30 BR

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Re: 30 BR

Postby mtngun » Thu Aug 04, 2016 7:56 pm

Shooting was interrupted this evening.
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Re: 30 BR

Postby mtngun » Fri Aug 05, 2016 8:19 pm

OK, continuing to experiment with different powders. Groups are numbered in the order which they were shot.

#1 & #2: still no joy with the 147 gr. GC so I am giving up on it for the time being.

#3 - #8: various tweaks with LT30 and the 120 gr. GC, . LT30 showed some potential but couldn't quite get its act together. Average for all six LT30 groups was 1.43".

#9 - #12: LT32 and the 120 gr. GC.. Average for all four LT32 groups was 1.31".
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Note that since the July 24 post, I have tweaked the nose die and the seating depth for the 120 gr. bullet, so comparisons to the July 24 results are not completely apples to apples. On July 24 the bullet was seated such that only 3/4 of the gas check was inside the case -- that wasn't very reliable even by benchrest standards -- so today's loads nose-sized the bullet less and seated a little deeper for better reliability. The deeper seating may hurt accuracy slightly but if so that is a necessary tradeoff for reliable functioning.
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Conclusions:
-- this barrel definitely prefers the 120 gr. GC over the 147 gr. GC
-- while I haven't performed a ladder test per se, best groups seem to be around 2900 fps. Vertical dispersion rears its head at higher or lower velocities. Hence I have been deliberately targeting 2900 fps.
-- Best powders so far are 1) WC844 @1.26" average, 2) LT32 @1.31" average, and 3) LT30 @1.43" average.
-- I have not done enough seating depth experiments to conclude which seating depth is optimal.

Things To Try Next Time And Down The Road:
-- 4198, RL7, RL10, and H322. I suspect they are faster than ideal but nonetheless I will shoot at least one group with each, just to say I tried. :lol:
-- continue tweaking seating depth and velocity
-- try different bullet weights.
-- beyond that, there's always minor tweaks like primers, bullet designs, and lubes. I doubt if I will live long enough to run out of new things to try. :lol:

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Re: 30 BR

Postby mtngun » Sat Aug 06, 2016 6:26 pm

Continuing with the powder comparisons ....

Here are the two bullets I'll be using today. I had forgotten that I had made the 120 in addition to the 130. Oh well, the joy of getting old. :roll: Both bullets had already proven to be respectable performers with WC844. However, today's 130 was nose-sized less and seated deeper than the last time I shot the 130. Also the 130's alloy has changed, from WW to reclaimed shot, so it will not be a 100% apples-to-apples comparison.
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Targets numbered in the order they were shot.

#1: H322 burned very well but accuracy was ho-hum.

#2 & #3: RL10 did well with the 120 grainer. Velocity variation was excellent, too.

#4: RL10 craps out when asked to push the heavier 130 grainer. Why? My guess is that these faster powders are "harsher" on the cast bullet as pressures and velocities go up.

#5: LT32, which did well yesterday with 120's, was ho-hum with the 130. Again my guess would be that pressure and "harshness" are to blame.

#6 & #7: same load & bullet as posted on May 21. But this time not as accurate, perhaps because of the different nose-sizing & seating.
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Conclusions:
-- While the 130 has proven itself just as accurate as the 120 (see the May 21 post), it's easier to get accuracy with the 120. My theory is that the 120 operates at lower pressure and that makes life easier on the cast bullet. Ditto for why it was tough to get good accuracy with the 147.
-- With the 130 grain bullet, WC844 is my first choice, and LT32 my second choice.
-- With the 120 grain bullet I would include RL10 in addition to WC844 and LT32.
-- Seating the bullet deeper to improve reliable functioning may have hurt accuracy compared to the May 21 load. That was anticipated. However, it may be possible to compromise, and more sizing/seating comparisons are in order.
-- at the beginning of this barrel project I contemplated chambering it for 308 Winchester rather than 30 BR. The concern was that the BR would have to use fast powders to achieve my velocity goals, and fast powders tend to be "harsher" on cast bullets. I still suspect that this barrel might be more accurate with a 308 Winchester chamber and a medium speed powder like WW760. And that may happen next year if and when I get tired of playing with the BR. :lol:

Things To Try Next Time And Down The Road:
-- settle on a powder, but in order to do that I need to settle on a bullet. :lol: I'm leaning toward the 120.
-- comparisons with sizing/seating depth.
-- comparisons with wheelweight vs. reclaimed shot.
-- I'm nearly out of the CCI #41 primers that I've been using, so do a comparison with the Remington benchrest primers that I plan to phase in.

