Loose Sabot

In January on the other forum Grouse45 posted a short experiment about ignition of Blackhorn whilst using a sabot that 'too loose' in his rifle. Never did he experience a delay, or failure. This month, lemoyne posted on the other forum how he was shooting 3/4" groups, but the sabot was 'too loose'.

These two threads got me to thinking about how we are always reading on this forum that one needs to use a tight fitting sabot to reliably ignite Blackhorn. For about a week, i intentionally loaded the Optima using a crush rib sabot, which was a way way too loose. The sabot is so loose, i could push the ramrod down the barrel with one finger. Every day, every day, the results were about the same.









The first of the 5 shots was from a cold squeaky clean barrel. Note how a non-magnum primer was used to provide reliable ignition.

One day for the fun of it, i dumped two vials of powder down the barrel five times, to see what would happen using the 'too loose sabot'. Four of those shots made about a 2 1/2" group, the other shot was a squib.

I'm getting ready to try that. Mine will load the same way. I can load with one finger

Ron, could it be that the problem some run into with the "loose sabot" has to do with the BP they are using in combination with that "loose sabot"? For instance, if I put a Low Drag SST down my MK95, 80 gr BH, and rifle primer...I get at best 50% ignition. Change out to 250 Barnes Expander and she goes boom every time. Last time I took the Super Disc out, it was cold and I was using 200 SST, crushed rib, 100 gr BH,W209 primers, crossfire BP. 3 of 4 shots were squibs. Changed out to the MMP sabot and things went back to normal. BTW, this was not an issue in warm weather out of that gun. I know that neither of these BP were intended for BH 209, but when coupled with the right sabot I have had great success. Nothing scientific here, just observations from shooting. Thoughts?

Aquastang said:

Ron, could it be that the problem some run into with the "loose sabot" has to do with the BP they are using in combination with that "loose sabot"? For instance, if I put a Low Drag SST down my MK95, 80 gr BH, and rifle primer...I get at best 50% ignition. Change out to 250 Barnes Expander and she goes boom every time. Last time I took the Super Disc out, it was cold and I was using 200 SST, crushed rib, 100 gr BH,W209 primers, crossfire BP. 3 of 4 shots were squibs. Changed out to the MMP sabot and things went back to normal. BTW, this was not an issue in warm weather out of that gun. I know that neither of these BP were intended for BH 209, but when coupled with the right sabot I have had great success. Nothing scientific here, just observations from shooting. Thoughts?

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Exactly!

The breech plug design, if not a completely sealed ignition system will give you more problems than a loose fitting sabot. I have had those saboted bullets that load with one finger go bang every time with a good breech plug. If your breech plugs leaks, with a loose fitting sabot, in cold weather, you will not like the results.

Ron,

What breech plug are you using? In my testing with the breech plugs using my o-ring, I have had 100% ignition every time, with several different bullet/sabot combinations. If you have a tight fitting saboted bullet, you can get away with some leaky ignition if using a hot enough primer. If you have a loose fitting saboted bullet and a leaky ignition source, not so much.

The Winchester W-209 may not be considered a Magnum Primer, but it's right up there behind the Federal 209A and CCI 209M. It actually might work better than the magnums in some applications, as they are longer by around 0.005", and will actually seal better in longer headspaced rifle/breech plug combinations.

Ron, I don't think the "too loose" caution doesn't apply to us "paper punchers" who shoot right after we load without jarring the gun around. If the sabot is held against the powder charge with no more than a couple pounds of pressure and the sabot is loose enough to slide away from it after a day of carrying the gun around, even a fraction of an inch of extra space might be enough to partially empty the ignition channel of a BH209 type plug and cause a misfire.

A true experiment would be to put a overpowder card against the breechplug, drop the powder and seat the bullet/sabot. Then remove the breechplug, take the card out, replace the plug and see if it would shoot without shaking a good deal of powder back into the ignition channel.

You'd have to do this many times to get a good sample because 1/1 or 0/1 doesn't mean much.

I'm not recommending anyone do this, but you might be able to visualize what might happen with a loose fitting sabot moving back out the barrel would cause. A breechplug with a flush or very shallow concave will still be in contact with the powder unless the void is very large.

