Hello fellow members. I have just recently started learning and reloading for my 308 bolt gun. Some background info before the questions. I am using Hornady Match 168gr bullets with 43.6 gr Varget powder and CCI primers. I am measuring powder with a RCBS 1000 beam scale and trickling with an Omega trickler. I have been measuring my speeds with a Magnetospeed V3 and documenting target results with pictures. I am resizing my Hornady brass with .001" neck tension and only moving the shoulder back a few thousands. I also trim and chamfer each case back to 2.005". I am currently focused on group size and accuracy as I work on my shooting mechanics. I then plan on stretching the set-up's legs and learning to shoot at longer distances.

I have read that there are a few items that can cause speed variations. I believe they are volume size in the brass, measured powder accuracy, primers, and neck tension. Now the questions:

1. Which ones are the most important?
2. My last test group showed a 40ft/sec variation. Is this about average for my set up or can I do better?
3. Do I need to weigh my brass to possibly get more consistent internal volumes?
4. Do I need to invest in a better scale (i.e. A&D FX-120I, etc.) to get lower speed variations?
5. Is the speed variation mostly coming from my Varget powder choice?

I appreciate any guidance from the group.

You gave no rifle, load, MV, or target data so I presume you feel you should have a better ES than you experienced. Given your prep and reasonable brass from the same lot, so would I. I'd expect to get an ES under 20fps. So, why 40fps?

Could be the brass. Use only brass from the same lot prepped the same way to the same length (just in case you didn't before). I have not found weighing cases to be substitutable for calculating mixed headstamp/lot case volume. But given the same lot of brass in your case I would weigh it (perhaps after a good washing) and select only the closest matches for the next test. If you have the same lot and the weights vary significantly, you might consider using a different manufacturer's brass. Lapua, Winchester, Lake City (same headstamp) seem to be the most frequently recommended.

Could be varying charge weights. On the next test with matched brass, be extra finicky about the weight shown on your (clean) beam scale. After a trickle, tap the pan to force the scale to "re-weigh" the whole pan . . . not just react to the last trickle.

Could be your target charge isn't very good, but this is more likely to give precision issues than twice the ES you would expect.

Hornady Match aren't the "best" bullets out there, but they certainly represent enough quality that they should not be a major factor here.

Are the barrel, crown, and the rest of your rifle in reasonably good shape?

Your MagnetoSpeed is quite likely to change the POI, change it differently if you make even small adjustments to its location or tightness of the strap . . . but it's not likely a contributor to your ES.

You asked which factors are most important (presumably to ES). Assuming a good rifle, a bullet, powder, and charge that your rifle likes, I'd say . . . lot-matched quality brass . . . accurate powder charge weight . . . consistent seating based on base to ogive measurements . . . reasonably consistent neck tension. Presumably the closer those things are one to the next the more likely your MVs will be too.

ETA: Many many other folks swear by Varget, so that was the first powder I tried. I had absolutely no luck with it. Went to IMR4064 out of my 308 and my problems disappeared. Sometimes, for whatever reason, changing powder (and/or bullets, brass) can help your rifle and you.

Rem 700 AAC-SD in AI chassis, 43.6gr Varget, averaged 2578ft/sec, 2.194" CBTO, can do .5"-.75" groups on factory Horandy Match ammo, shows signs of smaller groups with handloads if I could be more consistent/better with my mechanics.

Unfortunately it is mixed lots of once fired (my rifle only) Hornady Match ammo brass. All prepped the same way though.

I think you are correct on the varying charge weight. Seems to be very sensitive to operator reading. I try to double check level zero after each 10 rounds. I do like your idea of tapping the pan to make it reweigh the charge. This is why I asked about maybe a more accurate digital scale to help remove the human error.

Rifle only has about 1000 rounds through it. Crown was just recut to 11 degrees by smith and all hardware torque settings verified by smith.

Funny you mention 4064 as I was going to pick up a pound on Wednesday to try. I have also been told 4895 and Reloder 15 might be worth trying.

Thank you for comments.

Not trying to be a dick, but nearly every Remington has a shitty barrel. I don't do any of the stuff you are talking about. I have in the past but I fl resize, use lapua brass, don't hardly do any brass prep, use a chargemaster, and get consistent bughole sub .5 moa groups with the right powder / bullet combo.

I can't tell you how many years I struggled with precision reloading for guns that didn't really have that much potential. I've got one right now. A rainier ultramatch barrel that doesn't shoot as well as a psa barrel I have. I've tried 5 or 6 different powder / bullet combos and none shoot that well.

While you can certainly can make a difference with details, none of them compare to starting with a good tube.

40 fps extreme spreads aren't bad, how does it group on target? You can shoot very well to 600 yards if you're ES is 40 or lower.

