcraft and chrome lined to mil-spec. They don’t say who applied the chrome. They also say their coating is 2-3 microns. I can’t imagine that would be a problem. It sounds like you need to follow the usual troubleshooting for FTF. Check firing pin protrusion. What kind of primer strike did you get? Did the bolt fully close? Take off the o-ring. Reduced hammer spring is certainly a possible cause especially with some primers. |
|
pic of the round and indent in the primer?
You have a low powered weak hammer spring, therefore hard military primers are not going to go off every time. It's been noted for a long time over the years that is the downside to the light springs. For the advantage of a light trigger pull you get the disadvantage of less hammer strike requiring the use of soft primers. For a defensive use gun, the light springs are potentially a fatal flaw, on a range gun shooting hard primer ammo cheap, it's random training for misfires. Some actually do that to practice reloading drills. Not optimal in competition or combat, tho. |
All these wiz-bang coatings. 
I suggest getting some M855 and heading back to the range. Stiff BCG's will wear (ie gas rings) and loosen with use, and the full power 5.56 ammo helps speed up the process. ETA: Hard to diagnose gun issues via the internet, but you could also remove the gas rings and test fit. The bolt should move freely within the carrier without gas rings. Also, I've not seen it mentioned, but all this is assuming you're already using copious amounts of oil. If not, apply said large volume of oil and repeat testing. |
|
Quoted:
All these wiz-bang coatings.
I suggest getting some M855 and heading back to the range. Stiff BCG's will wear (ie gas rings) and loosen with use, and the full power 5.56 ammo helps speed up the process. ETA: Hard to diagnose gun issues via the internet, but you could also remove the gas rings and test fit. The bolt should move freely within the carrier without gas rings. Also, I've not seen it mentioned, but all this is assuming you're already using copious amounts of oil. If not, apply said large volume of oil and repeat testing. That. |
|
A brand new bolt - or more accurately, new bolt RINGS - should be a VERY tight fit in any carrier. Your test with an "arm swing" is actually similar to a test to determine if the rings are worn. In this test, you simply hold the BCG bolt-down, and if the bolt slides out of its own weight, the rings are worn. A new bolt/new rings should NOT slide out of the carrier easily, and an "arm swing" should only get you (at best) a little movement of the bolt.
Cryptic is the retail arm of Toolcraft, and they know their stuff when it comes to making carriers, so I would highly doubt that the carrier's bore is undersized, even with the coating (which Cryptic states is in the 2-3 micron thickness range). It really sounds like you have a "nice and tight" brand new BCG that behaves just like a brand new BCG should behave. What ammo did you have the failure with? And what FCG do you have? It could easily be that your hammer spring wasn't up to the challenge of setting off a round because everything is so new, and because new parts can take a little while to "break in". |
|
Quoted: A brand new bolt - or more accurately, new bolt RINGS - should be a VERY tight fit in any carrier. Your test with an "arm swing" is actually similar to a test to determine if the rings are worn. In this test, you simply hold the BCG bolt-down, and if the bolt slides out of its own weight, the rings are worn. A new bolt/new rings should NOT slide out of the carrier easily, and an "arm swing" should only get you (at best) a little movement of the bolt. Cryptic is the retail arm of Toolcraft, and they know their stuff when it comes to making carriers, so I would highly doubt that the carrier's bore is undersized, even with the coating (which Cryptic states is in the 2-3 micron thickness range). It really sounds like you have a "nice and tight" brand new BCG that behaves just like a brand new BCG should behave. What ammo did you have the failure with? And what FCG do you have? It could easily be that your hammer spring wasn't up to the challenge of setting off a round because everything is so new, and because new parts can take a little while to "break in". How many failures did you have, what kind of ammo, was the primer on the round that didn't fire dimpled like a fired casing? What trigger are you using? Did you build or buy the lower? Always use full power 556 ammo when you are breaking in new parts. There is some burnishing that needs to occur for the parts to fit together nicely, especially when the parts are from multiple manufacturers. |
|
Quoted: Without the cam pin in, the bolt should be able to spin freely inside the carrier. If it does not, you most likely have some of the coating causing the difference. Quoted: Quoted: Quoted: The bolt carriers are too tight. A build up of whatever their coating is most likely. Possibly the groove where the gas rings has buildup in it keeping the rings from fully compressing. By the way, tightness does not mean a tight tolerance. This is an example of too loose a tolerance. Tolerance means how mjch difference there is from the spec. Now much of a plus or minusthere is from the specified value. It is not how loose or tight the parts fit together. The bolt fits into the carrier just enough to fit, very tight fit. Without the cam pin in, the bolt should be able to spin freely inside the carrier. If it does not, you most likely have some of the coating causing the difference. |
|
I also don't think there is anything wrong with your parts. Get a good lube on the bolt for break-in, and get a couple hundred rounds of full power ammo down the pipe before declaring anything wrong.
