Crimp or no crimp for semi automatic rifless

[merbeau]

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

 

[g0rd0]

I would get a collet style crimp die and crimp, this style of die works on all style of bullets with or without a crimp grove.
A few years back I had a Rem 742 in 3006 and I had to crimp or the bullets in the mag would get pushed back into the case on recoil.
I have the lee crimp dies in 3030, 308, 3006 and 7rm but only use them in auto loaders and tube style mags

 

[merbeau]

Thanks for the reply. That is one of the reasons that I have not purchased my reloading dies yet. The collet style makes sense - I kind of suspected that the recoil and then the bolt slamming behind the round could make the bullet seat deeper.

 

[NoFences]

I have the same rifle and caliber. You'll want to get a small base sizing die for reliable feeding.

 

[g0rd0]

Thanks for the reply. That is one of the reasons that I have not purchased my reloading dies yet. The collet style makes sense - I kind of suspected that the recoil and then the bolt slamming behind the round could make the bullet seat deeper.

the bolt is not what slams the rnd.
What slams the rnd is the forward part of the mag (from the recoil). You can slow this down by loading the mag with the bullet tips touching the forward end of the mag. But, they may not cycle right in that position.
Now that I have said that load up with factory rnds , bullets to the rear of the mag, fire 1 remove mag and check you rnds for tip damage.
True story, my first deer rifle a rem 742 / 3006. Used for 10 years before I reloaded. When I loaded my first batch (FL size, and using the rcbs dies turned down the seat die to give a crimp). First round bang, action cycled 2nd round bang, action cycled 3rd rnd bang action did not cycle right (the gun did not fire, look cant and see the cocking handle not in the right place). So, I eject, brass and powder went flying leaving the bullet in the chamber.
Took off the mag and the 1 rnd left in it had the bullet almost shoved into the case. I then dropped my cleaning rod down the bore and knocked out the bullet.
A smith told me that it is common for that to happen without a strong crimp and to load the mag with the ammo fully forward in the mag or get a collet style crimp.
What happened was 1rst shot mag pounded the 3 in it, 2nd rnd pounded the next 2 rnds loosening the bullets the shot pushed and loosened rnd 3 so much that when it chambered the bullet was tossed out of the brass jamming the action and the bullet was tossed into the rifling. The nose on that bullet and the 1 left in the mag had the point hammered almost flat.
Ever since I started crimping for the 742 no issues (that is after I found powder bullet combo for it).
But you need to know that with an auto loader you may notice that reloads will not work right until you get to max loads.
I sudgest that you single load it until you know that you can get as close to max load without to much preasure signs, stay with posted OAL (don't play with that), You may have quite a job finding a powder that will cycle your action reliably.
For my 742 only IMR4064 and RL22 will do it and only with 180grn pills

 

[StrutNut]

I tried so many different dies that where supposed to work with that rifle I finally gave up and just shoot factory rounds in it. It groups great with Winchester Silvertips. Mine is an old Grade II Belgium.

 

[merbeau]

Ok, understand the magazine issue. Geez, what an experience. When I reload for my bolt actions, I will take a FL unprimed case and cut a slit in the neck and place a bullet into the neck and insert into chamber closing the bolt slowly. Then backing out slowly which if done several times will provide point of 'touching the lands.' I usually back off 0.005 to start my testing at. I have not had a round that exceed the published OAL and only once a round would not fit into a magazine using that technique which was with a 375 Ruger.

I want to do the same thing with the Browning closing the bolt by hand after inserting a blank round with the aforementioned procedure. Are you saying not to do this?

 

[merbeau]

I have the same rifle and caliber. You'll want to get a small base sizing die for reliable feeding.

thanks for the advice. just looked on Midway and RCBS does make that style for the 7mm Rem. Mag.

 

[RT2506]

Get a Lee Factory Crimp Die and leave your cases 5 thousands inch longer than the trim to length. This will give you enough case to get a good crimp on. You do not need a bullet with a crimp groove because this die will make it's own. From my own experience this does not destroy the accuracy of the bullet, even match bullets. One other advantage of this crimp I have found is that you don't have to go through that find the lands and "proper" seating depth process. The crimp holds the bullet in the case long enough to allow the pressure to build up for a good consistent burn and I have gotten great accuracy without all the "proper" seating depth process. I found this accuracy advantage while fooling with the old military rifles that have a throat a mile long and you can not even get close to the lands and the round work through the magazine. Like has been said with the BAR use a small base FL sizing die. Also realize that the BAR is a hunting rifle not a target rifle and that minute of shoulder angel accuracy on game is still dead game. Have fun.

 

[merbeau]

Thanks for the tips. This is definitely new territory for me. I have a box of Nosler 140 grain Trophy Grade ammunition which the has a crimp groove in the Accubond bullet and you can see the crimp. For all my rifles I shoot factory as a base for comparison. These have have functioned without incident through the rifle. I will try to reproduce their dimensions.

 

[bigedp51]

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

You have two choices
1. Increase your neck tension by making the expander button smaller or using a smaller neck bushing etc.

2. Lightly crimp the case mouth, the RCBS AR series dies I have use a taper crimp which I prefer.

We live in a plus and minus manufacturing world and no two dies and chambers are the same. Meaning neck tension can vary by the type/brand of dies and the neck thickness of your cases. (brass springback)

On my AR15 rifles and my M1 Garand I have never had a problem by "NOT" crimping "BUT" my expander buttons are polished .001 smaller. But on the ammo I load for my two sons AR15s I use a type "M" die expander and a light taper crimp.

