Cast for 7mm military rifles???

[leadhead]

Hi Guys, what do you guys size your boolets to for military
7mm's? I've always found that the bores were on the large
size .287 - .289 dia.
I have a buddy that has an old Rem 7mm rolling block, and
he's been sizing to .285 dia and it shoots great. I don't get it.
I've been sizing down .300 dia cast carcano boolets to .289
with some success and have beagled a few different molds
with the same results. Any info would be great.
Thanks,
Denny

[6.5 mike]

I had to wrap my lee 7m/m mould up to 0.291 to fit my '98 bbl 0.285/0.290.

[mooman76]

I had a few problems there. I have 2 rifles. I bought the second hoping it would work because it looked to be in better shape but it shot just as bad. Could barely get on paper2'x2' at 25y. One slugged .287 and the other .288. I finally got the better one that slugged .287 to shoot by adding a filler. The other still would not shoot any better. The one that did was shooting 1" at 25y after that.

[leadhead]

Could you tell me what your load and filler was? What bullet
were you using etc.
Thanks,
Denny

[Larry Gibson]

I've played with several M93/M95 7x57s having good bores with cast over the years and found they all had .287 - 289" groove depths. My current M95 has a .268" groove depth. Many years ago I had a nice single cavity 287405 Lovern type mould. It dropped its bullets right at .289", I hand lubed them or used a double or triple dip of LLA and they shot really well. In a moment of stubidity I traded the mould off with a rifle. Some time later I came into another milsurp 7x57 and picked up an original RCBS 28-168-FN which is also a Lovern design of sorts. Note; the current RCBS mould of that title is a nose bore rider.

With an alloy of 15 - 18 BHN the bullets drop right at .288". Since most milsurp 7.57s have very long throats the Lovern style bullets can be seated out so the GC is at the bottom of the case neck. This bullet GC'd, sized and lubed in a .288 H die is a perfect fit in my current M95 and shoots really well in the 1850 -1900 fps range over 28 - 30 gr of 4895 (depending on flavor) and a 1/2 gr dacron filler.

Larry Gibson

[mooman76]

Leadhead. I used 9gr of Red dot and the Lee 7mm GC boollet without the GC. If I remember right it drops at .287. I also used a small amount of Dacron filler. I tried Drier lint too that I heard from someone here to try and it worked the same as the Dacron.

[405]

Hatcher lists the standard nominal groove diameter for the 7x57 (military I assume) as .2855. But, like all old military calibers no telling the specs that may show up in the chambers, bores of old rifles. I have very limited experience with the 7x57 except for one piece-O-carp Ruger 77 back in the early 80s. Currently I've been getting serious with a Chilean M95 7x57 in practically unfired condition.

Like most old military rifles of that era it has a very long throat... .5", again I assume a standard because of battlefield function and the original 173 gr military ball ammo. Likewise the twist on these seems to be standard at 1:10. My Chilean specs are .276" bore and .2855" groove. So it appears it is right on the nominal as listed by Hatcher. I have a Lyman 287641 GC 160 gr bore rider mold and it drops right at .285" on the bands and .276" on the nose with a 12 BHN alloy. I run these through a .285" Lee push through sizer that barely rubs the bands and seats the gas check. I pan lube with soft BP type lube. I seat the bullet out far enough so the GC is right at the base of the neck and the nose just touches the leade (land entry) of the bore. I load with 18 gr 5744 and fluffy dacron fill. So far this has been an outstanding load in this rifle. But the rifle is in near pristine condition as is the bore so some of the success could be attributed to bore condition.

I'm sure by increasing the hardness of the alloy to 18-20 BHN... the as cast diameter might make it to .286". Also, it seems fairly common to be faced with slightly oversize bores and habitually undersize molds... I found one way to partially compensate for that dilemma is to use a gas check bullet. However, I don't think the gas check can compensate for undersize more than about .001-.002". The soft 12 BHN alloy may also help by obturation but I'm not sure of that. If I had a 7mm rifle with a .287-.289+" groove I'd think of getting a custom mold cut. Otherwise could get old, senile and long in the tooth waiting to find a production mold that drops abnormally fat bullets. :)

[leadhead]

Thats good information guys, thanks. Larry, I have that 287405 mold and also
the 287308. Both are old but they only drop at .287 dia. Is there a way to increase
the dia. buy changing the alloy? I use water quenched WW for most of my shooting
and have never had any problems until I started playing with these damn 7mm's.
Does the filler really work that well? I've never tried it, but hear alot from you on
it's benefits.
Denny

[Larry Gibson]

Adding 2% tin and casting hotter or by going to a harder alloy you may pick up as much as .001". Beagling or lapping the mould is the other way.

