7BR with cast boolits

[charlie b]

Well, I've had some mixed results with the 6BR, but, not better than 1.5MOA.

Varget was a bit erratic, but, I think I need to revisit it since it gave a bit lower vel with same volume charge as the IMR 4198 (which I have used successfully in the .308 with mid-velocity cast).

My first loads with 4198 were around 2200fps. This is on the high end of spin rate for this caliber. The 1-8 twist is the problem. I tried some lower loads and have a candidate at 16.7gn and 2120fps but relatively poor es/sd. 1.5-2MOA seems average for this load. Not great and still some bad fliers (typical of too high spin rate). When I went to lower loads the muzzle vel was very erratic. This is 100yd, squares are 1/2".

https://i.ibb.co/0VQxvC8/test.jpg (https://ibb.co/CsWfDbN)

So, am going to try Varget a little more and see what happens. I'd like to be in the 1800fps range.

A new guy at the range was shooting his Schuetzen rifle (breech seating). Sharps Borchardt action, .32-40. He was getting 0.3" and 0.4" groups at 100yd.

[PhilC]

I haven't posted much but I've run into the same conundrum. What started off nice, went south. Barrel leaded up even shooting loads that produced good groups initially with boolits cast at the same time and no other change in components. Tried powder coat vs traditional lube but no improvement. Sat down with my targets and notes 2 weeks ago trying to figure out where things went bad, the only constant was a 100 - 150fps increase in MV, so I reduced charge weight to velocities that previously shot well without much improvement.

During last Saturday's match my best 5 shot group was 1.52" with an agg of 1.87", best 10 shot group was 2.4" with an agg of 3.32". Score was a dismal 162. Chono'd velocity with 25.4gr N135 averaged 2167fps with SD of 5.0 and ES of 16.

Recalled I was plagued by similar problems with my 6.5CM until I slowed it down so pulled the tech data from the 2021 CBA Nationals and found 10 competitors shot 30BR. Here's what I found:

9 of 10 used linotype
8 used Fed 205M, 1 used Win SR and 1 used Win SP
Avg barrel length - 24"
Avg twist - 12
Avg velocity - 1960fps
Avg boolit weight - 194.7gr
All competitors used lube and gas checks
3 used Varget, 2 used A2495, 2 used N135, 1ea used N133, IMR3031, IMR8208

The grand national champion shot a 30BR with a 12T 24" Shilen using 207gr boolit over 29gr A2495, Fed 205M, at a chrono'd velocity of 1750fps.

I've re-run QL with the Ba factor adjusted to match actual chrono data at two low nodes with predicted velocties of 1821 & 1909fps. Had hoped to shoot this morning but is raining, maybe tomorrow if weather clears up.

RPM of my current load is over 173k, the new loads will drop rpm to 145k & 152k respectively and fully expect one or both to shoot well. Found a great deal on pure linotype direct from a printer for $1.45/lb delivered and have 110lbs enroute.

[charlie b]

The RPM 'limit' is based on radius. For .308 it is around 144,000rpm. That means it is a little faster for smaller dia. The loads that my .308 shoots consistently well are in the 1800fps range. The only 'difficulty' I have is load density. Some powders do ok, some don't.

The .30BR rifles are usually slower twist which means they can go to higher velocities without incurring the penalty of RPM effects. It really does seem the 'normal' .30BR barrels are ideal for cast bullets. Looking at folks who shoot them with jacketed it seems to be a very forgiving cartridge.

For now I'll just keep shooting my .308 with cast and leave the 6mm alone for a while.

I think you will be better off with those slower loads, if you can find a powder combination that works.

[PhilC]

I agree. Only way to know will be to load and shoot, maybe this week if weather and time permit.

[Fuj']

Still following.....

It's still aways down the road before I might decide but, My thinking since casting
bazillions of pistol bullets, my idea would be to go for a much fatter style of bullet.
Maybe do a 30 cal with a smaller case, more like the 30 major/Grendel. Get that
powder charge way down but fast. It's possible the BR case is just too much capacity ??
Just thinking out load !!. Maybe also something short and shaped like one of Robinett's
30's. Thinking maybe, the least amount of twist I could get away with, and the least
amount of grooves, and hang a tuner on the end.....

[charlie b]

Fuj, an interesting area to explore. Not sure anyone has really done all the work.

Historically cast bullets are shot at slower velocities for a few reasons. Initially barrel leading was a problem, but, current lubes and gas checks have been successful up to around 2600fps (in .30cal). Then there were the guns. Most are made with rifling twist for jacketed bullets, which means the RPM is limited, which means the vel is limited. Again, some have experimented with slower twists and reached higher velocities.

