Cast bullets for Mannlicher M95 in original 8x50R - keyholing!!

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Last Post 20 September 2023
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cohenmj660 posted this 05 June 2023

Hi out there. I’m looking for some help with a very specific question and I have a lot of background, so my question is going to be fairly lengthy. In summary, I’m looking for why my bullets seem to be keyholing, and what can I do about it. Now the background: The firearm I’m using is a Steyr-Mannlicher M1895. It is chambered in the original 8x50R and still has the original 30” barrel. The bore looks fairly good, although it does show some minor pitting. Nevertheless, the muzzle end seems ok since a vintage military bullet only goes in part way.

First, what ammo doesn’t keyhole? I have about 40 rounds of vintage military ammo for this rifle. The headstamp shows the Bulgarian lion and indicates that they’re from 1936. The bullet is a steel-jacketed round nose and weighs in at 244 grains. There’s a cannelure near the base of the bullet into which the case mouth is crimped. I don’t know what weight or type of powder is inside. I recently went to the range and shot a 4-5” group (5 shots) at 50 yards. The hits were about 12” above the point of aim, even though I had the rear sight set as low it could go (300 Schritt). No keyholing.

Second, I have other ammo that I purchased from Gad Custom Cartridges. These are reloads made from reformed PPU 8x56R cases and have what appears to be 205 gr spire point bullets. Once again, I don’t know the weight or type of powder used. These seem to print pretty close to the point of aim using the same rear sight setting. Similar group size but no keyholing.

I measured the diameter of both of these bullets (i.e., the vintage military and the reloads) and they both measure 0.323”.

OK, now the problem. I made some reloads of my own. The cases are leftover vintage military (1936) that I decapped (Berdan) and reamed out the primer pockets to fit CCI 250 Magnum large rifle primers (I was not able to find any CCI 200 primers anywhere). The cases were full-length resized and I guessed at a charge of 45 grains of IMR-3031. The bullets are ones that I cast myself from a Lyman 323378 mould, using homemade #2 alloy (hardness measures 15) and 8mm gas checks. The bullets were sized to 0.323” (i.e., to match the other bullets that I described above). When I shot these at the range, I could barely find the holes until I saw a couple that were quite far away from the point of aim and totally keyholed.

OK, now, let’s talk about the diameter of the bullets, because this is a very common cause of keyholing. From what I’m able to read, the bore of these old M95 Mannlichers is 0.329 or 0.330”. I have read that even though the original 244 grain bullets measured 0.323” they were expected to obdurate during the firing process, thereby grabbing the grooves and stabilizing the trajectory. I have no way of knowing how much, if any, obduration either my vintage military or my Gad Custom reloads experienced. All I know is that for those two cartridge types, there was no keyholing. I haven’t yet had a chance to slug my bore.

So, even though a very common cause of keyholing is bullets that are too small for the bore, this didn’t happen with 0.323” bullets in the first two cases, only in my reloads.

So, my next question, is it possible that my own reloads are overcharged and forcing the bullet down the bore too fast for it to obdurate and grab the grooves? Does anyone have any powder data for this cartridge with a 240 grain long round nose bullet?

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Larry Gibson posted this 20 September 2023

Looking at that last 200 yard target, note the bullet holes are all round going through the target even though the RPM Threshold for that bullet in that twist barrel was exceeded. That tells us bullet stability was not the issue. As I mentioned in an earlier post we should not confuse the adverse effect of exceeding the RPM Threshold with bullet stability. Let me also say again the RPM Threshold is not a "limit". Interesting that the 200 yard group of the 1st load was smaller than the 100 yard group of the second load.

As to your first cast load with the too much 3031 powder the ill fitted cast bullets were probably borderline stabile but the too high RPM exacerbated that causing them to not only keyhole but also caused the very wide dispersion of the keyholing bullets. If you get a better fitting bullet such as the Lee karabiner and slow the velocity RPM down then you should see an improvement in accuracy.

