Flat Spot Load Development Method - The HuntingPA.com Outdoor Community
 1Likes
Reply
 
LinkBack Thread Tools
post #1 of 12 (permalink) Old 08-30-2017, 08:29 AM Thread Starter
tdd
Super Moderator
 
Join Date: Jun 2009
Location: Northern Berks County, PA
Posts: 7,266
Back To Top
Flat Spot Load Development Method

I'll have to find the links I was sent and repost them, but folks I talk reloading with from other forums clued me in to this method, and it's a pretty slick concept.

The biggest "catch" is that you have to have a chronograph in order to do it. It won't work without it.

Here's my first workup----

I took my 270 Winchester, which is a pre-64 standard rifle with a 24" barrel. I had it shooting 150gr Nosler Ballistic Tips inside 1.5" at 200 yards, chrono'ing 2900-2960fps. Great load. Killed a couple bucks with it in South Carolina.

I decided I wanted to move it over to a 150gr Partition for my upcoming elk hunt. I tried just "swap the bullet and hope". It did...ok. About 25-30 rounds of work got me 2.5"-3.0" at 300 with 2800-2825fps. Useable.

Using the Flat Spot method, I expended 19 rounds and developed a load that shot 1.88" with one shot called slightly low, and that shot stretched the 3-shot group from about 3/4" to 1.88". At 200 yards. Speed was 3046fps for the 150PT. Before anyone has a stroke over that, I've measured my case capacity in my fired brass, run that through QuickLoad, and developed pretty solid data on what speeds track to pressures close to the 65k SAAMI limit. I'd have to be over 3100 by a bit, so 3040-3050 that I am getting is a good place to be....not too close to the edge, but getting what I can from the round. And 277 Partition at those speeds will work well for about any game animal I'm gonna hunt.

So here's the gist of it...

You get your load data, and load maybe 2 or 3 charges at least a couple grains under max. Shoot them to get speeds, and groups are immaterial, so shoot them into whatever.

Getting those initial speeds helps you calibrate your rifle and load data...i.e. if your data source predicts 2800fps and you get 2720fps, you know your rifle is not at the same pressure level as the data source's test rifle, and you can go higher in charge weight.

Knowing that, you develop a speed range you want to target, and make about a 2gr "range" of charge weights you'll be working with. You start at the bottom of the range and make 1 round at that weight. Go up 0.2gr, make one more round. Repeat until reaching the top of the range you selected.

Now go shoot them for speed. Groups don't matter. Shoot them in the dirt, in a target, whatever. You just need the speed. It's good to know what speed equals your "red line" that you shouldn't cross. Whether the rifle is giving sticky extraction or other pressure signs or NOT, you should know the speed you can't cross. If you find you've hit it, stop.

Record the speed for each round. What you'll more than likely find is that you'll have increments where the speeds increase 10, 20, even 30fps for just a tiny increase in powder. And then you'll find that you have increments of 0.5-1.0gr or so where the speed doesn't increase much at all as you add powder. That's your "flat spot". You may be able to find more than one, as well.

Once you've found the flat spot(s) in the speed range you want, calculate the middle point in the charge weights. Load up 4 rounds at the longest length you can in your rifle....meaning the longest that will cycle through the magazine, or if that's not a limiting factor, get to about 0.010" off the lands. Make another 4 at -0.010" from the first length. I usually do at least three lengths, but 4 wouldn't be a bad thing either. Now go shoot for groups.

More than likely, if the group you want doesn't appear, you'll see a clear trend in group size as the length varies. Work to follow that trend and the groups should tighten.

With the 270, I found my "longest I want to go in the mag well" length was 3.345" OAL. I shot 3.345, 3.335, and 3.325 OAL's with my "middle of the flat spot" charge.

3.345 shot a 6.5" group (you read that right) at 200. Wow.

3.335 shot a 4.25" group at 200.

3.325 shot a 1.88" group at 200.

Now I plan to re-run 3.325 to verify, but then to also run 3.320, 3.315, and 3.310, too, just to see if there's any refinement to be found.

The excitement for me here is that this helps take away a lot of the "try and see" blind experimenting we do in reloading. It makes it much more scientific and less "black magic" I think.

The key component is the chronograph, but a CLOSE second place is QuickLoad software. That really allows the reloader to get tuned in tight to what's going on with the rifle in question. When I give QL solid data, it consistenly predicts my chrono speeds to within +/- 15 or 20fps. This is how I find my "red line" that I know not to cross. When my speeds get close to the line, it's time to stop, whether I see any of the classic "pressure signs" or not. If I'm at those speeds, I'm at those pressures, and there's really no way around that.

Anyway, I just thought I'd share. It's a really interesting approach. I'm working with my 35 Whelen as well, and close to a good result. I'm about to start my 300WSM, and I hope next spring to take on more of my rifles and really tighten up my load work.
Hiamovi likes this.

