BAD groups----need help

[BWE Firearms]

Try some 150-180 grain bullets and see how it shoots with and without the suppressor.

[Titleiiredneck]

Confirm its a 1-8 twist, and who made the barrel? Confirm by running a patch through the bore, mark where the rod is when you start and where it is when it makes 1 rotation, measure betwen the marks on your rod and thats the twist. check the muzzle for burrs, and whats the barrel oal and thread pitch on the muzzle?

[One Shot]

Some progress. I shot 3 rounds of 125 gr and 3 of 168 gr at super sonic speed and had 1 in groups. I'll try some 168"s with less powder and see what happens.
Thanks for the help. I'll keep you posted.
Doc

[LouBoyd]

Also confirm muzzle velocity, Preferable with a chronograph (buy or borrow). Measure EACH shot of at least a 5 shot carefully aimed group at 100 yards and note the point of impact and velocity of each of those shots. Preferably post a photo of the target with each shot and it's velocity marked. Take the velocities with the chronograph set about 10 feet in front of the muzzle. Most bullets will be more stable at 1000 fps than in the range of 1050 to 1300. So far no one as mentioned bullet velocity, velocity dispersion, or the shape of the groups. That's not to say faster velocities can't be used. Some bullets can have suffieient stablity across the entire transoinc range.

Before even doing shootnig test I'd have made sure my bullets are seated on or within .01"- of the lands, then worked up the the loads to give 1000 fps before doing any accuracy tests. I'd also have loaded ammo with its neck diameter between 0.002 and 0.005 of my chamber's neck.

If there is a lot of velocity variation and vertical stringing then you've probably got a problem with bullet seating depth and/or the fit of your cartridge to the chamber. If you loads are faster than 1050 fps but have uniform velocities then I'd expect a bullet stability problem. Groups could be any shape. Barrel twist and the specific bullet designs matter. Bullet weight an shape aren't the whole story. The interall mass distribution in jacketed bullets matters too. You can't determine a bullet's stability by looking at it ( though it is an indicator).

I agree on checking the barrel twist rate. (use a cleaning rod with a brush or tight patch. Mark the rod. measure to the mark, pull the rod for 1 turn of the mark, measure again to the mark and subtract. Be careful the brush or patch isn't slipping over the lands.

Also note the elevation, temperature, and barometric pressure when you do the tests. (air density is calculated from that those. Along with air density spin rate and velocity determines the stability for a particular bullet.

Please give the name and model of each bullet you use. Bullet weight and nose shape affect stability but they don't define it. Even the internal mass ditribution affects bullet stabity. The suggestion of using 220 grain Sierra matchkings isn't that they're more stable than other bullets, just that they're well known to give good performance. Other bullets may be more stable but not seat near the lands.

8 inch groups at 100 yards is terrible. It's not a subtle problem and the answer will be a head slapper when you find it.

[dick]

I had a problem like that. I was only shooting sub loads that had worked in other rifles. After I shot several strings of super-sonic loads of 150gr doing about 2000fps, basically breaking in the barrel. My sub groups are where they should be.

[One Shot]

Tried new stuff today. As my volocitys go down, my groups get wider. I was shooting smk 190 gr hpbt. First with 16 gr AA 1680 and shot 1/2 in groups. Then 14 gr, with 3/4 in groups. Then 12 gr with 1 1/2 in groups. My chrono didn't work, but all were supersonic. I'm going to try 10 gr tomorrow. The gunsmith who built this for me said it is a 1in8 twist.

[Rancid Coolaid]

I've had significant vertical stringing with loads using H110. I have moved to #9 and lil gun and seen marked improvement.

Try something other than H110, it seems to be sensitive to temperature and position in the case.

[Rikky Lee]

You say you are using 190 grain SMK - I'd suggest this is part of the problem.

Recommend you get a pack of 220 SMK and 240 SMK and try the same load development.

There should be a difference.

[FordPrefect]

Got into the whisper a few months ago. Had horrible issues with deviation and H110 powder. Consistent fast first round and a little better for the rest of the string. But still not very good. Hand loads using a scientific scale but still 30-50 foot deviation creating terrible vertical stringing. Switched to lilgun per this forum and now can get with careful measurements 3-5 shot groups with 3-5 fps deviation. Vertical stringing gone. Using 240 SMK though. Would like to also try VV N110 as I hear that is consistent.

Watch the chrono. If the shots are not extremely consistent they will not group well. Especially with heavy subs. This is just my experience so far.

[martineta]

I use H110 for both 125 and 150 grain Nosler Ballitic tips at supersonic velocities. So far every deer I have pointed at died and shooting paper tiny groups with no verticle stringing at all. I shoot a 26 inch Encore stainless with Thompsons´s 1 in 12 twist. I shoot paper when its summer time and shoot deer in 0-60 F degrees. Haven´t noticed any changes that I can see. You shoot em the chest and they fall down. Is the verticle stringing with H110 a subsonic thing because I sure haven´t noticed it shooting supersonic with a long barrel?

I did buy a can of vv110 and a box of 220 matchkings to load subs. My new SSK Encore barrel came to the house the other day. Looking forward to seeing what I can do with the big bullets quietly. I will apply for the suppressor stuff and put a can on after this hunting season.