Mountain Molds 6 EXP

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Last Post 02 August 2016

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Paul Pollard posted this 16 June 2016

Mountain Molds sent a 6mm mold which arrived on Monday. The designation is 6 EXP and it is designed with the body of the Eagan MX2-243. The sharp pointed nose takes the place of the truncated cone of the Eagan. The intent of this exercise is to take the design of a good shooting bullet with a flat nose and determine if the sharp point nose makes a difference for wind drift while maintaining accuracy. The rifle is a 6ppc with a Shilen 1:14 twist barrel. According to most ballistic calculators, the Eagan bullet will not stabilize. Some weight is lost when going to the pointed nose bullet. Maybe with luck, we can stretch the pointed nose bullet a little more and gain some weight.

The overall length of two cavities is 0.800” and the center cavity is 0.815” long. These were cast of linotype and the shorter bullets weigh about 75 grains while the longer bullet weighed 77.5 grains. I started casting at 625Ã‚Â°F, but turned the heat down as it took quite a bit of time for the sprue to harden. I ended the session at 600Ã‚Â°F, but may try a little lower yet. For the first time with this mold, I didn't weigh and sort, just inspected for fill out and discarded unfilled bands or bases.

In order to size the pointy noses, I had to alter my gas check seater top punch. It had been flat on top for the Eagan flat nose. I found one for the LBT 65 grain which still had a 0.080” meplat. The first attempt was to insert a .177 pellet in the punch; after 8 bullets, the sharp nose poked through the lead and hit the flat part of the punch with a resulting flat on the bullet nose of about 0.050”. I drilled a small hole for the point and reinserted the lead pellet. This time it had enough cushion for the sharp point. The mold came with a top punch, which I put in the RCBS lubesizer along with a Lyman .244 die. This worked fine. Finally, for the taper/bump die, I swapped out the Eagan die for the LBT taper die. Also had to alter the top punch. I ran some through the sizing operation and checked fit and overall length with some dummy rounds. Everything looks very close to the Eagan sizes. One noticeable area was the nose is a little bigger on the 6 EXP at 0.239” and shows better engraving when chambered.

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mtngun posted this 02 August 2016

That's good info, Paul, and I agree that the Lyman #2 failure may be a hint that the 6exp needs a harder alloy.

That's the thing about cast bullets, there are so many more variables compared to store-bought jacketed bullets. It's a constant challenge to stay on top of it all.

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Paul Pollard posted this 02 August 2016

The 6Exp may not be getting a fair shake. With all the discussion about hardness testing, I took a look at my Eagan MX2 boxes of bullets. They were all made at least 4 months ago. They have had time to harden. But, they were also marked “Big Batch Lino #2". The 6Exp bullets were all cast with “Big Batch Lino #3". It turns out that testing the BB2 bullets on the LBT tester were around 22 BHN. Tested a few on the industrial hardness tester and it read 39 on the scale which equates to 22 or 23 BHN.

BB3 Lino samples tested 16 BHN on the LBT tester and on the industrial tester also showed about 16-18 BHN. I'm not worried about absolute readings. This shows that the 6Exp has been handicapped by a low BHN, especially after seeing the Lyman #2 results. Another 100 lb batch (BB Lino 4) may have a better “shot” at accuracy.

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mtngun posted this 01 August 2016

Thanks for the excellent data, Paul.

Yeah, it definitely preferred the Eagan. I wish we knew why. You wouldn't think that replacing the truncated cone with a short spitzer would make that much difference in accuracy.

Interesting that Lyman #2 missed the target, but .... I never did like Lyman #2. :D

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Paul Pollard posted this 01 August 2016

July 31, 2016.

Temperature, 71Ã‚Â°F to 84Ã‚Â°F. Humidity, 85% to 53%. Dew Point 67Ã‚Â°F. Wind 0-5 mph, variable direction. All targets shot at 200 yards.

The first box was loaded with 25 rounds of Batch#88 bullets, 6Exp from the rear cavity, 75 grain as cast. There were 21 rounds of Batch #76 MX2. These were to be a test of wind drift and drop. This didn't work at all. The Eagan bullets outshot the 6Exp by a wide margin. Without much wind, the MX2 bullets shot an aggregate of 1.025”. The last group was a 0.665” with 6 shots. The largest was 1.455. The five groups of 6Exp averaged 2.570”.

The center cavity 77 grain bullet was loaded with 32 clicks (17.8 gr) of H4198. These averaged 1.995 for 5 groups. The rear cavity averaged 2.107.

Also loaded were 25 rounds of Lyman #2 alloy cast from the rear cavity. These weighed 78.2 from the rear cavity. Evidently, the velocity is too much for this alloy. Out of the five groups, I could only find four. These averaged 3.783, with several shots off the paper.

All these were preloaded, so the only thing I played with was seating depth. This made a big difference by shrinking groups, just a little too late. Attached is a target which shows how much everything danced around. Hope you can decipher it.