I would try more neck tension. .001" isn't enough to insure consistent ignition unless the bullets are already touching the lands. I would also try lighter powder charges. 2600 fps is approaching maximum velocity for a 24" barrel. You're only .2 tenths of a grain from teaching that speed if you're going 2580 now.

Most commercial match 168 grain .308 ammo runs @ 2600 fps when fired in a 24" barrel. Many long range shooters are using .003" to .004" of neck tension which used to be unheard of. Increase your neck tension by spin polishing the expander ball in a power drill.

Replacement expander balls are cheap and easy to modify.

borderpatrol;

2 questions >>> 1) What grit paper do you use?  and  2) When you are done "polishing", what is the diameter of your expander?

Thanx!

- R -

robpiat you are not being one. I have read many members on here having that type of experience with the Rem 700. The stars must have aligned, a new cutter used on the barrel, been assembled after the first morning coffee break, because accuracy doesn't seem to be the issue. The picture below is a 10 shot group of factory Hornady Match ammo at 100 yards.



borderpatrol when I tried neck tensions of .002 and .003 (using a Lee collet die) the groups did open up. I have been measuring (CBTO, neck tension, shoulder, etc.) the factory match ammo I have on hand as a guide since this rifle seems to really like it. The Hornady box says it will do 2700fps out of a 24" barrel. I have tried loads with more and less grains. Both seemed to start getting bigger as speed went below 2570 and higher than 2590.

I am GUESSING that my human error of reading the beam scale is the largest factor to the 40fps ES I a saw. Then followed by case volume being important. But if the group feels that 40fps ES is not bad, I will "live" with it for now as I improve and become more consistent in my mechanics.

I do appreciate everyone's input as I am still learning.

First thing, try a different primer without changing ANYTHING ELSE. One change at a time.

Going .001" neck tension I would shitcan the Hornady brass. The neck wall thickness of the stuff I measure is not consistent case to case. This makes for different tensions.

You know what, just eliminate the brass variable all together and just get Lapua, then you'll know the brass inconsistency is not the problem.......but first the primer change.Get a few different ones.


What is the condition of the bore, just cleaned, 100rnds, 800rnd since cleaning? 

How many rounds are shot to get the 40fps ES, 5, 10, 100? What is your SD?

What is the oal? (Real, bto is a worthless number to us)

I am pretty satisfied with 7-8 SD and a 25fps ES for long range.

popnfresh thanks for the input. I see many people rave about the Federal primers but I cant seem to find any. CCI seemed to be second. Any others you recommend?

The bore is usually just cleaned or less than 100 since cleaned.

The group size was 15 rounds with 40fps ES and 13.3 SD. I just worked up a larger (50) sample size group to see how that goes.

I thought bto was a more consistent dimension than oal. I thought that the bullets had too much tip variance to use oal as a consistent measurement. Versus the bullet tapper was a more reliable measuring point.

As for your more consistent speed numbers, aren't you using a more elaborate powder dispensing/measuring set up?

Originally Posted By SumDude:
popnfresh thanks for the input. I see many people rave about the Federal primers but I cant seem to find any. CCI seemed to be second. Any others you recommend? 

Just anything,  if they have 4 different large rifle primers, then grab the 4 to try. What are they $3-4/100? I use Wolf for everything but you can't get those.

The bore is usually just cleaned or less than 100 since cleaned.

I like to have 50- 100rounds of fouling before load development. But I only clean at around 900rnds. If your bore is usually clean then development when it's  cleaner is a good idea.

The group size was 15 rounds with 40fps ES and 13.3 SD. I just worked up a larger sample size group to see how that goes.
 
That is a decent number of rounds fired to get an idea of ES and SD. The SD seems to match the ES so it isn't like you just had one bad shot causing a big spread.

I thought bto was a more consistent dimension than oal. I thought that the bullets had too much tip variance to use oal as a consistent measurement. Versus the bullet tapper was a more reliable measuring point.

No, you are 100% correct bto is the proper way to measure your length. But for us, it doesn't tell much, I don't know what your oal actually is. Are you 2.800" long, 2.850", 2.775"? Comparitors are different, bullets are different etc.


As for your more consistent speed numbers, aren't you using a more elaborate powder dispensing/measuring set up?

I use ball powder it throws better. I have this cheap Gemini-20 digital scale that I have checked and rechecked, with calibration weights and against my balance 100s of times now. I have come to trust it for all of my precision rounds.

So I take my case set it on the scale "tare" it, throw powder into the case and weigh it. No trickling ever. If the charge is outside of my limit I dump it and throw again.

I use W748 for everything .223, 6.5G and .308, it flows well enough that I don't really have to even weigh everything. For my single feed 230gr .308 load l use w760 for better velocity, it doesn't work as well but still well enough ti use the same method.


