Wyliecoyote wrote:Another issue is the 1/2"x 28 TPI muzzle thread on some but not all B14R steels. There is considerable hoop sress relief in some where a slugged barrel lets the pellet freefall from an inverted barrel. The symptoms are a very slight but regular POI shift as the section carbons up, great group, no group or inexplicable fliers when the others piled into a hole from the same ammo batch in the same shooting session. As they say, one group does not an accurate rifle make. The two cures are to cut and crown or counterbore and crown retaining the threads for any add ons. If you reckon it's you when one flies and the others pile into a hole, i reckon you are probably wrong. Once rectified, the POI remains constant and the ammo shows a group aggregate and not a selection of random outcomes.
bladeracer wrote:Wyliecoyote wrote:Another issue is the 1/2"x 28 TPI muzzle thread on some but not all B14R steels. There is considerable hoop sress relief in some where a slugged barrel lets the pellet freefall from an inverted barrel. The symptoms are a very slight but regular POI shift as the section carbons up, great group, no group or inexplicable fliers when the others piled into a hole from the same ammo batch in the same shooting session. As they say, one group does not an accurate rifle make. The two cures are to cut and crown or counterbore and crown retaining the threads for any add ons. If you reckon it's you when one flies and the others pile into a hole, i reckon you are probably wrong. Once rectified, the POI remains constant and the ammo shows a group aggregate and not a selection of random outcomes.
The implication here is that this "flier" should be predictable? Nine good shots in a group and number ten will be a flier? Clean the carbon out and get another nine good shots followed by a number ten flier?
Wyliecoyote wrote:The only implication here is that there is an issue with small threads cut on a large diameter barrel fitted to the B14R. How did you get to 10 shots with one predictable flier from an instance of a belled muzzle? My experience over many years shooting and putting together precision rifles is that a belling at the crown is the death knell for a rimfire or centerfire. What part of a measurable belled muzzle precisely at the threads are you failing to grasp? All you need to know is B14R with belling at the crown shoots OK but rectified shoots better. I have no idea of rifle expectations you may have but my own and those I associate with in the rimfire game is groups of sub quarter inch at 50 meters for every group. Not just the occasional one.
Maybe this can help with what gunsmiths have to deal with when old Betsy rolls up with an ailment.
https://bulletin.accurateshooter.com/20 ... uch-steel/
I have purposely not given details as to how to rectify the cock on close hang up with the B14R. The reason is simple. Bergara offers no parts back up should you screw it up. They only offer parts under warranty. I had a recent instance of a Copperhead action cocking cam failure. Details and photos were sent off to Holeshot who sent off the piece in 24 hours at no cost because Jerry said that this part should never fail. Vudoo does similar when it comes to issues and both offer spares knowing full well shooters modify, tinker and screw things up. Hopefully Bergara if they wish to claim a stake in the precision rimfire game follow suit with parts backup.
There is a detailed description amongst all the infights over on snipershide as to how to modify the B14R cock on close setup. Not exactly the way I did it, but the end result is the same.
https://www.snipershide.com/shooting/th ... s.7075139/
Wyliecoyote wrote:OK blade, how do we deal with this? My customer has brought in his B14R with a belief it is not performing as it should. The targets are showing irregularities with the occasional good group, a cluster and a couple of random fliers with other groups showing a pattern rather than a group. There is some visible carbon residue in the grooves for about 5 or 6mm from the crown. The blast pattern on the crown face is irregular with one side showing a shorter star pattern than the other. Various ammo was tried from SK, Eley and Lapua. The best result was from SK Longrange match but there are none under a half inch at 50. No two groups are in exactly the same place both vertically or laterally where the groups of 5 shots were shot in light wind. Generally the group center POI is constant to within a half inch radius of the POA. From a clean bore the first shot is not predictable and can vary considerably as to how far from POA it lands. Of major concern is even with the better ammo a shot can fly over an inch from the desired POI with total irregularity in regard to the number of shots fired. Not often but it does happen. It could be ammo but it can happen with all the ammo tested. Each ammo was tested in lots of five with a minimum of three groups. The better performing ammo had three or four shots to season the bore then at least four groups of five were shot.
Slugging the bore finds a loose spot right at the MD threads although the crown itself looks very regular and well machined from the factory. Using guage pins from Deltronic the bore right at the threads is over a thou over size for a depth of 11mm, the exact length of the MD threads. So blade tell me, what is your recommendation here?
You tell me your fix, I am shooting this rifle today and I will tell you what I did and didn't do. If it fails we will try your way.
Wyliecoyote wrote:. A precision ground 300 thou recoil lug fitted, factory bolt shroud junked and a hardened Rem 700 style shroud fitted.
Wyliecoyote wrote:If you take 0.6mm off that shoulder at the thread where the cocking sear screws onto the striker rod, it will give you a full 80 degrees of cocking engagement, slightly increases spring force, and will lengthen the striker travel giving a sharper more positive rim strike. A very simple fix to greatly increase ignition reliability that in itself will reduce ES and close groups at 100 meters/yards considerably. That 30 degrees or more of bolt lift no mans land is not an endearing feature of the B14R.