Mastering velocity ES 284W

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Audax
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Joined: Wed Sep 27, 2017 8:48 am

Mastering velocity ES 284W

#1 Postby Audax » Tue Oct 17, 2017 11:05 am

What is the secret. I have come to the conclusion the spread in velocity is more associated to barrel fouling than brass prep and reloading practices. The reasoning is the cold clean barrel velocities are always relatively stable and the second shot invariably has a 40fps higher velocity. Any subsequent shot never has a velocity as low as the first one...ever.

The calibre is standard 284W with a 0.314" neck running 0.003" or 0.004" clearances on both Norma and Lapua brass. The chamber has a freebore honed to the bullet size of 0.2839". It will not chamber a Lapua 180gr measuring 0.2842". Maybe that is too tight....?

Fired brass is re-sized with a custom die reducing the diameter at the shoulder/body junction 0.001", and headspace is zero ie there is no bolt resistance, but no backlash in the Barnard bolt either. The primer pockets are unformed to 0.128" in depth, and in the past the primers were weighted, and batched by length ie to determine seating depth. That has made no difference so I don't do it now. I have a proprietary tool however to seat the primers at equal depth from the base of the brass....or nominal crush of 0.001" on the anvil legs.

Powder used was AR2213sc, and now AR2209 (Batch # MEM5384), SMK 183gr projectiles now coated with WS-2 (both and and dry method) to try and mitigate the ES, primers tried have been Fed Std, 210M, and BR-2. Powder weight is measured on a Satorious Entris scale ranging from 51.8 - 52.2gr.

With a velocity limit of 2857fps on the range the 52.2 was too hot, but equally as variable in ES as the lighter load. The problem is the SMK's need to do over 2800 in the 1:9" Krieger to stablise so ideally the velocity needs to be ~2840fps.....a couple of blips above that and it could very easily exceed the limit.

Hopefully we can all learn something from this post...?

Audax
Posts: 16
Joined: Wed Sep 27, 2017 8:48 am

Re: Mastering velocity ES 284W

#2 Postby Audax » Tue Oct 17, 2017 11:07 am

That coating should read (both wet and dry method) ....sorry

Rebel105
Posts: 504
Joined: Fri Jun 13, 2008 12:22 am

Re: Mastering velocity ES 284W

#3 Postby Rebel105 » Tue Oct 17, 2017 11:34 am

I'll go first,
The first 2 or 3 shots through a clean barrel will always be slower so delete them from your Chony speeds. What chronograph are you using? How many rounds through the barrel?
Next, 1-9T barrel is likely on the edge of stability with 183 Sierras, I use them. so I wouldn't bother with a 9T barrel 183gn mix. Use Berger VLD 180's then you will start to see results. If you have lots of 2209 use it with the Berger VLD's. I found a great node around 50gns of powder. you should start lower and work up in .2gn increments. There is a higher node if you want to push your brass. in saying this, your circumstances are going to be different as you have coated the projectiles.
If you use 2213sc there is a great node at 2840 with 183 sierras, but, bare not coated projectiles and with a 8T barrel so your call as to which way you go.
Rod Davies might chime in here as Rod uses 183's as well. my secret is out, your turn Rod.
Geoff

Audax
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Re: Mastering velocity ES 284W

#4 Postby Audax » Tue Oct 17, 2017 1:33 pm

Thanks Geoff..I will keep your secret.....I use both Labradar tested against a Magneto speed....both seem to be very accurate with a max tolerance of 5fps between them. I am beginning to think the freebore is fouling too easily because Bergers which measure 0.2842" will not chamber either. I have heard anecdotally that 284W like 3 to 4 thou neck clearance to improve ES but I have seen nothing out there regarding the ideal freebore clearance.....!

The barrel has done 230 rounds, and I went with the 1:9" because 1:8" was struggling to get the velocity needed without pressure signs. I have tried three 1:8" twist buttoned barrels in the 284W configuration eg AR2213sc 56.5gr with bare SMK struggled to get over 2800fps in the 1:8" twist, which is too low to stabilise the 183gr....or those stability issues may have been related to the barrel being buttoned. However neither Lapua Scenar, or Berger 180grs would leave at much over 2800fps in that configuration either...to push harder was asking for pressure problems. The SAUM chambering deals to the velocity issues in the 1:8" twist barrel and I will use that calibre at ranges without the 2857fps limit.....my experience with 1:8" twist buttoned barrels has put me off trying to get the 284w chambering to work with 1:8", my guess is that your 1:8" twist is a cut barrel and that may very well be the difference in performance......?

