Eric Stecker
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7MM Berger Bullet Groups
- Thread starter 284stak
- Start date
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NZ Longranger,
Thanks for the info.
Sounds like I might be able get a little more out of the standard 7 RUM and the 180's but not much seeing that the barrel is only 27" and I'm not using moly coated bullets.
Wayne aka WAMBO
Thanks for the info.
Sounds like I might be able get a little more out of the standard 7 RUM and the 180's but not much seeing that the barrel is only 27" and I'm not using moly coated bullets.
Wayne aka WAMBO
284stak
Well-Known Member
Eric: I have tried the 168 VLD's from .025 jump to .020 into the lands. I have used Retumbo, RL-22, RL-25, H-1000, and 7828ssc --- none of these variables seemed to help. I emailed Walt - he gave me some advice, but in the end, seemed to agree that my barrel just will not shoot them. Seems suprising, as it is super accurate with the 140 accubonds - am going to try the RBBT ULD's once the new jackets are being produced.
johnnyk
Well-Known Member
284...I've still not gotten mine to shoot less than .906" with the 168gr...When this box runs out, they're out...JohnnyK.
rufous
Well-Known Member
Eric Stecker, I am curious as to why the Berger VLD bullet seems to generally shoot best when jammed into the lands while most other bullets generally shoot best when just touching to about 0.030" off the lands. Thanks, Bruin.
The Berger 168 VLDs shoot great in my 7mm WSM Savage 16FCSS. I load them to just short of the factory 3" detachable mag box (OAL=2.995") and when chambered I can see a slight throat engagement ring all the way around the bullet with no land marks. This is the first time I have ever seen throat engagement (lead?) instead of land marks. Solid ring around bullet instead of lands.
I tried them seated off the lands at a shorter OAL but they did not group much better than 1 1/2" at 100 yds seated deeper.
Found a new way to check engagement into the lands also, take the Crazy Cloth and polish the bullet to a real good shine on a loaded round. Chamber it and then remove. Throat and or land engagement shows up great on a highly polished bullet.
Works much better than putting soot on the bullet from a flame or using a majic marker to color the bullet ...
I tried them seated off the lands at a shorter OAL but they did not group much better than 1 1/2" at 100 yds seated deeper.
Found a new way to check engagement into the lands also, take the Crazy Cloth and polish the bullet to a real good shine on a loaded round. Chamber it and then remove. Throat and or land engagement shows up great on a highly polished bullet.
Works much better than putting soot on the bullet from a flame or using a majic marker to color the bullet ...
MagMan
Well-Known Member
Wambo, We had emailed each other a month and a half or so ago and I told you I would get back with you regarding some testing I was doing.
30" Rock 8.7 Twist APS 7mm RUM
It seems I can achieve 3350 fps with the 180 Berger's and US 869. US 869 seems to be a pretty amazing powder everything else pressured out around 3250 (Retumbo, RL 25, IMR 7828 and H870) but US 869 seemed to surpass that by 100 fps without building super high pressure. There were slight ejector marks but nothing I would consider extreme for an Ultra Mag.
This is just part of my velocity string
95 grains (starting load) - 3167 fps
99.1 (seemed to be the most accurate) - 3333 fps
100.3 two showed no ejector mark the third did - 3350 fps
I didn't adjust any OAL's and they were loaded quite a ways from the lands (.050 ish) but they all held at least MOA out to 600 yds.
I started doing velocity testing on the 200 Wildcats and US 869 but haven't gotten very far (ran out of bullets). I do know that 92 grains (which is a starting load) of US 869 out of my 30" Rock barrel will get you 3000 to 3016 fps away from the lands and 3060 - 3080 fps jammed into the lands. I'd be willing to bet I could get at least 3150 - 3200 with the 200's and US 869.
For now I have chosen to shoot the 175 SMK because it seems to be the most accurate (92 grains of H 870 @ 3241 fps). H 870 has proven itself to be more accurate than US 869 at least in my rifle any way.
30" Rock 8.7 Twist APS 7mm RUM
It seems I can achieve 3350 fps with the 180 Berger's and US 869. US 869 seems to be a pretty amazing powder everything else pressured out around 3250 (Retumbo, RL 25, IMR 7828 and H870) but US 869 seemed to surpass that by 100 fps without building super high pressure. There were slight ejector marks but nothing I would consider extreme for an Ultra Mag.
This is just part of my velocity string
95 grains (starting load) - 3167 fps
99.1 (seemed to be the most accurate) - 3333 fps
100.3 two showed no ejector mark the third did - 3350 fps
I didn't adjust any OAL's and they were loaded quite a ways from the lands (.050 ish) but they all held at least MOA out to 600 yds.
I started doing velocity testing on the 200 Wildcats and US 869 but haven't gotten very far (ran out of bullets). I do know that 92 grains (which is a starting load) of US 869 out of my 30" Rock barrel will get you 3000 to 3016 fps away from the lands and 3060 - 3080 fps jammed into the lands. I'd be willing to bet I could get at least 3150 - 3200 with the 200's and US 869.
