Mountain Molds 6 EXP

  • 2.2K Views
  • Last Post 02 August 2016
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 625°F, but turned the heat down as it took quite a bit of time for the sprue to harden. I ended the session at 600°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.

Attached Files

Order By: Standard | Newest | Votes
onondaga posted this 16 June 2016

No pictures? No mold!

Attached Files

Paul Pollard posted this 16 June 2016

Here's half a mold, showing the cavities. The middle cavity is the 77.5 grain at 0.815” long. The outboard cavities are the 75 grain at 0.800” long, same length as the Eagan MX2. 

Attached Files

Paul Pollard posted this 16 June 2016

Two dummy rounds were loaded to check for chamber fit. The one on the left is the 75 grain at 2.210 OAL. The front band is sized the same as the Eagan MX2 and is loaded to the same OAL. The one on the right is the 77.5 grain with OAL at 2.235. Because the bullet is longer, it is loaded longer. The front band on it also fits the same. The nose engraves lightly. It actually is slightly larger diameter nose than the Eagan. Both these bullets show full engraving on the nose; the Eagan only shows contact points at the nose/ogive junction.  It's hard to see, but there are light engraving marks on the nose and the first band.

 If you check mtngun's 6BR thread, you can see photos with lengths which match up with my finished sizes also. His photos are much better than mine.

Attached Files

onondaga posted this 16 June 2016

http://www.castbulletassoc.org/view_user.php?id=216>Paul Pollard

Thanks for the pictures! I hope you do well with the bullets.

Gary

Attached Files

Loren Barber posted this 17 June 2016

Paul,You are one step away from fame. I will be very interested in your accuracy results.  I have a 6 PPC bench rest rifle with a 14 twist Hart barrel.  Someday, I would really like to try some cast bullets in my rifle.  Please keep me informed. Maybe I'll see you in KC.Loren Barber

Attached Files

Paul Pollard posted this 20 June 2016

Saturday, June 18, 2016.

Shot the Mountain Molds 6 EXP in 75 grain and 77.5 grains. Accuracy seemed so-so, but the bullets seemed stable. The pointed noses tear the paper, making it difficult to determine if there is any tipping. The Eagan flat point punches out nice holes without tearing. The only powder used was H4198 with CCI450 primers. Cases were Lapua 220 Russian. Lube was Voodoo Red. One new thing for me was Gator gas checks. I used up the last of the Hornady gas checks on the Eagan bullets cast over the winter. Shilen barrel, 1:14 twist, 6ppc. The wind was only about 5 mph which was not the cause of the mediocre groups. Temperature was 85°F to 88°F and humidity started at 35% at noon and dropped to 28% by 3:00 pm.

The 75 grain cavities were shot first with varying powder charges of H4198. I tried a few thousandths variation in seating depth. These averaged 1.207 for 10 groups of 5 shots.

Next was the 77.5 grain with a few different powder charges and mostly the same seating depth. After smoothing the bullet holes, I couldn't see any tipping with this bullet either. There was one group shot with 30 clicks of powder and it may have been a little slow to stabilize this bullet. This was the largest group with this bullet. The average was 1.269 for 9 groups of 5 shots.

For comparison, I shot some Eagan bullets loaded with 32 clicks H4198 all at 2.205 seating depth. These also had Hornady gas checks. During these groups I had a primer misfire. This was on shot #2 and after poking out the bullet and blowing out spilled powder, shot #3 went way low. This opened the group to 2.100 for 4 shots. Ignoring this goofy group, the average of five 5-shot groups was .983.

None of the bullets showed stellar accuracy (even my old stand by). I'll try a bit better casting techniques and see if the weights will be a little closer. It looks like the bullets are stable, even the .835 long 77.5 grain one. 

Attached Files

OU812 posted this 20 June 2016

I know I sound like a broken record, but it would be interesting to see what softer and heavier 20-1 alloy and Titegroup powder would do in that rifle. Maybe even Hardball alloy (50 percent linotype, 50 percent pure lead).

Attached Files

Paul Pollard posted this 21 June 2016

It would be interesting to try 2 or 3 different alloys. However, I'm still trying to figure out how to cast good bullets in 3 cavities at one time. I've been using a single cavity mold exclusively for 8 years. Yesterday's casting session of linotype (again) gave me about 300 bullets. Scrap rate was about 20%. With 90°F ambient temperature, the sprue took forever to harden. Turning the pot temperature down was not a good idea. Complete fill out became worse. 

For the casting, I used a one pound Rowell ladle to get plenty of metal into the mold. I haven't run the numbers for the weights yet, but I did weigh each bullet and charted it on paper. It's not in the spreadsheet yet. As mtngun predicted, the front cavity weighs a bit more than the rear cavity.

For these bullets I'll be using Hornady gas checks again. I'm also trying different sizing dies, trying to get what works best. I may go back to sizing just the gas check in the Lyman die, then run the bullet into the taper/bump die for the final size. This tends to close the open end of the gas check a little better.

