Crimp or no crimp for semi automatic rifless

[Bart B]

Bart B,

So don't tell me a "uncrimped" full length resized cartridge has never had a bullet move forward from inertia when chambered in a semiautomatic rifle. All it would take is one neck on the thin side and then have a bullet "jammed" into the rifling and raise chamber pressures to dangerous levels.

It never happened with M72 .30-06 match ammo since crimping and canneluring bullets was stopped nor with M118 or M852 7.62 match ammo in Garands and M14/M1A semiautos as well as commercial semiautos chambered for either round. Their bullets are 2 to 4 times heavier than those in 22 caliber .223 Rem and 5.56 NATO semiautos yet have the same release force specs.

Pressure test data I've seen for bullets jammed into the rifling produce less pressure than proof loads for both the 22 and 30 caliber rounds mentioned above. Proof loads are not dangerous, just the absolute maximum for safety. I've shot hundreds, if not thousands, of them in Garands. Commercial and military rifles are tested with them.

So, Big Ed, your tirade was misdirected, not applicable to my remarks, but otherwise quite entertaining. I was referring to best accuracy demands. Combat accuracy can be less accurate and has to be more reliable; I agree that crimped in bullets are important. So are the 500 grain or heavier ones in 45 plus caliber hunting rifles as their recoil alone is enough to set bullets forward in the case if they're not crimped. If one cannot manage the quality of their cases to prevent less than needed release force on their bullets, that's a case quality ane reloader attention to details problem, not a bullet problem. Besides, the contamination of the atmosphere by Zombie odors requires bullets and primers be sealed like arsenal ammo is. Otherwise, the powder and primer pellet will be rendered inert by contaminants emitted by Zombies.

Sierra's reason for cannelures on that bullet was conveyed to me by them some time ago. And they told me it was civilian handloaders shooting that 77-grain pill in matches that asked for it. Do you have a link to a MIL SPEC stating the military originally wanted it? If so, that's fine by me. But they don't test them in crimped cases because they don't shoot as accurate.

Accuracy alone was the sole basis for my comments. If you want to redirect it to combat use, that's another bag of worms.

 

[waltercrouse]

Hi

I just purchased my first semi automatic rifle, a Browning BAR in 7mm magnum caliber. All my other rifles are bolt action.

I reload for all my bolt actions and have never used a crimp on my reloads.

Since for a semi automatic there is no control over cycling unless you only shoot one round the questions is to crimp on not to crimp and if so, what type of crimp taper, etc.

I am planning on using Nosler brass with 140 grain Berger VLD bullet which does not have a crimp groove.

Thanks

Robert

I suggest to crimp a bullet with a grove in it. I had some .357 smooth bullets without a grove and they moving out of the brass. They were crimped.

 

[alaska]

For my BAR I always use a RCBS Small Base Sizer Die and a Lee Factory Crimp Die with light crimp.

In the BAR .........7mm RM , 338 WM, 30-06 and 270 win and 300 Win.......seems
IMR 4350 performed best with the BAR piston system in all these Cal.

Suggest also to know how to clean the piston .......yearly.

The Speer 160gr Grand Slam or the tougher 160gr Swift A Frame are 2 excellent bullets in the 7mm RM with IMR 4350.

Really like the older Beligum made BAR's ........

 

[merbeau]

Alaska

Thanks for the information. I have some IMR 4350 as well as Retumbo, H1000, IMR 7828, IMR 4451 and Hodgdon Hybrid 100V. I looked at the owners manual and the gas system will have to be studied. This BAR is a FN Belgium made Grade II with a really nice bore. I purchased it because it did not seem to have been shot a lot and was in great shape and I was looking for a semi automatic.

 

[alaska]

Do not load real slow burning powders in your BAR
You can not load it like a bolt action

Like I said it was designed around IMR 4350
Too much pressure can damage the rifle.......very slow burning powders.

You might could use IMR 4451........but I don't think it approve much over well established IMR 4350.

I more concerned about not damaging your rifle rather than a extra 100 FPS

You have a nice rifle.........

Very simple gas system

Take the forearm off

Take the sliding support rails out

Take the rails off both sides

Take the spring out from the back be careful with small plastic that attaches to rear of the recoil spring do not break it

Now to front where the piston is ........the lug up front a wrench or adj will do take it off be careful not to mar it

Your piston may need to be bumped from the rear if it has not been cleaned......it should come out the front

Clean your piston area with good solvent......with 20ga shotgun bore brush........put everything back together in reverse order

Make sure your piston area is free of oil......residue.

The Berger VLD are a long bullet......very explosive........if deer are on you menu suggest the excellent 140 or 150gr Nosler Accubond and IMR 4350.
Any question shoot me a email I have 40 years with the BAR........

 

[merbeau]

Thanks for keeping me on the correct 'BAR' track. I will have to keep myself from thinking bolt for awhile. Will start out with IMR 4350 and 4451 And thanks for the cleaning tip. Great guys on a great forum.

Robert

 

[alaska]

Robert

Be very careful with 4451 if it's a double base powder like Reloader 17 is your port pressure might be high......start very low.

Like you know it's a high performance powder...........

 

[merbeau]

Probably will start with IMR 4350 and see if the rifle likes it. Will move to 4451 if initial results are not promising.

thanks

Robert

 

[Lefty7mmstw]

You need enough neck tension to keep the pill from moving under recoil, no more. I've fired out 30 round mags in my ar with 5.56's loaded with 75 grain priv partisan pills with 4895 under them at 2800 fps with zero bullet creep. I do NOT ever crimp a round, unless my big rifles are being loaded. I crimp for my 375h@h, my 405 win, and my 44mag pistol.

If you have issues with bullet creep, change your neck tension or toss a mild crimp on, but expect a loss of accuracy with the crimp. I wouldn't do it. As to bullet noses being damaged, use a bullet with a protected nose. Plenty of those designs are available.

Listen to Bart on this one...

 

[merbeau]

Update

First of all thank you to all that replied to my initial inquiry. Many good suggestions.

I finally was able to start some testing after having to overcome issues with my brass and RCBS X die system, selecting the Nosler 150 grain long range bullet and then purchasing a Lee Factory Crimp die, and a shell holder for my LE Wilson trimmer.

I went with IMR 4350, IMR 4451, Hodgdon 100V, Vihtavouri N160 and Alliant RL 17 which are similar to IMR 4350. Of all these N160 is the slowest.

The bullets were seated just deep enough to operate in the magazine and the crimp was set between light and medium setting as described from Lee.

The best combination was from RL 17 with a fairly good group at 57.0 grains and then the group shrunk down to about 0.5 inches at 58.0 grains. All these were shot off my bench rest system. (See Figs 1, 2 and 3).

The recoil did not seem excessive and I really could not ask for more from a hunting rifle. The only possible problem is that RL 17 may be temperature sensitive.

Again, thanks to all that replied.

Robert