I have problems (of the load development kind)

G'day Boys, Girls, and Gimp
After going for a range session with a new bipod that works (a super gucci dealextreme jobby), I was a bit confused as to what the results may mean.


I fired two 4 shot groups of the same load as follows:

Tikka T3, .308 winchester
Lapua brass (3rd firing approx)
190 berger VLD Hunting
46gr AR2208 (no pressure interestingly enough)
Federal 210 Primers
2664-2755fps velocity spread over 2 4 shot groups

16 deg
994hpa (not that it really matters)

I gave the rifle a rest for 5 mins in between groups, and tried not to bugger around too much with the round in the chamber, so the powder shouldn't have heated up too much.

Attachment 256

1st Group:
1 2664
2 2669
3 2688
4 2705

2nd Group:
1 2672
2 2708
3 2734
4 2755

SO..
Velocities climbed throughout the test, the first group stringed horizontally, and the second one stringed vertically, with similar overall group size.. is there any explainable reason for this to happen? If it was spraying the rounds all over the show I'd probably just can the VLD's, but it seemed to be doing similar things when testing other loads with VLD's in the past. I really wouldn't mind finding a way to get these bricks shooting, they kick ass in terms of wind drift, retained energy, and velocity past 500.. If they didn't boot like a mule they'd be ideal!

Any ideas re: the velocity change/grouping?

Cheers,
Kitto

Whats your twist rate?? relatively heavy pills for the .308. is it fast enough to cope with the heavy pills?

Thats also quite a large velocity spread. which would explain you vertical stringing. Horizontal stringing can be from poor bedding of action. have you always used a bipod for your load testing?? I prefer to use a proper bench rest and rear sandbag to remove as many variables as possible.

Tikkas normally don't need bedding jobs, but thats not a given.

I had very similar issues with a brand new rifle I purchased last year. Get small glimmers of excellence then i get what you are getting. Ended up taking it to Deam Maisey and discovering my chamber is not concentric to my bore therefore no matter how well I load my rounds the projectile will always enter the bore at an angle, therefore I will always get inconsistent results. :TT TT:

Saving up for a true flight ultra match barrel now. :thumbsup:

I was pretty dubious as to whether the 190's would stabilise either, as the twist is 1-11 on tikka 308's with a 22in barrel. However, the Berger site says 1-12 is all good for this bullet, and I would've thought that 2700 is enough in the speed department. If that IS what they are actually doing.. From what I've seen, some larger .30 cals such as 300wsm are only loaded to similar velocities. Probably because their owners don't have a chronograph! The bullets aren't tumbling either, and perform out to 650m, so surely they are stabilising.

I always have used a bipod, as I'm too lazy to set up a proper bench rest etc. I also have a rear stock rest bag thingy, which was kindly donated by gimp. I've always thought this was suitable for sub moa groups, which is all I'm after at the end of the day. This is also the setup I use on the hill, so thought that this consistency of rest would minimise POI change.

One very valid point you've brought up is bedding. would it be possible that I've not refitted the stock properly after cleaning etc at some point? It could also be possible that I have overtightened the bedding screws. I usually tighten the back screw as much as possible, then tighten the front one down to a reasonably tight level.

Don't get me wrong, I've developed about 5 loads that shoot like a dream, using 150 nosler BT's, Sierra Matchking (SMK) 168's, hornady 150btsp's, barnes 168 ttsx's, and Sierra Gamkings. On one particular day, I got 3 groups of 3 shots under 1/2 inch easily in a row with the NBT's. So shouldn't be a problem with the rifle fundamentally. It's just a problem that's cropped up recently.

It could just be that I need to be jamming the bergers in the lands.. I could be getting similar problems to your incocentric rifle, in that the bergers may not be hitting the rifling perfectly square. There's about a 120-140 thou or 3mm ish jump from memory.

