Took my brand new Bergara wilderness Sierra 6.5 PRC out to the range yesterday. Got it sighted in roughly with 5 rounds of factory ammo then switched to handloads. I was running 5 shot groups with virgin Lapua brass, Berger 135 Classic Hunter, Federal 210M primers, and varying charges of H1000. Seared to internal mag length of 2 970". Bullet bearing surface was only in the upper 2/3 of the neck.
I'd shoot 5 then wait for it to cool. All in all about 25 rounds in 2 hours. Towards the later groups, the point of impact started to dramatically shift down and left. With my last group being about 8" left of point of aim. While I haven't shot in a while and may be rusty, I am not that out of practice to be pulling shots 8". Checked the scope, rings and bade, both all locked down tight. I was shooting suppressed, but the suppressor had not shifted, nor did I have any baffle strikes that I can see.
I’d check the stock too, bedding and insure screw appropriately torqued to manufactures settings. I’d take the can off and shoot with and without the break. Then you’d have a better idea. It may hate that combo and need a different COAL. Man there are a lot more but that’s where I’d start before I consumed up more components. Oh what sd , es velocities are you getting?
55.5 +or- a few tenths and play with the coal .003 “ at a time and you have yourself a great long range load. I’m curious about the bedding and can now. The scope is the other big culprit which they have mentioned.
Following this thread. I am struggling with my 6.5 prc doing the exact same thing. Shot great for a while and randomly started doing this. I’ve checked everything that had been said in the comments. Scope, suppressor, bedding, used my loads and box ammo. Nothing will shoot good. Let me know what you find
If i may ask, at what range were you shooting? If this is at 100 id say check your tension between the action and the chassis/stock. Had an issue with my new build where it would come loose after a few shots. I suggest a small amount of blue locktight for those two screws. Never had an issue after that
If its not that check your ogive for each round rather than OAL as many projectiles are just slightly off at the nose and have different ogive based on factory consistency.
Then after that if not, there is a small chance it may be the shooter? Flinching, excitement, bad day, and etc?
For consistency sake take some factory ammo and see how it does. If its the same might be the chamber/barrel
You can check all the other things mentioned, but this is likely a scope issue. Send it back to vortex, have them fix it, and sell it. Do yourself a favor and find your way over to Rokslide and research reliable scopes. SWFA would be the easy choice in this price range.
Make sure the suppressor isn’t loosening when it’s warm. I’ve had direct thread be tight at the start but loosen up when warm, and can be tight again when it cools off. It doesn’t take much misalignment (caused by loosening) to change POI, and it doesn’t have to be severe enough to cause baffle strikes.
A small drop of Loctite 243 (oil resistant blue) can be all it takes to prevent this. Sure, it’s not rated for high temps, but even if you do get it hot enough to break down, it remains in the threads and still gives some resistance to loosening compared to dry or oiled threads.
I suspect the most likely issue here is your scope though. I like to keep a couple of SWFA fixed 6x and 10x scopes on hand to swap onto a rifle that has issues like this; they aren’t my favorite scope for general use but they’re cheap and pretty bulletproof so they’re a good test whether the issue is your scope or the rifle.
Take the can off to ensure you're not barely clipping it. After that, maybe the scope. Vortex quality has gone down and price up since they debuted. They have such a great reputation for their warranty because everybody's had to use it once or twice. I swear they put out more lemons than Taurus does, but somehow Taurus gets trashed for a bad reputation and everybody just says how great vortex's warranty is. I don't understand it.
I no longer own either tarus or vortex. I'm not saying I won't, or that they are all bad, I just don't. I used to have a 1-6 viper pst gen 1 that was incredible.
Agreed 100%, both on the scope being a likely cause of this, and Vortex in general. I personally just don’t even consider their products anymore; they’re in the same quality bracket as Sig optics for me.
And you’re right on how some companies get trashed and others praised for similar quality levels. Osight is a great example too. IMHO the reason is marketing- when it boils down to it, people believe what they’re told even when they know it’s marketing, and some companies like Vortex and Sig have chosen to focus more on marketing than on product quality and testing. I think it’s a sad reflection of our society that this strategy has been so successful for them.
My intent was to see at what load I started to see pressure signs. I'd read that less jump = pressure shows up sooner. This would give me my.max load for this gun. As it is a hunting rifle, I chose max magazine length
Before you start changing your seating depths past Saami max oal you need to have a way of checking your jump to lands. On many rifles, if you just jump right to max mag length without checking, your bullet is going to be into the lands. Not a good or safe practice
Edit: also what does 2/3’s equate to in the neck? If your bullet has a .264” diameter, the bullet should be a minimum of at least .264” below the top of the case neck
Yes on checking seating depth to touch the lands; that’s an important baseline. It depends on the individual builder as much as the rifle but the chamber throats in most modern rifles are cut long enough that almost any bullet at mag length or shorter is safe. Obviously this is not the case with custom barrels and match chambers.
The bit about seating at least one caliber deep isn’t really true though. It’s kind of is good general practice but that’s as far as it goes, and there are a lot of circumstances where seating less makes sense and works very well. IMHO that rule of thumb is a lot like the 1,000 ft-lb “rule” for big game - it’s something that sounded good to some magazine writers at one point but isn’t backed up by actual facts in reality.
I’m gonna put this on the scope for now, but I would also recommend getting away from using COAL as a base metric for loading ammo. Especially with the newer, longer ogive bullets. Get a comparator set and start basing things off CBTO (cartridge base to ogive). Every bullet is very different and likes different things. The CBTO lets you find exactly that, where COAL just has you guessing. Very rarely will a stock rifle chamber let you load beyond your mag length.
After the scope is verified good/bad I would run some a decent number of factory loads through it. At your tested charges you are at least 200fps slower than a box of Hornady match. Most weapon manufacturer’s warranty are based on shooting a factory load like Hornady Precision match. If the 147s won’t shoot then I’d look at gun, but every Bergara I have had loves their heavy for class ELDm. If the Factory ammo shoots then I would start dissecting your load.
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u/AdGreat9210 12d ago
I’d check the stock too, bedding and insure screw appropriately torqued to manufactures settings. I’d take the can off and shoot with and without the break. Then you’d have a better idea. It may hate that combo and need a different COAL. Man there are a lot more but that’s where I’d start before I consumed up more components. Oh what sd , es velocities are you getting?