[gicos]

You Rock Xman

Again I can't thank you enough for testing these. You solidly proved my beliefs from before the testing. The wheel doesn't need to be reinvented. So many great cartridges and rifles have gone by the wayside only because of mass marketing and big money. The Hot Cores can be found at just about every store that carries bullets and are as affordable as anything available today. I won't hesitate to use them on Colorado elk. They're less explosive in the SPC than the 270 and it just reconfirms, again, that it's much more about matching the bullet to the impact velocity than about bullet construction. You deserve serious kudos for all the work you've put in and been willing to share. My campfire's always open.

 

[dwb]

Thanks for all the work you have done,this really helps us reloaders. Xman I got some 130 corlocks that was bought 15-20 years ago,do you think that are the same as the ones you tested.

 

[Xman]

I got some 130 corlocks that was bought 15-20 years ago,do you think that are the same as the ones you tested.

dwb, the Core-Lokt design has been around for a long time. If your bullets have cannelures, they should be the same as the ones tested. I think the legacy 130 Core-Lokts did well in the 6.8 because of the lower energy levels didn't cause the bullet to lose its structural integrity which is what can happen when fired from more powerful cartridge. A couple of years ago, Remington came up out with their new Core-Lokt design called Ultra-Bond. These newer Core-Lokts should hold together better and have higher weight retention when they impact at higher energy levels.

 

[Xman]

Alternative Bullet Trap

Based on suggestions from gicos, I have been working on an alternative bullet trap. The original bullet trap (a gallon water jug with a box containing 1500 pages of phone book and a stack of magazines behind it) has worked well for monolithic/copper bullets, fragmentation bullets, and lead-core bullets with above average hardness. Lead-core bullets with softer lead cores have shown evidence that they continue to deform inside the phonebook. Gicos thought using a stack of newspaper saturated with water would be more suitable for these type bullets. He was correct and I have been testing this alternative bullet trap concurrently with the original bullet trap over the past several tests to learn its characteristics and define a process for building and using it. The bullets shown since post #401 have been tested using both methods. Most of the recovered bullets displayed since then have been from the alternative bullet trap.

 

[Xman]

Original vs Alternative Bullet Traps

A comparison test was done with the alternative bullet trap located 100 yards away using the 6.8mm Federal 90gr Gold Dot, .277 Nosler 150gr AccuBond Long Range (AB LR), and the .277 Hornady 130gr GMX. These bullets were chosen because I have recovered examples from deer (90gr GD) and elk (130gr GMX) plus the 150gr AB LR is the softest lead-core bullet I know of. I often am unable to pull a AB LR from a case with a collet pullet. It just squeezes the bullet to a smaller diameter and slips off. The recovered bullets from this initial alternative bullet trap test are shown in the picture below. The bullets recovered from the alternative trap are in the front row with a corresponding bullet from the original trap in the second row.

Results: The two GMX bullets had expanded to the exact same diameter, 0.529". For the 150gr AB LRs, the biggest difference between the two was bullet weight, and even that was small. The bullet from the original trapped weighted 55 grains and from the alternative, 58 grains, 3 grains difference. You can see the advantage of the alternative testing method with the 90 gr which had a more uniform mushroom similar to the one recovered from live game (back row right side). The 90 GD from the original bullet trap weighted 71 grains and from the alternative, 78 grains.

 

[Xman]

Going Forward

The alternative bullet trap comprised of just water soaked paper sounds simple but has some complications. It gets pretty heavy and can become too much for one guy to handle. I have tried just 12 inches of wet paper with phonebooks behind that. However, bullet deformation still occurred when the softer lead-core bullets entered the phonebook. At least 18 inches of water soaked paper is need to capture most 6.8mm bullets. To make the trap easier to handle, I have had to break the wet papers down into sections contained in Walmart bags. A Phonebook and or foam core is still required as an emergency backstop in case a bullet's penetration goes all the way through the wet newspaper stack.

I started out testing at 100 and 200 yards but now have settled at 25 yards and down load powder charge to stagger velocity, e.g., 33 gr CFE, 29 gr H335, 25 R10x and 23 R10x. For shot velocities below 2000fps, the .270 and 25 gr of TrailBoss are use. The .270's 1:10 twist makes sure the bullet is still stable enough to remain true on impact. I typically shoot 4 to 6 bullets into the trap before disassembling to search for the bullets. I have to work front to back in 2-inch sections or less to see if the bullet yawed or veered off a straight course. This way I make sure I know which bullet is which when I get to them. This process also gives a good view of how large and long the wound channel was. It has been essentially impossible to recover fragments from the alternative bullet trap, even when 90 grains of copper and lead have been left behind as was the case with the 150 AB LR.

Getting a supply of newspaper requires collecting them from the neighbors which has been pleasant. I started building the traps at home by setting up the papers in a trash bag and box then presoaking. It can take as long as 2 days for the water to penetrate and soak all the papers. I now build the alternative traps at the range. I fill a large cooler with water, put 3 stacks of paper inside, then place six gallon water jugs on top of the paper stacks (2 per stack) to get them to slowly sink. The papers are saturated by the time I get to the range an hour later. The water is squeezed out with body weight and a wood board then stacked into the bags/trap. I've built a wood fixture to hold the alternative trap which has also been helpful.

I'm still learning the particulars on how to use the alternative bullet trap and set it up. When I use it, I still test with the original trap as I am more familiar with it and how it correlates to live game. Results from both traps are cross reference which continues the learning process. This alternative bullet trap provides more realistic tests for soft-lead core bullets that are designed to expand/mushroom with limited fragmentation. It also offers new options for presenting data which you will coming up in the next test with the 130gr Speer BTSP.

 

[Texas Hog Man]

X-man....love the new wet trap, excellent idea.
As we spoke before, lit looks like the 150ablr would be decent for thin skinned animal but not good for larger game or bone shots....that 130 gmx looks fabulous!

I think you noted a while back that you would be testing 30 cal bullets too (like you haven't done enough for the 277 cal yet!!!)

I can't wait to see some expansion testing for the soon to be released nexgen.

Keep up the fabulous work!

 

[Roop]

My brother and I built a similar trap when we were teenagers, we used a 12gal bucket I had sourced from my job as a lifeguard (chlorine for the pool was shipped in them), packed with wet newsprint. It was a trial and error task figuring out how to get the paper to soak, then figuring out how to shoot it without wrecking our bucket. We used it with great success to determine which .22lr rounds we wanted to use for ground squirrels. Plus, it was a cool science fair project. eventually we accidently sent a round out the side of the bucked and had to quit. Nice work and keep it up, I look foward to future data with this method!

 

[obawon]

The alternative looks promising. One potential downside is if there is no water jug in front, you don't get a visual qualitative assessment of the hydrostatic shock potential...not sure how significant that is but figured I'd throw it out there. Whatever the final selection, three cheers for Xman and his bullet testing.

 

[Xman]

The alternative looks promising. One potential downside is if there is no water jug in front, you don't get a visual qualitative assessment of the hydrostatic shock potential...

You are correct in that the strike on the water jug is very telling on terminal performance.

Whatever the final selection,

I will be using either or both test methods going forward based on the bullet's construction. The alternative method is time consuming to collect the assets and prepare the set-up so I can't use it all the time but it is essential for bullets that have soft lead-cores that are designed to expand. Even when relying on the alternative, I still will do the orginal test method because it will allow me to correlate and learn what to look for in the alternative method.

 

[obawon]

Awesome work

 

[Xman]

Speer 130gr Boat-Tail Soft Point (BTSP)

The picture below shows two of the Speer 130 BTSPs in a line-up with other 130gr lead-core bullets. In my 18" ARP the 130 BTSP made contact with the lands at a 2.400" COAL. This bullet has one of the better ballistic coefficients for a non-tipped 130gr .277 bullet [1.095" BC 0.450] giving it a down-range advantage, especially if the starting velocity is 2400 fps or higher. The 130 BTSP on the right has had its tip clipped so it can be seated further out and still be magazine length. This shortened the bullet by 0.113" [0.982", BC 0.4??] making a COAL of 2.277" possible with max case volume which would benefit a slow burning powder like CFE223. All test shots were done at a COAL of 2.295" or shorter. Thank obawon for contributing the 130 Speer BTSP for testing.

From 6.8 SPC II - 18" ARP 1:11 barrel, 45F
130gr Speer BTSP - 2387 fps (29.0gr H335) [1.095" BC 0.450] - 2.295" COAL
130gr Speer BTSP - 2448 fps (33.0gr CFE223)

Caution - these loads worked in my rifle but this is no guarantee that they will work safely in yours.

The Speer BTSP is not a bonded bullet like the MSR bullets Speer makes for Federal. It's not listed as a HotCore but is likely made with a similar process as the lead from the soft-point bleeds over the copper jacket making it look bigger than it actually is. You can see this in the cross-section obawon provided when compared to the whole bullet. You can also see the jacket is very thin and there is no canulure to mechanically "lock" the core to the copper jacket. Canulures often are ineffective if the copper jacket balloons and stretches on impact, releasing the lead-core to fragment and penetrate while the copper jacket slows behind it (this is typical of the 120 SST). I was interested to see if the copper jacket would balloon and release its lead-core or retain it like the 130gr Remington CoreLokt did.

 

[Xman]

130gr Speer BTSP Terminal Testing Results

The Speer 130gr BTSP retained its core on 5 out of 7 test shots which I was not expecting. This is likely because its copper jacket was only 0.012" thick along the ogive. It peeled back like the Remington CoreLokt which also retained its core well compared to lead-core bullets with thicker copper jackets. At 100 yards, the impact showed an above average wound cavity (water slug on the outside of the bullet trap) which I believe was due to significant fragmentation. The copper jacket was recovered 1300 pages into the phonebook and the majority of the lead-core fragments were at 1500 which is excellent penetration for a Southern-size deer. The core with fragments from this bullet are in the second row on the right. The other bullet that lost its core is on its left and was recovered from the alternative bullet trap (wet-soaked newspaper). The bullets in the front row were also from the alternative bullet trap. Recovering fragments with this new test procedure is like finding a needle in a haystack. However, the amount of fragmentation is easily calculated as you can see in the weight vs velocity graph below. It also appears this type of analysis can derive the minimum expansion velocity which should be around 1700 fps for the Speer BTSP. Also, included is the Speer HotCore which did not fragment as much but still plotted a straight line. The clipped bullet's unfired weight was 128gr and had similar performance on impact.

Add another 130gr bullet that is effective in the 6.8mm SPC.

 

[Xman]

130gr Speer BTSP Ballistic Chart

With the BTSP's excellent BC and expansion, this bullet is a candidate for longer range hunting situation. Below is a ballistic table using a 200-yard zero. For those that use mil-dot reticles, ballistic drop compensation (BDC) matches nicely with the first mil-dot being 300 yards and 400 yards just a faction below the second mil-dot.

With its class-leading BC of .450, the Speer BTSP should maintain or have a performance advantage over the 120 SST and 110 AB which the other 130gr lead-core bullets could not do.

Hmm … time to do some load development and test for accuracy.

 

[obawon]

Xman. Thanks for another great test. Good to see that the little speer shows so much promise for the 6.8!

 

[sealer39]

Xman,
Have you experimented with clipping the tips of the 120sst? I was considering doing this to increase the OAL as opposed to modifying a mag. I can test for accuracy myself but I'm wondering how it would affect the performance on impact.

 

[Xman]

sealer, clipping the tips have promoted expansion in every bullet I've tested. Here is the affect on 130gr SSTs. Increase drag from the clipped tip showed up with more bullet drop at 200 yards.

http://68forums.com/forums/showthre.../showthread.php?33178-6-8-SPC-Bullet-Performance&p=471451&viewfull=1#post471451

Not sure what advantage will be gained by loading long with clipped 120 SSTs. I haven't found where loading longer reduces chamber pressure significantly enough to make a differences with typical 6.8 powders. It may actually increase chamber pressure as you get closer to the lands. If using a slower powder like CFE, there isn't enough volume increase to be much faster than AA2200 loaded to normal COALs.

 

[FightFireJay]

Xman,
Fantastic testing!

Regarding post # 232, comparison of 110gr TTSX and 110gr TSX, the poor performance of the TTSX got me thinking a bit. So I checked the Barnes website and sure enough, the TTSX bullet is labeled "270 Caliber" and the TSX bullet is labeled "6.8 mm". Almost like they were segregating the bullets by cartridge and not just caliber.

One quick email out to Barnes and the reply from Ryan Farr...

The TTSX will open up down to 2000 fps, and the TSX will open down to 1800 fps.

That certainly agrees with your testing and confirms that for 6.8 SPC usage (and in most cases of the new 270 AR wildcat) the 110gr TSX is a better bullet for terminal performance.

Thanks again for all your hard work!
J

 

[Xman]

Jay, thanks for adding that information. I've tested the TSX and TTSX across the caliber spectrum from .223 to .308 and the TSX has always out-expanded the same weight TTSX in the same caliber. This is probably why Remington chose the TSX for their Hog Hammer ammo line.

There is one other aspect to consider regarding why the 110 TTSX does better in the .270 Win than it does in the 6.8mm - twist rate. It doesn't affect the expansion of every bullet the same, but it is measurable with the .277/6.8mm TTSX bullets. The .270 Win is typically a 1:10 twist and the 6.8 is 1:11.25 plus the .270 launches the bullet at a higher velocity (3400 vs 2700 fps) resulting in a spin rate of 244,800 RPM to 172,800 RPM, respectively. The added centrifugal force helps the TTSX bullet expand to larger diameters.

I've just started testing the effects of twist rate. In the .223 where twist rates can vary from 1:7 to 1:11 or slower, the effect on bullet expansion can be dramatic. In the case of Hornady's new 55gr .223 GMX bullets, as much as 25% more when the bullet is shot from a 1:8 or faster compared to a 1:11. You can also see in the graph below that the 55gr GMX bullet became elastic just before it lost its pedals around 1100 ft-lbs of energy resulting in some amazing expansion with the faster twist rates.

 

[FightFireJay]

Forget the hogs, I feel like my brain just got hammered! I never seriously thought about twist rates affecting terminal performance, other than a quick look at and dismissal about spin rates stabilizing bullets in flesh (according to several sources who could do that math and proved it wouldn't stop a 5.56 from tumbling no matter what your barrel twist).

In retrospect, I shouldn't be too surprised... I was able to make some Hornady 55 gr SPSX bullets expand in mid air using my 1-8" barrel after they successfully shot in my 1-9" barrel.