Cheers

If you are getting great groups from other loads then my guess would be that 190's may be a little too heavy for your barrel. Fair enough on the bipod and bag, especially if you have been doing it for some time with good results. I always though that the secant (sp) ogive of the VLD's and the Amaxes alike prefer to touch the lands or be just off to achieve optimum results. so your comment about juamming them in could be the next option, you may have to back off a little with the powder as to not get a pressure spike.

Your velocity spread is still an interesting factor almost 100fps difference. thats a lot I would have thought!

You must like to tinker if you have all those other loads humming nicely in your Tikka. :thumbsup: nice!

The problem with the other ones is they are all pills with pretty average B.C's, and they didn't get anywhere near the sort of velocities (comparitively) that I'm getting with the 190's. I could only get 2750 out of the 168's before they started flattening primers etc, I'm guessing the powder wasn't completely burning in the barrel.

The first 3 groups I shot with the rifle 3 years ago were all factory ammo, and all around 3/4 inch! there's no challenge in sticking with something that works!

The other thing I considered when doing some testing with the same pills initially was that I could be just flinching, as they do give a fair wallop. I don't think I'd be getting trends such as these developing if this was the case though

One very valid point you've brought up is bedding. would it be possible that I've not refitted the stock properly after cleaning etc at some point? It could also be possible that I have overtightened the bedding screws. I usually tighten the back screw as much as possible, then tighten the front one down to a reasonably tight level. [/QUOTE]

I could be off here But Iv allways thought you should do it the other way round as there is usualy some bedding area forward of the tang area and over tightening this screw can tweek the action?

A couple of things, first yes vietmancam is correct, tighten the front screw first then the rear to not quite so tight,for a T3 id use 55 inch pounds on the front and 45-50 rear,but if its been working for you doing it your way then its unlikly to be an isse.Make sure the floating recoil lug in in its correct position.Are these the first loads youve tried with this bullet? if yes then the simple answer is you just havent found the right powder charge ,seating depth combination yet.Picking one load and hopeing is like buying a raffel ticket.The vlds can be very sensitive to seating depth
The other thing to remember is heavy higher recoiling loads can be harder to shoot off bipods in light rifles.

Quote:

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Originally Posted by Kitto

I was pretty dubious as to whether the 190's would stabilise either, as the twist is 1-12 on tikka 308's with a 22in barrel. However, the Berger site says 1-12 is all good for this bullet, and I would've thought that 2700 is enough in the speed department. If that IS what they are actually doing.. From what I've seen, some larger .30 cals such as 300wsm are only loaded to similar velocities. Probably because their owners don't have a chronograph! The bullets aren't tumbling either, and perform out to 650m, so surely they are stabilising.

I always have used a bipod, as I'm too lazy to set up a proper bench rest etc. I also have a rear stock rest bag thingy, which was kindly donated by gimp. I've always thought this was suitable for sub moa groups, which is all I'm after at the end of the day. This is also the setup I use on the hill, so thought that this consistency of rest would minimise POI change.

One very valid point you've brought up is bedding. would it be possible that I've not refitted the stock properly after cleaning etc at some point? It could also be possible that I have overtightened the bedding screws. I usually tighten the back screw as much as possible, then tighten the front one down to a reasonably tight level.

Don't get me wrong, I've developed about 5 loads that shoot like a dream, using 150 nosler BT's, Sierra Matchking (SMK) 168's, hornady 150btsp's, barnes 168 ttsx's, and Sierra Gamkings. On one particular day, I got 3 groups of 3 shots under 1/2 inch easily in a row with the NBT's. So shouldn't be a problem with the rifle fundamentally. It's just a problem that's cropped up recently.

It could just be that I need to be jamming the bergers in the lands.. I could be getting similar problems to your incocentric rifle, in that the bergers may not be hitting the rifling perfectly square. There's about a 120-140 thou or 3mm ish jump from memory.

Cheers

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I think you'll find its actually 1 in 11", just to be pedantic

Quote:

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Originally Posted by Mike H

I think you'll find its actually 1 in 11", just to be pedantic

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Shite, you're right Mike! I've always been sure that it was 1-12 - not sure where I pulled that number from.. I'll correct the original post.

