7.62x54r brass stretching

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All handloading data posted on Full-Bore UK from 23/2/2021 must reference the published pressure tested data it was sourced from, posts without such verification will be removed.
Any existing data without such a reference should be treated as suspect and not used.

Use reloading information posted here at your own risk. This forum (http://www.full-bore.co.uk) is not responsible for any property damage or personal injury as a consequence of using reloading data posted here, the information is individual members findings and observations only. Always verify the load data and be absolutely sure your firearm can handle the load, especially older ones. If in doubt start low and work your way up.
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Asgard
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7.62x54r brass stretching

#1 Post by Asgard »

Hello all, I have been developing some low loads for my old Mosin and I discovered the brass loaded with 165grn lead poly coated and 23 grn of 2400 stretches much more than 44grn rx15 and 182grn jacketed ammo which did not need any trimming after firing.
I wonder why?
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Re: 7.62x54r brass stretching

#2 Post by dromia »

What is the bullet retention on the cast and jacketed, what BHN is the lead?

Peak pressure also happens sooner with 2400 than Reloader 15 so less time for the bullet to "Let go" of the case also usually cast are of a greater diameter than condom bullets so if the neck expansion is the same for both more grip. Combine that with a hard commercial bullet and that would stretch the case.
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Re: 7.62x54r brass stretching

#3 Post by Asgard »

Hi and thanks for the reply. I am not sure of bhn, the bullets are from hf ammunition. Measured on micrometer both fmj and lead poly are .311. I had factory crimp on fmj and no crimp on the lead ones - they were seated to cannelure. Was it possible due to too much pressure from the 2400?
I have also noticed significant drift to the right
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Re: 7.62x54r brass stretching

#4 Post by dromia »

23 gns does seem a tad hefty to me what data source does it come from?

When you say poly coated what exactly do you mean by that?

Pressure within the limits of the cartridge in and of itself should not cause excessive case stretching, but when the pressure peaks in time can.

If you don't trim will the the round chamber?

If so does the case stretch again on subsequent loads the same?

Crimp dies are the work of the devil along with expander balls and should be destroyed as soon as they are made.

You didn't answer my question about neck tension.

What neck expander are you using?

If the neck is not expanded the correct amount for cast, 1-2 thou over bullet diameter then the case will grip a cast bullet more than a condom bullet which is strong enough to expand the case 'pon seating.

Cast bullets do not follow exactly the same processes as condoms for success. They need a different mindset.
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Re: 7.62x54r brass stretching

#5 Post by snayperskaya »

What variant of Mosin do you have?, also what length are you trimming to?.It is often worth slugging a Mosin barrel to see what the actual diameter is as they can vary quite a bit, as can the throats.As an example I have a very accurate 200gr cast load with a COAL of 3.00", this will chamber in my New England Westinghouse M91 but not in my 1917 Remington M91 but if I seat back to a COAL of 2.96" it will chamber in the Remington no problem and both the Remington and the N.E.W chamber FMJ rounds with a 3.03" COAL.

Does your drift to the right occur with all ammunition?, reason I ask is most people don't realise that Russian/Soviet Mosins were originally zero'd with the bayonet attached, as per Russian/Soviet doctrine, and when shot without the bayonet there is a shift in POI.They also tend to shoot high at 100m with the rear sight on the lowest setting, this is due to the way they were originally zero'd,

Below is a description of the Russian zero procedure for the M91/30 that may be of interest.......

On entering service with a unit, each rifle was tested for zero. The rifle was usually fired in the presence of—but not by—the soldier it was issued to. Its accuracy and zero were checked by the unit’s best shooters, who fired them prone off a rest at 100 meters, with their left hands supporting the rifles on the rests and the rear sights set at “3” (300 meters). The rifle’s aiming point was the bottom edge of a black rectangle 30 centimeters tall and 20 centimeters wide (roughly 12 by 8 inches). In keeping with their training to aim at a belt buckle, the required mean point of impact was 17 centimeters (6.69 inches) above the point of aim, at that sight setting. Four shots were fired, and the rifle’s zero was considered “confirmed” or acceptable if all four fell inside a 15-centimeter (5.90-inch) circle, with the average center not diverging from the aiming point more than 5 centimeters (1.96 inches). In the case of a noticeable flier, allowances were made to pass with three shots. Adjustments on the rifles were made by unit-level armorers on the spot if the rifle didn’t print correctly, and records were kept on each gun.