LMG

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Larry Gibson posted this 20 September 2023

As an example of the non linear group expansion as the range in crease, here is a test conducted with the 311291 cast bullet shot with two different loads out of a .308W w/10" twist barrel.

This is the groups at 50, 100 and 200 yards with the load that is under the RPM Threshold at about 133,000 RPM +/-. Note the basically linear group size expansion as the range increases.

Here is the 50, 100 and 200 yard groups with the load that exceeded the RPM Threshold. This load was around 165,000 RPM +/. Notice the large non linear but yet still "usable" groups by many at 50 and 100 yards. Then look at the 200 yard "group" which had to be shot on a much larger target. That is a perfect example of what happens when the RPM Threshold is exceeded.

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Larry Gibson posted this 20 September 2023

First of all, the RPM Threshold of 120-140,000 RPM is not a "limit". It can be raised or lowered.

Perhaps this explanation will suffice to enlighten you on the actual definition of the RPM Threshold.

The RPM threshold occurs at a point when;

[I]the bullet is unbalanced or becomes unbalanced due to uneven obturation in the bore or canting in the bore with ill fitting bullets during acceleration. The unbalanced bullet is forced to conform while in the barrel and its center of mass is revolving around its geometric center. When the bullet is free of the barrel's constraint, it will move in the direction that its mass center had at the point of release. After exiting the muzzle, the geometric center will begin to revolve about the center of mass and it will depart at an angle to the bore (line of departure). At 54,000 RPM to 250,000 RPM, depending on velocity and twist, the centrifugal force acting upon any imbalance in the bullet can be tremendous. It will result in an outward or radial acceleration from the intended flight path (line of departure) and will try to get the bullet to rotate in a constantly growing helix more noticeable as the range increases.[/I]

"Try to" are the key words here as there are things we do (slower burning powders, harder alloys, better designed bullets, perfect fit, etc.) that we do to push the RPM threshold upward. Conversely, using a faster powder, softer alloy, no GC, etc) lowers the RPM threshold. When the bullet goes beyond the RPM threshold it does not lose "stability”. It still is flying point forward. Its flight path simply becomes a larger expanding helical one. This is why when the RPM threshold is exceeded the groups expansion as range increases is non linear.

With cast bullets the RPM threshold will be exceeded long before the centrifugal force is enough to "spin the bullets apart". Exceeding the RPM threshold becomes apparent by the decrease in accuracy as velocity increases and the non linear expansion of group size as range increases

Thus, if the RPM threshold (normally in the area of 120 - 140,000 RPM....where is dependent on numerous factors) is crossed accuracy suffers, particularly in a linear expansion of the group size as the range increases. However, as previously discussed in numerous other threads on the topic the RPM threshold can be moved up or down by varying several factors. I have thoroughly demonstrated this numerous times using a 10" twist .308W rifle, with 3 different bullet designs suitable for the purpose using #2 alloy and using slow burning powders. Pushing those bullets to 2200 - 2300 fps at 45 - 48,000 psi) at 167 - 178,000 RPM they have held 2 moa accuracy (just about the accuracy level the rifle is capable of) or less to 500 yards.

LMG

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cohenmj660 posted this 20 September 2023

Larry and MP1886, I'm finding this debate fascinating, yet somewhat hard to follow. Let me see if I'm understanding the basics here. From what I read from Larry above, there is some sort of limit as to how much spin can be imparted to a bullet, and that is in the range of 120,000 - 140,000 rpm. Is that correct? If so, what happens if one attempts to exceed that limit? Is it that the rapid increase in angular momentum of the bullet is just too high and the bullet skids across the grooves? Or is something else going on that limits the rpm? Does this limit also apply to jacketed bullets?

Going back to MP1886's example: 2000 ft/sec x 12"/ft x 60 sec/min x 1/10" (rate of twist) = 144,000 RPM. This puts the example cited by MP1886 to be slightly higher than the max 140,000. Is this what the disagreement is about (i.e., that Larry claims a limit of 140,000 RPM whilst MP1886 says he gets good accuracy even when exceeding that limit)?