If it were me I would think a higher vel would be better, just for wind effects. Not sure where that optimal vel would be with a light bullet. If you look at the BR shooters the 30cal bullet weights vary from 130 to 230gn. Most seem to keep the vel in the 1500-2000fps range. Why? Don't know. I suspect the ones using heavier bullets do so to reduce the wind effect, but, again I am just speculating.

I would be very interested in someone pushing some of those boundaries. :)

[charlie b]

Just for reference here is a group from this morning with the .308. Accurate Mold 31-210E adjusted for powder coating. Yes, this was 200yd and those are 1" squares. Wind had was pretty consistent at this point but I still had not adjusted enough for it. Vel was just over 1800fps. Yes, these were powder coated bullets. My 'normal' group is closer to MOA at that range. The wind 'blew out' the other groups to 3" horizontal.

https://i.ibb.co/K5XV8NQ/200yd-210gn.jpg

You can see why I like the .30cal bullets. The 165gn XCB (NOE 310-165) does just as well but is sized and lubed.

Sorry for the hijack. Probably need a new thread.

[Fuj']

I still like my 7mm's for just about everything but this cast rifle bullet thing
can bring some good discussion. At the range myself yesterday finishing my
tuner tests for Saturdays match, I found a lone 300 Blackout case lying in the
grass.....I said " Hmmmnnnn" A Blackout with 110 to 125 grain jacketed bullets
will do about 2300 fps by average. I've heard 2450 fps with the TNT's and 4227 ??
That case looks very efficient for a cast bullet and speeds. Heck, good Ol' 2400
would work.....I need to start playing with JBM and bullet lengths to find a really
low twist rate.

Anyone play with coating cast bullets with Moly or HBN ??

[charlie b]

You could just try some cast in 7mm as Phil is doing. Keep it in the 'family' :)

2400 is a very common powder for cast. I'd have tried it by now but I don't have any. For the mid range loads (1500-2000fps) it seems to do really well.

Cast Boolit forum has a ton of folks experimenting with cast coatings and lubes. Moly coating has been tried in several different ways and does not seem to make a lot of difference. Having said that, my bullet lube uses Stalube Extreme Moly grease as the lubricant and beeswax as the carrier. HBN I am not sure. I have not seen any mention of it. The two 'big' coatings used these days are Powder Coating and HiTek. Both are baked on. HiTek is a proprietary formula so I don't know what is in it. There are several companies who sell coated bullets that use HiTek.

There was a lot of cast experimenting in the BR crowd back in the 80's. I remember a series of articles about using moly coating. The results were ok, but, not better than standard lube. They also experimented with polyethylene wads instead of gas checks. Those did work well, but, you had to use a case with a relatively long neck (IIRC they were testing using a .32-40 case). There is still a Cast Bullet class for plain base bullets.

FWIW, the biggest area of cast bullet performance is the casting of the bullet itself. Making a bullet with the fewest voids/flaws. Not as easy as it sounds. From what I can tell the most consistent results come from ladle pouring. Of those the ones that use the Lyman ladle and hold it against the mold do the best. After that, temperature control is key. I use a bottom pour pot as I like the convenience, but, I also cull out quite a few bullets. Some of the 'pickier' shooters will only keep 25% of what they cast. My 'control' is bullet weight. Bullets are sorted to 0.1gn and I only keep the ones on the high end of the curve.

.300 BO is a popular case for cast with the AR crowd. Most of them are using faster twist barrels so they get mixed results (and they are trying to cycle the action) It does seem to be a good size for light bullets. Reminds my of my old .30 Herrett.

[PhilC]

I'm waist deep in pulling the engine from my truck for some major preventive maintenance so check in here then head for the shop while it's still nice and cool. Almost time to head out, engine should be on the stand by noon.

Only coating I'm using is Smoke's powder, if not that, it's traditional lube, White Label's 2500+ in particular.

[charlie b]

I use Smoke's powders as well. For the rifles I have settled on Smoke's clear for a number of reasons, but, it also seems to shoot a little better. Not sure why. My guess is the lack of pigments means the coating has a more consistent thickness. I can't prove that, but, it is the only thing I can think of that would make a difference.

