Large or small rifle primers. Is one better?

[Jeff R]

Hi,
My pal in Michigan just won a 6.5 Creedmore rifle at a UP Whitetails banquet. He is shopping for components, and has found 6.5 Creedmore brass available with large or small primer pockets. He asked me which one he should order. I don’t know. Are there any new trends in the shooting world favoring one over the other?
Thanks,
Jeff

[cabezaverde]

The one he has primers for!

[BrassMagnet]

The one he has primers for!

AND the one he will have primers for!

[cwtebay]

Lapua brought the SRP to the CM because of more consistent ignition times within the powder column as well as leaving more brass intact at the case head. Unless your pal is stretching the legs on that rifle, and it's a precision type build - he's unlikely to see much difference. LRP does seem to be a more reliable ignition during UBER cold weather if that's an area of concern.

Sent from my Pixel 5 using Tapatalk

[Der Gebirgsjager]

My opinion and just discussion-- I don't believe that for practical purposes there's much difference. Like a lot of us here, the first time I ran across large vs. small primers was with .45 ACP. Both work very reliably, and the main annoyance is just in getting the brass mixed together when loading. Considering the mixed availability of primers now days and what they cost it would be a good idea to have some of both types.

DG

[35 Rem]

This not something new but rather from the 1980's but Jim Carmichael in writing about the 22 CHeetah wildcat cartridge said that he did a lot of testing to compare LRP's to SRP's in the same case. The SRP's gave a small but very measurable improvement in accuracy. I had a rifle chambered for the CHeetah based on his writings. He recommended the now obsolete Remington Basic brass which was 308 dimensioned with a small primer pocket. It was very uniform brass with thinner walls so it would hold more powder. To test the primer size theory I made up some 22 CHeetah brass using 243 Winchester as the donor brass so I would have large primer pocket brass for comparison. All brass was processed the same. Primer pockets uniformed, flash hole deburred, necks turned and reamed. trimmed to same length and deburred. The small primer brass consistently grouped smaller on paper. Loads using the small primer brass would typically be in the 3/8" range for 5 shots at 100yds. Same load but with the large primer would be around 1/2" 5 shots at 100yds. Not a huge difference but if you are trying to shoot crows or groundhog heads poking up from behind a soybean way out across the field any accuracy improvement is meaningful.

But now here is the negative - and Jim Carmichael mentioned it in his article. Cold temperatures can cause hangfires. And they did. Let the temperature get down to even 55 and I would start to notice a "click - boom" delay. According to Mr. Carmichael the Remington #7 1/2 Benchrest was the hottest SRP available so that's what I've always used. Yet it is still plagued with this temperature problem. Typical loads for the CHeatah are about 40 grains of powder which is about what the Creedmoore is going to use so I would expect the same results. If I were going to deer hunt with it, I would be very hesitant to use the SRP brass. If you only want to shoot the smallest groups in fair weather then small may very well be best.

OH yeah, supposedly the reason behind the SRP's accuracy advantage is that it ignites a smaller % of the total volume of the powder charge so that any variation from primer to primer will have less impact on the velocity variation. I never tried long strings of chronograph test to prove or disprove that.

[Jeff R]

Thank you all. I will send him a link to this thread.
Jeff

[Half Dog]

I opted for the large rifle primers simply because I have/had other calibers that used them.

[rockrat]

Probably better ignition if using it for hunting in colder weather, when using large rifle primers

[Shawlerbrook]

Small rifle primers seem to be more available probably because of increased production due to military use.

[AnthonyB]

I use both in 6.5 CM. The Lapua SR brass is for the Ruger Precision Rifle and paper targets; the LR is used in the SCAR for the ignition reasons mentioned.
Tony

[MT Gianni]

Be versatile and get some of each. Never shoot them together but have enough to work up and shoot either if primers are difficult to find.

[gwpercle]

Be versatile and get some of each. Never shoot them together but have enough to work up and shoot either if primers are difficult to find.

:goodpost:
LIKE LIKE LIKE

This is the best answer ... you never know what you will find , so cover both bases .
Gary

[Texas by God]

Exactly. Get both types.
I shoot the not so common 6.8 SPC cartridge and I’m glad to have either type.
My jacketed loads use Remington LRP brass,
My cast loads use the SRP brass from other companies(Hornady, S&B, SSA).


Sent from my iPhone using Tapatalk

[Kestrel4k]

That is a very interesting post, 35 Rem; thx.

[ebb]

Many BR shooters say that a small rifle primer is problematic with cases loaded with over 40 grains of powder. I have no idea but if I wanted to use the SRP brass I would use SRP magnums if approaching 40 grains or low temps are in the mix. Nowadays the SRP brass is known to take more pressure than the LRP due to more metal left in the base of the cartridge, just like CWTE bay said. I think that most all of the guys using SRP today only want the added pressure and want to hot rod the cases. Palma shooters discovered this many years ago.

[shaggybull]

If you get both types then you would have option to shoot which ever primers were available. I haven't seen small rifle primers on shelf in a couple years, large rifle have been more available here.

[white eagle]

my chronograph says I get higher velocities out of SRP than LRP
but that is just my set up

[Rapier]

Most common, therefore lest expensive is SRP.

[farmbif]

I went with srp because that what starline had when I went shopping for brass. cci 41's and Remington 7 1/2's work well for what ive shot