308 & 200 hybrids horizontal stringing

[Julien]

We are trying to tune a 308 to shoot the berger 200gr hybrids and are getting unexplained windage.

The action is a RPA quadlock with a 30" heavy palma barrel in 10.33 twist siting in a laminate stock.
The barrel is new and was tested with 185's and shot superbly then the throat was cut a bit longer to accept the 200's.

So far the results have been kind of weird really, we had speeds in the 2750 fps range with only 2 or 3 fps spread and the taget at 300m printed a straight line about 6 inches long with no wind.
Normally this should shoot great but the stringing has me confused, there was no wind to speak of .

Results @ 600m three in 3/4" and one 6 inches away all in a straight horizontal line so near zero vertical , again no wind .

We are hitting the range again tonight to try again , i beleive the load was about 45 gr varget lapua palma brass with small rifle primers and 200gr berger hybrids.

Any advice on my horizontal stringing would be greatly apreciated.

 

[Steve Blair]

Have you adjusted your seating depth in small (.003" or .075mm) increments? I usually see groups go from vertical to small to horizontal to a scatter node as the depth is adjusted.

 

[savageshooter86]

What powder? That seems fast for 200 hybrid doesn't it?

straight line about 6 inches long with no wind

Would that be wind?

 

[jsthntn247]

Might want to check and make sure you have good clearance around your barrel and one side is not touching when recoiling. Has it been bedded?

 

[wolley]

I'm thinking the heavy recoil of pushing a 200 at 2750 has knocked something loose.
Or it could just be too hot of a load? 2750 is really pushing a 308 with a 200g bullet.
Trying to burn that much powder could have all kinds of bizarre results when the bullet exits the muzzle and still has 15,000psi behind it.

 

[Julien]

Have you adjusted your seating depth in small (.003" or .075mm) increments? I usually see groups go from vertical to small to horizontal to a scatter node as the depth is adjusted.

We had played with the seating depth and again tonight, our problem seems to have been primers .
Once we tried a different primer things tightened right up .
This is the first time I see primers give windage normaly flyers are the cause.

Unless we overlooked something the problem seems to be resolved the gun held 1/4 moa and better out to 685yds.

 

[wolley]

Muzzle pressure isn't as high as I thought it would be. Still a VERY hot load though.
Cartridge : .308 Win. (SAAMI)
Bullet : .308, 200, Berger Hybrid #30427
Useable Case Capaci: 44.580 grain H2O = 2.895 cm³
Cartridge O.A.L. L6: 2.906 inch = 73.81 mm
Barrel Length : 30.0 inch = 762.0 mm
Powder : Hodgdon VARGET

Predicted data by increasing and decreasing the given charge,
incremented in steps of 1.111% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms

-11.1 101 40.00 2534 2852 57271 5189 99.9 1.478 ! Near Maximum !
-10.0 102 40.50 2560 2912 59456 5221 100.0 1.455 ! Near Maximum !
-08.9 103 41.00 2587 2972 61727 5251 100.0 1.434 !DANGEROUS LOAD-DO NOT USE!
-07.8 104 41.50 2613 3032 64089 5278 100.0 1.412 !DANGEROUS LOAD-DO NOT USE!
-06.7 106 42.00 2639 3093 66547 5304 100.0 1.391 !DANGEROUS LOAD-DO NOT USE!
-05.6 107 42.50 2665 3154 69104 5329 100.0 1.371 !DANGEROUS LOAD-DO NOT USE!
-04.4 108 43.00 2691 3216 71767 5354 100.0 1.351 !DANGEROUS LOAD-DO NOT USE!
-03.3 109 43.50 2717 3277 74541 5379 100.0 1.331 !DANGEROUS LOAD-DO NOT USE!
-02.2 111 44.00 2742 3339 77432 5403 100.0 1.312 !DANGEROUS LOAD-DO NOT USE!
-01.1 112 44.50 2768 3402 80445 5426 100.0 1.293 !DANGEROUS LOAD-DO NOT USE!
+00.0 113 45.00 2793 3464 83589 5448 100.0 1.275 !DANGEROUS LOAD-DO NOT USE!
+01.1 114 45.50 2818 3528 86870 5470 100.0 1.257 !DANGEROUS LOAD-DO NOT USE!
+02.2 116 46.00 2844 3591 90296 5491 100.0 1.239 !DANGEROUS LOAD-DO NOT USE!
+03.3 117 46.50 2869 3655 93877 5512 100.0 1.221 !DANGEROUS LOAD-DO NOT USE!
+04.4 118 47.00 2894 3719 97620 5532 100.0 1.204 !DANGEROUS LOAD-DO NOT USE!
+05.6 119 47.50 2919 3784 101537 5551 100.0 1.188 !DANGEROUS LOAD-DO NOT USE!

 

[XTR]

We are trying to tune a 308 to shoot the berger 200gr hybrids and are getting unexplained windage.

The action is a RPA quadlock with a 30" heavy palma barrel in 10.33 twist siting in a laminate stock.
The barrel is new and was tested with 185's and shot superbly then the throat was cut a bit longer to accept the 200's.

