I have a question about shimming the gas system on my norinco m305. I guess my flash hider is welded on. I was thinking about making a puller but then it occurred to me, Could I not just shim it between the stock and the band? I tried it out (I've not shot it, just a test fit) w/ a washer that I thinned out to a good thickness so the gas lock snugs up at about 5:30 or so. my band is now tight and I didn't have to reef the gas lock to 6:00. just moderate pressure. It seems like a reasonable work around for those of us with welded flash hiders who don't want to butcher their rifles by hammering it off (saw a video haha), and don't have immediate access to a puller or# cash for a gunsmith to do it. Would this be acceptable? Sorry if this has been brought up before. I had a quick look in the threads.
m305 gas shim location alternative?
- Thread starter C.308
- Start date
Short answer is no, that will not work at all. For a better explanation than i can offer, google "m14 stock ferrule clearance". There's supposed to be 1/16" gap between it and the rear of the GC assembly. Any contact other than the underside of that ferrule will kill accuracy.
The proper way to shim is over the barrel, at the rear, between that plate and the GC. This is tried tested and true. Getting that flash hider off is the first necessary step in tweaking any of these rifles.
The proper way to shim is over the barrel, at the rear, between that plate and the GC. This is tried tested and true. Getting that flash hider off is the first necessary step in tweaking any of these rifles.
I am looking for a rifle that still has the flash hider welded on so that I can make a how-to video to show an alternate method for removal. There is no hammering involved and no charge. PM me if you'd like to have your flash hider removed.
Just cut one side of the the shims and slip them over the barrel between the barrel band and the flange that the band rests against. Shimming is only a temporary measure since they wear out quite quickly (500-1000 rounds is my experience) and you will see your groups start to deteriorate. The best solution is to find a gas lock that tightens correctly or perhaps get one of the Dlask adjustable gas locks but you will have to remove the flash hider to replace the existing gas lock.
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thanks for all the replied and advice. im brand new to the m305 game. I thought this would make a more natural joining of the parts as the ferrule would press against the gc assly. and the stock would press on the shim which toches the ferrule. but I've learned over time that no matter what makes sense in my twisted mind, I shouldnt question what has been proven to work (ive been proven wrong before hah) Ill try to get that flash hider off! Thanks all!
Travis Bickle
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- Upper Lower Middle Alberta
A lot of guys don't understand that the whole purpose of shimming the gas system is two fold.
One is to stop it from rattling when you fire the rifle which messes up the harmonics of the barrel when firing. This one is more common knowledge.
Two is because you don't want the gas system (specifically the front band) to contact the stock ferrule. There should be a visible gap between the ferrule and the front band with only the bottom lip of the front band hooked under the stock ferrule. This is really to be done in conjunction with properly bedding your action. Keeping upward pressure on the front of the barrel so that there is a steady pressure pushing the stock downward into the lip of the front band once rifle is assembled. Then shaving off the handguard bottom edge sides so there is no contact on the stock is another job to perform as well.
Properly bedding an M14 is one of the most nail biting experiences I've ever attempted but if I can do it anyone can.
One should also dremel out said stock ferrule to ensure that the gas cylinder is not touching the sides of it inside the stock channel.
None of this is of much relevance unless you spot weld your gas cylinder to the front band so it's rock solid all one piece either (some call it "unitizing" because it sounds technical and impressive but really you're putting 3 spot welds on the gas cylinder to weld it to the front band is all)
Though much of this sounds daunting, it's actually achievable with no special tools (aside from a buddy with a welding setup and some marine tex for bedding and a castle nut pliers for $7 on e-bay).
You can bore out the weld spots with a drill to weaken them, heat up the flash hider with a torch, brace it well in a vice and use a 2x4 stubb and a hammer to knock the norc flash hider off if you really want to. If you're going to shim your unitized gas system properly I recommend doing this and shim it until the Gas Cylinder Lock gets hard to tighten at around the 5 o'clock position. You want to have to force that ####er in hard past that.
