Reloading .303 British with LR Magnum Primers?

[loose noose]

Just recently started reloading for the above cartridge (been reloading for over for over 45 years), and came across my once fired Sellier & Bellot .303 empty casings.

After re-sizing the cartridges, getting the proper OAL, and cleaning out the primer pockets, including using my reamer, etc. I noticed that the CCI large rifle primers would not insert properly in the pocket (protruding too far out "high primers").

Just before discarding the prepared cases, I tried some Winchester Large Magnum Rifle primers I had on hand, and with quite a bit of effort managed to get them inserted properly.

My question is using a Sierra 174 grain .311 HP BT bullet and 39.5 grains of H335 powder (note the max listed in my Hornady Reloading Manual is 41.0 grains starting is 38.0 grains), with an overall length of 3,075. Will the pressures be too high in my recently acquired British Enfield No.4 MK2 in excellent condition. I generally use the recommended loads, however that Sellier & Bellot brass is garbage as far as I'm concerned.

Any comments would be greatly appreciated, prior to shooting any of this ammo in my rifle. Note I have used Remington Brass with this same load data with out a problem the only variable is the magnum primer.

 

[ArchAngelCD]

Since you are not at the max charge you will be fine with magnum primers. They only burn slightly longer and slightly hotter, not create a nuclear explosion lol.

Now to why are the primers high. Are you sure the primer pockets on that brass aren't crimped? Many military cartridges have crimped primer pockets or staked pockets that have to be addressed before you can properly seat or even install a new primer. Take a look before you go further.

 

[loose noose]

Arch Angel, I did clean the primer pockets as well as reamed the pockets with my electric reamer, as I've had problems using once fired Sellier & Bellot 9mm brass with that red sealer on the outer edge of the primer pocket. Sure can't figure out why the magnum primer would actually fit, and the standard primer would not. Well the magnum primer went in awfully hard, but at least stayed flush and undistorted. Note I've been using a Lee Auto Prime, as I use my single stage RCBS Rock Chucker press when doing rifle cartridges. Thanks for the word of encouragement in using the magnum primers, never go near maximum loads on Military firearms.

 

[homatok]

After FL sizing, if you measure the depth of the primer pocket, you will notice that it is shallower and has lost some depth. When cold worked, brass does indeed expand in all directions, front and rear. Therefore, to restore the primer pockets dimensions and depth, it is a good idea to routinely clean them out with a pocket uniformer. You will find that it shaves out a little brass every time.

 

[Ifishsum]

The difference in fit was more likely due to the difference in brand than it is magnum vs std primer...it's been a while back but I have also had rifle brass that primed easier with Winchester than with CCI - I think it may have been S&B as well now that I think about it. Not necessarily a bad thing, just a difference. They may also loosen up a bit after a couple of loads and get easier to seat. Truth be told I almost always use magnum primers with ball powder anyway so I wouldn't think anything of it.

 

[elwoodm]

the same goes for me always use mag primers with ball powders. did some BLC-2 in 303 that did not burn well and made a mess of un burned powder all over my no.4 :banghead:

 

[loose noose]

I thank all of you folks that responded it sure puts my mind at ease, I didn't think it was rocket science, but ever since I started reloading, I've always used as close as possible to the components that were recommended. I don't have any Winchester LR standard primers at hand but I just might try finding some as I've got another box of S&B brass. The H335 powder is very clean burning, in my other loads, so I didn't see any reason why a magnum primer would clean up the unburnt powder.

My first inclination was that the primer pocket was out of round/sync so I used my Lyman electric pocket reamer , but that didn't work either, checked the depth and it was the same depth as the Remington brass. Definitely had me going there. Incidentally about all you can buy around here is CCI primers for some reason.

 

[ArchAngelCD]

All I can add is, it's possible the pockets are just not the same exact size as those produced in the USA. Maybe try an inexpensive primer pocket uniformer tool which I have a feeling might fix the problem.

http://www.midwayusa.com/product/1064338732/lyman-primer-pocket-uniformer-tool

 

[WelshShooter]

I've used PPU and Sellior & Bellot brass and found that Fiocchi, Federal and CCI large rifle primers would seat with no issues. I've not tried magnum primers so cannot comment on that.

Generally, if I'm swapping between components on a known good load that I've generated, I've backed off by a grain and worked my way back up. The key to .303 British is maintaining low pressure to ensure good lifetime of the brass. The result is just neck sizing the brass and reduce the unecessary full length sizing which will lead to case-head separation. I would recommend buying a broken shell extractor for this calibre as you will need it sooner than later, especially for S&B brass which is notorious for case-head separations.

I found that Ramshot Big Game and 174gr PPU FMJ bullets make for a very nice load. With the standard sights I've achieved 2" groups at 100m and have managed to hit "man-sized" targets at 900m too.

 

[W.E.G.]

If somebody has credible evidence that magnum primers make any difference whatsoever in chamber pressure, I'd be interested to see it.

 

[WelshShooter]

If somebody has credible evidence that magnum primers make any difference whatsoever in chamber pressure, I'd be interested to see it.

Not magnum primers per se, but some evidence that primer brand makes a difference.

http://www.300blktalk.com/forum/viewtopic.php?f=141&t=97658

The link shows the same load where only the primer brand was changed between each load. The results show that for small rifle primers the Remington7.5 primers produced a max velocity increase of 50fps when compared with CCI 400 primers. This is relevant for .300blk using W296 powder. I suppose the results could differ based on calibre and powder used.

Doesn't really answer your question W.E.G. but some data is better than none. 10 shots per group isn't a statistically large sample size. One thing I've noticed, which is repeated in the above, is that you can reduce your Extreme Spread when using a magnum primer versus a standard primer (within the same brand of course).

However, it's good solid advice to work your load back up whenever you change one component even if you suspect there might not be a problem.