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Re: 30 BR

Postby mtngun » Sat Aug 13, 2016 8:50 am

Last time I settled on the 120 gr. GC bullet. I narrowed down the suitable powders but didn't settle on a particular powder or a particular charge. I did some quick and dirty seating depth experiments, but not enough to be confident in the results.

Today's goal was to settle on a particular powder charge and a particular seating depth.

I'm not a big fan of ladder tests but wanted to try it anyway, just to say I've tried it. :lol: The problem with ladder tests is they assume every single shot is statistically significant, which of course is not true. Maybe if you repeated the ladder test 10 times and got the same results every single time, then it would be significant, but no one actually does that. :lol:

So here's my ladder tests for whatever they're worth. RL10 showed very little vertical dispersion, so all I could do was rule out the horizontal extremes.

LT32 showed quite a bit of vertical dispersion, and it seemed to be random. Since LT32 performed poorly in the ladder test, I eliminated it from contention.

Of the RL10 charges, 33.5 landed in the center of the group and had performed decently in last week's tests so it gets the nod to be my standard powder charge with the 120 gr. GC, at least until something better comes along.
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Continued in the next post ....

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Re: 30 BR

Postby mtngun » Sat Aug 13, 2016 9:00 am

Now that I've settled on 33.5 gr. RL10 and the 120 gr. GC, let's fine tune the seating depth with that load.

"JAM" refers to the COL where the bullet begins to make contact with the throat when chambered. "JAM -10" means seating so that the bullet has to jump 0.010" to the contact point. "JAM +10" means seating so that the bullet engraves 0.010" (or possibly gets pushed deeper into the case) when chambered.

Obviously a single 5-shot group for each setting is not statistically significant, so the expectation here was merely to rule out groups that were extremely bad. Based on that logic I'm going to rule out "JAM -10" and "JAM +10". It's a coin toss between between -5, 0, and +5. I'm going to go with -5, at least until something better comes along..

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This afternoon I'll shoot groups with the -5 load and see if it can maintain that kind of accuracy.

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Re: 30 BR

Postby mtngun » Sun Aug 14, 2016 10:28 am

The 33.5 gr. RL10 load looked promising in the previous post, now to see if it is repeatable ....

The short answer is "no." :cry:

There were complications. The velocity of the load had crept up to 2950 fps in the afternoon heat. It's not that I'm opposed to high velocity but past experience suggests that accuracy in this barrel deteriorates noticeably above 2900 fps.

Many of the groups tended to be dispersed horizontally -- in hindsight that could have been due to the heavy trigger pull, more on that later -- but I tried tweaking the forearm bedding. FYI on my other BR calibers with straight barrel blanks I have been bedding the forearm with a thin strip of cheap mouse pad. That seems to work well and is idiot-proof. However due to the 30 BR's tapered barrel, it was bedded with a thin (1/8" thick) strip of foam rubber. The idea was that the foam rubber provides a little bit of damping action but is too soft to exert much upward pressure. However, the foam rubber had taken a "set" and was no longer doing anything, in fact I was able to easily slide it out without loosening the action screws.

Then I tried one group free-floated (3rd row, 4th column). The group was round but nothing to brag about.

Then I tried one group with a strip of mouse pad bedding under the bottom of the barrel only -- not the sides of the barrel. (4th row, 4th column). The mouse pad is a little firmer than the original foam rubber so it did exert some upward pressure on the barrel. Not a lot, but a little. Anyway, the the horizontal dispersion was gone but now it had vertical dispersion. :lol:

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Then I tried using two small pieces of mouse pad on the sides of the barrel channel only, held in place with double sided tape (top row, columns 1 & 2). Groups were not any better but by that time it had become obvious that something was wrong with the trigger so I called it a day.
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The Jewell's trigger pull had been creeping up for some time and by the end of the day it felt like 5 pounds. Testing would later show that it was "only" 4.7 ounces, but even so it was enough to make the free-recoil gun move as the trigger was squeezed. After the day's shooting was finished I removed the action from the stock, revealing some powder grains on and probably inside the Jewell. I sloshed the Jewell in gasoline for a few minutes, blew it out with compressed air, and then it broke at 2 ounces every time. :)

All in all a frustrating day where nothing went as planned. However, I did learn a few things -- I was reminded of the importance of trigger pull and bedding, and that the powder charge may need to be tweaked from day to day or even from hour to hour to keep the velocity in its sweet spot.