Yes, the dacron filler really works that well with rifle powders on the fast end like 2400, 4227, 5744, 4198, 4759 up through the slow burners when loading density of the powder is less than 80 - 85% of case capacity. Ignition consistency almost always improves with improved accuracy resulting. Less powder is needed to obtain the same velocity and psi level. If used as a filler not a wad then powder migration is prevented and hang fire problems associated with recoil affecting the powder position with rounds in magazines during firing is prevented.

Note; in lessor capacity cases when top end loads of 2400, 4227, 5744, 4198, 4759 are used a filler may not improve much. With lessor velocity/pressure loads with such powders the filler becomes really benificial.

I do not use any filler or wad with faster pistol/shotgun powders but instead find a powder that ignites readily and consistently at the velocity range I am seeking.

Larry Gibson

[leadhead]

OK Larry, How do you add the filler? Do you just pull tuffs of it
off, or do you have to weigh each one? What all works for filler?
Denny

[405]

Dacron (polyester) filler. I use it in the applications that Larry mentioned. Really easy to add to big, straight-walled cases like the 45-70s. A little more tedious in the bottle necks. I use it in bottlenecks like 30-30, 30-06 and 7x57. I don't weigh the filler. I use the low density , high loft stuff that comes in sheets that are about 3/8-1/2 inch thick.

I add powder to case then judge the length from powder to about mid-neck of the case. I then cut a rectangle that is about the diameter of the case and long enough to fill between powder and mid-neck. That leaves a long rectangle of material. I start the end into the neck and gently persuade it to enter as far as it will go. I've found that long nose tweezers really help stuffing it the rest of the way in. Once inside I thinks it's best that it retains its loft and evenly fills the space between the powder and bullet base. I seat the bullet- that's it.

If for example I'm going to load 10 rounds. I get the rough size the filler should be. I then cut, with scissors, long strips of the dacron of the width I want. Then just eyeball each cut for length until I get 10. As low density as the material is really no need to weigh each one- waste of time.

Pic is of Lym 287641, 7x57 case, filler, tweezers. BTW the piece of dacron weighs about .2 gr

[leadhead]

Thank you 405, That was very informitive.
I'll be trying that out very shortly.
Denny

[405]

Adding filler may or may not help much. Larry explained the parameters of filler use pretty well since he has both the chronograph data and direct data of actual pressure standard deviations. Adding filler to correct mismatch between bore and bullet may not do much if that mismatch is too large and the primary reason for poor accuracy. I think the gas check does more in that regard than the use of filler but have noted that the gas check can only help compensate for an undersize bullet by maybe .001"+/-. Accuracy has to do with a lot of things. One of course is good bullet to bore fit and the ability of the bullet to take spin from the rifling from the moment it starts accelerating down the bore. Another is bullet integrity during its passage down the bore- like soft bullets with short shanks and long unsupported noses that are pushed hard down an oversize bore.... I think the bullet can actually get bent or pushed out of form if the design or fit is bad. Another is the gas seal around the perimeter of the base and around the shank... if gas starts cutting up the sides of the bullet... no hope for accuracy. So- grossly undersized bullets have no hope for those reasons and for sure some more. Whether or not filler will help... maybe a little. It will help the standard deviations of pressure/velocity in some applications.

I know that in the production molds Saeco does offer a fat 7mm. I think it is about 140 gr and supposed to drop at about .288. I don't know the specifics of its design and don't know if it would work in a 7x57 military but it might ???

[Larry Gibson]

OK Larry, How do you add the filler? Do you just pull tuffs of it
off, or do you have to weigh each one? What all works for filler?
Denny

Here's how I do it, just shows more than one way to "getter' done":groner:

The “dacron” is polyester fill as commonly found in pillows and toys. It also comes in sheets called “batting”. It can be obtained very reasonably at most any fabric store.

The dacron batting comes in various thicknesses. I prefer that which is about 5/8" thick. My wife recently bought me 10 yards which will give many, many thousands of cast bullet loads. With this current batch of batting I cut it initially across the width into strips about 3/4" wide. I then "eyeball" cut 1/2" wide chunks which is close to 3/4 gr.

A smaller chunk is cut for 1/2 gr and larger for a larger amount. I've cut some chunks that weight 1/2, 3/4, 1, 1 1/4 and 1 1/2 grs and have them in a "snack" baggie stuck on a poster board above my loading bench for quick reference when I need to cut new chunks. The batting will run thin and thick throughout the sheet so I again just "eyeball it" based on the thickness of the batting when cutting the chunks.

