is it a must to work up new load when changing powder lots

[5R milspec]

remember here you are not so much chasing fps when changing lot to lot in powders, keep accuracy in mine. So with that said, you can find the same or as close to the same fps from lot to lot, but watching the accuracy would be the most important thing to do.

[Bart B.]

Everyone I know throws a party when they learn their ammo has a 14 fps velocity spread. That'll produce an SD of about 4 fps.

Congratulations.

And that's the first time anyone on the iNet tested that way then published the results I know of. I hope every reloader reads it.

Timing's important, too. Warm up the barrel with a few shots then load the first round to test, let it cook in the chamber for 15 seconds then shoot it. 45 seconds later, chamber the next one then wait 15 seconds to shoot. Keep this cycle constant for all shots fired. Then all powder charges will be cooked "medium rare" to shoot bullets out the barrel with the same pressure curve shape. That helps uniform their speed.

Sierra 175 HPMK's will stay supersonic through 1000 leaving as fast as yours in temperatures above 60 degF.

[Metal god]

Yep ES was 14.5 and SD was 5.74

I'm still here at the range . On my last work up load of 4064 and 175gr smk
Started at 42.5 gr and about to shoot my last load of 44.5gr . 43.5gr shot real good . 44 seems to have tight bolt . Would not call it sticky .

[jwrowland77]

I don't know if I'd go any higher than 44 if I was getting a tight bolt, especially if 43.5 shot really good.

It's nice to find those loads with low SD and ES. I found a couple of those this past weekend.

[Metal god]

Yep again . 44 and 44.5 are to hot . I think I got some primer pocket leakage on that last 44.5gr load . I'll update the thread later with pics . Cleaning up right now and leaving range in a few

[Metal god]

Here's a quick update and pics of targets and brass

This is the Loads I worked up using 175gr smk and IMR-4064 . The 42.5gr is 1.1 moa , 43.5gr group is .8 moa with that flyer I did not call . The 44.5gr is 1.3 moa and I did call those two low left shots so I think that load is more accurate then what I shot . To bad it's over max pressure .



Here is the primer end of the brass in the order they were shot . They don't look to bad but I think the 44 and 44.5gr loads are to hot .


This is a link to the brass photo that you can zoom way in on and see the primers up close
http://imageshack.com/a/img536/5846/b42080.jpg

This pic is of the test results of the two different lots of IMR-4895 . Old lot 1.3 moa 10 shots / new lot 1.6 moa 10 shots but I was not really going for any real accuracy on those strings



All in all I think I had a good day . The fact it seems my velocity gets more consistent with a much lighter hold means I need to move my scope back a little if I plan to shoot like that from now on . It's a completely different hold so I'm sure there will be more to adjust as I start to hold the rifle in that way . One thing I noticed is my trigger finger placement needed to change just a tad . I was pulling the rifle when pulling the trigger .

Feel free to comment on anything I worked on today . I'd like you guys to take a good look at the brass . If you need other pics let me know and I'll post

[jwrowland77]

That 43.5 of 4064 load looks pretty good there. Nice. Definitely looks better than the 4895 loads.

[Metal god]

I really didn't see any powder soot on the brass and primers but I remembered wiping the head of the case after those 44.5gr loads and a little black soot was left on my thumb . That got me thinking I should check my bolt to see what it looks like


Is that black powdered doughnut around the firing pin hole normal or is that an indication of to much pressure . Does that show that gases leaked through the primer pocket ?

I also updated the accuracy measurements on those targets above

[Real Gun]

All very interesting. I just had to wonder on the last target shown with so many hits trending around 2 o'clock whether the gun was quite sighted in.

[Metal god]

Yes the gun is sighted in but not to the loads I was shooting . When doing load development I have found It's best to aim at the same spot every time and see what's the smallest group . If you chase the bull with each load you will never know how that load works . Case in point . I had the same POA at both pictured targets . How ever my POI was almost the exact opposite . On one high right the other low left . I also had another load with me I was working on with all different components . It shot WAY high right of my POA . so much so I had to aim at the low left side of the target or the bullets would either be off the paper or in one of the other targets .

