A Reliable 27gr Reload

Reloading info for the 5.7x28mm

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Rifles2
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A Reliable 27gr Reload

Post by Rifles2 » 10 Aug 2011, 09:13

Hey guys. I'm a long time reader of the Forum and finally decided to sign up & contribute. Wanted to share with you the results I've had with a semi-replica of FN's SS195LF, which I call the DHX195RL. I've been working on it for the past year and it's taken me more than 2,000 tries to get this damned thing figured out, but I finally did and figured I'd share the good news. Apologies for all the pointy-headed stats & analysis that follows, but that's what I do for a living and the only way I could prove to myself that my stuff is as good as FN's factory bullets.

A little about the bullet: It is a dual core (lead & polymer), swaged bullet with an open tip and flat base. I've got the core proportions figured out to give me a 27gr finished bullet (+- 1%) for all three versions (I make them from jacket nominal lengths of: .600", .705", and .740"). Here's a shot of the components, a couple finished bullets and one that I sawed in half.

Image

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As you can see, the plastic core fills the bottom two thirds or so allowing me to push the lead forward to improve stability (or at least maintain it given the different densities of the cores). Figuring out this center of gravity was the most recent breakthrough that allowed me to get the bullet I wanted. There were a hundred others, which is why it took forever.

My last trip to the range allowed me to capture the results, which I summarize below. For those unfamiliar with stats, I posted a shooting analysis primer on my blog here: http://www.dhxbullets.com/Shooting-Anal ... r_b_4.html (I know, shameless plug). Feel free to refer to it if this analysis doesn't make any sense. I've read you guys for a couple years now and this is a pretty smart forum so no sense dumbing it down.

Ok, so the test is between the DHX195 Reloads and FNH's SS195LF factory ammunition, with the goal to see whether the two lots had the same or different levels of precision. I loaded my bullets with 5.2gr of TB and seated them to an overall length of 1.585". Both lots were shot from my PS90 tri-rail with a 4x32 scope at an indoor 50' range. I used a Stoney Point steel bench rest modified to fit the PS90. Targets were 1 3/4" diameter, with 12 sequentially numbered targets to a sheet. My wife mixed up three round groups across two magazines, wrote down the sequences and kept them until I got home. This way I did not know which groups were mine and which were FN's while shooting. Here are what the two lots looked like after decomposing them with my wife's list and entering them into Minitab:

Image

Aside from having to zero that scope about a 3/8" down & a 1/4" right, it's hard to see anything obvious here. Maybe I was a little more wild on a couple of the outliers in the upper right. The scale here is in 1/8" increments or about 2 3/16" tall by 1 9/16" wide (scale modified for best fit). But to make any sense of this it's got to be plotted by shot group. Here's what that looks like for DHX and for FN, respectively:

Image

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So now the question becomes which of those lots is better in terms of group precision? Well, the residuals (distance between each shot and its group average) tell the story. Here are what the two residual distributions look like:

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Now we've got some actual stats to compare. My bullets had an average residual of .2585" while FN's came in slightly higher at .2663". That's only a difference of .0078", which is practically insignificant. FN's standard deviation was smaller, but again the difference was negligible (.0047"). Here are some of the other stats:
Descriptive Statistics: Residual (in)

Variable Lot N N* Mean SE Mean StDev Minimum Q1 Median Residual (in)
DHX 41 0 0.2585 0.0215 0.1377 0.0466 0.1801 0.2438
FNH 29 0 0.2663 0.0247 0.1330 0.0659 0.1627 0.2610

Variable Lot Q3 Maximum Residual (in)
DHX 0.3177 0.6156
FNH 0.3473 0.5867

I ran a few statistical tests to confirm that the means, medians and variances are all statistically equivalent and I'm proud to say that they are. Practically speaking that means I've finally made a bullet that shoots as good as FNs. I've got a couple other things I'm going to try to see if I can improve on this, but for now I'm pretty pleased.

I'd appreciate any feedback and am happy to reply to questions about the bullet or anything else. Also wanted to offer them to anyone who wants to try them out. Just look up DHXBullets.com to order or give me a call and I'll make you up a lot of a hundred. They are excellent bullets for the 5.7 cartridge. And, as I mentioned earlier, I keep a blog there that I post about new insights to the world of swaging, shooting and the associated stats.

