Winchester 748 issues

C

cjclemens

New member
Last weekend, I shot some .223 test loads through a new upper I built. At the end of my range session I proceeded to unload some leftover test loads from a previous test session. In that group were a few loads that consisted of 50 grain Varmint Grenades over Winchester 748 powder. I shot 2 out of 4, and my rifle jammed. I stopped and cleared the FTE, and noticed that the 2 I had fired were showing some severe high pressure signs. One had popped a primer and had significant brass flow around the ejector. The other one just had a nasty ejector swipe. The primer was still in the case, but it fell right out while handling the brass. I pulled the bullets on the remaining 2 rounds. When I went to dump the powder out, it was extremely chunky. I had to stick something into the case to break up the clumps just so I could dump the powder out.

I was shocked to see high pressure signs like that, because these were literally loaded and fired earlier this year and showed no such signs. My question is: just how temperature sensitive is winchester 748? It was a warm day (mid 80's), but I was sitting in the shade. My rifle was a little on the hot side, so I was wondering if this could have been caused by those rounds sitting in a warm chamber for a few seconds before firing.

Last, but not least, what could have caused the clumping of the powder? 50 grain Varmint grenades are fairly long bullets, so the loads were lightly compressed. Is the clumping just an artifact of the compression and could it have something to do with the sudden high pressure signs I had?

I've never had great luck with 748 so, once I use up what I have, I probably won't be buying any more. However, I'd like to know more about what went wrong here, so I don't pop any more primers in the future.
 
The load was probably overly compressed with too much powder.

Check water capacity of your brass. And have someone put your load data in Quickload
 
How many grains powder were you putting in the case? You might weigh the cases. I've seen 223/5.56 cases weigh everywhere from 92 grs to 106. The heavy ones would have noticeably smaller case capacity. A load worked up in a thin walled case may be an overload in a thick walled case. If you worked up the load in the winter under cold temps then 80* would be enough to cause increased pressure. That happened to me on a 40gr Sierra HP bullet with 748 worked up in the cool winter (40s) but blew a case head in July under rapid fire on picket pins. I had been following the advice of Bob Hagel a shooting/hunting writer who advocated max loads. Well, his book cost me a new bolt on my Rem 788.
 
Originally Posted By: ackleymanSimple, your load is too hot.

Use thick cup primers

Right - I noticed that. I was just wondering what might have made them shoot OK one day and be too hot a few months later.
 
Originally Posted By: HellgateHow many grains powder were you putting in the case? You might weigh the cases. I've seen 223/5.56 cases weigh everywhere from 92 grs to 106. The heavy ones would have noticeably smaller case capacity. A load worked up in a thin walled case may be an overload in a thick walled case. If you worked up the load in the winter under cold temps then 80* would be enough to cause increased pressure. That happened to me on a 40gr Sierra HP bullet with 748 worked up in the cool winter (40s) but blew a case head in July under rapid fire on picket pins. I had been following the advice of Bob Hagel a shooting/hunting writer who advocated max loads. Well, his book cost me a new bolt on my Rem 788.

I'm thinking this is probably the best explanation. However, It wasn't winter when I shot these last. It was more like early spring. I'm thinking the temps were in the 50's or 60's. I know 748 is temp sensitive, but I didn't think it would do that. Now that I think of it, the chamber would have been fairly warm from shooting other test loads. It could have easily been over 100*F in there, and each cartridge might have been in there for 15-20 seconds before I pulled the trigger.
 
Welcome to temperature sensitive spherical powders! I had a very similar experience with H-380, in a 22-250. Loaded, and tested in the Spring, at 45-60 degrees(no signs of pressure), and checked Zero at 85 degrees, to dispatch Summer varmints, and blew out primers, and had to hand pound the bolt open on a Savage action. I checked the load, and nothing changed(charge weight, seating depth, etc), from the rounds fired the previous Spring...I still have the partial canister of H-380, and it needs to be disposed of, because I won't load with it again.

Squeeze
 
CJ, what was your load. I have shot a couple of cases of 748 on dog towns, never had any problems. I shot 50 and 55g bullets, always used 7 1/2 primers.
 
Reloading manuals vary greatly in what a max load is. I usually find what is the max load for that particular barrel and my lot# of powder in the 75* area, then back off one grain. This has proved to be safe on p. dog towns at 95* temps, but let a round cook in a hot chamber and all bets are off.
 
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Originally Posted By: ackleymanCJ, what was your load. I have shot a couple of cases of 748 on dog towns, never had any problems. I shot 50 and 55g bullets, always used 7 1/2 primers.

I don't recall the exact load, but I was working out of the Hornady's 7th edition which is, as best I can tell, fairly conservative when it comes to max load values.

As I mentioned before, I'm thinking I was working with a near-max load at 50* F, and baking them in a hot chamber for a few seconds on a hot day was enough to put them over the top.
 
Everybody has miles that vary.

I label every single batch of ammo i make in great detail. From how many firings on the brass to the lot number of powder. I also keep all that information in a separate note book with test results. These days an excel spread sheet is better.

Ammo temperature is an interesting study. Keeping ammo on the dashboard in the sun will definitely cause differences in ammo pressures and velocities, compared to sitting in the shade. More extreme results with longer ranges.

A bullet chambered for a normal aim and fire session will not have that extreme effect. A bullet sleeping in the chamber after abnormal high round count shooting will have higher pressures and velocities

Its too bad you did not weigh your powder charge after the pull. Or have any information on how much powder was in there. Paying attention to this stuff is responsible.

It seems to me that load was much more than lightly compressed.