After I get a load I really like I sight the scope to that load . Then note the scope adjustment needed for all other ammo I shoot through the rifle . That best load is my 178gr A-max , 4064 combo but may soon be the 175gr smk and 43.5gr 4064

[jwrowland77]

The 175gr SMK with the 43.5 shot really well. Should be a good 600yd load, if your looking at doing comps.

[Metal god]

If that 43.5 load ends up being as good as it appears . It will be my go to load for all shooting distances including 1k .

Ave. 2712 fps
ES 34
SD 14

Who knows maybe I get those numbers better by the way I hold the rifle

[jwrowland77]

Oh definitely. Didn't realize you hit 2712. You'll definitely be able to 1k with that for sure.

[Bart B.]

Is that black powdered doughnut around the firing pin hole normal or is that an indication of to much pressure? Does that show that gases leaked through the primer pocket.

Dirty, high residue powders typically put more of that black stuff on bolt faces than cleaner ones. IMR3031's a good example of dirty powder whereas IMR4064's pretty clean.

If that black stuff cleans off easily (bore cleaner and toothbrush; aggressively) and there's no surface texture change or micro-pitting under it compared to the rest of the bolt face, it's just powder soot blowing back around the primer at low pressure before its cup seals against the pocket at peak pressure. A normal thing that sometimes happens; usually with reduced, low pressure loads.

If there's surface texture erosion and/or pitting (gotta use at least a 10X loupe to see it, maybe) under that black stuff, then hot gases are blowing past the primer near peak pressure. A cause could be the primer pocket's been enlarged from previously fired hot loads and too much gets by before the primer cup seals against the primer pocket.

[Metal god]

Here's the clean bolt face . Looks like there may be some pitting . I scraped a dental pick across the face but did not feel anything

[Clark]

CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.

I handload over 5 dozen cartridges.
I have overloaded over 2 dozen cartridges to the point of destruction just to see what would happen.
I have overloaded the 308 and other cartridges with similar case heads; 6mmBR, 243, 257RAI, 260, 270, 30-06, and 8x57.

The 6mmBR is the exception because of the small rifle primer pocket. The weak spot in a work up is a pierced primer.

The 308 and the others will get a loose primer pocket as the limit. I measure the extractor groove growth as a more sensitive and consistent precursor to loose primers.

If I play with Quickload so that the velocity predicted matches the velocity measured, I get a consistant pressure of loose primer pockets across the Mauser case head cartridges.

Measuring that threshold and measuring those velocities allows me to compare different lots of powder.

I have found the difference between IMR4895 lot to lot and H4895 not to be a big deal, and can be down in the noise of the other variables I account for in my derating by a safety margin from the threshold of lose primer pockets.

What is different is bulk 4895 pull down surplus powder.
I have found as much as a 9% difference between that and the fancy canister 4895 powder from the gun store.

[pathdoc]

Quite a few published loads have a four grain spread between minimum and maximum listed, so max = min + 4.

If my load was min + 2 or less, I would feel safe to run with it.

If my load were above this, I would shoot min, min + 1, min + 2, then advance in half grain increments.

Obviously this needs to be adjusted in proportion depending on the spread of your particular cartridge/powder/primer/projectile combination, published data and any previously determined maximum for your rifle.

[Bart B.]

The second test's results in post 25 is one reason I think ladder and OCW tests are just a roll of the velocity dice when the rifle is hand held. Each dot is worth about 7 or 8 fps of velocity spread for the .308 Win. Figure the odds of each throw from snake eyes to boxcars.

[Metal god]

I am amazed at that test in post #25 my self . Those ten rounds , 5 in each test were loaded at the same time in the same way . I did all the case prep and sizing ( neck only )at the same time ( 50 cases ). The next day I loaded 50 rounds all with the old powder lot , bullets from the same 500ct bag . primers from the same tray etc etc . I do not throw my charges . I weigh the charges to less then a tenth (I throw to get close then I trickle till I get closer then add one kernal at a time till my beam scale is zero ) and check weight every 20 rounds or so while loading . Cases are trimmed to the exact same size then the flash holes are reamed . All placed in the same box and pulled randomly . Those should be very consistent loads and I think the first test shows that .

