What a differnce a crimp makes

[Smith357]

I was out this morning testing out a few reduced loads in my .30-06. These two loads pictured are the same exact loads prepared the same way except one was lightly crimped and one is just tension fit. The load is 6 grains of BE under a .309 180 grain cast bullet from straight wheel weights, Lee DC C309-200-R, un checked, with 2 applications of liquid Alox painted in the groves, and a CCI BR primer. Brass was neck sized only. Range 50 yards, wind from right to left less than 5mph.
The rounds were loaded one at a time into a bone stock 1974 Winchester M70 with Leupold 3x9 VxII and fired from a concrete bench with a 9" Harris bipod used as a front rest.

The crimped group

The uncrimped group

 

[Nevada Ed]

Now that's what I am talking about !!
Very nice...............you never know what is going to happen
with a new test load. Sure is sweet when you come up with groups like that last one.

I get good groups with the 100gr Hornady "Plinker" with my
1903 custom 30-06 with 20grs of SR 4759 but kept it at only
50 yards due to the low velocity with no crimps.

Even better since those bullets are your own, home made "Recycled" brew.

 

[rwsmith]

Aw man, I just let myself......

Aw man, I just let myself be talked out of crimping 30-06. Decisions, decisions.

 

[Smith357]

Aw man, I just let myself be talked out of crimping 30-06. Decisions, decisions.

Non-crimped is what works in my rifle, you may yield very different results. All I can say is make up 5 or 10 of each and see how it behaves for yourself then pick the best performer.

 

[moxie]

Non-crimped usually works better.

Remember that the main reason for crimping, in heavy revolver loads, is to prevent "bullet jump." In full auto rifles this can occur too, so crimping is a good idea for 30-06 fired out of, say, a BAR. Out of a bolt rifle, nah. Good case neck tension is all you need. Why mess up brass and possibly the bullet itself by crimping if you don't need to?

 

[Smith357]

Non-crimped usually works better.

Remember that the main reason for crimping, in heavy revolver loads, is to prevent "bullet jump." In full auto rifles this can occur too, so crimping is a good idea for 30-06 fired out of, say, a BAR. Out of a bolt rifle, nah. Good case neck tension is all you need. Why mess up brass and possibly the bullet itself by crimping if you don't need to?

The thought behind the crimp was with such a light load retaining the bullet in the case for a fraction of a second might equalize the pressures. But it seems all it did was deform the bullet as in these low pressure rounds the crimp is still visible on the fired cases.

 

[2152hq]

.... But it seems all it did was deform the bullet as in these low pressure rounds the crimp is still visible on the fired cases.

I found that too w/ cast bullet loads in 30-06 and 30-40Krag.

When I loaded the same two using the exact same load (12.5gr Red Dot) but w/ pulled GI FMJ bullets & I crimped the loads,,the FMJ bullet ironed out the crimp on it's way out of the case in both calibers.

The groups were still better using the FMJ bullets w/o crimping though.
They didn't beat the cast bullet groups however.

I can load the cast bullet down to 9gr RD and still shoot & group them OK.
9gr RD under the FMJ's will land them in the grass 3/4 way to the target w/ the same sight setting. Bore friction?

You never know how it's going to go. No set rules,,just some guide lines. But range testing tells all.

Very nice group w/the M70.
I may need to get one of those telescope things.

 

[SMSgt]

I have never crimped a shouldered rifle round and see no need to start. Someone somewhere thought it was a good reason because the military does it. Well, if you're reloading for a machine gun, maybe.

 

[Nevada Ed]

In all my years of reloading for my bolt action 22-250, 270 & 30-06 rifles, there was only ONE bullet that needed a crimp to work to its best performance.
It was the Remington 150gr PSP flat base Core-Lokt, set at 3.19" oal and a medium crimp with imr 4350 powder at 2900fps +/-.

 

[Mikie]

Yes, but why?

Is there any explanation why this is true?

 

[forestswin]

I really like pictures - they really make the point more than can be explained with words - and the lesson is much easier to remember

not much else needs to be said

except maybe - you did miss the target

 

[Smith357]

I really like pictures - they really make the point more than can be explained with words - and the lesson is much easier to remember

not much else needs to be said

except maybe - you did miss the target

Yes, Yes I did.

The scope is currently sighted in for my full power MOA loads of 49.6 grains of 4895 under a 168 grain V-Max and zeroed at 200 yards for the cold barrel shot, the irons are set for 100 yards. Come to think of it I have not changed the zero on the rifle in many years. I will take it out a couple times a year and it just shoots into the bull as long as the light barrel stays cool. It will start stringing vertically when it warms up, about 3 rapid shots. The old hunting scope does not have target turrets or an easy way to mark positions so I figure for these plinking loads I'll just use a little Kentucky windage.