Did not perform as expected

[TackDriver284]

A few weeks ago, I tested a few 3 round groups for hunting for the 308 using H4895 and 150 SST Interlocks. Worked up from 44 grains to 45.6 and did not use a chrono at that time, and checked for pressure signs and there was none. The best charge was 45.2 grains which shot a ragged hole @100 . The other day I made 15 rounds of 45.2 grains H4895 to test and sight in for deer season and took the chrono this time, and unfortunately it did not shoot like it used to, and it was very humid, some groups were .75- .9 MOA instead of the .2 MOA I done previously a few weeks ago. After firing several rounds thru the chrono, and ES spread was 6 and velocity average was a whopping 2980 fps. That is close to 30-06 speeds. Hodgdon data shows 45.5 grains as max with a 150 Ballistic Tip @ 2800 ish. Before I have fired the rounds today, I have shot about 80 rounds of 155 Palmas with RL-15 ( 3 trips to the range ) and shoots an inch or less @ 300 yards and gave it a good cleaning before I used the SST's.

Would humidity have any effect on patterns compared to a sunny day?

I am working on another set of 3 round groups but with a CCI 200 primer ( saving the Fed210M ) this time. Hopefully I see some change from the last patterns.

 

[358 WCF]

I've noticed that it takes some of my rifles a little longer than 2 or 3 fouling shots to start grouping well again after a through cleaning with all these new decoppering, decarboning chemicals. Too much of a good thing? Maybe.

Also 3 shot groups are at the ragged minimum end of all things statistical. They work OK for showing possible trends, but the sampling just isn't big enough for much of anything else with any degree of certainty. 4 or 5 shots shows truer expected group size. 10 shots is an even better sampling if you want to check your 3 shot trend.

Wind, even a small breeze, will affect groups more than humidity. So will lighting differences & mirage. Do you shoot across a hillside that the sun hits? Remember, heat rises & yes those thermals rolling up the hill will move your POI a bit. Then there's always the loose screw behind the trigger that had an extra cup of coffee on the way to the range.

 

[TackDriver284]

358, I had cleaned the rifle prior to shooting those, it took 2-3 rounds to settle, and shot several .3 -.4 MOA 3 round groups and that .2 MOA group. Maybe I did something wrong, possibly used a wrong full sizing die
( RCBS )with the button which pulls on the neck on the upstroke, that I don't like. Today I full sized with a Redding with a bushing today without the button and used a .307 carbide mandrel afterwards and a change of primers to a CCI 200 and I'll make another trip to the range using the same 3 round charges as I did the first time and see what results I may get.

 

[358 WCF]

Mark, knowing nothing about your rifle or anything else I was just throwing out some ideas about stuff that's caught me in the past & continues to screw up my otherwise good groups.

Hoping you found the magic combination, but I'm curious what use the .307 mandrel has when using a bushing die? The bushings are able to adjust neck tension by .001". Unsure about Redding, but Wilson bushings have a slight taper, so if you flip them there's approx. a .0005" difference. Maybe you didn't have the right bushing on hand? Changing primers at the same time? Hmmm... was it the primer change or the sizing procedure that caused the difference?

Trying to get the best from our equipment is fun, frustrating at times, enlightening, & a great hobby. For a deer rifle, a consistent 3/4" is better than trying to reproduce a 1/4" fluke. Chasing teeny tiny groups with a hunting rifle can make us crazy(er) but the equipment makers love it. I need to pack more sand in my front rest bag & get some more spoon melting coffee before going to the range...

Interesting video here by the guy who designed the 1st FL bushing dies. (The S is for Speedy.) Among other things, he explains why it's not all about shooting the smallest groups, but about not shooting any big ones. Smart guy.

https://www.youtube.com/watch?v=1kUywg2OFUk

If you dont know about the Houston Warehouse here's some background & the original article is downloadable.

https://precisionrifleblog.com/2013/10/ ... -accuracy/

 

[Nimrod84]

358 WCF has great responses and I would be okay hunting with anything starting with a 0; but I've never shot game past 350-400.

I've seen humidity / temp changes cause some issues due to bedding changes in wood stocked rifles. On a synthetic or tub gun, I don't think humidity makes much of a difference unless your getting into the trans-sonic range or its raining and you get really unlucky - https://www.gunsandammo.com/editorial/e ... ory/372027.

If neither of those describe your situation - I would be looking at the brass prep / sizing operation and the nut behind the trigger. If you are able, it might be worth checking the scale to make sure it didn't get bumped or start reading low.

I had a similar thing happen for me, but it went the other way. Great groups as I got to 5 shots on brass that I wasn't annealing and bullets were basically falling into the case - I got fantastic groups for me with less neck tension. Had 3 consecutive shots on a 3" plate at 500 yards and the last two went just off the right due to a missed wind call. Groups went back to normal once neck tension was restored.

 

[lhsako]

I've noticed that it takes some of my rifles a little longer than 2 or 3 fouling shots to start grouping well again after a through cleaning with all these new decoppering, decarboning chemicals. Too much of a good thing? Maybe.

Also 3 shot groups are at the ragged minimum end of all things statistical. They work OK for showing possible trends, but the sampling just isn't big enough for much of anything else with any degree of certainty. 4 or 5 shots shows truer expected group size. 10 shots is an even better sampling if you want to check your 3 shot trend.

Wind, even a small breeze, will affect groups more than humidity. So will lighting differences & mirage. Do you shoot across a hillside that the sun hits? Remember, heat rises & yes those thermals rolling up the hill will move your POI a bit. Then there's always the loose screw behind the trigger that had an extra cup of coffee on the way to the range.

Absolutely true! Super clean means more fouling shots needed.

 

[1Shot]

Different day, different weather, different set up of shooting rest, different way you feel that day etc. means different results. With anything under MOA don't sweat it and go hunting. LOL