7mm Mag grouping question

[landyboy]

I've been trying to dial in my Browning 7mm Rem Mag and for this picture I am using Berger 168 Hunting VLD's it is a ladder load with Retumbo and each 3 shot group is 1grain of powder more. The 1st two shots of each group are nearly touching but the third is about 1 1/4 away. Its an Abolt sitting in a Bell and Carlson Stock 26" barrel. Velocity deviation is pretty good and I am waiting between shots the same amount of time.

 

[Blinddog]

My abolt 7mm did not like 168 gr. vld's either switched to 160 gr. Nosler Partitions and issue solved. the main reason was seating depth. where I wanted to seat them they would not fit in the clip. loaded manually they grouped great but seated deeper to fit in clip my grouping opened way up. Maybe you can find the right mix to get them to work.

 

[MeatMissile]

Have you shot any groups of more than 3? If so, did you have a 2-group situation or a continuous stringing?

 

[Marble]

I've been trying to dial in my Browning 7mm Rem Mag and for this picture I am using Berger 168 Hunting VLD's it is a ladder load with Retumbo and each 3 shot group is 1grain of powder more. The 1st two shots of each group are nearly touching but the third is about 1 1/4 away. Its an Abolt sitting in a Bell and Carlson Stock 26" barrel. Velocity deviation is pretty good and I am waiting between shots the same amount of time.

I have 3 A bolts. 708 Ackley, 7mm and 300 wm. All like max or a little over on powder and are within. 010 of the lands.

They are also sensitive to various powder increments and going a full grain is too much to know if you're right on or not. There is a lot of testing to do in 1 grain.

Bergers can be slightly difficult to get just right. But they are good bullets as their popularity is indicative of their performance. Your other option that I would consider is the 160 AB.

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[EdP]

How long are you waiting between shots? Did you shoot all 9 shots in succession with the same wait time or did you wait additional time between groups? After getting two excellent shots are you taking additional time trying make sure the 3rd is good too, and letting that cartridge get hot in the chamber?

1 grain increments may be a bit large for finding an optimum load but given that all 3 groups are the same size I don't think that has anything to do with your issue. It's the 3rd shot opening the group per your original question.

I second MeatMissile's recommendation - shoot 5 shot groups, it will provide additional info. Also, I'd recommend waiting 3 minutes between shots and keep the sun off the barrel.

 

[riversidejeep]

I have a few hundred groups like that from 20 different rifle/caliber combos. Do your load workup in 1% increments and I'm sure you'll find a load that makes a nice round group. If not switch powders.

 

[Harvey_NW]

Your POI consistency is great for a 3 grain spread. I would use the high charge and test seating depth and .1gr increments around that. Might also check your ring base connections and action screws, make sure everything is degreased and torqued. Unpopular opinion but I test with 3 shots until I start getting somewhere because 3 shots may not be statistically valid to call a load good, but it will definitely let you know if it's not.

 

[menhaden_man]

I've been trying to dial in my Browning 7mm Rem Mag and for this picture I am using Berger 168 Hunting VLD's it is a ladder load with Retumbo and each 3 shot group is 1grain of powder more. The 1st two shots of each group are nearly touching but the third is about 1 1/4 away. Its an Abolt sitting in a Bell and Carlson Stock 26" barrel. Velocity deviation is pretty good and I am waiting between shots the same amount of time.

I get sweet groups out of my xbolt with 168 VLDs and 62.2 gr of Retumbo... 2.725" CBTO and BR2 primers. Not sure what you've got going on there but will probably take a few more rounds to find out.

 

[Raygun15E]

Try the Berger seating depth test. Then go back to your powder test. You should find a seating depth your rifle likes. I was having the same problem with a tikka T3 .30-06 and 180AB. It was driving me nuts. I picked the powder weight that gave me ‘best’ group and velocities to run a seating depth test. I found I needed to jump the bullet more than expected. I also recommend using smaller powder increments. Using .5gr should be small enough and it’s simple math.


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[SouthPaw]

If the VLDs keep giving your trouble maybe try the Classic Hunter, they were designed for SAAMI & factory mag applications. Other bullets have been more finicky in my Abolt (270) but these were super forgiving. Right at book max H4831sc .020 off the lands and it shoots fantastic and fits in the mag for hunting.

 

[bdan68]

With two different points of impact like you're getting, it could be a scope issue (parallax maybe) or perhaps a bedding issue.