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Tuning a Load (part 2)

 
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Old 04-26-2007, 09:42 PM
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Tuning a Load (part 2)

OK Lets all play nice first off to include me.

I read an interesting article today by Ken Oehler in one of the gun mags (old age and I cannot remember which one).

He talked about his recommended method of tuning.

Obviously he is a big proponent of the need for a chrono as it helps ID pressure signs and out of sych components in a load. He discussed the need for this due to the fact that many people take the max load listed and either start right there and even go up to dangerous levels and use hard primers so they have no idea of the pressure ranges they operate under.

Basically he recommended working powder first, seating depth and then neck tension. Any load that would not give you and ES/SD of under 30 was a no winner.

Work the powder and then the seating depth for max accuracy and if using bushings the neck tension. Then tweak for low ES/SD was his basic system. That makes sense with any system.

It was interesting to see that he believed that as a final step you can change primers and dramatically change you your ES/SD. Which is what I have found also.

Basically if you think about it you have two pretty well established procedures and both can and will work as long as you understand certain limitations with them and accepted practices that you must do to give you quality information.

1. The ladder- I will be the first to say, probably not for a regular factory rifle. They are just not accurate enough to give you reliable results. However, if you are shooting a rifle with custom barrel or at least a heavy factory barrel, AND are after the min size group. I think it works well if you understand the limitations and practice proper procedures, such as shooting in no wind conditions, must have chrono, exact powder charges, brass prep, faith in your ability to know where the bullet "should have gone" .

2. Shooting groups-normally similar to a ladder but with shooting 2-5 shot groups in incremental steps. If it won't group with 2 it will not group with 5, so I limit 5 shot groups to final testing. Ideally test again in no wind condition, use chrono, exact charges etc. I have used this method and many other LR BR shooters use it to quickly ID loads thatllok like they work and pressure ranges.

Key practices that you should do no matter what method. Now these may be applicable to the degree of accuracy you are after. If I am looking for 1 MOA hunting loads, obviously things do not have to be as critical. If I want a gun to shoot legitimately 5 shot groups in the .1-2 range, then absolutely zero shortcuts can be taken.

Define your realistic expectations. Custom gun top notch action, barrel trigger etc. Should easily go .5 and under. Will it go in the .1 range, not really and consistently. Factory heavy barrel- Goal might be .5 but it really might not get there and to expect a .3 consistently ( 5 five shot groups in a row day after day) is totally unrealistic. Consistency is the key in all cases, not the once in a life time 3 shot group.

1. Best brass- RWS, Lapua, Norma, Win, Fed and Rem. That is my order of pref. IF you can use RWS, it will wear out 3 barrels and is by far most uniform.

2. Bullets- Choose what is best type for your target. Hunting or paper? May want to weigh and sort by ogive (two Stoney point comparaters on dial caliper or Buhay ogive checker).. Some even spin them on a Juenke and sort that way.

3. Powder- I recommend a non-temp sensitive powder. To me that means Hodgen line is the first choice normally. I also love Norma MRP for my WSMs. Are there others, sure. Easy to pick 1-2 go to non sensitive powders that give you max fill in the case without a compressed charge, and are always recommended.

4. Primers- Most have found magnum primers are often not needed with magnum cases and really can cause problems except in very large cases with very slow burning powder. Oehler talked about this also. Primer sensitiviy CAN be an issue, for example CCI 35s are used in the M1 and M1A to prevent slam fires, and are obviously extremely tough. Federals are more sensitive. I use mainly federal and CCIs and occasionaly the Win. However, I also have some Rems laying there, along with PMC just to check IF drastic measures are called for. Understand the limitations of what you use.

4. Weighing charges- got to be precise IF extreme accuracy is called for and not so precise if just a 1 MOA hunting load. I use a Ohaus Navigator that measures to the .01 grain along with a Harrels measure. Some guys can throw to the .1 with a Harrels but I cannot especially with the large kernal powders. I also have a little CED digital ($95) that has proven to be just as accurate as the Ohaus ($450).

5. I ream all primer pockets and flasholes and neck turn only on a tight neck gun normally. If my hunting cases are that lopsided, they might get the high spots touched off if I am using a bushing die or just trashed. I will test one case to see what kind of neck tension I can maintain first though. Hunting load in a magazine should have min of .003 tension, which means the neck needs to be sized .004. Recoil on bullets in mags with loose neck tension will move in the neck upon firing at times.

6. I load with .3 gr increments over a 3-4 gr spread for WSM or Win Mag size case, and .5 for the 338 Lapua size and a 5-7 gr spread with a 2-3 gr spread and .2 inteval for BR cases. My spread stops at 2-5% over book max normally. That allows me to ID the upper limit for my gun and probably hit two nodes. Custom actions, min SAAMI chambers and tight control of tolerances and reloading might and many times allows you to go over book max. NOT RECOMMEDED for the inexperienced and without a chrono. Now that means do not do it in your Rem 700. Many times the lower node will give you the best accuracy, but you might want the upper node for a hunting load. I may not fire all them IF I start getting my pressure signs that I do not like, such as excess primer flow, case head expansion that suddenly jumps over the norm for that case. Now if you are after a hunting load only and want max MV you can cut the spread range down some but use the same increment steps on the charges. You are after only the upper node.

