How do you isolate variables when working up loads?

[rodgers65]

I've been reloading 9mm for IDPA for about 6 months now. Basically I found a recipe that fed reliably and was accurate enough, then ran with it. But now that winter set in and I have time on my hands, I'm starting to wonder if I'm really missing out on some accuracy advantages or reduced recoil from a better load.

Lets assume for now that the gun, primer and bullet are fixed variables. I start with x grains of Powder A, find a good OAL, and the right crimp. But it's not making power factor, so I have to increase the charge weight. Does that change the OAL and crimp?

Or what if Powder A is out of stock and I have to switch to Powder B, does that change OAL and crimp?

What about the same thing with primers?

Or would it be better to check PF before messing with OAL and crimp?

How do you guys go about finding the best combinations without having a butt-load of extra components laying around? It's not like you can get 1/8 lb of powder and 50 bullets/primers at a time for a taste test. At some point, do you just say "good enough"? I'd much rather spend my time behind the trigger than the loading bench, but there will always be a nagging thought that I'm not using the most accurate ammo if I don't do a reasonable amount of testing.

[kneelingatlas]

You've got a lot of questions there so I'll go after the easiest first: crimp. If you have your bullet of choice, gradually increase the crimp until the bullet can't be pushed in by pressing it down on the bench with your thumb.

Next is OAL: find a length which feeds reliably in your pistol(s) and stick to it.

Neither of these things really need to change unless there's a problem.

Primers: as long as your gun sets them off reliably you're GTG.

Powder: if I'm considering a powder I'll search this forum, if I come up empty, or just a few hits, I move along. The members here have spent TONS of time and money testing EVERYTHING; the chances you've thought of something no one else has are pretty slim. So I would suggest trying a few powders which are popular for your purpose and see which one you like best. For 9 minor lots of people use Clays, Title group, Bullseye, etc. What type of powder are you using?

Edited January 1, 2014 by kneelingatlas

[Sarge]

I first find a load that works in the gun and makes power factor. If it is accurate and feels good them I stop. If it's not grouping well or feels a little different from what I would consider good then I start messing with it. I move oal up and down without changing powder charge, I move oal up and down AND change powder charge, I move powder charge up and down without touching oal.

As far as variables for what we need out of our rounds for these games:

Any primer that works is good. I would probably get a ton of win SPP's and never look back.

I set crimp at .377 ish and never touch it

In 9mm I would just get a decent quality 124 grain bullet since 115's are too snappy and some guns don't shoot 147's very well.

Search here for what the majority thinks are good powders and go with it.

It takes quite a bit of testing to come up with an ideal load for you and your gun.

[rodgers65]

Thanks for the replies, I guess OAL and crimp aren't as crucial as I was thinking. Some testing with it yesterday showed minor differences in group size, but it's probably negligible. I'm currently using Bullseye and picked up some Titegroup to try, all with CCI primers. Right now I'm running through a box of 124gr Berrys RN, but typically use a lead cast 125gr RN. Sounds like if it's reliable and reasonably accurate, I should do some minor tinkering and devote my time improving the shooter.

[bowenbuilt]

One of the most prolific problems posted here is about crimping plated bullets such as the ones you are using. The secret to running plated bullets at their best is lack of crimp. You do NOT want to actually crimp these. All you want to do is eliminate the case flare so that the case is straight at the case mouth while not leaving any marks on the plated bullet or running the round so far into the taper crimp die as to change the original diameter of the bullet. Crimping auto pistol rounds does NOT hold them in place but has the exact opposite effect as the brass will spring back but the bullet will not. Case tension holds the bullet in place not the amount of crimp as it does in revolver ammunition. Using the search function at the top of the page will greatly help in choosing a good powder, powder charge and bullet weight. These are the variables that everyone has a different experience from. There is no easy way to find what you like because there is no exact science to choose your favorite until you actually experience it for yourself. Choose wisely and enjoy the ride.

[Sarge]

That's a long winded way of saying .377ish.

[Hi-Power Jack]

Rodgers, bullets are NOT fixed variables - unless you're in the happy position of having tens of thousands of one bullet.

Your gun might prefer one weight over another, and certainly one brand over another. Your gun might prefer .355, .356,

.357 sized bullets, also; or lead vs jacketed, etc.

Don't discount the effect of The Bullet

[GARD72977]

I have had good luck with almost every bullet. Usually it is just finding out how the gun wants you to load it.

[Steve RA]

To add to the discussion about crimp - or lack thereof - first take a razor blade (single edge is best) and hold it against the side of a factory round. You'll find the side of the case is straight (we're talking pistol, not revolver here). This is how reloads should be, case tension is what should hold the bullet firmly against "set back".

You should have a "wasp waist" effect to your loaded cartridges. If you don't then you need to polish whatever expands the neck after sizing until the diameter is reduced enough to gain the "wasp waist" effect.

Different brands of cases have different wall thicknesses and I suggest you sort your brass by brand and use the brand that works best for you.

Don't use a Lee Factory Crimp Die on plated or lead bullets.

This is what works for me, your results may differ.

[Mat Price]

+1 on not using a lfcd on plated or lead. It's great for jacketed bullets but I have personally NEVER had good luck loading lead moly or plated bullets with one. I keep a dillon crimp die on hand for my bayou bullets