Please educate me on the 375 Win and cast boolites.

[Muskyhunter1]

I have been shooting my 38-55's for years with cast and have a great accuracy. Today I decided to play with my Marlin 375S in 375 Win (Micogroove). I loaded 20.0 grain of 2400 behind the following .377 sized bullets with Lyman Lube:

Lyman - 249 grain 375248, and
Lee - 250 grain.

The rifle shot terrible and was all over the paper and even key holed at 25 yards. I don't get it with jacket bullets this same rifle will put a bolt rifle to shame at 100 yards every time. I have sizing dies from 375 to 381 but i heard .377 was the way to go (I know I need to slug the bore but it should be .375 dia as it is a fairly new rifle).

Does it have some to do with the rate of twist and/or weight of the bullet, the 375 Win throat, the length of the ogive (nose) on the cast, the WW boolite alloy. This same load shoots very well in my 38-55.s

Can anybody who loads cast in this round give me some pointers for success?

Thanks,

[Tatume]

I don't get it with jacket bullets. This same rifle will put a bolt rifle to shame at 100 yards every time.

I'll take that bet.

You don't say whether you have completely cleaned the copper from your bore. Although I've never seen copper fouling cause keyholes, it will create inaccuracy.

Take care, Tom

[TomAM]

When you slug your barrel, I think you'll find a groove diameter of .378+". That's what I've found on 3 Marlin 375s so far.

Then measure throat depth. Full diameter can usually extend about .3+" beyond the case mouth.

The Ranch Dog 375 deals with the throat issue by using a clever multi-crimp design. Since only the lowest crimp groove is needed for the 375 Win, my solution is #38-235A in my catalog.

[Muskyhunter1]

I'll take that bet.

You don't say whether you have completely cleaned the copper from your bore. Although I've never seen copper fouling cause keyholes, it will create inaccuracy.

Take care, Tom

Well maybe not every bolt rifle - lol. The point I am making is it is very accurate but your are right I guess I need to check for copper fouling. Thanks

[Muskyhunter1]

When you slug your barrel, I think you'll find a groove diameter of .378+". That's what I've found on 3 Marlin 375s so far.

Then measure throat depth. Full diameter can usually extend about .3+" beyond the case mouth.

The Ranch Dog 375 deals with the throat issue by using a clever multi-crimp design. Since only the lowest crimp groove is needed for the 375 Win, my solution is #38-235A in my catalog.

Wow .378+ I would have never thought Tom. I guess you are correct I need to slug it. I have a couple of your Ranch Dog designs here Tom and they are great. Awesome accurate hunting bullets I might add.

Just for clarification you are saying the 375's throat is straight for about .3+ before the throat begins to taper (free bore) whereas the 38-55 tapers from the end of the chamber but slowly?

When you say the lowest crimp groove you are referring to the groove closest to the lubrication grooves (aft) - correct? Basically you want to get the ogive of the bullet as close to the rifling in the throat while maintaining max. overall length.

Thanks Tom.

[Artful]

Ranchdog did it very well
http://www.ranchdogoutdoors.com/bin/TLC379235RF/bullet/sketch.jpg
http://www.ranchdogoutdoors.com/bin/TLC380250RF/bullet/bullet_sketch.jpg
http://www.tmtpages.com/LinkSkyImages/ranch_dog/RDCartridgeSketches/Images/375_WIN~WW_Super~RD_Mold-TLC379-235-RF_Case.Jpg

http://i56.photobucket.com/albums/g181/ReeceTalley/freeboreIV.jpg (http://s56.photobucket.com/user/ReeceTalley/media/freeboreIV.jpg.html)

http://www.levergunscommunity.com/viewtopic.php?f=1&t=22035

[Muskyhunter1]

Thanks Artful. Amazing graphics that answer a lot of my questions. You obviously have been playing with this caliber. I noted today while cleaning my 375 Win. rifle shards of lead fragments were on the patches. I gave it a really good cleaning.

