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Posted: 6/29/2008 5:27:12 AM EDT
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I purchased a YHM FSB/Folding Sight Post a couple of years ago and installed to what I believe was the correct specs. At the time I was using stock FH. I recently upgraded to an ARMS SIR Free Float system and when I removed the FSB I noticed that the wear pattern around the gas port on the barrel was not even. I also downgraded to some wolf ammo and now I have short stroking issues. (Bolt does not lock back after last round) I also have installed an Enidine Buffer (I believe it to be the correct size for carbine length rifles 3 5/8" length) as that is what I remember ordering. My gas key is tight and staked correctly and the gas tube (Mushroom end) looks good. I have had the YHM FSB for over two years and never experienced this problem until I started shooting Wolf Ammo 62Gr JHP. I know its not the best but it was cheap. Using the ammo did however highlight the fact that I had a gas system not functioning correctly. I believe it is due to the misalignment of the FSB. I installed the FSB leaving the stock handguard front cover. My questions are; 1) Should I remove the front HG plate as it serves no purpose with the SIR installed. 2) How do I ensure that the FSB is installed correctly? Currently, the set screws on FSB are leaving indentations just outside of the old barrel pin slots on the barrel. I am concerned that this is not correct. Any help would be appreciated. |
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Pull the gas block and check out the burn around the barrel gas port. When you go to reinstall the gas block, pencil line the barrel gas port (align this with the gas tube), and check the distance from the center of the gas port to the barrel shoulder against the center of the gas block passage against it's back edge. On some blocks, you have to keep the back of the block off the barrel shoulder a hair (thickness of a front hand guard cap). As for the Wolf ammo and the buffer, here may be your problem, and you might have to be back to the lighter stock buffer for such (if not a gas port size or chamber problem with the Wolf ammo). |
Thank you Dano. I just recently tried WOlf against my better judgment for use as plinking ammo. However, I was concerned that I might have gas system issues after my recent troubles. Previously with the same buffer and gas block installed I fired Lake City M855 ball without any incident. (3000+ rounds) I wanted to be sure before I reassemble my rifle. I have read a lot of posts concerning the inconsistency of wolf ammo and reliability issues. |
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Number 6) from Yankee Hill gas block installation instructions. www.yhm.net/store/media/2_pc_GasBlocks.pdf (6) Install the front sight or gas block assembly, being careful to align the gas tube into the upper receiver/ barrel nut assembly. If using a standard forearm slide the front sight or gas block all the way on until it hits the metal forearm cup. If you are using an aftermarket forearm DO NOT PUSH THE SIGHT AGAINST THE SHOULDER OF THE BARREL! You must leave a 1/32” gap between the shoulder of the barrel and the gas block / front sight. Be certain that the top of the front sight or gas block is in perfect alignment with the sighting line of your rear sight. A suggested way to do this is hold a common ruler across the top of the gas block and hold the firearm in the shooting position and view the ruler to see that it is parallel to your site line. |
| That is interesting indeed. If a 1/32" gap must be left then that would suggest the the alignment of the gas port on the barrel and the GB is correct. In other words I should have two concentric circles on the barrel as the gas port on the block is larger than the one on the barrel. However, I do not have that. The patterns on my barrel would indicate that the GB is too far forward. Is the 1/32" gap for alignment purposes or is there another reason for the leaving of the gap? Thank you. |
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