|August 27, 2013, 08:03 PM||#26|
Join Date: December 10, 2012
The major fault for some people with the micro groove is that it is not as accurate with cast as its predacessor was.
|August 28, 2013, 06:28 AM||#27|
Join Date: June 22, 2009
Location: South Carolina
Flintlock 50, you did not tell us what bullet and load you were using. Seeing that I am thinking of ways this could be readily duplicated.
1. shooting bullets that are way too long for the twist rate in rifle. For instance a 14" twist in 30 cal will stabilize 168 gr. just fine but 180 grains or heavier it will not.
2. shooting 30 cal bullets in 32 cal barrel will do it.
3. The bullet holes appear to be made with a pointed bullet which should not be used in a tube feed rifle.
4. I think if you tried 30.6 grains of 4895 with a Sierra 150 grain bullet for the 30-30 you will see round holes.
I have been doing a fair amount of testing on a Marlin Texan Model I picked up about six weeks back and it has been very educational indeed.
The main problem I am having is getting the cases fireformed to the chamber as the design grips the chamber wall so tightly it won't allow the shoulder to move forward to its maximum length. This is readily seen in a number of 30-30 cases I have seen have their primers backed out a significant distance above the rim on firing.
Rationale: the more a case moves when it is fired and the more a case is squeezed back to original dimensions the shorter the case life will be. Even though the 30-30 headspaces on the rim, what controls the case life is how far the shouldeer moves forward on firing and how much it is returned on sizing. You only need to have .001" clearance at the case shoulder to get the bolt into battery easily.
Setting your die to just barely move the shoulder will completely eliminate the backed out primer condition.
The best ompetition bolt gun shooters that are serious use a MO Gage to set their dies so the shoulder will not be moved back from the fired position more than .001" to .002" as they want easy closing and maximum case life due to the high cost of brass these days.
Or look at it this way, the less a case moves on firing/sizing the longer it should last.
From the drawings I have looked at it appears the min factory loaded length to shoulder and the maximum fired length to shoulder can be about .040" ! ! ! !
Best I can determine no one makes a 30-30 case gage so I rigged up a set up to where I could measure the distance to the shoulder of a unfired round, then fire them and insert them in same gage and see how much the shoulder moved forward. I use a bench inspection gage for this but a 6" caliper could be used.
Background: I have a 30 cal ammo can slam full of 30-30 brass that was once fired and I ran it all through my RCBS 30-30 dies and the die was sitting way off the shell holder so I was not full length sizing them. I loaded up 8 rounds and measured the distance from case head to shoulder which was measured from the top of the gage to the back of the rim and on my gage this is .080". I then fired the cases and measured them again and the variation of forward shoulder movement was astounding running as much as .010" forward which for a bolt gun is completely unacceptable and were uneven.
I reloaded these and backed the FL die up to where only the neck was partially sized (this did not move the shoulders at all) and loaded them up again and shot them and there was very little movement of the shoulders and still no common uniform length to shoulder.
I neck sized them again and loaded them up and greased the cases. Now I am showing shoulder moved an average of .018" forward.
I loaded them again and greased them and now I have arrived at where I want to be which is the case shoulder is actually touching the shoulder of the chamber. Basically my finish length is around .104 so the shoulders have moved forward .024" ! ! ! ! !
I ran my die down in small movements till the shoulders went from .104 to .103" and I will leave them right there. I can easily chamber loaded rounds at this position.
On my dies with my shell holder the distance from the top of the shell holder to the bottom of the die is about .023" which I figure is a good starting point till the shoulders have contacted.
Now that I have my shoulders where I want them I can get down to some serious testing. I shot 8 shots the other day. First on cold clean barrel was high, the next six rounds went like 1.006" center to center and the last shot was low out of the group. Group was vertical which I attribute to inconsistant control of the forearm as I have figured out just letting a light gun shoot resting on the bag will give large variations in dispersion where controlling the forearm by a firm grip will significantly decrease group size.
Another killer is the factory trigger pulls. If you pull down rifles with a falling hammer design you will find the sear surfaces form two V type shapes and interlock >>. Thus when you start to pull the trigger the force required to pull one > from the other is considerable.
If you are skilled you can get these trigger travels reduced by perhaps .030" and feel much lighter. The trick is to stone the sear so bouncing a cocked rifle on the floor will not jar it off. It other words you can make it too good of a pull and wind up in a unsafe condition if not done correctly. I did mine in three stages and I have removed all the perceived creep and the roughness so I cannot detect trigger movement before it fires.
Having a good trigger is very critical in taking off hand shots.
I believe the next time I shoot my groups will be better yet as I am not fighting a glitchey trigger. I guess I have now done about a dozen lever guns for myself and friends and so far none have been overcut into the danger area but then again I would never carry a cocked lever gun in the woods. They are always carried with hammer down locked in the 1/4" cock position.
My bolt guns are adjusted as well and I never carry a round in the chamber while moving with the bolt down. There are only a few bolt gun safeties I trust, 1903 Springfield, 98 Mauser, Jap Arisaka, Ruger 77 MK II, 71 Mauser, 71/84 Mauser, and I have a Tikka T3 I just got but have not evaluated the safety as yet.
If I want to have a round in chamber on anything else and be ready quick I carry rifle with bolt knob in the up position so all I have to do is lower the bolt which is very quiet and it is ready to go.
On other rifles I trust the M1 Garand, the M14 (A), M16 for starters to carry loaded and cocked.
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