Blown primers with H110?

[pomofo]

I seemed to have to some trouble today with some handloads loaded with H110. I started off with 110 grain VMax seated to an OAL of 2.050", and with 17.9 grains of H110, 1 of the 3 cases ejected with the primer blown out (found it in the bottom of my brasskeeper.) Since the other 2 cases didn't show any pressure signs, I dismissed it as a fluke, and fired 3 rounds with 18.2 grains of H110. Same thing, 1 of the 3 cases blew the primer. So, I put that aside and started with the 125 Sierras, loaded to 2.050", and when I hit 17.8 grains of H110 I got the same thing, 1 of 3 cases blew the primer. Then I tried the Lapua HPCE 100 grain on top of 17.6 & 17.9 grains, and that did just fine, go figure.

Relevant data:
Model1Sales upper
16" barrel
Carbine-length gas system

Brass: 221 Fireball, virgin, necked up with Redding dies
Primer: CCI 41 (to prevent slamfires)
Powder: H110
Temperature: about 70, indoor climate controlled range

These powder levels are WAY below max, Hornady lists a max of 20.4 grains for the 110 VMax, and Sierra lists 19.0 for the 125 SPT. I run all my loads through Quickload too, and each of these showed up at around 41000PSI. I know H110 has a reputation for being temperature and density sensitive, but it was indoors and these loads filled 87-92% of the case. The only thing I can think is that maybe the pressure was still too high while the bolt was unlocking? There's no really noticeable bulging of the case head, I'll have to measure the expansion, but the primer pockets are all so loose that I can just drop the blown primer into the pocket.

Should I chalk this up as a fluke and keep going? Or try different powders, like AA9 or AA1680?

[Colohunter]

I surprised that you are having so much of a problem, especially without using max loads. But I would suggest you stop right there. If it is in fact enlarging the pockets I would say it isn't just a fluke.

I ended up with one blown primer with H110. But I had worked up to the max load with a 125gr Sierra SPT. I didn't have any pressure problems until I got to the final five loads that I had loaded at the max. They all fired and ejected fine, but one had a blown primer so I backed down to the previous load and left that as my 125gr. That leaves me with a 125gr bullet at a little under 2200fps.

I just to compare, I am also using a 16" M1S upper with a carbine length gas system.

[pud-knocker]

Model 1 tight bore.....

I had one that measured .3065

As I approached 18 gr of H110 got the same results....

My SSK, Olympic, and PacNor could be driven much harder before pressure signs appeared, but they all slug check .308

[Art]

I had similar problems with a Model 1 barrel.

Check the OAL that the chamber will take with your bullet, mine was way short.

Check the headspacing of fired rounds, mine needs the Redding die almost 0.030 off the shell holder. My chamber will take a 1.410" case, I use 1.400" max. 221 Fireball brass gives ~ 1.650" max.

Check the magazine feeds well by ejecting a few cycled rounds before you fire them. The cheap mags set mine back. Bushmaster and Colt work fine for me.

The bore was rough rough rough. I fire lapped it with a Midway kit and the problems went away. Pressure signs gone, velocities up, SDs down.

I'm using a JP adjustable gas block with 125 gr TNTs because it's overgassed with supersonics.

My current favorite load is 19.5 gr IMR 4227 @ 2.120" OAL with Winchester or Lake City brass holding 26 gr water. Primers are still round at the edge, and case head expansion is minimal even with a large chamber. 2150 fps, SDs in the low teens.

Most of the ideas for this came from this board. The fire lapping was the big change.

[pomofo]

Yeah, I have a tight throat, but that only affects the big bullets (150+). I've fired 147 grain M80, 168 grain Prvi Match, 175 Berger VLD, and 220 grain Hornady RN, all over Acc. 1680, seated to the max length I could get in my chamber, which with the spitzers was up to 0.1" less than in the load books. I knew I'd have to download from book data, so I ran the data through Quickload to get loads up to 50K PSI, and all of those went off without a hitch. Since the short loads are so short that the bullets are nowhere close to the lands, I figured book data would be sufficient. Guess I was wrong. But I'll definitely take a look into fire lapping or an adjustable gas block.

[jefflaw45]

I too have a Model 1 Sales upper.. 15gr of h110 behide a 150gr Remington PCL bullet seated to AR-15 length is about all I can go safely..

I get about 2000 fps with that load..

any more and I get blown primers loose pockets etc

My brass measures 1.360-1.363 when formed.

Bore doesn't appear rough, but haven't slugged it to measure constriction

[320pf]

Originally Posted by jefflaw45

I too have a Model 1 Sales upper.. 15gr of h110 behide a 150gr Remington PCL bullet seated to AR-15 length is about all I can go safely..

I get about 2000 fps with that load..

any more and I get blown primers loose pockets etc

My brass measures 1.360-1.363 when formed.

Bore doesn't appear rough, but haven't slugged it to measure constriction

Jeff,

Here are the reloading data from the SIERRA and HORNADAY reloading manuals for 150 gr bullets. The preformance of your load is not too far off from what one would expect. M-1 chambers tend to run a bit tight so your pressures come up with a bit less powder. So if you are getting ~2000 fps you are doing OK. That is about as much velocity that you can get with a 150gr bullet.

I have posted my reloading data on Reloaders Nest. Most of the loads listed under the "Not yet verified user loads" heading are mine.

http://reloadersnest.com/frontpage.asp?CaliberID=135

Here are the Sierra data. These data are from a 10-inch barrel. A 16-in barrel runs abou 230 fps faster.
150gr
Powder/Velocity--1400----1500---1600---1700---1800
AA-No.9 ----------12.4---- 13.4--- 14.4--- 15.5
2400 -------------13.4----- 14.1--- 14.8--- 15.7
Viht N110 --------11.8-----13.0--- 14.2----15.4-- 16.5
H110 -----------------------13.8--- 14.8--- 15.9-- 17.0
296 -------------------------13.8--- 14.8--- 15.9-- 17.0
Viht N120 --------15.1-----16.3----17.5--- 18.7
AA-1680 ----------14.7----16.0--- 17.4--- 18.8

Here are the Hornaday data. These data are from a 10-inch barrel. A 16-in barrel runs abou 230 fps faster.
150gr
Powder/Velocity--1500----1600---1650---1700--1750-- 1800-- 1850
2400 --------------12.9--- 13.7--- 14.2
AA-No.9 ----------13.0--- 13.9--- 14.3
Viht N110 --------13.1--- 14.3--- 14.9--- 15.5
296 ---------------13.2--- 14.4--- 15.1--- 15.7--- 16.4-- 17.0
H110 ------------ 13.5--- 14.6--- 15.2--- 15.7--- 16.2
IMR4227 --------- 14.4--- 15.3--- 16.1--- 16.6--- 17.0-- 17.4
AA-1680 --------- 15.9--- 17.0--- 17.6--- 18.2--- 18.8-- 19.4-- 20.0

I hope that this helps

320pf