Thanks for reading.

Dave


Test results:
Two-Sample T-Test and CI: Residual (in), Lot

Two-sample T for Residual (in)

Lot N Mean StDev SE Mean
DHX 41 0.259 0.138 0.022
FNH 29 0.266 0.133 0.025


Difference = mu (DHX) - mu (FNH)
Estimate for difference: -0.0078
95% CI for difference: (-0.0735, 0.0580)
T-Test of difference = 0 (vs not =): T-Value = -0.24 P-Value = 0.814 DF = 68
Both use Pooled StDev = 0.1358


Kruskal-Wallis Test: Residual (in) versus Lot

Kruskal-Wallis Test on Residual (in)

Lot N Median Ave Rank Z
DHX 41 0.2438 34.9 -0.32
FNH 29 0.2610 36.4 0.32
Overall 70 35.5

H = 0.10 DF = 1 P = 0.752
H = 0.10 DF = 1 P = 0.752 (adjusted for ties)


Test and CI for Two Variances: Residual (in) vs Lot

Method

Null hypothesis Variance(DHX) / Variance(FNH) = 1
Alternative hypothesis Variance(DHX) / Variance(FNH) not = 1
Significance level Alpha = 0.05


Statistics

Lot N StDev Variance
DHX 41 0.138 0.019
FNH 29 0.133 0.018

Ratio of standard deviations = 1.036
Ratio of variances = 1.072


95% Confidence Intervals

CI for
Distribution CI for StDev Variance
of Data Ratio Ratio
Normal (0.724, 1.450) (0.524, 2.104)
Continuous (0.653, 1.565) (0.427, 2.449)


Tests

Test
Method DF1 DF2 Statistic P-Value
F Test (normal) 40 28 1.07 0.859
Levene's Test (any continuous) 1 68 0.02 0.884

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Re: A Reliable 27gr Reload

Post by MrSlippyFist » 10 Aug 2011, 09:25

Thanks for the awesome contribution!
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Re: A Reliable 27gr Reload

Post by Grantness » 10 Aug 2011, 09:31

Tremendous work Dave! Your meticulous study is extremely impressive.

I have a couple questions:

What is the length of the bullet in the test? When you mention jacket nominal lengths are you talking about before or after swaging?

Have you done any tests to see how fast the bullet can go or how it compares in velocity to the FN bullet per a given charge?

With the lead forward in the bullet, do you think the center of gravity is such that the bullet would not tumble/yaw in the same way as the FN bullet on impact (in soft targets like ballistic gelatin for instance)?

Again, fantastic job! Fascinating :thumb: :thumb: :clap:

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Re: A Reliable 27gr Reload

Post by Rifles2 » 10 Aug 2011, 09:59

Thanks Guys. Regarding your questions Grantness:

The test lot was the longest bullet I make (.740"), although I've done similar tests with the same results for the .600"s and .705"s. The process adds different amounts for the three but generally between .001" - .018", depending on the lot I'm making and where I want to put the CG. The ones in this test averaged .753".

Haven't done any speed tests since I only have regular access to an indoor range that's always crowded. Maybe someone on the forum can help us out with that.

And an excellent question regarding the CG. I did one test on an outdoor 100yd range just to see if these would fly true at the longer range and they did (results posted to blog). But unfortunately I can't comment on ballistic gelatin impacts since I haven't conducted that test. Definitely a worthwhile test though.

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Re: A Reliable 27gr Reload

Post by Grantness » 10 Aug 2011, 10:32

Thanks for answering my questions.

If you need someone to help see how fast you can take this bullet I'd be more than happy to work up some nice loads for it... I could also find out what loads you would need to get the same velocity out of both the FN bullet and yours, as that could have had an impact on the testing you did. I've never worked with gelatin before but several others on the forum have like JGreenburg and Elite Ammo. I would certainly understand if you didn't want to let others have these bullets just yet.

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Re: A Reliable 27gr Reload

Post by eVenom » 10 Aug 2011, 18:25

Very good work!

The Demand for this could be great!

