195 Bergers and Vihtavuroi N570

[MudRunner2005]

Ok so I need some help now. I have worked loads all the way up to 85 grains of VVN570 with no pressure signs but the best accuracy was around 82.5 grains. (All of these loads were loaded to Mag length) The grouping was not great so I figured I'd do the Berger seating depth test. Loaded up 24 rounds per the directions and started with the shortest COAL. I figured I'd start with more jump than less in case there was a pressure spike. Glad I did. The first round was fine. the next round had a pretty stout bolt lift. Against my better judgement I decided to fire one more and it blew the primer out. Why such a pressure spike when I decreased the charge and loaded the bullet longer? I was shooting 0.13 off the lands. I'm guessing that I need more jump?? I thought that with the bullets being loaded longer the pressure would be reduced even at the same charge....

I don't know if this is true, but here's my theory...

Could it be possible that seating a bullet too deep can create excess chamber pressure and pressure spikes, just like seating one into the lands will?

My reasoning behind thinking this, is that, while the bullet has no physical force obstructing the front of it (like it would be if it was engaging the rifling), the bullet would still need excess force to push it out of the case because of the excess amount of bearing surface that has to be pushed through the case neck that is gripping the bullet. In-turn causing excess boiler time, which would create more pressure inside the case than if the bullet was seated farther out, where the bullet would be pushed out of the case sooner, creating lower pressures...

I would be interested in hearing other people's thoughts on this, as well.

 

[jweigel]

I wanted to post my findings with this combo in my Factory Sendero. Started with the bullet seating testing all done at 77 grains of N570 with Fed215. Found .050 off the lands was best in this gun. Groups were nothing special. Then did pressure testing starting at 77 and going up to 84 grains. Had extractor marks at 83 and 84, bolt lift at 84. Speeds ranged from 2950 at 78g up to 3200 at 84 g. The loads from 81 on up really opened up so I loaded a group from 78g up to 80g and shot yesterday. The 78 and 79 had really low ES (6 and 12 respectively) but groups were just over 1 MOA. At 80 grains the point of impact jump 5" vertically and the three shot group was a .31" MOA. AV speeds were 2914 - 78g, 2969 - 79g, and 3103 - 80g.

I have found this powder really lays down lots of powder fouling. ....and I mean lots. I started to clean (Wipe Out) after ever shoot.

Going to load up a 79.5, 80.0, 80.5 and 81.0 to see if that .31 group was for real or a fluke. After shooting about 120 rounds working on this bullet, I have only had three groups under 1 MOA. But not sure if the barrel fouling was misleading the testing.

Will see.

jjw
ND

 

[kyron]

What range are you doing your load work up at?

I am shooting the berger 180 VLDs and could only get 1 moa on a ten shot group at 300 yards. But the other day I took that same load and shot a horizontal line (very gusty winds) that was at most 3 inches tall at 1000 yards

 

[jweigel]

I shoot at the 200 yrd Range....gives a little more separation. Once I have a load, I try to shoot at 300, 500, + to validate. I have MOA turrets and use Strelok.

I am just about finished cleaning my guns with WipeOut. Both Factory Senderos.....7RM and a 7STW. The 7RM had about 50 rounds through it (180 VLD with 70g N570) the 7STW had 12 rounds. It looks like the STW has more then twice the copper build up. Both have lots of powder.

Hope to shoot again this week.

jjw
ND

 

[jweigel]

Had great morning to shoot (Lefty....you should have been out). While I did not repeat the .3" group, I did have a 80 grains three shoot group with an ES of 3. The group was MOA. Nothing improved above or below. The speed stayed within 30 fps for a full grain of powder up from 80. At 81 grains I had a big POI shift 5 inches down. I am starting to wonder if after 8 shoots of so I get enough powder/copper fouling to cause the POI change. The speed at 81 was about the same as 80.

I love the ES and no change in speed over a spread of grains, I just which the group size was better.

I am thinking I need to shoot at 400 yards or more so see what group size is then. I am hoping (wishful thinking???) that MOA will stay or get better......bullet stabilizing with distance???

I am going to stay with 80 grains of N570. The speeds today were 3072, 3073 and 3070.