Let me understand your comment Geoff regarding Berger VLD.....are you saying the accuracy node is something to do with the clean and complete burn of the powder producing as a by-product accuracy on the target, and consistent ES in velocity.....I will try anything....?

Rebel105
Posts: 504
Joined: Fri Jun 13, 2008 12:22 am

Re: Mastering velocity ES 284W

#5 Postby Rebel105 » Tue Oct 17, 2017 2:40 pm

Audax,
2209 is considered a very good powder to achieve low SD. SD is what you should be looking for. What I am saying is a lot of .284W shooters use Berger VLD either jammed a little or jumped a little and very easy to tune with 2209. Mine likes .015" jump and it's a buttoned barrel. I can use either 2213sc with 183Sierras or 2209 with Bergers. I'm not home but from memory my 284 reamer has about 230 thou freebore which seats the projectile down to the shoulder/neck junction just.
I suggest you may have answered your own question with the tight chamber/neck/ free-bore. .284 do like at least 4thou neck clearance. If you have the 8T barrel still, try it with a different reamer, (not too custom neck etc) If the Bergers are not chambering you may have an issue there which is causing a lot of pressure by clamping the projectile, so take care. I would recommend not using it until you have that area investigated.
My saum shoots the 183's quite well and it's a buttoned 8.5T barrel.
I would not want to comment further on which barrel is best but I say cut or button will/should not cause your issues. I have used both and can't pick much difference.
The barrel is now ready to tune so it should be easy now.
A bit of info for you to decipher. try projectiles uncoated then when the barrel is humming check with your Labradar, then match the speed with coated ones to see if it achieves the same.
Geoff

Gyro
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Location: New Zealand

Re: Mastering velocity ES 284W

#6 Postby Gyro » Tue Oct 17, 2017 3:25 pm

Nice work Audax but why have you decided to play with the 'standard' freebore clearances ? Perhaps this is introducing variables that will add confusion to your adventure ?

Audax
Posts: 16
Joined: Wed Sep 27, 2017 8:48 am

Re: Mastering velocity ES 284W

#7 Postby Audax » Tue Oct 17, 2017 3:46 pm

Hi Gyro,
That is what I am trying to ascertain......what is standard.....? And why.....?

The reamer manufacturers ask you what dimensions you want...and yes my adventure is certainly a bit confused, in fact I am wondering which way is up...?

Matt P
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Joined: Mon Nov 14, 2005 8:22 pm

Re: Mastering velocity ES 284W

#8 Postby Matt P » Tue Oct 17, 2017 4:02 pm

A few questions, how do know that the 8 twist doesn't stabilize the 183 SMK, going the Berger twist rate calculator it has a Stability factor of 1.5 or higher right down to 2500 FPS in an 8 twist ?? If the stability factor is over 1.5 it's stable and will give optimum BC.
The 0.2839 FB dia isn't enough in my opinion, I have actually increased the FB dia on most of my new reamers to 0.0008 over nominal (6mm based calibers 0.2438 for example).
As Geoff stated around 50 grns of 2009 and a Berger 180 grain bullets would be the standard load in FO.
The bullet doesn't know if the barrel is cut or button, have you checked if the button barrel is an 8 twist ??
Matt P

Audax
Posts: 16
Joined: Wed Sep 27, 2017 8:48 am

Re: Mastering velocity ES 284W

#9 Postby Audax » Tue Oct 17, 2017 4:58 pm

Hi guys,
Thank you much for your helpful advice. I spent a bit of time responding to Geoff, and the messgae has disappeared into cyber space.
Geoff...I will try your idea of bare and coated and see what results acrue.....thanks
Matt...the SMK wouldn't group at the max velocity I could get ~2820fps. Called Bartlien and they said two things are needed to run the SMK.....the velocity has to exceed 2800fps, and there was evidence the buttoned barrels didn't handle SMK too well, so I went with a cut 1:9" and that problem was solved, but I still cannot get a desirable ES/SD which of course is not that great at 1000yds ie 1 moa vertical spread.

The twist on the 1:8" is almost as good as a cut barrel ie 4 turns is equal to 805mm tighter at the muzzle end, closer than most buttoned barrels I have seen. I have given up on a 1:8T with 284 ......works fine with a SAUM, but muzzle energy limits mean it is like a V8 idling.......if you know what I mean ...!

It is interesting you have so much clearance on the bullet.....Dave Manson and I colluded on the clearance and he could see no issue with being so tight.....I thought it would provide the ideal gas seal being almost the same ID as the bore diameter of 0.284" and my ES/SD would be wonderful with no gas leakage......not so.....!

