The "rails" you have circled in green are the cam pin track and in fact if you drop a 180 BCG into the upper receiver the BCG will rattle around uncontrolled until you install the charging handle which rides along the lower opening of the ejection/charging slot and will align things close enough to close the bolt. There is still lots of play in the BCG until the guide rods are inserted into the front trunnion at which point the cam pin has a few thou of clearance from the cam pin track. Only once the rear guide rod retaining plate has been captured into the lower receiver by closing the upper/lower assembly do the guide rods become fully stabilized on both ends. At this point the cam pin is not resting on the cam pin track and the bolt handle is not resting on the the ejection slot but contact between pin/track or handle/slot may be initiated by applying rotational force to the bolt handle. The cam pin and bolt handle act more like over travel stops preventing excess BCG rotation during cycling but there is not constant contact between the BCG and receiver.
Sterling Arms R18 MK3
- Thread starter Horilka
- Start date
I am pretty certain that there is a recess in the top of the Mk3's Barrel Trunion to secure the front of the Guide Rod Assembly. The rear is secured against the Lower Receiver's Rear Wall when the rifle is closed up.
If you were to evaluate accuracy of a new action properly, you would need to make few tests single feeding manually, slowly closing the action and compare that to a normal operation so see if automatics introduces issue during feeding/bolt seating/closing. Just saying. It might be quite time consuming endeavor.
Maybe that's how they do it where you are from, but in my world (trained by the Canadian Army) you group a rifle using it in its normal semi-automatic mode. What is the point of determining intrinsic accuracy by hand-loading single rounds when the rifle will never be fired in that manner during a normal course of events? Besides which, I don't have the time for hand-loading a semi-automatic firearm.
I will be firing 5 and 10-round groups from 100m using a zeroed 10x Optic. I may even go hog-wild and mount a 5-25x, as I am a bit of a magnification slut. Anyhoo, that's what I understand so that's what I'm a gonna do! I reckon YMMV....
I will fire a bunch of groups with my latest batch of Federal 55gr FMJ ammo and then with some Federal 62 gr FMJ ammo. That ought to satisfy my buddy Horilka. I will also fire some Match ammo if I can acquire some from Cabelas without breaking the bank. Watch and shoot.....
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Maybe hire Mark and pay him, provide your specific ammo.
He is doing everybody a favour and the way he does it should be up to him.
Maybe it would be better if CGN stopped being such a neurotic place where everyone is instantly expecting personal insults instead of technical discussion of technical problems, but well it is what it is.
No, I didn't mean to imply that anyone needs to do any extra favors, invest any effort or money or somehow needs to be told on what to do. If it appears to read that way, well, I didn't mean it, probably translation of nuances is not my strong suit.
As for an evaluation of a change in a design of a gas gun "where I am from" - yes, it would be beneficial to make sure that cycling automatics of a new energy and/or geometry does not reduce precision of the overall rifle, such that test grouping with manual loading would give you a baseline of what barrel and general harmonics of the rifle can do and compare that to result of fully cycling rifle. But hey in "where I am from" we don't usually consider any chunk of 6061 with breaking piston rods and pins falling out to be a rifle worth producing.
No, I didn't mean to imply that anyone needs to do any extra favors, invest any effort or money or somehow needs to be told on what to do. If it appears to read that way, well, I didn't mean it, probably translation of nuances is not my strong suit.
As for an evaluation of a change in a design of a gas gun "where I am from" - yes, it would be beneficial to make sure that cycling automatics of a new energy and/or geometry does not reduce precision of the overall rifle, such that test grouping with manual loading would give you a baseline of what barrel and general harmonics of the rifle can do and compare that to result of fully cycling rifle. But hey in "where I am from" we don't usually consider any chunk of 6061 with breaking piston rods and pins falling out to be a rifle worth producing.
You can rest assured that I did not infer any personal insult from your initial post regarding accuracy testing. Perhaps I was too abrupt with you - if so, I apologize for my terse tone. I simply do not understand what benefit is to be accrued from comparing the accuracy of handloaded rounds versus those which are mechanically-loaded by the cycling action. If accuracy is abysmal (>2 MOA) then it doesn't really matter what the Barrel is capable of when not disturbed by the moving Bolt Carrier Assembly and Piston/Rod Assembly. At that point, accuracy is clearly unacceptable and something will have to change in order to achieve better results. I'm no Design Engineer, so I don't have a clue how one would go about determining a fix to that particular hypothetical. I reckon the R18 design team will cross that water if and when they get to it. On the other hand, if accuracy is acceptable (<2.5 MOA) then great - the smaller the group sizes the better! But again, I faiil to see how knowing what the Barrel is capable of under false circumstances can help to further improve acceptable accuracy. Sorry, but I reckon I am either tired or simply to dense to understand the relevance of the hand-loading that you recommend. I probably won't help me if you explain it further, but you are welcome to try if you'd like....
PS. We don't consider any chunk of 6061 with breaking piston rods and pins falling out to be a rifle worth producing where I come from either....
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Disconnecting the entire reciprocating mass and attachment of the gas system as well as non-floated elements of the upper (like hand guards) and single feeding rounds into the chamber would in theory and likely practice, provide the best yielding of what the mechanical accuracy potential of the barrel with any given ammunition is.
If it shoots 2.5 moa in that arrangement and 2.5 moa when shooting semi auto as designed, the limitation isn't the workings of the action throwing things off.
It is a 'nice to know' metric if one was to diagnose an issue with either ammunition or a rifle, but ultimately not something many would invest in the time and energy to seek data on.
I've done it with ARs in the past, and interestingly - gas or no gas, on that platform it has minuscule to no effect.
If it shoots 2.5 moa in that arrangement and 2.5 moa when shooting semi auto as designed, the limitation isn't the workings of the action throwing things off.
It is a 'nice to know' metric if one was to diagnose an issue with either ammunition or a rifle, but ultimately not something many would invest in the time and energy to seek data on.
I've done it with ARs in the past, and interestingly - gas or no gas, on that platform it has minuscule to no effect.
We know this from the TACOM.videos. All that remains to be seen is whether the lower sides of the Mk3 Bolt Carrier actually slide against the interior walls of the Upper Receiver as the action cycles, as is the case with the MCX. I will have the answer to that question later today, with the arrival of a Test Rifle for my review.
Good catch, looks like they just AR180B'd it. I hope they bring the collapsible and folding stocks.
I haven't seen it mentioned either but since the bolt and gas system appear to be chrome I would guess that. Also since they state numerous times that they are making it to international standards Chrome makes the most sense as that is still the military standard.
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