For now I have chosen to shoot the 175 SMK because it seems to be the most accurate (92 grains of H 870 @ 3241 fps). H 870 has proven itself to be more accurate than US 869 at least in my rifle any way.
MagMan,
Thank you very much for the info, it's just what I was looking for.
When my friend has his rifle back from Shawn we'll be testing the 200gr Wildcats with US869 and WC872 as I think they will give the top velocities.
I was thinking about trying WC872 in the 27" 7mm RUM with the 180's just to see if I could get more speed then I was getting with Retumbo, looks like I probably will but accuracy trumps top speed so only time will tell.
Wayne aka WAMBO
Thank you very much for the info, it's just what I was looking for.
When my friend has his rifle back from Shawn we'll be testing the 200gr Wildcats with US869 and WC872 as I think they will give the top velocities.
I was thinking about trying WC872 in the 27" 7mm RUM with the 180's just to see if I could get more speed then I was getting with Retumbo, looks like I probably will but accuracy trumps top speed so only time will tell.
Wayne aka WAMBO
Eric Stecker
Well-Known Member
- Joined
- Jul 27, 2007
- Messages
- 292
Bruin,
The VLD design uses a secant ogive which has an abrupt transition from the bearing surface to the ogive. It seems that this abrupt transition is sensitive to alignement. This has not been proven through controlled testing but the conventional wisdom is that this has an impact on results. If the bullet starts out straight and held straight by the rifling then the bullet is more likely to come out of the muzzle straight resulting in less yaw while the bullet moves from spinning around the axis of the bore to spinning around the axis of the bullet. If the bullet is forced through the barrel with the tip not in line with the axis of the bullet is will produce mcuh greater yaw once the bullet exits the muzzle. This is bad for precision.
There are some folks who are really sharp with math who claim that the amount of yaw that is possible from this situation is too small to make a difference. I am not a math wizard and cannot argue this point. I do know that typically if the VLD does not shoot when jumped (in many rifles it does) then precision can be improved by putting the bullet into the rifling. It seems that alignment is the only thing that is effected when the bullet is successful when jammed.
When neither a jam or a jump produces the accuracy you want there is usually something going on with the barrel. This could be from an uneven throat or throat erosion. The VLDs are sensitive to such things and if everything is square and right you should not have a problems getting them to shoot well. These are the same bullets used by target competition shooters all over the world with excellent results. We do not have a "match" bullet and a "hunting" bullet. They are the same bullet and if they do not work in a given rifle then something is not squared away. This can be challenging to resolve.
Another thing to keep in mind is that our 7mm and 6.5mm bullets are the most streamline VLD we make meaning that they are the most sensitive to such things. We have just finished making some 6.5mm 140 gr (non-VLD) which are meant to be used when the VLDs do not work. It will not be long before we introduce our 7mm (non-VLD) as well. The real trick will be to make sure they perform on game the same way the VLD do. So far the non-VLD have not been tested on game.
Regards,
Eric
284stak
Well-Known Member
So basically, my smith must have done a bad job on trueing my action and cutting my chamber/throat as the gun does not shoot the VLD's at all - again, lucky to get 3 MOA out of them. That may be the best explanation for the problems I have had with them, but hard to explain my 3 shot 140 AB group at 825 yards yesterday - 3/4 inches vertically and 3 3/4 horizontally. The only other shoot I took was at 600 to get a better idea on windage. I guess the explanation would be that the AB has a thicker jacket and therefore can take more abuse from a bad throat/barrel combo.
"give the bullet a chance to stabilize"? I understand why you would sight at longer distances for other reasons but your bullet does not have fletchings on it like arrows. I always thought your bullet is either stabilized right out of the muzzle because of the right twist rate in your barrel (and the quality of your barrel), barrel harmonics (the right node), or it's not. Either the quarterback throws a lame duck or a tight spiral - not a lame duck that suddenly turns into a tight spiral.
How can a bullet that is on a plus moa path at 100 yards suddenly be .5 moa at 300? It can't just change directions from it's established course. I understand sighting in at 300 yards (and 800 plus for that matter) for reasons of validating your trajectory or measuring extreme spreads, etc. But allowing your bullet to stabilize???
How can a bullet that is on a plus moa path at 100 yards suddenly be .5 moa at 300? It can't just change directions from it's established course. I understand sighting in at 300 yards (and 800 plus for that matter) for reasons of validating your trajectory or measuring extreme spreads, etc. But allowing your bullet to stabilize???
Drenge,
I read what you're writing, I would like to be able to explain it.
I will just say that my 300 RUM Sendero will shoot tigher MOA groups at 300 yards than it will at 100 yards. How does it happen? I don't know but it happens. And just about every time.
I read what you're writing, I would like to be able to explain it.
I will just say that my 300 RUM Sendero will shoot tigher MOA groups at 300 yards than it will at 100 yards. How does it happen? I don't know but it happens. And just about every time.
