Help with 284 Shehane

[canderson]

I am having a little trouble tuning my 284 shehane. I have throated the gun to where my OAL with a 180 is around 3.2". This helped the gun tremendously. The load is 56.8 of 4831 with a BR-2 using Berger 180 vld or JLK 180 vld. Velocity is 2907, ES in the high teens. The problem is huge unexplained verticle shots (12-14 high) at 1000 yards. The gun will shoot fine for a while then, it will sling one or two high. I have a dasher barrel for this gun and, it shoots like a dream. I feel like the gun/scope setup is fine. Looking for any and all suggestion before I make a tomato stake. Thanks.
Chris

 

[ThunderDownUnder]

Hi Chris, you probably tried this already but no harm done by repeating it!
VLDs are tricky suckers and really need to be placed in their "sweet spot" for launching and it can require some testing to find the right bullet seating position.

Below is a direct quote from Berger Bullets...

"For years we have relayed that it is best to jam the VLD into the lands for best performance. This works for many rifles however there are many rifles that do not shoot the VLD well when the bullet is jammed. We have learned that the VLD can shoot best as much as .150 jump off the rifling. VLD bullets can be sensitive to seating depth and it has been found that these bullets shoot best in a COAL “sweet spot”. This sweet spot is a COAL range that is usually .030 to .040 wide.
The quickest way to find this sweet spot is to load ammo at four different COAL. Start with a COAL that allows the bullet to touch the rifling. The next COAL needs to be .040 off the lands. The third COAL needs to be .080 off the lands. The last COAL needs to be .120 off the lands. One of these COAL will outperform the other three by a considerable margin. It has been reported that the VLD bullets don’t group as well at 100 yards but get better as the bullet “goes to sleep” at further ranges. We have learned that by doing the four COAL test you will find a COAL where the VLD bullets will group well at 100 yards. Once the COAL that shoots best is established you can tweak +/- .005 or .010 to increase precision or you can adjust powder charges and other load variables. Frankly, those who do the four COAL test usually are happy with the results they get from this test alone. "

Ian

 

[canderson]

Thanks Ian,

I have tried and found the sweet spot was just touching the lands. My buddy's gun likes them 0.020 jump. Both of us were too hard headed and it took us several hundred rounds before we found the seating depth.

 

[JHardy]

Chris:

Your 56.8 grain load of 4831SC should give you more than 2907 fps. What length barrel? You did not mention (or I did not catch) whether you were shooting F-Class, 1000 BR or prone.

I have shot a lot of 284 Shehane from the prone with sling and jacket. My 57 grain load gave me 2951 fps with an ES under 5. I never had a vertical shot with that rifle that could not be explained by the conditions or my execution of the shot. Vertical will drive you nuts and is sometimes difficult to source the problem. Often, it can be recoil management. I am about 275 pounds and sling up very tight -- I don't even remember the recoil. If I made a mistake in butt plate placement, cheek placement or do something different with my grip, I (and anyone else) will get vertical.

What type of action and barrel? Who smithed the rifle? What length barrel? How is the action bedded? What scope or irons? How do you measure your powder charges? The answers to these questions MIGHT help a little in trying to find the problem. I can tell you this from experience -- if you determine it is the barrel, tomato stake it and get another.

Jim Hardy

 

[canderson]

The rifle is a BAT M action with a 31" 1.25 straight 1-9 twist barrel. The action has been properly bedded in a McMillan F class stock. I am shooting F class open with a nightforce 12-42. The action was smithed by Homer Strickland and the stock work by Tim Thompson. I use my rcbs chargemaster is meter the charges. The bullets are seated with 0.001 neck tension. I have been shooting the rifle free recoil. Thanks again for trying to help.

 

[AlanPF]

Chris,

Here's roughly what I do when trying to narrow down the cause of vertical. Firstly I see if there is vertical at short range (e.g. 100yds). If there is, then there's a huge number of possible causes. However its usually easier to test at 100yds (you can see the bullet holes), and I don't do any testing further out until 100yd accuracy is good. That's not the end of it however, because things like muzzle velocity variation and bullet BC variation will only cause serious vertical at the longs. When testing at the longs, I find it useful to use a chrono, to look for any correlation between muzzle velocity and point of impact.

So it will be interesting to see if you still get flyers at 100yds. If you do, then it may be a barrel problem, which you may be able to eliminate with tuning of loads.

Hope this gives you some ideas?

BTW thanks to Jim Hardy for making the 284 Shehane popular - I have one in the pipeline (almost ready except for bullet availability) - have been using a 6.5-284 for years.

Alan