Would that be caused by the WW bullet being under sized (.377 dia)? I am using Lyman Alox bullet Lube now but I have all the ingredients and I am going to make some Ben's Red in the New year when things slow down (hunting season is over - lol).

Thanks for your help Lads.

[runfiverun]

lyman 375449 sized to 379.
that's where I finally found happiness in my marlin and Winchester.

[Muskyhunter1]

I have that mold and can do that runriverrun - thanks. What powder did you use and are you gas checking it?

I checked the Lyman Cast Book (4th Edition) for the load I was shooting yesterday and they list 24.0 grains (min load) going out at 1595 fps with a 249 grain boolite (Lyman 375248 no gas check). Maybe i should be using a gas check boolite as I am getting up there in velocity.

[runfiverun]

definitely using the gas checks.
I'm pushing them pretty hard in the marlin using aa-1680 probably a bit too hard actually.
i'll probably end up slowing the powder down to aa-2230 or imr 4198 when it's all said and done.

I tried a couple of plain base molds and they fell out at about 1450 fps or so.
but I wanted more velocity to help with the sight settings, and went with the gas check mold and started pushing things.

[Artful]

Thanks Artful. Amazing graphics that answer a lot of my questions. You obviously have been playing with this caliber.

I have a Winchester Big Bore Lever, Ruger #3 and Barrel for my Contender. As a game round I like it - never had to fire a second shot when using either 375 Winchester or 358 Winchester with cast boolits :bigsmyl2:

Marlin Microgroove barrels have always done better with gaschecked or tubular cast in place jackets for me.

[Muskyhunter1]

Ok I slugged my 375 bore last night but the slug (bullet fishing sinker) broke in half before I got it thru the bore. Tom was correct. Even with the lose slug she measured .3775. If the slug was tight it would have been an easy .378. I loaded up a box of .379 dia Ranchdogs tonight as per Artful and Tom's specs. My Ranchdog has a gas check so I will report back after my next range trip. Thanks

[Muskyhunter1]

Went to the range yesterday. Thanks to you folks the results were much better but there is lots of room for improvement.

Without revisiting the load development process, I found my pet 38-55 load of 21 grain of IMR 4227 was not that great in the 375 Win. I guess I will switch and use the powder it seems to love with jacket bullets which is RX 7. Hopefully my groups will tighten up considerably.

This group was at 50 yards. I used Tom's 250 grain Ranchdog GC sized to .379 dia. with an overall length of 2.505 inches with the 4227 load as above.

A five inch nine shot group in a string at 50 yards. I personally look at it as pretty poor group considering I shot a group half this size with an iron sighted Marlin 93 in 38-55 at 100 yards with the same bullet and load. The 375 Win Marlin has a scope too............. I am not too sure why the load is stringing and believe as the shots progressed in strung downward. The shots were in succession about 3 mins apart. Given it is winter and cold up here, it really shouldn't cause that big of a difference. It hasn't in other rifles (38-55 etc.)

124551

After checking all the posts in this forum in relation to cast and the 375 Win, a number of members seem to really like Rx 7 powder in this caliber. My question is why does it preform better. Is Rx 7 a faster or hotter burning powder than IMR 4227? If it is, maybe the pressure spike comes faster and the bullet base upsets into the mico groove bore more quickly. Thus giving better accuracy. Just a thought. Any opinions?

[MT Chambers]

I'd try the widest bullet that will chamber.

[Pepe Ray]

It looks, to me, more of a rifle problem than a load problem.
I would check the bedding or contact points between fore end , tube and bbl.
Too much stress, not allowing for movement (expansion).
Is it worth $0.02?
Pepe Ray

[Muskyhunter1]

It looks, to me, more of a rifle problem than a load problem.
I would check the bedding or contact points between fore end , tube and bbl.
Too much stress, not allowing for movement (expansion).
Is it worth $0.02?
Pepe Ray

Thanks Pepe Ray. I would normally tend to agree with you, but this same rifle will shoot a nice tight group with jacket bullets at a 100 yards. I cleaned the rifle yesterday and there is no fouling to speak of. Just carbon/powder residue.

