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Discussion Starter #1
I've been working on my elk load using Marshall's 250 gr LFNGC and it appears that I may be reaching maximum.  I'm basing this on observation of velocity and pressure ring visibility.  I'm currently sitting at 35.7 gr of Re7 in Win 38/55 cases seated to an OAL of 2.560".  I know how each gun can be it's own rule but am wondering if I should be able to expect greater than 2050 fps with this load?  I haven't firelapped this Marlin barrel yet and hope to gain at least 50 fps based on that alone.  Accuracy isn't bad (tested at 50 yards) but hopefully will also improve with firelapping.  I realize that more velocity won't necessarily give me any more usable penetration but based on last week's exercise in "working down" loads it's obvious that flatter trajectory will be a good thing as far as effective range goes.

Marshall, you've posted data similar to mine that gives you velocities in excess of 2200 fps (if memory serves).  In another post you've mentioned lengthing the cartridge carrier stop to allow loading longer OAL.  Is the latter most likely the reason for my loads coming up short?  Also, how involved is the carrier stop modification and is this a gunsmith only procedure?

One more question, you don't have 375 Win slugging sinkers listed in your catalog.  Is this a mistake or a reality?
 

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Bart,

About the carrier alteration for your .375 Marlin.  The directions given on our Tips section for the 1894 Marlin apply directly to your .375 Marlin.  Same process, same results.  The only thing you may need to do, is to modify the ejector that sits in the left side of the receiver.   In its current factory guise, it may not allow you to eject a loaded round from the chamber, and in this case all you need to do is to remove the bolt, drop out the leaf-spring loaded ejector, and mill back the forward portion of the flat part that contacts the rim of the cartridge case.  As I recall you can take about 0.060" off of this part of the ejector to gain the necessary length to reliably eject the longer COL we are discussing here.  On some rifles it isn't even necessary to do this little proceedure.

As for the lapping, don't be surprised to find you gain your anticipated 50 fps, and maybe another 25-40 fps beyond that once the constrictions are removed where the front magazine hanger is dovetailed into the barrel and the rear sight dovetail the same way.  Often these constrictions are .0015"-.002" and can raise hob not only with potential accuracy, but velocity as well.  Above all, make sure when you are finished lapping that you follow through and do the final polishing step as outlined in the Technical Guide.  This is essential to reap all the potential benefit from your lapping, and to maximize the performance of these MicroGroove barrels.

Once lapped, I think you'll find that your loads operate at a slightly lower pressure, and that your velocity will increase.  Too, you'll be able to increase your load marginally due to the lower friction coefficient of the barrel.  Yes, RL-7 is a great powder for the .375 Winchester cartridge, but I've also found that AA 1680 is by far and away the best powder for the loads you are developing.

Lastly, about the egg sinkers.  Nope, not an oversight or misprint!  Commercial egg sinkers are designed for fishermen, and are made to specific weights, unfortunately none of the commercial weight egg sinkers correspond favorably to the .375 caliber bores!  Sorry!

Let us know what you end up with after your lapping project, and some more load development!

God Bless,

Marshall
 

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Discussion Starter #3
Thanks for the info Marshall.

The carrier modification thing is good to know.  Once I chambered a dumby round with bullet loosely crimped to see how long my rifle could chamber.  It measured about 2.610 but I couldn't eject the round without tapping the bullet down a little with a dowel through the muzzle.  I was just a little bit too long...just a little.  I suspect that 2.600 would eject fine.  But that would leave me with the feeding problem.  Sounds like that one isn't too hard to tame.

As for the final final polishing step, we just moved into this house and I've misplaced my BTB Technical Guide.  I recall it had to do with hand polishing with a rod and patch-wrapped brush, and a little polishing compound, or something to that affect.  It'll turn up before too long I hope.