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Re: 30 BR

Postby mtngun » Sun Aug 14, 2016 11:03 am

OK, so the trigger pull was restored to 2 ounces and to my way of thinking the 2-piece mouse pad forearm bedding ought to provide a little damping without putting much pressure on the barrel. Let's give the RL10 load one more chance to prove itself.

Because yesterday afternoon's velocities were too high, I dropped the powder charge to 33.3 gr. RL10 (2nd row, 1st column). Then I tried 33.4 gr., and finally 33.5 gr.. The horizontal dispersion was gone and groups were mostly round, but accuracy was still not up to expectations. :cry:

I had been using CCI #41 primers, but am nearly out and will be phasing in Remington 7 1/2's, so I did a primer comparison (1st row, 1st & 2nd columns). The Remington may have boosted velocities 15 fps but otherwise Not much difference in accuracy.

At that point I gave up on RL10 -- sometimes it acted like it wanted to shoot, but it wasn't consistent.

Back to ol' reliable WC844 (1st row, 3rd & 4th columns). Groups looked better than RL10, but were still spoiled by bad fliers. :evil: The fliers had normal velocity and the shots "felt" good, so my guess is they were due to some imbalance in the bullet.
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Observations and Lessons Learned:
-- after experimenting with many powders, I'm back to where I started with ol' reliable WC844 (H335). H335 would normally considered too slow for the 30 BR, but I suspect Colonel Harrison's rule to use slower powders for high velocity cast may be in play here. Slow powders are gentler on the bullet.
-- no significant difference between the CCI 41 vs. Rem 7 1/2, other than perhaps a little more velocity with the 7 1/2.
-- while 2900 fps seems to be a sweet spot for barrel vibes, it may be a little too much for cast bullets. I haven't been able to get rid of the pesky fliers.
-- after the experience with the dirty Jewell trigger, I'm paying more attention to trigger squeeze. You wouldn't think trigger squeeze would matter on a 2 oz. trigger, but it does. I've gotten in the habit of dry firing while I wait for the barrel to cool between shots. When you dry fire, the crosshairs move noticeably (always in the 8 o'clock direction). At first they usually moved 3/16" - 1/4", but with practice I have been able to reduce the movement to 1/8". The sloppy Remington bolt drops noticeably when the sear breaks, making zero movement seemingly impossible. :(

Things To Try Next Time and Down The Road:
-- fyi all of today's and yesterday's bullets used reclaimed shot quenched after curing the powder coat, approximately 25 - 30 BHN. Next time try a comparison with quenched WW (~18 BHN). This barrel's best groups to date were with 18 BHN wheelweight.
-- try different lubes, which I need to do anyway as I am nearly out of Rooster HVR.
-- try weight sorting bullets.
-- if none of those things shrink groups then I may have to drop velocities down to 2700 - 2800 fps. 2900 fps is challenging. :lol:
-- when time allow I will fix the Remington bolt shake, but that will probably be a winter project.

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Re: 30 BR

Postby mtngun » Sun Aug 14, 2016 6:33 pm

Seeing if dropping the velocity to 2800 fps will improve accuracy significantly. Short answer: not much.

Groups are numbered in the order they were shot. Velocities were a little higher than I intended, so I kept walking the powder charge down; however, the lower charges were offset by increased velocity due to barrel heating, so I never did get the velocity down where I wanted it (2780 - 2800). :lol:

The 1.14" average 5-shot group is equivalent to a 1.44" 10-shot group (10 shot group = 1.26 times the 5 shot group) -- not much better than this powder did at 2900 fps earlier today. :) While this is not bad accuracy for high velocity cast, I would like it better if it shot groups like #2 every single time. :lol:

5 out of 8 groups have predominantly vertical dispersion. I ran out of bullets, otherwise I would have kept walking the powder charge down looking for a "sweet spot" with less vertical dispersion.

Besides barrel harmonics, I tend to blame the bullet for the fliers. Not that there is necessarily anything wrong with the bullet, but it may be getting deformed when it is accelerated to 2800 fps. That is the perpetual challenge with high velocity cast bullets.
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A while back I posted this photo of a loaded round where the bullet was a little cock-eyed in the case. I'm seating a little deeper now (0.120" - 0.140" deep), so seated bullets are not as cock-eyed as before, but still they are often a little bit cock-eyed. Back when I was seating shallow and jamming bullets into the rifling I figured they would straighten themselves out, but now that I'm seating a little deeper and jumping to the rifling, they may not straighten themselves out. :(
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Why are they being seated cockeyed? Well, My seating die is homemade and is the simple kind that does not guide the bullet while it is being seated. So I will try to find time to make a fancy seating die, the kind that uses a floating bushing to guide the bullet. We'll see if that helps.

