6x45 now a coyote rifle

[madsenshooter]

Or, what a difference one thousandth can make! I have an AR15 I had built around a 6mm Obermeyer barrel that I got off gunbroker for $10. I also had the cherry for the Eagan MX2-243. I had BaBore make me a mold with the cherry. Try as I might, I couldn't get decent accuracy above 1600fps. The boreriding nose measured .235", the bore of the Obermeyer .233", measured with pins. Should've been perfect, according to conventional theory. But the Obermeyer isn't a conventional barrel, it has 5R rifling, and a fast twist. I haven't measured the twist as of yet, but I'm fairly certain it's 1/8.

After a lot of thought, I came to the realization that a bore with an odd number of grooves has no land directly across from the other to offer support for the boreriding nose as the boolit passes down the bore. Wondering if this could be the problem, I decided to enlarge the nose of the Eagan. I only enlarged it .001-.002. .001 at the top of the ogive, .002 at the edge of the top driving band. I drilled down through the meplat of a bullet while it was clamped in the mold, then inserted a tiny tap. I then applied Wheeler Engineering 340 grit borelapping compound and gave the bullet a short spin. I used a couple bullets as the lapping compound ate the softer alloy faster than it did the aluminum of the mold. That's a good thing, keeps you from taking off too much at once.

Today, I got to give the fatter nosed Eagan its first trial, and it appears that I'm on to something here. Pictured are the two ten shot groups, each around an inch and half at a velocity of 2250fps. They're equal to what was previously my best with the Eagan at around 1600fps. I've added some tin to my alloy and have some cast that measure about .0005 more than these ones. They should tighten the groups a bit more, if my theory is correct. If they do, I've a couple more thousandths I can take off the mold to get them at their utmost.

My load was a real odd one, for the advanced reloader only, a duplex of 4.5gr Blue Dot under 21.3gr WC860. Groups seemed to get tighter as the barrel got dirtier, I'll take that as an indication that the nose needs to be larger.

I think that the Eagan was poorly designed as a borerider. It has very little bearing surface in its two little bands and the gascheck. In the 5R rifling, in my way of seeing things, since there's no opposing land for the boolit to ride, I was getting a wobble. I think a lot of rifles with an odd number of grooves get this wobble, but most have enough bearing surface on the rear to overcome it before the boolit exits the muzzle. Oh, that bullet hole in the upper right of the second picture is 30 caliber, I was playing with my parkerized Krag today too.

I think that a borerider will work best in a rifle with an odd number of lands and grooves when it is the same diameter as the dimension from the top of a land, to the bottom of the groove directly across from it. In my case, that's about .240", so only slightly smaller than the driving bands.

[madsenshooter]

I decided to skip the 1/2 thousandth larger bullets and went with some that cast a full thousandth larger. They were a little lighter due do a change in alloy, thus a little faster. 2307fps Avg. The group isn't all that impressive until one takes into consideration the fact that about half of what I shot had a considerable amount of runout. Got that problem fixed with an M-die. I'm going to reduce the main charge a bit, get back down to 2200-2250fps. It'll be my load for the CBA regional benchrest matches, Fri and Sat. I forgot to add, with the increase in diameter of the ogive, I can seat a little deeper and still be in the rifling, I'm now at max magazine length with a metal magazine, the volume of gas produced should cycle the action, though I've not tried it yet. Now all I need is a pack of coyotes!

[dk17hmr]

Nice....I run 55gr Nosler ballistic tips in my 6x45 for general hunting and 70gr SMK's for pelt hunting......Never really thought about shooting cast in it.

[303Guy]

If the bore-rider nose is large than bore diameter and it chambers then the throat end might be larger bore than the muzzle end. Size those boolits to bore-ride in the throat on chambering and let the bore size the boolits on firing.

A trick to try is to coat the bore-ride nose with some thick and fairly firm lube to act as a 'grease patch'.

Something like this. This is melted on.


Encouraging results.

[madsenshooter]

I was wondering if you Enfield shooters had a similar problem. After the regionals, I'm going to continue enlarging the mold until I get its best. Got a couple thousandths to go, but no time left before the event.