[Charley]

I've had the same issue with my Marlin. I've gone from .376 to .380, in .001 increments, different molds, commercial cast, etc. Still looking for the load. Shoots great with jacketed, mediocre to horrible with cast.

[Muskyhunter1]

I've had the same issue with my Marlin. I've gone from .376 to .380, in .001 increments, different molds, commercial cast, etc. Still looking for the load. Shoots great with jacketed, mediocre to horrible with cast.

Stick around Charley - maybe we can figure this out together. Over the next week I will load up some shells with Reloader 7 and report back. They say the 375 loves that powder and my rifle seems to be no exception.

[TomAM]

I've gotten mine down to about 3.5 MOA using Reloader 7 and FAT (.380") boolits that fill the cavernous throat.
RL7 has produced the best groups, at least for my 375s.

[Charley]

Stick around Charley - maybe we can figure this out together. Over the next week I will load up some shells with Reloader 7 and report back. They say the 375 loves that powder and my rifle seems to be no exception.
Mine didn't. At least it shot groups (large ones!) with it, not patterns.

[Muskyhunter1]

Thanks Tom. Next weekend I will be trying your Ranchdog and Reloaded 7

Charley do you have a Ranchdog mold? I have the Accurate mold Ranchdog from Tom here on the forum and I think it will shoot for me. It will just need a little tweaking with powder lube seating etc.

[Muskyhunter1]

I just got back from the range and I am happier with my results. Reloader 7 seems to be the powder my rifle likes. I have to admit I am not thrilled with my groups considering my old iron sighted 38-55 can still out shoot the 375 Win at 50 yards and 100 yards with cast - so far. On a positive side, I am making progress and I would feel confident on the bear stand with this load given most my shots are under 50 yards.

My load was 30.0 grains Reloader 7, CCI 200 primer, 250 Ranchdog WW sized to .379 with a GC. Unfortunately I was in a bit of a hurry today as I spent the earlier part of the afternoon trap shooting, so I was racing against darkness.

This is my first group of 6 rounds at 50 yards.

124997

I wasn't thrilled so I shot off another ten rounds at the next target. Note - it appears I had one flyer. Not sure if it was me or the bullet - I guess i will never know (likely me).

124998

I think I am definitely heading down the correct route thanks to all the excellent guidance. As Tom said maybe I need to get a .380 sizer and fill the cavity (anyone got one for sale Lyman/RCBS?). I have a .381 but it might be too big. I think I can improve the accuracy of that powder combination. I will reload an bunch of shells in 1/2 grain increments from min to max with Reloader 7 and see what that does for me. I will post the results when I am done.

[TomAM]

I had Buckshot make me a .380" sizer die. I highly recommend him. Excellent work, reasonable price, quick turnaround, and that extra thousandth trims a couple inches off the group size.

[TomAM]

If your .381" die engages your boolits (you can't size them up) and they don't make the cartridge too fat to chamber, then it's not too big. Go for it.

[Muskyhunter1]

If your .381" die engages your boolits (you can't size them up) and they don't make the cartridge too fat to chamber, then it's not too big. Go for it.

Hey why not - thanks. I am not getting any sign of pressure now with my current load and a .379 dia slug. Two of the molds you made me drop at .382 so I have lots of room to play. It might me just what is needed. I am working the next while thru Xmas so I will have to wait a week or so before I can play. Thanks again Tom.

[Muskyhunter1]

Tom - You were correct again. The .381 dia slug was the way to go.

I had an amazing day at the range today. I loaded up a bunch of your Accurate mold 381 dia sized 255 grain Ranchdog GC cast and got amazing groups. I think I will be willing to hunt with this rifle now. These loads can also be improved over time.

