Range Report WTF when your groups blow up at long range?

[GJgo]

Yesterday I saw something that I saw years ago. Rewind.

Years ago I was working up loads for my Elk rifle, 300 WSM. I found a really great load w/ 168 TSX (secant ogive)- 3 shot groups ~ .5 moa at 100 yds. Consistent. One day I decided to click up & shoot 300yds for practice. Groups went to 2 moa. ?? So, I then worked up loads for 150, 165, & 180 TSX (tangent ogive). Groups were closer to 1 moa @ 100, but they were 1 moa at 300 as well. Hmm. Since then I have stuck with the 180s @ 3040 fps w/ H4350 and they get the job done.

Yesterday I took my Savage 308 10FCP to the range. I found a couple good loads that I wanted to stretch out & see how they held up. Win brass, BR2 primers, .015 off lands. First load is 200 SMK (tangent ogive), 47.5 RL17, 2640 fps (temp sensitive btw), 5 shot groups about 1 moa @ 100. Next is 178 Amax (secant ogive), 45gr Varget, IIRC 2790 fps, .75 moa 5 shot groups @ 100.

First I ran at 100 to do a reality check and it was as expected. 5 shots smk and then 5 shots Amax. Next I moved my target to 300 yds & clicked up. I ran a 6 shot Amax string that measured 2.5 moa. Finally I ran a 6 shot string with SMK that ran 1 moa.

I've always heard that tangent ogives are easier to tune, agreed. It seems to me though that either a) I'm crazy or b) sometimes a secant ogive bullet needs to be tuned depending on your distance- is this possible? Something I'm missing here? There was a light breeze but that wasn't it, the bad group was all over the place.

 

[Jeffvn]

Re: WTF when your groups blow up at long range?

Bullet shapes and load testing - different rifles like different things. My 1:9 twist KWM 7wsm loves Berger vlds, Sierra 180s, and likes the 175SMKs. But it HATES Hornady 162s. go figure.

100 yard testing is mostly a waste of time, at least for me, if I am looking for a load that shoots at 1,000 yards. I prefer to do as much of my testing as possible at the longest distance I can find for the wind conditions. It will dramatically reduce the time you spend on the development process.

If conditions are too windy to shoot at distance (400+), I will sometimes do 100 yard testing for the purpose of finding a minimum velocity (e.g. 2,900 fps - with my 7 WSM). Other than that, I do all my testing at 400 yards plus. If it groups at 400 plus, it will group at 1,000 yards and beyond. Under good wind conditions I can shoot through my chronograph and do load testing at 400+ at the same time.

Jeffvn

 

[Greg Langelius *]

Re: WTF when your groups blow up at long range?

Is the the scope parallax adjustable and set properly for the different distances? If the reticle appears to shift across the aiming point in sync with head movements behind the scope, it isn't; and that's where your groups' expansion is coming from. Parallax mismatch is the prime cause of unexplained accuracy inconsistencies that are related to different distances.

Greg

 

[AKAce]

Re: WTF when your groups blow up at long range?

100 yard groups are Lies... always.

Use 100 yards to Zero, 300 for load dev. Your loads just suck, not the bullets or their shapes.

 

[LawnMM]

Re: WTF when your groups blow up at long range?

I'm going to toss this out only because nobody else has yet. It could be that you are a better shooter at 100 than you are at 300.

That said, RL17 is VERY temp sensitive. I've had tuned loads with SD's in the single digits triple their value with as little as a 15-20 degree temperature change.

Rich

 

[GJgo]

Re: WTF when your groups blow up at long range?

You know, I've always done load development at 100yds because I figured it would minimize wind issues, and there's always some wind here. My local range goes to 300 though so that'd be easy enough to change. There's also a range out here that goes to a mile it's just not as convenient.

Greg- Yes, in both cases I adjusted the parallax when I went from 100 to 300. Remember, in both cases ceteris paribus I had expected results w/ the tangent ogive bullets in a back to back comparo- it was just the secant bullets that got weird. It's possible that my Amax load sucked, but it's a fairly common load from what I've read so who knows.

-side thought- Of course, this 308 barrel is funky. It shoots Federal 180 soft points 6 moa @ 100, Nosler 168 BTs 4 moa at 100, and Federal GMM 175 SMKs .75 moa @ 100. I wanted to try some heavies so I was playing around with the 200 SMK, but honestly the best it's ever shot was with FGMM 175s so maybe I'm chasing my tail. I've thought about re-barreling more than once.

 

[azimutha]

Re: WTF when your groups blow up at long range?

I think I'd rebarrel. A decent barrel in a .308 should be able to shoot SMKs and Accubonds/BTs into less than 1 MOA @ 100 yards.

My own WTF moment came Thursday morning. After having done changes to my stock and remounting the scope I shot @ 100 for an hour (10 shots every six minutes, alternating with lots of .22). Everything was great. Then off to shoot gongs @ 300. I aimed @ the 2" gong (no wind) and hit the 4" gong 8" away. Turned out the screws holding my SRS rail mount had worked loose and the bipod, although loaded, was going screwy.

