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Posted: 12/28/2011 3:36:43 PM EDT
| what is the relationship between bolt gap and felt recoil? reliability? and when does it damage the receiver? |
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Quoted:
what is the relationship between bolt gap and felt recoil? reliability? and when does it damage the receiver? When the bolt gap is low you have less seal on the bolt face and this can cause the rifle to short stroke also when your bolt gap is low there is more wear and tear on the rifle if it falls below .04 the roller may slap out on your receiver a bit if your rifle is bolt gaped at .21 to .25 the recoil is cut half The American hk spec for bolt gap at .04 to .020 the German spec is .04 to .025 I was told by a hk builder that went to the H&K factory himself that american rifles are bolt gaped at .018 - .020 German rifle are set at .021-.025 for want it is worth I put some +4 and +6 rollers in my rifle and love it |
| My situation was that the first round in a magazine fired, but the second one would chamber but not fire. My gap was on the high side of .30 mm Swapping different locking pieces and bolt didn't change the gap by much in my case.. Thanks for giving me insight on where to set the gap to. I will aim torwards .21-.25mm |
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My situation was that the first round in a magazine fired, but the second one would chamber but not fire. My gap was on the high side of .30 mm Swapping different locking pieces and bolt didn't change the gap by much in my case.. Thanks for giving me insight on where to set the gap to. I will aim towards .21-.25mm I was told if you go over.025 you can get light strikes sounds like you need some minus rollers 
swapping lock pieces will not change your bolt gap sound like you need some - 2 or -4 rollers till the rifle settles then after 300 rd put he reg 8mm rollers in your good to go most h&k rifles settles .01 to .05 after 300 rds locking pice may vary a bit but not going to change that much hope this helps |
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Quoted:
what is the relationship between bolt gap and felt recoil? reliability? and when does it damage the receiver? The mechanics of this system are so misunderstood that you are going to get all kinds of answers, and introduction to a few myths or as I like to call them "internet facts". First, lets talk about the HK specified gap of .004"~.020". Why those numbers? If you look at your BCG out of the rifle you will see the pawl on the carrier that extends to the ramp on the bolt head. There is a corresponding ramp on the underside of the pawl. The opposite end of the pawl rests on a spring. The engineers determined that the proper amount of tension on the ramps was achieved at a gap setting between .004~.020". 
Next, look at the interaction inside the bolt head. #1 is the spring tension provided by the recoil spring against the carrier which pushes against the skirt of the locking piece. #2 is the contact triangle. The roller is pressed agaist the shoulder of the locking piece, the front of the window in the bolt head, and the near angle of the trunnion. #3 is the resulting gap between the front of the carrier and the rear of the bolt head. When your gap is too low (say ZERO!) the tension from the carrier pushes directly on the rear of the bolt leaving the rollers to float, not necessarily contacting all three surfaces. In addition, because the gap is low, the spring tension on the carrier pawl is minimized and the bolt will unlock violently. In extreme cases the bolt will smash against the stock buffer so hard that the rollers will spread and dimple the rails. Guns with low gaps are also harder to cock. OTOH, when your gap is too large the pressure on the pawl is high, but the distance it travels under this pressure is very short (referred to as timing) which also results in faster opening and makes the rifle much easier to cock. The .004"~.020" was determined to be the safe zone for operation. The last and most legendary component is the locking piece (LP). The LP is the real mechanism for adjusting the timing of the rifle. The smaller the shoulder angle (40 degrees) the longer the action stays locked and the more pressure is exhausted out of the barrel, the larger the angle (60 degrees) the lock time is decreased and the action opens sooner increasing felt recoil. The LP sets the timing, the roller size adjusts the gap. Remember, gap on the DRLB action is set with the bolt resting on an empty chamber with the hammer resting on the rear of the carrier (dry fired). However when a round is chambered there is actually a gap between the bolt face and the barrel face of .005"~.009" and your gap will be very large. The bolt/barrel gap is necessary to keep the two from beating each other to death while cycling. Too many people misinterpret this and go with the "bigger is better" theory. |
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Quoted:
Quoted:
