Split groups

[Weairy]

Having some trouble at the moment tuning a rifle. We keeping getting splits in groups when testing.

Two different barrels, three different projectiles, several different loads, two different scopes, two different stocks. Beddings good. Scopes and mounts are good. Runout is spot on with loads. Shooting two shots almost touching, but the third throws out an inch. Photos tell the story.

Anyone experienced this? Any thoughts?

7SAUM at 300yd

[argh]

Josh,
I had a 308 barrel that would put fliers in most groups. Normally one, maybe 2 per 10 shot group. I tried all different loads and seating depths, until I jammed hard (.010 in), that was the only fix I could find. At jumping projectiles it just would not shoot consistently.
Cheers
Adrian

[Weairy]

Josh,
I had a 308 barrel that would put fliers in most groups. Normally one, maybe 2 per 10 shot group. I tried all different loads and seating depths, until I jammed hard (.010 in), that was the only fix I could find. At jumping projectiles it just would not shoot consistently.
Cheers
Adrian

Thanks for the reply Adrian. Tried everything from 15 Jam to 20 Jump with not much improvement so far.

[tachyon]

It's possible you just have 2 ordinary barrels.

I would agree with argh that jamming works best. The COAL where hard jam occurs is dependent on neck tension but I've found about 20 thou back from that to be good. That is about 20 thou longer than touch with my reamer and Berger 200.20x in 308.

Something I have noticed is that many Remington style actions do not have 250 thou of firing pin fall (this was tested as being best). Minor differences in triggers and hangers see this vary. My Panda came with 220 thou of firing pin fall and hummed away well enough to win more or less everything for about 6 months, then it stopped shooting.

The fix was 3 things:

Step 1 was jam.
Step 2 was to replace the firing pin spring - this improved ES and SD and was noticeable on the target.
Step 3 was to get a 30 thou offset hanger so the firing pin had the full fall (and yes this does produce a slight cock on close)

Prior to doing those 3 things I was about to give up on this particular barrel, but it seems to be shooting fine now.

51245.jpg

[saum2]

Do you wonder if 58.8 is the correct powder charge for the barrel?

[Weairy]

Do you wonder if 58.8 is the correct powder charge for the barrel?

Should it ever stop blowing, we'll find out. Got some loads set in the 57s to try

[BATattack]

I'd say bedding first even though you think it's good. Also 58.8 of what? Too hot for 2209, too low for 2217?

What is your ES doing during these odd shots? If the ES is good then the problem is probably mechanical. If not then it's something to do with your ammo

[Weairy]

I'd say bedding first even though you think it's good. Also 58.8 of what? Too hot for 2209, too low for 2217?

What is your ES doing during these odd shots? If the ES is good then the problem is probably mechanical. If not then it's something to do with your ammo

Thanks for the input.

Two different stocks, two different actions. Both Barnards on Barnard bedding blocks. Both proven with 308 barrels. Checked all clearances etc again last night, re-torqued everything to make sure, so we're 100% convinced it isn't the bedding.

58.8 of 2213SC. Ladder test shows the node there. ES within 2-3fps on these shots, around the 2920fps mark.

Shouldn't be shooter error; can lay down straight after with a proven 308 and keyhole-cut 5 shots without any issues.

Really, really strange one.

[BATattack]

What brand of barrels? Myself and at least one other person I know have had barrels with incorrect twists and possibly bore diameters recently. Tried several different brands of projectiles and different powders and ended up shooting a raggard hole with some light weight "fouling" ammo. It was repeatable so measured the twist and it was .6" out to what was ordered.

[FlashG]

Weaire, I had exactly the same problem.

1/9 krieger - 7mm shehane - about 600 rnds -2013c --180 & 168 bergers. Both projectiles affected for last 100 rnds.
Started shooting 2 to 5 shots into centre then dropping low left bull eye or inner at longer range.
Because of shortage of cleaning stuff I hadn't been completing cleaning.
Offhand comment by other 7mm shooter was 2013c with stout loads was badly fouling barrel. He changed to 2209 and found fouling was a lot less.
Made up homemade carbon cleaner Ed's red recipe (cheap and works as good as any). Using 308 copper brush found tight spot about 5 to 6 inches forward of chamber. Soaked well and got lot of carbon strips out. Barrel then de-coppered with last of bore tech.
Repeated all clean. Good to go.
After finding a comment on google from America (how many nuclear physicists, rocket scientist and ballisticians are there in USA) a common cause of low left occasional shots is caused by barrel fouling and or inconsistent loads from faulty scales.
Commentator thought fouling slows twist and velocity ie. causing low left shots.
I found also my AND123 scales had been lying with creep a problem. Now calibrate every 4 weighs and alls good.
My problem is now solved and rifle making me look good.
Cheers Flash.

[Pablolig]

May I ask if you have used a borescope?
I had an older barrel 284 that slowly started to open up groups.
I was meticulous with my cleaning regime.
Never wanted to use abrasives, until I thought I had nothing to loose.
Groups and odd shots disappeared!
I used Iosso bore paste.
Just another angle

[Weairy]

What brand of barrels? Myself and at least one other person I know have had barrels with incorrect twists and possibly bore diameters recently. Tried several different brands of projectiles and different powders and ended up shooting a raggard hole with some light weight "fouling" ammo. It was repeatable so measured the twist and it was .6" out to what was ordered.

Benchmark and Krieger

[Weairy]

May I ask if you have used a borescope?
I had an older barrel 284 that slowly started to open up groups.
I was meticulous with my cleaning regime.
Never wanted to use abrasives, until I thought I had nothing to loose.
Groups and odd shots disappeared!
I used Iosso bore paste.
Just another angle

Always borescope, huge on cleaning. Boretech, Sweets, Hoppes and Iosso/REM X40 as required

[AlanF]

Craig,

I've only had one barrel that did this and the problem remained until it was rechambered. The symptoms were similar, with two different groups, in my case about 1 MOA vertically. Over the course of the shoot it tended to "migrate" from one POI to the other, but with nothing in between. I believe there was something in the threading or other contact between barrel and action that was unstable and as the barrel heated, it changed. Some people said the barrel may have not been properly stress relieved, but I decided that route was too hard to pursue, so tried a rechamber and it worked. My advice would firstly be to try some different torque levels when tightening the barrel. Then if still there consider rechambering/rethreading.

[GSells]

Borescope it ! Maybe hard carbon issue ? Paste with a patch back and forth 10 times . Dry patch 5 times , then borescope again . Repeat to shiny clean but don’t over do it and definitely don’t use a bronze brush only patches ! Can stuff barrel ! Make sure you patch out with Kero and don’t leave any paste medium in the barrel. For me , I would do some test groups at 100 m’s to take any conditions out of the equation and check group shapes 3-5 shots each group ? Then if it still shoots bad possibly barrel or chamber problem? Could also be the rifle isn’t balanced in the bags and now recoils very differently and May need a new technique to shoot ? There are so many variables and could be a number of things ? But borescope first I would think.