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Old April 8, 2010, 12:24 PM   #1
LeMat1856
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what does this mean: 1/4"-28UNF

hello all,

i recently purchased a pedersoli .58cal howdah and the box arrived without a user's manual.. surprise ! !

needless to say that left me with a few questions about loading, disassembly, and nipple size, just for starters..

gloria, the dp email rep, told me this monster uses "1/4"-28UNF" which she said was a common size.. last week i got a box of supplies and two new nipples that were "1/4 x 28" but turned to have a much shorter cone than the factory ones..

so, my question is just what do those numbers mean / measure and how can i find the correct size *before* i buy them in the future ?

i've noticed that there are other metrics for nipples so any additional information on those would be appreciated.

thanks,
~d~

ps. now that i think of it, the same thing happened when i bought a replacement for my euroarms jp murray muskatoon only that one was much longer than the factory.....
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Old April 8, 2010, 12:53 PM   #2
Doc Hoy
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As Ronald Reagan always said, "Well...."

1/4 means 1/4 inch is the diameter of the threaded part of the nipple. 28 means 28 threads per inch and UNF stands for Unified National Fine which in this case is redundant because for a 1/4 fastener, (or in this case your nipple) 28 threads per inch already is Unified National Fine. Unified National Standard (UNS) for that diameter is 24 threads per inch. Unified National Course (UNC) is 20 threads per inch.

I think the nipple will be okay for two reasons. 1) Nipples of that size will fit in your pistol. 2) The cone size should not matter on that particular pistol unless there is something special about the flame shape that is produced by the original nipple in comparison with the shorter cone. I stopped shooting single shot stuff a while ago but I never encountered a weapon that was overly particular in it's ignition characteristics.

I would try the caps you are using on both the original nipples and on the replacement nipples. If the shorter cone requires a different size cap, you will want to know that before you change out the nipples and then go shooting with the wrong caps.

Always more comforting to have the original parts but in this case, I think you are okay.

Every time the word nipple is typed on this forum I always find a way to drag my own personal preference into the conversation. Most everyone is sick of reading this but here goes.

I personally think you should take the orignial nipples out of the pistol before you shoot it. Schmootz the threads up with some kind of lubricant (Bore lube is okay) and then put the nipple back into the pistol just a little tighter than snug but not too tight. Then when you clean the pistol, clean it with the nipples removed.
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Last edited by Doc Hoy; April 8, 2010 at 01:17 PM.
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Old April 8, 2010, 03:35 PM   #3
mykeal
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The length of the cone can be important. The shorter cone will mean the hammer face will not strike the cap properly; the hammer face is supposed to be parallel with the top of the cone, and thus strike the cap evenly all around. The shorter cone means that only a part of hammer face will strike the cap. In an extreme case this could mean FTF's. It could also lead to hot gas blowing back through the nipple flash hole and escaping into the hammer area since part of it won't hold the cap down. It might even mean the hammer face doesn't contact the cap at all - the alignment might be so bad that the lip of the hammer hits the cone preventing the face from reaching the nipple.

The real dimension to check is not the length of the cone but the distance from the surface where the nipple seats against the gun to the top of the cone. The flange on the shorter cone nipple might be thicker and make up for the shorter cone.

1/4x28 threaded nipples come in several lengths; the shorter ones are generally for pistols, with the longer ones usually used on rifles. That's not always true, however. Sounds like your Howdah uses standard rifle nipples.
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Old April 8, 2010, 08:34 PM   #4
LeMat1856
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.
.

i thank you both for the info.

doc, i've been using "super lube" grease for the threads ever since i did battle (and lost) with a frozen nipple on the lemat.. they all get the treatment now.. your advice is worth repeating since i know many ppl will say "i'll do it next time..." which could very well be too late...!

mykeal, exactly what i was thinking as well.. looks like i've wasted another $8 in my education in this sport.. dixiegunworks has "real" howdah nipples for less ($2.95 x 2) which look longer so i'll try again rather than risk using these.

btw, i've gotten a few good rounds out of this beast at the range using .575 (old style) conicals and just 40-45gr fff recently.. seems to be shooting very high.

thanks again,
~d~
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Old April 9, 2010, 10:18 AM   #5
ebr-lvr
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Thanks Doc, and Mykeal. Good info that I'll remember. Good luck and congratulations LeMat on your new Howdah. I hope there is one somewhere in my future too.
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Old April 9, 2010, 11:31 AM   #6
Doc Hoy
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For all

Pay closer attention to Mykeal's post than to mine regarding the use of the nipples that the DP rep suggested to LeMat.
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Old April 9, 2010, 02:01 PM   #7
mykeal
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Just for the heck of it, here are the various nipple thread sizes commonly used today:
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