Csparks1106
Member
Is there any advantage in using magnum primers in 38 special for a S&W 642. It has a 1 7/8” barrel and I didn’t know if the magnum primer would help to burn all the powder before exiting the barrel.
Magnum primers for snubby?
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ArchAngelCD
Member.
No, magnum primers are only needed for hard to ignite slow ball powders like H110/W296.
Welcome to the forum.
Welcome to the forum.
243winxb
Member
A mag primer will have a thicker cup. Less chance of a pierced primer. I use mag.
Charlie98
Member
You are probably better off finding a powder that will burn more completely in the shorter barrel.
Csparks1106
Member
I have and was planning to use Unique. It is for defensive loads only that concern me. 110 grain Sierra HP's and 135 grain Speer HP's.
gwpercle
Member
Nope , you just wasting a magnum primer. Unique does not need them.
In a pinch , if magnum primers are all you have you can use them but drop back your powder charge of Unique 0.5 to 1.0 grains to make sure the pressure hasn't been bumped up higher than you want it.
Look out for sticky case extraction....drop back charge if you encounter it.
Gary
In a pinch , if magnum primers are all you have you can use them but drop back your powder charge of Unique 0.5 to 1.0 grains to make sure the pressure hasn't been bumped up higher than you want it.
Look out for sticky case extraction....drop back charge if you encounter it.
Gary
Charlie98
Member
As much as I love Unique, it is a slower burning powder and probably not the best for light bullets in short barrels. I'll give you a caveat, however... when I was loading for .38 and .357, Unique was all I used.
Csparks1106
Member
I have used SR 7625 but I'm nearly out. I have copious amounts of red and green dot. Tite group and CFE pistol also. Would any of those be a better choice?
Csparks1106
Member
Missed that, need to work on my reading skills.
Unique is really good for that.
Yep.
Charlie98
Member
It's an interesting question. The shortest barrel I loaded .38 for was 3", Unique did OK, but I wasn't loading that light of bullet. I would probably try CFE Pistol just to see, it may have a different burn characteristic than Unique in the short barrel.
Generically speaking, what IS a good powder for light-for-caliber bullets in defensive loads?
Generically speaking, what IS a good powder for light-for-caliber bullets in defensive loads?
243winxb
Member
Titegroup or CFE Pistol (ball powders)with mag primer for 110 gr & 135 gr bullets.
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Higher velocities are obtained when not all the powder is burned before the bullet exits. If all the powder is burned, the pressure will drop to a lower level than if powder was still burning.
A magnum (or small rifle) primer will not necessarily ignite more powder. It will better ignite harder-to-ignite loads of dense, compressed, and heavily-deterred powders. Ball powders, for example, are made "slow" in burn rate by coating the powder in materials that deter combustion. These deterrents also inhibit ignition to a degree. Combined with fine granulation and compressed loads, a magnum primer sometimes helps ignition, maybe more so with a temperature-sensitive ball powder in cold conditions.
.38 Special should never see pressures that would pierce a standard primer. One problem with using more primer than you need to is they could by themselves push the bullet out of the case before the powder ignites. This was observed with some experimental primers for 9mm Luger at CCI, about which Allan Jones (CCI) wrote, "The primer's extra gas unseated the bullet while still trying to light off the main charge, producing one peak. Then the bullet retarded as it engaged the rifling, creating the second peak. Although a shooter would never notice this in a production firearm, that double hump was worrisome." The issue is also known to present with .22 Hornet when small rifle primers are used. Allan wrote about inconsistent performance, particularly with light bullets that the primer could unseat. It is solved by using small pistol primers for .22 Hornet. Small pistol, SPM, SR and SRM primers are all interchangeable by size but have progressively more force and gas volume. The bottom line is, you don't want to use more primer than necessary, and using primers off-label so to speak is ill-advised.
http://www.shootingtimes.com/editorial/ammunition_st_mamotaip_200909/100079#
A magnum (or small rifle) primer will not necessarily ignite more powder. It will better ignite harder-to-ignite loads of dense, compressed, and heavily-deterred powders. Ball powders, for example, are made "slow" in burn rate by coating the powder in materials that deter combustion. These deterrents also inhibit ignition to a degree. Combined with fine granulation and compressed loads, a magnum primer sometimes helps ignition, maybe more so with a temperature-sensitive ball powder in cold conditions.
