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Standard Deviations on .308 of 160!!!!!

m1a convert

Sergeant
Full Member
Minuteman
Mar 29, 2003
287
4
Idaho Falls
I just got a chrono and my loads suck for consistency. SD of 160 and extreme spread of 507!!

I am working on getting the load more consistent.

Remington cases. Varget. 175 gr. SMK. Fed 210M

I size the cases and then throw the charge with a RCBS chargemaster scale, then seat the bullet.

I know I could go crazy and measure every aspect of the case for concentricity etc, but I am looking for the things that will give me the most bang for my buck as far as time spent.

I have a friend on the US Palma team and he says weigh the cases and sort them into groups is the biggest thing. He doesn't uniform the flash hole, trim to length, turn necks etc. His SD are around 7.

What do I need to do to fix this?
 
Re: Standard Deviations on .308 of 160!!!!!

Try isolating your scale from any possible electrical interferences and plug it into a battery backup to keep it from bouncing with electrical variances. Get a good set off check weights also. Leave the scale on also to keep it warmed up or at least turn it on one hour before using it. I also keep the first case that I have loaded as a weight check. I tare my scale to that case and look at the weight variances. If I see anything over 1-1.5 grains it gets pulled and checked.

I know before I plugged my Denver Instrument into a battery backup I could watch the scale jump when the AC unit kicked on and off.

A good certified check weight is always a way to make sure your scale is reading what it should be. I got several check weights and always try to toss the check weights that are close to the load I want.

I noticed with my Lyman 1200DPS that I could punch in 43gr and I could take the pan off the scale and when I placed it back on the scale it would be off by 2-3 grains. Needless to say that got sent back.

Always have two scale IMO a digital (I like Denver Instrument) and a good balance beam. The old technology still works too.

Terry
 
Re: Standard Deviations on .308 of 160!!!!!

my lyman does the same did they fix it when you sent it back
 
Re: Standard Deviations on .308 of 160!!!!!

+1 to the above recommendations.

I don't turn necks, weigh brass etc. I have several loads for my .308 that get me 3.8, 4.2, 7.1 and 8.9 SD's consistently with my chargemaster.

By consistently I'm referring to at least 100 rds of each chronied on different days, different weather conditions and it's still within those particular ranges (~1.5 +/-) for the same components.
 
Re: Standard Deviations on .308 of 160!!!!!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mavrick10_2000</div><div class="ubbcode-body">+1 to the above recommendations.

I don't turn necks, weigh brass etc. I have several loads for my .308 that get me 3.8, 4.2, 7.1 and 8.9 SD's consistently with my chargemaster.

By consistently I'm referring to at least 100 rds of each chronied on different days, different weather conditions and it's still within those particular ranges (~1.5 +/-) for the same components. </div></div>

So what do you feel is important to do to achieve those low SDs?
 
Re: Standard Deviations on .308 of 160!!!!!

With numbers like that, I'd say your chronograph is malfunctioning. An ES of 500+ is damn near impossible unless you reload blindfolded or something kinky like that.

Try the loads again on another day, see if they still read wonky. Bring a box of known-good factory ammo like FGMM 168s or 175s or perhaps some standard-velocity *match* .22LR ammo - they may not have the super tight ES/SD you're looking for, but generally pretty decent nonetheless. If the numbers are all screwed up still... it ain't the ammo.

 
Re: Standard Deviations on .308 of 160!!!!!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: memilanuk</div><div class="ubbcode-body">With numbers like that, I'd say your chronograph is malfunctioning. An ES of 500+ is damn near impossible unless you reload blindfolded or something kinky like that.

Try the loads again on another day, see if they still read wonky. Bring a box of known-good factory ammo like FGMM 168s or 175s or perhaps some standard-velocity *match* .22LR ammo - they may not have the super tight ES/SD you're looking for, but generally pretty decent nonetheless. If the numbers are all screwed up still... it ain't the ammo.

</div></div>

Bingo!
 
Re: Standard Deviations on .308 of 160!!!!!

What was the vertical spread like with those rounds, even at 100 yards you should see a sizeable vertical spread unless the chrony is bad. My first thought when I read your post was that your chrony is bad.

 
Re: Standard Deviations on .308 of 160!!!!!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: memilanuk</div><div class="ubbcode-body">With numbers like that, I'd say your chronograph is malfunctioning. An ES of 500+ is damn near impossible unless you reload blindfolded or something kinky like that.

Try the loads again on another day, see if they still read wonky. Bring a box of known-good factory ammo like FGMM 168s or 175s or perhaps some standard-velocity *match* .22LR ammo - they may not have the super tight ES/SD you're looking for, but generally pretty decent nonetheless. If the numbers are all screwed up still... it ain't the ammo.

</div></div>
+1 there is no way in hell those numbers are right. i don't do half the shit some reloaders do and don't have near as nice as equipment as some and still get sd of 7-10 consistently.
 
Re: Standard Deviations on .308 of 160!!!!!

Make sure your rifle is consistently lined up in the same place for every shot fired as well . I have a Beta Master chronograph and rarely see great SD's over a long string . I use it to figure out averages to get me on at different ranges and then correct my Dope with real world data .
 
Re: Standard Deviations on .308 of 160!!!!!

