Gas Piston and Op Rod Alignment Question

Pr589

Pr589

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Hey folks,

I just noticed that the Op. Rod and gas piston on my M305 are not well aligned. See pic below. The questions I have are:
- Is this a safety or durability concern?
- Will it cause precision issues? The rifle shoots 1.5 MOA regularly and if I'm lucky, a little less.
- If it is a concern, what do I do about it? I'm thinkin' that this is due to over-indexing of the barrel but that's just my guess.

This is a pic of the head of the Op. Rod with the rifle upside down. The bolt is locked back. For those not familiar with Blackfeather stocks, the Op. Rod is sitting in the Blackfeather Op. Rod Guide.
You can see the "imprint" of the gas piston on the head of the Op. Rod. You can see it is 1mm to 2mm off centre.

IMG_2041_zps845712ff.jpg
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Not a safety concern and a non issue as far as a rack grade rifle.
But, it can lead to deflection forces back at the tab of the oprod, and this is does cause wear of tab and oprod track in receiver.... After a long time of use mind you.

NM conditioning the barrel under the oprod guide and positioning it for piston/oprod alignment is a desireable modification.

For this and other simple do it yerself tweaks/mods... Scott duffs m14 owners manual and jerry kuhnhaussen's 30 cal service rifle shop manual... Not as good as a clinic with myself or Hungry.... But useful books for the at home M14 tuner. ;)
 
So no safety issues, and only a small durability concern - check.

Is this lack of alignment due to the indexing of the barrel and would it affect the ability of the rifle to shoot groups?

Looks like I need to sign-up for the Burlington M14 clinic. Woo hoo
 
The Blackfeather op rod guide...was it installed by replacing the pin? The picture shows that it is very evident it is not vertical. Were the barrel sights vertical when you bought?
 
Sobo - The pin was replaced. I might be wrong but I think the installation is OK. You can't judge vertical alignment from the picture since the barrel was canted to get light where I needed it for the photo. What I believe is important for the Op. Rod Guide (ORG) installation is the vertical alignment between the "pillars" in the receiver and the ORG. As installed, this ORG and the receiver both slide smoothly into the stock with no force required and neither shows any anomalous wear along the sides of the metal. Also, the ORG bolt hole is perfectly aligned with the hole in the stock. To me this indicated that the ORG was properly fitted.

I had thought that I'd messed up the install initially then I got to thinking. If I twisted the ORG and the Op. Rod to produce better alignment, the stock and ORG would not slide into the stock, and would bind. To me this implies that the alignment issue comes from the gas cylinder/piston being misaligned. Since the gas cylinder system is pinned, it seems to me that the whole barrel would have to be rotated to the correct alignment - which is why I suspect that this is an indexing issue.

Then again I could be wrong....
 
The reason I commented was that the picture clearly shows the ORG, as installed has a definite cant to the left as evidenced by the distance between the face (left and right) of the guide and the handguard. That is why I asked if the front sight is also out of alignment. If you set the rifle on a table, so that it is siting vertical, and using a wall or some other vertical reference, you can quickly determine if the front sight is out of alignment. Based on the impact of the piston on the Op rod, if the barrel is not indexed properly, you will quickly see it with the sight.

If you are concerned about the gas block alignment, turn the rifle upside down and allow it to set squarely on the table. Using a builders square, set it on table beside the gas block. You will quickly see if there is an issue.

I am not familiar with the ORG you installed, but to install, do you used the same roller pin slot in the barrel? You had mentioned screws to fasten. Are there screws on either side of the apparatus which fasten to the barrel? It could be that the manner in which the screws fasten to the barrel could be one possible cause. I'm thinking more about the possibility of the ORG rotating on the barrel axis if the screws are not matching the barrel exactly or they are torqued unevenly during installation.

The principle is similar to how a scope rotates if the screws are not evenly torqued as they are being fastened down. Also, i noted on a website showing the installation of this thing that it appears to be three set screws. Is there a roll pin which has to be installed as well? When you finished installing, did you check the alignment of the op rod to the piston (without the springs) before shooting? This would have been evident that things were not aligned properly.
 
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Sobo - thanks for your observations on my post.

I took a look at the handguard alignment and it is canted to the left (looking from the receiver towards the barrel). While I couldn't do the exact test that you suggested because the rifle is scoped and has a mount that would interfere, I did something similar.

I turned the rifle upside down and used a set of bubble levels,one against the side of the Op. Rod Guide (which was validated as being vertical), and the second on the bottom of the front sight, which was indeed leaning to the left (looking from back of rifle). Seems conclusive to me that it's an indexing issue.