I will do more test like that . It sucked those were my last 10 rounds I had with me that were known to be good . I would say that 2517 first shot seemed to be odd . As soon as I saw it I thought that can't be right . I will try to duplicate that test next time out .

I will say barely holding the rifle is an odd way to shoot . I was concerned of scope bite . My big muzzle break probably helped with that . Also the fact I had very little pressure on the rifle . My 2.5lb trigger pull moved the rifle much more then I thought it would . I had to adjust were the pad of my finger was placed on the trigger in order to keep the cross hires from moving . I'm not sure if that means I've always had bad trigger finger placement or it was because my trigger finger hand was completely off the rifle and I had to pull the trigger while holding my hand and arm in the air .

[Bart B.]

Metal god says:

I do not throw my charges . I weigh the charges to less then a tenth (I throw to get close then I trickle till I get closer then add one kernal at a time till my beam scale is zero ) and check weight every 20 rounds or so while loading . Cases are trimmed to the exact same size then the flash holes are reamed . All placed in the same box and pulled randomly .

Then surmizes all of that to mean:

Those should be very consistent loads.

Well, your target's show something's not very consistant.

Sierra Bullets throws charges from a measure with a 3/10ths grain spread into totally unprepped cases testing their bullets at 200 yards with 10-shot groups. Their best 30 caliber match bullets shoot 1/4 MOA or better groups. As far as I've found out, Berger does the same with theirs. Rail guns are used to test this ammo so all human variables as well as those of rifles are eliminated. Realistically, its a test of the ammo as well as the barrel used, but you cannot shoot one without the other. The barrel has the least variables in the system. And the variables in the case, powder and primer are insignificant.

Benchrest competitors producing the smallest groups through 300 yards meter their powder charges to a 2/10ths grain spread directly into totally sorted and prepped cases. Their groups are only a tiny bit smaller than Sierra's or Berger's.

If your more exact and identical load components don't do that good, I suggest your look in other areas of variables that degrade accuracy a lot more to shrink your groups by reducing them. So learn and check out what other variables there are in those three areas; rifle, ammo and you.

[Metal god]

Well, your target's show something's not very consistant.

How dare you sir !!

Oh yes it's me for sure . I believe I proved that in the test . When I was barely involved in the shots . They shot very consistent . The more involved I became the worse they did poor me That's one of the reasons I load the way I do . I want to make sure it's not the ammo . That way I can work on me . I believe my biggest issue is trigger flinch and I still can't get the reticle to stop moving . It moves around about 1/4 moa and I can't seem to stop it . Maybe with less hold on the rifle I'll do better . That is something I will be looking into in the future .

I'm still pretty new at this . only been a couple years since I started shooting for accuracy . I had been shooting for many year before that but just plinking and spraying and praying Many bad habits I need to work through .

[Bart B.]

I suggest you test your ammo slung up is a solid prone position with a tightly rolled up towel under your front hand that holds the fore end and another smaller one under the stock's toe. Then grip the stock's grip with your other hand so the fore finger end pad is on the finger lever and no other part if that finger touches the stock. You may need to twist that hand's position to do that. You need to hold on target while totally relaxed. No muscles strained pulling the rifle to opine where you want it to.

Adjust your position moving your front elbow sideways until your aiming error wobbles the least. Positioning the butt up and down in your shoulder to see where that helps. Then change your body angle and leg position to further shrink your holding area.

Dry fire and watch which way the reticule jumps when the firing pin falls. If it jumps to the right, your trigger finger's too much into the trigger guard onto the lever. If jump's to the left, the finger's not in far enough. You need the force on the trigger to be straight back so when it's come to a stop, that force pushes the rifle straight back and no amount sideways.

Most people shoot .308's more accurate this way than holding onto them resting on something atop a bench they're sitting at. Some have been doing it since the 1950's. It finally evolved into what's now called F Class competition.

[Metal god]

Thanks Bart for the help . I'll work on that next time out . Not sure when that will be though . Just picked up a couple more jobs and it could be as much as 4 weeks before I get out again