1911Forum banner

Plunk Test Results

3K views 10 replies 7 participants last post by  Nick A 
#1 · (Edited)
I ran off a test batch (50 rounds) of 230 grain LRN while trying to come up with some new range rounds. After loading the rounds them to a OAL of 1.235" I ran a plunk test on them. The enclosed photo shows the results.

The very slight raised shoulder on the bullet just shows above the case mouth. The case rests just slightly above the barrel hood when dropped into the chamber. When I run the next batch I will seat the bullets a little deeper (maybe around 1.200").

I run my reloads through a Lee FCD and the crimp is 0.470".

I have the photograph of how to judge the plunk test and realize these rounds may possibly be in the "too long" group. What I'd like to toss out for discussion is this, should I take these rounds to the range and test fire them, attempt to seat the bullets just a little further in (reduce the OAL), or pull the bullets and start over again? :confused:
 
#2 ·
What do those rounds measure at the crimp? You may need a little more taper from the looks of those. I do mine at .470

Also, do you have a factory round to compare to? Use that as a control to make sure its not the barrel.

My guess is your bullets are .452 diamater and are mushrooming when you seat them that low. I seat 230gr to 1.26. The FCD should smooth that out if you have enough crimp. Its just a guess though and should be easy to prove/disprove by measuring.

Not a gunsmith but I'm pretty sure a round sticking up like that would be considered "no go".
 
#3 ·
Assuming no bulge in the case body, it might be:

Bullet interference at the freebore or lands.
or
Case mouth interference at the end of the chamber.


Put some Sharpie marker on the brass case and push that case into the barrel with your thumb,
then tap it out carefully with a dowel from the muzzle end.


See if the bullet has a mark from the bore or rifling.
or
See if the sharpie is all scraped up around the case mouth.



If bullet: Shorten your OAL
If case: Tighten your crimp 0.001" increments until it fits.


I have a Commander that does the same thing a .470 crimp,
but chambers fully with .469 crimp. All it takes is 0.001 inch.
 
#6 · (Edited)
Bullet interference at the freebore or lands.
or
Case mouth interference at the end of the chamber.

If bullet: Shorten your OAL
Nick, It appears the bullet (shoulder) was interferring with the round fully chambering. The crimp was OK (I crimp all my rounds to 0.470" and the FMJ and LSWC seated fine).

I went back and reduced the OAL to 1.200" (just where the shoulder on the bullet was flush with the case mouth) and they passed the plunk test with flying colors. The case seated flush with the barrel hood (see photo) and they made that satisfying "plunk" when the dropped in.

I must have used the wrong line in my reload file because when I loaded the first 15 test rounds a week ago I seated them to an OAL of 1.200".
 
#4 ·
I had a similar issue with one of my 1911s, it just took a little trial and error. 1st, as to the lesson you learned and I suspect most of us reloaders have experienced. Before you make 50 loaded rounds (or more) that end up having to be adjusted or pulled, make up a dummy round first and work on OAL and crimp until you get a good fit.

Loading short shouldn't "mushroom" the bullet, but using the FCD on lead loads can shave lead because of the lead bullet's slightly larger diameter. There is a school of thought that the FCD isn't necessary and some feel that it shouldn't be used on lead reloads--be your own judge. :confused:

With that, put together a dummy (no powder/primer) and work on it until you get a successful "plunk." As Nick noted, either OAL or crimp or both could be to blame, so just experiment.

Happy shootin'
 
#5 ·
Respectfully, I'm pretty sure that if you can't fully seat a round that is 1.26 with a .473 crimp (which is SAAMI spec) then your chamber needs to be reamed by a qualified gunsmith.

Again, I am not a gunsmith but I personally don't think you want to adjust your ammo to correct an out of spec chamber. That's part of the reason I asked about a factory round.
 
#7 ·
I am not trying to hijack your thread but I have seen a lot of people talking about OAL lately I am new to reloading well haven’t even gotten all of my set up yet lol. From what I have gathered you determine how deep to seat the round based on taking a measurement of a factory round then just make yours match that? But what do you do if say you are reloading a round nose flat tip, I have never seen any of those factory rounds at any local gun stores, how do you determine OAL. I mean i guess it should be the same right? Will the reloading manuals tell you for each specific load and type of bullet what your OAL should be and then you just do plunk tests to tune it to your chamber?

thanks, braden
 
#8 ·
prybra07 - use the plunk test to set the OAL for the actual bullet you are using (dont exceed max OAL). Do this with a dummy round; keep seating the bullet deeper until the round will fully seat in the barrel and drop out when turned upside down. Then make up a couple more dummy rounds and see if they will manualy cycle in your gun. If yes, then load 10 or so and go to the range and try them. Be aware, you should be starting at the starting load level and be caseful increasing the powder charge if your OAL is less than the one in the load data manual.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top