The first group was 8 shots at 50 yards. The powder was 20 grains of IMR 4227 which is my favorite for my old 38-55 levers (light for 375). It shot really low but grouped really well.

126372

I then ran my loads from minimum to maximum (in 1/2 grain increments) of Reloader 7 behind the same Accurate .381 Ranchdog GC cast (as above). They all group well even 32 grains (max at 1811 fps) but my sweet spot was definitely at 31 grains. This was 9 rounds at 50 yards.

126373

I want to thank everyone for their help with this project.

The following is a highlight of the points that I think (correct me if you think I am wrong) were critical for accurate cast boolites rounds in my Marlin 375S in 375 Win caliber.

- I slugged my barrel - mine was .3775 but the slug broke so it is more likely .378 dia (I shot .377 dia slugs that leaded badly and accuracy was real poor - .379 dia slugs showed remarkable improvement in accuracy and no leading was evident),
- My boolites were cast of wheel weight composition - maybe I should consider water dropping them in the future,
- I work my way up to a cast .003 thousands of an inch larger than my groove diameter .381 dia (no pressure signs at max. load),
- COAL was maximized to get the boolite seated as close to the throat of the rifle as possible for Reloader 7. The IMR 4227 loads were in the most forward crimp groove as used in my 38-55 rifles,
- Used a Accurate mold Ranchdog configuration cast boolite to get the boolite ogive closer to engage the rifling ASAP in the throat after the freebore,
- Gas Checks possibly were very beneficial with the Microgroove rifling, and
- Reloader 7 and IMR 4227 seem to be my very promising powders.

Thanks again for all your feedback folks.

[Artful]

I like Accurate 5744 powder in mine but I'm going to have to look for some Reloader 7 now.

One of the things I want to try this year is powder coat on the NEI mold
designed for copper tubing jacketed cast boolits.

[Muskyhunter1]

Artful - Ok you have my curiosity, what are these NEI molds for copper tubing jacket cast boolites? Sounds like a new challenge.

[Artful]

3/8 copper tubing is .375 diameter - if you have a mold you can cut the tubing to length and insert into the mold just before you pour your boolit and it solidifies into a copper tube jacketed boolit.

Walt *(NEI) made up two for me - one in 293 grain
http://img.photobucket.com/albums/v355/rowdyfisk/FAL/Boolit/NEI375293J2cav2_zps8f8afb89.jpg (http://smg.photobucket.com/user/rowdyfisk/media/FAL/Boolit/NEI375293J2cav2_zps8f8afb89.jpg.html)
the other 240 grain - I wanted them when I got my 375 Weatherby Magnum.

[Sweetpea]

Do you just use a tubing cutter?

Seems that it would leave a bit of a locking ring, could be a good thing.

Preheat the copper on the hotplate?

[Artful]

Yes and preheat in the lead pot.

[Muskyhunter1]

That is really interesting. Do you have some pics of the finished product.

Any chance the core could separate on firing and leave the jacket in the barrel. Wouldn't be a good thing.

[Artful]

That is really interesting. Do you have some pics of the finished product.

Any chance the core could separate on firing and leave the jacket in the barrel. Wouldn't be a good thing.

never had one separate - you could consider it soldered in. I'll poke around my stuff to see if I have one to photograph.

[Muskyhunter1]

Artful,

True I never thought of it that way as being soldered in. Sorry for so many questions, but how do you cut the jackets in consistent lengths and what kind of accuracy do you get?

This is very interesting.

Thanks,

[Artful]

Accuracy was sub 2 MOA from 375 Weatherby mag with 88 grains of 4350 at 100 yards.
Tubing cutter was followed up by a little filing to make length spot on.

[NVScouter]

Artful please please please show us a finished round!!!

[HD.375]

Bump--- Wheres Artful gone.........
this is relevant to me, so i dont mind reviving this thread.