Does 1 inch faster twist make much of a practical difference? Could that possibly explian the better performance of the heavier bullets as opposed to the 150's in terms of velocity?

what page are you looking at?Berger list the 190vld part # 30154 as best in 1-12 the 210.gr is 1-11.Id take Litz's recomendation.I dont think you have a stability problem.

Its unlikely to be a twist rate problem, we already know the rifle shoots two other loads well so its probably the problem alot of people have your rifle just dose not like the berger VLDS and in your case the 190gr.

have you tried different seating depths? FOllow the berger suggestion of how to tune a load starting at just touch and working back, one of mine shoots best at 120 thou jump, another likes them at 40
instructions from Berger (it works)
.010 off the lands (jump) 6 rounds
.050 off the lands (jump) 6 rounds
.090 off the lands (jump) 6 rounds
.130 off the lands (jump) 6 rounds

Shoot 2 (separate) 3 shot groups in fair conditions to see how they group. The remarkable reality of this test is that one of these 4 COALs will outperform the other three by a considerable margin. Once you know which one of these 4 COAL shoots best then you can tweak the COAL towards or away from the lands .002 or .005. Taking the time to set this test up will pay off when you find that your rifle is capable of shooting the VLD bullets very well (even at 100 yards).
Velocity spread was reasonable with the cold barrel suggesting the warm barrel is causing the rise in fps. I would back load off a little, do the seating depth test then look at bumping load up again, did you arrive at 46gr as the most accurrate load or purely on velocity?

Interesting feedbak here suggesting 175gr could be a better option

.308 Winchester (7.62 NATO)

The old 190 grain VLD was a grenade, even at .308 Win velocities it was spectacular, exploding into multiple fragments of around 7mm (.250”), one could have expected time dilation at the ‘event horizon’ and gravity to pull the hunter into the carcass. Again, this bullet has been revised. In truth, the 190 grain bullet weight is not well suited to long range hunting using the .308 and of the VLD line, the 175 and 185 grain bullets strike the balance, twist rate being the final deciding factor between the 168, 175 and 185 grain bullets. As has been previously mentioned, it is quite a challenge to shoot and kill game cleanly beyond 650 yards with the .308. The 175 grain VLD launched at 2600fps is down to around 1630fps at this range. Wounding is definitely tapering off at this velocity (current VLD design) and 850 yards (1400fps) should, for the sake of the animal, be considered absolute maximum for fast bleeding. It must be reiterated- target resistance is an important factor in this equation.

Cheers for the replies guys,
I arrived at 46.5 gr mostly due to velocity, as group size did not vary much at all on the basis of powder charges. I imagine this is purely because I haven't got the seating depth right though, as horihunter said, that will probably be the main source of error.
Interesting read on the BallisticStudies site, I'd looked at the 185gr pill as an option but chose the 190 purely due to higher B.C.

On an unrelated note, I shot a hare with this load a few weeks back @50m, which very surprisingly didn't die straight away. It was a lower chest shot, and I had to give it a coup de grace.. This was the first time I'd had to finish off a hare after shooting it with the .308

That doesn't surprise me about the hare. I've seen them soak bullets up from the .223 and thought I'd missed, even at close range. Gut shot em and you know.

Problem now solved!

Changed from 190 to 185 Berger VLD hunting's (0.3BC Drop)
Reduced load back to 44gr, and started working up in 0.3gr increments. 45 shot sweetly
Got a muzzle break from Waitaki Engineering $220 fitted
Got a 20moa rail and warne rings from Waitaki as above $180 from memory
Stole one of Gimp's stock packs

Don't have any photos, but from what I remember, it shoots well now. Claimed 1 tahr and 2 deer with this load. It seemed to do pretty well at 300m ish, haven't tested it close up yet. Also went better than I did at the LR shoot, and offended all those who shot beside me.

Cheers for the advice though tussock, you're most likely right! The muzzle break's made it managable to shoot more than 20 rds in a sitting now

Not manageable to be anywhere near, though.