I'll have to pick up a can of AA1680.  Can you recommend a starting load?  I'm reaching for top velocity and accuracy...but then that's the norm I think when developing a load for really big game such as elk or moose.  It seems most of the top load data I've seen for this cartridge involves Re7.  Of course I'll have to weigh this all out with respect to the number of BTB bullets I have left.  I can afford to experiment with 150 or so more rounds but then it'll be time to load 'em up for the upcoming season, which is inside the 12 week backorder window now.  I'll probably just stick with Re7 for this season.

I'd like to extend my support for an article on this cartridge since you are by far one of the most knowledgeable on the subject.  I've read Paco Kelly's articles and they are interesting, but most of his data involves either modifying factory bullets or handcasting bullets which we don't all have access to.  I'll bet there are a lot of others out there who would like to see this too.

I just ran across a recent article over on sixgunner.com by the above mentioned writer.  He is quoting some pretty stiff ballistics for a couple of his 375 Win loads.  For example, a 300+gr homemade cast/jacketed bullet at nearly 2300 fps?  Or another homemade cast/jacketed of 265 gr exiting the muzzle at over 2470 fps?  I know how one of our moderators feels about the subject writer and am not trying to stir up trouble, but these loads sound like trouble to me.  These are getting into highend 444 territory.  Paco's rationale has always been that the Winchester BB will handle more pressure than the Marlin.  Is there any truth to the BB vs Marlin argument?  And are these loads really safe in the BB?


(Edited by bartmasterson at 4:32 pm on Aug. 30, 2001)
 

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Bart,

As for the article on the .375 Winchester, I'll certainly consider it... right now I have lots of Tech Notes either in the cooker, or on the back burner.... something like getting out bullets to hunters for hunting season has taken priority :smile:

Using our .377"-250g LFNGC bullet, your .38-55 brass, and the longer COL that you have mentioned, start out with 33.0g AA 1680 and see what happens, work up as prudence leads, but this is the powder that has won all velocity and accuracy honors in my testing.

Concerning Paco Kelley's loads, I haven't fired them, and don't know about the pressures his loads generate.  Consequently,  I'm not in a position to comment on the pressures of those loads.

I think that when comparing the relative strength attributes of the Winchester 94BB and the Marlin 375, it is a moot point.  Once you get into the pressure danger levels of either one or the other, you're already treading into territory you have no business walking!  Pushing the pressure envelope, to the absolute top working pressure threshold of any firearm is foolhardy and dangerous.  I value my sight, hearing and the dexterity of my hands and limbs too much to eke out an extra 100 fps for the sake of fulfilling some number game with a chronograph!  If loading with prudence, either gun will handle sane pressures with equal safety... beyond that, well, Russian Roulette has never been my cup of tea!

Perhaps this will help!

God Bless,

Marshall
 

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Discussion Starter #5
Whatever (and whenever) you can do on the technical article will be much appreciated.  Making bullets is more important right now, agreed.

I will try working with the AA load you mention.  Have never used any of their powders.

As for hotrodding the 375 in either Marlin or BB the bottom line is that the SAAMI max should be safe in either, and that's all that really matters for the sane.  I only asked the question because Paco seems to be saying in his articles that there's some advantage in favor of the BB for heavy loads.  Personally I will stay away from these 3600fpe loads he talks about.  Even if they are safe the recoil must be tremendous and would probably require your 25lb-bag-of-shot-trick to shoot accurately.  You can rest assured that you are preaching to the choir regarding use of good sense when working up loads.  I too have a certain affinity for my natural body parts.

I will keep you updated on my progress with the 375.  My order for lapping supplies is in the mail.  I am really interested in seeing what differences I can measure in velocity and accuracy, and am trying to be somewhat scientific about it.  I found the technical guide and will try to follow your recipe as closely as possible.

And now, a couple more question if you will.  Since fishing sinkers aren't made in "375 caliber" I guess I'll have to use soft bullets for slugging.  Are your lapping bullets soft enough for this purpose, and can you provide any words of wisdom concerning their use in this role?  Secondly, you refer to obtaining air gun velocities using light loads of fast burning powders during the lapping process.  The only powder in that category that I keep onhand is Bullseye.  Can you recommend an appropriate charge for this purpose?
 
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