Pretty extensive tests have demonstrated that the weight of the filler does not have to be exact, only close. What is important is that there is enough so that it “fills" the space between powder and bullet. A little too much hurts nothing but too little poses problems. That's why I have the different size "chunks" so I can use the right size for the case capacity I am filling. For example; with most medium burning powders (3031, 4895, 4064) in and '06 to function an M1 a 3/4 gr dacron filler is about right. With slower powders that give a higher loading density like 4831 a 1/2 gr filler is about right.

I use a section of .22 cal cleaning rod in cartridges of .30 - .375 cal to push the Dacron chunk inside the case just so it is all in. The 6 to 10" section gives plenty to hold onto and sufficient "feel". Merely hold the chunk of dacron over the case mouth and shove it in with the rod. Sometimes it takes a couple three pokes to ensure all is inside the case mouth. I poke the chunks in until the are at the bottom of the neck or at least all in the case. It doesn’t matter. What you want is to let the base of the bullet finish pushing it down and adding any compression. Thus I do not push it down on the powder but let the bullet do that when the bullet is seated. Using the right size chunk of dacron this method then provides a "filler" in the air space between the powder and base of the bullet.

A small length of coat hanger works for the .22-7mm cartridges and an unsharpened pencil works well for .45 cals.

Larry Gibson

[leadhead]

Thank you very much Larry for your advice and time.
I will try them out when the weather breaks.
Denny

[Uncle Grinch]

I've played with several M93/M95 7x57s having good bores with cast over the years and found they all had .287 - 289" groove depths. My current M95 has a .268" groove depth. Many years ago I had a nice single cavity 287405 Lovern type mould. It dropped its bullets right at .289", I hand lubed them or used a double or triple dip of LLA and they shot really well. In a moment of stubidity I traded the mould off with a rifle. Some time later I came into another milsurp 7x57 and picked up an original RCBS 28-168-FN which is also a Lovern design of sorts. Note; the current RCBS mould of that title is a nose bore rider.

With an alloy of 15 - 18 BHN the bullets drop right at .288". Since most milsurp 7.57s have very long throats the Lovern style bullets can be seated out so the GC is at the bottom of the case neck. This bullet GC'd, sized and lubed in a .288 H die is a perfect fit in my current M95 and shoots really well in the 1850 -1900 fps range over 28 - 30 gr of 4895 (depending on flavor) and a 1/2 gr dacron filler.

Larry Gibson
Larry,

Question on your '95 Mauser... Is that a military stock or a straight grip commercial on your 7x57? It looks sweet!

[EMC45]

I've played with several M93/M95 7x57s having good bores with cast over the years and found they all had .287 - 289" groove depths. My current M95 has a .268" groove depth. Many years ago I had a nice single cavity 287405 Lovern type mould. It dropped its bullets right at .289", I hand lubed them or used a double or triple dip of LLA and they shot really well. In a moment of stubidity I traded the mould off with a rifle. Some time later I came into another milsurp 7x57 and picked up an original RCBS 28-168-FN which is also a Lovern design of sorts. Note; the current RCBS mould of that title is a nose bore rider.

With an alloy of 15 - 18 BHN the bullets drop right at .288". Since most milsurp 7.57s have very long throats the Lovern style bullets can be seated out so the GC is at the bottom of the case neck. This bullet GC'd, sized and lubed in a .288 H die is a perfect fit in my current M95 and shoots really well in the 1850 -1900 fps range over 28 - 30 gr of 4895 (depending on flavor) and a 1/2 gr dacron filler.

Larry Gibson



Beautiful rifle!!

[1Shirt]

I use similar to Larry's method. I can sit and watch TV, and cut little squares of dac fill, (mindless work). When I do it, I usually cut about three approximate sizes of the dac that I use. 1/2", 1", 1/2", and most often use the 1/2" squares in most loadings. When I insert them, I pull thes stuff apart (kinds of fluffs the stuff up a bit), and then use what ever is handy to stuff it down thru the neck. I also do it one case at a time after charging. Sequence prevents mistakes in most cases. Have never used a filler in real small cases.
1Shirt!:coffeecom

[Larry Gibson]

Larry,

Question on your '95 Mauser... Is that a military stock or a straight grip commercial on your 7x57? It looks sweet!

That is the original stock "bubbed" into a sweet little sporter. I got the rifle for a very good price as it was just 80% done and was still in pieces. I finished the project. Don't know who started it but they did a wonderful job on the stock. I put the forend and sights on and converted it to cock on opening. I also plan putting on a small 2.5X scope. It is a joy to shoot.

Larry Gibson