Do this and you will see substantial accuracy increases compared to a rack grade Norc. I would put mine up against a Springfield M1A any day all day now and it costs me almost nothing to get it there (except time) from used M305 off the EE
One is to stop it from rattling when you fire the rifle which messes up the harmonics of the barrel when firing. This one is more common knowledge.
Two is because you don't want the gas system (specifically the front band) to contact the stock ferrule. There should be a visible gap between the ferrule and the front band with only the bottom lip of the front band hooked under the stock ferrule. This is really to be done in conjunction with properly bedding your action. Keeping upward pressure on the front of the barrel so that there is a steady pressure pushing the stock downward into the lip of the front band once rifle is assembled. Then shaving off the handguard bottom edge sides so there is no contact on the stock is another job to perform as well.
Properly bedding an M14 is one of the most nail biting experiences I've ever attempted but if I can do it anyone can.
One should also dremel out said stock ferrule to ensure that the gas cylinder is not touching the sides of it inside the stock channel.
None of this is of much relevance unless you spot weld your gas cylinder to the front band so it's rock solid all one piece either (some call it "unitizing" because it sounds technical and impressive but really you're putting 3 spot welds on the gas cylinder to weld it to the front band is all)
Though much of this sounds daunting, it's actually achievable with no special tools (aside from a buddy with a welding setup and some marine tex for bedding and a castle nut pliers for $7 on e-bay).
You can bore out the weld spots with a drill to weaken them, heat up the flash hider with a torch, brace it well in a vice and use a 2x4 stubb and a hammer to knock the norc flash hider off if you really want to. If you're going to shim your unitized gas system properly I recommend doing this and shim it until the Gas Cylinder Lock gets hard to tighten at around the 5 o'clock position. You want to have to force that ####er in hard past that.
Do this and you will see substantial accuracy increases compared to a rack grade Norc. I would put mine up against a Springfield M1A any day all day now and it costs me almost nothing to get it there (except time) from used M305 off the EE
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Thanks for the detailed information. Sorry i havent come back to this for a little while. Ive been exploring some other projects. I would like to get started on my m14 project again though. All i have done so far is replace the oprod spring guide. Its a very noticable difference in the movement of the action!
I actually sold my long barrelled m305 and managed to get my hands on a DA socom 18 with a threaded flash hider. Much easier to work with. (I am a mechanic and have the means to remove the flash hider according to the above instructions but I just would rather not mess with it.)
I now understand the idea of shimming the gas system and the importance of keeping the band away from the stock ferrule. My next step will probably be to upgrade any vital parts I can to usgi and properly unitize and shim my gas system (although it seems pretty good on this rifle compared to the last one.) I would only consider bedding the rifle in the stock if i could get my hands on a nice usgi synthetic stock and even then probably not. I really only plink at the range so for my needs its probably more trouble than its worth. (Then again, why would i upgrade to usgi parts in that case? I dont know haha because i want to is the best answer. Bedding the stock seems like a more permenant and possibly value reducing modification if not done right...and i have zero experience with it)
Im just going to keep my eyes peeled for parts and then once i get a deal or two I will take it to the next step. Thanks again to everyone for all of the advice!!
I actually sold my long barrelled m305 and managed to get my hands on a DA socom 18 with a threaded flash hider. Much easier to work with. (I am a mechanic and have the means to remove the flash hider according to the above instructions but I just would rather not mess with it.)
I now understand the idea of shimming the gas system and the importance of keeping the band away from the stock ferrule. My next step will probably be to upgrade any vital parts I can to usgi and properly unitize and shim my gas system (although it seems pretty good on this rifle compared to the last one.) I would only consider bedding the rifle in the stock if i could get my hands on a nice usgi synthetic stock and even then probably not. I really only plink at the range so for my needs its probably more trouble than its worth. (Then again, why would i upgrade to usgi parts in that case? I dont know haha because i want to is the best answer. Bedding the stock seems like a more permenant and possibly value reducing modification if not done right...and i have zero experience with it)
Im just going to keep my eyes peeled for parts and then once i get a deal or two I will take it to the next step. Thanks again to everyone for all of the advice!!