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Re: A Reliable 27gr Reload

Post by Grantness » 10 Aug 2011, 18:30

My guess is the lead will expand or break up while the polymer takes a separate, but shorter path (assuming it is lighter). Depending on the velocity, it might not break up at all.... the lead and jacket could simply squish against and around the polymer.Tumbling seems unlikely unless the weight is centered more towards the rear. Still, its a big departure from 30gr Vmax's, Bergers, or Varmint Grenades...

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Re: A Reliable 27gr Reload

Post by Rifles2 » 11 Aug 2011, 04:57

Grantness - Thanks for putting together the load data for this. I'm pretty sure you'll be pleased with their performance and I'm anxious to see how it compares to the factory stuff.

For others who also want to purchase a lot, we have them in stock now at: http://www.dhxbullets.com. We also offer some pretty hard core analytical products if you're interested in the specific weight or length parameters of the lot you buy.

Thanks for checking us out.

Dave

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Re: A Reliable 27gr Reload

Post by panzermk2 » 11 Aug 2011, 09:55

Have you thought about putting the lead in the base and the nylon then on top of it?
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Re: A Reliable 27gr Reload

Post by Rifles2 » 11 Aug 2011, 11:25

Panzer - I did make one lot with the lead and polymer reversed and actually got similar results on the 50' indoor range (although I didn't test them against FN's ammo). I reverted back to the lead-forward model because I thought it would stabilize better at the longer distances on the outdoor range, which I've since verified. I should have tested some polymer tipped rounds on the 100yd range too, but it never occurred to me to try. It wouldn't be hard to reverse that part of the manufacturing process though.

Curious to know if you see any benefit of having the lead in the base vs. forward?

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Re: A Reliable 27gr Reload

Post by Esteves » 11 Aug 2011, 11:59

Rifles2 wrote: Curious to know if you see any benefit of having the lead in the base vs. forward?
Terminal ballistics. With the weight rearward, the bullet is much more likely to upset after penetration.
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Re: A Reliable 27gr Reload

Post by panzermk2 » 11 Aug 2011, 12:18

Yep with the weight up front the bullet will hardly upset at all. With it to the rear as soon as the bullets hits the media it will start to tumble.
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Re: A Reliable 27gr Reload

Post by Rifles2 » 12 Aug 2011, 05:25

Thanks guys. I've been so single-minded on matching the flight characteristics to the SS195LF that I completely overlooked the terminal ballistics. Will work that up and share the results - maybe even get some ballistic gel and compare the differences. Should be interesting.

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Re: A Reliable 27gr Reload

Post by Rifles2 » 12 Aug 2011, 16:33

Here's a shot of the revised .705" lead base. Will post test results when they're available.

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Re: A Reliable 27gr Reload

Post by Grantness » 13 Aug 2011, 10:36

A boat tail would more closely resemble the SS195 an perhaps add some length. Would that be a great difficulty to add?

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Re: A Reliable 27gr Reload

Post by Rifles2 » 13 Aug 2011, 12:15

Yeah, that probably will be the next improvement on the design. I just got done with the FMJ prototype today, which has a cupped base rather than the traditional BT. Need some additional tooling for the BT, but I'll probably get it before too long. Here's a shot of the new prototype. Its jacket starts at .705" and ends up about .748" with the same 27gr weight.

Image

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Re: A Reliable 27gr Reload

Post by Grantness » 13 Aug 2011, 13:05

That's great. The longer the better (if you can get it to tumble).

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Re: A Reliable 27gr Reload

Post by VeTTeMaNC486 » 13 Aug 2011, 19:42

Holy crap. Very nice.

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Re: A Reliable 27gr Reload

Post by Rifles2 » 23 Aug 2011, 04:46

Worked up the new FMJ prototypes for testing, hopefully this weekend. Will post results of this and our new lead-base round shortly.

Also, DHX is running a special through Labor Day: 100pcs of 1x fired brass and 10% off every order of 100 bullets or more while supplies last. Promo code = fsforum
Visit our link on the forum banner to find us.

Grasias
Last edited by Rifles2 on 25 Aug 2011, 09:43, edited 1 time in total.

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Re: A Reliable 27gr Reload

Post by Wollychop » 23 Aug 2011, 08:25

Can't wait to try these out! Any timeline on availability?

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