I do fully extend my bolts by flicking my wrist, every time I go to re-assemble a rifle from field strip, but I don't expect a new BCG/bolt assembly to necessarily extend in that manner. Most will, with some lube, but some don't. All I have tried started extending consistently within a couple of range trips. |
|
Quoted:
Is it so tight that the bolt won't go into battery? Does the firing pin move freely in the bolt? The pin is the same as the bolt fitment in the carrier. It fits, but does not freely move. That shouldn't be a problem though because its being stuck by the hammer. It moves enough to work properly. It has to be the coating on the bolt. Just not enough gas pressure to push the bolt into full battery. Thanks for your response |
|
Quoted:
Without the cam pin in, the bolt should be able to spin freely inside the carrier. If it does not, you most likely have some of the coating causing the difference. Quoted:
Quoted:
Quoted:
The bolt carriers are too tight. A build up of whatever their coating is most likely. Possibly the groove where the gas rings has buildup in it keeping the rings from fully compressing. By the way, tightness does not mean a tight tolerance. This is an example of too loose a tolerance. Tolerance means how mjch difference there is from the spec. Now much of a plus or minusthere is from the specified value. It is not how loose or tight the parts fit together. The bolt fits into the carrier just enough to fit, very tight fit. Without the cam pin in, the bolt should be able to spin freely inside the carrier. If it does not, you most likely have some of the coating causing the difference. So with the cam out, the bolt does spin. I can hear a very very faint grinding sound when i spin it. |
|
Quoted:
Are those shiny gold and black coatings on the inside of the carrier where it would normally be chromed? If they are, thats most likely the problem. Did you lube all parts before installing/firing? I'm sure even these parts with the blingy type finishes would still require lube, right? I would call Cryptic and ask them whats up and how to lube. Yes they are. I did both a non lubed and lubed test on the coatings. In both cases, there was a failure to fire. The failure was caused by the primer not being struck hard enough. I threw a mil-spec bolt in and had absolutely no issues. |
|
Quoted:
Bolt and carrier drawings are available on the web. Get the drawings and see if their dimensions are in spec. They say their BCG’s are Toolcraft and chrome lined to mil-spec. They don’t say who applied the chrome. They also say their coating is 2-3 microns. I can’t imagine that would be a problem. It sounds like you need to follow the usual troubleshooting for FTF. Check firing pin protrusion. What kind of primer strike did you get? Did the bolt fully close? Take off the o-ring. Reduced hammer spring is certainly a possible cause especially with some primers. Springs most likely the culprit now that I'm reading these posts! Thanks! |
|
Quoted:
A brand new bolt - or more accurately, new bolt RINGS - should be a VERY tight fit in any carrier. Your test with an "arm swing" is actually similar to a test to determine if the rings are worn. In this test, you simply hold the BCG bolt-down, and if the bolt slides out of its own weight, the rings are worn. A new bolt/new rings should NOT slide out of the carrier easily, and an "arm swing" should only get you (at best) a little movement of the bolt. Cryptic is the retail arm of Toolcraft, and they know their stuff when it comes to making carriers, so I would highly doubt that the carrier's bore is undersized, even with the coating (which Cryptic states is in the 2-3 micron thickness range). It really sounds like you have a "nice and tight" brand new BCG that behaves just like a brand new BCG should behave. What ammo did you have the failure with? And what FCG do you have? It could easily be that your hammer spring wasn't up to the challenge of setting off a round because everything is so new, and because new parts can take a little while to "break in". Thanks for the response! The "arm swing" was just habit, I was just trying to explain the tightness of the bolt. After reading your response, i'll throw the stock springs back in and give them another go. Thanks again! |
|
Quoted:
I also don't think there is anything wrong with your parts. Get a good lube on the bolt for break-in, and get a couple hundred rounds of full power ammo down the pipe before declaring anything wrong. I do fully extend my bolts by flicking my wrist, every time I go to re-assemble a rifle from field strip, but I don't expect a new BCG/bolt assembly to necessarily extend in that manner. Most will, with some lube, but some don't. All I have tried started extending consistently within a couple of range trips. Thanks! Going to put the regular springs back in and give it a go. The flick is just a habit, and was a way for me to describe the tightness of the bolt. |
|
Also, clean the snot out of the BCG and then lube the ever lovin' crap out of it. Make sure you clean and then lube the bolt space in the carrier and inside the bolt where the firing pin rides.
New parts are usually coated with some sort of protective material (which is NOT a gun lube), and all new parts should be very thoroughly cleaned when received. When assembled, new parts should be very thoroughly lubricated. The "grating" you felt/heard was the bolt rings, and that's a NORMAL indication. But the firing pin should have a smooth, sliding fit within the bolt, new or old. This is why I think you need to deep clean the assembly, and particularly the inside of the bolt. |
| Just call JP and see if they will swap you for a stronger hammer spring and that would likely resolve your light strike issue. Measuring the protrusion of the the firing pin should be done. I seem to recall a firing pins spec as minimum (.028") and maximum (.036") protrusion. |
AR Sponsor