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Accuracy Testing - Best Practices


blueeyedme

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While there is a tremendous amount of information for the new reloader to get started developing loads, there does not appear to be much information on the "how to" of accuracy testing. Share your best practices here for all of us.

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This is what I did for my Bianchi load. Assuming you have a quality firearm, and need great accuracy at 50 yds.

Pick powder, pick bullet. Research PPC/bullseye forums to see if I am close in components. For 50 yds, 2 inch groups, you will need a Zero, Sierra, Hornady or maybe Nosler bullet(as suggestex to me by KKM) Montana gold shoots good till 25, but opens up to much at 50. I havent tried a Precision Delta.

Start at min book load, load 10-20, bump load by .1gr, load 10-20 more. Repeat untill max charge is reached. Use a mid range OAL that works in your gun. I like to start around 1.12-1.13.

Test loads on a sandbag, or ransom rest. Pick out most accurate load. Then load 10-20 starting at about 1.110 and increase by .01 every 10-20 rounds up to the max length for your gun/magazine or chamber.

Choose the most accurate load and load a ton of it.

If you dont get something that meets your need, changr bullet weight or powder and start over. Havr your gun checked by a competent smith who builds precision handguns.

This process found me this load.. 5 shots 50 yds under and inch, I called the 6th flyer.

IMAG0037-1.jpg

Edited by DWFAN
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DWFAN is pretty on there. I have had similar accuracy out of my gun, the sixth shot is never a flyer with me it is operator error. Smallest group ever was .55" with 5 shots, actual sixth shot was loose and went to .85". Done it more than once so know for a fact the outer shot is ME!

Don't dismiss Montana Gold bullets, just because one person did not get tehm to work. A few guys here just love them. One finished 8th at Bianchi this year. His gun stays under 1" all day with the 115gr JHP from MG. I have seen him shoot it better from time to time.

Now the group attached is at 25Y, 38Super Zero 125gr JHP in my daughters Springfield based AP gun, this gun is ? years old and the front moves nearly an 1/8" left to right when you grab the comp. Groups at 50y are about 1.5" all the time.

post-789-0-86495800-1314692300_thumb.jpg

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Oh yes, that 6th shot was 100% my error, and I knew it when it went off.

The load was a 9mm, 4.3 gr Titegroup, 121 Hornady HAP, 1.130 oal. Through my bianchi gun, 6 inch Schuemann AET. All winchester brass. I just cant afford to shoot HAPs all the time.. Haha..

One guy around here got Montanas to shoot fot him, theyre about a 4 inch group for me. Just depends on the gun.

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How much does crimp factor in to things? I've heard arguments that more crimp provides a more consistent burn/case pressure. I tend to be of the opinion that crimping modifies the bullet and that's bad. Of course I have no data to back up that belief.

Also has anyone studied the effects of undersized dies on 50y accuracy?

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My accuracy suffers at 50 with a lee FCD, but not a u die.

I use moderate crimp, a faint mark on a pulled bullet. Another one of the trial and error things to try. Although to me its hard to duplicate crimp once you change a die setting.

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Oh yes, that 6th shot was 100% my error, and I knew it when it went off.

That leads to my tip...

Throw out one hole in each group. None of us is perfect and shooting 200 rounds from sandbags will cause even good shooters to loose mental focus.

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Never throw a shot out of a group. It is there so count it.

Use a sandbag to support the firearm if you want no fliers, or better yet don't shoot them. :sight:

My two best groups ever both contain a "flyer", 0.8" first 5 went into 0.55", 0.85" five of the six went 0.61" the "flyer" was shot #4. The first was clearly seperate from th emain group. The second I called oops as I fired that shot and it was clear of the other three and I essentially filled in the gap as I finished off.

The smallest was with Sierra the next smallest was with Zero.

I will however fire a shot into the berm to ensure that the pistol is loaded as in a match.

Crimp, less crimp will usually lead to an increase in ES over the chrono, but those groups above were with minimum crimp, I can get single digit ES (with a 10 shot sample) but th egroups are consistantly larger, not by much, but by a noticeable amount. You have to obviously crimp, how much is open to experimentation. Various brands of brass react differently to crimp. Certain bullets can manage more crimp than others, most plated bullets don't like too much.

Some people espouse no crimp if possible. I have tried polishing down the expander to 0.001" smaller than factory and just barely crimp just slightly straighten the case but still leave a light mark on a pulled bullet. I like this but you have to be careful how much you flare and how you seat the projectile. By not expanding the case so much you increase neck tension (to quote a rifle term) and therefore will not require so much crimp to ensure retention of the projectile and ensure that the powder will burn correctly. This theory is best for plated projectiles. But works very well with JHP.

For Lead I generaly find that with th ebullet being usually 0.001" larger than JHP or plated you just need to flare sufficiently to remove the chance of damage to the base of the projectile and crimp sufficiently well to prevent set back and allow pressure to build evenly, you are set.

I shoot predominatly Action Pistol, both guns I shoot most with just plain hate lead. Sierra or Zero JHP are what I use. I know that as a backup, Nosler, Hornady and Montana Gold all work in my guns. But Sierra and Zero are the easiest for me to acquire most often.

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What too many people do is to only fire a single group and a given charge weight and assume any exemplary groups must be the norm. I have never owned a single gun, not even a .32 S&W Long shooting 98gn wadcutters that could tell the difference in +/- 0.2 gn, repeatably.

Always shoot with a rest. Go from starting load to max load in 0.3-0.5gn increments.

When you find a load that looks good, load in 0.2gn increments from at least 0.5gn below to at least 0.5gn above, not to exceed max load. Next repeat until you see if any load is consistently accurate and not just "luck." You should find that there is a 0.5gn range where the loads are all reasonably accurate and you simply go with the middle charge.

If you see accuracy going UP and Down with just a 0.3gn change, the reason is you or your load technique. There is no secret charge that is super accurate if a charge 0.1 or 0.2 gn up or down gives you a 2" or larger group.

The problem also is if you keep looking for that one load that beats them all, you'll never settle on one load and practice with it. Establish what accuracy you need and find loads that meet or exceed that goal and practice.

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