.38 Special should never see pressures that would pierce a standard primer. One problem with using more primer than you need to is they could by themselves push the bullet out of the case before the powder ignites. This was observed with some experimental primers for 9mm Luger at CCI, about which Allan Jones (CCI) wrote, "The primer's extra gas unseated the bullet while still trying to light off the main charge, producing one peak. Then the bullet retarded as it engaged the rifling, creating the second peak. Although a shooter would never notice this in a production firearm, that double hump was worrisome." The issue is also known to present with .22 Hornet when small rifle primers are used. Allan wrote about inconsistent performance, particularly with light bullets that the primer could unseat. It is solved by using small pistol primers for .22 Hornet. Small pistol, SPM, SR and SRM primers are all interchangeable by size but have progressively more force and gas volume. The bottom line is, you don't want to use more primer than necessary, and using primers off-label so to speak is ill-advised.
http://www.shootingtimes.com/editorial/ammunition_st_mamotaip_200909/100079#
243winxb
Member
From the above link- We tested loads at both maximum normal pressures and at the starting loads (some labs calculate start loads — we shot them). Standard primers caused no ignition issues at the max load but posted higher extreme variations in pressure and velocity in the lower pressure regimes of the start loads. In extreme cases, the start loads produced short delayed firings — probably in the range of 20 to 40 milliseconds but detectible to an experienced ballistician. Switching that propellant to a Magnum primer smoothed out the performance across the useful range of charge weights and completely eliminated the delays.
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These pocket pistols are what they are: first and foremost, lightweight concealable pistols. The frames are aluminum and trying to turn this into a 357 Magnum is a very bad idea. Don't be surprised if the OP crack's the frame, ruins the timing, in an attempt to increase the velocity in his pistol. You can't change the laws of physics with primers. It would seem best for the OP to stick to factory ammunition.
For his little pistol, I recommend going down to the local gunstore and buy a box of premium +P 38 Special ammunition, shoot a couple of rounds, out of the over priced 20 round box, to verify everything goes bang, and put that in the cylinder when you carry the pistol. At the range, shoot 125 grain standard pressure 38 Special ammunition, because S&W adjusts the sights on these things for 125 grain bullets. Older snubbies are adjusted to shoot to POI with 158 grain bullets.
For his little pistol, I recommend going down to the local gunstore and buy a box of premium +P 38 Special ammunition, shoot a couple of rounds, out of the over priced 20 round box, to verify everything goes bang, and put that in the cylinder when you carry the pistol. At the range, shoot 125 grain standard pressure 38 Special ammunition, because S&W adjusts the sights on these things for 125 grain bullets. Older snubbies are adjusted to shoot to POI with 158 grain bullets.
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ArchAngelCD
Member.
I agree, my .38 Special +P ammo even for short barrel revolvers is made with powders like AA#5 and HS-6.
ArchAngelCD
Member.
Do you really feel pressures generated by .38 Special ammo will pierce a standard SPP? I do not.
243winxb
Member
Tolerances- Firing pin protrusion. Shallow primer pocket. Primer length. *Rim thickness and headspace.* Tolerance stacking may produce a primer face flush with the case head. If you dont clean pockets, a primer may be sitting a little high.
Had to replace the hammer nose on my old M28 because of gas cutting from pierced primers. Makes a tiny pin hole that is almost invisible. 1 or 2 every 1000 rounds, it adds up. Doesnt happen with mag primers.
Not a pressure thing.
Edit add* Rim thickness & headspace.
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Csparks1106
Member
I appreciate the responses. I have no intention of turning this into a 357 magnum. This is actually my daughters gun and I was just curious about the muzzle flash and unburned powder. Her practice loads are cast wad cutters and semi wad cutters. It seems I had read somewhere that magnum primers helped, but I also know they can change the pressures.
243winxb
Member
Unique will work for both.
But, note that Alliant no longer posts current data with 158 gr jacketed bullets using Unique.
Csparks1106
Member
I’ll have to look but I think my Lyman cast book shows Unique for the cast loads. I do have some Nosler 158 hollow points but I’m not sure if Nosler’s data lists Unique.
The best way to reduce muzzle flash is to use a powder with flash-suppressant in it. There are many such powders these days. I don't think Unique is among them, though. Reducing the total mass of powder will also help - faster, smaller charges simply generate a lower volume of gas to light up upon exit.
ArchAngelCD
Member.
I agree, there are several powders available with a flash suppressor additive. The fairly new BE-86 is a good example and it seems to be very versatile too. ZIP and AA#2 are other examples of low flash powders.
Personally I use a lot of W231 and really don't notice and flash from several snub nose revolvers.
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