Bullet sealer?

joneb · June 29, 2019, 02:25 PM

I pulled the bullets on 7 rnds of LC 5.56x45 with a collet puller. I found these at shooting range they all had a light primer strike.

All 7 where consistently hard to pull, they had a taper crimp to the bullet cannelure. these also a black substance applied to the bullet below the cannelure.
I'm wondering what this black stuff is and if it has any adverse affects to the barrel?

I'm guessing it's a sealant, but it purpose maybe to increase case neck tension on the bullet.

Nodak1858 · June 29, 2019, 04:11 PM

It's an asphalt sealant for moisture. Although once hardened it does increase neck tension but that wasn't the intended purpose of it. If you want to take it off mineral spirits will take it off, no affects on a barrel that I've ever experienced. I've shot a bunch of mil surplus ammo with sealant haven't seen anything bad. If you want to "break" the sealant's hold, run the rounds in a seating die with it turned in just enough to seat the bullet a fraction lower. Then they'll be easier to pull.

**Unclenick** · June 29, 2019, 04:37 PM

The other names for this are asphaltum and pitch. Liquid asphaltum is still used in art as an etch resist for artists making plates for printing, so you can buy a quart of it to play with if you want to. It was originally applied by women at ammo plants wielding a small paint brush, but I'm sure it has long since been automated. It was allowed to dry and then the bullet was seated before it was rock hard.

You will find cases using the sealant are loose at the neck. That is, if you take a Q-tip and wet it with mineral spirits, as Nodak1858 mentioned, it readily dissolves the asphaltum and you can remove it from inside the neck. So if you remove it from match ammunition brass that was never crimped, a bullet then slides in and out of the neck freely. If it was crimped, that may not happen. But in match ammunition, the sealant held the bullet after it finished hardening, and that was all that held it. I have pulled down 1964 National Match ammunition and found that to be the case with it.

joneb · June 29, 2019, 05:23 PM

Thank you. I can think of a few cartridges that I would like to try this in, with some of my magnum revolver loads I find it hard to minimize bullet jump with heavier bullets.
It would be interesting to see how this sealer would effect the performance of slow burning magnum powders.

**Unclenick** · June 29, 2019, 08:44 PM

There was a claim military match .45 Auto ammo was more accurate than commercial match ammo back in the '70s, and the article I saw on it back then attributed the superior accuracy to the sealant increasing start pressure for more consistent velocity. However I've never seen any report that military match rifle ammo shot any better than commercial match. Mainly the opposite, where Federal Gold Medal Match was concerned. Federal also makes the Mk316 mod 0 sniper ammo with the 175 grain SMK for the M24 sniper system. I have no idea whether sealant is used in those or not. It would be interesting to find out.

hounddawg · June 30, 2019, 07:19 PM

Quote:

attributed the superior accuracy to the sealant increasing start pressure for more consistent velocity.

there could be something to that. Litz experimented in one of his books and found that .003 compression exhibited lower velocity SD's than ammo that used less neck tension. My own tests showed the same in .260 Rem and .223.

makes me wonder what would happen if I would size cases with a body die then seat with some pitch how they would shoot

Bart B. · June 30, 2019, 10:19 PM

Quote:

Originally Posted by hounddawg

there could be something to that. Litz experimented in one of his books and found that .003 compression exhibited lower velocity SD's than ammo that used less neck tension. My own tests showed the same in .260 Rem and .223.

makes me wonder what would happen if I would size cases with a body die then seat with some pitch how they would shoot

If .003 inch "compression" means a .003 inch diameter interference fit between bullet and case mouth, fine. That is a new term to me. A lot more than typical about .001 inch people end up with when sizing die neck diameter is about .002 inch less than loaded round neck diameter. The industry standard is the pounds of force needed pull the bullet from the case neck. There are military specs for their ammo, none for commercial ammo I know of.

Arsenal cases use an expander die in case necks making the inside diameter about .001" larger than the bullet but leaves a doughnut at the shoulder. The pitch sealant is smeared in the neck before powder and bullet go in. Bullets are prevented from going too deep in the case by that doughnut internal shoulder. The pitch hardens and its type determines the bullet pull force to pull the bullet out. Some ammo also has case mouths crimped into bullet cannelures tripling the bullet pull force needed.

Get a Lyman M neck expander die about 2 thousandths larger than the bullet then use it to expand case necks to about .010 inch short of the shoulder to form that doughnut, smear the pitch around inside then seat the bullet. A resized larger expander ball might work, too.

Military teams pulled 172 grain FMJBT match bullets from match ammo then replaced them with commercial match bullets .0004" smaller in diameter. The black pitch left in soon bonded to the bullet enough to stay in place even if the last one of eight fired semiauto once every 5 seconds. Accuracy tests showed 2/3rds MOA through 600 yards in the best 7.62 NATO chambered M1 and M14 match grade rifles with barrel groove diameters .0002" to .0004" smaller than bullet diameter.