With my 54r brass some cases will expand more than others even with the same bullet weight/powder charge.
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Re: 7.62x54r brass stretching

#6 Post by Asgard »

Dromia, to answer the questions: Source is Lyman cast bullet handbook 3rd edition. By Poly coated i meant polymer coated lead bullets. Yes it will chamber without trimming. the chamber is vy looong. I haven't tried a subsequent load, that was the first time I fired a low load cast bullet in a rifle. As retention on the bullet, both batches of ammo were full resized , the 182gr fmj was factory crimped for consistency, I did not crimp the lead bullet just seated to the crimping cannelure. I did not use a neck expander as I do not possess one for 7.62x54R but I was thinking that the expansion for the lead head may need to be bigger than for fmj. As I said this time was the first for me with cast bullets, I am trying to develop a lower load to protect the rifle and to ease it on the shoulder for me and my young son who enjoys shooting too.
Snayperscaya: My Mosin is a 91/30 from 1927 Izhevsk made. I am trimming to 2.1in. My bore slugged to .310. Is the cartridge measured to ogive 3 in? I am shooting the Mosin with the bayonet on and it groups quite well probably around 20cm diam circle with fmj load set about 40 thou of the rifling. The drift to the right was noticed only with the lead cast cartridges. It varied quite a lot from 4in to 1 foot. Vy Vy strange. I have some 200grn heads and I will try and see how they behave. Interesting zeroing procedure and tnx for posting. When I was much younger and we used to go to the range with our unit we had a humanoid paper target we used to call the cow. For 100m we were always told to aim the AK at the base of the cow to hit the middle. Who had a 5 hits row would win a permission to go home for the weekend:D
Tnx both for answering. It's all a learning curve.
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Re: 7.62x54r brass stretching

#7 Post by Alpha1 »

Please don't call bullets heads its the wrong terminology. They are cast bullets or jacketed bullets. The head is the base of the case. I would suggest you invest in an expander if you are going to carry on with cast bullets. Seating a bullet without the case kneck being expanded to the correct diameter can lead to shaving of the cast bullet so when it chambers it is undersized for the bore.
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Re: 7.62x54r brass stretching

#8 Post by andrew375 »

I shoot cast extensively in both my mosins and don't see any abnormal case stretching. In my experience most case stretching is a result of the neck expander button in the resizing die that pulls the neck and shoulder forward. Try polishing the button down a few thou' .

I use a Lee collet die , for 7.5 Swiss as they don't make one for the Russian, then a separate neck expand and flaring die.
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Re: 7.62x54r brass stretching

#9 Post by dromia »

Coated bullets are prone to case sticking, best to use proper cast bullets without unnecessary "coatings". I suspect this along with neck expansion and perhaps too stiff a load but changing to a properly "lubed" and sized bullet will solve the problem, do that first and see if that helps.

This coating thing is just a fad and really doesn't do anything positive for rifle bullets, there are some people getting good results at high velocity with coated cast but it is a very involved process and bit like HV cast in 6.5 Swede. It has its place I think for people doing high volume pistol bullets.

Cast bullets need to be 1-2 though over groove diameter so should have a greater diameter than condoms, ideally the should be sized to fit the freebore if they will chamber at that diameter, but using groove diameter is a sound starting point, the lead must be soft not hard as you get with commercial bullets which are made hard for the benefit if the manufacturer not the shooter, hard alloys work easier in casting machines and are more robust for packaging.

Are these commercial bullets or home made? If home made then what alloy are you using?

Doesn't sound like much of a reduced load to me, the Lyman book isn't very good for reduced loads as they try to get condom velocities from cast for their publication.

I suggest you read Harris's seminal work Cast Bullets for Military rifles a copy of which resides in the library here and bin the coated bullets.

Once you have determined the specs of your rifle you can then choose a mould that will give you a fitting bullet then you will need a two step neck expanding "M" type die for your cases.

As has been said expander buttons cause case stretching and should be destroyed but if that was the cause then the same would be happening with your condom loads.

I suggest that you search these forums as this subject has been done to death and there is much good stuff herein on the subject.

There are no such things as bullet heads, a meaningless term adopted by a retailer whose customers was getting confused 'tween bullets and cartridges and unfortunately has stuck, the head is the base of the case, the bullet is the bullet!
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Re: 7.62x54r brass stretching

#10 Post by Asgard »

Thank you for all info. I'll keep this updated with some values. The bullets are from hf ammunition, commercial made.
Talk soon
In my language we use the colloquial term bullet for the whold cartridge and for the projectile however there is no confusion about this here.
The lion cannot protect himself from traps, and the fox cannot defend himself from wolves. One must therefore be a fox to recognize traps, and a lion to frighten wolves.
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