Bottom line, make test rounds and see if you can push the bullet into the case by placing the bullet against your loading bench and pushing on the base of the case.

The simplest thing to do is buy bullets with a cannelure and apply a light crimp if you can't measure your neck thickness and expander button diameter.

 

[RevJim]

I have an older Belgium made BAR in .270 Winchester. I use the RCBS Small Base FL dies, Lee Factory Crimp Die and I load them to just work through the magazine properly. This rifle has a long throat and touching the lands is too long for the magazine anyhow. The same will work for your 7 mag. Depending upon your chamber dimensions and number of reloads you want out of your cases, you may want to invest in a collet die that sizes down the bulge in front of the belt. BTW, I crimp my cases pretty hard, never had an issue. Good luck to you.

 

[Bart B]

For what it's worth, people winning the big matches and setting records in NRA and CMP matches shooting AR platforms using the .223/5.56 round never ever crimped case mouths onto their bullets. And their rounds single loaded often have so little neck grip on the bullets, one can easily pull out a bullet with their fingers.; proving a tight grip by the case mouth on the bullet is not needed. If you've got the stuff to measure the force needed to pull a bullet out of a case, you will learn crimped in bullets have a greater spread of that force; therefore, so will velocity and pressure have greater spreads.

Sierra Bullets proved crimping reduced accuracy back in the '50's along with benchrest folks; both shooting bullets the most accurate. I think Sierra was one of the two bullet companies who got on Richard Lee about his factory crimp die causing their bullets to shoot less accurate. Lee finally agreed to put words in print saying not to crimp those makes of bullets.

Being the first person on earth to shoot an M16 across the standard course of fire in the 1971 DCM Excellence in Competition match at the Nationals, I can attest to the conversations several of us on the military teams shooting them. We all knew that many folks would want to crimp case mouths on ammo for it, but we all knew better. None of our ammo had crimped in bullets.

Arsenals used to crimp all .30-06 match ammo. I think it was Col,'s Hatcher or Townsend that convinced them to quit crimping ammo and no longer put the cannelure in that original machine gun round's 173-gr. FMJBT bullet. When they finally did that, the largest test groups got smaller. No more 30 caliber match ammo hand crimped in bullets.

Sierra Bullets caved into customer demand for their 22 caliber 77-gr. HPMK bullet to have a cannelure in it for crimping for use in AR platforms. They repeated their early '50's tests with different amounts of crimps on them as well as no crimps at all. They never crimped another test round testing that bullet for accuracy standards. Good lots of them would shoot 1/4 MOA in their 200 yard test range. Best accuracy with any crimp put 'em into 2/3 MOA at best.

Therefore, I suggest people do what they want to. Follow the trail match winners and record setters blazed with no crimped in bullets or hack your way through the woods and end up some place else.

Judge accuracy by the largest groups shot with any process of bullet seating; they happen when all the variables add up in different directions. The smallest groups are mostly luck as all the variables tend to cancel each other out. Both happen at the same low percentage rate across all groups fired anyway. They all are somewhere between some unit of measurement and zero.

Shoot at least 20 or more shots per test group to get statistically significant results. If you use the smallest single few-shot group to asses accuracy, any combination of tools and their use, components and their assembly, any given method may well be the one you prefer.

Finally, if you're not shooting your stuff into sub 1/2 MOA accuracy at worst, you may not see how much accuracy loss is caused by crimping case mouths into bullets. Even the slightest amount of crimp is enough to deform bullet jackets enough to cause imbalance at 150,000 rpm or more that makes them jump further than normal off the bore axis upon exit from the barrel.

 

[bigedp51]

Sierra Bullets caved into customer demand for their 22 caliber 77-gr. HPMK bullet to have a cannelure in it for crimping for use in AR platforms. They repeated their early '50's tests with different amounts of crimps on them as well as no crimps at all. They never crimped another test round testing that bullet for accuracy standards. Good lots of them would shoot 1/4 MOA in their 200 yard test range. Best accuracy with any crimp put 'em into 2/3 MOA at best.

Bart B

The 22 caliber 77-gr. HPMK has a cannelure because the military requested it for their 5.56 mm, Special Ball, Long Range, Mk 262 Mod 0/1 ammunition.

My blasting, end of the world, SHTF, Zombie apocalypse ammunition is "LIGHTLY" crimped and my match grade ammo is not crimped. If a reloader does not understand neck tension or bullet grip then crimping is not the end of the world as you stated above. 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.

There is a reason "WHY" the military requested a cannelure on their bullets.

And there is a reason "WHY" RCBS has a taper crimp on their AR series dies.

So all of you readers just remember this, the red tipped V-Max bullet on the left is fired in my bolt action .223 Savage and is not crimped. And the green tip Z-Max on the right is crimped for my AR15 rifles just like the military does.

So again, there is nothing worse than a jammed AR15 rifle in a Zombie attack where only close range head shots count.

And if you decide not to crimp then your going to have to make friends with the Zombies and do your postings at Benchrest Central.

P.S. I crimp my 30-30 ammo also, and range estimation isn't critical and crimping the bullets doesn't matter as long as you put the corn piles less than five feet apart.

So who does this Bart Buttzinsky think he is, and why is he crimping our style?

The following message was brought to you by "The Society for the Prevention of Bart B Pulling the Handle of my Reloading Press Association".

Signed
Attila the Hun