Good luck on the truck :)

[charlie b]

Just for grins I went back to the CB forum and looked up HBN info. Seems a lot of people in years past have tried it and moly. Most of the moly users seem to have stopped using it for various reasons. The consensus was that just moly or HBN on a lead bullet doesn't work. Some liked moly in their bullet lube, some not. Some tried HBN in the bullet lube but it didn't make a lot of difference.

There were a few who have tried tumbling already coated PC bullets in moly and/or HBN (those that I read about already had tumbling setups for their jacketed bullets). Those folks seem to have the same kind of results as jacketed bullet users, ie, the moly coating is contested but the HBN coating seems to be good. One guy who used the HBN on his powder coated bullets really like it with only two downsides. First, the bullets were so slippery they were hard to handle. Second, the health effects of HBM needing a good mask and gloves.

The conflict over the results of using moly in a barrel seems controversial.

If the regular PC didn't work so well as is I'd be tempted to try the HBN on top of the PC.

[charlie b]

Fuj,

What is your take on moly vs HBN?

[PhilC]

Back to 7BR...some success from Saturday's match, now, if I could get those to repeat and eliminate single flyers the entire match I'll be satisfied. :-)

https://i.ibb.co/jy6J5kK/5shot.jpg (https://ibb.co/jy6J5kK)

https://i.ibb.co/8YZjW3h/5-shot.jpg (https://ibb.co/8YZjW3h)

https://i.ibb.co/h9QY8Wv/10shot.jpg (https://ibb.co/h9QY8Wv)

[charlie b]

Nice work Phil.

[Fuj']

Back to 7BR...some success from Saturday's match, now, if I could get those to repeat and eliminate single flyers the entire match I'll be satisfied. :-)

https://i.ibb.co/jy6J5kK/5shot.jpg (https://ibb.co/jy6J5kK)

https://i.ibb.co/8YZjW3h/5-shot.jpg (https://ibb.co/8YZjW3h)

https://i.ibb.co/h9QY8Wv/10shot.jpg (https://ibb.co/h9QY8Wv)

My experience when shots go low is the rifle is nose heavy and needs weight in the stock.
Shot fliers going high is bounce on the front bag and why some shooters claim better groups
with a soft front bag. That last target if not a sighter, looks like some wind....

[Fuj']

Fuj,

What is your take on moly vs HBN?

No experience with HBN, and the only moly used was to mix some powder with a 50/50
mix of Alox and bees wax for non gas checked bullets. Not a fan of powder coat because
of being uneven and screwing up stability. I guess it's fine for plinking ammo only.

Let me ask a question.....With cast bullets, how do you sort them for match's ??

[charlie b]

Thanks. I just wondered about all the supposed issues with moly. One of the easiest lubes to make is a 50/50 mix of Sta-lube Molygraph and Beeswax. But, I don't clean the barrel after every session so it might go a few weeks. I do have a stainless barrel, but.... The other lube I like is Lucas Red N Tacky and Beeswax.

My PC bullets shoot as well as the non-PC bullets. But, that may be an issue with my skills rather than the bullets :) The 210gn bore rider I shoot requires PC to fit the bore properly and it shoots as well as the lubed bullets (not bore riders). But, I like the convenience of the lubesizer and a one step process. It just happens that the longer bore rider is a better bullet at long distance for me.

Sorting is done by weight and visual. I put the bullets in 0.1gn batches and visually inspect for flaws. I usually have 5-10 bins of bullets, eg, 167.1 to 167.7gn. For 'matches' I will pick only the heaviest bullets, eg the 167.5, 167.6 or 167.7. Each 'match' would be fired with a single weight of bullet, eg, 167.7gn.

From my experience the 0.1gn difference is not that much of a deal, ie, I could probably sort into 0.3gn batches and do just as well. But, the mental thing gets involved :) The bigger factor is the heavier bullets have fewer/smaller voids. This is a factor if you start pushing the RPM of the bullet.

[PhilC]

Last target was one of two 10-shot group targets and wind did pick up a bit but was from ~8 o-clock position so group should have shifted to the 2 o-clock position.

One thing I noticed during the match is I cannot put any pressure on the stock, if I do, point of impact and consistency is erratic. The 1st & 2nd targets above were shot with no stock contact at all, not even my right thumb for trigger pull, instead, I used rear of the trigger guard to anchor my thumb.

Alloy used was lino/Pb @ 1:1, sized within 12hrs, then left to harden naturally. Gas checked, lubed, and loaded 2 days prior to the match.

[GrenGuy]

Even though I don’t do cast, yet?, it’s good to hear from a competitor.

Yes, Free Recoil works best from the Bench for Me.