Range Report Velocity spike with Varget???

[tsonda]

Had a strange thing happen this weekend. Kids are in a match kinda like Fclass, but scored electronically on a steel plate. So we have two dashers. The kids had shot 3 rounds of 10 shot strings at 500y with short breaks in between. It was 95 degrees outside (Texas). Gun was getting pretty warm. Ammo was in the shade. Targets got moved to 635y. So a longer break after the 500y series. Girls gun we had previously during warmup got a good dope to 635 using 3.4mils. First shots at 635 on warm gun where roughly 18" high. took us 5 shots to find the misses and move her down on the plate. Final dope dialed in at 2.6mils. After we got her on she held 3-4" vertical at 635y. Next heat my boy shot the same targets (different gun) and used his dope of 3.4mils. Dope was good. We got home I took the gun out with the remaining 12 rounds we had and the gun shot good out to 790y.



Both guns running 2956 fps. Girls gun 32.6 grains of Varget 105 hybrids. Boys gun is 32.7 of Varget 105 hybrids. No pressure signs both guns. Loads developed at around 75 degrees, but have been shot at 85-90 degrees.

Any ideas??? First I might add that the girl is 9yo and anything can happen at that age. That said after I dialed her down she held a 1/2 moa vertical for 5 remaining shots. I was initially thinking hot gun, hot ammo, hot mag equals pressure spike. But we had no heavy bolt lift. no ejector marks on brass. The calculation in the app says the 105's would have to be traveling at 3350 to get that same dope. I would think if we had that big of a pressure spike we would have the telltale signs

 

[MakeSawdust]

When you shot the gun after the match did you still have to dial less elevation or did it go back to what you expected?

 

[ballistic64]

Wow, 18" high at 635 is quite a bit. Last year I was in a hurry to get some 6BR loaded to shoot the same day and developed a case of HIA. My load was 30.3 gr RL15 with 105s. When I got to the range and my shots were about 10" high, I immediately quite shooting after a couple shots and realized my head in ass reloading session turned out to be 33 gr of RL15 instead of 30.3. I could tell something wasn't quite right just by the sound of the shot and amazingly the brass really didn't show a lot for excessive pressure. When I got back I pulled the bullets and sure enough 33 grains.

 

[tsonda]

When shot again at the house, the dope was back to where it should have been out to 790y with velocity at 2956. Same loaded rounds we took to the match. I'm thinking if it was a pressure spike then the boys gun should have done something similar, but it didn't

 

[ballistic64]

That is strange. I don't run Varget but I don't really think it is known for temperature sensitivity.

 

[Mordamer]

Scope tracking problem? Unless you measured the velocity spiking up, that would be one of the last things I'd suspect.

 

[Milo 2.5]

The only thing that comes to my mind is a carbon ring started developing, then one shot blew it out. BUT, I do not think varget is known for carbon rings, and usually accuracy suffers with a carbon ring.
.8 mil is way too much for even a 9yr old fundamentally wise.

 

[tsonda]

It has me baffled for sure. Maybe 100-125 rounds since last cleaned

 

[garandman]

Vargets always been consistent for me.

 

[Seandradamus]

Maybe she started holding on the one mil line of the Reticle , I’ve mistakenly done that when the background is dark , The brain can do funny things in competition

 

[tsonda]

Anything is possible with a 9yo. Whatever she did it was consistent

 

[Clearlight]

Hmm wasn't there so cant say for sure , but different shooters often have different zeros if not shooting off
a rest F Class / BR style .

Cooking a round in a hot rifle can give you enough extra fps to be over the target.

 

[bschneiderheinze]

Are you using an 8lb jug or something else. The only reason I ask is because I took 7 1lb jugs and threw them in a 8lb jug and “mixed” them together. I’ve been shooting high and inconsistent but the chrono was pretty consistent with the 20 rounds I had left over after the match. I have noticed huge swings bp here.

 

[tsonda]

Yes all loaded from same 8lb jug of Varget. And She had a good dope from previous practice round out to 635y. One of my other questions would be if we "cooked" off 5 rounds in a hot barrel, I would assume to see some pressure signs on the brass or heavy bolt lift.

 

[WB300]

Interesting for sure. I go through similar with my 12 year old. I've second guessed my loads and scope several times but now think it's inconsistency on his fundamentals.

Parallax, mirage, wrong dope/holds, too much cheek/head pressure on stock? Combo of these???

Update when you get it figured out.

 

[bschneiderheinze]

Can I ask what scope your running just for my benefit. I’m doing a tracking test on mine this week. Something isn’t right.

 

[tsonda]

Kahles 525i

 

[Qtip]

Dwell time in the hot chamber likely raised the temperature of the round affecting the velocity.

 

[tsonda]

well she cranked off 5 pretty quick. All where high I don't think dwell time was a problem