what is the relationship between bolt gap and felt recoil? reliability? and when does it damage the receiver? The mechanics of this system are so misunderstood that you are going to get all kinds of answers, and introduction to a few myths or as I like to call them "internet facts". First, lets talk about the HK specified gap of .004"~.020". Why those numbers? If you look at your BCG out of the rifle you will see the pawl on the carrier that extends to the ramp on the bolt head. There is a corresponding ramp on the underside of the pawl. The opposite end of the pawl rests on a spring. The engineers determined that the proper amount of tension on the ramps was achieved at a gap setting between .004~.020". http://i2.photobucket.com/albums/y29/Holescreek/Gunstuff/LPContactpoints1001112.jpg Next, look at the interaction inside the bolt head. #1 is the spring tension provided by the recoil spring against the carrier which pushes against the skirt of the locking piece. #2 is the contact triangle. The roller is pressed agaist the shoulder of the locking piece, the front of the window in the bolt head, and the near angle of the trunnion. #3 is the resulting gap between the front of the carrier and the rear of the bolt head. When your gap is too low (say ZERO!) the tension from the carrier pushes directly on the rear of the bolt leaving the rollers to float, not necessarily contacting all three surfaces. In addition, because the gap is low, the spring tension on the carrier pawl is minimized and the bolt will unlock violently. In extreme cases the bolt will smash against the stock buffer so hard that the rollers will spread and dimple the rails. Guns with low gaps are also harder to cock. OTOH, when your gap is too large the pressure on the pawl is high, but the distance it travels under this pressure is very short (referred to as timing) which also results in faster opening and makes the rifle much easier to cock. The .004"~.020" was determined to be the safe zone for operation. The last and most legendary component is the locking piece (LP). The LP is the real mechanism for adjusting the timing of the rifle. The smaller the shoulder angle (40 degrees) the longer the action stays locked and the more pressure is exhausted out of the barrel, the larger the angle (60 degrees) the lock time is decreased and the action opens sooner increasing felt recoil. The LP sets the timing, the roller size adjusts the gap. Remember, gap on the DRLB action is set with the bolt resting on an empty chamber with the hammer resting on the rear of the carrier (dry fired). However when a round is chambered there is actually a gap between the bolt face and the barrel face of .005"~.009" and your gap will be very large. The bolt/barrel gap is necessary to keep the two from beating each other to death while cycling. Too many people misinterpret this and go with the "bigger is better" theory. if .020 is the top for safe actions why does H&K set there rifles at .020 to .025 for german use ? |
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Quoted:
Quoted:
Quoted:
what is the relationship between bolt gap and felt recoil? reliability? and when does it damage the receiver? The mechanics of this system are so misunderstood that you are going to get all kinds of answers, and introduction to a few myths or as I like to call them "internet facts". First, lets talk about the HK specified gap of .004"~.020". Why those numbers? If you look at your BCG out of the rifle you will see the pawl on the carrier that extends to the ramp on the bolt head. There is a corresponding ramp on the underside of the pawl. The opposite end of the pawl rests on a spring. The engineers determined that the proper amount of tension on the ramps was achieved at a gap setting between .004~.020". http://i2.photobucket.com/albums/y29/Holescreek/Gunstuff/LPContactpoints1001112.jpg Next, look at the interaction inside the bolt head. #1 is the spring tension provided by the recoil spring against the carrier which pushes against the skirt of the locking piece. #2 is the contact triangle. The roller is pressed agaist the shoulder of the locking piece, the front of the window in the bolt head, and the near angle of the trunnion. #3 is the resulting gap between the front of the carrier and the rear of the bolt head. When your gap is too low (say ZERO!) the tension from the carrier pushes directly on the rear of the bolt leaving the rollers to float, not necessarily contacting all three surfaces. In addition, because the gap is low, the spring tension on the carrier pawl is minimized and the bolt will unlock violently. In extreme cases the bolt will smash against the stock buffer so hard that the rollers will spread and dimple the rails. Guns with low gaps are also harder to cock. OTOH, when your gap is too large the pressure on the pawl is high, but the distance it travels under this pressure is very short (referred to as timing) which also results in faster opening and makes the rifle much easier to cock. The .004"~.020" was determined to be the safe zone for operation. The last and most legendary component is the locking piece (LP). The LP is the real mechanism for adjusting the timing of the rifle. The smaller the shoulder angle (40 degrees) the longer the action stays locked and the more pressure is exhausted out of the barrel, the larger the angle (60 degrees) the lock time is decreased and the action opens sooner increasing felt recoil. The LP sets the timing, the roller size adjusts the gap. Remember, gap on the DRLB action is set with the bolt resting on an empty chamber with the hammer resting on the rear of the carrier (dry fired). However when a round is chambered there is actually a gap between the bolt face and the barrel face of .005"~.009" and your gap will be very large. The bolt/barrel gap is necessary to keep the two from beating each other to death while cycling. Too many people misinterpret this and go with the "bigger is better" theory. if .020 is the top for safe actions why does H&K set there rifles at .020 to .025 for german use ? Before I would give any credence to that statement I would want to know where is it published in the HK literature. Facts are only facts when they can be verified. Unsupported facts are just hearsay. There are quite a few people that run extra large gaps in the little pistol caliber weapons quite successfully and in many of them it is necessary. The little guns are much less reliant on the locking mechanism for function and in fact work really well when built as direct blowbacks. Bottlenecked cases are quite a different story. There are plenty of photos circulating on the net of rifles that discharged out of battery and the resulting damage. |
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