30. Carbine... over pressure?

floriosean1

floriosean1

CGN Regular
Rating - 100%
25   0   0
Location
uxbridge
I purchased a universal m1 carbine and decided to do some loading for it. Using cci small rifle primers, 110 gn projectiles from frontier and 13.0 grains of 2400. Lymans reloading manual says 13.5 is a max load so i figured 13 would be safe.

I fired 5 shots through my chronograph and averaged 2141 fps which is almost 300fps faster then the manual says i should get. Also all the primers are heavily cratered, but i see no other signs of over pressure around the primer or on the case.

I've been reloading for 7 years, i reload pistol rifle and shotgun, but if you can believe it I've never dealt with over pressure. What do you guys think? Any advice is welcome.
 
Reloading 101 is that you work loads up from the minimum load listed. Go up until you either hit the listed max, get the accuracy and or velocity you are after without any high pressure signs. You will find that you won't always get to the maximum listed load without high pressure signs, it does happen. Never start out at or near the maximum listed load! Kinda surprised you have not run into this in 7 years of reloading, I've maxed out with high pressure signs a number of times before hitting the listed max.
 
crashcollins said:
Reloading 101 is that you work loads up from the minimum load listed. Go up until you either hit the listed max, get the accuracy and or velocity you are after without any high pressure signs. You will find that you won't always get to the maximum listed load without high pressure signs, it does happen. Never start out at or near the maximum listed load! Kinda surprised you have not run into this in 7 years of reloading, I've maxed out with high pressure signs a number of times before hitting the listed max.
Click to expand...

X2 on the above. Some bores are tighter than others, and a host of other variables. Not really unusual to run into pressure signs well before a published max in a particular gun. By the same logic, some guns can safely allow loads over the published max. No way to know which is which except to work up loads, starting low.
 
I use the same powder & 13.1 gr with Speer 110 HP with no problems. OAL 1.642-1.645. I test fire NR re-barrelled carbines and check case length and brass diameter before & after with both factory & my reloads. Case length should be 1.280 - 1.290 before shooting. If you have a vernier, check before and after case length.

Perhaps your chrono is out of calibration? Suggest you shoot some factory loads to compare velocities.

If you have a GEN III Universal (the version with 2 return springs), visually inspect the square slide opening where the right bolt lug fits in for any cracks in the corners of the opening. This is the usually failure point for these parts on a Universal GEN III.
 
Both powders and primers change burn rates from lot to lot. For the most part, unless you're loading for extreme accuracy, there usually isn't enough difference to make any substantial change.

It has been my experience that SMALL cartridges will magnify any slight changes and because of this I am very careful when developing a load for a rifle that is new to me.

2400 is a great powder for the 30 M1 carbine round and it is what I use as well. However, I have never been able to load my cartridges with anywhere near a max load. I don't think I'm alone on this.

The M1 carbine action is a great platform but it isn't as strong as many would like to believe.

Another reason for cratering may be a chamber cut to maximum spec. Headspace can be an issue with this rifle. For an explanation look back to when the rifle was designed. They had feeding issues with it in early military trials because of the slight difference in length of the mass produced cases. When it came to mass production back in the forties, even though it could be very good, one time use items such as cartridges had some pretty wide variations. Not only that but as was often the case certain variances were allowed to be exceeded.

Many surplus M1 carbine chambers were and still are on the large side to make the little rifle reliable under all circumstances. Dirty cartridges/chamber, over max length case, under min length case and even larger gas ports for the piston than was necessary. Their reasoning for this was sound and the little rifles will handle just about everything they are fed without any issues.

Your rifle is a post war clone. It likely has a slightly large chamber as most of the rifles made at that time relied heavily on surplus ammo. I have one of those and I like it. My go to load for my M1 carbines is 12.7gr/2400 under 110 bullets of different designs. Primers don't seem to make much difference. All of my brass it milspec, which has thicker sidewalls, which is also a good reason to use a mid range load.
 
I once found a Start load that blew the primer and we had to use a block of wood to pound the bolt open.

There is a reason the book says Start load. You start there and work up, if pressure is ok. The Max in the book is the max for their rifle, not yours. You have to find the Max for your rifle yourself.

