7.62 x 39mm Crimp Question/ Range Report

[ar15newbster]

Does pressure increase with crimed ammo? Or does it just hold the bullet longer while powder burns to reach the pressure needed to launch the bullet. (better for slow burning powder) I'm using a starting load with H335 30.7 grns. Lymans 49th is 30.5 grns with pressure @27,400 C.U.P. using a Hornandy SP 123grn. .310" Max load is 34.5grns. @43,300 C.U.P. If my rounds are not properly crimped, what would the outcome be?
I know crimping is also used the keep the bullet in place when using guns with high recoil and semi autos.
In the attached picture the rounds in front row are roll crimped and the ones in the rear are crimped using Lee factory crimp die. I like the results from the roll crimp because it puts the case mouth closer to the center of the cannelure.
Shot these rounds at 100 yards. First time shooting my own.
The two rounds high and left are from my sks with iron sights. First time shooting this rifle. Took me several rounds to adjust the sight using the metal target. The rest are from my WASR 10 with iron sight. Second time shooting it. I'm happy with the results. I was pretty nervous about firing these rounds even though I did tons of homework. It felt good after shooting them, right up until taking a richocheted bullet to the forhead from a fellow shooter. How many of you can say that you have been shot before?
7.62x39mm.jpg
Range Report.jpg

[Waldo]

ar15newbster...

I don't have a direct answer to your question, but all of my rifle loads have been without a crimp, regardless of whether the bullet has a cannelure or not.
It was my impression that a strong crimp kept the bullet in place during heavy recoil, but I'm not sure how much of a difference it would make, pressure-wise.

Off topic...If you could, post a range report on those loads you're putting together. I just bought a bunch of 7.62x39 components, and can't find the powder I wanted to use: VV120. Considering H322 instead..

[cjskalka]

I crimp my 7.62x39 with the lee factory crimp die and havent seen any signs of pressure at all. I'm using a lighter load than you though.

[ar15newbster]

ar15newbster...

I don't have a direct answer to your question, but all of my rifle loads have been without a crimp, regardless of whether the bullet has a cannelure or not.
It was my impression that a strong crimp kept the bullet in place during heavy recoil, but I'm not sure how much of a difference it would make, pressure-wise.

Off topic...If you could, post a range report on those loads you're putting together. I just bought a bunch of 7.62x39 components, and can't find the powder I wanted to use: VV120. Considering H322 instead..

Thanks. I've been reloading for .223 and had the h335 already, but i'm looking for either Accurate Arms 1680 which is made specificly for this round or Reloader 7. IMR 4138 will be my third choice. Check out reloadersnest.com

[ar15newbster]

I crimp my 7.62x39 with the lee factory crimp die and havent seen any signs of pressure at all. I'm using a lighter load than you though.

The load i'm using is from Lyman's 49th and is the most accurate load using this bullet. It uses the most powder but has the least amount of pressure.

[Waldo]

Out of curiosity, how close to the top did the powder get when you put your loads together?

I just tried to put 28 grs into the case (WW) and it's almost to the top..a compressed load for sure.

Me getting a little bit nervous

[jb7706]

Page 63 of the Hornady Handbook 7th Ed states "...crimping can assure the proper pressure build up of slow burning powders..." That seems clear that crimped cases develop higher pressures with slower powders. It does not give any info on how much more, nor is it clear if it only affects slow powders.

There is a thread that discusses crimps and pressure at http://www.perfectunion.com/vb/showthread.php?t=35266. After reading through that it seems wise to back your charge down some and work up watching for pressure signs.

[ar15newbster]

[QUOTE=Waldo;2795392]Out of curiosity, how close to the top did the powder get when you put your loads together?

I just tried to put 28 grs into the case (WW) and it's almost to the top..a compressed load for sure.

Me getting a little bit nervous[/QUOTE

The powder is pretty close to being full , the bullet probably just touches the powder after seating. So a light compressed load . If 28grs. makes you nervous, try 34grs which Lymans max load.

[ar15newbster]

Page 63 of the Hornady Handbook 7th Ed states "...crimping can assure the proper pressure build up of slow burning powders..." That seems clear that crimped cases develop higher pressures with slower powders. It does not give any info on how much more, nor is it clear if it only affects slow powders.

There is a thread that discusses crimps and pressure at http://www.perfectunion.com/vb/showthread.php?t=35266. After reading through that it seems wise to back your charge down some and work up watching for pressure signs.

Thanks for the reply and link. You mention backing down on my load of 30.7 grs. and Lymans starting load is 30.5 grs.? I wish the range would just let me shoot rounds that are attracted to a magnet.
If you see the guy in the picture at the range , don't be alarmed , it's just me trying out my first crimped reloads.
images.jpg

[jb7706]

Another source for you to consider. Check out http://stevespages.com/310_1_130.html. Take time to read the intro to the his site before you take his recipes and run.

[ar15newbster]

BTT

btt

[Gnzrme]

Good job Michael, Sorry I couldnt be there...I would have fixed up your wound just perfect. Keep trying with the crimp and when I get back we can go shooting.

[FeelthySanchez]

Re
Q: "Does pressure increase with crimed ammo?"

A: Crimping a projectile will definitely /\ chamber pressures