Last edited by tdd; 08-30-2017 at 08:32 AM.
tdd is offline  
Sponsored Links
Advertisement
 
post #2 of 12 (permalink) Old 08-31-2017, 09:37 PM
Frequent Contributor
 
Join Date: Dec 2004
Location: Washington County, PA
Posts: 646
Back To Top
Some good info there. The process you described is very similar to how I do my load development. I always shoot through the chronograph just to get as much data as I can. I have noticed the flat spots while working through charge weights but never really concentrated on them. I am working on a target load now for my newly acquired custom 300 wsm. I'm gonna give this a try. My hunting load was so easy with this gun that I now want to start over with a match bullet just to see how good I can tune it.
Sekora is offline  
post #3 of 12 (permalink) Old 09-01-2017, 04:06 PM
Regular Visitor
 
Join Date: Aug 2014
Location: carlisle pa
Posts: 67
Back To Top
Nice write up and very good information. Thanks for posting.
psweigle is offline  
Sponsored Links
Advertisement
 
post #4 of 12 (permalink) Old 09-04-2017, 12:30 PM Thread Starter
tdd
Super Moderator
 
Join Date: Jun 2009
Location: Northern Berks County, PA
Posts: 7,266
Back To Top
This method has played out on my 35 Whelen now, too.

After working a few strings up to get good speed data, I started working seat depth.

Today it gave me a 1.98" group at 200 yards with a 250gr Nosler Partition moving at 2589fps at the muzzle off a good charge of IMR4320.

I'm digging this approach to load work a lot. The key to it, though, is a good chrono.
tdd is offline  
post #5 of 12 (permalink) Old 09-15-2017, 08:48 AM Thread Starter
tdd
Super Moderator
 
Join Date: Jun 2009
Location: Northern Berks County, PA
Posts: 7,266
Back To Top
Just to followup on this...

Shot the Whelen to confirm the group size would repeat. Same load that went 1.98" now went 1.56" (both at 200 yards).

I made some minor seat depth adjustments and saw that produce a group of 1.07" at 200 yards. I have been working with 250gr Nosler Partitions with that rifle, and they come in 25-ct boxes. I have not finished the 2nd box yet.

This rifle was a challenge for me with my "normal" reloading techniques of semi-organized "try and see". In what I think is about 40 rounds, I have it at or under MOA out to 200, and it's moving a 250gr PT at 2575-2590fps.

This method has been fantastic. It just makes things make sense.
tdd is offline  
post #6 of 12 (permalink) Old 09-18-2017, 09:54 AM Thread Starter
tdd
Super Moderator
 
Join Date: Jun 2009
Location: Northern Berks County, PA
Posts: 7,266
Back To Top
A little more data...hopefully this is useful to folks.

My 300WSM has been, since I bought it in 2010, a "blah" shooter. Killed several deer with it, but it's never wowed me. I'd get a great group, then a not great group. I just sort of gave up fighting with it and accepted it as a 1.5-moa (ish) shooter that was more than adequate for taking game.

I decided to run a flat spot ladder on it.

Turns out, my current load sits right on the edge of a flat spot. So I knocked the charge back 0.2gr (2/10's of a grain), and shot a group with 2 touching and one about 1-1.25" left of the two touching. Ok, I thought...this needs some seat depth work and we're set. I forgot that I had one round loaded that the bullet seated hard into the case mouth. Likely I didn't chamfer it well. I marked the case on that one, but forgot to look for and note when I shot in the sequence of rounds I fired. I think that might be the culprit.

So I let the rifle cool, and I shot three more. Perfect...PERFECT...cloverleaf that measured 0.41" (at 100 yards).

Need to shoot it a bit more, but this looks really promising.

I'm loving this method of load work. It seems to be really helping me sort out rifles better than I've ever had them sorted out.
tdd is offline  
post #7 of 12 (permalink) Old 09-24-2017, 08:41 AM
Hooked on HuntingPa
 
Join Date: Jul 2011
Location: NJ
Posts: 359
Back To Top
and the rifle has nothing to do with it right?


I saw a guy shoot a pre 64 06' with factory ammo and achieved the same thing.

do the homework before the hunt
milboltnut is offline  
post #8 of 12 (permalink) Old 09-24-2017, 07:20 PM Thread Starter
tdd
Super Moderator
 
Join Date: Jun 2009
Location: Northern Berks County, PA
Posts: 7,266
Back To Top
I'm not sure I understand your point?

Of the rifles I'm working with, one is a pre64 M70 and the others are later.

My point was that I have these rifles shooting around an inch. At 200 yards. With minimal components and loadwork involved.

If that sounds like it's as easy as opening a box of ammo.... it isn't.
tdd is offline  
post #9 of 12 (permalink) Old 09-24-2017, 07:32 PM
Hooked on HuntingPa
 
Join Date: Jul 2011
Location: NJ
Posts: 359
Back To Top
I can achieve a little over an inch with not a lot of load development...at 300 yards. Actually one load development of 1 grain increments 1 grain below max, and with that one load ALWAYS get a tight group.


If I get an inch or better with ONE load development, that's right one... at 100 yards and at 300, a little over an inch or an inch and a half.


A couple a days ago a shot a round, the book said 3K... through a chronograph and it said 2800. The test rifle was a model 70 with 24 inch barrel.. mine is 22 inch. I was polite to the guy with his chrony.. and in my mind didn't care nor was concerned about 200 feet per second drop.

do the homework before the hunt

Last edited by milboltnut; 09-24-2017 at 07:40 PM.
milboltnut is offline  
post #10 of 12 (permalink) Old 09-24-2017, 07:53 PM Thread Starter
tdd
Super Moderator
 
Join Date: Jun 2009
Location: Northern Berks County, PA
Posts: 7,266
Back To Top
2800 sounds very plausible in the situation.

You'll lose a solid 100fps for the barrel length difference and 100fps deviation from book values is very normal.
tdd is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the The HuntingPA.com Outdoor Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may not post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome