LFP Comment Thread

[grayfox]

I put a grid overlay onto a copy/paste of the picture into my little graphics program. Now this is 600 wide by 975 tall grid, I'll call them pixels, they're not inches or mm, and I had to make a couple assumptions:
1. Measuring the band-gap (grooves) entails going from the outer edge of a band-cut, across both chamfers to the other outer edge.
2. The two bullets look to have the same linear length from ogive to start of the respective boat tail, so I'm assuming that.
Meaning the difference in bearing surface, if any, would be the delta of the band-gap sums.
For the 120 TTSX, I measured a total of the band-gaps (grooves) of 120 pixels, 40 pixels for each gap.
For the MKZ, I measured 100 pixels, well: 1 at 51 and the 2d at 47 so I rounded up slightly, conservatively.

Meaning to me the MKZ may have a bit more bearing surface. Of course the friction is also a function of the hardness + any lubricity of the two metal surfaces, which could be different in the 1 vs the other.
Both are solids not lead/copper so probably uniform hardness properties radially through a bullet's diameter.
So --- hard to say IME - maybe the MKZ is a bit longer of a bearing surface,
But Rick you had the real things not just a picture, so what I'm seeing could be less precise.

O, one more point - rather a question, since the MKZ gaps are further to the rear of the bullet, does that cause more initial friction for the first few microseconds for bullet travel vs the TTSX bands which allow some yielding "sooner" in bullet flight? I wonder but don't know.

Interesting.

[rickOshay]

Thanks gray fox. I agree its hard to measure these, especially where the bands start on the MKZ because they are rounded.

The ogive on the MKZ is much further back than the TTSX. In the picture, it is located at the point across from the middle of the third band on the TTSX. So your assumption in #2 is a bit off for the MKZ



Thats 270 pixels long compared to the 316 pixels for the TSX on my screen

Wish the manufacturer would chime in.

It would be interesting to see a pressure trace of these two as they travel down the barrel.

[grayfox]

Good observations. FWIW I'm not a particular fan of the Barnes's either... they're good bullets I'm sure and lots of shooters love them, but I couldn't get them to track for me, and all the reading I did of them needing barrels not fouled by other bullets to do well (I tend to look for 2 or 3 bullets per rifle), plus the higher cost, plus I can get the more traditional bullets Hornady, Sierra, and Nosler to do well... I've just not had the love for 'em.
Glad other guys like 'em tho.

[LRRPF52]

I put a grid overlay onto a copy/paste of the picture into my little graphics program. Now this is 600 wide by 975 tall grid, I'll call them pixels, they're not inches or mm, and I had to make a couple assumptions:
1. Measuring the band-gap (grooves) entails going from the outer edge of a band-cut, across both chamfers to the other outer edge.
2. The two bullets look to have the same linear length from ogive to start of the respective boat tail, so I'm assuming that.
Meaning the difference in bearing surface, if any, would be the delta of the band-gap sums.
For the 120 TTSX, I measured a total of the band-gaps (grooves) of 120 pixels, 40 pixels for each gap.
For the MKZ, I measured 100 pixels, well: 1 at 51 and the 2d at 47 so I rounded up slightly, conservatively.

Meaning to me the MKZ may have a bit more bearing surface. Of course the friction is also a function of the hardness + any lubricity of the two metal surfaces, which could be different in the 1 vs the other.
Both are solids not lead/copper so probably uniform hardness properties radially through a bullet's diameter.
So --- hard to say IME - maybe the MKZ is a bit longer of a bearing surface,
But Rick you had the real things not just a picture, so what I'm seeing could be less precise.

O, one more point - rather a question, since the MKZ gaps are further to the rear of the bullet, does that cause more initial friction for the first few microseconds for bullet travel vs the TTSX bands which allow some yielding "sooner" in bullet flight? I wonder but don't know.

Interesting.

That's where I'm leaning. This doesn't mean it's a bad bullet. Barnes and other solid bullet manufacturers used to use no relief bands at all. Some still don't have them. The start pressure considerations for a bullet without relief bands close to the ogive are going to be different than one like the TSX where the first relief band is within ~.080" of the ogive, effectively forming a short ring that is driven into the leade, followed by the space of the band where there is no additional resistance until the second ring is encountered.

The Barnes engineers said it took them years of experimentation working to try to reduce the start pressure with the older product line, when the answer was under their noses all along with cast bullet shaping. Even with the relief bands, start pressure is noticeably higher with a solid, and especially increased when you kiss the lands with long COL.

They said they've seen pressure spikes as much as 10ksi with the same load just with touching the lands.

The only time I've ever blown a primer with a hand load was with the GMX in .260 Remington. It blew the snot out of that primer, and I ceased shooting and pulled that load. Everything appeared to be in a reasonable load range, but nope, it was way overpressure.

These bullets need pressure-testing in a standardized pressure test breech by someone competent, who has calibrated the system meticulously. Barnes said it took them years of calibration and re-calibration, which they are always chasing. When they see people slap an RSI on their chamber and take a few readings, they know that person is not getting any valid readings unless they are building an initial library and calibrating the gauges over a long period of time.

That's why when I see the figure of 31.5gr of CFE being thrown out there to "safely" load under this bullet, I want to see some test data to support it, because 31.5gr of CFE under a 120gr TSX is way over the top for me, I won't even go near that and haven't in my load development with it. Things start getting crazy after 30.3gr of CFE223 under a 120gr TSX at 2.230" COL.

Notice the increase in speed:

120gr TSX, CFE223, 2.230" COL, Hornady 1x brass, CCI 450, 18" Lilja 3groove, 1/8 twist
30.0 2435 2424
30.3 2463 2497
30.6 2563

When you see 66-100fps jump with .3gr of charge weight, you know you're in a really bad place, and that's with a bullet that has the relief band right behind the origin of the ogive at the shank.

Another thing that may be in the MKZ's favor is that it appears to be softer with an advertised 1600fps expansion threshold, but even still, a solid resists being driven into the lands much more than a cup and core bullet. I've never seen a spike that high with a cup and core with CFE223, even when I pushed my initial pressure ladder with the 123gr AMAX waaaaaay past MAP just to see where it would depart. I was able to get the 123gr AMAX going so fast from a 16" barrel that it exceeded 24" velocities, but that doesn't mean it's anywhere near safe to produce that load.

If I had the inclination of other people who have just jumped into this discipline, I would rush off to the internet and yell, "I just got 2700fps from a 16" Grendel with 123gr AMAX! No pressure signs!" Insane velocity is your first pressure sign.

[rickOshay]

Another thing that may be in the MKZ's favor is that it appears to be softer with an advertised 1600fps expansion threshold....

Someone on this forum tested the expansion threshold of the MKZ and found it to be MUCH lower than the Barnes TTSX bullets, by >300 fps.

The TSX was designed for much higher velocities than the Grendel with an envelop of 2000 - 3000 fps. The new LFPs coming out, like the MKZ, are designed for lower velocities, from 1600 - 2600, fps that are much better suited for the Grendel.

[grayfox]

May not necessarily be softer, it could be because of the length and design of the petal grooves. Think I remember seeing that maybe in an other forum's discussion... they could be deeper than the "average bear" and look to be longer, plus skewed at an angle, instead of being parallel to the bullet's axis. What I don't recall is if they are designed to split off or to peel back... some guys did seem to be getting some decent results with them, the ones that reported, that is.

[rickOshay]

My understanding is that the metal composition determines the performance window which is limited to about 1000 fps. This is the range between the metal being soft enough to bend, and yet strong enough to hold together.

LFPs designed to be soft enough to open up at 1600 fps will come apart (petals break off) if you get much higher than 2600 fps. So it's a sliding scale for the velocity/range you want.

The metal composition is different between the 118 MKZ and the 105 MKZ. The 105 is harder so that is holds together a higher speeds.

The TSX was designed to hold together a 3000fps - mainly for the .308 case family of .264s

[grayfox]

I chased down an old thread on CBB performance and the pix and descriptions there showed them as the petals peeling back (as opposed to breaking off), for that caliber at tested velocities. So that answers that question. There was also mention of being made of "soft/er copper" (no values or compositions given), which is consistent with 52's and your statements... I'm not a metallurgy expert so will rely on you-all's observations for that.
Thanks!
Lead's days, unfortunately, may be numbered since the last USA smelter was forced to close a couple of years ago IIRC... so we definitely need some innovations and ways to keep accurate, inexpensive reloading components coming. That's what America is good at -- innovation.

edit: Not to be misunderstood - I like the regular cup/core lead/copper Hornady, Sierra, Nosler bullets we have right now, just fine!!! just sayin'.

[thedudeabides]

Does anyone have any numbers or load data for the Maker Trex bullets? I'd love to see what's realistic from the 110gr. from 16 and 18". I can't seem to find it anywhere and the website seems a bit incomplete.

[rickOshay]

Does anyone have any numbers or load data for the Maker Trex bullets? I'd love to see what's realistic from the 110gr. from 16 and 18". I can't seem to find it anywhere and the website seems a bit incomplete.

The good news and bad news with the 110gr TREX is that its the first 110 gr offering in LFPs. In fact, the whole range of weights from 100 to 120 has been largely ignored in the 6.5 caliber.

I'm very happy to see the 105, 107, 110 and 118 gr LFPs being made recently to fill this gap.

I have predicted a 2600 fps max from a 20" barrel for this projectile based on other data. I have recently confirmed this using CFE223 and achieved 2560fps with no excessive pressure signs on brass. I believe that higher velocities could be achieved with H335, TAC, or AA2520.

If you subtract 25fps per inch loss of barrel length, you should be in the 2500 to 2550 range.

Given this LFP opens up down to 1800 fps or less, that means you have a range out to about 350-400 yds depending on what the BC is for these LFPS.

Hope this helps.

[thedudeabides]

That does help, but still wondering also about the BC on those suckers? Trying to decide between these and the 105 mkz. Cbb saying 2750 from an 18" puts it out towards 450, even with a 2000fps min opening. Looking forward to more data on all the lfps and many thanks for all your efforts Rick!!!

[grayfox]

Dude, I think it would be wise to cross-validate any CBB-stated values with others on here that really understand the Grendel, like lrrp52, vascar2, bft etc. Every vendor has a slight, shall I say, leaning towards his or her own products that ought to be balanced with other, objective inputs. If they all agree then great!
Anyway, how much do you need to have at 450 and what are you shooting out there?

[thedudeabides]

Absolutely grayfox, couldn't agree more! Can't wait to see more posted results and writeups from the pros regarding the lfps. Looking for best lfp for elk specifically, and of course deer or anything else. I would like to think 400 to be max reasonable for elk, but you know how hunting goes and one should know real performance.

[grayfox]

I am hopefully elk-bound also, these long-range shooters on here know their stuff. I'll let them advise.
Good hunting.

[sneaky one]

I sent 105 GMX's to Richard small a few years back-- They were loaded to the original data sheet from AA for 110 Barnes solids..I just sent him a text--- I think 2580-2660 was the zone.

It was a safe soft load.

He just texted----- he's prepping for Hurricane Irma!

Someone - JASmith, got your ears on dude? Can you run a program on this 110.? Thanks.!

RS said he;d be on here asap.

[Makerbullets]

That does help, but still wondering also about the BC on those suckers? Trying to decide between these and the 105 mkz. Cbb saying 2750 from an 18" puts it out towards 450, even with a 2000fps min opening. Looking forward to more data on all the lfps and many thanks for all your efforts Rick!!!

The BC for the 110gr TREX is .45
the 85gr TREX is .37 and the 95gr REX is .31
Robert at CBB has the 105 BC.

Paul

[rickOshay]

Paul - Thank you very much for all your support.

The Summary thread has been updated with these data.
Lead Free Projectiles for the Grendel

[DJL2]

The 85 has a higher BC than the 95? Is that because the 85 is intended to be used with a "ballistic tip" and the 95 is not?

[rickOshay]

Got the 120 gr Peregrine Plains Master in. The design is interesting with the plunger and the long nose and low bearing surface.

Hopefully get some gel and load data soon.

[rickOshay]

The 110gr Lehigh Controlled Chaos has been added.

Man! When I started this back in January this year, I didn't know what I would be getting into. The number of 0.264 LFPs has expanded dramatically this year. Good year for the Grendel!

I had to break up the group photo because the number had become too big.