Pushing the Velocity in 8mm Mauser

[Nelsdou44]

I've been having pretty good success in shooting cast with slower powders in 308 Win (AA3100 as suggested by Nobade) so I decided to try it in the 8mm Mauser. Ran some calcs through QuickLoad that indicated a casefull would produce 20ksi behind a 175 grain pill and send it 1,900 to 2,000 fps. I've never had any luck pushing cast lead over 1,600 fps in a 9.25 twist Mauser barrel, but what the heck, I've leaded up my Yugo M24/47 barrel before, so I loaded up a set and headed to the range.

What a pleasant suprise! Not knowing exactly how true these boolits would fly, I had no trouble putting 10 rounds into a 6" bull at 100 yds and banging the gong at 200 yds with another 10. On each round fired I had been expecting it to suddenly go awry and lead up the barrel, but not so. Yahoo!

Now the 3100 doesn't burn completely and does leave some "trash" in the barrel, but it did burn cleaner than I expected. Didn't find it to be a problem to interrupt my shooting session.

I did not run these through a chrony, but I know they are faster than 1,600 fps. I zero'd in the Yugo at 100 yds using the 200 meter rear sight setting, 6 o'clock hold and 200 yds using the 400 meter setting, samo hold. Felt recoil is also more than any of my other 8mm cast loads.

I carefully examined the patches when cleaning the Yugo and found only a few very tiny specks of lead on the first two, and that was it.

I'll be back to "tune" this load some more. Finally, a potential load for my 8mm Mausers I'd consider hunting with!

Nels

[Buckshot]

..............A couple years back I headed up a GB for the above "Heavy 8", 8mm boolit. In common alloy it drops at 236grs. For some reason I felt it needed to go 2300 fps with good hunting accuracy, which for me and iron sights equates to 3" or less at 100 yards benched.

I used a M38/46 Turk Mauser with a 24" bbl. I used surplus WC852 ball (slow) powder, and started with a Grex filler over the powder. The surplus WC852 I have is about like a slow lot of 4831. I chose WC852 as I had a lot of experience with it, and had found it to be a very predictable and benign powder to work with. No sudden surprises

Toward the end of the loading/shooting tests I had deleted the use of the filler and had gone to a drop tube. Just before I ran completely out of room (and these were fully expanded, neck sized cases) I reached the goal of an average group velocity of 2300 fps. Actually 2318 fps. I was VERY happy to have been able to quit testing, and as a positive to have had it turn out such a success.

The only bad part was the fact that the brisk recoil managed to split the stock through the wrist. Recoil, rather poor inletting, and a somewhat dry stock contributed. Happily the rather nice piece of walnut the rifle was stocked in was a simple fix, and it has since been glass bedded.

..................Buckshot

[James C. Snodgrass]

Why does a case full of slow powder work so well ? I know it does I've done it myself in several different cases . I know that it is low pressure but still the velocity is up and you would think that the bullet would strip at speed . Just my observations. James

[felix]

Stripping comes from acceleration of the boolit, not its velocity. ... felix

[Larry Gibson]

"Why does a case full of slow powder work so well ?"

Not all slow powders work well. For those that do the answer lies in; loading density rusulting in more uniform ignition, slower time pressure curve during accelleration that causes less damage to the bullet and a lower velocity that results in less RPM.

Larry Gibson

[Nelsdou44]

Update:

The boolits used were 170 grain LBT design, water-quenched WW, GC'd, sized @.325" and lubed with alox/JPW mix. CCI 200 primers were used.

A point of interest from the QL program: The pressure curve generated for this load indicates the boolit is approximately two inches down the tube going about 700 fps when max chamber pressure is attained. With that said, I'd treat the data from QL as an approximation only; it assumes certain variables such as the pressure to engrave a cast boolit at 1160 psi, and so forth. But the general idea about acceleration is probably valid.

But I'm not sure what "lower velocity that results in less RPMs" means in this particular case.

Nels

[Larry Gibson]

Update:

But I'm not sure what "lower velocity that results in less RPMs" means in this particular case.