[madsenshooter]

Got the regionals over with. For the most part the rifle/boolit combination worked well. Not a benchrest rifle, but the combo will hold a coyote head out to 200yd. Further work will be done on the mold. In as much as the base of the bullet is already slightly below the neck/shoulder junction with the forepart of the nose measuring .237, I'm going to try to limit any increase in the diameter of the borerider to the rear, making the bullet a bit more tapered vs the nearly parallel sides that it now has. Presently, it is still a 1.5 moa combination, though 1.5 moa at 2300fps sure beats the same at 1600fps! As said gunwriter Craig Boddington, "One inch accuracy ain't good enough". It'll take more than that to be competitive with those benchrest shooters! Will keep those of you who are interested updated as the experiment continues. Maybe my coyote rifle will become a benchrest rifle before all is over.

[Three44s]

madsenshooter,

Come out to my neck of the sage brush ......... I've got coyotes a plenty!!


Nice work BTW!!!


Three 44s

[madsenshooter]

Thank you, it's still a work in progress, as they say. We've got plenty of deer eating coyotes in SE Ohio. They're interbred with husky type dogs and eastern wolves, and they're huge compared to the western variety. A rich fellow in Toledo left the state of Ohio enough money to buy up 6000 acres of woodland that surrounds my hometown as a wildlife area, and the coyotes have found heaven on earth! They're big enough that I think I may need a 30 caliber, but I'm going to give this 6mm a try before getting the Garand out. I'm going to the range today to check function of the AR with this duplex load. Anyone who cares to try the load, start low with your booster and work up. This would make for some cheap loading with 50BMG powders going for $49/8lb.

Update: Yesterday I got out to the range, as presently loaded, with 20.5gr 860 and 4.5 gr of Blue Dot, the load will not quite cycle the action. However, I know that I can increase the 860 .8gr and have little effect on velocity. I also know that there is room for more yet, and that for those who might wish to use this inexpensive powder in a .223, I know that the cylinder of a .223, meaning the bore, has a much lower volume than a 6mm bore and the load, worked up, should cycle them with ease, even a rifle length gas system. Here's a pic of the group shot yesterday. The barrel hadn't been cleaned since the second day of the regionals, so is over 100 rounds dirty. I added this pic to show, it does shoot a consistent 1.8". Yes there are 10 rounds in the group. I added this pic because someone was trying to say that I was using the pic above that I shot with my runout ammo as an excuse. It wasn't an excuse, just a statement of fact. It seems there's a few people on this board who wish to call people liars because they can't duplicate what others have accomplished, for whatever reason. To those I say, "Up yours buddy, your opinions matter naught to me!" No doubt they'll try to say I shot this at less than 100yds. As stated, I'll continue this endeavor. I think it will get better yet, and if doesn't, I'll have had some fun and will have learned some lessons by trying. If I'd have followed the advice of others, I'd have bought a slower twist, conventional rifled barrel, but how does one beat a $10 Obermeyer. By the way, there was a 6mm shooter at the regionals, he had encountered the same problems with the Eagan, moreso than I as he was using barrels with a larger bore diameter than my Obermeyer. Oh, forgot to mention, to quiet some who wanna know, I did measure my twist rate, and it is 1/8. In proportion to bullet diameter, that would equal a 1/10.14 twist, .308 barrel.

[madsenshooter]

I feel I now have the mold lapped out as far as it is safe to go. The nose now mics .237" at the beginning of the ogive, and .2383" just forward of the top driving band. This is at 90 degrees to the parting line. I don't think I can go anymore for the same points on said parting line measure .239" and .2413". The combination of BaBore's venting system and the high Sn alloy I use makes a substantial parting line. Not so big I guess, only .001 tall on each side, but enough to fill the .240" bore measurement that I had thought needed filled. Any larger and I'll be sizing a lot of that parting line.