Attached Files

OU812 posted this 21 June 2016

You need a Lyman or RCBS ladle. Holding the tapered spout against tapered sprue plate opening is a form of pressure casting, just at a lower pressure. I have always cast hot...this gives me best fillout of bullet.

Bottom pour pots are trickier to learn, but work just as good as ladle casting. Flow rate adjustment is most important and changes as level drops...lower level equals lower pressure.

No two molds or alloys cast exactly the same, so adjustments must be made. Sometimes it can be difficult to find sweat spot.

...

Attached Files

45 2.1 posted this 21 June 2016

OU812 wrote: You need a Lyman or RCBS ladle. Holding the tapered spout against tapered sprue plate opening is a form of pressure casting, just at a lower pressure. I have always cast hot...this gives me best fillout of bullet.

Bottom pour pots are trickier to learn, but work just as good as ladle casting. Flow rate adjustment is most important and changes as level drops...lower level equals lower pressure.

No two molds or alloys cast exactly the same, so adjustments must be made. Sometimes it can be difficult to find sweat spot.

...
Stay with the Rowell ladle Paul..................... Everyone should try the methods for themselves to see just which method delivers the best results as to uniformity in weight and as cast diameter. Weigh all the bullets cast via each method and plot the distribution curve. Bottom pour versus Lyman/RCBS ladle versus Rowell ladle. Then see what happens on the target!

Attached Files

mtngun posted this 22 June 2016

Thanks for the detailed report, Paul.

BTW I had no problems getting good fill with a drilled out (#21) RCBS ladle and linotype at 715F.     I'm sure the 3-cav does run hotter than your 1-cav.     I don't want to second guess your casting style since you obviously have plenty of experience, but reading in between the lines it sounds like your lead thermometer is out of calibration ???

I don't know why the MX2-EXP would shoot any different than your MX2, since the part that is in contact with the barrel is very nearly the same.   But my 6BR did not like the MX2-EXP's at all.  :(    If it is not an accurate design then we go back to the drawing board.   

I've been using Gator checks for the 6mm and they work fine.  I don't have any Hornady checks to compare them to.   For some calibers Gators are identical to Hornadys, while for other calibers there is a slight difference in thickness.

Attached Files

mtngun posted this 22 June 2016

Paul Pollard wrote: The nose engraves lightly. It actually is slightly larger diameter nose than the Eagan. Both these bullets show full engraving on the nose; the Eagan only shows contact points at the nose/ogive junction.   You would think that, to the extent that it made any difference, the increased engraving would improve accuracy.    But I can imagine one way that increased engraving might actually hurt accuracy.     I'll test the theory in my barrel when time allows.

Attached Files

Loren Barber posted this 25 June 2016

Paul,Do you have an estimate of the velocity of your loads?Loren Barber

Attached Files

Paul Pollard posted this 25 June 2016

Loren, 32 clicks (17.7 grains) of H4198 or LT30 will give about 2200 fps with Fed 205m primers. That's with the 80 gr bullet. CCI450 primers give about 2300 fps, I think. I need to recheck. LT32 will need one more grain to equal that velocity.

With the 75 gr Mountain Molds bullet, CCI450, 17.7 gr H4198, velocity was 2350 fps; with the 77.7 gr, it was 2330 fps.

Attached Files

OU812 posted this 26 June 2016

NOE may be working on a scaled up version of John Alexander's 223 caliber 227-80 bullet. I requested to close up the gap between gas check and first band. My theory is hydraulic pressure caused by excess lube in this area is causing gas checks to pop off when exiting barrel  (occasional flyer or flyers). He would also shorten bore ride length slightly. This bullet would work perfectly in 6mmPPC, 6mmBR , 30 BR rifles without throating. Any other ideas before going into production?

Attached Files

Paul Pollard posted this 26 June 2016

Mtngun wrote, “You would think that, to the extent that it made any difference, the increased engraving would improve accuracy.    But I can imagine one way that increased engraving might actually hurt accuracy" I looked more closely at my taper dies. The MX2 die which was using a flat push out pin sized the nose at 0.2385. The LBT die tapered the nose 0.2385 up to 0.2405 in front of the front band. After sizing 2 of each die, I made up 2 dummy rounds of each. When chambering dummy rounds, the LBT-sized ones were tight chambering and one pulled the bullet when extracting. The MX2-sized ones chambered easily and extracted without trouble. The LBT die may be sizing the nose too big and holding the bullet's tapered front band away from the taper in the throat.

Attached is a really rough sketch of the nose sizes.

Attached Files

Paul Pollard posted this 29 June 2016

June 28, 2016.

