The UK's Finest Independent Forum for Shooters and Gun Owners. Est 2010.

A micro-grooved Marlin, contrary to general cast bullet wisdom, needs a hard cast bullet, but over sized.

Sim G wrote:A micro-grooved Marlin, contrary to general cast bullet wisdom, needs a hard cast bullet, but over sized.

I would be interested in how you came to that conclusion I assume you have personnel experience in re loading cast bullets in a micro groove.
I agree that bullet fit is critical. But hard cast bullets in a micro groove no that does not work for me. A friend of mine has spent a considerable amount of time on the range with me trying to get hard cast bullets to shoot in his Marlin micro groove with out success.
If you can offer any tips as to were we might be going wrong I would appreciate it.

dromia wrote:I wouldn't get the bevel base though just go for a plain base version.

Why is that? Assuming a plain base generally shoots a little tighter?

dodgyrog wrote:SAECO do a very similar one - my SAECO moulds always throw good boolits

Do you sell a similar bullet?

I've tried 7 or 8 cast bullets, all 158gr or lighter with mixed results, generally if driven hard they will shoot but none have been satisfactory at 1100fps or less varying from 2" @ 50 to 12" or more but this 180gr just shoots well even down to 935fps, my plinking load at 1050fps is shooting 5 into 1" or less rested at 50 and when everything aligns 2" at 100.

I don't know why it's been so much better if it's the weight/length as the lighter ones ought to be stable but it just seems to work! Come to think of it the 180gr is the only one sized at .357 all the others i've tried have been .358. I don't get any leading to speak off and it's non-micro groove. Anyway, these bullets are VERY hard and bouncy and as I'm not pushing them I don't see the need and I'd like to try some softer ones in a similar style/weight.

I have cast and loaded for a .357, .44, 30-30 and .45-70 Marlins, all in microgroove. Bullets tend to have to be two thou over, hard and driven fast. I found that a .35 Remington version shot well with heavy .358s in the 200gn range. That's not just my experience, but of a fair few of the Marlin Collectors Association. And get those boys on Marlin Owners going on microgroove and cast then you better up your bandwidth!

Sometimes the only one you can get away with is the .357, but only sometimes as groove diameter specs are listed as .3577".

farmer7 wrote:

dromia wrote:I wouldn't get the bevel base though just go for a plain base version.

Why is that? Assuming a plain base generally shoots a little tighter?

dodgyrog wrote:SAECO do a very similar one - my SAECO moulds always throw good boolits

Do you sell a similar bullet?

I've tried 7 or 8 cast bullets, all 158gr or lighter with mixed results, generally if driven hard they will shoot but none have been satisfactory at 1100fps or less varying from 2" @ 50 to 12" or more but this 180gr just shoots well even down to 935fps, my plinking load at 1050fps is shooting 5 into 1" or less rested at 50 and when everything aligns 2" at 100.

I don't know why it's been so much better if it's the weight/length as the lighter ones ought to be stable but it just seems to work! Come to think of it the 180gr is the only one sized at .357 all the others i've tried have been .358. I don't get any leading to speak off and it's non-micro groove. Anyway, these bullets are VERY hard and bouncy and as I'm not pushing them I don't see the need and I'd like to try some softer ones in a similar style/weight.

You have a Ballard .357? Firstly, nice. Secondly, ignore my stuff on micro-groove and thirdly, Cherish that carbine for a Ballard .357 is desirable!

Bevel bases are just lube collectors the bevels are supposed to help seat the bullet in the case neck, once again inappropriate jacketed bullet thinking applied to cast. If you are properly neck expanding with an "M" type neck expander then seating with a plain base is much better.

I have had a few Marlin micro grooves over the years and they have all shot very well with softish alloy 10-12 BHN, the trick I have found is to size the bullet to as close to throat diameter as seating and chambering will allow. Gas checked designs also seemed to work best.

The micro groove/Ballard discussion is a long and at times conflicting one, some get softer alloys to shoot in them others don't, if we assume that their is some consistency in the rifles manufacture then the diverging experiences should be a factor of the handloading and casting processes. Or micro groove Marlins are just finicky fecking guns.

Micro grooves should not be such a mystery to get to shoot well, the design isn't particular to Marlin, Metford rifling for instance can be called "micro groove" and it also shoots soft bullets well.

Still it is what ever works for each individual.

The hardest alloy I ever use is 18BHN for long range 303 shooting with 220 gn + bullets going at 2,300 fps. It isn't a very hard alloy but it is a tough alloy.

As in all cast bullet shooting the key is good bullet fit and that means fitting the bullet to the throat not just the grooves.

As always Adam, a full and considered contribution. But you could have just used one of your sentences in this discussion....

dromia wrote: Or micro groove Marlins are just finicky fecking guns.

Or finicky fecking handloaders.

An optimally hard lead bullet is simply one which obturates at a given pressure sufficient to seal the bore against the gases which would otherwise “cut through” the lead (called “gas-cutting”, forcing molten lead into your rifling.)

1) A bullet which is too hard won't obturate and seal the bore, because the gas pressure is insufficient to expand the base of the bullet. 

2) A bullet which is too soft at a given pressure will experience excessive base expansion and vaporization of the lead, causing leading. There is a formula for optimal bullet hardness which is simple and it is worth knowing:Optimum BHN = PSI / (1422 x .90).
Both arguments for bore leading by Hard and soft bullets may under certain bullet/Pressure combinations be deemed correct.

As always there is the theory and there is the practice as BHN is only an indicator for part of factors in cast bullets and does not measure bullet "toughness" for instance, therefore the formula only works in a certain set of circumstances.

Lee have been touting this flawed thinking in their tomes, obviously there is a relationship 'tween pressure and how the bullet behaves but the formulaic approach is only pertinent to a specific alloy which BHN alone won't measure.

With good bullet fit there is no need for obturation also I would challenge the vaporisation of the lead on the base, on all the many bullets I have retrieved shot at all pressures commensurate with the calibre I have yet to see any evidence of "vaporisation" of the bases.

This is all old fashioned cast bullet thinking you are touting which seems to have more to do with reading than with practical experience, things have fortunately moved on over the years.