Trying to reduce SD

[Boisblancboy]

In my .308 using 44.6gr of RL-17, Winchester brass, Winchester primers and 230 gr Bergers I'm getting velocities of about 2450 average. My SD in a 10 shot group is about 15. I tired using BR-2 primers but things got worse. I'm running .003 of neck tension. Any quick ideas what to try to bring my SD down?

 

[fdshuster]

Try different primers, bullet seating depth, and neck tension?

 

[Rem6br]

Try .002 on neck tension

 

[Down South]

If it were me I would try Fed, wolf/tula, and mag primers and see what happens. Different neck tension, seating depth, etc. can affect it also from what i've seen in testing. Do you turn necks? There are so many factors it'll make your head spin.......

 

[Boisblancboy]

One thing I forgot to mention is that the larger the charge the better the ES and SD got. I'm not sure if that has any significance or not but I was definitely happening.

 

[bheadboy]

if the larger charge seems to improve the results, and you are near capactiy for that powder, try a slightly faster powder, i find that the best pressure curve is not always with the slower powders and heavy bullets.

Bob

 

[Boisblancboy]

I am at capacity but not showing any pressure signs.

 

[Steve Blair]

Most cartridges show least velocity variation near or at full pressure. Even if the case is full, that will not guarantee low figures. I use H4350 in .308 with 230 Hybrids and get very low ES. Give it a try. I gave up on RL17 because of temperature problems with hot barrels and attendant velocity variation. [br]
All of the factors cited above, as well as seating depth, seating depth variation, charge weight variation, contribute to velocity variation. While no single factor may be a large contributor, the effects are cumulative. [br]
On another note: Standard Deviation is a statistical tool used to predict the behavior of larger populations from a small sample. Get rid of it as it has no importance to a long range shooter. All that matters is extreme spread. You could have a relatively low SD with one round 30 fps slower than the rest. That shot is likely a low 9 at 1000. Start looking at your extreme spread and try to get it under 15 fps. Your elevation will improve.

 

[PRECISIONWELDING01]

RL 17 is erratic big numbers just unpredictable I gave up on powder .tula primers will help

 

[brian427cobra]

What scale are you using.

 

[bozo699]

RL 17 is erratic big numbers just unpredictable I gave up on powder .tula primers will help

I have top shelf scales and I have to agree with this.
Wayne.

 

[6BRinNZ]

If I was only allowed only one area to reduce my SD numbers I would work on neck tension/thickness consistency.
The next thing I would try is primers...falls into the quick idea category...if you can get them
In reality everything comes into play.

+1 to what sleepygator said.

 

[bozo699]

Wayne,
I agree but also seating depth has a huge part in it!
Wayne.

 

[6BRinNZ]

Wayne,
I agree but also seating depth has a huge part in it!
Wayne.

yep no argument there

I was hoping you might chime in...

 

[Laurie]

I'd agree with earlier comments about Re17 in .308 Win - it only works with heavy loads and the heaviest of bullets and can still produce problems. If you must stick with it, switch to Lapua Palma (small primer) brass and use SR magnum primers. This case design with the small primer, and I suspect even more crucially the small (1.5mm) diameter flash-hole, changes the burning characteristics of heavy charges of relatively slow-burning powders such as Re17 and Viht N550. You can usually work up to noticeably higher velocities too despite Lapua cases having less capacity than Norma or Winchester. It's very strong brass, so a high initial cost is usually recouped in the long run. With annealing every few firings I'd expect them to last for 20 or so firings even with stiff loads under 210-230gn bullets.

 

[Laurie]

I use H4350 in .308 with 230 Hybrids and get very low ES. Give it a try. [Sleepygator]

Interesting ..... I'd wondered about anybody using 4350 on your side of the Atlantic as few if any have tried it on our (eastern) side. Viht N550 is a lot cheaper than H4350 in the UK, and it's the most popular choice for 210s and heavier. As with Re17, it does need to be loaded up to full pressures to perform well, and I'm pretty sure users lose much of their initial saving through reduced barrel life. Just as well we don't string shoot here!

 

[Boisblancboy]

I'm using a RCBS ChargeMaster 1500 Powder Scale and Dispenser that I set to .3 gr short of what load I'm looking for and hand trickle the rest in.

Well I think what you guys are saying is right, my only problem I don't have enough inventory to try new cases primers or powder. I don't have the combination of components I need to give it a shot. So I think I'm kinda stuck with what I have for the time being until components start becoming more readily available again.

 

[Erik Cortina]

I'm using a RCBS ChargeMaster 1500 Powder Scale and Dispenser that I set to .3 gr short of what load I'm looking for and hand trickle the rest in.

I think we just found your problem.

The scale on the Chargemaster is not sensitive enough to allow you to hand trickle slowly.

Try this, set scale to 0, then trickle powder very slow (I used Omega trickler for this test), you can get a few grains of powder in the pan without the scale ever reading higher than 0.

 

[Boisblancboy]

While I agree it's not the best scale I do check what the rcbs is saying to a beam scale.

But while trickling I go very slow. I notice that the scale can take up to a few seconds for the addition two to three grains of powder to register.

 

[bozo699]

I agree with Erik, and my findings were the same as his.
Wayne.