Nels

The RPM is based on velocity and the rate of twist. The slower the velocity the less RPM generated.

Larry Gibson

[Nelsdou44]

The RPM is based on velocity and the rate of twist. The slower the velocity the less RPM generated.

Exactly. To interject "RPM" in the above discussion is nonsense.

If we can agree for a given powder type, charge, boolit, and cartridge, the effects can be graphically described by a pressure-time curve, ending when the boolit leaves the muzzle.

On ignition the boolit engraves into the lands it accelerates down the barrel being pushed by a pressure pulse that rapidly builds then decays. From ignition to the point the boolit leaves the muzzle the boolit is in a state of positive acceleration, which also corresponds in a changing rate of velocity.

The shear forces attempting to "strip" the boolit material are proportional to the thrust on its base, which are causing the acceleration of the boolit.

The velocity is what it is.

Now if we could "control" the positive acceleration of the boolit to keep the thrust and the shear forces just below the "stripping level" and some how maintain that level of positive acceleration all the way down the length of the barrel, the muzzle velocity would be huge! (acceleration=0 at muzzle)

But we all know powders don't give us the ideal pressure-time curve to do that. So we make due with burning deterrents and additives to broaden the pressure pulse to get a more sustained push. And yes, there are some other drawbacks to slow powders.

So Larry, when you talk about the thresholds of RPM, it makes no sense to me.

If you were talking thresholds of acceleration, ahh, that I can understand.

Nels

[Larry Gibson]

Nelsdou44

It is Snodgrass and felix that interject the topic of 'stripping". My post was directly related to your first post. It has nothing to do with a cast bullet "stripping" accelleration. The use of slower burning powders has to do with minimising the adverse affect of obturation during accelleration.

You asked the question; ""Why does a case full of slow powder work so well ?"

I merely answered that question with; "Not all slow powders work well. For those that do the answer lies in; loading density rusulting in more uniform ignition, slower time pressure curve during accelleration that causes less damage to the bullet and a lower velocity that results in less RPM."

I believe I stated the very same thing in that answer that you did in your last post. Stripping of course is damage to a cast bullet. With many slower powders like 3100 and 100% loading density the velocity is lowered over loads with other medium or fast burning powders. The lower the velocity generates lower RPM which then has less adverse affect on accuracy.

I'm not sure where the burr under your saddle came from. My apologies for answering your question and obviously wasting both our time.

Larry Gibson

[Nelsdou44]

I'm not trying pick on ya Larry. There is an important point being overlooked here and it's not time wasted if we learn something from it. And the same for anybody else reading this post.

Quote: "With many slower powders like 3100 and 100% loading density the velocity is lowered over loads with other medium or fast burning powders"

Slower powder accelerates the boolit at a lessor rate than a fast powder. Both powders give the boolit positive acceleration, but the slower powder extends the acceleration for a more sustained duration of time. Depending what slow vs fast powder is being compared, the velocity of the boolit being propelled by the slow powder may be much higher.

It's not the velocity that's lower, it's the acceleration.

Here's a case in point between a full load of AA3100 and 13 grains of Red Dot, 8x57, same Lee 175 boolit:
Red Dot



and 3100



The red line is the pressure curve. The changing slope to the blue line (velocity) is the acceleration. The more gradual (less steep) the slope of the blue line is the less positive the acceleration is, but it is still positive. The Red Dot has a very positive acceleration early in its pressure time curve, much more than the 3100, but loses that "kick" fairly quickly by evidence that the blue line ramping to the horizontal quickly. The 3100 has less positive acceleration but keeps building for a longer duration, resulting in much higher velocity.