To test the hypothesis that bullets may be getting deformed as they are accelerated, I ordered an identical 18" twist Krieger barrel that I plan to chamber for 308 Winchester. The idea is to shoot the 308 and the 30BR side by side with the same bullets at the same velocities in identical Krieger barrels, only the 308 will use a slower powder like WW760. The differences in pressure and acceleration will be small, so I don't expect to see a huge difference in accuracy, but if my theory is correct the 308 should have a slight advantage. We'll see.

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Re: 30 BR

Postby mtngun » Sat Feb 18, 2017 9:35 am

Looking over my previous posts for this 30BR, I was struck by how far out I had to seat the bullet to catch the rifling. In hindsight the throat was too long for the light bullets that I prefer to shoot in this 18" twist.
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So .... I decided to set the barrel back and try again. I used homemade reamers except for the throating reamer. While I am satisfied with my current generation of homemade D-bit reamers, a D-bit is less than ideal for cutting throats. The cutting angle is not as "sharp" as a store bought reamer, plus the single cutting edge tends to "catch" on the rifling. So used a store bought reamer thinking it would be better. Well it did cut smoothly, however I found out later that the 1.5 degree store bought reamer was not actually 1.5 degrees. In fact it was more of a curve! :lol:

FYI the "chamfer" reamer puts a slight chamfer at the entrance to the throat, so the gas check won't catch on the sharp edge.
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I deliberately cut the throat on the short side, so the bullet has to be seated deeper. Due to spring back while nose-sizing, the front band engraved hard and would not allow the bullet to seat out as far as I prefer. So I need to go back to the drawing board on the nose die for this barrel. Pic of nose-sized bullet and cartridge with bullet seated to engrave front band.
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Even though I wasn't satisfied with the nose fit, I wanted to shoot a few anyway, just to see what would happen. I used a randomly picked load of 32.0 gr. RL10, oven treated reclaimed shot about 35 BHN, and BAC lube. Both the rifle and the ammo were cold, 40F. Velocity ranged from 2608 (the 1st shot) to 2677 (the 9th shot). I broke from my usual practice of shooting a fouling shot, and instead fired the very first shot into the group. It landed in the center of the group. The outliers were #4 (the highest shot) and #5 (the low flier). So not a great group, but bear in mind this was shot cold and BAC lube generally does not give top accuracy when it is cold. I have not tested this load in warm weather so I have nothing to compare it to.
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11 shots were fired total, and at least 3 gas checks came off and hit the cardboard exit of the muffler. I was dissappointed because this chamber and this bullet employed all my best practices for eliminating flying gas checks. However, note that there was still a tiny bit of lube on the check shank -- it's difficult to entirely eliminate lube on the check shank.
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Observations:
-- the good news is that the Loverider design shot a fair -- though not great -- group when it was cold. The first shot from a cold barrel went into the group.
-- the bad news is that at least 3 gas checks came off.
-- Fired case necks measured the same as loaded case necks -- 0.331" - 0.332" -- so I may need to turn the necks just a wee bit. Nonetheless there was no difficulty chambering the loaded rounds. For the time being I'll monitor the situation closely.
-- I need to tweak the nose sizing die so the bullet can seat further out.
-- beyond that I can't say much until I test in warm weather, because I know from experience with the 7BR that cold temperatures can hurt accuracy with this lube.

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Re: 30 BR

Postby mtngun » Sun Feb 19, 2017 7:36 am

Another cold temperature test with the Loverider design, except this time 1) I scraped the lube out of the check shank and 2) I increased the powder charge to 33.0 grains.

Shot #1 lost its gas check.

The good news is that it shot a group -- rather than a shotgun pattern -- despite the cold, and the 1st shot from a cold clean barrel went into the group. The bad news is that it still lost at least one check, and the accuracy was nothing to brag about.
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Now let's shoot a Loverin for comparison. These were leftover from last year, and have Rooster HVR lube, and a hybrid coating. They may be made of wheelweight rather than reclaimed shot like the Loverider. In any event they didn't spring back as much in the nose sizing die so they fit the throat better than the Loverider.
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Shot at 40 degrees with no fouling shot. The cold Loverins with HVR did just as well as the cold Loveriders with BAC, and no gas checks came off that I know of. Of course it is not a 100% apples to apples comparison because there were slight differences in the BHN and the lube. As far as I know the coating has no affect on GC bullets and I no longer bother to coat GC bullets.
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In this particular barrel and chamber, the Loverider design does not seem to have any advantage in cold weather, and the 1st shot from a cold clean barrel lands within the group. :)


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