Since I experienced some failures to function with the duplex load, I installed a Wolff reduced rate buffer spring. Should have gone directly back to the duplex, but on a whim tried a slightly different load. That was 22.8gr of DP85, an Accurate surplus ball powder that is about 4350 speed, with .3cc of Puf-Lon as filler. Ballistics were great and the rifle functioned. Avg of 2186fps, ES of 29, SD of 8.0. Group was nice, had I been shooting for score it would have been a 97-3x! The two 9s out to the right were me. The rifle had recoiled back in my rest away from my recently installed recoil stop (aka sling swivel), and I didn't notice. I shot the two out to the right, noticed, set the rifle back to the stop in the cradle and went back to hitting in the black.

It quickly became obvious that the Puf-Lon was not the way to go however as it blew back into the chamber when a round was extracted and caused difficult chambering of subsequent rounds, meaning I had to use the forward assist a couple times. It would be a good load for shooting with the gas system off, as in CBA benchrest competition though.

RPM of the bullets would have been an average of 196,740! In the future, I'll go back to working with the duplex load.

[Larry Gibson]

Madsneshooter

Congradulations, you have accomplished with your 8" twist 6x47 what I accomplished with the 6.5 Swede with its 7.8" twist; about 2 moa at under 2200 fps at around 195,000 RPM +/-.

Larry Gibson

[madsenshooter]

Thanks Larry! Actually, that's 1.5-1.6" anyway you stretch the caliper. Error as indicated, was more a matter of my shoddy benchrest technique than the load. (Front rest is a car jack with a U cut wooden block on top for forearm support). Maybe I should use one of the lead sleds available at the club. More development to come, to be a hunting rifle, I need full and reliable function. To be a benchrest rifle that'll compete with the fellows at Wastenaw I'll need a lot more of them in that red circle.

[madsenshooter]

In post #9 I'd said that I thought the Puf-Lon blew back into the chamber. It wasn't the Puf-Lon, it was unburned DP85. So I thought I'd try a faster powder, both with and without the filler. 21.5gr of 4895 w/o filler got me an avg of 2256, ES of 102, and SD of 31. 20gr w/Puf-Lon gave me an avg of 2218, an ES of 58 and a SD of 19.3, so the Puf-Lon reduced the ES and SD substantially. Nothing fell back into the chamber with either load. I'd hoped for around 2100fps with the lower load, I know the sweet spot's down there close. I did get full function with both loads, so I'll drop it down to 19gr w/Puf-Lon and see if there's any improvement. The faster load, w/o filler was the normal 1.5", the slower load gave me a 2.5" group. Swede Nelson is going to lend a helping hand though. He'll be doing a run of the pictured 6mm bullet while he's doing the 22 cal version, but that won't be until Feb. I think the taper is just what I need for more "wedge factor" in the 5 groove bore. That .240 second band should quickly seal the throat along with the bore dimension I said needed filled, and the shorter OAL should give me a bit more magazine space. In the meantime, I'll keep trying to find the spot with what I have here. I might even go back to the DP85, but with a magnum primer. http://castboolits.gunloads.com/showthread.php?t=124042

[madsenshooter]

Today we had a rare no wind day here in Northern Indiana. Though I got back to the duplex yesterday, it's a hunting and very cheap plinking round. I did change the kicker to about 2.6gr of 10B101 to make it even cheaper. But that was yesterday....Back to today. My coyote rifle is almost a benchrest rifle with a load of 14.2gr of SPP210, a Swiss made 4198 clone. Shot a nice 1.3"x1.1", 10 shot,100yd group under the no wind conditions. Wish everyday could be like today! I shot this right out of a clean barrel with no fouling shots, so I'll probably make like the benchresters and clean every chance I get come Saturday. Hey Larry, you suppose maybe the two outside and top and bottom shots are the edges of the helix? Note the radial dispersion. Maybe I ought to try going down a few tenths more? Avg velocity was 2088, ES33, SD5.

http://castboolits.gunloads.com/imagehosting/thum_12364e4ab28b49a82.jpg[/img][/url]

[Larry Gibson]

madsenshooter

Hey Larry, you suppose maybe the two outside and top and bottom shots are the edges of the helix? Note the radial dispersion.