[Larry Gibson]

Nelsdou44

I am well aware of all of that regarding accelleration. My point is that when you are "pushing the velocity in the 8mm Mauser" (the subject of this thread, remember) and have achieved a higher velocity switching to a slower powder many times reduces velocity (and thus RPM) which is many times conducive to increased accuracy. It is many times simply the reduction of velocity and RPM that improves accuracy, not the lessoned acceleration of the bullet. Ispeaking of medium and slow powders not the fast ones like Red Dot. I did not mention your Red Dot load at all. Red Dot is a fast powder that is accurate in the 1400-1600 fps range in rifles such as the 8mm. Medium burning powders are much more effecctive to increase the velocity as are some slow burning powders. Some slow burning powders are too slow and give erratic ignition. Some are hard to ignite at lower pressures (many ball powders) and also give erratic ignition. Quick Load is nice but I suggest you chronograph that load to see what the ES/SD is. That will tell you if you have a consistant load, Quick Load will not. Quickload also can be pretty close with pressures and velocities with jacketed bullets but many times it is not close with cast bullets. The only way to know is to chronograh the load. Other than that it is just a calculated guess.

You obviously haven't read many of my previous posts or you would know that I am well aware of the relationship of pressure, buring rates and accelleration of bullets. You may also ask how I know about Quick Load not being quite correct? It is because I use both Quick Load and an Oehler M43. The Oehler M43 actually measures the pressure and gives a nice little graph of the actual measured pressure similar to the calculated ones you posted from Quick Load. I am not guessing at pressures, I am actually measuring the real pressures as they are in my rifles, 8mm Mauser included. I recently have done a considerable amount of testing of .30 cals and of the 8mm Mauser. Those tests included fast, medium and slow burning powders, 3100 included.

It is good that you think you have found a good load. However " the 3100 doesn't burn completely and does leave some "trash" in the barrel" indicates that there is not consistant ignition. Chronographing will answer that. Also your accuracy criteria seems to be "putting 10 rounds into a 6" bull at 100 yards". That is simply 6 moa and really not very good accuracy from an accuracy standpoint. Had those 10 shots gone into 3 MOA or less then you might have something. Putting 10 shots into 2 moa or less would be much, much better. If you are satisfied with 6 moa then that is ok too, I've no qualms with that. However, with regards to RPM; if you are pushing the velocity of the 8mm Mauser at 2000 fps or above that (you are above the RPM threshold) then you'd better pay attention to the effect of RPM or you not shoot any better than 6 moa.

Larry Gibson

[45 2.1]

Larry wrote this:
It is good that you think you have found a good load. However " the 3100 doesn't burn completely and does leave some "trash" in the barrel" indicates that there is not consistant ignition.

Nelsdou44-
If you fill the case up to the base of the shoulder with 3100 and put ground poly buffer up to the middle of the neck, then seat a heavy boolit on that, you will probably find that the load will be quite accurate and burn cleanly.

[Nelsdou44]

45 2.1,

I've been thinking about that same thought as well. I'd been considering modeling the cartridge as having reduced capacity to come up with a reasonable guess as to how much filler and a corresponding change in pressure. What you recommend is a fairly small amount that should be plenty safe.

Nels

[45 2.1]

I'd been considering modeling the cartridge as having reduced capacity to come up with a reasonable guess as to how much filler and a corresponding change in pressure. What you recommend is a fairly small amount that should be plenty safe.Nels

I've tried this in quite a few cartridges. It works pretty well from the 6.5 Swede up to the 8x57 capacity cases. It works perfectly in the 7.65 Arg with 200 gr. boolits. Larger capacity cases than the x57 mauser case do not work too well when a lot more poly buffer is used and can have pressure excursions in those cases. Keep in mind the pressure limit of the cartridge and rifle you try this in.