My experience with BH209 is that the seal between the primer face and the breechplug is the most important item for reliable ignition. I've had flash holes (the 7/64" part) almost fully caked with soot, but still get 100% BH209 ignition with the original Optima hex breechplug with the slightly concaved face. That's because I use a thin washer at the bottom of the primer hole. It makes an interference fit between the primer skirt and the firing pin face (but no contact with the primer face itself. This seal ensures that the primer flash is powerful enough to shoot through any soot in the flash hole, but the powder blast has no path back into the primer pocket. After two dozen shots, I can still see daylight through the breechplug even though a drill bit comes out fully embedded with soot.

Just another thought.

Interesting, busta replied while I was writing and I agree that the seal is the most important thing. Since primers are of different lengths, dimensions are critical. A tight seal with a Fed or CCI primer might not allow a Winchester primer to close the barrel or let you pull the hammer and lock it back.

Aquastang,

Which Rifle Primer are you using in the Mk-95?

Busta said:

.....What breech plug are you using?....

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The Western Powders plug. No o-ring. The firing pin bushing is shimmed so that the W209 in this plug are compressed about 0.003", when they are chambered. There is zero blow by.

To all replies: It is my belief there several myths about what it takes to reliably ignite Blackhorn. It seems these myths began, because folks were/are using breech plugs not properly designed to burn Blackhorn. Zero blow by, is more better than not; a good breech plug can overcome other issues.

ronlaughlin said:

To all replies: It is my belief there several myths about what it takes to reliably ignite Blackhorn. It seems these myths began, because folks were/are using breech plugs not properly designed to burn Blackhorn. Zero blow by, is more better than not; a good breech plug can overcome other issues.

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I completely agree. When working/experimenting on the KRB7 a few years ago I also found that as soon as the Breech plug was sealed up so I had no blowback the rifle then shot BH209 with standard 209 shotgun primers reliably. Before that even the Mag primers would not make it ignite BH reliably. I use the Rem STS 209s in mine. I don't know if they are as hot as the W209 and it don't matter to me.

ShawnT said:

ronlaughlin said:

To all replies: It is my belief there several myths about what it takes to reliably ignite Blackhorn. It seems these myths began, because folks were/are using breech plugs not properly designed to burn Blackhorn. Zero blow by, is more better than not; a good breech plug can overcome other issues.

Click to expand...

I completely agree. When working/experimenting on the KRB7 a few years ago I also found that as soon as the Breech plug was sealed up so I had no blowback the rifle then shot BH209 with standard 209 shotgun primers reliably. Before that even the Mag primers would not make it ignite BH reliably. I use the Rem STS 209s in mine. I don't know if they are as hot as the W209 and it don't matter to me.

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Shawn,

The Remington STS is right up there behind the Magnums, and right there wIth the Winchester W-209.

Hey Busta,

What do you think the coolest Standard 209 Primer is (not the ML primers)? I had thought the W209 and STS was some of the cooler primers.

My personal findings over chronograph showed that a tight bullet and hot primer gave me the tightest spread of velocity.ive never had a misfire with any quality primer or loose bullet but velocity spread grew ..

ronlaughlin said:

To all replies: It is my belief there several myths about what it takes to reliably ignite Blackhorn. It seems these myths began, because folks were/are using breech plugs not properly designed to burn Blackhorn. Zero blow by, is more better than not; a good breech plug can overcome other issues.

Click to expand...

Agree. Since I first tried BH209 over a year ago, my only misfire was with one of the first shots I took and that was before I used the washer. Since then, I went through 2 bottles of BH209 and am on the third and never had a misfire since. I just got a used Optima V2 with the standard QRBP and put a washer in there and went through 30 rounds last week with zero misfires with BH209 and sabots, 205g REAL's and a Shiloh Minie conical.

ShawnT,
I am currently using Tula LR primers. That was all that was available locally when I purchased the MK95...they work fine in any weather with the Barnes expanders. It had occured to me that the ignition issues with the SST's might be solved with a primer change or a different sabot But, I never had any plan to hunt with the SST's anyway, so I never gave it any more thought until now. What primer are you using in your 95's?

Aquastang said:

ShawnT,
I am currently using Tula LR primers. That was all that was available locally when I purchased the MK95...they work fine in any weather with the Barnes expanders. It had occured to me that the ignition issues with the SST's might be solved with a primer change or a different sabot But, I never had any plan to hunt with the SST's anyway, so I never gave it any more thought until now. What primer are you using in your 95's?

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I use the CCI 250 Large Rifle Mag primer. It was what Knight recommended to me. I have used Rem 9 1/2M and the Fed 215 too.