 

[LawnMM]

Re: WTF when your groups blow up at long range?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: GJgo</div><div class="ubbcode-body">It's possible that my Amax load sucked, but it's a fairly common load from what I've read so who knows. </div></div>

What numbers do you get out of chronographing that load?

 

[GJgo]

Re: WTF when your groups blow up at long range?

I double checked my notes and the 45gr load is clocking 2790 fps with a spread of about 20 fps. 24" factory tube.

Here's a question. Other than the 175 SMK, what other tangent ogive bullets might I try in that weight range? (Or, should I even bother?) It looks like the Hornady 178 BTHP as well as the new Barnes Match Burner 175 (?) are both secant. I love Bergers, but to be honest they're out of the budget. Maybe Nosler 175 CCs?

 

[LawnMM]

Re: WTF when your groups blow up at long range?

20 for the ES? If so that's a pretty tight load. Is the group swelling primarily vertical, horizontal, or both? I imagine it grows more one way than the other.

I'm really not trying to bust your balls but a small lack of trigger discipline could be it. Try shooting a group at 300, dial back to zero and put one shot each on three dots 1/2" in diameter. Then shoot another group at 300. Take pics and post them and it will show a lot about what you, and your load, are doing.

Rich

 

[azimutha]

Re: WTF when your groups blow up at long range?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: GJgo</div><div class="ubbcode-body">Other than the 175 SMK, what other tangent ogive bullets might I try in that weight range? (Or, should I even bother?) It looks like the Hornady 178 BTHP as well as the new Barnes Match Burner 175 (?) are both secant. I love Bergers, but to be honest they're out of the budget. Maybe Nosler 175 CCs? </div></div>The Berger OTMs are $12-13 more per/100. It might be worth trying one box. Still, I'd be concerned that the barrel shoots such poor groups with some relatively easy bullets like the Nosler BTs. Until I burned through it, I even shot a mish-mash of .308 surplus given to me free and none of it ever shot worse than 2 MOA. I don't think I've ever put anything through the barrel of a .308 that didn't shoot at least that well without any tuning.

 

[sinister]

Re: WTF when your groups blow up at long range?

Sounds like you may need to get your barrel borescoped and replaced.

 

[GJgo]

Re: WTF when your groups blow up at long range?

In a roundabout way I think I may have found an answer. The last few weeks I've been sorting out a deer rifle, a Win 70 6.5 Swedish. I sorted out great grouping loads @ 100 with the 130 TSX & the 140 Amax- <1MOA. Took it out to 200 to zero, and same story- 3MOA or so. They were both running ~2850 which was safe pressure-wise with both H4831SC & H1000. So, I told myself that the Swede doesn't need to be fast to kill deer so I decided to turn it down & try it, only testing at 200yds. Bam! The groups started shrinking & today I found easy sub-MOA groups w/ both powders around 2700 fps & the 140 Amax. (Have to re-visit the TSX load later..) So, next I think I'll try turning down the wick on the other sticks & see if the same behavior occurs- looks like more accuracy nodes may exist at 100 yds than at longer distances. That's the theory, anyway...

 

[GJgo]

Re: WTF when your groups blow up at long range?

Just came across this thread, wanted to put in a final post on what I found with the Savage 308. As it turns out, there was a bad spot in the barrel about 1/2 before the end. Looks like the reamer got cocked at an angle or something right before it came out of the barrel & dug out a deep spot. Hacksaw + crowning tool later the problem is solved. Rounds are staying consistent in their MOA at varying distances.

That said, I did try running the new Barnes Match Burner 175s and they have been shooting enough better than the usual contenders that I've switched & not looked back. That they're the least expensive of the bunch is a nice bonus.

 

[MALLARD]

Re: WTF when your groups blow up at long range?

allot of BR or match shooters will not shoot 2 different jackets in the same shooting session. Something about different jackets lead to different copper build ups in the bore.

haha , if your having problems at 300 but not at 100 , i suggest you practice load development at 300y. If you get lucky you'll shoot 1 moa at 300y , and 3 moa at 100y , haha

 

[Bob 964]

Re: WTF when your groups blow up at long range?

What size targets are you using at 300 yds? The reason why I ask is that, when I am zeroing my Savage 110FP at 100 yds, I generally use a 5" target. When I used a 5" target at 300 yds however, my groups weren't as tight as I expected them to be. But when I switched to 12" targets at 300 yds, I started shooting much tighter groups.

 

[GJgo]

Re: WTF when your groups blow up at long range?

As I recall my 100yd targets are 2" & my 300yd targets are 6". Or so. I have a bunch of targets I downloaded form Benchrest Central. Sometimes I just put an orange dot in the middle of a sheet of white card stock so I can easier see the holes through the scope at long range- a lot of targets are too busy & make it hard to see. At any rate I'm happy with the setup now that I solved the problem, next is to run some aggs at longer range & see how it does.