I am interested in your theory of why the freebore should be greater than the bore diameter, and whether you think the higher pressures leak more than the lower helping to allevaite the higher velocities somewhat......it is about the only thing I haven't ruled out.....!

Audax
Posts: 16
Joined: Wed Sep 27, 2017 8:48 am

Re: Mastering velocity ES 284W

#10 Postby Audax » Tue Oct 17, 2017 5:04 pm

Hi guys,
Thank you much for your helpful advice. I spent a bit of time responding to Geoff, and the messgae has disappeared into cyber space.
Geoff...I will try your idea of bare and coated and see what results acrue.....thanks
Matt...the SMK wouldn't group at the max velocity I could get ~2820fps. Called Bartlien and they said two things are needed to run the SMK.....the velocity has to exceed 2800fps, and there was evidence the buttoned barrels didn't handle SMK too well, so I went with a cut 1:9" and that problem was solved, but I still cannot get a desirable ES/SD which of course is not that great at 1000yds ie 1 moa vertical spread.

The twist on the 1:8" is almost as good as a cut barrel ie 4 turns is equal to 805mm tighter at the muzzle end, closer than most buttoned barrels I have seen. I have given up on a 1:8T with 284 ......works fine with a SAUM, but muzzle energy limits mean it is like a V8 idling.......if you know what I mean ...!

It is interesting you have so much clearance on the bullet.....Dave Manson and I colluded on the clearance and he could see no issue with being so tight.....I thought it would provide the ideal gas seal being almost the same ID as the bore diameter of 0.284" and my ES/SD would be wonderful with no gas leakage......not so.....!

I am interested in your theory of why the freebore should be greater than the bore diameter, and whether you think the higher pressures leak more than the lower helping to allevaite the higher velocities somewhat......it is about the only thing I haven't ruled out.....!

mike H
Posts: 501
Joined: Mon May 08, 2006 5:34 pm
Location: JUNEE NSW

Re: Mastering velocity ES 284W

#11 Postby mike H » Tue Oct 17, 2017 6:11 pm

This is very interesting,it may be worthwhile to send a couple of your 1-8 twist barrels to a shooting gunsmith and get them chambered to their specifications,they may be able to help.

Audax
Posts: 16
Joined: Wed Sep 27, 2017 8:48 am

Re: Mastering velocity ES 284W

#12 Postby Audax » Tue Oct 17, 2017 6:50 pm

I have seriously considered that Mike, but before doing so what I am thinking is that all may not be lost by increasing the bore to chamber a Berger or Lapua, this would create greater clearance for SMK and see if results change. Seems like Matt has tried tighter bores and is relaxed about increasing clearances to 0.0008".

Then I could test the Berger and Lapua in a tight bore to see if they have similar issues to the SMK in respect of velocity variations.

Could be tomorrow's job.....!

Rebel105
Posts: 504
Joined: Fri Jun 13, 2008 12:22 am

Re: Mastering velocity ES 284W

#13 Postby Rebel105 » Tue Oct 17, 2017 6:53 pm

Audax,
First thing you do now is reread what people have written, Understand what MattP has said, he has machined more 284 barrels than had breakfasts. Stop thinking too much about your theories, sorry if this sounds rude, but a 284 is easy to get going with standard time tested reamers either no neck turn or neck turn. Please have you barrel/chamber checked by a competent gunsmith before you use it again.
Geoff

Tim N
Posts: 716
Joined: Fri Jan 25, 2013 8:18 pm
Location: Branxton NSW

Re: Mastering velocity ES 284W

#14 Postby Tim N » Tue Oct 17, 2017 7:06 pm

Another thing to consider is carbon build up with your round count.
If you can get someone experienced to check with a borescope it may need a de carbon.
Appologies if I'm telling you nothing new
We don't rise to the level of our expectations, we fall to the level of our training. Archilochos 680-645 BC

Audax
Posts: 16
Joined: Wed Sep 27, 2017 8:48 am

Re: Mastering velocity ES 284W

#15 Postby Audax » Tue Oct 17, 2017 7:31 pm

Hi Tim,
No carbon....I have a 17" reach Hawkeye and I check after every clean....it is meticulously clean.

Geoff,
It is not a dangerous or serious chamber issue as I may have erouiously conveyed.....the ES is 35-45 fps, SD 9-15. It appears the tight freebore may be a failed experiment which I was always prepared to increase if required......I am simply trying to understand why it may not be working as I thought it should.

QuickLoad calculates the pressure circa 56000psi Pmax is 63000psi, and there is every indication the working pressures are indeed in the former region.......however I thank you for your concern.....!


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