7. Seating depth- depends on magazine or not and VLD or not. If a mag, seat to max OAL for mag, if single shot and VLD seat .030 in and if non VLD seat touching. That way, all you have to do is go one way to check. Most VLDs will like .020 or so in and most non VLDs will like just touching to .040 off. Barnes even has some that like as far as .070 off. At this stage, go to neck tension if you using bushing dies.

8. Chrono- IMO no reason not to have a decent one if you want accurate loads. Obviously Oehler if you can get one, the PACT, CED etc are good. The Chrony's seem to be real hit and miss. Check yours against an Oehler if possible so you know is it consistent and how does it read (high, low etc) for reference. MV that is consistent is a sign of a decent powder load and whether you shoot a ladder or incremental groups IF you record your data you will see large jumps in MV from one load to the next and then 2-3 loads will have very small jumps and be very consistent in their readings. This is probably a node, you want to ID the upper and lower limits and tune in the middle. Smaller incremental steps. That way pressure spikes by temp, and othe variations will not be a problem.

Good example of why to use a chrono. I built a WSM hunting gun shoot Barnes 168s and tested up to the max book loads. My MV was over 100 fps slower than what it should be with zero pressure signs on Fed primer. Not sure why exactly but it finally took another 2 gr to come up and there was a very good load in that area. Three of us shoot WSMs with 210s and we range from 2950-3050, powder is MRP, barrels are all 30" and the loads for each are from 64.5-67.0 grain and the largest did not give the highest MV. NO pressure signs and we all used F210s in custom actions and min SAAMI chambers. We all closely check case head expansion, neck tension etc all the time.

Reamers and throats will effect pressure. Barrel land style will effect MV and pressure, such as the 5R, 5C canted riflings are faster with less pressure which means more powder and within safe limits.

8. I work powder loads for final tune in .1 gr increments and 5 shot groups. Normally we are only talking .1 gr either way from my middle (3 x 5 shots)

9. After that I work seating depth in .10 increments with 3 shot groups to find where it tightens and then opens and final tune from there with .5 increments

10. If my group is good but my ES/SD is high try a primer change with 1-2 different primers. ie change from mag to standard, in a BR go from a standard to the 450 etc. Little discussion or online research will give you the recommended ones to try.

11. Final step is normally 3 five shot groups at distance of 300 yds min to confirm groups, repeatability of MV, ES/SD etc.

12. At the range. Zero wind condition at early morning or late evening. Good solid rest is a must. Not necessarily a BR needed, but a decent one only costs $100 and then $30 for rear bag and there are two bag combos that can be used. Chrono, we talked that. A log book to record everything in before you leave the range. Fouling rounds are a must and to get an initial zero IF you do not have one. Confirm zero and foul the barrel (start with a clean barrel) confirm the chrono is working. Start your firing. One shot wait min one minute. Record the data, and your shot call if you pulled it out. Measure case head expansion from virgin brass to once fired and record. This will show you where pressure starts when it starts going over the once fired number. Look at primers for excess flow, cratering, and extractor marks on case bottom. Now soft cases such as Norma can show a slight extractor mark with safe but upper end pressures depending on the extractor. What do all the cumulative signs show you is the key. Shoot and record. Analyize and then work up next set of tuning loads. 2-3 short range sessions and less than 100 rounds will have an extremely accurate load normally and even quicker for a hunting load.

Finally, do your homework before loading. Read the manuals, I have them all but now there are many websites that list recommended loads. What are the common case, primers, powder and bullets? Put together a little test plan of components that you are going to go to first and then second. What is top charge weights on powder for that case and bullet? Write your plan and then start the loading and testing.

There is a third method that is basically a round robin group ladder method called the OCW. However, that method argues against the need for a chrono, says start at the upper end of recommended charges and says that there is one universal load for each caliber/bullet regardless of the throat, chamber and barrel configurations. However, they also now state that this method is only good for "practical rifles" and 1 MOA and maybe .5 MOA loads. I think the focus on upper end limits at book max, do not use or need a chrono and belief that there is a universal load in spite of obvious individual gun differences raises issues with this method. Now add a chrono and precise testing plan to discover what your gun really wants and let it take you there and OK.

Now what does this all mean? You have couple methods to use, but if you stop and think they all require you to put the same thought, preparation, planning and conduct of testing to get quality results. Understand the limitations of what you, your gun and your equipment can or cannot do and work from there.

this is a down and dirty explanation along with what I think are pitfalls, issues and areas you need to think about. Have it and make em go into little bugholes.

BH
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Old 04-27-2007, 05:34 PM
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Re: Tuning a Load (part 2)

Now that was good reading thanks.
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Old 04-27-2007, 06:34 PM
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Re: Tuning a Load (part 2)

++1
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Old 04-28-2007, 10:49 AM
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Re: Tuning a Load (part 2)

Thanks BH,great read.
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Old 04-28-2007, 04:48 PM
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Re: Tuning a Load (part 2)

Good information here BH. I'll be saving this one for common reference.
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Old 04-28-2007, 05:04 PM
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Re: Tuning a Load (part 2)

[ QUOTE ]
++1

[/ QUOTE ]

That does not do the poster justice!

You took a bad situation and gave plenty of thought and insight to this post. You answered the original question and took it further. IMO, many will benefit from this post.

Thank you [img]/ubbthreads/images/graemlins/smile.gif[/img]

edge.
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Old 04-28-2007, 08:13 PM
oso oso is offline
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Re: Tuning a Load (part 2)

Well done! Very informative should be great for a lot of folks.

Thanks for taking the time to write it.
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