Vertical Stringing

aocasek · Post by **aocasek** » Fri Jul 27, 2007 2:57 pm

Hi All,
I spent some time at the range today shooting my loads at 300 yds and I had some problems with vertical stringing. I'm posting it here but I'm not sure if its my load, the gun, or maybe my shooting form.

My first load is the 39 BK over 26.1 of H4895. This loads shoots an average 3580 but the spread (I thought this might be the problem but see below) was around 90. The case is a winchester with a CCI BR4. O.A.L. is 2.250. Cases were primer pocket uniformed, flashole deburred, and neck sized, trimmed. Length was 1.840. At 300 yds 5 shots went into a .5 inch wide group that streched to 2.5 inches in length. The smallest 5 shot group I shot at 100yds with this load was .296 and it consistently will put five under .5

Second load was the 32 v-max over 22.5 of IMR 4198, BR4 primer, and 2.250 length. Scase prep as above. Velocity is 3700 with a spread of 49. This load, at 100 yds will shoot .3's and I'll occasionally get to the .2's. Smallest was .196. This load performed the same way as the above load at 300. 5 into a .5 inch wide group that stretched 2 inches or so north to south.

Any suggestions on why this is happening? I thought it might be the spread with an inconsistent velocity but the v-max load is more consistent and it did the same thing. Could it be my rest? I shoot a short bipod off the bench with sandbags in the rear. Any input would be good, as I thought I had two good loads but I'm disappointed with the performance at 300.

Thanks,
Adam

glenn asher · Post by **glenn asher** » Fri Jul 27, 2007 3:01 pm

Sounds like ignition to me, try bumping up your charge somewhat, that's awfully mild, a stiffer load may burn better. Just an educated guess, though.

Rick in Oregon · Post by **Rick in Oregon** » Fri Jul 27, 2007 3:06 pm

Adam: The usual culprits to vertical stringing can be a bedding issue, such as the barrel touching the forearm of the stock, neck tension being inconsistent, or wide velocity swings with a given load.

If you've checked your bedding, I'd next look at your velocity SD's with a chronograph to see if wide variations exist.

In any given string, a faster bullet will strike higher on the target, and the slower bullet usually will strike lower in the group. That's a starter, let us know how it shakes out.

skipper · Post by **skipper** » Fri Jul 27, 2007 3:46 pm

Speedy Gonzales wrote an excellent article on vertical stringing. I have read it several times. It will give you lots of good information and suggests several things to check. I won't try to reinvent the wheel here with my own ideas.

http://www.6mmbr.com/verticaltips.html

.204 Sniper · Post by **.204 Sniper** » Sat Jul 28, 2007 12:21 am

Make sure your stock screws are tightened down to 65 Inch Pounds (NOT Foot Pounds!).

I usually free float my barrel, then add a Sims String Leech (for bows) as a pressure pad under the barrel about 2 inches back from the fore end.

This 'tunes' the harmonics and seems to stop stock 'slap' that bumps the barrel in varying degrees under recoil. It makes the stock more 'consistent' during recoil.

This process brought my .308 down into the .2's at 100 yards.

Start with the stock screws - if it still happens try the pressure pad. You won't be disappointed.

jo191145 · Post by **jo191145** » Sat Jul 28, 2007 5:01 am

All great advice so far and the answer is probably in there somewhere.

Just to add to your confusion let me throw in a few more possibilities

Try ditching the bipod for awhile. You do not need a BR rest in front but sand on both ends might help. Pods can really mess with rifle harmonics especially if your using a bench. You can also try nailing/clamping a 2x4 to the bench in front of the pod legs and adding a little preload to them by gently pushing with your shoulder.

I've seen plenty of light loads that work at 100 but fall apart at longer ranges. The fact that both loads shot the same vertical groups suggest theres more than that at fault here. Still couldn't hurt to try redeveloping your loads at longer ranges.

Head wind ? tail wind?
Parallax Sure you dialed the vertical out of your scope?