I use the CCI 250 Large Rifle Mag primer. It was what Knight recommended to me. I have used Rem 9 1/2M and the Fed 215 too.

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Yep, CCI is what I was looking for at the time, but primers were hard to find then. I'll probably give those a go this spring.

Aquastang said:

Ron, could it be that the problem some run into with the "loose sabot" has to do with the BP they are using in combination with that "loose sabot"? For instance, if I put a Low Drag SST down my MK95, 80 gr BH, and rifle primer...I get at best 50% ignition. Change out to 250 Barnes Expander and she goes boom every time. Last time I took the Super Disc out, it was cold and I was using 200 SST, crushed rib, 100 gr BH,W209 primers, crossfire BP. 3 of 4 shots were squibs. Changed out to the MMP sabot and things went back to normal. BTW, this was not an issue in warm weather out of that gun. I know that neither of these BP were intended for BH 209, but when coupled with the right sabot I have had great success. Nothing scientific here, just observations from shooting. Thoughts?

Click to expand...

I haven't been following his threads, so may be missing some info and the general theme, but a 100 grain volume / 70 grain weight load of Blackhorn 209 is rather small from my rifle. If every component was exactly the same, reliably igniting a 100 grain volume / 70 grain weight charge will be relatively easier than reliably igniting a 150 grain volume / 105 grain weight charge. Then, if you changed variables with the 150 grain volume / 105 grain weight charge by changing the bullet/sabot combination for a loose fit, you add a greater potential of having even more ignition issues with the larger charge, especially when hunting with such a lightly held bullet/sabot combination that is not firmly held against the powder column. The ignition of that Blackhorn powder column, and the created pressure from that ignition, follows behind that bullet down the barrel and is dependent upon that compressed seal against the column to not only consistently ignite, but to consistently propel the bullet down and out the barrel. Blackhorn goes out of their way to educate end-users on this topic, not to make claims that a loosely fitted bullet will always slide further off the powder column when hunting, or will always cause ignition and accuracy issues; but in my opinion, to make end-users aware of this particular variable that can show a tenancy for causing ignition and accuracy issues.

I do believe that from an engineering standpoint, the science, the math, the testing, and the Empircal data show that the efficiency of the burning Blackhorn powder and its resulting expanding gases, which drive the bullet down the barrel, are directly related to the looseness of the powder column and the bore to bullet/sabot fit within the barrel to confine the column of powder. Just like with a cartridge, a loose partial charge is less efficient that a full charge in its burning and expansion of the gases. Just like with a cartridge, loose tension of the bullet being held against the case neck and/or barrel rifling is less efficient than one held firmly. Having a loosely fit bullet/sabot with a loose Blackhorn powder column underneath will be less efficient in not only igniting, but also will be less efficient in its burning and resulting gas expansion behind the bullet, than if the reverse were true and the bullet/sabot was held firmly with compression against the Blackhorn powder column. All current writings and teachings within the field of internal ballistics will back this up, which is why Western Powders publishes this information to be available to end-users of their Blackhorn 209. Igniting a huge charge of black powder is relatively easy, as it is an explosive which does not burn, but immediately explodes. Blackhorn 209 is not an explosive, it burns, albeit at a reduced pressure so to be classified as a black powder substitute, but it does not explode. As a result, it is of greater difficulty to confine and ignite than black powder, and a hunter armed with this knowledge would be wise to eliminate and/or reduce any of these variables which can negatively effect the ignition and burn of the powder.

Best

Makes sense to me. Had you read the OP, you would know that i dumped two powder vials into the rifle one day, and out of 5 shots experienced a squib; also the group size of the four shots, opened up to 2 1/2".

Ive been shooting BH with a patched roundball out of the Mountaineer .32 for hundreds of shots without one misfire. Granted its a unique situation, and light (20-30grn) loads, but its standard knight bolt/breechplug, all I use are w209 primers

Only one comment about explosions verses burning. From a chemical standpoint all explosions are really very fast burn rates. Burning in the layman term for oxidation. Black powder is considered an explosive because of its rapid burn rate. Other BP subs are considered flammable solids for storage and shipment purposes.

Sorry no loose Sabot test, but here is a 45 Pb bullet test done last year.
Bore of rifle is 0.4525". So, with the same bullet and load, 3 shots each from bench with rest and bag under butt. Can't explain the 1-flyer in many target groups - maybe me.
But, I do know a slightly looser fitting bullet (for me) shoots better than a tight fitting one. Weight of my Dewey rod will push the bullet down.