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7-31-16 Sheet #3.jpeg

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mtngun posted this 21 July 2016

Thanks for the excellent range report, Paul. :)

It sounds like the pointy nose is reducing wind drift a little. With a sectional density of about 0.180 it's never going to be a long range missile, but striving for incremental improvement is an important part of benchrest shooting.

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Paul Pollard posted this 21 July 2016

July 19, 2016. Temperature 71Ã‚Â°F to 78Ã‚Â°F, humidity 78% to 71%. Wind 3-8 mph variable directions.

Shot the remaining 5 groups of MX2 80 grain bullets loaded with CCI 450 primers and 32 clicks of H4198. These averaged 2299 fps.

Five groups of the 6Exp 77 grains bullets with CCI 450 primers and 31 clicks of H4198 averaged 2308 fps.

I had thought that the CCI 450 primers would increase velocity more than the Federal 205 primers. With the 77 grain 6Exp bullets, 9 groups with Fed 205 primers, 31 clicks of H4198, these averaged 2308 fps, same as the CCI 450 primers.

With the velocity the same for the MX2 and 6 Exp, the drift and drop should be more meaningful. At 200 yards, the first target had wind coming from 3 o'clock. The MX2 bullets hit 2.250” more to the left and were about 1/2 inch lower. Group sizes were both about 2.25”.

When the wind shifted to 12 o'clock, it drove both bullets down and off the paper for several shots. The groups overlapped each other in a 3/4” wide band, with the pointed 6Exp hitting about 1/2” higher than the MX2. The attached photo shows the results.

Shooting 2 groups on each target seemed like a good idea, but the bullet holes are more nearly the same. The 31 clicks for the 77 grain 6Exp seems to cut the paper more cleanly than the 32 click load. Next time out, I'll use different target bulls for the different bullets.

There were 5 groups of MX2 bullets and these averaged 1.925”.

There were 15 groups of 6Exp bullets and these averaged 2.183”.

One group had an extreme spread of velocity of 142 and SD of 53. The powder may have hung in the measure on this one. Without this abnormal group, the average ES was 31 and SD was 12 for 19 groups.

In a strange twist, the lowest ES and SD was a group shot with 3 bullets from the front cavity and 2 from the rear cavity. There is about .3 grain difference between these cavities. The group size was 1.75 and had ES of 8 and SD of 4.

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CBA President

John Alexander posted this 05 July 2016

Paul, Excellent report and encouraging results. I may have to reconsider that old unfired, by me, 6 PPC rusting away in the back of the gun safe. John

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mtngun posted this 05 July 2016

Thanks again for the excellent data, Paul.

I'm not surprised that the EXP is more stable than its flat nose parent.

Lucas is lucky to have you as a mentor.

Does your PPC have a 2 oz trigger? Shot free recoil, or holding?

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Paul Pollard posted this 05 July 2016

July 4, 2016.

Temperature was 68 to 78 degrees, humidity 64% and wind about 8 mph.

The 100 yard targets were shot with the MM 6 Exp from cavity #1. These weighed 75.62 to 75.80 grains for a .18 grain spread. Ready to shoot, they weigh about 77 grains. For this testing, I decided to find a velocity where they became unstable. From previous testing the MX2 Eagan was unstable below 2130 fps. The range of testing started at 32 clicks H4198 and decreased until running out of primed cases at 26 clicks. The charge weights were from 17.7 grains down to 14.3 grains. Each click is roughly 1/2 grain. These were with Federal 205 blue box primers. The velocity started at 2335 fps and ended at 1983 fps. I couldn't see any tipping and accuracy remained reasonably good.

After struggling all day with a stiff bolt-lift Savage, and learning how to breech seat, 9 year old Lucas shot the last target with the 6 ppc. When he shot up the last bullet in that box, he asked if there were any more.

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7-4-16. 100Yd. MM vs MX2.jpeg

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mtngun posted this 05 July 2016

Sorry we got sidetracked on your thread, Paul.

That's great data, and 1.112” is not bad at 200 yards! I can only hope to do as well someday.

Glad you seem to be achieving your goal of less drift while maintaining the MX2's accuracy. :cool:

You're getting awesome results with linotype, but I'm wondering if you have ever tried a denser alloy like heat treated WW or similar? Dunno if accuracy would be equal to lino, but if it was, the denser alloy should have less wind drift. About 6% difference in density between WW and lino, so sectional density would also be 6% larger, and the BC for a G1 profile is proportional to sectional density. Just a thought.

Getting back to your nose dies -- if I understood you correctly, you believe accuracy is better with the MX2 nose die than with the tapered LBT die, perhaps because the 0.2385” nose allows the front band to engrave more when chambered ???? Or maybe the slight engraving of the .2385” nose is simply more consistent ???

Any idea what the original freebore & leade angle was in your PPC?

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Paul Pollard posted this 05 July 2016

This is an attempt to keep this thread from unraveling completely. July 4, 2016.