Do your loads show any sign of vertical grouping at 100yds?

In "Secrets of the Houston Warehouse" theres a short sentence concerning load development and stringing. Mostly concerns BR guns jammed into the lands but it sure seems to work for me even jumping. Goes something like this.

Loads seated short with light charges produce vertical stringing. As you seat the bullet farther out and increase the charge the load will eventually produce horizontal groups. The trick is to find the point in between.
Most likely this is not your problem but it couldn't hurt to seat those bullets out a little and search for a stiffer load. Good Luck

aocasek · Post by **aocasek** » Sat Jul 28, 2007 10:38 am

Thanks guys for all the tips. I think I'm going to try losing the pods for a start. Hopefully that simple fix will help. If not, I'll tweak the load. The gun is a 527 varmint kevlar and the glass is a leo vx-II 6-18 and since I've had this rig I've found that it shoots best with slightly over mid-range loads. What I've found is that when I get up around max, the bottom usually falls out and groups open to inch and a half so increasing the load wouldn't be my 1st choice.

Do you think another primer would be a better fit, like a magnum primer (I have some CCI 450's lying around) instead of the BR4? I think I have the scope adjusted correctly so thats probably not it but I'll double check to make sure. I'll let you know what I find.

jo191145: I noticed you're from CT, I happened into a ruger 77/22 hornet and wanted to get it cut to K-Hornet and I found a company called Connecticut Precision Chambering. Have you ever heard of them? I talked to the guy and he seemed knowledgeable but I wanted a little more info before I made a decision to have them do it. Thanks for all the help.

Adam

Rick in Oregon · Post by **Rick in Oregon** » Sat Jul 28, 2007 12:00 pm

aocasek: The 204 (223 case family) does not require a magnum primer for about any powder suitable for the case.

But if you decide to try it anyway, be sure to back off your load and start from a starting load, as you'll be changing all the pressure parameters.

jo191145 · Post by **jo191145** » Sat Jul 28, 2007 3:18 pm

aocasek wrote: jo191145: I noticed you're from CT, I happened into a ruger 77/22 hornet and wanted to get it cut to K-Hornet and I found a company called Connecticut Precision Chambering. Have you ever heard of them? I talked to the guy and he seemed knowledgeable but I wanted a little more info before I made a decision to have them do it.
Adam

I found CPC back when I turned from a shotgunner/pistolero type guy to a centerfire freak. Unfourtunately I chose a mini-14 in that highly accurate .223 Remington round as a first. Ended up taking a leap of faith and trading that mini for a yet unreleased Sav 12 VLP in a totally new cartridge called the 204 Ruger. Haven't missed the mini yet.

So I never spent a big chunk of change trying to make that mini accurate.
Never did business with CPC or any other mini accurizing company.
I did relook through CPC's site. Seems they've grown some since 2004.
Don't know anything about Ruger 77/22 accurizing.
It does seem they do though. Or are you just looking for the rechambering?
Maybe some of the forum members more knowledgable than I could peruse they're site and formulate an opinion.

http://www.ct-precision.com/

glenn asher · Post by **glenn asher** » Sat Jul 28, 2007 3:41 pm

They DO have an outstanding reputation for taking a pig of a rifle and making it shoot a lot better. They specialize in the smaller Rugers, like the Hornet and the rimfires, but also tackle other problem rifles. They've gotten good press, anyway, I have no personal experience with their work. They did have a production rifle "package" where they'd recrown, bed, and tweak triggers, etc. them for, IIRC, about $175.

aocasek · Post by **aocasek** » Mon Jul 30, 2007 7:39 pm

Price went up a bit but I think its still a pretty good deal, for the 77/22 hornet they will recrown, tighten the infamous 2 peice bolt, recut to K-Hornet, and do the trigger for about $240 incuding shipping. Hopefully that reputation holds true cause the 77/22 hornet I have is a dog...got a 3 man slingshot thats more accurate!