Sources for sealant.....

https://www.hernon.com/industries/mi...ition-sealant/

https://www.permabond.com/2014/10/30...aling-bullets/

**Unclenick** · July 1, 2019, 10:07 AM

The M-dies I have are intended for both jacketed and cast bullets, so the step portion of the expander is too short to reach full bullet seating depth before it starts flaring the case mouth. The longer nose guiding portion of my .30 cal M-die is -0.0013 (0.3067"). That part is long enough. If I assume that is typical, you would have to buy and M-die intended for a .311 bullet to expand a .308 case to close to 0.310".

If you have a lathe, turn your own expander mandrel the desired diameter to use with the Sinclair expanding mandrel die body.

Those UV curing sealants look neat, but they seem to be applied post-ammo assembly, so I don't know how hard they hold. It might be interesting to experiment with an anaerobic methacrylic sealant (Loctite).

June 29, 2019, 02:25 PM	#1
joneb Senior Member Join Date: December 10, 2005 Location: Central , OR Posts: 1,888	Bullet sealer? I pulled the bullets on 7 rnds of LC 5.56x45 with a collet puller. I found these at shooting range they all had a light primer strike. All 7 where consistently hard to pull, they had a taper crimp to the bullet cannelure. these also a black substance applied to the bullet below the cannelure. I'm wondering what this black stuff is and if it has any adverse affects to the barrel? I'm guessing it's a sealant, but it purpose maybe to increase case neck tension on the bullet.

June 29, 2019, 04:11 PM	#2
Nodak1858 Senior Member Join Date: September 7, 2009 Location: N. Dakota Posts: 435	It's an asphalt sealant for moisture. Although once hardened it does increase neck tension but that wasn't the intended purpose of it. If you want to take it off mineral spirits will take it off, no affects on a barrel that I've ever experienced. I've shot a bunch of mil surplus ammo with sealant haven't seen anything bad. If you want to "break" the sealant's hold, run the rounds in a seating die with it turned in just enough to seat the bullet a fraction lower. Then they'll be easier to pull. __________________ We've all heard that a million monkeys banging on a million typewriters will eventually reproduce the entire works of Shakespeare. Now, thanks to the Internet, we know this is not true.

June 29, 2019, 04:37 PM	#3
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	The other names for this are asphaltum and pitch. Liquid asphaltum is still used in art as an etch resist for artists making plates for printing, so you can buy a quart of it to play with if you want to. It was originally applied by women at ammo plants wielding a small paint brush, but I'm sure it has long since been automated. It was allowed to dry and then the bullet was seated before it was rock hard. You will find cases using the sealant are loose at the neck. That is, if you take a Q-tip and wet it with mineral spirits, as Nodak1858 mentioned, it readily dissolves the asphaltum and you can remove it from inside the neck. So if you remove it from match ammunition brass that was never crimped, a bullet then slides in and out of the neck freely. If it was crimped, that may not happen. But in match ammunition, the sealant held the bullet after it finished hardening, and that was all that held it. I have pulled down 1964 National Match ammunition and found that to be the case with it. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

June 29, 2019, 08:44 PM	#5
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	There was a claim military match .45 Auto ammo was more accurate than commercial match ammo back in the '70s, and the article I saw on it back then attributed the superior accuracy to the sealant increasing start pressure for more consistent velocity. However I've never seen any report that military match rifle ammo shot any better than commercial match. Mainly the opposite, where Federal Gold Medal Match was concerned. Federal also makes the Mk316 mod 0 sniper ammo with the 175 grain SMK for the M24 sniper system. I have no idea whether sealant is used in those or not. It would be interesting to find out. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

July 1, 2019, 10:07 AM	#8
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	The M-dies I have are intended for both jacketed and cast bullets, so the step portion of the expander is too short to reach full bullet seating depth before it starts flaring the case mouth. The longer nose guiding portion of my .30 cal M-die is -0.0013 (0.3067"). That part is long enough. If I assume that is typical, you would have to buy and M-die intended for a .311 bullet to expand a .308 case to close to 0.310". If you have a lathe, turn your own expander mandrel the desired diameter to use with the Sinclair expanding mandrel die body. Those UV curing sealants look neat, but they seem to be applied post-ammo assembly, so I don't know how hard they hold. It might be interesting to experiment with an anaerobic methacrylic sealant (Loctite). __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

June 29, 2019, 05:23 PM	#4
joneb Senior Member Join Date: December 10, 2005 Location: Central , OR Posts: 1,888	Thank you. I can think of a few cartridges that I would like to try this in, with some of my magnum revolver loads I find it hard to minimize bullet jump with heavier bullets. It would be interesting to see how this sealer would effect the performance of slow burning magnum powders.