I have heard of people seeing pressure signs from stored hand-loads. It is thought that the salt and moisture from your fingers during the process causes corrosion between the bullet and the case and therefor welds them together. That is not likely in 6 months. 2 years or more in the south land though maybe?
 
Originally Posted By: arlaunchEverybody has miles that vary.

I label every single batch of ammo i make in great detail. From how many firings on the brass to the lot number of powder. I also keep all that information in a separate note book with test results. These days an excel spread sheet is better.

It was labeled initially. Since I had already shot others from the same batch in a previous range session with no issues (other than poor accuracy), I consolidated them with other test loads so I could take them to the range and unload them. If I went through my notes, I could look up what was in them - I just figured it was kind of a moot point now.

Quote:Ammo temperature is an interesting study. Keeping ammo on the dashboard in the sun will definitely cause differences in ammo pressures and velocities, compared to sitting in the shade. More extreme results with longer ranges.

A bullet chambered for a normal aim and fire session will not have that extreme effect. A bullet sleeping in the chamber after abnormal high round count shooting will have higher pressures and velocities

The barrel was definitely hot to the touch, but not blazing hot like you get after a mag dump. The cartridges weren't in the chamber very long either.

Quote:Its too bad you did not weigh your powder charge after the pull. Or have any information on how much powder was in there. Paying attention to this stuff is responsible.

I can still do that. I haven't dumped them into the discard jar just yet. I can also check my notes to see what they were originally supposed to be. Again, I didn't think that would be necessary, since they shot OK the first time around. I'll do this as soon as I get home, since a few people have asked about the load I used.

Quote:It seems to me that load was much more than lightly compressed.

That's entirely possible. I didn't feel any extra resistance when I loaded them, and I didn't see any marks on the bullet that would indicate it, but I suppose its still possible.

Quote:I have heard of people seeing pressure signs from stored hand-loads. It is thought that the salt and moisture from your fingers during the process causes corrosion between the bullet and the case and therefor welds them together. That is not likely in 6 months. 2 years or more in the south land though maybe?

These were still clean and in good condition. I actually wear nitrile gloves when I reload to keep my brass and bullets from tarnishing. I hate to handle that shiny, clean brass with bare hands, unless its time to stuff it in a magazine.
 
748 is notorious for going crazy in teh heat. The High Power boys recognize this and if the do use it here in Phoenix they will have "summer" loads and "winter" loads. Winter is 40-70 degrees 4 months and Hot as Hades the rest of the year. I'll shoot next Thursday and it will be in th 114-118 level.

No matter what the powder we avoid letting a round cook in the chamber. When I taught my snipers in FLA and LA I always had to get on them about letting that stuff cook. Not bad at 100 yards but when you stretch out bad things happen. In that business bad things are really bad. They carried extra ammo in their pockets rather than laying a box out in the sun. Here I always shade my cartridges. If they are too hot to pick up they are too hot to shoot consistently.

Greg
 
I am very interested to learn everything i can from this experience. There are those who reload and blow primers and there are those who do not reload.

Factory ammo can blow primers out to i have heard.

LoL

All learning. All good.

Thanks for this post and putting the info out there. What type of primer were you using?
 
Originally Posted By: HellgateI had been following the advice of Bob Hagel a shooting/hunting writer who advocated max loads. Well, his book cost me a new bolt on my Rem 788.

WHERE did you find a new bolt for your Rem 788??
 
Ok, so I weighed the charges from the pulled loads. The leftovers consisted of one from each charge I used. The ones I weighed happened to be my minimum and maximum charges - 26.6 grains and 27.5 grains respectively. That means the ones that popped primers were 26.9 and 27.2 grains. Max charge for a 50 grain projectile in the Hornady book I used is 28.3, but the varmint grenades are a much longer bullet, so I tried to stay well under max. Maybe this was more compressed than I thought - but that still doesn’t explain why I didn’t see pressure signs the first time.

I’m not afraid to pop a primer or two, as long as that’s my worst mistake. I just prefer to learn something from it so I don’t do it again. That’s also why I posted it in here. If I did something stupid, I expect y’all to call me out on it.
 
Danno,
I Cracked the rim of the bolt face when prying out the seized brass case head. I called Remington and asked if I could buy a new bolt and they said to send them the rifle because they had to be sure it was properly headspaced. This was back when they were still making the 788s. I think I paid a little over $200 for it brand new.
 
Originally Posted By: cjclemensOk, so I weighed the charges from the pulled loads. The leftovers consisted of one from each charge I used. The ones I weighed happened to be my minimum and maximum charges - 26.6 grains and 27.5 grains respectively. That means the ones that popped primers were 26.9 and 27.2 grains. Max charge for a 50 grain projectile in the Hornady book I used is 28.3, but the varmint grenades are a much longer bullet, so I tried to stay well under max. Maybe this was more compressed than I thought - but that still doesn’t explain why I didn’t see pressure signs the first time.

I’m not afraid to pop a primer or two, as long as that’s my worst mistake. I just prefer to learn something from it so I don’t do it again. That’s also why I posted it in here. If I did something stupid, I expect y’all to call me out on it.

Just because the book says that is max, that doesn't mean squat. Your rifle versus the test rifle could be different in many respects, how tight is the chamber, how much freebore, what brass, what seating depth, and on and on.
I have been using 748 for nearly 30 years, I have never had a primer blow out on an AR15. In fact, I have never blown a primer except with an AR10 that was way over gassed. The load was not high, but the bolt was opening under pressure leaving an unsupported case head. Off the top of my head, 27gr seems like a very stiff load. I have never compressed the powder with 748.

Sounds to me like a simple case of too much powder stuffed in the case.
 


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