Let's take this a little bit further......
Shimming is not just performed to tighten up the assembly for improved barrel harmonics and shimming is not a step to consider when addressing stock fitment at the ferrule. If you are shimming the gas system to affect the gap at the stock ferrule...... Stop. This is not the way. Modify the stock at the ferrule by removing it and adding or taking away untill the ferrule has the 1/16" gap. This can be a stand alone modification or as a key step in a full bedding job. I did a write up and was in the stickies.... not sure if it still is.
The primary reason for shimming or even better roll peening the barrel's gas assembly buttress forward.... is to properly and precisely align the has port with the cylinder. THAT is the primary purpose of shimming the gas system forward.
When i build an M14 rifle and select the gas system i want to use with the barrel i have already chosen, I slide the cyclinder into place and use the gas port alignment tool to achieve precise and optimal position of the cylinder. Measuring the gap between buttress and gas system assembly I can now decide exactly what shims I need or I can decide if roll peening the buttress bearing surface forward is the better route. Too much gap and shims are required but I hate using shims and prefer the permanent approach.
So once the gap behind the assembly is addressed and the cylinder/barrel port alignment is dead on, we now find a gas lock that hand tightens at 4:30 or 5:00 in it's rotation from top dead center.
that's the way it gets done if you want permanent , professional results that "will" improve the performance of your rifle.
Shimming is not just performed to tighten up the assembly for improved barrel harmonics and shimming is not a step to consider when addressing stock fitment at the ferrule. If you are shimming the gas system to affect the gap at the stock ferrule...... Stop. This is not the way. Modify the stock at the ferrule by removing it and adding or taking away untill the ferrule has the 1/16" gap. This can be a stand alone modification or as a key step in a full bedding job. I did a write up and was in the stickies.... not sure if it still is.
The primary reason for shimming or even better roll peening the barrel's gas assembly buttress forward.... is to properly and precisely align the has port with the cylinder. THAT is the primary purpose of shimming the gas system forward.
When i build an M14 rifle and select the gas system i want to use with the barrel i have already chosen, I slide the cyclinder into place and use the gas port alignment tool to achieve precise and optimal position of the cylinder. Measuring the gap between buttress and gas system assembly I can now decide exactly what shims I need or I can decide if roll peening the buttress bearing surface forward is the better route. Too much gap and shims are required but I hate using shims and prefer the permanent approach.
So once the gap behind the assembly is addressed and the cylinder/barrel port alignment is dead on, we now find a gas lock that hand tightens at 4:30 or 5:00 in it's rotation from top dead center.
that's the way it gets done if you want permanent , professional results that "will" improve the performance of your rifle.
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For verification of gas port alignment would the proper diameter punch/ pin suffice? I mean to just pass it through to confirm that it lines up, or is there more to it. Im not expecting a walk through on the procedure as im sure you've earned your skills and knowledge.
There is so much more to this rifle than i ever would have thought! Down the rabbit hole I go, I guess. Haha.
There is so much more to this rifle than i ever would have thought! Down the rabbit hole I go, I guess. Haha.
Yes, that's the beauty of this forum for those hunting for m14 info, and though i don't post much anymore, I have always felt the need to freely share the knowledge. A hole transfer punch that just fits the diameter is a good tool. You don't want it too tight fitting as who knows if that will disturb the chrome lining at the gas port inside the barrel. For those without a transfer punch, a long shank end of an appropriate size will also do in a pinch if you have bits that long. Mine was made by badger ordnance some time back but is a handy tool.
insert pin , verify it passed thru to barrel and while it is in place, use a caliper to measure the gap between buttress and gas band plate. I usually do this procedure without the plate and then do the math to subtract it's thickness after measuring it also with a caliper. Being a former smith I had lots of parts to choose from so would mix and match gas locks and gas band plates for optimal size/fitment. Something I realize is not really practical for norinco rifle owners themselves.