Poor video but you get the idea.



http://www.ar15.com/forums/t_16_10/6511_LABRADAR-vs-MAGENTOSPEED-vs-SHOOTING-CHRONY-BETA-velocity-comparison.html
The numbers for this test above were with my "crap" winchester LR primer that I use for testing so I don't  waste my Wolf primers.

I was surprised by the numbers, the charges were not weighed like in the video just threw them in the case. 
The charge weight was for my 175smk load, these were 168CCs. .001" neck tension.
(850rnds since cleaned)

Then the 6.5G numbers were the actual long range load where every charge was weighed, the Wolf primer, correct charge weight and gave basically the same results as the .308 load that was thrown together.
(650rnds since cleaned for the Grendel)
.001" neck tension.
Lapua Brass for both.

600 grit will polish well and isn't so aggressive that you'll remove too much metal too quickly. I follow up with 1500 grit. Use your calipers and only remove .001" at a time.

If you have three buttons to work with polish one down to .305" .306" and .307".

Thanx!  I only have one expander at this point and unmodified it measures .3065.  If it expands to its diameter but then you get a .001 "spring back", that puts the neck ID at .3055 which would put the neck tension at 2.5 mils.  Almost perfect out of the box!...  I'll have to get more buttons to play with...    Thanx again!

Results from a test Bryan Litz did on neck tension and SD.
Attached File

Neck tension is more a function of the platform being used

Let's just cut to the chase

Get some lapua brass, regular not palma.

Get some BR-2 Large Rifle Primers to use with your Varget

Rework your load at magazine length....

Do not Crimp

Ditch the Lee Die and a Get Redding Type S FL and 0.336 bushing

I best you have an ES of 10 or less!

Thanks all for commenting. Lots of good information here I need to "digest" and look into. I may need to purchase a small sample of better brass to run some comparisons.

To clear one thing up I only used a Lee collet die to vary my neck tension after using my normal full size die. I normal use a Forster full sizing die for neck tension and to slightly move the shoulder back. I then use a Forster micrometer seater die.

One thing at a time!
One thing at a time!

Yup!

BTW, if you don't want to spend $80 for 100pcs of Lapua, Brownells has 25 case boxes of Norma for about $23.
The batch I got was every bit as consistent as Lapua.

Oh cool! Thanks for the heads up.

A shooter I see from time to time claims .001 tension can allow some caliber of bullets to shift in the magazine during recoil. Is that range bullshit, or is there some truth to it?

I plan on using Lapua brass if and when it becomes available. For now, I am using Hornady with good results with my creedmoor. The 308 has been somewhat challenging.

.001" neck tension will not hold a bullet firmly enough for a semi-auto. You need more than .002" to make that happen, .003" to insure it. Bolt actions that aren't run violently when manipulating the bolt can probably get away with .001" of neck tension. That's provided that you have that much. Cutting your neck tension dimension to only .001" is hard to do across a large volume of brass, impossible to do with mixed head stamps.

.0015 to .002" is plenty for any bolt action.

Creedmoor sports sells ammo for 1-1.25 a round loaded in lapua. Periodically free shipping.

Yeah, it's a good idea to be sure. You just have to see how it works. I push a loaded round against my bench to see how much pressure it takes to push in. Then I feed them through a mag and measure.(with already scrutinized Lapua brass)

My Grendel AR gets .001" on mag feed loads with Lapua, Hornady brass needs .003" due to wall thickness variations, some end up .001" some .003".

.223 AR is .001" single feed only rounds, Lapua brass. Plinker rounds, LC brass get the regular dies so probably. 004"

.308 bolt gets .001" for mag and single feed with Lapua. 


As with everything in loading, you need to know what's what and all the details of everything, pay attention to everything .
When I seat bullets, every single one is checked, if I didn't feel a loose neck in seating it will show up short when I  measure it. 

You also have to be aware that neck length that grips the bullet matters. .001" neck tension on a partial sized neck is going to have less grip than a full neck size at .001" tension. 

Good info.
I have to single load anything much over 2.8 in my 308 anyway. The rounds get stuck in the magazine about half the time if not. I have not tested for an exact spec on that yet. I had some of the Hornady 178 ELD's get stuck when I loaded with the "base to ogive" length I came up with using the comparator.  
I will get a chance to turn some case necks this weekend as well, what with the rain that is expected. I bought a neck turner and the goodies to go with it, and it needs to be used.

How much does Humidity when loading change or vary the speed? Do you all only load when the level is low (say 40-50% only)?

I also did pick up a pound of 4064 and a few BR2 primers to try also.

Humidity has very little effect within reason. Humidity can make your powder clump in your measure. Powder may absorb some moisture from the air but with proper handling that can be avoided.

When not in use, containers are closed tight and stored in the house.

When not loading all powder goes back into its container from the measure.

The two things above should keep the powder at a reasonably consistent moisture level.

So one of those things to be aware of but not as important as the other factors mentioned in the posts above.