In regard to the screws and pins. There is a roll pin that secures the ORG (it's optional but I used it anyway), in addition to the 3 set screws. During install I incrementally tightened each of the screws but didn't use a torque screwdriver or a similar tool to measure. I'm thinking that this would only produce a small twist where we're likely looking at 5 to 10 degrees of twist. I didn't check the Op. Rod/gas-piston alignment during install. Perhaps this should be an explicit check that Frank adds to his installation manual, before slathering on Locktite. I instead relied on clearance between the sides of the ORG and the bedding pillars of the stock, as well as using the corresponding main bolt holes on the stock and ORG.

I don't think the alignment issue is stock or ORG related. By doing your tests I'm increasingly convinced its due to indexing.

Thanks for the advice. You've moved me down the road. Now we'll see if Barney can sort me out at the Burlington M14 clinic.
 
Miss cut spline ways or in proper timing of said rifle. Take a picture of the feed ramps and post them. This will tell you if it's the barrel's timing that is out or if it's improper spline way cuts.
To bad the maker of said op-rod guide could not find a way to correct this issue like one can do with the OEM guide.
 
Crack Feather - Thanks for weighing in.

See the pic of the feed ramps below. The rifle has had no FTF issues.

Also, help me understand how the OEM guide could help correct alignment issues. Seems to me it was attached to the barrel by friction and the roll-pin, same as for the Blackfeather ORG. Perhaps I could use the same method for correcting alignment.

Chamber_zpsd1c7e3eb.jpg


Thanks
 
Granite,

Thanks for the input. The ORG is rock solid. If I twisted the ORG to bring the Op. Rod into alignment with the piston, it would be out of alignment with the receiver. From the tests I've done on the suggestions of other posters I'm confident that either the barrel is over-tightened or as suggested by Crack Feather, the splines on the barrel which secure the gas cylinder are perhaps machined out-of-alignment.

I found the alignment issue when I was inspecting the rifle for something that might be causing 1st round flyers. These flyers open my nice 1 inch groups to 1.5, 2 or sometimes 3 inches. It's driving me nuts to see these nice 1 inch clusters plus one hole 1.5 inches high.
 
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sorry guys it was my failed attempt at humour LOL

too me, i would say your barrel needs indexing ever so slightly.
evidenced by the of center impressions the end of the piston tail is leaving on face of oprod tube and the fact that the handguard appears slightly off from the oprod guide.
is your front sight also slid over to one side from center to get a zero?

however, out of spec barrels are known to exist, as are flash hiders, gas assemblies, ect ect.
true indexing is not based on feed ramps or barrel splineways and especially not the oprod guide pin slot.
indexing , and all other barrel dimesions as far as splineways ect go are based on gas port location.
so , ideally a perfectly indexed barrel has the gas port at the true opposite of top dead center.
barrel dimension checks should start with the gas port as the "zero"
a special tool, not made anymore, allows for insertion into the gas port with the rifle upside down to check index to receiver. +/- 3 degrees is tolerance, i'm lucky enough to have such a tool hehehe

anyhow, my suggestion to the OP, is too loosen off the oprod guides set screws amd knock out the pin. leave the oprod guide in position but it should be loose enough to rotate as needed.
install action to your stock , trigger as well. don't tighten or install any black feather screws just yet
now, put your rifle in a rest so the receiver is level both ways.
use alignment bars to check index

doing it this way will rule out the blackfeather's affect on your rifle and should show you if it's an index issue or something screwy with your barrel

bottom line and the reason for my stab at humour is...... yer complaining about a rifle you claim is shooting reliable 1 to 1.5" groups at 100 ....... most guys would not touch a thing and be very happy with that ;)
 
45ACP - Thanks for the more fulsome explanation. Helpful as usual when you`re not being mysterious :)

Half the fun of these rifles is the home-tweaking, especially for us noobs:dancingbanana:. For the business members, my guess is that a big chunk of the business is due to the tweakers always trying to tease out that extra bit of accuracy. reliability, coolness or whatever.

For me I too would be happy with reliable 1 to 1.5 in. groups but while I can get this on my best 5 round groups, too often I get these warm-bore flyers that can open the groups dramatically. We might have to accept first and last round flyers as endemic to the M14 platform but I`m not yelling uncle....yet. Just to support my `claim`of 1-1.5 inch groups, see the pic below from a recent range visit.

Thanks for the help

BestGroups_zpsa97c6f6e.jpg
 
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