Could be but the group is small enough that it could just be the random dispersion within the cone of fire. Only way to know is to load up 20 rounds and fire a 10 shot group at 100 yards and follow it with a 10 shot group at 200 yards. If the group dispersion is linear the load is good and this group is within the cone of fire. If the group is non linear then the "radial dispersion" shots are probably above the RPm threshold for that load and componants. Contrary to what DrB wanted as to "predictability" there just isn't any way to know ithout testing as mentioned. Looks like your getting a pretty good load though but only testing for non linear group dispersion will give you the correct answer. Keep up the good HV load development work.

Larry Gibson

[madsenshooter]

I'll be doing some 100 and 200yd testing in a CBA match tmrw. I think things are about as good as they're going to get with this bullet and 5 groove rifling. I can't wait to get the NOE bullet that will better fill the bore! Until I get it, I think a "cone of fire" is the best I'm going to get. In my way of seeing things I'm getting a wobble that starts in the barrel and continues in varying degrees to the target. CBA rules would put my 6x45 in the Heavy or Unrestricted class, I can't compete against those heavy 30cal rifles and bullets, so I'm going to get a 5.56 upper to use in the Military or Hunter class, but will continue with this experiment. The 6x45 will continue to be my coyote shooter though.

[madsenshooter]

Yesterday's match didn't go so well, but not as bad as it has been in the past. I used a different brand of cases for the match, and the load shot nowhere near as good as it did in the bottom group shown. 200 yard groups were not linear, meaning not simply a doubling of the 100yd groups. There was no wind to contend with so that wasn't the problem at all. To me, it's as if some of the bullets ride the lands, and some chose not to, despite my best efforts at keeping things aligned. I guess I got lucky in the group above and ten in a row chose to ride the lands. Just to see if it helps, I am oven heat treating some my bullets, all the while anxiously awaiting the bullet from Swede that will fill my bore.

[madsenshooter]

I've been playing with heat treating my babbitt bullets, minimizing the amount of lube I use (concocted something I call LLAMMO, LLA thinned with mineral spirits and Marvel Mystery Oil), and trying different powders. I apply the LLAMMO with a Q-Tip. Went to the range today and I'm pretty pleased with the results. Load was 22.2gr Russian 4895 (burns about Varget speed). Load needs more work, AV was 2353fps but SD and ES were high. Case necks were somewhat sooty too. The high left flier was a round that the neck split on when I loaded the boolit, I went ahead and shot it rather than pull it down. There's 11 shots there, squares are .950". 211,770 RPM, not bad for a beginner! EDIT: A couple days later I tried some loads using DP85, an Accurate powder once sold as surplus. It burns about 4350 speed. Velocity was increased to 2455fps and accuracy increased to 1" by orienting the bullets all the same way in the magazine (single loading). I also tried 28gr, but pressure was too high. That resulted in lead being blown back onto the neck of the case, velocity was 2555fps, and accuracy still wasn't bad, a 2x2 square.

[madsenshooter]

It was sunny and nice for a January day here in IN. So I took a trip to the public range that's about 20 miles from home. I had some left over loads from the last cast boolit match of last year, enough to shoot a couple groups. These were loaded with 26.5gr of DP85 and lubed with the LLAMMO mix I came up with, driving bands only, with a q-tip. When you're trying to grip rifling that's only .002 tall and rounded, standard lubing practices don't work well. Bullets were cast of a 23BHN babbitt, then further heat treated to exactly what BHN I don't know, harder. Velocity around 2450fps. Group is 1.3"x1.5" at 100 yds, RPM out of the 8" twist, 220500.

[Larry Gibson]

Very good, be interesting to know how hard (BHN) those heat treated bullets came out? They are obviously holding up very well to the accelleration of that load. How well does that rifle shoot jacketed bullets at the same velocity?

Larry Gibson

[madsenshooter]

Yea, saw that hard to look through little scope the other day somewhere, but I've shot up all the boolits Larry. Baked them 3hrs at 425. I found a way online to eliminate that little scope, but can't find my way back to it. Just snap a pic of the indent, measure in pixels, then convert pixels to inches. I'll post more about that when I find my way back to it. Did I ever mention my dad has alzheimers? I'm getting close to the age where it first hit him. Jacketed bullets, a bit faster:



Old Boots knows his stuff!