View Full Version : Vertical stringing M305

01-04-2013, 06:58 PM
I shot my 305 today in relatively cold weather (-5C), this is first time I have had a problem with vertical stringing.I have shot this rifle quite alot in the past without this issue. The group had less than a inch horizontally, but 4 inches vertically at 100 yds. The POI would start high and string low. The rifle has a scope mounted on a ARMS #18 mount. I don't suspect the scope mount or rest setup at this time. The gas band is tool tight at 6 O'Clock. I was test shooting 150g Hornady FMJ over 38.9g of Varget for the first time. Could the load be responsible in any way?

01-04-2013, 11:26 PM
Could be a multiple factor.
1) Cold temp
2) Low powder charge.
3) Rapid heating of a cold barrel with the gas lock too tight.

Next time you notice this try flipping your gas lock around so that it has some room to breath. It should solve the problem.

01-18-2013, 04:39 PM
I tested 150 g FMJ with 42g of 4064, -10C.Loaded rounds singly over a empty mag at 100 yds . I had taken the rifle apart and found a rub mark on the barrel from the cylinder assembly.I think the gas cylinder lock is too tight ( Thanks Satain). I have read that some guys relieve the stock to give better clearance behind the stock ferrule (#62 m14 schematic) wrt the front band (#22). Anyone done this?

01-18-2013, 05:26 PM
Barrel heating up would be my guess.

01-18-2013, 05:30 PM
Seems like it, but any ideas why this would be exaggerated in colder weather? I haven't had this issue in the warmer months that I recall.

01-18-2013, 07:20 PM
I will ask the doc after dinner tonight and post back later or better yet let him speak on it.

01-18-2013, 07:26 PM
Well on a cold barrel you can expect to have some deviation of FPS's due to reduced pressure etc. It'd be interesting to see if there is any significant changes if you wait, say, 5 minutes between shots to remove the heat variable.

01-19-2013, 02:49 PM
Could you post up and tell me if your powder is tempature dependent?
As he was telling me that certain powders effect accuracy depending on the powder is stable at that tempature. Something about not ignating at the same time every time.
So he then went on to say that it is either heating up and gas lock tension or unstable powder at those tempatures that you are shooting.
He would also like to appoligize for not being able to come on because he is still taken care of his son and dosn't really have enough time.

01-19-2013, 06:02 PM
Satin- Thanks for he help!-Well I tried Varget with a light load, and the pictures above were with
IMR 4064. I will try the Varget again with a higher load. I was hesitant to use Varget as I read it pounds the gun- I understand from your earlier posts that you get good results with fairly heavy loads? ( compared to my data tables anyway).
I am not sure about the temperature stability of IMR 4064- but I think Varget is supose to be stable. I tried to turn the gas lock around but it was too loose and would require shims- maybe I will make some coke can shims as I do not have any proper ones.

01-20-2013, 02:03 PM
Yep sounds like you need a shim set. Also if you go back on that other site I had a write up on what worked well under all conditions.
The powder I use:
With 168gr Serria Match Kings and CCI hard primers. Sorry I froget the excat numbers as I since drop that rig with a friend who loved it. But if I remeber it I used 43.5 grains of powder for best resualts.

03-06-2013, 09:16 PM
I had the same problem with mine, however, not quite to this extent. I shimmed/fliped my gas lock and voila: much nicer grouping. I can attest to VARGETs temp stability. I use it almost exclusively now in my .22-250, .243 and all my .308s. I use my double duty coyote/target rifle all year round and my zero does not change from say shooting in July to shooting in January (read: neglidgable up to 200 meters).