[bcp477]

Filler or buffer can be very effective in upping the velocity one gets, by effectively causing a pressure increase, beyond what would occur without the filler. For example, my current favored load uses only 28.0 grains of IMR-4064, with .3 to .5 grains of cotton wool, as filler. The load chronos in the range of 1930 to 1980 fps through my 20" barrel, using a 170 grain bullet, as it stands. 28 grains of this powder, without filler, would most likely produce significantly less velocity - I doubt more than 1700 fps (but I do not have the data to prove this). In this case, the filler is an asset - and entirely safe - because the max. pressure the load can produce is WELL below max. safe levels. The load with filler is MUCH more accurate than without. However, if my chosen load contained, say, 46 grains of the same powder, then filler would definitely NOT be safe. I cannot put forth a specification as to the max. charge with which poly buffer (or any other filler/ buffer) might be safe - I have no data to go on. As a rule of thumb, however, I would NOT recommend use of a filler/ buffer, if using charge weights are to exceed 80 - 85 % of maximum, under ANY circumstances - and I myself would likely use more like 75 % of maximum as the limit for filler, just to be cautious. It would be VERY easy to inadvertently exceed max. safe pressures, if filler is added to an already fairly stout load. One other consideration, which goes right along with this concept - there is some evidence that fillers or buffers actually increase max. pressures in a NON-linear fashion, depending on the relative level of the charge weight, vs. maximum. In other words, if a filler increases net pressure by 15 % at a load density of 70 %, for example, it is possible that the same filler (and same amount) MIGHT actually increase pressures by, say 25 %, at a load density of 80 %. This is, as I understand it, not proven; however, some testing, relating to pressure changes (and the influence they have on ballistics and operational issues) done with artillery, some years ago, seemed to bear this out.

So, the point is, when dealing with the subject of fillers or buffers - above all, be careful. ALWAYS err on the side of caution.

[Larry Gibson]

bcp477 is correct, the use of fillers does , in fact, increase presures. It also increases the burning efficiency of the medium and slower burning powders (most often but not always. Some really slow powders in smaller cases do not respond well to even the use of fillers). My rule of thumb for the use of a filler (prefer dacron and use it almost exclusively) is based on case volume. I use the same 80-85% by volume as bcp477 use for weight. (it's pretty close to the same with slow powders in small and medium cases). Basically when the volume of the powder reaches 80-85% of the case capcity I've found a filler is no longer necessary for efficient burning.

However, I've also found that even though the filler is not necessary the use of the dacron filler seems to provide a better gas seal or buffers the bullet to produce better top end accuracy. So while the filler with 80-85%+ loads may not increase burning efficiency it still provides some benifit. Of course the load still must be worked up and still must remain at safe pressure levels.

Larry Gibson

[Bret4207]

Larry, you tickled and old memory. Are you aware as to whether or not Dacron is hygroscopic, that is will absorb moisture? Hope I used the right term. I tried a Dacron fillered load years ago and got some "bloopers". My thought at the time was that the Dacron had been moist as I wasn't too sure about where it had been stored. I had some other loads put together at the same time that I used fiberglass insulation in as a filler and they worked fine, stunk to high heaven though. Any info on the moisture issue?

[Larry Gibson]

Bret4207

I've not had any problems with the dacron being hygroscopic (SP? - hydroscopic?). I live in an area where it is pretty moist - the Pacific NW, more specifically, right on Puget Sound). I keep it stored in my garage and it is nice and fluffy when loaded. Some years back I used to use the dacron as a wad (originally recomended by Lyman, Javelina and in the gun rags). It worked fine for single loading but I discovered that when the rounds with more recoil were in magazines the wad would become dislodged and powder would mitigate into and around the wad. This caused blooper shots and hang fires (click - bang). Since using the dacron as a filler I've not had a single occurance of either. I've also had some cartridges loaded for a year+ and not had a problem.

Larry Gibson

[bcp477]

I used to use dacron fiberfill, but now I've switched to cotton wool (biodegradable, smells less objectionable when fired and no chance of having it melt and stick inside the chamber or bore). If dacron is hygroscopic.....cotton is FAR MORE so. I've not had the slightest indication of a problem, although I haven't used these rounds in the field, yet. I doubt that this is or would ever be an issue, especially since the cartridges are "sealed" with the bullet lube (I use Lee Liquid Alox, which forms a nice seal in the neck of the case, when the bullets are seated). Of course, I cannot be sure that problems might not occur, if using these rounds in a rain-soaked forest.......