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MP1886 posted this 19 September 2023

....but yet the OP with the same twist and same bore/groove diameter problem was too small a bullet and rpm, yeah right. Make up your mind Larry. We aren't talking about 6.5 Swede or 7 twist AR15. How about we agree to disagree before the thread disappears or gets closed. You want to agrue with me take it to pm's.

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Larry Gibson posted this 19 September 2023

"As I've mentioned pushed it to almost 2000fps and had zero rpm problems."

And you shouldn't have as "almost 2000 fps" out of the 10" twist of those rifles is "almost" just 140,000 RPM. The RPM Threshold is generally 120-140,000 RPM but may be pushed up some with a proper fitting cast bullet, especially in rifles with deep grooves like the M95s. Actually, if only shooting at 50 or 100 yards, respectable usable accuracy can be gotten at a bit higher velocity with cast bullets.

However, if just punching paper or plinking such velocities are not needed and not even desired many times. Higher end velocities are most often wanted for hunting and shooting at longer ranges.

LMG

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MP1886 posted this 19 September 2023

If you use 7.62x54R for the 8x56R then they are really short. The 8x50R isn't as bad. That LEE .329 bullet is not fat enough for my M95 8x56R as the groove is .330. So I got a mould for the 338 Win Mag and it sized down just beautiful and shot really really good. As I've mentioned pushed it to almost 2000fps and had zero rpm problems.

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hpbear101 posted this 19 September 2023

I have the 8x50 and a 8x56, I use the lee .329 mold in both. For the 8x50 I use 7.62x54R brass, it is slightly long you can trim to the right length or shoot them as is in most 95s. I have good luck with Herco and 2400.

Tom

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MP1886 posted this 19 September 2023

I believe 22 bullets have a wee bit of antimony in them so they swage better.

What I do is drill a hole in a well ages piece of oak that is larger then I need and use that for my mold. Then wacking it on my anvil it pops out into a towel. Then I chuck it in the lathe and turn it down to the precise size I need. That way I don't have excessive pounding. For taps and she's compressed.

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Ken Campbell Iowa posted this 19 September 2023

22 rimfire bullets are soft ... but you have to melt them all together into a worm ... if you just drop a few down the barrel your upset piece will be kinda ugly.

and watch for the sound of your tapping to change suddenly as the lead is fully compacted ... if you keep going there will be a lot of lead extruded past the tip of your undersize push rod. no big deal, but a bit ugly.

this whole procedure is actually pretty simple .. once you have done one ...

and yes, unlock the bolt and tap the sample out with a few more taps of the push rod.

oh, while tapping hold the rifle by the barrel, no use beating up the bedding of the gun.

ken

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MP1886 posted this 19 September 2023

Old fishing weights maybe, but the ones you buy today are zinc!!! If you had some Hornady round balls for muzzleloaders and cap n ball revolvers they are of soft lead.

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cohenmj660 posted this 19 September 2023

Sounds like some good advice. I will try that once I locate a good source of soft lead. Does anyone have experience with using fishing weights for a source of lead?

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MP1886 posted this 19 September 2023

Mike you make the lead cylinder as long as far as your want to measure. I usually go into the rifling a little bit as that ways I get the throat, the leade, and some of the rifling. You want to use the largest diameter rod that fit in the bore (which is the land tops, not the groove). I usually put a marker pen mark on the rod at the crown before I stop just to see how much I compress the cylinder. First start off by cleaning your chamber and bore. Put a very light finger lube of light oil on the slug. You can tell by the sound of your taps when it's fully compressed as it changes from the first taps to the last. Also you would probably have to keep tapping as your open the action as these things fit tight sometimes. For the filler in the case I use to cut off a bolt that would fit inside the case neck, but having a lathe now I make a shaft. Try to use as pure lead as possible as it compresses easier.