With a usgi pattern barrel, heavy, medium or standard profiles, options improve as the parts that fit these barrel threads are able to be sourced and tried for best fitment. Again though.... the rabbit hole LOL
welcome to the affliction
insert pin , verify it passed thru to barrel and while it is in place, use a caliper to measure the gap between buttress and gas band plate. I usually do this procedure without the plate and then do the math to subtract it's thickness after measuring it also with a caliper. Being a former smith I had lots of parts to choose from so would mix and match gas locks and gas band plates for optimal size/fitment. Something I realize is not really practical for norinco rifle owners themselves.
With a usgi pattern barrel, heavy, medium or standard profiles, options improve as the parts that fit these barrel threads are able to be sourced and tried for best fitment. Again though.... the rabbit hole LOL
welcome to the affliction
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I read on another site that guys use teflon tape to shim the system. Then they replace it every year or two depending how much they shoot. I tried it on mine and it worked good for something I just had sitting around the house anyways. Also as a bonus no need to remove the flash suppressor.
I've never heard of that one......
Lets look at all this another way.
You want performance from your rifle right? get it as repeatable accurate as you can?
So when the gas system modifications take place, these are not done just to tighten up the assmebly and this is going to magically improve barrel hamonics and tighten up your groups right?
Well maybe.....
Let's stop for a minute and think about all this. Gas port alignment should be the primary reason for applying shims to that assembly. Allowing for optimal gas flow/dwell time. This then transfers to optimal and repeatable function of the gas piston. This then translates to repeatable travel of the oprod and bolt in and out of battery. For a battle rifle this really isn't required but for those who are anal about squeezing out accuracy, shim for the right reasons. Any other reason is just doing a modification that doesn't "need" to be done. A loose gas system on a GI m14 battle rifle would be a normal thing from what i understand from the gunny's comments I have followed.
Shimming is one step in optimal alignment of the ports and then rotational alignment by tightening the barrels splineways to center the cylinder on axis to the gas port.... then a nice tight gas lock turning hand tight at about 4:30 and tool tight at 6:00 and last tig weld unitizing the band to the cylinder to give the stock a fixed mating surface for ferrule and gas band lip.
shimming is a fun thing to do at clinics but I fear many folks are not realizing that it is but one step in accurizing the gas system and often done with zero regard for the gas port alignment.... which essentially is shimming's sole purpose.
Lets look at all this another way.
You want performance from your rifle right? get it as repeatable accurate as you can?
So when the gas system modifications take place, these are not done just to tighten up the assmebly and this is going to magically improve barrel hamonics and tighten up your groups right?
Well maybe.....
Let's stop for a minute and think about all this. Gas port alignment should be the primary reason for applying shims to that assembly. Allowing for optimal gas flow/dwell time. This then transfers to optimal and repeatable function of the gas piston. This then translates to repeatable travel of the oprod and bolt in and out of battery. For a battle rifle this really isn't required but for those who are anal about squeezing out accuracy, shim for the right reasons. Any other reason is just doing a modification that doesn't "need" to be done. A loose gas system on a GI m14 battle rifle would be a normal thing from what i understand from the gunny's comments I have followed.
Shimming is one step in optimal alignment of the ports and then rotational alignment by tightening the barrels splineways to center the cylinder on axis to the gas port.... then a nice tight gas lock turning hand tight at about 4:30 and tool tight at 6:00 and last tig weld unitizing the band to the cylinder to give the stock a fixed mating surface for ferrule and gas band lip.
shimming is a fun thing to do at clinics but I fear many folks are not realizing that it is but one step in accurizing the gas system and often done with zero regard for the gas port alignment.... which essentially is shimming's sole purpose.
