Shimmed 2 V2's today....

[SidecarFlip]

Finally got around to shimming 2 Accura V2's (Bergarra) today, mine and my hunting associates.

Interestingly, it's a long process but in the end, both rifles close properly and trigger properly with no primer blowback whatsoever. We touched off both mine (that hasn't been fired since I bought it about 5 months ago) and my friend's that has been touched off numerous times.

I'm sending Barnes saboted 250's, TMZ flavor and my friend is sending Thor's in FMJ, no sabot. We are both using Blackhorn at 100 grains and both rifles are tack drivers at 100 yards. Both rifles shot with holes touching at 100 (after initial sight in and bore swabbing......amazing. 3 ignitions on each to set the optics (both have Nikon Camo BDC reticle) scopes and 7 more.

10 shots through each and absolutely no primer blowback or bolt face blackening.

Far as manufacturing tolerances, mine took a 10, a 5 and a 2 thousands shim to set the retainer where the primer cup was rubbed completely around the circumference while my friend's took a 10, twin 5's and a 2 to achieve thge same result.

My friend's was showing a bit of bolt face erosion from blowback, a thing of the past now.

I would never recommend the shim kit to anyone without a good working knowledge of the mechanics of fit as it pertains to slam ignition. It's a very fine line between proper operation and unintentional ignition. The retainer must be set where the retainer contacts the primer cup evenly without deforming it and possible igniting the primer accidentially and once the retainer is properly set to a particular brand of primer, you cannot switch primers without resetting the the clearances because different brands have different cup heights and it only takes a couple thousands more to initiate a slam fire.

I set both retainers at 10 inch pounds for the sake of repeatability and to provide a constant compression on the 'O' ring on the retainer.

I'm using CCI 209 standard shot gun primers btw, n ot the fancy (and way more expensive) 209 inline primers. Not needed.

 

[ENCORE]

Its great when a plan comes together...

 

[SidecarFlip]

It takes a bit of time, about 3 hours for each rifle and of course you have to disregard the cautionary label on the shim kit. What I found interesting was the variance in the depth of the countersunk bore between the 2 rifles, one bore was appreciably deeper than the other, 0.010 or so. I checked the depths with a micrometer depth gage prior to applying any shims.

You have to be really careful installing the shims, especially the 0.002 size. They want to get cocked in the bore and you have to jostle them in. I used a solid carbide machinists scriber and my magnifying headgear.

The firing pin retainers are well out past the breech face now. I set each retainer at 10 inch pounds, seemed like a good torque value.

Closing the action requires a firm close, not a snap shut, but a firm shut. If you shut the action with less than a firm shut, the trigger won't pull back so I know, I'm right there. The cups are showing a ring around the outer edge, all the way around, the primers I'm using are CCI 209 standards with copper plated cups that make seeing the fit easy.

I used about half a box of primers setting up both rifles, wanted to get it as close as possible without actually striking the primer pill.

Absolutely no blow by from the breech plug primer pocket and the primers come out just as easy as before and it's burning most all of the Blackhorn, we swabbed the barrels after the second load on each, then sent 8 more without swabbing and the last one went in as easy as the first one, not that the yellow saboted TMZ, don't load easy because they don't. The FMJ's went in real nice and stayed nice and easy to load.

I brought them both in the house and cleaned both. 2 patches in each barrel with CVA bore cleaner and the 3rd patch was clean. Pulled the 209 breechplug, a bit of bore cleaner, a Q-tip and hot water and all is like new.

No cleaning of the breech face or the lug area because nothing blew out.

Both rifles are grouping in 1.5 inches at 100 yards with 100 grains of Blackhorn. I'm tickled.

Next comes some chronometer readings. I want to find the sweet spot for the Barnes and the Thors (which are actually non-saboted Barnes). I'm going to order some non-saboted lead polymer tipped and fiddle with them too.

All in all, it's fairly easy to take a production rifle with an excellent barrel but some detractions and make a better rifle from it.

I suspect my centerfires will be spending more time in the gun cabinet next fall.....

The only negative aspect is the time it takes to get it just right, just the right amount of crush on the cup, and, you can't ever switch primer brands or style because cup height varies from manufacturer to manufacturer, while not much, maybe a couple thousands, being at the edge of a slam fire condition and substitutiing a higher cup could have bad results.

 

[FrontierGander]

3 hours? Good lord, it only takes me maybe 10 minutes.

You only need .002" crush fit on the primers to be blow by free.

Have you measured your primers length and then closed them in the action and measured again to see exactly how much crush fit you are getting?

 

[ENCORE]

3 hours? Good lord, it only takes me maybe 10 minutes.

You only need .002" crush fit on the primers to be blow by free.

Have you measured your primers length and then closed them in the action and measured again to see exactly how much crush fit you are getting?

Maybe you should have explained how you're dong it for him...

 

[SidecarFlip]

3 hours? Good lord, it only takes me maybe 10 minutes.

You only need .002" crush fit on the primers to be blow by free.

Have you measured your primers length and then closed them in the action and measured again to see exactly how much crush fit you are getting?

Absolutely. I read your instructions and modified them. Prevailing torque on the retainer actually determines the final fit which is why I set both and a set torque value. I had some issues with one rifle because the breech face was starting to erode from many ignitions. I had to fixture the action in the mill and spotface the recess (above the threads) to provide a square and flat base for the retainer, shim washers and seal ring to rest on. The first was no issue, the second was. 6 hours total, however, the recess was 0.010 deeper prior to spotfacing.

I fully understand CVA's reluctance (and their disclaimer on their website as well as the disclaimer on each packet of shims). It's not a procedure to be undertaken lightly because it can result in spontaneous ignition when the action is closed, if, the retainer crushes the pill. That would be ugly and most likely result in personal injury.

It would be very difficult to determine (accurately) just what the crush is. By that I mean, there is no way to determine (for the layperson) what 0.002 crush on the cup is, because when the action is closed, the cup is not accessable, one reason I bought the CCI's, because they have a copper plated cup that allows you to visibly ascertain if the cup has physical contact with the retainer and what the area contacted is. I set the fit to encompass the entire outer circumference of the retainer, but beforehand, I ensured the retainer was flat and square by chucking both retainers in an appropriate collet, fixtured in the surface grinder and took a cleanup pass across the face.

As a machinist/shop owner and dealing with precision machining everyday, I would not recommend or endorse anyone to modify their CVA is it was in service for any length of time.

The ideal scenario is applying the modification to a new, unfired rifle or a rifle with very limited ignitions. Simply put the blow by from the primer fit degrades the breech face over time and degrades the retainer face as well. New or limited use rifles will not have that issue.

Works like a charm but procedural attention is everything.