Today, I put up some targets at 200 yards. This test was not well planned, but offered some insight with the MX2 and the 6Exp. The attached target is marked up in pen and there are two groups of each bullet on the target with different aim points. The MX2 loads were CCI 450 primers and 32 clicks (17.7 gr) of H4198. These bullets weigh about 81.5 gr ready to shoot. Velocity on these was 2310 fps. The two groups averaged 1.915.

The 6 Exp loads were Fed 205 primers (blue box) and 32 clicks (17.7 gr) H4198. These weigh about 77 gr ready to shoot. These averaged 2335 fps and the average of the 2 groups was 1.112.

The crosshairs were held on the outer edge of the red scoring rings (200 yard 7 ring). I drew a vertical line on the target and measured each bullet hole from that line in inches. The wind was right-to-left and the numbers were negative numbers to the left. I averaged each set of measurements. The MX2 averaged 2.223 from the line and the 6Exp averaged 1.903. The difference was .320 more drift for the MX2. Two of the groups showed a 1.25 vertical difference on the target. The other aiming points were a little unclear (forgotten).

Next time out, more targets with more groups would give more information. It looks like the ballistic coefficient is better with the pointy bullet, however, the MX2 continues to shoot well, even at 200 yards. There was no evidence of tipping at 200 yards.

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7-4-16. 200Yd. MM vs MX..jpeg

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mtngun posted this 05 July 2016

frnkeore wrote: "I suspect we will begin to see progress in plain base scores as competitors begin using coated bullets."

I completely missed the above. Regarding coating, it will not occure in ASSRA or ISSA matches. Those groups have ruled it a “jacket” and can't be used. I don't believe CBA has had a discussion, regarding it's use or legality in matches.

FrankOn another thread, President John stated that coatings and paper patches were legal in PB category. Although as far as I know, the issue has not actually come up in competition thus far.

Coatings don't make the bullet more accurate but they seem to allow PB to run at the same velocity as GC and with equal accuracy. Depending on whether or not you believe that velocity matters at 200 yards.

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frnkeore posted this 04 July 2016

"I suspect we will begin to see progress in plain base scores as competitors begin using coated bullets."

Frank

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mtngun posted this 04 July 2016

The current 5-shot 100 yard record for PB is 0.1903". Sure, the PB shooter has to pray for ideal conditions and/or be very, very good at doping wind, but I don't doubt that the accuracy potential is there.

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frnkeore posted this 04 July 2016

Joe, I have yet to see or even hear about a machine rest used with a PB rifle, most all of them are SS, falling block types and almost all use a exposed hammer (lower AO strength & slower lock times). That doesn't really matter, because the UNR can use them also. Why do the higher end BR shooters use sleeved actions and as fast a lock time as they can get?

I believe what really matters is that the vast majority of PB, shoot breech seated. Unrestricted clases have yet to adopt that and I believe that their scores would improve, if they did so.

As to the velocity not making any difference, all I can say is “You gotta be kidding"!!!

To believe that, you have to believe that the laws of physics are wrong. It's all in the math Joe.

Frank

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joeb33050 posted this 04 July 2016

frnkeore wrote: "and the rules favor them, somewhat."

Joe, can you explain the above statement, in more detail.

The rules are the same as UNR/UNP but, PB can't run as fast as the GC guy's and almost, if not all PB rifles, have slower lock times. I see that as a disadvantage.

FrankSee 5.9(c); UNR and PB can use machine rests. (Not UNP, as I read.) Note “somewhat". In a machine rest, lock time doesn't matter. And MV seems not to matter much in competition. We don't know WHAT matters, we could find out by testing/experimenting PBB vs. gas checked. This lack of testing/experimenting, in my mind, goes a long way toward explaining the almost complete lack of improvement in CB accuracy at the NM, for 24 years. We won't argue about this. joe b.

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frnkeore posted this 03 July 2016

"and the rules favor them, somewhat."

Joe, can you explain the above statement, in more detail.

The rules are the same as UNR/UNP but, PB can't run as fast as the GC guy's and almost, if not all PB rifles, have slower lock times. I see that as a disadvantage.

Frank

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joeb33050 posted this 03 July 2016

mtngun wrote: Thanks for the data, Joe and Paul That's about what I thought.

What about the plain base category? 1 MOA to be competitive? I suspect we will begin to see progress in plain base scores as competitors begin using coated bullets. The PBB guys have made some progress, and are a threat to the UNR and HVY guys, depending on who attends. They've got this down pat, and the rules favor them, somewhat. If they get much better, they'll demolish the .5” threshold. I was at the match where the first 200 yard 250 in history was shot, back in 198?. The CT Dentist, whose name escapes me. Lately, 250s are shot all over the place, sometimes several a day by one guy. Look at the charts to see progress or lack. Jerry/Gerry Ventura is his name, at the WNYSS, Alabama Hunt Club. Now where are my glasses?

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mtngun posted this 03 July 2016

Thanks for the data, Joe and Paul That's about what I thought.

What about the plain base category? 1 MOA to be competitive? I suspect we will begin to see progress in plain base scores as competitors begin using coated bullets.