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cohenmj660 posted this 19 September 2023

OK, so lemme see if I understand this. I should start with a spent 8x50R case and put a spacer into the case so that there's about, what, 1/2" of space in the case mouth. Then I should make a rod of soft Pb that's about 0.300" in diameter and about how long? I can do this by drilling a hole in a piece of wood using a 9/32" drill, pouring the Pb into it and then punching out the slug out from the other end.Then I fit the slug into the mouth of the case that has the spacer in it and chamber the case.

Now what you're saying is that by 100 little taps on a 1/4" brass rod from the muzzle end will deform the Pb to the point that it takes on the shape of the throat and some of the rifling. Is that correct?

One other question - how do I get the case out? I'm picturing that if i work the bolt back the case (and spacer) will eject, leaving the Pb slug in my chamber. Does that happen?

Sound right?

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Ken Campbell Iowa posted this 18 September 2023

chamber image ... here is a copy from a post i made a few years ago ... i find the lead upset is easiest for me ... and it gives me a " loaded brass " that i keep for future reference ... i bot some lead swaging wire .. you need pretty soft lead, as in pulling the bullets from 22 rimfire cartridges. melt some 22 bullets all together in a spoon and roll or hammer that lump into a 1/4 inch round worm to insert into your test brass case.

use a brass or aluminum rod to pound so to not scrape your barrel. POUND WITH A HUNDRED LIGHT TAPS .. gives the lead time to swage ...

***********************

a simple throat check is to seat your chosen cast bullet loosely and very long ... chamber it and see how far ( or if ) the throat pushes the bullet back in the case ... that gives you an idea of the length of the throat ... it is often best to seat the bullet out as far as possible ... not always, but often.

the best ... and highly suggested method ... is to create an image of the entire forward part of the chamber including the throat and even a 3/8 inch portion of the rifling ahead of the throat. this will give you a lot of information . can/will save you weeks of random trying things that won't work .

use the search button here to look for posts on chamber casting ... chamber images ... cerrosafe ... chamber upset ... pound cast ...

cerrosafe is some neat stuff ... it melts at hairdryer temps and you gently pour the liquid into a pre-heated chamber ....stopping the flow with a wadded patch about 1/2 inch in front of the throat . let it set up and then push it back out and you can see what your chamber looks like .... you can order cerrosafe from rotometals, and you can use it over and over ... but i suggest you do a cast for every gun and store it for reference.

* pound casts * involve upsetting soft lead in the area of the front of the neck and into the rifling ... i put a spacer rod into an empty case so i don't need so much lead and chamber the case ... the soft lead should be a soft rod seated in the neck and extends an inch or better up the throat before you tap it from the muzzle with a brass or aluminum rod ( softer than barrel but don't bugger a good cleaning rod ) ... use about a hundred little taps rather than 5 giant hammer blows . this gives a good image also; i keep soft lead wire around for this purpose , you can use 22 rimfire bullets also , melted into a rod shape first .

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MP1886 posted this 18 September 2023

Mike I pushed the 8x50R's brother to 1900 fps and over in the 8x56R in my M95 Steyr. Those two rifles aren't subject to rpm problems. To name a rifle that is difficult because of it's fast twist it's the 6.5x55 Swede. Don't far into that trap friend. For as undersized as your bullets were and pushing them fast that wee little bearing surface had a hard time holding onto the rifling, nothing to do with rpm.

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Larry Gibson posted this 18 September 2023

Mike

I seriously doubt the #2 alloyed cast bullets with700X and Unique powder loads obturated much. Note it is "obturate' with regards to bullets sealing the bore not "obdurate" which has a completely different meaning.

As I said in a previous post to MP1886, "The OP, with his cast bullet, has two problems; the undersized cast bullet and pushing the bullet too fast, I.e. to too high of RPM." You solved the second problem (too high a velocity with too much RPM) with the 700X and Unique loads. When you get that bullet or, perhaps, the Lee Karabiner, to fit the throat and/or groove diameter then accuracy should improve a good deal more.