First of all, such spreads indicate a problem with the chrono or the chrono process. My guess, it's the latter. Readings taken within 20ft of the muzzle can be faked out by the muzzle blast.

Greg
 
Re: Standard Deviations on .308 of 160!!!!!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">First of all, such spreads indicate a problem with the chrono or the chrono process. My guess, it's the latter. Readings taken within 20ft of the muzzle can be faked out by the muzzle blast.

Greg </div></div>

I don't have any proof except my word but I chrono at 15 feet from the muzzle and have had no problems. I agree it is a chrono issue and a guess would be its a Chrony. That being said I have seen readings change with cloud cover going in and out but no where near that much. Read the paper and leave the chrono at home unless your curious on speed.
 
Re: Standard Deviations on .308 of 160!!!!!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: eitmsmf</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">First of all, such spreads indicate a problem with the chrono or the chrono process. My guess, it's the latter. Readings taken within 20ft of the muzzle can be faked out by the muzzle blast.

Greg </div></div>

I don't have any proof except my word but I chrono at 15 feet from the muzzle and have had no problems. I agree it is a chrono issue and a guess would be its a Chrony. That being said I have seen readings change with cloud cover going in and out but no where near that much. Read the paper and leave the chrono at home unless your curious on speed. </div></div>

It is a Chrony. Are do they have a reputation of being garbage?
 
Re: Standard Deviations on .308 of 160!!!!!

My shooting partner and I both own Chrony's and between us we don't have a working Chrony. His stopped a gas check, and mine got caught in a passing sun shower. Not really the crony's fault in either instance. Fact is, neither of us have clocked a round in a couple of years now, and we seem to be doing pretty well without them.

Greg
 
Re: Standard Deviations on .308 of 160!!!!!

Same problem with my Chrony Betamaster...eventually sold it
A recent used oehler 35 P sold on ebay for 568$ with 6 sky screen lateral supports missing !!!
 
Re: Standard Deviations on .308 of 160!!!!!

I use a chrony and don't have any probs even as close as 10'.
 
Re: Standard Deviations on .308 of 160!!!!!

Truth be told, the only REAL point in the chrono is to wip out a make-shift ballistics table with your bullet and velocity,some claim to use it as a way of making sure they aren't over pressure, but I've had "Above max loads" in a manual not cycle in my 1911, ive seen my .308 shoot 100fps faster than a max load with 1.1 grains less powder ect....Check for pressure signs on the case ect.. But in the end, if you serious you are going to shoot at 100, 200, 300, ect...all the way out to find out what it really does, which makes the point of the chrono moot. Someone above mentioned ignor the chrono and see what the bullet actually does, do that. Also, read the directions and change the battery :)Then you can move from that to ignoring groups and seeing what you can actually hit
smile.gif
 
Re: Standard Deviations on .308 of 160!!!!!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: tarzan</div><div class="ubbcode-body">my lyman does the same did they fix it when you sent it back </div></div>
No, it still did it! It got sold on Ebay! I use a Denver Instrument now!

Another trick to help you when you are chronographing loads!

Simply take a Black Sharpie marker and blacken the bullet tips! That easy.
This will give you better variation between the bullet and your white chrono tops.

I also have a piece of string that is the length that I want my screens away from my muzzle attached to my tripod! That way I get my screens the same distance from my muzzle every time.

Another good trick for those of you that do not have IR screens for chronographning on cloudy days. Chemical Lights taped to the tops of your screens! Bright yellow works really well!

Terry
 
Re: Standard Deviations on .308 of 160!!!!!

I'll just second or fifth the motion that an ES of 500 would have to be the chrono. If it isn't maybe you need to stop reloading for a while.
 
Re: Standard Deviations on .308 of 160!!!!!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: PGS</div><div class="ubbcode-body">Sounds to me like the chrono is a POS. </div></div>


+1
 
Re: Standard Deviations on .308 of 160!!!!!

Spend $200 and get a CED M2 chrono and then you wont be waisting your time.

CJG
 
Re: Standard Deviations on .308 of 160!!!!!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: m1a convert</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mavrick10_2000</div><div class="ubbcode-body">+1 to the above recommendations.

I don't turn necks, weigh brass etc. I have several loads for my .308 that get me 3.8, 4.2, 7.1 and 8.9 SD's consistently with my chargemaster.

By consistently I'm referring to at least 100 rds of each chronied on different days, different weather conditions and it's still within those particular ranges (~1.5 +/-) for the same components. </div></div>

So what do you feel is important to do to achieve those low SDs? </div></div>

I time my shots for each string and between each string. Depends on the temp outside. Generally 3-5 mins between shots 15-20 mins between strings - basically I'm not letting the barrel heat up too much, and keep the temp as consistent between shots as possible. Eject the fired brass and keep the bolt open while I wait to allow air flow to cool it a little bit as well. Shooting on a covered line doesn't hurt either to provide a little shade. I'm always consistent when testing new loads. I have a CED M2 and it's great. I've heard the Wolf primers give more consistent SD's as well. I haven't tested any other loads for any other rifles (Diff Primers) with my chrony yet, so I'm not about to contribute it soley to the Wolf Primers. Not all of the loads while working up had SD's that good, but nothing over 34-35 and those were two consecutive charge increments, and then started going back down, eventually to 7.2 as my charge weight increased on the high node for my rifle with that load, I listed the best to date in my prev post.