Re-prepped the 75 grain bullets. Resized these in the MX2 taper die which sized the nose to 0.2385 for the full nose length, as opposed to the 0.2385-to-0.2405 taper of the LBT taper die. Hornady annealed gas checks. Tumble lube. These bullets finished at 0.814 long x 0.2442 diameter at the base band and gas check. The front band is tapered from 0.2435 to 0.2425, as near as I can measure. This should be the 3° taper included angle.

The target is marked up to show clicks of H4198. 30 clicks is about 16.5 grains and 32 clicks is about 17.8 grains. The measure will usually throw in a .3 grain spread, and it doesn't seem to make too much difference. The one thing I noticed about this bullet was that it was predictable. When a shot went out, then a glance at the wind flags would confirm that I wasn't paying attention.

So far, I can't tell if there is less wind drift with the pointy bullet vs the flat point. This was one of those days when things shot well. The 7 group agg was 0.643. Still needs some fiddling. The 31 click load looks like it would work better with the 75 gr bullet vs the 80 gr Eagan.

Attached Files

mtngun posted this 29 June 2016

Thanks for your report, Paul.   I admire your attention to detail and willingness to try different things. :)

Dunno what the BC of the Eagan bullet is, but the EXP is pretty close to a G1 form so I figure its BC will be the same as its sectional density, about 0.200.   So perhaps the EXP drifts less than the Eagan but even with a pointy nose the BC is still nothing to brag about.

If I ever get into CBA competition I may be inclined to go with a slow twist 30BR or 30PPC.   18” twist can stabilize up to 150 gr. spitzer (using reclaimed shot),  16” twist up to 165 gr..    That should drift less than a 6mm 80 gr. yet with a 16” - 18” twist could be just as accurate as your 14” twist 6PPC if not more so.   Recoil would be the only downside.

What kind of accuracy do you need to be competitive?    Has your PPC barrel lost accuracy with age?   

Attached Files

OU812 posted this 30 June 2016

That's it !!! Hornaday “annealed” gas checks

Verygood shooting Paul

Attached Files

Paul Pollard posted this 30 June 2016

Competitive accuracy in unrestricted rifle class is .500 and under. A couple times the 5 shot agg at 100 yds was won with .330 to .350.

If there any 75 grain bullets from the previous casting with Gator checks, I'll resize those in the MX2 die. That seemed to be the key to accuracy with any of these bullets.

Attached Files

OU812 posted this 30 June 2016

How do you anneal your gas checks? I have done this , but was wondering of a better way.

The Gator checks have a more rounded base than the Hornaday. My tests have shown Hornadays work better as far as accuracy goes. I am probably wrong.

Attached Files

mtngun posted this 30 June 2016

OU812 wrote: My tests have shown Hornadays work better as far as accuracy goes. I am probably wrong.I give you credit for being humble, OU812.  :D  :D  :D

Attached Files

Paul Pollard posted this 03 July 2016

Annealing gas checks.

A 2 quart sauce pan with a lid. Put 1000 checks in the pan and spread evenly. Put pan on hot plate set a the highest setting. Let cook for at least 30 minutes. They will turn black.

 At the end of that time or longer, I add vinegar to the pan. Let this come to a simmer or boil. This will knock the black flakes off. Pour off the vinegar into a container to re-use. Pour the gas checks into a metal strainer and wash with a garden hose and sprayer to get all the remaining crud off the gas checks. Dry thoroughly in the sun or with a heat gun.

Attached Files

joeb33050 posted this 03 July 2016

mtngun wrote:

What kind of accuracy do you need to be competitive?   CBA NATIONAL MATCH DATA , 1992-2015, UNRESTRICTED CLASS, 4 5-SHOT 100 YARD AVERAGES.

15 AVERAGES <.501" AVERAGE WINNING AVERAGE = .540" <.501 WINNING AVERAGE 12 YEARS OUT OF 24

OF MATCH ENTRANTS TOTAL  146

15/146 = 10%

THERE'S NO INDICATION THAT GROUPS GOT SMALLER IN 24 YEARS.

LUCK/CONDITIONS HAD A BIG PART IN VARIATION.

I'VE SUGGESTED THAT .5” IS THE CB THRESHOLD.  

Attached Files

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.

Attached Files

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?

Attached Files

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

Attached Files

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.

Attached Files

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

Attached Files

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.

Attached Files

frnkeore posted this 04 July 2016

"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.

Frank

Attached Files

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.

Attached Files

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.

Attached Files

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?  

Attached Files

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. 

Attached Files

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?

Attached Files

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

Attached Files

Paul Pollard posted this 21 July 2016

July 19, 2016. Temperature 71°F to 78°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.

Attached Files

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.     

Attached Files

Paul Pollard posted this 01 August 2016

July 31, 2016.

Temperature, 71°F to 84°F. Humidity, 85% to 53%. Dew Point 67°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.

Attached Files

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

Attached Files

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.

Attached Files

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.

Attached Files

Categories
Search
Popular Tags
This Weeks High Earners
Hot Topics
Close