LMG

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cohenmj660 posted this 18 September 2023

Hi Larry - thanks for the training lesson on dacron fillers. I'll have to see about that once I start with loads that leave substantial space in the case, although, I have to admit, the last 6 lots that I made with 700X and Unique were pretty much empty.

You hit the nail on the head with your question about the size of the original bullet. Those bullets measure 0.323 - 0.324" at the base and ~0.320-321" right in front of the cannelure. In addition, I had read somewhere that these bullets would "obdurate" so that they would fill up and seal in the bore, which was typically 0.329". Silly me...I thought that if a steel-jacketed bullet would obdurate sufficiently to seal up in the bore, why shouldn't a lead (OK, #2 alloy) bullet do the same?

I think the whole obduration thing might be a myth, at least as far as the M96 Mannlicher goes with those steel-jacketed bullets and the pressures that those cartridges developed. This may explain why, when they reworked many of these rifles between the worlds wars they chambered them to accept the more powerful 8x56R cartridge which sported 0.329" bullets (as is sold by PPU these days) without modifying the bores at all.

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Larry Gibson posted this 18 September 2023

Mike it is, glad to meet you.

Out of curiosity, what's the diameter of that original bullet?

Here is a discussion I posted many years ago that explains what a dacron filler is and how I use it.

"I have for many, many years found dacron (polyester fill) to be the best "filler". I use a filler only when appropriate. Many think I always use a filler with every powder....I DO NOT!!!! The use of the filler can cause problems if not used correctly and when appropriate. If the powder is not correct for the bullet/cartridge combination then the filler is not going to make it "right". Many want to use a specific powder for a cartridge because the powder is "cheap" or because "they have a lot of it". There are lots of powders that are not only poor choices to use but that can be dangerous if used in an inappropriate bullet/cartridge combination. Do yourself a favor if you are wanting to use an inappropriate powder (usually "no data" available is an indication the powder might be inappropriate) and get an appropriate powder. You will save yourself a lot of frustration. The use of the dacron filler only makes an appropriate powder perform better. The dacron filler will not make a silk purse out of a sow's ear.

Also many do not understand the difference between a “wad” and a “filler”. A wad is a material pushed down on the powder to hold it in position against the flash hole. There is a gap between the wad and the base of the bullet. A “filler” fills the entire space between the powder and the base of the bullet. The filler will not move under recoil or rough handling of the cartridges. The use of a appropriate filler prevents migration of the powder through or around it.

I don't use the dacron filler with the fast to medium burning "fast" pistol /shotgun type powders. I find one of these fast burning powders that is fast enough to ignite and burn efficiently at the velocity I want and avoid using a filler with them.

I almost always use the dacron filler in rifle cases with the slower “fast” burning powders (4227, 4759, 5744, 4198, etc. with lighter medium weight bullets for the cartridge; i.e. 140 - 165 gr bullets in .30/.31 cals of 30-30 through '06 case capacity), the medium burning powders (RL7, 3031, 4895, etc.) up through the slow burning powders (RL19, AA4350, H4831SC, RL22, 3100, etc.) that give around 80% or less loading density under medium to heavy weight bullets for the cartridge; i.e. 170 - 220+ gr bullets in .30/.31 cals. Those examples are for the .30/.31 cals but the same guidance applies to other calibers. The dacron filler is used only between the powder and base of the bullet.

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 all the dacron is at the bottom of the neck or at least all in the case. It doesn’t matter exactly where just so long as you don’t tamp it down on the powder as a wad and leaved a space between the base of the bullet and the dacron.

What you want to do is push it in to let the base of the bullet finish pushing it down and adding any compression against the powder. 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. With the charged cases in a loading block I simply hold the chunk of dacron over the case mouth and push it in with the rod. It is quite easy and a lot of “precision is not required, just get the dacron into the case and let the bullet finish pushing it down.

LMG

Concealment is not cover.........

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