You got away with it. Learn your lesson.
 
Well thanks for the advice guys. I guess with never having issues before i got cocky, i should know better. Ill be pulling the rest of the 45 rounds and starting at 12gn which is listed as the min.
 
bearhunter said:
Both powders and primers change burn rates from lot to lot. For the most part, unless you're loading for extreme accuracy, there usually isn't enough difference to make any substantial change.

It has been my experience that SMALL cartridges will magnify any slight changes and because of this I am very careful when developing a load for a rifle that is new to me.

2400 is a great powder for the 30 M1 carbine round and it is what I use as well. However, I have never been able to load my cartridges with anywhere near a max load. I don't think I'm alone on this.

The M1 carbine action is a great platform but it isn't as strong as many would like to believe.

Another reason for cratering may be a chamber cut to maximum spec. Headspace can be an issue with this rifle. For an explanation look back to when the rifle was designed. They had feeding issues with it in early military trials because of the slight difference in length of the mass produced cases. When it came to mass production back in the forties, even though it could be very good, one time use items such as cartridges had some pretty wide variations. Not only that but as was often the case certain variances were allowed to be exceeded.

Many surplus M1 carbine chambers were and still are on the large side to make the little rifle reliable under all circumstances. Dirty cartridges/chamber, over max length case, under min length case and even larger gas ports for the piston than was necessary. Their reasoning for this was sound and the little rifles will handle just about everything they are fed without any issues.

Your rifle is a post war clone. It likely has a slightly large chamber as most of the rifles made at that time relied heavily on surplus ammo. I have one of those and I like it. My go to load for my M1 carbines is 12.7gr/2400 under 110 bullets of different designs. Primers don't seem to make much difference. All of my brass it milspec, which has thicker sidewalls, which is also a good reason to use a mid range load.
Click to expand...

A very true statement. After reading a lot on the development and problems thereof on the .30 carbine I decided it wasn't a rifle I ever wanted to run "at it's max performance", I would rather have it last my lifetime a whole lot better. I found the lightest, slowest published load I could find for the powders I had available and started a smidge under that...I kept testing/increasing in small increments until I had a load that would work my action/eject "every time" and went with that, for my rifle that was around 1750-1800 fps (I believe U.S. govnt. initial ammo spec for .30 carb. was around 1925). It has served me well and killed a couple of deer with it so no use "stressing" the gas action slide framework at all.
 
tbdtp said:
CCI 400 have a very thin primer cup. I see cratering way before max pressure is reached in most of my sub calibers. If you went up to cci 450 or br the cratered primer will probably be gone.
http://www.jamescalhoon.com/primers_and_pressure.php "list of most common primers thickness"
Click to expand...

well that would explain why i see cratering, but no gas leakage around the primer, or signs of over pressure on the casing itself, maybe i'll try the remington primers i have as well
 
I can't help you much on the subject of reloading, as I don't reload myself, but I'll tell you of an experience I had with a M1 carbine and surplus ammunition. I have an original WW2 Inland. I bought a bunch of surplus .30 Carbine off a friend. The ammunition was made around 1952 in the Dominican Republic. A few of us went to the range and shot a bunch of this ammo (this was the first time I had shot this rifle) It shot fine and we had burned thru around 60 rounds when all of a sudden, as my friend's son was shooting, the gun stopped shooting. Upon examination, we discovered that the bolt had went to pieces. One of the guys in the group was a reloader and he checked the spent cases. he said the cases and primers showed signs of excess pressure. I eventually got another bolt and the friend that I had bought the ammo from offered to take the ammo I had left (around 500 rounds) and pull the bullets in order to check the powder charge. He did so and came to find that the powder load was very inconsistent, with some being overloaded and some being under loaded. He wasn't sure of the powder type, so he averaged the powder that came from the rounds and reloaded all the same. I've shot some of it since he did that and it shoots fine and cycles the action just fine. The cases also look fine now. I guess my point is to watch your spent cases for signs of overpressure. The bolts in these rifles are not too forgiving of overpressure, cheers.
 
You must log in or register to reply here.
Back
Top Bottom