So far the results have been kind of weird really, we had speeds in the 2750 fps range with only 2 or 3 fps spread and the taget at 300m printed a straight line about 6 inches long with no wind.
Normally this should shoot great but the stringing has me confused, there was no wind to speak of .


i beleive the load was about 45 gr varget lapua palma brass with small rifle primers and 200gr berger hybrids.

You are going to blow something up.

For most F-TR shooters the load for the 185 Berger is "about 45 grains of Varget" (or less), with a MV that you are quoting for the 200s. (yes you can get 185s faster but with different powders) you are way out there. I get less than that with 2000MR. You really should consider slowing it down, about three to three and a half grains worth.


Check your brass. You may have already blown the pockets.

 

[Julien]

Ok guys before anyone thinks we are going to blow something up you guys haven't taken into consideration the groove diameter of the barrel the extended throat and the fact we are using cases with small rifle primers.

I make barrels and this one was made with the 200's in mind which is why it was cut to a larger groove diameter, the small rifle primers ignite the powder slower so the pressure spike is slower and the longer throat gives more boiler room.
If I would have cut this barrel to .3075 or .3077 rather than what I did rifle it @ the speed never would have reached 2750 without serious pressure.
The fired cases have been neck sized and reprimed and the pockets are as tight as they were no overpressure signs at all.

The pressures were normal with no cratering of the primers or flatening the bolt opened very lightly and btw an RPA quadlock is a hell of a tough action .
Lapua brass is also thicker and can handle a bit more pressure than some

I shoot a lot of f-class and I see guys load stuff up to crazy pressures where cases are only good for one firing, this is certainly not the case with this load because the brass will last in this one.

Varget also varies from lot to lot and sometimes 2 grains for the same velocity so this one is a bit slow.
After repriming the fired cases the pockets are still very tight so no overpressure that I can detect this is after 2 firings now

 

[paulT]

Hi Julien, Have you also tried the 215g Berger hybrids, how far off Lands are you with the 200g hybrid load, Just completed build with my FTR rifle which has a 32in heavy palma profile barrel with 1 in 10 twist which is throated for the 210g berger BT LR however i notice the berger 215g hybrid has higher BC and might switch to this bullet for 1000-1200y however i read while back that the 215g hybrid was hard to tune and most FTR shooters seem to prefer the lighter 200g hybrid or 210 BT LR bullet for some reason.

 

[Julien]

PaulT the only heavies I have played with are the 200 berger hybrids and they worked best for me .015" off the lands.
We tried some N150 at first but the es was to high ,with varget they are below 10 fps now.
At first there was only 2 or 3 fps difference but the grouping wasn't great with the horizontal stringing.
I know the Chou brothers in Ontario Canada have been using the 215's with good success from what I have been hearing.
I haven't checked today's scores at the Canadian f-class championship in Ottawa but as of yesterday they seem to be doing well.

 

[paulT]

Thanks for info Julien.

 

[Trevor60]

the Chou brothers shot the 185's at this years Canadian F Class Nationals. I know they have made several attempts to get the 215 to work without success up to this point. i am not sure they are pursuing this anymore but as winter comes anything is possible.

Trevor

 

[Julien]

Trevor those 185 jugernaughts are sure easy to tune and perform very well in the wind these are what I will be shooting for the rest of the season.
A friend of mine knows the chou's and told me they had done well with the 215's at one point so I assumed they were still shooting them .

From the testing we are doing with the 200's however I think this may be my bullet for next season, as well as a barrel rifled to the same dimensions as the one I did in the rifle we are testing with.

 

[Trevor60]

200 get better BC but there is a trade off against accuracy and more recoil then the 185's there are allot of people that shoot the 200's with good results.

I was at the Chou's yesterday so I can only go on what they tell me, and as of right now they are still in the testing phase and have not shot the 215's in any match,

Best of luck hope to see you at the Victoria day or Easterns next year.

Trevor

 

[Julien]

Trevor, I really would like to be able to make it out there next year , now that we have friends that moved to Ottawa it might be easier for me that way the wife and kids would have something to do.

 

[Medium rare]

I am shooting the 215s and they have performed really well. I had the same horizontal stringing that you are describing. I'm not sure if it was my inability to tame the recoil but I ended up going done to the next lower node which fixed my stringing problem. I have been shooting the best I've ever done at this lower speed. I have 31 5/8" kreiger 5r hv 308. I hope this helps.

 

[Steve Blair]

I am shooting the 215s and they have performed really well. I had the same horizontal stringing that you are describing. I'm not sure if it was my inability to tame the recoil but I ended up going done to the next lower node which fixed my stringing problem. I have been shooting the best I've ever done at this lower speed. I have 31 5/8" kreiger 5r hv 308. I hope this helps.

[br]
What velocity are you getting? What bipod do you use and did you change your technique?

 

[jsthntn247]

What kind of horizontal are yall getting? I have noticed horizonal myself and wondered if it was me.

 

[Medium rare]

I am using sinclair 3rd gen adjustable bipod. I bought a duplin bipod but haven't got the rail installed and the way things are going I may not and save it for another rifle. I am running them around 2500. I have had them considerably faster. I have shot one mid range match with them and shot 147 5x and course record is 148. That was by far the best score I've had in mid range. I got second that day and would have been 2nd in open with my score. I won a steel match with this load against about 20 guys with no caliber or muzzle restrictions. I am pretty pumped about this load. It makes me look like a good shooter.