Just to test, I will load up three groups (3 shot groups) with a .010 increase and decrease in the seating depth over the .050 OTL I am at now.

jjw
ND

 

[eshorebwhntr]

What do you consider to be the best that gun will shoot? Or a better question is what is a good average group size that you get out of that gun with other loads?

I only say that because a factory STW has (I believe) a 1-9 or 1-9.25 twist. The 195 probably needs a little more than that to stabilize properly. If it's not then accuracy might not be there. Additionally, from what I've read by Bryan Litz you'll be lowering the BC on that bullet from not stabilizing properly. To get published BC's by Berger you have to be fully stabilized. In ND elevation and that combo you'll probably be about 5-6% below that advertised BC. Still higher than the 180 Hybrid.

He also posted some info on the "bullets stabilizing better at 400" part of your post. That didn't make sense to him so he tested the theory that "bullets go to SLEEP (or stabilize) at further distance". At one point he offered to fly a person out to his home with their rifle if once they arrived they could prove that their rifle shot a better group at say 300 vs 100. In the end I think his conclusion was that your eyes and scope "work better" at 300 yards vs 100 and that was how people had rifles that would shoot better groups (moa wise) at 300 vs 100. He basically made a setup where you would aim at a point at 300 yards and have your bullet punch paper at 100. Pretty interesting read.

Short answer is I don't think shooting groups at 400 to prove your loads will be of any more benefit than 2 or 300.

If you have history with another load combo that produces better results then I guess you know your accuracy potential. If you don't then that would be what I would try to establish next. Additionally, my opinion is that the 195 is another good option and not necessarily a better option. Inside 1000 yards the 180 with higher MV will probably outrun it but have slightly more wind drift.

It's up to you but I would consider trying the 180 Hybrid next if you can't get the 195's to do what you want.

 

[bigbulls]

This is what happened when I switch to 195 Bergers. I have a custom gun with 26" barrel, when shooting 180 gr vld bergers the barrel was a 1&9 twist, and now I had new barrel installed 1&8 twist everything else stayed the same with the gun. I don't shoot hot loads these 2 loads are middle of the range, no pressure signs even in the 80-90 degree heat.

The 180 vld load was shooting 3140 fps with sd being under 10 and less than 1/2 moa group at 100 yards with H1000 powder.

The 195 berger load is 3060 fps with sd under 9 and less than 1/2 moa group at 100 yards with N570.

I gave up 80 fps and .3 moa across the ranges out to 1000 yards but I gained 200 lbs of energy which is what I was after. In the end I don't think it was worth it but it's what I wanted and I'm happy. Just food for thought for others looking at changing to something different.

 

[jweigel]

Good points guys....I did have a great load with Retumbo and the 180 VLD in this STW that ran 3015 and .5 MOA. I held less them 1 MOA out past 1000 yrds. I also have a 7RM Sendero. After testing lots of powder I settle on 7828SC pushing a 168VLD 3050 but around 1 MOA.

This winter I picked up some N570 and started testing it in the RM first. But jumped to the 180VLDs. I was able to get to 3010 but started getting extractor marks but groups for a spread of 2 grains of powder were all less then .5 MOA. Backed off 1.5 grains and settled on 2950 and still .5 MOA. Have shot it several times now cold bore....even squeaky clean and the first three shots are still .5MOA. Bingo!

Started playing with these 195s in the STW using N570. After doing seating depth and then pressure testing I never really had groups below 1MOA and quit.

Using the same seating depth for the 180s/Retumbo load I did pressure workup with N570. Could get to 3200 before signs of pressure but groups opened up after 3100 so I settled on 80 grains...well below pressure and a .75 MOA.

So now i have one gun shooting 180s at 2950 and the other at 3100.
Kind of boring and seems like I not getting the full potential of the STW.

Back to the 195s....that is where I am at now.

I just visited with Dan with Chinchaga bullets about his 196 VLD. I'm thinking I should just order a box rather then keep burning powder on these 195s. I will still load up some a shoot out around 500 yards but expectations as pointed out are it will be the same 1 moa or worse as it is at 200.

That's my story and I'm sticking to it.

jjw
ND

 

[eshorebwhntr]

.75 moa @3100fps with a 180gr VLD and no pressure is pretty **** good. Brass will probably last you a while.

Good brass life in an STW means something in today's world.